Scientific Report 2001 Volume V General Energy
PAUL SCHERRER INSTITUT ISSN 1423-7342 March 2002
Scientific Report 2001 Volume V General Energy
edited by Prof. Alexander Wokaun and Christina Daum
CH-5232 Villigen PSI Switzerland Phone: 056/310 21 11 Telefax: 056/310 21 99
A digital version of this report is available on the home page of the General Energy Research Department http://ene.web.psi.ch TABLE OF CONTENTS
INTRODUCTION A. Wokaun
ENERGY AND MATERIALS CYCLES 3 S. Stucki
PARTIAL OXIDATION OF METHANOL ON A COPPER CATALYST 5 F. Vogel
LOW TEMPERATURE CATALYTIC PARTIAL OXIDATION (POX) OF HYDROCARBONS (d TO C10) 7 FOR HYDROGEN PRODUCTION E. Newson, T.B. Truong, A. Fleury
A NEW REACTOR CONCEPT FOR IMPROVED HEAT INTEGRATION IN AUTOTHERMAL 9 METHANOL REFORMING K. Geissler, T. Schildhauer
ON-BOARD FUEL CONVERSION: DIMETHYL ETHER FROM METHANOL FOR COMPRESSION 11 IGNITION ENGINES H. Armbruster, S. Stucki
THE REDOX PROCESS FOR PRODUCING HYDROGEN FROM WOODY BIOMASS 13 R. Sime, J. Kuehni, L. D'Souza, E. Elizondo, S. Biollaz, S. Stucki
METHANE FROM BIOMASS 15 S. Biollaz, S. Stucki
HEAVY METAL EVAPORATION FROM FLY ASH IN INERT AND OXIDIZING ATMOSPHERES 17 H. Lutz, Chr. Ludwig
STRUCTURE OF ZINC PARTICLES FORMED BY CONDENSATION FOR TRANSPORTATION 19 TO AN ANALYTIC DEVICE T. Barone, J. Wochele, Chr. Ludwig, A.J. Schuler, B. Ketterer
HEAVY METAL RECOVERY FROM FLY ASH: A Zn K-EDGE EXAFS STUDY 21 R.P.W.J. Struis, Chr. Ludwig, H. Lutz, A. Scheidegger (LES)
SOLAR TECHNOLOGY 23 R. Palumbo
REKIN, AN EXPERIMENT TO STUDY THE KINETICS OF THE OXIDATION OF ZINC 25 VAPOR — CONCEPTUAL OVERVIEW AND DESIGN P. Bodek, I. Alxneit
OPTIMISATION OF THE QUENCH FOR THE SOLAR THERMAL DECOMPOSITION OF ZINC OXIDE 27 M. Keunecke, J. Lédé (LSGC-CNRS-ENSIC, Nancy, France), M. Ferrer (LSGC-CNRS-ENSIC), R. Palumbo, A. Meier
SPECTRAL REFLECTIVITY OF Fe203 AND NiO AT HIGH TEMPERATURE 29 M. Musella
TOWARDS THE INDUSTRIAL SOLAR PRODUCTION OF LIME 31 A. Meier, E. Bonaldi (QualiCal AG), G.M. Celia (QualiCal AG), W. Lipinski, R. Palumbo, A. Steinfeld (ETH Zürich and PSI), C. Wieckert, D. Wuillemin
OPERATIONAL PERFORMANCE OF A 5 kW SOLAR CHEMICAL REACTOR FOR THE 33 CO-PRODUCTION OF ZINC AND SYNGAS S. Kräupl, A. Steinfeld (ETH Zürich and PSI)
HYDROGEN PRODUCTION VIA THE SOLAR THERMAL DECARBONIZATION OF FOSSIL FUELS 35 D. Hirsch (ETH Zürich), P. von Zedtwitz (ETHZ), A. Steinfeld (ETHZ and PSI) SOLAR THERMAL EXTRACTION OF COPPER AND ZINC FROM SULFIDES 37 C. Guesdon, M. Sturzenegger
THE SOLZINC-PROJECT FOR UP-SCALING THE SOLAR CHEMICAL TECHNOLOGY FOR 39 PRODUCING ZINC AS A SOLAR FUEL C. Wieckert, R. Palumbo, M. Epstein (Weizmann Institute, Israel), G. Olalde (CNRS-IMP), H.-J. Pauling (ChemTEK), J.F. Robert (CNRS-IMP), S. Santén (ScanArc), A. Steinfeld (ETH Zürich and PSI)
PROGRESS IN THE DEVELOPMENT OF SMALL THERMOPHOTOVOLTAIC PROTOTYPE 41 SYSTEMS W. Durisch, B. Bitnar, J.-C. Mayor, F. von Roth, H. Sigg, H.-R. Tschudi, G. Palfinger
COMBUSTION RESEARCH 43 K. Boulouchos
HOMOGENEOUS IGNITION IN HIGH-PRESSURE COMBUSTION OF METHANE/AIR OVER 45 PLATINUM M. Reinke, I. Mantzaras, R. Schaeren, R. Bombach, W. Kreutner, A. Inauen
AN EXPERIMENTAL AND NUMERICAL INVESTIGATION OF TURBULENT CATALYTICALLY 47 STABILIZED CHANNEL FLOW COMBUSTION C. Appel, I. Mantzaras, R. Schaeren, R. Bombach, A. Inauen
STRUCTURE AND NOx EMISSION OF TURBULENT PREMIXED METHANE/AIR FLAMES AT 49 HIGH PRESSURE P. Griebel, R. Bombach, A. Inauen, W. Kreutner, R. Schären
EXPERIMENTS ON THE SOOT REDUCTION POTENTIAL OF OXYGENATED FUELS 51 S. Kunte (ETH Zürich), T. Gerber, M. Tulej, B. Bougie, P. Radi, P. Beaud, G. Knopp
QUANTITATIVE ANALYSIS OF TWO-COLOR RESONANT FOUR-WAVE MIXING SPECTRA 53 OF THE OH RADICAL P.P. Radi, A.P. Kouzov, P. Beaud, T. Gerber, G. Knopp, M. Tulej
FEMTOSECOND PHOTODISSOCIATION OF THE ETHYL RADICAL 55 G. Knopp, P. Beaud, P.P. Radi, M. Tulej, A.P. Kouzov, B. Bougie, T. Gerber
SOUND GENERATING FLAMES OF A GAS TURBINE BURNER OBSERVED BY LASER-INDUCED 57 FLUORESCENCE W. Hubschmid, A. Inauen, R. Bombach, W. Kreutner, S. Schenker, M. Zajadatz (Aistom), C. Motz (Aistom), K. Haffner (Aistom), CO. Paschereit (Aistom)
INVESTIGATION OF COUNTER FLOW DIFFUSION FLAMES 59 Ch. Frouzakis (ETH Zürich and PSI), A. Inauen, W. Kreutner
FLOW VELOCITY MEASUREMENTS IN A HIGH ALTITUDE SIMULATION CHAMBER USING 60 LASER-INDUCED GRATINGS B. Hemmerling, D.N. Kozlov (General Physics Institute, Moscow), M. Neracher
SIDE REACTIONS IN THE SELECTIVE CATALYTIC REDUCTION OF NO WITH NH3 62 G. Madia, M. Koebel, M. Elsener, A. Wokaun
INVESTIGATION OF THE OXIDATION OF NO OVER PLATINUM CATALYSTS 64 J. Despres, M. Koebel, M. Elsener, A. Wokaun
ELECTROCHEMISTRY 67 O. Haas
LaCo03 PEROVSKITE, A NEW COBALT REFERENCE FOR EXAFS INVESTIGATIONS 69 O. Haas, R.P.W.J. Struis, J. McBreen (Brookhaven National Laboratory, USA)
THE INFLUENCE OF SURFACE MODIFICATIONS ON THE ELECTROCHEMICAL LITHIUM 71 INSERTION PROPERTIES OF HEXAGONAL GRAPHITE P. Novak, M.E. Spahr (TIMCAL SA), H. Wilhelm (TIMCAL SA), F. Joho, J.-C. Panitz, J. Wambach, N. Dupont-Pavlovsky (University of Nancy, France) 50 KW SUPERCAPACITOR MODULE FOR THE BRESA PROJECT 74 M. Bärtschi, S. Müller, R. Kötz, R. Gallay (Montería Components S.A.), A. Schneuwly (Montena Components S.A.), V. Hermann (Montena Components S.A.)
BIPOLAR GLASSY CARBON HIGH POWER SUPERCAPACITOR 76 M. Hahn, B. Schnyder, M. Bartsch, R. Kötz, M. Carlen (ABB), D. Evard (Leclanché S.A.)
COMPARISON OF THE SELF-CHEMISORPTION OF AZURIN ON GOLD AND ON 78 FUNCTIONALISED OXIDE SURFACES B. Schnyder, R. Kötz, D. Alliata (INFM, Viterbo), P. Facci (INFM)
OXYGEN REDUCTION ACTIVITY OF Pt AND PtCo-ALLOY CATALYSTS: A COMPARISON BE- 80 TWEEN KINETIC MEASUREMENTS AND POLYMER ELECTROLYTE FUEL CELL EXPERIMENTS U.A. Paulus, C. Draschil, T.J. Schmidt (LBNL and PSI), V. Stamenkovic (LBNL), N.M. Markovic (LBNL), P.N. Ross (LBNL), G.G. Scherer
ASSESSMENT OF REFORMATE TOLERANCE IN A TWO-CELL POLYMER ELECTROLYTE 82 FUEL CELL WITH 100 cm2 ACTIVE AREA L. Gubler, G.G. Scherer, A. Wokaun
INVESTIGATION OF TEMPERATURE DEPENDENCE ON CO-POISONING IN A POLYMER 84 ELECTROLYTE FUEL CELL OPERATING WITH REFORMATE F. Hajbolouri, B. Andreaus, L. Gubler, G.G. Scherer, A. Wokaun
ON THE IMPORTANCE OF A SUFFICIENT WATER SUPPLY AT POLYMER ELECTROLYTE 86 FUEL CELL ANODES B. Andreaus, A.J. McEvoy (EPF Lausanne), G.G. Scherer
EFFICIENCY IMPROVEMENTS BY PULSED HYDROGEN SUPPLY IN POLYMER ELECTROLYTE 88 FUEL CELL (PEFC) SYSTEMS A. Tsukada, P. Rodatz (ETH Zürich)
CURRENT DISTRIBUTION MEASUREMENTS IN PE FUEL CELL OF TECHNICAL RELEVANCE 91 F.N. Büchi, A.B. Geiger R.P.C. Neto (Instituto Superior Técnico, Lisbon)
DEVELOPMENT OF A 40 kW FUEL CELL SYSTEM BASED ON AN ARRAY OF 6 POLYMER 93 ELECTROLYTE FUEL CELL STACKS F.N. Büchi, M. Ruge (ETH Zürich), P. Dietrich, F. Geiger, P. Hottinger, CA. Marmy, R. Panozzo, G.G. Scherer, P. Rodatz (ETHZ), A. Tsukada, F. von Roth
LONG-TIME PERFORMANCE OF RADIATION GRAFTED PSI MEMBRANES IN H2-02 POLYMER 95 ELECTROLYTE FUEL CELLS T.J. Schmidt, T. Rager, G.G. Scherer
IMPROVEMENT OF THE INTERFACE IN MEMBRANE-ELECTRODE ASSEMBLIES BASED ON 96 RADIATION-GRAFTED MEMBRANES J. Huslage, T. Rager, T.J. Schmidt, G.G. Scherer
RADIATION-GRAFTED POLYMER FILMS WITH IMPROVED MECHANICAL PROPERTIES 97 T. Rager, D. Beckel, C. Noirtin, P. Muff, S. Schweri, O. Haas, J. Huslage, G.G. Scherer
NOVEL MEMBRANES FOR APPLICATION IN DIRECT METHANOL FUEL CELLS 99 A.B. Geiger, T. Rager, G.G. Scherer, A. Wokaun
ACTIVATION OF EDGE-PLANE PYROLYTIC GRAPHITE ELECTRODE SURFACES BY 101 MECHANICAL ABRASION FOR ATTACHING SULFONIC ACID GROUPS B. Steiger, G.G. Scherer
HYDROGEN PRODUCTION BY METHANOL REFORMING: POST-REACTION 103
CHARACTERISATION OF A Cu/ZnO/AI203 CATALYST F. Raimondi, K. Geissler, J. Wambach, A. Wokaun
PULSED REACTIVE CROSSED-BEAM LASER ABLATION OF La0 6Ca0.4CoO3 FOR THE 104 PREPARATION OF ELECTROACTIVE THIN FILMS M.J.Montenegro, T. Lippert, S.Müller, A. Wokaun, P.R. Willmott (University of Zürich), A. Weidenkaff (University of Augsburg) FABRICATION OF MICROOPTICAL ELEMENTS IN QUARTZ BY LASER - INDUCED BACKSIDE 105 WET ETCHING G. Kopitkovas, C. David, T. Lippert, A. Wokaun COMPARISON OF LIBS AND LA-ICP-MS FOR THE ANALYSIS OF TRACE METALS 106 K. Meissner, T. Lippert, A. Wokaun, D. Günther (ETH Zürich), U. Pfeifer-Fukumura (FH-Wiesbaden)
FABRICATION OF RIE MASKS BY ArF LASER ABLATION OF THIN METAL FILMS ON 107 GLASSY CARBON M. Kuhnke, C. David, T. Lippert, G.G. Scherer, A. Wokaun
TIME RESOLVED MEASUREMENTS OF THE LASER ABLATION PROCESS OF A 108 TRIAZENE-POLYMER BY NANOSECOND INTERFEROMETRY M. Hauer, D.J. Funk (Los Alamos National Laboratory, USA), T. Lippert, A. Wokaun
FAST AND SLOW PARTICLES DURING ABLATION OF A PHOTOLABILE POLYMER 109 T. Lippert, M. Hauer, A. Wokaun, J.T. Dickinson (Washington State University, USA), S.C. Langford (Washington State University, USA)
ATMOSPHERIC CHEMISTRY 111 U. Baltensperger
LOCAL ANALYSIS OF PHOTOCHEMISTRY IN THE PO BASIN AROUND MILANO 113 J. Dommen, A.S.H. Prévôt, B. Neininger (MetAir), M. Baumle (MetAir)
EVALUATING PHOTOCHEMICAL MODEL RESULTS IN THE LOMBARDY REGION 114 N. Ritter, J. Dommen, A.S.H. Prévôt
LESS OZONE IN TICINO DURING FERRAGOSTO 115 R.O. Weber, A.S.H. Prévôt
A NEW METHOD TO DEFINE NOx AND VOC SENSITIVITY OF 03 FORMATION 116 S. Andreani-Aksoyoglu, J. Keller, A.S.H. Prévôt
CHAPOP (CHARACTERIZATION OF HIGH ALPINE POLLUTION PLUMES) 117 S. Henne, M. Steinbacher, S. Nyeki, J. Dommen, M. Furger, A.S.H. Prévôt
FIRST MEASUREMENTS WITH A PROTON-TRANSFER-REACTION MASS SPECTROMETER 118 (PTR-MS) M. Steinbacher, J. Dommen, A.S.H. Prévôt, C. Ammann (FAL, Bern-Liebefeld), A. Neftel (FAL)
THE YEAR OF GASPHASE AND AEROSOL MEASUREMENTS (YOGAM) - PRELIMINARY 119 AEROSOL RESULTS N. Bukowiecki, I. Polo, A.S.H. Prévôt, J. Dommen, R. Richter, E. Weingartner, U. Baltensperger
MOBILE MEASUREMENTS OF AIR POLLUTANTS IN THE ZURICH REGION: FIRST RESULTS 120 G. Widmer, N. Bukowiecki, A.S.H. Prévôt, J. Dommen, E. Weingartner, U. Baltensperger
WIND VELOCITY CROSS SPECTRA MEASURED IN THE RHINE VALLEY 121 M. Furger, R.O. Weber, S. Gubser (ETH Zürich)
PRELIMINARY COMPARISON OF THE SATELLITE-BASED AEROSOL PRODUCT OF MISR AND 122 SUNPHOTOMETER DATA FOR WESTERN SWITZERLAND J. Keller, C. Borel (Los Alamos National Laboratory, USA)
SPATIAL MAPPING OF AEROSOLS ON THE BASIS OF AIRBORNE IMAGING SPECTROSCOPY 123 S. Bojinski (RSL, University of Zürich), J. Keller, M. Schaepman (RSL), D. Schläpfer (RSL)
THE NEW PSI SMOG CHAMBER FACILITY FOR CONTROLLED ATMOSPHERIC CHEMISTRY 124 EXPERIMENTS U. Baltensperger, D. Baechle, B. Bitnar, J. Dommen, M. Furger, D. Paulsen, A. Prévôt, R. Richter, M. Steinbacher, E. Weingartner, M. Kalberer (ETH Zürich), M. Sax (ETHZ) R. Zenobi (ETHZ)
A DMA FLOW SYSTEM TO IMPROVE ULTRAFINE AEROSOL SIZE DISTRIBUTION 126 MEASUREMENTS D. Paulsen, E. Weingartner
ONLINE QUASI-CONTINUOUS MEASUREMENT OF ORGANIC ACIDS IN THE ATMOSPHERE 127 R. Fisseha, L. Gutzwiller, E. Weingartner, U. Baltensperger VERTICAL SIZE DISTRIBUTION OF PARTICLES NEAR A MOTORWAY 128 D. Imhof, U. Corsmeier (IMK), M. Köhler (IMK), F. Fiedler (IMK), E. Weingartner, U. Baltensperger
HYGROSCOPIC PROPERTIES OF JET ENGINE COMBUSTOR PARTICLES DURING THE 129 PARTEMIS CAMPAIGN M. Gysel, S. Nyeki, E. Weingartner, U. Baltensperger, A. Petzold (DLR), C.W. Wilson (QinetiQ)
VOLATILE PROPERTIES OF JET ENGINE COMBUSTOR PARTICLES DURING THE 130 PARTEMIS CAMPAIGN S. Nyeki, M. Gysel, E. Weingartner, U. Baltensperger, A. Petzold (DLR), C.W. Wilson (QinetiQ)
CHEMICAL CHARACTERIZATION OF THE ATMOSPHERIC AEROSOL AT THE HIGH-ALPINE 131 RESEARCH STATION JUNGFRAUJOCH (3580 m ASL) S. Henning, E. Weingartner, M. Schwikowski, U. Baltensperger
HYGROSCOPICITY OF AEROSOL PARTICLES AT LOW TEMPERATURES 132 E. Weingartner, M. Gysel, S. Henning, N. Bukowiecki, U. Baltensperger
STUDY OF THE TROPOSPHERIC AEROSOL AT JUNGFRAUJOCH BY MEANS OF 133 SIMULTANEOUS LIDAR AND IN-SITU MEASUREMENTS R. Nessler (EPF Lausanne and PSI), G. Larchevêque, I. Balin, H. Van den Bergh, B. Calpini (EPFL), N. Bukowiecki, E. Weingartner, U. Baltensperger
ISOTOPE STUDIES IN THE SWISS CANOPY CRANE PROJECT (SCC) 134 R. Siegwolf, Ch. Körner (University of Basel)
CARBON TRANSFER IN A MIXED FOREST UNDER ELEVATED C02 135 K. Steinmann, M. Saurer, S. Pepin (University of Basel), C. Körner (University of Basel), R. Siegwolf
18 8 0 VALUES OF LEAF WATER IN C02 ENRICHED TREE SPECIES 136 S. Sigrist, M. Saurer, S. Pepin (University of Basel), Ch. Körner (University of Basel), R. Siegwolf
NATURAL C02 SPRINGS: A UNIQUE OPPORTUNITY FOR STUDYING CARBON 137 SEQUESTRATION M. Saurer, P. Cherubini (WSL Birmensdori), G. Bonani (ETH Zürich), R. Siegwolf
VALIDATION OF AN 0-18 LEAF WATER ENRICHMENT MODEL 138 M. Jaggi, M. Saurer, R. Siegwolf
ENERGY SYSTEMS ANALYSIS 139
A MERGE MODEL WITH ENDOGENOUS TECHNOLOGICAL CHANGE 141 S. Kypreos, 0. Bahn
THE ROLE OF SPILLOVERS OF TECHNOLOGICAL LEARNING IN A "BOTTOM-UP" MARKAL 143 MODEL OF THE GLOBAL ENERGY SYSTEM L. Barreto, S. Kypreos
INTEGRATING LCA DATA INTO A MARKET ALLOCATION MODEL FOR CAR POWERTRAINS 145 A. Röder
APPENDIX 147 1
INTRODUCTION
Alexander Wokaun
The program of PSI's energy research departments Energy and Materials Cycles was the subject of an international audit in June of Major advances have been achieved in one of the 2001. Our presentations have been well received by central projects of the laboratory, i.e. the removal of the experts, both with respect to scientific quality and heavy metals from the solid residues of municipal application oriented relevance. The audit team stated waste incineration. It has been conclusively shown that the energy research activities represented one of that the oxidation/reduction conditions established PSI's assets, and that they should continue to focus during the thermal treatment of filter ash have a deci• on problems where PSI, due to its structure and its sive influence on the evaporation of groups of heavy unique large research facilities, could achieve a high metals. An EXAFS experiment performed at the impact both on a national and a global level. ESRF in Grenoble was key for showing, for the ex• We have placed our program in the context of three ample of zinc, that a solid state transformation of large trends that will be characterizing the develop• oxides into sulfides was responsible for the evapora• ment of the global energy system in this century: tion of this metal in several steps.
• A substitution process is taking place with re• With respect to biomass gasification, studies have spect to the primary energy carriers used. With been carried out with respect to the best way of ex• the aim of decarbonisation, coal is increasingly tracting pure hydrogen from the low calorific value substituted by oil, gas, biomass, and various gas that is typically obtained from a biomass gasifier. forms of solar energy. By consideration of the involved equilibria, it was shown that a water gas shift / pressure swing adsorp• • With regard to end energy carriers, there is a tion sequence offered advantages as compared to a move from liquid hydrocarbons to grid bound fu• solid state redox scheme. els, i.e. natural gas and hydrogen, and towards the use of electricity. High Temperature Solar Technology • The development of energy converters aims at The overarching goal of the laboratory is the use of reducing pollutant emissions and raising effi• solar energy for the production of solar fuels, or for ciencies, thereby lowering greenhouse gas re• the reduction of C02 emissions in large scale indus• lease. This trend towards "near zero emission" trial processes that are conventionally carried out with concepts applies to both combustion engines the use of fossil fuels. and electrochemical converters. In a short-term project targeted at the solar produc• The program of the General Energy research de• tion of lime, highly encouraging results (98% degree partment may be mapped upon the mentioned of calcination, adjustable reactivity of the lime) have trends. The laboratories of Energy and Materials Cy• been obtained in a 10 kW prototype reactor. cles and of Solar Technology are advancing the use of renewables (biomass, solar energy), while at the Hybrid processes, in which the calorific value of fossil same time reducing materials flows by the use of fuels is upgraded by solar energy, represent the me• closed cycles. Combustion research and Electro• dium-term strategy. In this context, the successful chemistry are both working at low or zero emission operation of the SYNMET reactor, in which zinc oxide devices that are converting the energy carriers of the is reacted with methane to produce zinc and synthe• future (methane, hydrogen) into useful energy with sis gas, represents an important milestone. For the the highest possible efficiency. The Laboratory of proof of the concept on an industrially relevant scale, Atmospheric Chemistry aims at a comprehensive a large EU project (SOLZINC) has been approved in investigation of the consequences of human energy which the solar conversion of zinc oxide with a solid use. Finally, the energy systems analysis group carbon source will be investigated. frames these efforts by placing them into the context As its long term goal, the laboratory is working at of global C02 reduction scenarios. thermochemical cycles in which solar hydrogen and The sections of this report present selected results materials will be produced without the use of auxiliary from the mentioned laboratories. An introduction by fossil fuel. In this context, the physical sciences group the head of the laboratory precedes each section, in has come up with a novel scheme in which sulfides, which the research strategy is explained and some rather than oxides, are used as starting materials. highlights are mentioned. Hence, in this general in• Copper sulfide Cu2S has been identified as a promis• troduction, only a short preview on some exciting ing raw material, from which metallic copper would be achievements will be given. produced in a solar reduction step. 2
Combustion Research Together with power electronics and controls devel• oped at ETH Zurich, the power train was thoroughly Catalytically stabilized combustion is one of the most tested in a dynamic test bed. promising schemes for reducing the NOx emissions By the time of printing of this volume, the power train of gas turbines. For the use of a catalytic combustor has been implemented into a vehicle, and was suc• upstream of the main burning chamber of the gas cessfully tested on the road over the Simplón moun• turbine, it is crucial to know the streamwise distance tain pass, as will be documented in detail in next over the catalyst where homogeneous ignition is initi• year's report. ated. The group working at this concept has made great advances in matching the observed ignition Atmospheric Chemistry distances with theory. In addition, the influence of turbulence was investigated for the first time. During a Year of Gasphase and Aerosol Measure• ments, the lab's mobile emission laboratory has been Thermoacoustic instabilities represent a major chal• regularly sampling a route comprising downtown and lenge for the operation of large gas turbines. The rural areas in the canton of Zurich. Interesting trends laser diagnostics group has made a significant contri• on the generation and transport of ultrafine aerosol bution towards solving this problem. Using in situ particles, as well as ozone generation, are emerging spectroscopy, they have been able to show that the from the data. pressure waves originate from periodic heat release within the flame front itself. Towards the end of the year, the aerosol group suc• For instationary combustion in Diesel engines, ex• ceeded in finalizing a smog chamber, which will rep• haust gas aftertreatment will be indispensable for resent a powerful laboratory tool for investigating the generation and surface chemistry of aerosol particles. reaching the low NOx emission standards prescribed by the forthcoming EURO IV and V regulations. In These studies supplement the field work carried out this context, we have investigated the so-called 'fast' both on roadside and at the high-alpine station at the selective catalytic reduction reaction, and were able Jungfraujoch. to show that partial conversion of NO into N02 (e.g., Pollutant flows into ecosystems are studied using by means of an oxidation catalyst) is advantageous stable isotopes of carbon, nitrogen, and oxygen as for the conversion of the nitrogen oxides into the de• tracers. Particular attention was paid to the carbon sired inert nitrogen molecule. uptake by plants and canopies under conditions of
elevated C02 concentrations, as established in field E lectrochem istry experiments or existing close to natural C02 springs. Besides a strong signature of the meteorological Energy storage activities included work on advanced conditions, clear evidence for the down-regulation of lithium-ion batteries. An air electrode for the zinc/air photosynthesis was found under conditions where battery was prepared, for the first time, by pulsed plentiful C02 is available - a fact that might be highly laser deposition. relevant for assessing the C02 binding capacity of In situ characterization methods have been used forest sinks. successfully to advance our understanding of the low temperature polymer electrolyte fuel cell. It was Energy Systems Analysis shown that the use of milder preparation conditions Technological learning must be quantitatively as• resulted in improved mechanical properties of the PSI sessed, and included in bottom-up engineering mod• membrane. Impedance spectroscopy gave clear hints els of the energy system, to obtain a faithful predic• that maintaining a small pressure difference is bene• tion of the optimum energy mix under a set of C02 ficial for maintaining proper humidification of the emission constraints. The systems analysis group membrane. For fuel cells running on reformed fuel, has applied this concept to study expected changes the effect of temperature on the CO tolerance was in the stock of motorized individual vehicles, and the quantified. interaction of learning with market-based instruments A major effort of the laboratory was devoted to the as emission trading. realization of a complete power train for a fuel cell In May of 2001, PSI's energy research departments vehicle. A module consisting of six fuel cell stacks (of opened their doors to the interested public, and more 8 kW power each) was assembled, tested and sup• than 1600 visitors have used this opportunity to dis• plied with auxiliaries for fuel and air supply, as well as cuss with our scientists on question related to the cooling. The fuel cell was supplemented by a 60 kW present and future of energy. We are determined to supercapacitor module, capable of storing the break• continue this fruitful dialogue in 2002, and to commu• ing energy of the vehicle and providing power during nicate relevant news via channels addressed at the acceleration, thereby supplementing the fuel cells. interested public. 3
Energy and Materials Cycles 4
LABORATORY FOR ENERGY AND MATERIALS CYCLES
Samuel Stucki
Sustainable management of material and energy re• ide redox cycle is handicapped with respect to both, sources implies that, in a long term, renewable ener• investment cost and efficiency. Large-scale production gies will be used to drive closed material cycles. The of hydrogen from biomass for decentralized use in mission of the Laboratory for Energy and Materials small fuel cell power units will not become of interest Cycles (LEM) is to carry out research into technologies before an efficient hydrogen distribution system will be for producing clean fuels and secondary raw materials in place. We have therefore started to focus on alter• from biomass, waste and fossil resources using ther• native strategies to use existing biomass resources for mal and catalytic processes. Improving the eco- providing fuels and/or electric power. Common to all efficiency of products and services (i.e. more value for advanced processes for converting biomass fuel is the less pollution and less resource intensity) has been production of a clean and versatile gas, which can the guiding principle of the research projects at LEM. either be used as a fuel gas for electric power genera• tion, or converted to a marketable fuel, such as e.g. Hydrogen is the ultimate fuel for clean energy conver• synthetic natural gas (S. Biollaz et al). sion in fuel cells. Its production from liquid fuels, such as methanol (F. Vogel) has been the focus of much of The behaviour of volatile elements and compounds in our activities. Systems' and economic analysis have thermo-chemical processing of wastes and bio-fuels is shown that hydrogen for mobile fuel cell applications of central importance if the avoidance of hazardous will have to be produced from available hydrocarbon waste deposition and the recovery of potentially valu• resources in the near to mid term. We have therefore able metal resources are taken into account. The increasingly focused our fuel processing activities on processes governing the volatilisation of e.g. Zn from catalytic partial oxidation of hydrocarbon fuels (E. fly ash have been studied in detail, using on-line moni• Newson et al). Whether or not the fuel conversion to toring of metal species in hot gases and taking into PEM-grade hydrogen on-board a vehicle will be a account the composition of the ash components, as viable option will depend critically on the question how well as the partial pressure of the gas phase (H. Lutz such catalytic converters will be capable of responding et al). Our unique on-line method for the analysis of to varying load and cold start-up. The dynamics of a metal vapours is based on the formation of aerosol catalytic fuel processor has been studied using the particles in a quenching process. We have started to conversion of methanol to DME, a relatively simple study the influence of quench conditions on the forma• reaction with low enthalpy change and running on a tion of such particles (T.Barone et al.). The speciation chemically very stable catalyst (H. Armbruster et al.). and chemical neighbourhood of trace metals in ashes Catalytic partial oxidation reactors exhibit a much are of central importance for the thermo-chemical more complex chemistry with local thermal effects, the behaviour of the materials. We have successfully ap• dynamics of which raise questions to be addressed in plied synchrotron radiation (EXAFS) for identifying the the future. chemical speciation of Zn in fly ash samples treated at various temperatures (R.P.W. Struts etal.). Hydrogen production from biomass has the potential of providing renewable fuel for fuel cell applications with clearly lower costs than present-day solar hydro• In 2002 LEM has been active in a number of projects gen options. However, the study carried out by R.Sime funded by government agencies and by industry, inclu• et al. has shown that the economy excludes small ding a consulting job in a major technology evaluation decentralized technologies for producing hydrogen for an advanced process for thermal treatment of and that the investigated approach using the iron ox• automotive shredder residues. 5
PARTIAL OXIDATION OF METHANOL ON A COPPER CATALYST
F. Vogel
The partial oxidation of methanol was investigated in both a fixed-bed microreactor and in a thermogra• vimetric analyser (TG-FTIR) at 180°C and 220°C using a copper-based catalyst. In the microreactor, a hot spot in the undiluted catalyst bed of 4 K and 32 K was observed at 180°C and 220°C, respectively. Methanol conversion was strongly accelerated between 180°C and 220°C. In the TG-FTIR experiments the reduced copper was oxidized in the presence of oxygen and methanol (O^MeOH = 0.24) at 180°C,
while at220°C it remained reduced for the same 02/MeOH ratio. Both hydrogen and methanol are able to reduce the oxidized copper to its initial oxidation state. These observations are consistent with the hy•
pothesis that adsorbed CO and H2 are oxidized faster than Cu.
INTRODUCTION 3 RESULTS
Methanol is considered as one liquid fuel option for Two experiments at 180°C and 220°C were performed fuel cell powered electric cars. Hydrogen for the in the fixed-bed microreactor. The departure from the Polymer Electrolyte Membrane (PEM) fuel cell can be oven temperature is shown in Figure 1. At 180°C the extracted on-board from methanol by steam reform• temperature profile was almost flat with a hot spot of 4
ing, partial oxidation (POX, 1), or a combination of K. C02, methyl formate, and oxygen were detected in both reactions. the effluent gas.
CH3OH + 0.5 02 -» C02 + 2 H2 (1)
Heterogeneous copper-based catalysts exhibit an ~o~ Oven setpoint 180°C excellent selectivity to hydrogen since they do not --»-- Oven setpoint 220°C catalyse the methanation reaction, as opposed to nickel. Oxidized copper (CuO), however, has no activ• ity for POX, and only total oxidation to carbon dioxide and water is observed. To gain a better understanding of the reactions involving both methanol and oxygen 5* on a reduced copper catalyst, experiments in a fixed- 1Ï SiC Catalyst (750 mg) SiC bed microreactor as well as a thermogravimetric study 1 on a commercial copper catalyst were performed. Axial distance from beginning of catalyst bed (cm)
2 EXPERIMENTAL Fig. 1 : Axial temperature profiles for the partial oxida• Microreactor experiments were performed in a fixed- tion of methanol in a fixed-bed microreactor. Feed:
1 bed tubular reactor (4 mm I.D.), fitted with a thermow- MeOH:02:N2 = 5:1:120. WHSV = 2.2 h" . Oven tem• ell (1.5 mm O.D.) for measuring axial temperature perature: o 180°C, • 220°C. profiles. 750 mg of a commercial Cu/ZnO/AI203 cata• At 220°C the picture changed dramatically. A hot spot lyst (particle size range 125-250 urn) was sandwiched of 32 K was observed right at the beginning of the in the reactor between two layers of SiC. The reactor catalyst bed. Thermal conduction in the stainless steel was placed in the isothermal zone of an electrically thermowell and probably also thermal dispersion in heated oven developed at PSI. Reduction of the cata• the gas smeared the axial temperature profile no•
lyst was performed under flowing 20% H2 at 300°C for ticeably. In this experiment, H2, C02, CO, and methyl 2 h. Methanol was fed to the reactor at a weight hourly formate were detected in the effluent gas, but no oxy• _1 space velocity (WHSV) of 2.2 h . The gaseous efflu• gen. ent was analysed for CO, C02, H2, N2, 02, CH4 using GC/TCD with a two-column switching system. Obviously, methanol conversion is strongly acceler• ated between 180°C and 220°C. This is consistent Thermogravimetric studies (TG-FTIR) were performed with the results from Fierro [1] who found a fast in• in a DuPont 951 thermogravimetric analyser coupled crease in methanol conversion, and H2 and C02 yields to a BOMEM MB-100 FTIR analyser. Ca. 50 mg of around 215°C for the partial oxidation of methanol on catalyst were placed in a metal screen basket and a Cu/ZnO catalyst. suspended on the thermobalance. Helium, hydrogen, oxygen, and helium loaded with methanol were fed to Studying methanol POX in a TG-FTIR has several the TG-FTIR according to the sequences described advantages over the microreactor setup such as (/) below. Product gases were analysed in the FTIR de• nearly isothermal conditions due to a rapid tempera• tector for CO, C02, H20, methanol, methyl formate. ture control, (//) the mass signal reflecting changes of 6 the catalyst, (///) FTIR enabling on-line analysis of After 67 min. hydrogen was turned off and oxygen gaseous products. Figure 2 shows the evolution of the was added to the helium. The mass of the catalyst catalyst mass over time. During the temperature ramp increased steadily to 101.6% of its initial value. We from 45°C to 180°C a mixture of hydrogen and helium assume that at this point the catalyst was fully oxi• was flowed over the catalyst to degas and reduce it. dized. Then, the feed was switched to ca. 1 % metha• At 180°C reduction was fast as reflected by the rapid nol in helium. As can be seen from Figure 3, the cata• drop in catalyst mass after 25 min. After 44 min. the lyst mass decreased rapidly to almost the same level feed was switched to methanol/helium. The mass of as after reduction with hydrogen/helium. The high CO the catalyst increased slightly, probably due to the concentration (not shown) indicated methanol decom• adsorption of methanol. At the same time hydrogen position according to (2). After 132 min. oxygen was and CO were evolved (not shown) from the dehydro- added to the methanol/helium stream (02/MeOH = genation of methanol according to (2): 0.1). Interestingly, no increase in catalyst mass was observed under these conditions. An increase of the
CH3OH -> CO + 2 H2 (2) 02/MeOH ratio to 0.24 did not change the mass, as opposed to the first experiment at 180°C. A further After 115 min. a mixture of methanol, oxygen, and
increase of 02/MeOH to 0.5, however, led to a slow helium was fed to the TG-FTIR. The oxygen-to- increase of the mass. Unfortunately the experiment methanol ratio was 0.24. As can be seen from Fig• had to be stopped before a steady value for the mass ure 2, the mass of the catalyst increased monotoni- was reached. cally indicating the oxidation of the copper catalyst.
4 CONCLUSION
• Both H2 and methanol reduce the oxidized copper to the same extent. After reduction the copper is
101 £ assumed to be present as Cu° only.
,00 I • POX at 220°C with 02/MeOH = 0.24 does not oxi• 99 5 dize the copper, i.e. the copper is still present as
Cu°, whereas at 180°C and 02/MeOH = 0.24 the copper is oxidized.
• With 02/MeOH = 0.5 at 220°C the catalyst mass seems to attain a value between fully oxidized and Time (min.) fully reduced.
Fig. 2: Temperature ramp and mass evolution for a • Oxygen reacts faster with adsorbed CO and/or H2 copper catalyst exposed to different environments: A (or an intermediate species, e.g. HCHO) than with
Cu. As soon as most CO and H2 are oxidized, Cu H2/He, B MeOH/He, C He, D MeOH/02/He (02/MeOH = 0.24). is oxidized as well.
A second experiment was performed where the tem• • Below ca. 200°C methanol decomposes to CO and perature was increased up to 220°C (Figure 3). After H2 slowly, and thus only little oxygen is needed to degassing and heating to 220°C hydrogen was added oxidize these products. Above ca. 200°C methanol at D to reduce the catalyst, the mass of which de• decomposition is fast and yields large amounts of creased rapidly by about 2%. CO and H2. Thus more oxygen is required before the Cu surface is oxidized as well.
: ! ! ! : • Depending on the 02/MeOH ratio and the tempera• 240 ! ! ! ! ! L M. ! - - - - !!»--- „ J. * ture the Cu surface may be stabilized at an oxida• 200 -j—/r i " " i i!" !" ¡v : tion level between 0 and +2. !I ! / ! ' rf**"^ Iii (Oo ) 160 ! ! ! g* ¡II 5 ACKNOWLEDGEMENTS * 1 ï • J y- § / ¡ \L fljHi/-y ¡ ! / ! ! 2 120 th He, B MeOH/He, C He, D H2/He, E 02/He, F tions for the production of hydrogen, 12 Interna• MeOH/He, G MeOH/02/He (02/MeOH = 0.1), H tional Congress on Catalysis, Granada, Spain, 02/MeOH = 0.24, I 02/MeOH = 0.5. July 9-14, (2000). 7 LOW TEMPERATURE CATALYTIC PARTIAL OXIDATION (POX) OF HYDROCARBONS (d TO C10) FOR HYDROGEN PRODUCTION E. Newson, T.B. Truong, A. Fleury Hydrocarbon reforming by autothermal partial oxidation to produce hydrogen for stationary and mobile applications has shown, in the temperature range 500-600°C, significant hydrogen yields from liquid (C4- C10) and gaseous (CrC4) hydrocarbons. Hydrogen rates equivalent to methanol autothermal reforming at 330°C have been measured. Noble metal oxides on mixed oxide supports were used for 200- 400 hours continuous operation. Future work lies in scaleup and reaction engineering to control the hotspot in the 1-2 kWth range. 1 INTRODUCTION the microreactor having an internal diameter of 4mm with a total length of 130 mm. The length of the cata• Hydrogen production from liquid or gaseous hydro• lyst bed was 10-20 mm depending on dilution of the carbon fuels would serve to bridge the transition from catalyst (100-200 mg) with a particle size of 0.125- hydrocarbon to hydrogen systems. 0.250 mm. Feed and product systems were all under The stoichiometry of producing hydrogen by catalytic PC control for safe and continuous operation for sev• partial oxidation (pox) of hydrocarbons instead of eral hundred hours to follow catalyst deactivation. methanol is compelling. For mobile applications, well- Product analyses were by GC-FID-TCD facilitating to-wheel analyses for low temperature fuel cell sys• mass balances (C/H/O) over the system. tems [1] suggest a higher full fuel cycle efficiency (ffc) for hydrocarbons (27%) than methanol (24%), both exceeding the ffc internal combustion engine effi• 3 RESULTS AND DISCUSSION ciency of 18%. Socio-economic factors such as public Results were obtained with methanol and isooctane, a acceptance, in-place infrastructure and world-wide representative gasoline component with a research distribution systems, also favour hydrocarbons. octane number (RON) of 100. The temperature range Natural gas (primarily methane) could find application was 300-600°C, 1-10 bar pressure, with process pa• in stationary combined heat and power systems. rameters (air, A02, water, AH2o) being optimised to This report describes the POX catalyst screening of maximise hydrogen production and minimise carbon hydrocarbons using noble metals on mixed oxide monoxide and coke formation. The results in Table 1 supports for both gaseous (C-|-C4) and liquid hydro• contrast the pox parameters for hydrocarbon and carbons (C4 -C10) from a refinery i.e. isomerates (C4- methanol feeds at about the same extrapolated hy• C7) and platformates (C5-C10), with less than 1 ppm drogen production rates i.e. space time yields (STY), sulfur content. of about 27,000 litres H2/hour/litre reactor volume(lrv) or power density of about 80 kWth/lrv. 1 CH4 + /2 02 + H20 = C02 + 3 H2 ISO 30-04 (i-C8) KG-BIF (MeOH) C8H18 + 2 02 + 12 H20 = 8 C02 + 21 H2 T[°C] 550 330 2 EXPERIMENTAL P [bar] 4 1 The laboratory reactor system is shown in Figure 1, WHSV [hr"1] 14 18 ^02 1.15 1.0 Mb. ^ jFCl ÀH20 1.10 1.0 l|§-i><—txà- Hot Spot [°C] 45 11 Conv. [%] 65 98.5 Yield 37.9 93.0 STY [IH2/hlrv] 27,965 25,500 Power Dens. 83.9 76.5 [kWth/lrv] %CO 6.2 2.0 .... % CH4 1.0 %o2 0.39 0 Fig. 1 : Microreactor for autothermal partial oxidation Table 1 : Partial oxidation of isooctane (i-C8) and of hydrocarbons. methanol (MeOH). 8 The main difference between methanol and hydrocar• The same catalysts have been successful for gaseous bons is the operating temperature to achieve signifi• hydrocarbons i.e.natural gas (mainly methane) . Table cant hydrogen yields, 330°C versus 550°C respec• 4 compares pox results for liquid (C4-C8, RON=92) tively. The potential for hydrocarbons is clear with the and gaseous (CrC4) hydrocarbons. modest conversion of 65%. CO values can be lowered by adjusting the water parameter (AH2o)- C4-C8 Ci-C4 Gasoline composition is shown in Table 2 by PONA TEMPERATURE (°C) 550 550 analyses, including research octane numbers (RON). PRESSURE (bar) 5 3 P : PARAFFINS (e.g.n-heptane,RON=0; iso-octane, RON=100) GAS HOURLY - 104,840 43,000 O : OLEFINS SPACE VELOCITY (h1) N : NAPHTHENES (e.g.methylcyclohexane,C7H14) CONVERSION % 68.6 77 A : AROMATICS (e.g.toluene,C7H8, RON=110) % H2 PRODUCT - 41.7 56 ISOMERATE (RON=88,C/H=5.3; i-C5, n-C5,2-2-DMB) GAS (DRY) 98%/<1%/ 1% / 1% /<1PPMS POWER DENSITY 91 26.4 PLATFORMATE (EX PLATFORMER, RON=98) (KWth/litre reactor) 27% / <1 % / 1.4% / 71% / <1 PPM S % CO IN PRODUCT GAS 3.5 1.5 Table 2: Gasoline composition PONA analyses. Table 4: POX comparison of liquid (C4-C10) and gase• From a refinery in Switzerland, Tamoil, Collombey, ous (Ci-C4) hydrocarbons. isomerates and platformates have been freely sup• plied, so that hydrocarbon feeds (< 1 ppm sulfur) with The operating temperature of 550°C is about 250°C representative research octane numbers, lower than conventional endothermic steam methane 92 For liquid and gaseous hydrocarbons, reactor tem• ISO 29-03 (i-C8) ISO 35-09 (i- peratures (500-600°C) exceed the ignition tempera• Cs/lsom) tures of isooctane/air (210°C) and propane/air (479°C) T[°C] 550 550 compared to methanol/ air (455°C). Control is main• tained by limiting the oxygen content of the reactant P [bar] 3 3 gases under the "inerting" effect of nitrogen and water. WHSV [hr"1] 14 14 5 CONCLUSION, FUTURE WORK 1.3 1.19 Significant yields and extrapolated power densities of 1.05 1.45 ÀH20 hydrogen from hydrocarbons by partial oxidation have Hot Spot [°C] 51 51 been demonstrated on a laboratory scale. Refinery feeds (RON 92) and natural gas mixtures have also Conv. [%] 61.1 68.6 been tested with positive results. Further work lies in scaleup and reaction engineering to control hotspots Yield 33.4 39,3 in the 1 -2 kWth range. STY [IH2/hlrv] 24,640 30,350 6 ACKNOWLEDGEMENTS Power Dens. 73.9 91.6 [kWth/lrv] The Tamoil refinery, Collombey is specially acknowl• edged for the liberal supply of refinery samples and %CO 4.35 3.29 their analyses; Haldor Topsoe A/S, Denmark for the % CH4 1.40 2.63 methanol catalysts. %02 1.04 0 7 REFERENCES Table 3: Partial oxidation of isooctane (i-C8) and [1] B.L. Höhlein, Fuel Systems for Transportation, i-Ce/isomerate. Proc. IEA Adv. Fuel Cell Workshop, Wislikofen, CH, 43, (1997). Extrapolated power densities are significant with po• tential for higher conversions, since temperature can [2] L.D.Schmidt, Millisecond Chemical Reactions and be raised to 600°C. Catalyst lifetimes are 200-400 Reactors, Studies in Surface Science and Cataly• hours with noble metals on mixed oxide supports. sis 130, Eds. A.Corma et al., Elsevier (2000), 61. 9 A NEW REACTOR CONCEPT FOR IMPROVED HEAT INTEGRATION IN AUTOTHERMAL METHANOL REFORMING K. Geissler, T. Schildhauer With regard to mobile applications, the autothermal methanol reforming process as hydrogen source for PEM-fuel cells has advantages compared to the externally heated steam reforming reaction in terms of control and transient behaviour. However, thermal (hot-spot) control of the autothermal process turns out to be the key issue for scale-up in order to ensure selectivity, catalyst stability and process safety. There• fore, a novel reactor concept based on catalytically coated plates has been developed. It shows a low pressure drop, improves heat integration and solves the scale-up problem of autothermal methanol re• forming. These improvements have been shown in experiments using Cu/Zn/Al203 as catalyst. 1 INTRODUCTION the catalyst are media for heat transfer and no limiting gas-solid heat transfer is involved (Figure 2). Figure 3 The objective of this work was to improve the reactor shows schematically the reactor concept. concept for autothermal methanol reforming which can be applied as a hydrogen source for polymer electrolyte fuel cells. Since liquid methanol has a higher energy density per volume compared to hydro• gen, it could be especially advantageous as a hydro• gen storage medium for non-stationary applications. Autothermal methanol reforming can be considered as a combination of exothermic partial oxidation (with air) and endothermic steam-reforming (with water). Al• though the stoichiometry of the reactants can be ad• justed to yield an overall reaction enthalpy of zero, the different reaction rates of exothermic fast methanol oxidation and endothermic slow steam reforming often cause an unbalanced temperature profile. If simple tubular reactors are used, significant hot spots in the entrance region can occur. During scale-up this prob• lem becomes more and more severe, eventually even being a safety issue if it comes to run-away. In addi• tion, even comparatively moderate hot-spots of below 400°C can shorten catalyst lifetime, particularly with reactor length copper catalysts, and lead to increased formation of the unwanted by-product carbon monoxide due to the accelerated water-gas shift reaction. Fig. 1 : Changing of the axial reactor temperature profile due to the introduction of flow reversal. 2 THE NOVEL REACTOR CONCEPT To solve this problem, different possibilities can be en• visaged. The first one, the removal of heat in the hot- spot region, is not acceptable for mobile applications since efficiency of the reactor decreases. Another C02 + 2 H2 CH3OH + % 02 way, described in [1], is the distribution of the heat production over the reactor length by splitting the 02 feed. This method is either technically difficult due to control problems or causes high pressure drops. Cu/Zn/AI2i Therefore, the novel reactor concept suggests a spa• tial coupling of the exothermic and endothermic reac• C02 + 3 H2 2 tion zones. To realize this aim, a reversal of the flow CH3OH + H 0 direction after the hot-spot is introduced. It allows to use released heat at the backside of the contact area, as shown in Figure 1. The flow reversal is combined with the use of catalytically coated plates for the opti• misation of the heat transfer. The reactions occur Fig. 2: The catalytically coated plate enables optimal directly at the surface of the plate, so only the wall and heat transfer by conduction. 10 - improved catalyst life-time due to flattened tempera• ture profile - extremely low pressure drop, hence minimised power loss from gas compression O O (! O - self-regulating system for changing loads - heat exchanger function for pre-heating of feed can easily be implemented - high mechanical stability of the catalyst against vi• brations and shocks typically occurring in mobile ap• plications - cheap and simple substitution of de-activated cata• lyst filling without exchange of expensive pressure- tight parts - construction can be adapted to autothermal reform• ing of basically any hydrocarbon feed, e.g. methane, Fig. 3: Schematic reactor concept. LPG or petrol. 3 EXPERIMENTAL 350 To prove the concept, a small test unit was built con• sisting of 10 plates (FeCrAlloy, thickness 0.08 mm) with an active surface of each 36 cm2, mounted in a 330 -- isolated stainless steel housing. The active surface 2 was coated with 1.75 mg/cm Cu/Zn/Al203 catalyst. The distance between the plates was 3 mm. Nine 310 -- thermocouples monitored the temperature in the reac• tor. The equal distribution of the feed streams was realized by capillaries. 290 -- 4 RESULTS 270 -- At pre-heating temperatures between 252°C and Tubular Reformer 285°C, weight hourly space velocities between 5 1 and 10 gMeoH(gKat h)" conversions up to 65% were 250 _i i i i i i i j i i i i i i i i i i i_ measured by GC-MSD-analytics. 12 3 4 length of reactor (cm) Figure 4 shows the temperature profiles of autother• mal methanol reforming in a tubular (500 mg catalyst) and the new reactor (600 mg catalyst) at equal methanol space velocities. For the new PSI reformer the air flow is 50 % higher than the amount fed to the Fig. 4: Temperature profiles of autothermal methanol tubular reformer. It can be seen that the temperature reforming in a tubular and the new reactor at equal profile remains flat. Even with doubled air feed no methanol space velocities. temperature gradients over 27K could be measured. 6 ACKNOWLEDGEMENTS 5 CONCLUSION Major constructional support by Peter Binkert and It has been proved that the reactor works stable at Fritz von Roth is gratefully acknowledged. Südchemie high conversions. Low hot spots (max 27 K) with „mir- (D) supplied commercial catalysts under a confidenti• ror hot spot" at reverse side of plate flatten considera• ality agreement. bly the axial temperature profile. This allows easy scale-up by adding more plates to the reactor. There• fore, the novel reactor type has some advantages 7 REFERENCES over state-of-the-art reactors: [1] Schüssler, M., Entwicklung eines kaltstartfähigen Reaktors für die autotherme Reformierung von - easy adjustment of reactor size to the desired hy• Methanol, Fortschritt-Bericht VDI, Reihe 6, Ener• drogen output since heat transfer conditions are not gietechnik. Düsseldorf, 1998. changed during scale-up 11 ON-BOARD FUEL CONVERSION: DIMETHYL ETHER FROM METHANOL FOR COMPRESSION IGNITION ENGINES H. Armbruster, S. Stucki One example of an on-board fuel conversion system is the fumigation of dimethyl ether. In this concept, a fraction of the methanol used as fuel is catalytically converted on-board to DME and water. The rate- determining step of the catalytic reaction with y-AI203 as a catalyst is found to be the reaction of adsorbed intermediates; mass transfer is limited by Knudsen diffusivity. Providing DME for fumigation in a 180 kW engine will require approx. 0,7 kg of catalyst. The transient behavior of a pilot fixed-bed reactor has been estimated using simplified models, which show that the cold start should be manageable in less than one minute. This is an acceptable time for cold-starting an engine in heavy-duty vehicles. 1 INTRODUCTION (r 1_ 1_ -AE with ks = kn-EXP The conversion of fuels on-board a vehicle is a central theme today. As an example of a catalytic conversion reaction the production of methanol to dimethyl ether (r 1 1 -AG, W,M (DME) and water was studied. Alcohol fuels (methanol and Kw¡M=KWiM(TR)-EXP and ethanol) have interesting advantages with respect T 7RJ, to emissions and, since they can be produced from biomass, represent one possible way of introducing K is the equilibrium constant of the DME formation renewable fuels into transportation applications. The reaction: 2 CH3OH <-> CH3-0-CH3 + H20. disadvantage of methanol is it's bad ignition behavior The rate constant of the surface reaction (ks) and the in compression ignition engines. adsorption constant KWM (W=water, M=methanol) depend on temperature and are given by the modified A system analysis revealed that fumigation of DME is Arrhenius equations above. The parity plot in figure 1 an interesting option for using methanol as a fuel in shows that the model describes the measured data compression ignition engines. In this concept, a frac• reasonably well. The activation energy of 123 kJ/mol tion of the methanol used as fuel is catalytically con• we measured for the reaction is lower than the litera• verted on-board to DME and water, and the products ture value of 140 kJ/mol [1,3]. of the conversion are introduced into the engine via the combustion air. Emission investigations show that the EURO-V limit values are kept with an oxidation catalyst. 2 KINETIC MEASUREMENTS The methanol conversion was tested with different catalysts (y-AI203, H-Mordenit, DOW EX, Nation) under various conditions such as temperature from 100°C to 400°C, WhSV from 3 to 30 1/h, pressure from 0,5 to 5 bar, particle size from 0,063 to 1 mm and mass of catalyst from 0,41 to 1,25 g. Because of its superior thermal stability and low costs, y-AI203 was selected as the most promising catalyst for converting methanol to DME in sufficient rates for an on-board application. 0,4 0,6 0,8 conversion observed The kinetics of the methanol dehydration reaction over y-AI203 catalyst was evaluated by a large set of meas• Fig. 1 : Parity plot for methanol dehydration reaction urements. The reaction is best described by a Lang- kinetic. Good agreement between measured and fitted muir-Hinshelwood mechanism involving the reaction of data is shown. adsorbed intermediates as rate determining step [1, 2]. The rate of methanol consumption, which fits best 3 EXPERIMENTS AND MODEL OF THE TRAN• our experiments, is given in the following equation. The equation is similar to the results of [3]. SIENT BEHAVIOR OF THE PILOT PLANT A pilot conversion reactor loaded with 110 g of catalyst (y-AI203) was built to study the transient behavior of kS • Km{PM -PWPE/K) -r, M the catalytic system. This pilot plant allows to study the (l + 2^]KM • PM +KW • Pw) heat management and the cold-start dynamics of the 12 reactor. For start-up, prior to feeding methanol to the tween experimental data and modeling with respect to catalyst bed, it is heated by a flow of hot gas, simulat• the evolution of the DME production rate (Figure 2(c)). ing the exhaust of e.g. a catalytic methanol burner. Altogether it was shown that, starting from ambient Electric heating coils for controlling and varying the temperature, it takes the reactor system 4 to 5 min• wall temperature of the reactor surround the pilot reac• utes to reach steady state operating conditions. Here tor. The temperature in the bed is measured with sev• again the data show good agreement. The models eral thermo-couples along the reactor. The product succeed in predicting the conversion of methanol. gas is analyzed with a gas Chromatograph and, for recording fast response (seconds) of the system, a mass spectrometer. 4 OUTLOOK AND CONCLUSION The experiments with the pilot reactor have allowed us In Figure 2 an example of a cold start-up experiment to validate the models of the reactor. The model can is shown, along with modeling results. Figure 2(a) be used to calculate the design parameters (mass of shows the measured evolution of the temperature at 6 catalyst required, start-up time, etc.) of a technical on• given positions inside the reactor. board converter. For a 180 kW engine 0,7 kg of y- heating-up formation of ether Al203 are required resulting in a compact and afford• able reactor design. Design calculations using the model show that such a reactor would be ready for steady state production within 25 sec if heated with hot gas of 600°C from a methanol burner. From our point of view, 25 sec warm-up is acceptable for operating buses, trucks or heavy-duty engines. The results form this work can be applied to study other systems with on-board fuel conversion. A fast heating-up of the reactor can only be obtained if the operating temperature of the reactor is low and at the same time the temperature tolerance of the catalyst is high. The enthalpy change of the methanol dehydra• tion reaction is small and therefore hot or cold spots are not an issue. This is, however, one of the central problems with most fuel converters such as gasoline reforming for fuel cell applications. The on-board fuel conversion is technically feasible. The development of the on-board fuel conversion into a commercial product is, however, still a great chal• lenge for engineers. Fig. 2: Experimental data and model calculation for a cold start-up, temperatures and methanol conversion. 5 REFERENCES Approx. 300 s are needed to heat the reactor from [1] K. Bakshi, G. Gavalas, Effects of Nonseperable 25°C to 300°C with a flow of gas of T=400°C. The Kinetics in Alcohol Deydration over Poisoned Sil• heating-up period can well be simulated using a sim• ica-Alumina, AlChE J. 21, 494 (1975). ple one-dimensional model (Figure 2(b)). It takes an• other 100 s between the beginning of methanol feed• [2] E. DeCanio, V. Nero, J. Bruno, Identification of ing and the detection of DME at the outlet of the reac• Alcohol Adsorption Sites on y-AI203, J. of Cataly• tor. sis 135, 444 (1992). The simple thermal model does not quantitatively pre• [3] G. Bercic, J. Levee, Intrinsic and Global Reaction dict the temperature profiles during the initial phase of Rate of Methanol Dehydration over y-AI203 pel• dehydration; however, there is good agreement be• lets, Ind. Eng. Chem. Res. 31, 1035 (1992). 13 THE REDOX PROCESS FOR PRODUCING HYDROGEN FROM WOODY BIOMASS R. Sime, J. Kuehni, L. D'Souza, E. Elizondo, S. Biollaz, S. Stucki Hydrogen may be made from biomass fuel gas using a method of cyclic reduction and oxidation (REDOX) of iron oxides. The production of hydrogen using REDOX technology has been modelled. These studies showed that the hydrogen production efficiency depends significantly on the gasifier fuel gas composition and the thermochemical properties of the REDOX material. A lab scale REDOX system was developed to provide experimental data. Good agreement between experimental and theoretical data was obtained. However, the inherent thermodynamic constraints of the REDOX process limit the maximum efficiency. The REDOX hydrogen process is significantly less efficient and more costly than conventional hydrogen technology. 1 INTRODUCTION sition was measured using a Prima 600 mass spec• trometer. Gas composition, water flow, gas flow and A number of strategies have been developed for pro• temperature are monitored in real time using Labview ducing renewable hydrogen from biomass. One strat• software. The equipment is suitable for measuring the egy is based on cyclic reduction and oxidation conversion of fuel gas to hydrogen. (REDOX) of iron oxides [1]. The biomass is first gas• ified to produce a flammable fuel gas containing CO, C02, H2, H20, CH4 and N2. gasification Biomass- *Fuel gas RED0X ) Hydrogen REDOX technology (Figure 1) is used to produce hy• drogen from fuel gas in two stages: 1. Fuel gas is used to reduce magnetite (Fe304) to wuestite (FeO). 2. The wuestite is reoxidised to magnetite using Condenser steam. Hydrogen is produced after condensation of the remaining steam. Balance Flow Fuel gas Hydrogen Steam-hydrogen j 0 Meter m »fr 1 Water Mass spectrometer Condenser Gasifier Water Fig. 2: Experimental REDOX equipment. 3 RESULTS AND DISCUSSION î T niiiiiiiii Bajjij^BI IM The gasifier fuel gas quality is an important issue for Air Wood the REDOX technology development. The effect of the Fuel gas I^B^B^a^aVgas-* fuel gas composition has been modelled. The model• Air ling showed that the potential hydrogen production efficiency is strongly dependent on combustion- Fig. 1 : Basic REDOX process. products/ fuel ratio ((C02+H20)/(CO+H2) = C/F) of the fuel gas. The effect of the fuel gas C02/CO ratio on 2 EXPERIMENTAL the chemical conversion was then measured over a range CO-C02 mixtures (Figure 3). Good agreement An objective of this work was to maximize the conver• was obtained between experimental results and mod• sion of fuel gas to hydrogen. Experimental equipment elled predictions. The modelled line assumes an aver• for studying the REDOX hydrogen process was de• age metal oxide equilibrium C02/CO ratio of 3.2 (Ta• signed and constructed (Figure 2). Fuel gas is mixed ble 1). with water in the evaporator where it is heated to 400 °C. The humidified fuel gas is then heated in the The modelling predicts that best efficiencies will be furnace to 800 °C before passing through the bed obtained using fuel gas from an indirect gasifier. How• material. After passing through the bed the fuel gas is ever even under ideal conditions an overall biomass to depleted having been oxidized by the bed material. On hydrogen efficiency of 45% should be considered an cooling to 4 °C the water condenses. The gas compo• upper limit. 14 Hydrogen production from REDOX was expensive for • Experimental O Modelled two reasons, high capital cost and low efficiency. ^—Linear (Experimental ) Linear (Modelled) 1 1.5 CCyCO ratio Fig. 3: Effect of the C02/CO ratio on the conversion of fuel gas to hydrogen. 100 1000 Biomass input (MW* HHV) An alternative to REDOX, is to use shift conversion Fig. 4: Hydrogen production cost from REDOX and followed by pressure swing absorption (PSA). PSA is used commercially to produce hydrogen from fossil PSA. fuel gases (natural gas, coal and petroleum). 4 CONCLUSION Biomass gasification >Fuel gas PSA ) Hydrogen Good agreement between modelling and experimental was obtained. The efficiency was shown to be influ• enced by the fuel gas C/F ratio. Further work focused The efficiency of the PSA option was modelled using on optimising the metal oxide C/F ratio and including ASPEN. The modelled efficiency of 60% was signifi• reforming capability are expected to slightly increase cantly higher than the REDOX option. the efficiency. Economic analysis of the REDOX and PSA technology REDOX hydrogen technology faces significant techni• options has been completed. Hydrogen production cal and economic challenges. The efficiency is low costs from REDOX and PSA are shown in Figure 4. and will remain low due to thermodynamic constraints. For REDOX, three scenarios have been considered. REDOX reactors will require exceptionally high capital In the first scenario (REDOX-100%), the capital cost cost. of the REDOX component was calculated assuming 3 5 ACKNOWLEDGEMENTS an optimum energy density of 0.35 MWth/m given by Hacker et.al. [6]. This results in a very high hydrogen The authors would like to thank the following people: production cost. The second scenario (REDOX 50%) Thomas Marti, Peter Hottinger and Peter Binkert. Fi• shows the effect of halving the cost of the REDOX nancial support by the Swiss Office of Energy is grate• component. In the final scenario (REDOX 10%) the fully acknowledged. cost of the REDOX component is reduced to 10%. Even using this extreme scenario the hydrogen pro• 6 REFERENCES duction costs are still at least 70% higher than the PSA option. [1] V. Hacker, G. Faleschini, H. Fuchs, R Fank- hauser, G Simader, M Ghaemi, B Spreitz, K. Frie• Using PSA technology, the equipment needed to con• drich, Usage of biomass gas for fuel cells by the vert fuel gas to hydrogen makes a relatively modest SIR process. Power Sources 71, 226-230(1998). contribution to the total investment [2]. For REDOX the capital costs are much higher because of the low [2] A. Faaij, C. Hamelinck, E. Larson, T. Kreutz, Pro• energy density in the REDOX bed. Data from other duction of methanol and hydrogen from biomass studies using BCL indirect gasification [2] have been via advanced conversion concepts-preliminary re• included for comparison. Reasonable agreement was sults, Biomass for Energy and Industry, 1st World obtained between the PSA options. Conference and Technology Exhibition (2000). 15 METHANE FROM BIOMASS S. Biollaz, S. Stucki The importance of natural gas for the energy supply will increase in the future. New applications for natu• ral gas are in development, i.e. household heating with fuel cells and natural gas as a clean fuel for trans• port. Methane as main part of natural gas can be produced form different sources of biomass. Following an upgrading of the primary gas such renewable gas could be injected into the natural gas grid and be used through a well established infrastructure. This might be a transition step to solar hydrogen. 1 INTRODUCTION ever, it is not specified in the action plan where this There are two high priority goals in energy policy: additional electricity should come from. Offshore wind reducing significantly the consumption of primary en• power might be a primary source for renewable hy• ergy and supplying the remaining energy demand with drogen production. decarbonised fuels. Reviewing the last 100 years It is expected that it takes 10 years and more to build there is already a trend to decarbonised fuels, i.e. up the needed infrastructure for the use of natural from coal to oil and further to natural gas. At the same gas, i.e. fuelling stations and cars running on natural time, systems running with natural gas are more effi• gas. It is also expected that it takes additional 5 years cient and therefore the specific consumption of pri• to build up the infrastructure for hydrogen production, mary energy decreases. The importance of natural etc. gas will therefore further increase within the next dec• ades. 3 METHANE FROM BIOMASS Methane as main part of natural gas is the natural In Europe, the distribution grid for natural gas is per• product of anaerobic biomass decomposition. It is also manently improved as the consumption is increasing. a significant part of the fuel gas from the gasification In addition, new applications for natural gas are in development, i.e. household heating with fuel cells, of hemicellulosic biomasses, i.e. wood. The gas qual• and natural gas as a clean fuel for transportation. In ity can be upgraded with some post-treatment of bio- the car industry most recent developments of power gas and fuel gas, i.e. C02 separation. Such upgraded trains are based on natural gas as primary energy. gas, which is rich in methane and poor in carbon diox• Whether low emission vehicle with synthetic designer ide can be injected into the natural gas grid. Therefore fuels, new generation of CNG cars, or fuel cell car it is compelling to use methane from different sources running with hydrogen: they all depend on natural gas of biomass via a well established infrastructure. as primary energy. Basically all these fuels such as One central question which arises is: How much bio• synthetic designer fuels, methane or hydrogen can be mass is available? To give an answer to that question produced from biomass. a material and energy flow analysis was performed for Switzerland [2]. Several conclusions can be drawn 2 EU ACTION PLAN: ALTERNATIVE AND RE• from that study rsp. confirm well known facts. The NEWABLE FUELS FOR TRANSPORTATION most important use of biomass is for food and fibre. The European commission published recently an ac• Energy from biomass comes primarily from waste tion plan concerning alternative fuel for road transpor• biomass. There are three different biomass types tation [1]. The driving forces for this action plan are: which are most import and might be interesting for improving security of supply and reducing greenhouse methane production: Wood from forestry and wood gas emissions. The objective is a 20% substitution of processing industry, agricultural residuals, manure oil by alternative fuels in the road transport sector by and bio-wastes from household. the year 2020. This objective poses a challenge well As shown in Figure 1 a technical potential of up to 180 beyond what has been asked from the car and oil PJ of primary energy is available [3]. This corresponds industry in the past such as drastic reduction of emis• roughly to 20% of the primary energy demand of Swit• sions of conventional air pollutants. zerland. primary energy [PJ] year biofuels natural gas hydrogen total [%] [%] [%] [%] 2005 2 - - 2 2010 6 2 - 8 2015 (7) 5 2 (14) 2020 (8) 10 5 (23) Table 1: Alternative fuel for road transportation: Op• timistic development scenario [1]. energy residues agricultural household crops from residues, bio-waste Table 1 summarises the EU target for market shares landscape manure of alternative and renewable fuels. In the action plan [HI today • future 0 potential biofuels are understood to originate from agricultural Fig. 1 : Biomass potential in Switzerland as primary products, i.e. ethanol and rape seed oil. Hydrogen is energy [3]. Wood, agricultural residues and household expected to be produced from electric power. How• bio-waste are most important resources. 16 4 METHANE CONVERSION TECHNOLOGY nology" can therefore be considered as a transition technology to hydrogen. Different conversion technologies are needed to con• vert biomass to methane depending on the biomass type. In Figure 2 different routes for the production of 5 OUTLOOK methane from biomass are shown. Biomass such as Independent of the application of the primary energy sludges and bio-waste can be converted to methane "biomass" it must be mentioned that it is a limited via fermentation or hydrothermal gasification. Woody resource. At the same time it is not yet clear today biomass is preferably converted to methane via ther• how much biomass will be available for energy appli• mal gasification and methanation of the fuel gas. cation and for what type of application (fuel, electricity, In Switzerland there are two fermentation technolo• heat). In terms of technology development this implies gies available: KOMPOGAS [4] and 2B [5]. The that key technologies need to be developed which are KOMPOGAS process converts bio-wastes from robust with respect to future decisions. Some of these household to biogas. Typical capacity is 10'000 tons key technologies are: conversion technology for bio• of wet biomass per year which can be treated per mass to gas, i.e. gasification and gas cleaning tech• vessel. The fermentation takes place within thirty nology. days. In addition to the production of biogas, compost is produced. 6 ACKNOWLEDGEMENT The 2B process is a new process specially developed Financial support by novatlantis - sustainability of the for the fermentation of grass. In this process only the ETH domain - is gratefully acknowledged. cell nucleus is fermented. Typical capacity in Switzer• land is 10'OOO to 15'000 tons of wet biomass per year which can be treated. In Europe the capacity would go 7 REFERENCES up to 50'000 ton. The fermentation takes place within [1] COM(2001) 547, Communication on alternative two days. In addition to the biogas production, fibre fuel for road transportation and on a set of meas• and proteins are produced. ures to promote the use of biofuels, Presented by For the conversion of wood to methane some modi• the Commission, Bruessels (2001). fied technologies from coal industry can be used. [2] K. Scheurer und U. Baier, Biogene Güter in der There is one installation operational in USA which Schweiz - Massen- und Energieflüsse, im Auftrag converts lignite coal to methane rsp. SNG (substitute des BfE, Bern (2001) natural gas) [6]. Further developments in conversion technology are needed. Key areas are the biomass [3] J. Hersener und U. Maier, Energetisch nutzbares gasification, gas clean-up and the methanation. One Biomassepotential in der Schweiz sowie Stand of the challenges is the adaption of the coal technol• der Nutzung in ausgewählten EU-Staaten und ogy to biomass. The typical capacity of a wood-to- den USA, im Auftrag des BfE, Bern (1999) methane plant would be probably 40'000 to 360'000 [4] http://www.kompogas.com tons of wood per year. [5] http://www.2bio.ch The basic technology for the production of methane or [6] http://www.dakotagas.com hydrogen from biomass is identical. "Methane tech- Sources of biomass Biomass type Technology Product Fig. 2: Methane production from different biomass. 17 HEAVY METAL EVAPORATION FROM FLY ASH IN INERT AND OXIDIZING ATMOSPHERES H. Lutz, Chr. Ludwig The effect of oxygen (02) on the evaporation behavior of zinc (Zn) from a filter ash of a municipal solid waste incinerator was investigated. Depending on the redox conditions, Zn showed quite a different evaporation behavior. When adding oxygen a shift of the evaporation to lower temperatures was found. Thermodynamic modeling allowed interpreting the evaporation spectra with regard to the volatilized Zn- species. In the absence of oxygen, zinc chloride (ZnCI2) and metallic zinc (Zn°) can evaporate at tempera• tures above 800 °C, whereas in the presence of oxygen onlyZnCI2 evaporates, but already above 700 °C. 1 INTRODUCTION meter (ICP-OES). To obtain different oxygen levels 02 had been mixed to the carrier gas at 0 vol% ("inert"), For a detoxification of filter ash from municipal solid 0.4, 1.5, and 6 vol% ("oxidizing"). The temperature waste incinerators heavy metals need to be removed was raised from 300 °C to 950 °C at a heating rate of to a large degree (often >95 %). 6 °C/min then kept constant at 950 °C until the rate of Such heavy metal removal efficiencies in a thermal evaporation had dropped below a preset threshold process cannot be achieved for all important heavy (Figure 2). This design of the temperature regime was metals (Cd, Cu, Pb, Zn) without adjusting the chemi• not so much chosen in order to achieve maximum cal environment. Parameters, such as current redox- evaporation percentages, but rather to optimise the conditions and the availability of chemical species and study of the chemistry in the given temperature range. reaction partners, influence the reactions in the ash The thermodynamic calculations were made based on during its treatment. Both can easily be adjusted by the composition given for the reference ash BCR176. choosing from a variety of additives such as oxygen Following assumptions apply: C at 1 wt%, [CI] = [K] + (02), carbon (C), and chlorides (Cl-salts). Ideally, [Na]. these transform non-volatile heavy metal species into volatile ones that can leave the ash under the applied physico-chemical conditions. 3 RESULTS At temperatures below 1000°C Zn is least volatile in its oxidic state (ZnO), more volatile when present as 55 100 the pure metal (Zn°) and even more so as chloride (ZnCI2). According exclusively to the above order, the aim of the thermal treatment process would be to transform all present Zn-species into chlorides and 2 40 — — • evaporate them at suitable temperatures. Several o factors complicate the achievement of this aim. Cru• o. 20 — - — - 1 cial are the availability of the necessary species, the 1 1 1 1 1 1 L © 0 -I— —i— —i— —i— avoidance of unwanted reactions as well as the kinetic 0.0% 0.4% 1.5% 6.0% barriers governing the velocity of the reactions under oxygen in carrier gas, % consideration. In this work we present results on the evaporation of Zn from the certified reference ash "BCR176" under Fig. 1 : Evaporation of zinc from BCR176 in 4 differ• conditions with and without oxygen in the inert carrier ent atmospheres (0, 0.4, 1.5, and 6 % 02). The error gas argon (Ar). The experimental results could be bar is about ±5 % Zn. interpreted with the help of thermodynamic modelling calculations. 02 has a marked influence on the percentage of Zn that evaporated during the ash treatment (Figure 1). It 2 EXPERIMENTAL had been expected that the Zn evaporation would The ash investigated, "BCR176" is an official refer• decrease in all "oxidizing" cases due to the formation ence material and was certified by the Community of non-volatile oxidic Zn-species. This expectation is Bureau of Reference in the 1980s. The ash was used met by BCR176: It showed a decrease in evaporation. as received. For every experiment an ash sample with However, the evaporation of Zn is quite independent a weight of 100 mg was placed into an Al203 crucible, of the 3 levels of oxygen added (Figure 1). Also it is which was then inserted into a quartz tube furnace. important to note, that in the presence of 02 the During the experiments the evaporation of Zn was evaporation occurs at a lower temperature (Figure 2). studied by on-line monitoring [1, 2]. For all experi• The overall time of evaporation also shortens favora• ments argon (Ar, 99.998 % purity) was used as carrier bly. The onset of the Zn-evaporation in the cases gas to transport the evaporating Zn to the detector, an "oxidizing" coincides with the onset of the first, tiny Zn- inductively coupled plasma optical emission spectro• peak at minute 80 for the case "inert". 18 1000 900 800 ü 700 O 600 3 +-» 500 400 55 300 Q. 200 E 100 0 17 33 50 67 83 100 117 133 150 167 183 200 217 233 250 267 283 time, min (left: one gridline = 100 °C) Fig 2: Evaporation of zinc for the given temperature profile from the ash BCR176 in 4 different atmospheres (0, 0.4, 1.5, and 6 % 02). The integral beneath the curve is a measure for the absolute amount that evaporated. The amount of ash used was 100 mg, thereof 3.5 mg were Zn. The simultaneous emergence of the peaks indicates present as ZnO. At higher temperatures, gaseous an evaporation of the same Zn-species. But while ZnCI2 is the prominent species. No metallic Zn° can only a tiny amount evaporated from the ash in the be expected according to this thermodynamic model. absence of 02, a large amount got formed and So in the case "inert" two species at higher tempera• evaporated in its presence. It seems that this forma• tures volatilize (ZnCI2 and Zn°), while for "oxidizing" tion occurred at the expense of the larger, second only one species evaporates, but already at lower peak at minute 100 (Figure 2). temperatures (ZnCI2). The second volatile species, By thermodynamic calculations we were able to at• Zn°, is not stable under oxidizing conditions. Lutz et tribute a species to every major Zn-peak. The calcu• al. [3] assumed that the first, tiny peak for the case lations show a pronounced difference in the occur• "inert" mentioned above is ZnCI2 originally present in rence of both volatile and non-volatile Zn-species as the ashes. This fits well the fact that the evaporation soon as oxidizing conditions were applied (Figure 3). experiments with oxygen show the Zn-evaporation to start at just this temperature, the earliest possible for any ZnCI2 to evaporate in the systems given. 4 ACKNOWLEDGEMENTS We express our thanks to A.J. Schüler and T. Figilis- ter for technical assistance, and to R. Struis, S. Stucki, and A. Wokaun for their support and fruitful discussions. The Swiss National Science Foundation financially supported this project (5001-058295). 300 400 500 600 700 800 900 1000 temperature, °C 5 REFERENCES [1] Chr. Ludwig, A.J. Schuler, J. Wochele, S. Stucki, Fig. 3: Calculated equilibrium speciation showing Measuring the evaporation kinetics of heavy the dominant Zn-species for the cases "inert" and metals: a new method, Recovery, Recycling, "oxidizing" along the experimentally investigated Re-integration, 4th world congress, Geneva, temperature gradient. Switzerland (1999). For "inert" the thermodynamically only stable Zn- [2] Chr. Ludwig, A.J. Schuler, J. Wochele, S. Stucki, species up to about 800°C is expected to be ZnS. Measuring heavy metals by quantitative thermal Thereafter, gaseous ZnCI2 is calculated to form at the vaporisation, J. Wat. Sei. Technol., 42:7-8, 209- expense of ZnS. Volatile Zn° is stable at tempera• 216 (2000). tures exceeding 900 °C. [3] H. Lutz, Chr. Ludwig, R. Struis, On-line Monitor• For "oxidizing" on the other hand, ZnO-compounds ing of Heavy Metal Evaporation Using Induc• are thermodynamically stable at temperatures below tively Coupled Plasma Optical Emission Spec• 600 to 700 °C. While ZnO*AI203 and willemite troscopy (ICP-OES), ICP Information Newslet• (Zn2Si04) are present in small amounts, the bulk is ter, 27:3 (2001). 19 STRUCTURE OF ZINC PARTICLES FORMED BY CONDENSATION FOR TRANSPORTATION TO AN ANALYTIC DEVICE T. Barone, J. Wochele, Chr. Ludwig, A.d. Schuler, B. Kelterer Aerosol containing small particles with homogeneous structural characteristics are desired for analysis in Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). To investigate heavy metal evaporation behaviour during thermal treatment a laboratory on-line elemental analyzer has been devel• oped. The analyzer consists of a Condensation Interface (CI) for the generation of aerosols and an ICP- OES as detector. The settings at the CI can strongly influence the particle formation, and therefore the quality of the measurements. To improve the method preliminary experiments were conducted to investi• gate the characteristics of zinc particles formed in the evaporation/condensation process. System condi• tions, such as vaporization temperature, carrier gas, and flow rate, were varied to investigate their influ• ence on particle size, homogeneity and shape. The experiments suggest that particles vary most with temperature, lower vaporization temperatures resulted in the formation of smaller particles. 1 INTRODUCTION Water Online evaporation measurements [1, 2, 3], which Oven Jacket allow to perform thermo-desorption spectroscopy Nebulizer (TDS) are used in different projects to investigate and characterize the heavy metal behaviour during ther• mal treatment of waste, waste residuals, energy car• riers and raw materials [3, 4]. The system consists of a temperature regulated tube reactor, connected to an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) via the CI (condensation interface, Figure 1). In a typical TDS experiment 0.1 to 10 g heterogeneous sample material is heated from 25°C up to 1000°C at a constant rate and the TolCPor evaporated heavy metals are detected on line. In order to improve the analytical method, it is essential Prefilter to better understand the particle formation processes. In this study a simple particle collection method has been tested using elemental Zn as a model com• pound for evaporation. Scanning Electron Micros• Fig. 1 : System for thermo-desorption spectroscopy copy (SEM) was used to characterise particles in with oven, condensation interface and ICP-OES. size, shape and distribution, generated at different Particles formed in the CI are sampled with a mem• temperatures. brane filter for subsequent SEM analysis. 2 PARTICLE FORMATION AND SAMPLING 3 ZINC PARTICLE STRUCTURE Approximately 0.5 g of granular zinc was vaporizied in the tube furnace at temperatures from 350 to 750 Zinc particle structure was investigated using the °C. The vapor was carried by argon at 440 ml/min, to following general operating conditions designed for the CI. Because particles with similar temperature the online detection of metals [1, 2]: carrier gas and time history have similar structural characteris• flowrate, 440ml/min Ar, nebulized water droplets tics [5], the hot metal vapor is quenched in a narrow included in the quench, original injection position of zone. At the CI a water jacket surrounds the tube and cool countercurrent, and vaporization temperature at the hot metal vapor is met by a cool countercurrent of 750°C, between the melting (419°C) and the boiling argon and nebulized water droplets. Water droplets (909°C) point. are included in order that the latent heat of evapora• tion contribute to the cooling and as condensation For a sampling time of 2 min, 2.0 mg of zinc was seeds. Then the metal fume (vapor + particles) exits obtained on a polycarbonate filter. The particles (Fig• the CI and is intended to pass into the ICP-OES for ure 2) appear to be aggregates and clusters (>0.5 analysis. um) composed of primary particles (« 0.5 um). Be• cause the aggregates and clusters overlap in the In order to investigate particle structure, the stream areas observed, their sizes were not discerned. exiting the CI was sampled with a membrane filter. Aggregates differ from clusters in that they are linked Two types of filters were used, cellulose and polycar• in branched chains by the sintering or merging of bonate. Sampling times ranged roughly from 1 to 10 primary particles. The primary particles appear to minutes. Once the particles were collected, the filters have spheroidal and cubic shapes. The particles look were sputtered with a gold/palladium coating in similar in shape to zinc oxide particles published in a preparation for SEM analysis. Random areas of the particle catalogue [6]. However, the zinc oxide parti• filter were observed at magnifications from 66 to cles are described as hexagonal. 20'000. 20 Fig. 2: Zinc particles formed at 750°C. Particles Fig. 3: Zinc particles formed at 550°C. Nanoparticles appear to be aggregates of primary particles. Scale appear faint. Scale 500 nm. 500 nm. 4 EFFECT OF SYSTEM PARAMETERS 5 CONCLUSION System parameters were varied to determine the These preliminary experiments suggest that particles particle change during an intended typical TDS vary considerable during a typical TDS experiment, experiment. Some system parameters investigated at most with temperature. Also a standard procedure were temperature of vaporization, increased carrier for injection position and gas flow should be etab- gas flowrate, absence of water in the quench and lished to control particle structure. To determine if the injection position of the cool countercurrent. results apply to other heavy metals, further experi• ments should be conducted, with real samples, such The most important change resulted from a reduction as incineration residues or batteries. in vaporization temperature from 750°C to 550°C. The fume was sampled for 2 min with a polycarbon• ate filter and 0.2 mg was collected. Small particles 6 ACKNOWLEDGEMENTS were deposited sparsely across the filter. Particles with sizes near 0.5 urn were deposited along the rims We thank S. Pratsinis and K. Wegner (ETH-Zürich) of the pores (Figure 3). Nanoparticles appeared faint for fruitful discussions. This project is financially sup• but could be seen on the filter surface. Large clusters ported by Gebert Ruf Stiftung (Project P-058/00). such as the one shown in the bottom right hand cor• ner of Figure 3 were rare and could have resulted 7 REFERENCES from the reentrainment of particles deposited on the walls back into the gas. Overall, a decreased vapori• [1] Chr. Ludwig, A.J. Schuler, German Patent, zation temperature led to less clustering and hence 198 38 383, (1998). smaller particles. [2] Chr. Ludwig, A.J. Schuler, J. Wochele, S. Stucki, Another adjustment that led to smaller, more homo• Measuring the evaporation kinetics of heavy geneous particles was the movement of the injection metals: a new method, R'99, 4th world congress, position of the cool countercurrent 1 cm in, toward Geneva, Switzerland, 205-210 (1999). the oven. A shorter sampling time was used than in [3] Chr. Ludwig, A.J Schuler, J Wochele, S. Stucki, the aforementioned experiments. After 1 min 0.4 mg Measuring Heavy Metals by Quantitative Ther• was collected on a polycarbonate filter. The amount mal Vaporisation, Journal of Water Science and of aggregates and clusters observed was less than Technology 42:7-8, 209-216 (2000). for the original case but more than that for a lowered vaporization temperature. Primary particles appeared [4] J. Wochele, Chr. Ludwig, A.J. Schuler, A. Krebs, to be 0,5 urn or less and clusters were 2 urn or less. Optimisation of Metal Recycling from Batteries, The shapes of the primary particles were similar to Proceedings of EMC Friedrichshafen (D), 165- those in Figure 2. Further experiments should be 174(2001). conducted to determine if these results apply gener• [5] S.K. Friedlander, Smoke, Dust, and Haze, Ox• ally. ford University Press, New York (2000). Large crystals (1-3 urn) were formed by moving the [6] W.C. McCrone, R.G. Drafty, J.G. Delly. The injection position of the cool counter current 2 cm Particle Atlas, Ann Arbor Sciences Publishers, away from the oven, increasing the flowrate to 600 Ann Arbor, Ml (1980). ml/min and eliminating water from the quench. 21 HEAVY METAL RECOVERY FROM FLY ASH: A Zn K-EDGE EXAFS STUDY R.P.W.J. Struis, Chr. Ludwig, H.Lutz, A. Scheidegger (LES) Fly ash is normally deposited in landfills, as it contains high concentrations of toxic heavy metals, such as Zn, Pb, Cd and Cu, among other elements, like Na, K, Ca, Cl, S, Al, Si, and O. The Laboratory for Energy and Materials Cycles (LEM) studies means to detoxify materials like fly ash by thermal treatment under various gas atmospheres (inert, reducing or oxidising) and/or by adding solid additives to the ash (such as carbon), with the ultimate goal to produce secondary raw materials suited for reprocessing industry. 1 INTRODUCTION mode using ionisation chambers purged with appro• priate inert fill gases. A typical raw spectrum with fly Heating up a sample of fly ash under a flow of Argon ash sample {1} is shown in Figure 2. leads to 3 distinct peaks for the rate of evaporation of Zn species (see Figure 1), as revealed by our on-line detection of heavy metal species with an Inductively 4- — Fly ash sample {1} / T=400 C Coupled Plasma-Optical Emission Spectrometer [1]. 3 O = T-quenched 4 h at 950 C & 3 r-1000 sample for in CO Zn EXAFS O c < S CD c c -800 CD »• CD 3 "T" t—i—i—i—r •o 9.4 9.6 9.8 10 CD 10.2 10.4 10.6 -600 »• Zn K-edge absorption energy [keV] C ^C D Fig. 2: Raw Zn K-edge absorption spectrum. -400 O Data reduction was performed using WinXas vs. 2.0, following standard procedures [3]. The resulting % i i i i i i i i i i r functions as a function of wavelength k (not shown 0 100 200 300 400 500 600 here) were weighted by k3 to account for dampening Time (min) of oscillations with increasing k and Fourier trans• formed to achieve radial structure functions (RSF). A Fig. 1 : Zinc evaporation rate during thermal treat• Bessel function as provided by the WinXas software ment of fly ash under inert flowing conditions. package (smoothing parameter = 4) was used to sup• press artefacts due to finite Fourier filtering range While it is plausible to infer from thermo-dynamical between k = 3.7-12.5 Á'1. data [2] that peak {2} is due to evaporation of "indige• nous" ZnCI2 and peak {6} to evaporation of Zn° (metal• lic zinc), it was not clear what Zn species would 3 RESULTS evaporate at position {4}. Therefore, we prepared Fourier transformation of the spectra yields a RSF, several fly ash samples by temperature quenching at which aids the identification of characteristic frequen• the respective positions {1} to {7}. These and refer• cies resulting from backscattering atoms coordinated ence samples were analysed using EXAFS (Extended with the absorbing Zn atoms. X-ray Absorption Fine Structure) to determine the atomic species neighbouring zinc within the respective samples. 2 EXPERIMENTAL CO The spectra of the fly ash and reference spectra were 0> recorded at the beam line BM1b (Swiss-Norwegian Beam Lines, SNBL) of the European Synchrotron .2 Radiation Facility (ESRF, Grenoble), using a Si(111) channel-cut monochromator. Beam energy was cali• brated by assigning the first inflection point in the K absorption edge of a Zn metal foil to an energy of 9.659 keV. All spectra were obtained at room tem• 0 1 2 3 4 5 6 perature. The spectra of the fly ash samples were (Phase uncorrected) interatomic distance, R [Â] collected in fluorescence mode using a Stern-Heald- type detector (Lytle detector, The EXAFS Co.). The Fig. 3: Radial structure functions (RSF) derived from spectra of the reference samples (ZnCI2, ZnO, ZnS, Zn EXAFS spectra with reference compounds, as Zn2Si04, ZnAI204) were collected in transmission discussed in the text. 22 The RSFs shown in Figure 3 reveal that ZnO, Zn2Si04 tion rate course shown in Figure 1. In sample {7}, the and ZnAI204 are all marked by oxygen as first Zn content (which was 100% at {1}) dropped by ca. neighbouring atom at a typical (phase uncorrected) 70% after 4h at 950°C and consists mainly of zinc radial distance around 1.5 Â. With ZnS, sulphur is alumínate (ZnAI204) and zinc silicate (Zn2Si04). At the positioned around 1.9 Á and with zinc metal foil, the intermediate temperature range between 400 and neighbouring zinc lays at around 2.3 Á. We note that 745°C, ZnS is formed on the cost of both, ZnO and the respective curves also differ substantially at higher Zn2Si04. With ZnO, we note that it is a sulphur scav• interatomic distances, indicating differences in the enger known from hot gas cleaning techniques. higher coordination shells as well. From the EXAFS analysis of the fly ash (see Figure 4) and the reference samples (Figure 3), it became evi• dent that sulphur (contained in the fly ash) competes with "indigenous" chloride to react with ZnO to form solid ZnS, instead of volatile ZnCI2. We note that ZnCI2 itself was not detected, likely due to its high volatility under the given temperature conditions. The formation of Zn-S on the cost of Zn-O is well illus• trated by the rise in the EXAFS intensity for the sam• ples {1} to {4} (viz., T=400->865°C) at the typical Zn-S distance around 2 Á. Zn-0 Zn-S o O O U O U o o Eh Eo o o o CD LO i-^ CO ai O) M toII M II M II Oven temperature Fig. 5: Speciation of Zn compounds residing in the fly ash samples {1}-{7}, as discussed in the text. Conclusions and Outlook: The Zn K-edge EXAFS analysis allowed us to obtain valuable information with respect to the speciation and fate of zinc species re• siding in fly ash during thermal treatment. The EXAFS study underlined the role of indigenous sulphur and its competition with indigenous chloride, shifting the for• mation of volatile ZnCI2 to substantially higher, hence, less desirable temperatures. Among other questions, the chemical form of sulphur in the original fly ash is unresolved yet. It could not be resolved with powder XRD, due to its low content, and necessitates soft X- ray EXAFS analysis. Therefore, the authors would Interatomic distance. R [Â] greatly welcome the implementation of such a beam line facility at PSI's SLS in the near future. Fig. 4: Radial structure functions (RSF) derived from Zn EXAFS spectra with fly ash samples {1}-{7} (bot• 4 ACKNOWLEDGEMENTS tom to top). Acknowledgement to Isabelle Bonhoure (LES), Otto The decomposition of Zn-S (which is likely also in• Haas and Bernard Schnyder (Electro-Chemistry), and duced by a ZnCI2T forming reaction, but at a some• the skilled assistance of the SNBL personnel, particu• what higher temperature than with ZnO) is evidenced larly, W. van Beek and H. Emerich. by the gradual drop in the ZnS intensity going from samples {4} to {6} (viz., T=865->950°C). ZnS is re• 5 REFERENCES moved totally after 4h thermal treatment at 950°C (sample {7}). Speciation of the various zinc com• [1] H. Lutz, Chr. Ludwig, R.P.W.J. Struis, ICP Infor• pounds residing in the respective fly ash samples is mation Newsletter, in press: 27:3 1-7 (2001). feasible by modelling the background corrected and [2] See, e.g., Thermochemical properties of inor• normalized EXAFS spectra with a linear combination ganic substances, O. Knacke, O. Kubaschewski of spectra from different reference spectra. Figure 5 & K. Hesselmann (Eds.), 2nd Ed., Springer, Berlin presents these results multiplied with the Zn fraction in (1991). the respective fly ash samples, which we estimated from the respective area involved in the Zn evapora• [3] T. Ressler, J. Synchr. Rad. 5, 118 (1998). 23 Solar Technology 24 THE HIGH TEMPERATURE SOLAR TECHNOLOGY LABORATORY Robert D. Palumbo Because the sun is a 5800 K energy source, the of the oxidation reaction. S. Kraeupl and Ch. Wieckert thermal energy streaming from it to the earth is of each present papers that investigate solar thermal extremely high quality; it can be used as process en• processes leading to zinc. The process explored by ergy for a large variety of thermal processes. Consider the first author also produces syngas as a solar fuel. for example a process for producing zinc from zinc These papers describe processes that combine fossil oxide. It requires a given amount of energy that can fuels with sunlight, easing the technical difficulties of be calculated from the change in the enthalpy of the separating the metal from the products and easing the products (zinc and oxygen) and the reactant, zinc reactor engineering difficulties, due to required reac• oxide. Nature, however, requires that a large portion tion temperatures near 1600 K rather than 2300 K. D. of this energy be supplied as electric work, if the Hirsch et al. describe solar processes operating at thermal energy source is at ambient temperature. An similar temperatures and leading to hydrogen produc• ambient temperature thermal source simply does not tion via the thermal decarbonisation of fossil fuels. have a high enough quality to effect the desired reac• tion. The same observation can be made with respect Besides using concentrated sunlight for fuel produc• to producing hydrogen from water at room tempera• tion, the laboratory is investigating a number of cur• ture — we need an electrolysis cell to supply most of rent industrial processes for which high temperature the required energy in the form of electric work. But as solar energy can be supplied as process heat in place the temperature of any endothermic decomposition of the current use of fossil fuels. This research repre• process increases more process heat can be substi• sents a path toward reducing industrial C02 emis• tuted in place of electric work. If the temperature of sions. Interfacing the high quality thermal energy from the process for producing zinc were increased to over the sun to a current industrial process is an alternative 2300 K, one could supply all of the required energy as to the "end of the tail pipe " approach of capturing and thermal energy. One can see from these examples then sequestering the C02 in caverns or the ocean. In that as the temperature of a thermal energy source this regard A. Meier et al. describe work on develop• increases, the thermal energy becomes more work ing a solar lime kiln and C. Guesdon et al. describe like in nature. Although one can use solar energy for their research into the solar extraction of metals from space heating and the boiling of water, its industrial their sulfides. potential far exceeds these applications, perhaps be• The work of the laboratory is focused on developing ing in the end only limited by our imagination. industrial scale reactors that enable us to creatively tap into the high quality potential of solar energy. The The work described in this section explores the indus• work is experimental, but strongly supplemented with trial potential of using concentrated sunlight in high numerical modeling efforts. We are learning how to temperature thermal chemical processes. The ther• match the solar flux available at the entrance of a mal decomposition of zinc oxide in fact is one such reactor to the rates of desired chemical reactions so process. At temperatures exceeding 2300 K we pro• that much of the solar energy ends up driving the duce zinc. It can be used as a fuel in a zinc/air fuel chemistry of the reaction. Models are required so that cell for electricity production or for producing hydrogen we can extrapolate small experimental results at a set in a low temperature exothermic reaction with water. of defined operating conditions to large scale reactors The product of the electrochemical or thermal chemi• operating under a variety of conditions. This effort cal reaction is zinc oxide, which can then be recycled requires us to understand the optical properties of our to the solar furnace. This high temperature process reactants and even the construction materials of the thus opens up the possibility of transforming solar reactor. We need the fundamental understanding of energy into a fuel that can be stored and transported. how the sunlight and IR radiation interact with the However, an important technical difficulty is separat• materials inside a reactor. The research described by ing the zinc from the oxygen before they recombine to M. Musella et al. is directed at this goal. give back zinc oxide. Two of the following papers be• gin to address the question as to whether or not the As we look to make our industrial processes more separation will be possible by a rapid cooling process. sustainable, it seems appropriate to investigate using Bodek and Alxneit describe an apparatus that will be sunlight in such away that takes advantage of its used to study the oxidation kinetics of zinc from a thermodynamic potential. The papers that follow rep• fundamental perspective, while Keunecke's paper resent part of the Laboratory's 2001 effort at achieving describes an apparatus for an empirical investigation this goal. 25 REKIN, AN EXPERIMENT TO STUDY THE KINETICS OF THE OXIDATION OF ZINC VAPOR — CONCEPTUAL OVERVIEW AND DESIGN P. Bodek, I. Alxneit An experiment to study the reoxidation kinetics of zinc vapor based on a confined coaxial jet has been developed. Zinc vapor optionally diluted with inert gas is confined in a stream of oxygen also optionally diluted with inert gas at temperatures up to 800°C. The concentration of zinc atoms will be probed spatially resolved by planar laser-induced fluorescence. To extract kinetic data from this information, also the mixing behavior in the confined coaxial jet has to be established beforehand. We present the concept of the experiment and a detailed description of the design. 1 INTRODUCTION 2 CONCEPT One attractive chemical process to produce hydrogen Due to the apparent lack of experimental information using solar energy is by splitting of water. The direct dealing with the reactivity of metal vapors at elevated thermal splitting of water, however, requires ultra high temperatures and under conditions only remotely com• temperatures and an effective technique to separate parable to those to be expected in a solar reactor it hydrogen from oxygen. At 2800 K water is dissociated was decided to make use of the similarity of the oxida• to about 10% at 1 atmosphere. One possibility to cir• tion of metal vapors, i.e. a flame using a metal vapor cumvent problems associated with these facts are as fuel, and that of a hydrocarbon flame. In both cases thermochemical cycles. These cycles separate the information of the rate constant of a highly exothermic formation of oxygen and hydrogen in two distinct reaction taking place at high temperatures and under chemical reactions. At PSI a two-step cycle based on pressures approaching 1 atmosphere or more is of zinc oxide studies for this purpose. In a first solar step interest. The metal vapor flame is implemented as using concentrated solar radiation, zinc oxide is de• confined coaxial jet shown in Figure 1. composed at 2300 K yielding zinc and oxygen. Metallic zinc is collected and reacted with water in a second low-temperature step yielding hydrogen and again zinc oxide. Of prime importance in the process is the sepa• Vacuum Chamber ration of zinc and oxygen avoiding substantial reoxida• tion of zinc. It is evident that the efficiency of the whole process directly depends on the amount of zinc that can be harvested in the solar step. Currently the sepa• ration of zinc and oxygen is implemented as a rapid quench. In order to design an effective quenching device, information on the path of the reaction must be known. Currently it is not clear, whether the reoxida• tion of zinc vapor starts from the gas-phase or only occurs on zinc droplets or crystallites. To answer these questions the kinetics of the oxidation of zinc vapor and, preferentially, of its homogeneous nuclea- tion rate must be known. Only little information is available in the literature about Laser the reaction of metal vapors with oxygen. Kashireninov et al. [1] studied the oxidation of magnesium vapor with oxygen. In their setup a diffusion flame of magne• sium vapor is formed. The temperature distribution Fig. 1 : Concept of Rekin showing the confined coax• and thus the heat released in the flame was deter• ial jet and the probing laser sheet. mined spatially resolved using an array of thermocou• Zinc vapor optionally diluted with inert gas leaves the ples. From this information the rate constant of the central nozzle and is confined in a stream of oxygen reaction Mg + 02 -> MgO(g) + O could be obtained. stemming from the ring-nozzle. The oxygen stream Campbell [2] studied in great details the reaction of can also be optionally diluted with inert gas. A gas transition metal (TM) atoms with oxygen. In his setup heating system will allow preheating the gases to tem• metal-organic precursors are photolyzed in a dilute peratures approaching 1000 K [3]. Therefore it can be stream of oxygen. The disappearance of the metal controlled whether zinc atoms or droplets will take part atoms formed is measured temporally resolved and an in the reaction. Depending on the exact geometry of expression for the second-order rate constant of the the nozzle system a laminar flow or turbulent mixing reaction TM + 02 -> TMO(g) + O is obtained. All these can be realized after the nozzle system. Thus the studies mentioned are performed under conditions situation of a diffusion flame as well as the one ap• that are incompatible with those to be expected at the proaching a premixed flame can be achieved. By exit of a solar reactor and none are dealing with the choosing the appropriate geometry of the nozzle sys• metal of interest zinc. tem the case of a diffusion limited reaction can be 26 largely excluded and measuring the reaction rates to be relatively inert towards zinc vapor. All surfaces becomes possible. that are in contact with oxygen, i.e. the parts forming the annular gap, are gold-plated to avoid corrosion. The concentration of various species (zinc atoms, The source is made from individual parts connected oxygen molecules or intermediates) in the reaction using metal seals. This allows for a smooth replace• zone will be probed spatially resolved by planar laser- ment of parts and an easy change of the exact ge• induced fluorescence (PLIF). In order to extract infor• ometry of the nozzle. Zinc and oxygen streams can be mation about rate constants from the spatially re• individually diluted with hot inert gas. Thus tempera• solved concentration the mixing behavior inside the ture and partial pressure can be individually controlled confined coaxial jet has to be known. This can be in both streams. experimentally determined again by PLIF at room temperature using organic tracers in both streams or An external gas handling system is installed. Mass at high temperature by using NO as tracer. Sampling flow controllers define the flows of the three gas the solid product of the reaction and analyzing its mor• streams as well as the ratio of oxygen to inert gas in phology by electron microscopy will provide additional the oxygen stream. Each of the three streams is then information about the path of the reaction. heated to a defined temperature and connected by heavily insulated tubes to the experiment. A rotary vane pump dynamically evacuates the main tube. 3 DESIGN After leaving the main tube of Rekin the hot gases are cooled and if necessary passed through a particle The main part of Rekin consists of two pieces: A multi- filter. A throttle valve is installed in front of the pump to sectioned tube (25 cm inner diameter) with four win• regulate the flow thus defining the operating pressure dows attached forming a cross (i) and the zinc evapo• of Rekin. We expect to operate the experiment at ration source including the coaxial nozzle (ii) that is pressures slightly below ambient. integrated in a flange to be mounted on top of the tube (i) and pointing downwards. Spacers allow mounting the coaxial nozzle at distances from 0 to 20 cm above 4 ACKNOWLEDGEMENT the cross formed by the four windows Financial support by the Swiss Federal Office of En• ergy (BFE) is gratefully acknowledged. The wall of the large tube (i) is thermally insulated allowing the use of Viton seals to connect individual 5 REFERENCES sections. It also limits the thermal stress on flanges avoiding warping. The wall of the tube is flushed with [1] O.E. Kashireninov, V.A. Kuznetsov, G.B. Manelis, hot inert gas to confine the reaction zone to the Kinetic Study by the Diffusion Flame Method of centerline of the tube and to prevent zinc vapor or the Gas-phase Reaction Between Magnesium solid products to deposit on the observation windows. and Oxygen, Rus. J. Phys. Chem.49, 520 (1975). At the bottom of the tube a water-cooled copper plate is used to collect the solid reaction products for a [2] M.L. Campbell, Temperature Dependent Study of 3 subsequent analysis. the Gas-Phase Kinetics ofZr (a F2) and Hf(a F2), J. Chem. Soc, Farad. Trans. 94, 1687 (1998) In the source part (ii), zinc is evaporated in a graphite and references therein. crucible, heated with Thermocoax heating wires. All other parts are made from ETG-100 steel that proved [3] M. Keunecke, private communication. 27 OPTIMISATION OF THE QUENCH FOR THE SOLAR THERMAL DECOMPOSITION OF ZINC OXIDE M. Keunecke, J. Lédé (LSGC-CNRS-ENSIC, Nancy, France), M. Ferrer (LSGC-CNRS-ENSIC), R. Palumbo, A. Meier The quench of the system Zn/02 after the solar thermal decomposition of zinc oxide is studied in two dif• ferent types of solar reactors. The quench method is a combination of a cold surface and a cold inert gas. Experiments indicate that Zn yields are depending on the site of the cold surface and the ratio between the cold inert gas and the produced zinc. Additionally, the influence of the gas temperature on the zinc yield is analysed. The obtained information will be verified with a laboratory set-up in order to optimise the process parameters of the solar reactor. 1 INTRODUCTION tor. To suppress a premature cooling by the gaseous dilution, the use of preheated carrier gas is consid• For the storage of solar energy, the decomposition of ered. zinc oxide to zinc and oxygen is one of the most prom• ising process options. Concentrated sunlight provides 3 EXPERIMENTAL the process heat for the endothermic zinc oxide disso• The development of an optimised reactor concept for ciation reaction at temperatures around 2000 K. The the production of zinc requires the knowledge of some solar radiation is converted directly into chemical en• constraints: (1) the position and the efficiency of the ergy, and the solar energy stored in the condensed heat exchanger; (2) the level of dilution; and (3) the zinc phase can be used to split water. This leads to a preheating temperature of the carrier gas intended to two-step water-splitting cycle using the Zn/ZnO-redox be mixed with the product species at high tempera• system for the solar production of hydrogen [1]. ture. This information was obtained with two different prototype solar reactors. Both reactors worked in the The most critical step in obtaining high Zn yields within batch mode concerning the solid zinc oxide, which the dissociation reaction of zinc oxide is an effective was pre-sintered before its use to a density of ap• quench of the gaseous products in order to avoid the proximately 4000 kg/m3. One reactor was indirectly recombination of Zn and oxygen. Various quench heated with concentrated sunlight impinging on a methods exist, like a quench by injecting a cold liquid graphite tube. The inner tubular reaction compartment or a cold gas. Another method is using a cold surface was made of Al203; it enclosed the ZnO sample and to condense the products and avoid the re-oxidation. was continuously flooded by an inert gas stream. The We decided to use a combination of two methods; quench section at the exit of the tube consisted of a using a cold surface and diluting the product gas cold finger made of copper. It was intended to receive stream with an inert quench gas. part of the reaction products, and its variable position was an important parameter for the study. 2 THEORETICAL The second reactor (Figure 1) was directly heated with concentrated sunlight entering through a transparent There is still not much information available concern• quartz glass window. ing the recombination reaction of zinc and oxygen. The hypothesis that this reaction is essentially hetero• 5 - Chimney geneous implies some surface for the re-oxidation of zinc to occur. Such surface could be a cold wall, or a droplet of liquid zinc, or particles of either solid zinc or already formed solid zinc oxide. As liquid zinc is known to be more reactive than solid zinc [2], it seems inevitable to find experimental conditions where the fraction of liquid zinc droplets is minimised. Com• pletely avoiding the formation of liquid zinc droplets while cooling down the Zn(g)/02(g) system means operating below the triple point of zinc. However, the low zinc partial pressures below the triple point require extremely high dilutions with the inert gas, thus render• ing the system unattractive for an industrial process [3]. Hence, the solution consists in developing a reactor allowing only negligible amounts of liquid zinc droplets in the carrier gas and keeping Zn in the gaseous state Fig. 1 : Schematic of the directly heated solar reactor until its arrival in the quench section of the solar reac• used to study the quench of zinc and oxygen [4]. 28 This non-cavity reactor was insulated inside with a The percentage of Zn in all the products recovered at heat resistant AI2O3/SÍO2 material. Gas streams at various places throughout the quench zone is nearly various places were needed to guarantee a clean 80%. It is found that the metallic zinc yields are de• window and the quench of the gaseous products [4]. pending on the distance between the dissociation site The 15 kWth solar reactor also included an electrical and the quench site, i.e. the location of the cold sur• gas heating system for preheating the inert gas. Addi• face and the location of the cold inert gas jet. tionally, a copper heat exchanger served as the cold quench surface. It was located at the exit of the reac• 5 OUTLOOK tor chamber (Figure 1) close to the dissociation site, but not exposed to the sunlight. Due to the complexity of the above-described solar reactors and the large number of variables in real The oxygen content in the product gas stream was solar experiments, it has been decided to further simu• measured with gas chromatography; X-ray diffraction late the dissociation of zinc oxide in a much simpler analysis was used to determine the zinc yields at vari• laboratory set-up. This concept includes well-known ous sites of the cold surface. fluid dynamics and allows easy modelling to get more insight into the Zn/02 recombination reaction. In 4 RESULTS particular, the influence on the back reaction of both the dilution with the carrier and quench gas and its Several solar experiments were performed in the PSI temperature can be investigated under highly solar furnace with both the indirectly and directly reproducible conditions. heated reactors. In general, the results confirm the findings of previous experimental studies [3] that the With this approach, fundamental information about ratio between the carrier gas and the produced zinc is reaction mechanisms and kinetic data for the oxidation influencing the zinc yields for constant reaction rates. of zinc is expected in order to determine the appropri• Moreover, experimental data for various dilution ratios ate process parameters for an effective quench of the and different reaction rates suggest that the zinc yields Zn/02 system. are not only depending on the dilution ratio with an inert quench gas, but also on the inert gas tempera• 6 ACKNOWLEDGEMENT ture (Figure 2). Initial results indicate that Zn yields are near zero when the inert gas (argon) temperature is This work is being funded by the Swiss Federal Office below 900 K. The Zn yields are as high as 16% above of Energy (BFE). this temperature. 7 REFERENCES [1] A. Steinfeld, P. Kuhn, A. Relier, R. Palumbo, J. 0.2 i Murray, Y. Tamura, Solar Processed Metals as Clean Energy Carriers and Water Splitters, Int. J. 0.16 - Hydrogen Energy 23, 767 (1998). [2] A. Weidenkaff, A. Steinfeld, A. Wokaun, P.O. I 0.12- c Auer, B. Eichler, A. Relier, Direct Solar Thermal N c Dissociation of Zinc Oxide: Condensation and "fi 0.08- Crystallisation of Zinc in the Presence of Oxygen c • Solar Energy 65, 59 (1999). 0.04 - . [3] R. Palumbo, J. Lédé, O. Boutin, E. Elorza Ricart, • • • A. Steinfeld, S. Möller, A. Weidenkaff, E.A. 0 -I • # •—* 1 1 Fletcher, J. Bielicki, The Production of Zn from 400 600 800 1000 1200 1400 ZnO in a High Temperature Solar Decomposition Inert gas temperature [K] Quench process - I. The scientific framework for the process, Chem. Eng. Sei. 14, 2503 (1998). [4] S. Möller, R. Palumbo, Solar thermal decomposi• Fig. 2: Zn yield (ratio of mol Zn to mol ZnO decom• tion kinetics of ZnO in the temperature range posed) at different inert gas temperatures. 1950-2400K, Chem. Eng. Sei. 56, 1 (2001). 29 SPECTRAL REFLECTIVITY OF Fe203 AND NiO AT HIGH TEMPERATURE M. Musella An apparatus for measuring the directional-hemispherical spectral reflectivity of materials up to high tem• peratures has been built at PSI. For characterising the instrument, reflectivity measurements on Fe203 and NiO were carried out in the range 510-860 nm at temperatures up to 1200 K. The reproducibility of the measured data was better than 1.5 %. The standard deviation, calculated for experiments carried out on different samples, varies with the material used and, in general, depends on wavelengths and tempera• ture. 1 INTRODUCTION For the experiments the sample is placed in the inte• grating sphere and white light is focused on its sur• Radiative properties of materials play an important face. The light reflected from the sample is detected role in technical applications at high temperatures. by an ICCD camera. The same procedure is applied to Being necessary for temperature measurements, heat a reference target of known reflectivity and the un• transfer and energy balance calculations, they are a known sample reflectivity is obtained by comparing the key parameter in solar technology. In spite of their two detected fluxes [1]. The use of the ICCD allows importance however, only a few data exist in literature. the simultaneous measurement of the reflectivity in a In order to provide this information, an apparatus for large, continuous wavelength range (presently 510- measuring the spectral reflectivity of condensed sam• 860 nm). ples in the visible and near infrared range at high tem• peratures has been developed in our laboratory. To 3 RESULTS assess the performance of the apparatus, experi• ments have been carried out on materials for which Fe203 powder (pressed at 57% theoretical density) literature data exist and that are of interest for the was studied in vacuum at temperatures up to 1200 K. laboratory. Results obtained on Fe203 and NiO are Figure 2 shows the measured reflectivity. The values reported here. reported are averages obtained from various experi• ments carried out with different samples. The calcu• lated standard deviation, g, depends on wavelength 2 EXPERIMENTAL and temperature, its average being approximately 4%. The method used for measuring the directional- Measurements carried out on the same sample show hemispherical spectral reflectivity is based on the inte• a reproducibility better than 1.5 %. grating sphere technique, where a comparative proce• dure is used. A scheme of the apparatus is shown in Figure 1. 0.35- 0.30- 0.25- _> "•5 0.20- o o oc 0.15- 0.10- 0.05- —I— —I— —I— —I— —I— —I— —I— —I 500 550 600 650 700 750 800 850 900 Wavelength, nm Fig. 2: Reflectivity of Fe203 as a function of tempera• ture. The slight peak around 600 nm is an artefact due to a notch filter placed in front of the detection system. Fig. 1 : Schematic of the apparatus for reflectivity measurements. S sample mounted on an electrical In Figure 3, the experimental values at room tempera• resistance; R reference; M routable manipulator; F ture are compared with literature data. The results are optical fibre; IW cooling water inlet; OW cooling water in good agreement in the range 600-750 nm while for outlet; P vacuum pump; V vacuum chamber; W white lower and higher wavelengths the literature values are light, C monitoring camera; L heating laser (not used systematically lower. Because the tendency and the here). shape of the curves is the same, the difference in the 30 absolute values is attributed to the different morphol• for Fe203. In Figure 5, the experimental values at ogy of the samples used in the experiments. room temperature are compared with literature data. 0.45- .... _b 0.40- 0.35- 0.30- S 0.25 • U O <¡¡ 0.15- 'S 0.20- OC 0.15- 0.10- 1—I—1—I—1—I—1—I—1—I—1—I—1—I—1—I—1—I 0.05- —I— 1— —I— 1— —I— —I— —I —I— —I 450 500 550 600 650 700 750 800 850 900 500 550 600 650 700 750 800 850 900 Wavelength, nm Wavelength, nm Fig. 3: Reflectivity of Fe203 at room temperature: a. Fig. 5: Reflectivity of NiO at room temperature: a. this this work; b. this work 66% confidence interval; c. Ref. work b. this work 66% confidence interval; c. Ref. 2 2 curve 3; d. Ref. 2 curve 5. curve 14; d. Ref. 2 curve 23; e. Ref. 2 curve 19. NiO pressed powder aliquots were sintered at 1573 K The agreement is excellent for values above 650 nm for 3 hours in air. After the treatment the samples, while a systematic deviation is observed at lower having 64% theoretical density, showed a greenish wavelengths. Again the discrepancy is attributed to the colour. Figure 4 shows the measured reflectivities different morphology of the studied samples. obtained as averages from different experiments. 4 CONCLUSION Measurements confirm that reflectivity data can be obtained with high reproducibility from 500 to 800 nm at temperatures up to 1200 K. The influence of sample morphology was found to be of great importance and further investigation is needed. 5 ACKNOWLEDGEMENTS I would like to thank I. Alxneit and H.R. Tschudi for their suggestions and helpful discussions. Continuous 0.05 H 1 1 1 1 r" 1 1 1 1 1 1 1 1 1 1 1 support from the Swiss Federal Office of Energy is 450 500 550 600 650 700 750 800 850 900 Wavelength, nm gratefully acknowledged. Fig. 4: Reflectivity of NiO as a function of tempera• 6 REFERENCES ture. [1] I. Alxneit, S. Eckhoff, M. Schubneil, H.R. Tschudi, The calculated standard deviation, a, varies between 4 Measurement of the Hemispherical Emissivity in and 6 % for all the temperatures and wavelengths, the Visible Region at High Temperatures sup• except for room temperature above 800 nm where it ported by Laser Heating, Proceedings of the rises to 14 %. The high value obtained at room tem• ISES 1999 Solar World Congress, Jerusalem, Is• perature is probably due the fact that a has been cal• rael (1999). culated as average of samples presenting surfaces with a slightly different state of oxidation, and therefore [2] Y.S. Touloukian and D.P. DeWitt, Thermal Radia• different optical properties. At higher temperatures, tive Properties, Thermophysical Properties of where the stoichiometry gets more uniform, the stan• Matter Non metallic solids, Vol. 7 (IFI/Plenum, dard deviation decreases to the same value obtained New York, Washington 1970). 31 TOWARDS THE INDUSTRIAL SOLAR PRODUCTION OF LIME A.Meier, E. Bonaldi (OualiCal AG), G.M. Celia (QualiCal AG), W. Lipinski, R. Palumbo, A. Steinfeld (ETH Zürich and PSI), C. Wieckert, D. Wuillemin A new industrial concept that aims at the development of the chemical engineering technology for the solar production of lime is being examined. To establish the technical feasibility, a 10 kW solar reactor has been designed, constructed, and experimentally tested at a high-flux solar furnace. The quality of the produced solar lime meets industrial standards. 1 INTRODUCTION stone material is introduced into the hot furnace with• out preheating the limestone particles. Substituting concentrated solar energy for carbona• ceous fuels, as the source of high-temperature proc• In solar simulator experiments at ETH Zurich [7], the ess heat for the thermal decomposition of limestone concentrated radiant energy from a high-pressure (CaC03) to produce lime (CaO), is a means to elimi• argon arc lamp was used to directly irradiate a thin nate the dependence on conventional energy re• layer of limestone particles (about 10 g of CaC03) on sources and to reduce emissions of C02 and other a SiC plate. pollutants. Solar processing offers a clean and sus• Solar furnace experiments were conducted at PSI to tainable path for reaching these goals, and the indus• establish the technical feasibility of a 10 kW solar re• trial solar lime project with QualiCal AG [1] is a pio• actor (Figure 1). This novel reactor consists of a hori• neering attempt to address this challenge. zontal rotary kiln with an innovative particle feeding The specific purpose of the project is to establish the system for continuous operation (mean CaO produc• technical and economic feasibility of a 0.5 MW thermal tion rate 10-30 g min"1). The reaction chamber is lined input solar calcination plant for the production of lime, with a refractory concrete and well insulated with a e.g. as building material in a developing world setting porous ceramic fibre, both allowing for temperatures or for high quality applications in the chemical industry. up to 1600°C. The current work is based on the experience from previous studies showing that CaC03 can be calcined with concentrated sunlight and that a high degree of chemical conversion can be achieved [2-5]. Further• more, an internal study done at PSI along with several leading players in the cement industry concluded that solar calcination is a feasible process [6]. 2 EXPERIMENTAL The raw material used for testing the new concept for the solar calcination process was extremely pure Carrara marble (CaC03 content close to 98%). We examined different particle size fractions in the range of 1-5 mm that cannot be treated by current industrial technologies for calcination, since they either use grain sizes below 1 mm (flash calciners or fluidised bed reactors), or above about 10 mm (rotary kilns), or Fig. 1: Test of the 10 kW solar lime prototype reactor even above 40 mm (vertical shaft kilns). in a solar furnace at PSI. Thermogravimetric measurements were conducted at 3 RESULTS AND DISCUSSION temperatures up to 1200°C with 400 mg samples for different purge gas compositions (pure air and a mix• Kinetic parameters obtained from thermogravimetric measurements suggest that complete calcination of 2- ture of N2 with varying C02 content). 3 mm limestone particles can be attained within less Electric furnace experiments were performed accord• than 2 minutes at 1050°C and only 4 seconds at ing to the following procedure that was chosen to 1350°C. The kinetic parameters, however, may be simulate the conditions in a solar furnace, where the influenced by the sample weight, the shape of the burning temperature is expected to be reached almost crucibles, and the heating rate [8,9]. For increasing instantaneously: (1) the electric furnace is heated to C02 content in the gas phase, the calcination pro• the chosen temperature between 850°C and 1340°C; ceeds at significantly higher temperatures, thus show• (2) the cold quartz crucible containing 30 g of lime• ing the need for fast C02 removal. Both electric furnace and solar simulator experiments strated. The quality of the produced solar lime meets indicate that the necessary retention time is in the industrial standards. range of 3-7 minutes to ensure complete calcination of A numerical reactor model is being developed to as• the 2-3 mm limestone particles at temperatures above sist in the modification and optimisation of the current 1100 °C. The retention time for the calcination is solar reactor and eventually in the conceptual design strongly related to the burning temperature, the grain and economic analysis of a large-scale solar lime size, the void distribution within the sample, and the plant. thickness of the particle bed. Moreover, the elevated C02 partial pressure within the closed electric furnace 5 ACKNOWLEDGEMENT may hamper the CaC03 decomposition reaction, thus explaining in part the discrepancy to the thermogra- We thank the Swiss Federal Office of Energy (BFE) vimetric measurements. for funding this work. The results of the solar experimental campaign con• 6 REFERENCES firm that lime with a degree of calcination exceeding 98% (Figure 2) and virtually any quality ranging from [1] The Solar Production of Lime, 2000 - 2003 Re• low to high reactivity can be produced in the solar search Program: www.qualical.com/solar (2001). reactor. The operating temperature and the reactants' residence time are found to be the two most critical [2] G. Flamant, D. Hernandez, C. Bonet, J.-P. Trav• parameters. The thermal efficiency, defined as the erse, Experimental Aspects of the Thermochemi- ratio of process heat used for the chemical reaction to cal Conversion of Solar Energy; Decarbonation of the solar power input, reaches 10-15% for this non- CaCÖ3, Solar Energy 24, 385 (1980). optimised solar reactor prototype, indicating the poten• [3] J. M. Badie, C. Boner, M. Faure, G. Flamant, R. tial for developing an efficient and cost effective solar Foro, D. Hernandez, Decarbonation of Calcite industrial calcination process. and Phosphate in Solar Chemical Reactors, Chem. Eng. Sei. 35, 413 (1980). [4] O. A. Salman, N. Kraishi, Thermal decomposition of limestone and gypsum by solar energy, Solar Energy 41, 305 (1988). [5] A. Steinfeld, A. Imhof, D. Mischler, Experimental Investigation of an Atmospheric-Open Cyclone Solar Reactor for Solid Gas Thermochemical Reactions, J. of Solar Energy Eng. 114, 171 (1992). [6] A. Imhof, Internal reports from 3 PSI / Industrial Workshops, Oct. 1996, June & July 1997. [7] Professorship in Renewable Energy Carriers at the Institute of Energy Technology, ETH Zurich, 80% -I , , 1 0.0 10.0 20.0 30.0 Internet address: http://www.pre.ethz.ch (2001). Mean Production Rate (g/min) [8] M. Maciejewski, A. Relier, How (unreliable are kinetic data of reversible solid-state decomposi• Fig. 2: Degree of calcination for a variety of solar tion processes ?, Thermochimica Acta 110, 145 experiments with specific operating conditions de• (1987). pending on temperature, rotational speed of reactor, reactants feeding rate, product discharging system, [9] A. Romero Salvador, E. Garcia Calvo, C. and particle size (2-3 mm). Beneitez Aparicio, Effects of sample weight, par• ticle size, purge gas and crystalline structure on 4 CONCLUSION AND OUTLOOK the observed kinetic parameters of calcium car• bonate decomposition, Thermochimica Acta 143, The solar calcination of very pure limestone particles 339 (1989). in the range of 2-3 mm has been successfully demon• 33 OPERATIONAL PERFORMANCE OF A 5 kW SOLAR CHEMICAL REACTOR FOR THE CO-PRODUCTION OF ZINC AND SYNGAS S. Kräupl, A. Steinfeld (ETH Zürich and PSI) We report on the operational performance of a 5 kW solar chemical reactor for the combined ZnO- reduction and CH4-reforming "SynMet" process. The reactor features a pulsed vortex flow of CH4 laden with ZnO particles, which is confined to a cavity-receiver and directly exposed to solar power fluxes ex• ceeding 2000 kW/m2. Reactants were continuously fed at ambient temperature, heated by direct irradia• tion to above 1350 K, and converted to Zn(g) and syngas during mean residence times of 10 seconds. Typical chemical conversion attained at the reactor outlet was 100% to Zn and up to 70% to syngas. The thermal efficiency was in the 15-22% range. The experimental results indicate that the solar chemical re• actor technology can be further up-scaled and developed for an industrial application. 1 INTRODUCTION 2 REACTOR DESIGN The solar chemical reactor technology for the Figure 2 shows schematically the SynMet-reactor. It "SynMef'-process, i.e. the solar co-production of zinc consists of a 240 mm-length 110 mm-diameter cylin• and synthesis gas (syngas) by the combined drical cavity that contains a 6 cm-diameter windowed reduction of ZnO and reforming of CH4, is being aperture to let in concentrated solar energy. The developed for converting solar energy into storable quartz window is cooled and protected from condens• and transportable fuels [1]. The overall reaction can able gases by an auxiliary gas flow. Both reactants be represented by: CH4 and ZnO are fed at ambient temperature. ZnO powder (mean particle size = 0.4 urn) is continuously ZnO + CH4 -» Zn +2H2 + CO fed axially while CH4 is simultaneously pulse-injected tangentially, creating a stoichiometric gas-particle The produced Zn can be stored and transported. On helical stream that absorbs efficiently the incoming demand, it can be used either for direct electricity solar irradiation. The mean residence time of reac• generation or for H2 production. The chemical product tants inside the reaction chamber is 10 seconds. The is ZnO, which is recycled to the solar reactor. The reaction products (Zn vapor and syngas) exit through thermochemical cycle is depicted in Figure 1. a water-cooled Pyrex tube where part of the zinc con• denses. Particle filters collect the remainder solid products downstream. The gaseous products are analyzed on-line by gas chromatography while repre• sentative solid product samples are analyzed by x-ray diffraction. Solar power input and power flux intensi• ties through the reactor's aperture were measured optically using a calibrated CCD camera aimed at an AI203-coated Lambertian target. product access for outlet . thermocouples Fig. 1 : Storage and transport of solar energy via the SynMet process. In previous papers we examined the chemical ther• modynamics and kinetics of the SynMet process [1,2], performed a life cycle assessment and economic analysis [3], and described the engineering design, fabrication, and experimental investigation of a 5 kW prototype solar reactor for effecting the reaction using concentrated solar energy [4-6]. In the present note we report on recent experimental results of the test campaign conducted at PSI's high-flux solar furnace Fig. 2: Scheme of the improved SynMet solar chemi• during summer 2001 [7]. cal reactor [6]. 34 3 EXPERIMENTAL • pulsed feeding * pulsed feeding + pipe We report on eight solar runs, grouped in three cate• 4 fixed bed gories: 1) Run I used a fixed-bed of ZnO subjected to 22% a continuous flow of CH4 that was injected via a pipe O positioned under the bed; 2) Runs ll-VI used the con• c tinuous axial feeding of ZnO and pulsed tangential 96% at 1676 K. Typical H2:CO and C02:CO molar Fig. 4: Variation of the thermal efficiency as a func• ratios in the syngas were 1.5-3 and 0.08-0.25, respec• tion of the nominal reactor temperature. tively. 4 CONCLUSION Figure 3 shows the complete energy balance for each experimental run, indicated in percent of the solar A vortex ZnO-CH4 flow solar reactor for co-producing power input. The conduction heat loses through the Zn and syngas was tested in the temperature range reactor walls (outlet, rear, front and cylinder) vary 1406-1676 K and for an input solar power between between 20-26 % and re-radiation losses through the 3.6 and 5.7 kW. The reactor and peripheral compo• aperture vary between 20-30 %. The power used for nents, including the quartz window at the reactor's heating the reactants and for driving the chemical aperture, performed trouble-free under approximate reaction was between 15-22 % of the solar input. steady state conditions. High chemical yields and reasonable energy conversion efficiencies were ob• fixed pulsed pulsed + pipe tained. The experimental results indicate that the solar feeding feeding „ 100 chemical reactor technology can be further up-scaled and developed for an industrial application of ZnO- reduction combined with the reforming of natural gas or other hydrocarbons. - 70- 5 ACKNOWLEDGEMENTS Financial support by the BFE-Swiss Federal Office of Energy and The Baugarten Foundation is gratefully J= 30- acknowledged. c 6 REFERENCES LU [1] A. Steinfeld, A. Frei, P. Kuhn, D. Wuillemin, Int. J. Input solar I V VI VII VIII Hydrogen Energy, 20 793-804 (1995). power [kW] 5.4 5.7 3.7 3.6 4.1 [2] A. Steinfeld, C. Larson, R. Palumbo, M. Foley, Energy 21, 205-222 (1996). Fig. 3: Energy balance for each solar run [7]. [3] M. Werder, A. Steinfeld, Energy 25, 395-409 The thermal efficiency is defined as (2000). AHl1 [4] A. Steinfeld, M. Brack, A. Meier, A. Weidenkaff, reac tanta @ 298 K-> products @ Trta thermal D. Wuillemin, Energy 23, 803-814 (1998). Qsolar,input [5] S. Kräupl, A. Steinfeld, J. Solar Energy Engineer• where Qsoiar is the solar energy input and AH° the ing 123, 733-737(2001). standard enthalpy change of the reaction when the [6] S. Kräupl, A. Steinfeld, J. Solar Energy Engineer• reactants are fed at 298 K and the products are ob• ing 123, 237-243 (2001). tained at Treactor. r/thermai obtained in solar experimental runs at approximately steady-state conditions is plot• [7] S. Kräupl, A. Steinfeld, J. Solar Energy Engineer• ted in Figure 4 as a function of Treactor. ing, submitted (2001). 35 HYDROGEN PRODUCTION VIA THE SOLAR THERMAL DECARBONIZATION OF FOSSIL FUELS D. Hirsch (ETH Zürich), P. von Zedtwitz (ETHZ), A. Steinfeld (ETHZ and PSI) Two hybrid solar/fossil-fuel endothermic processes, in which fossil fuels are used exclusively as the chemical source for H2 production, and solar energy as the source of high-temperature process heat, are considered: 1) the solar thermal decomposition of natural gas; and 2) the solar steam gasification of coal. These processes offer viable and efficient routes for fossil fuel decarbonization and C02 avoidance. The advantages of the solar-driven process are three-fold: a) the discharge of pollutants is avoided; b) the gaseous products are not contaminated; and c) the calorific value of the fuel is upgraded. 1 INTRODUCTION gen-rich gas phase. The carbonaceous solid product can either be sequestered or used as material com• The conversion of solar energy into chemical energy modities under less severe C02 restraints. They can carriers, i.e. solar fuels (e.g. solar H2), which can be also be used as reducing agents in metallurgical long-term stored and long-range transported, over• processes. The hydrogen-rich gas mixture can be comes the major drawbacks of solar energy, namely: further processed to high-purity hydrogen that is not being a diluted, intermittent, and unequally distributed contaminated with carbon oxides and can be used in energy source [1]. fuel cells without inhibiting platinum-made electrodes. The substitution of fossil fuels with solar fuels is a H2-rich mixtures can also be adjusted to yield high- long-term goal requiring the development of novel quality syngas. technologies. Strategically, it is desirable to consider mid-term goals aiming at the development of hybrid The steam-reforming/gasification of natural gas, oil, solar/fossil-fuel endothermic processes in which fossil coal, and other hydrocarbons can be represented by fuels are used exclusively as chemical reactants and the simplified reaction: solar energy as the source of process heat. The prod• ucts of such hybrid processes are cleaner fuels whose CxHy + xH20 : fy \ H 2 + xCO (2) quality has been solar-upgraded: their calorific value — + X is increased by the solar input in an amount equal to Other compounds may also be formed, especially with the enthalpy change of the reaction. The mix of fossil coal, but some impurities contained in the raw materi• fuels and solar energy creates a link between today's als are cleaned out prior to the decarbonization proc• fossil-fuel-based technology and tomorrow's solar ess. The principal product is syngas of different H2:CO chemical technology. It also builds bridges between molar ratios. The CO content in the syngas can be present and future energy economies because of the shifted to H2 via the catalytic water-gas shift reaction, potential of solar energy to become a viable economic and the product C02 can be separated from H2 using, path once the cost of energy will account for the envi• for example, the pressure swing adsorption technique. ronmental externalities from burning fossil fuels. The transition from fossil fuels to solar fuels can occur Reactions (1) and (2) proceed endothermically in the smoothly, and the lead-time for transferring important 800-1500 K range. Several chemical aspects of these solar technology to industry can be reduced. reactions have already been studied [2, and literature cited therein]. Some of these processes are currently 2 DECARBONIZATION OF FOSSIL FUELS practiced at an industrial scale, but the energy re• quired for heating the reactants and for the heat of the An important category of thermochemical processes reaction is supplied by burning a significant portion of for mixing fossil fuels and solar energy is the decar• the feedstock. Internal combustion results in the con• bonization of fossil fuels, i.e. the removal of carbon tamination of the gaseous products while external from fossil fuels prior to their use for power genera• combustion results in a lower thermal efficiency be• tion. Two methods are considered: the solar thermal cause of the irreversibilities associated with indirect decomposition and the steam-reforming/gasification. heat transfer. Alternatively, using solar energy for Both methods make use of high-temperature solar process heat offers several advantages: 1) the dis• process heat for driving the endothermic transforma• charge of pollutants is avoided; 2) the gaseous prod• tions. ucts are not contaminated; and 3) the calorific value of the fuel is upgraded by adding solar energy in an The thermal decomposition of natural gas, oil, coal amount equal to the AH of the reaction. Furthermore, (pyrolysis), and other hydrocarbons can be repre• by directly irradiating the reactants, solar energy can sented by the simplified reaction: be efficiently transferred to the reaction site, bypass• ing the limitations imposed by heat exchangers. CxHy=xC(gr)++-H2 (1) Other compounds may also be formed, depending on The two solar thermal decarbonization methods are the reaction kinetics and on the presence of impurities schematically shown in Figure 1 in the form of simpli• in the raw materials. The thermal decomposition fied process flow diagrams. The two methods have yields a carbon-rich condensed phase and a hydro• been compared [3], focusing on thermodynamics and 36 exergy efficiency. From the point of view of carbon essed, e.g. about 890 kJ-mole'1 for natural gas, and sequestration, it is easier to separate, handle, trans• 35,700 kJ-kg"1 for anthracite coal. Exergy efficiencies port and store solid carbon than it is C02. Also, the are carried out for a blackbody solar cavity- steam-reforming/gasification method requires addi• receiver/reactor operated at 1350-1500 K and sub• tional steps for shifting CO and for separating C02, jected to a mean solar flux concentration ratio in the while the thermal decomposition accomplishes the range of 1000-2000. removal and separation of carbon in a single step. In For route Nr. 1 aimed at H2 generation from natural contrast, the major drawback of the thermal decom• position method is the energy lost associated with the gas, the exergy efficiency amounts to 30%. This route sequestration of carbon. The thermal decomposition offers zero C02 emissions as a result of carbon se• may be the preferred option for natural gas and other questration. However, the energy penalty for com• pletely avoiding C02 amounts to 30% of the electrical hydrocarbons with high H2/C ratio. But for coal and other solid carbonaceous materials, the residual of output, vis-à-vis the direct use of CH4 for fuelling a energy upon decarbonization may be too low for an 55%-efficient combined Brayton-Rankine cycle. industrial application. Instead, the gasification of coal Higher exergy efficiencies (exceeding 65%) could be via reaction (2) has the additional advantage of con• obtained when the carbon is either steam-gasified to verting a relatively dirty solid fuel, which is traditionally syngas in a solar gasification process and the syngas used to generate electricity in 35%-efficient Rankine further processed to H2, or used as a reducing agent cycles, into a cleaner fluid fuel (cleaner only when of ZnO in a solar carbothermal process for producing using solar process heat) that can be used in highly Zn and CO that are further converted via water- efficient Brayton-Rankine combined cycles and fuel splitting and water-shifting to H2. Any of these two cells. alternative solar processes yield 2 additional moles of H2 per mole C(gr) and offer a net gain of 40% in the electrical output (and, consequently, an equal percent reduction in the corresponding specific C02 emis• H.-rich Gas sions), as compared to the conventional combined cycle power generation. (Natural Gas, Oil) C(gr>rich Solid For route Nr. 2 aimed at H2 generation from coal, the exergy efficiency amounts to 56%. This route offers a net gain in the electrical output by a factor varying in the range 1.8-2.2 (depending on the coal type), vis-à- vis the direct use of coal for fuelling a 35%-efficient Rankine cycle. Specific C02 emissions amount to HJC02 0.44-0.52 kg C02/kWhe, about half as much as the (Coal, NG, Oil) specific emissions discharged by conventional coal- fired power plants. Fig. 1 : Simplified process flow diagram for the solar 4 CONCLUSION thermal decarbonization of fossil fuels. Two methods are considered: (a) the solar thermal decomposition; There is a pressing need to develop greenhouse gas (b) the solar thermal steam-reforming/gasification. mitigation options that can be applied to fossil fuels in Omitted is the formation of by-products derived from the mid-term. The proposed solar/fossil fuel hybrid impurities present in the feedstock. chemical processes conserve fossil fuels and reduce emissions. It further converts solar energy into a stor- 3 EXERGY EFFICIENCY AND C02 MITIGATION able and transportable chemical fuel. The fossil and POTENTIAL solar energy mix could substantially reduce C02 emissions and become an important intermediate The following routes for H2 and power generation are solution towards a sustainable energy supply system. examined: a) The solar thermal decomposition of natural gas 5 ACKNOWLEDGEMENTS followed by carbon sequestration and H2 use in a This work is supported by the ETH-Project Nr. TH- 70%-efficient H2/02 fuel cell; 29799-4 and by the BFE-Swiss Federal Office of En• b) The steam gasification of coal followed by syngas ergy Project "Clean Energy Technologies for C02 processing to H2 (by water-shift gas reaction and Mitigation". H2/C02 separation), which is used to fuel a 70%- efficient fuel cell. 6 REFERENCES The exergy efficiency for each of these open-cycle [1] A. Steinfeld, R. Palumbo, Solar Thermochemical routes is defined as the ratio of the work output by the Process Technology, Encyclopedia of Physical fuel cell to the total thermal energy input by solar and by the heating value of the reactants: Science and Technology, Academic Press, 237- 256 (2001). Work Output 3 [2] D. Hirsch, M. Epstein, A. Steinfeld, Int. J. Hydro• 'I exergy n HHV v ) ^ solar "•" ' reac tan t gen Energy 26, 1023-1033 (2001). where QS0|ar is the solar energy input and HHVreactant is [3] M. Steinberg, Int. J. Hydrogen Energy 24, 771- the high heating value of the fossil fuel being proc• 777 (1999). 37 SOLAR THERMAL EXTRACTION OF COPPER AND ZINC FROM SULFIDES C. Guesdon, M. Sturzenegger A novel approach for extracting metals from metal sulfides is proposed. Key feature is the use of concen• trated solar radiation to directly convert metal sulfides into the metal and sulfur. Such processes have the potential to produce metals with virtually zero emission of S02 and C02. The feasibility of such a solar thermal extraction has been evaluated for zinc sulfide (ZnS) and copper(l)sulfide Cu2S. Thermodynamic calculations suggest that for both processes heat recovery from the hot product is required to implement a viable process. Decomposition experiments have indicated that the high reactivity ofZn and S is not com• patible with the energy requirement of heat recovery and that quenching will likely be needed to collect Zn. As an alternative, the addition of a mixture of 02 and steam (chemical quenching) is discussed. The ex• traction of Cu from Cu2S appears less critical: Experiments under N2 revealed the formation of metallic Cu already at 1323 K. Natural separation of gaseous S from liquid Cu successfully prevents recombination of the two products and at least partial heat recovery can be envisaged. 1 INTRODUCTION furnaces. To explore the feasibility of direct reduction of metal sulfides under concentrated solar radiation, a Most of the commercially important non-ferrous met• study on the decomposition of synthetic ZnS and als such as copper, zinc, nickel or lead are mined as Cu2S was initiated. sulfides. Carbothermic processes as they were im• plemented e.g. for the extraction of iron from iron ox• ide can not be applied, since carbon-sulfur com• 2 DECOMPOSITION OF ZINC SULFIDE pounds are not stable enough to drive the reaction of The energetics of the decomposition of ZnS is illus• metal sulfide with carbon. Therefore, conventional trated by means of the enthalpy-entropy- (Mollier-) extraction processes include roasting to convert the diagram. Mollier diagrams contain the enthalpy as metal sulfide into the corresponding metal oxide, and variable. Thus, enthalpy differences can be immedi• as a second step the extraction of the metal from the ately read from the diagram. For reversible processes metal oxide. This production scheme implicates two the slope of the curves represent the equilibrium tem• serious disadvantages [1]: Firstly, roasting of the sul• perature. Figure 1 shows that the decomposition of fides liberates corrosive and toxic sulfur dioxide (S02). solid ZnS into gaseous zinc Zn(g) and sulfur S2(g) is Reaction 1 describes the roasting of zinc sulfide endothermic by 396 kJ/mol. The equilibrium tempera• (ZnS). Although S02 is nowadays often used for on- ture was calculated to be 1824 K. From Figure 1 one site production of sulfuric acid, emission of S02 still can appreciate that the moderate equilibrium tempera• causes severe damages to the local environment. ture is mainly due to the high reaction entropy which Secondly, metal extraction from the relatively stable results from the formation of gaseous products. For• intermediate metal oxide by either a pyrometallurgical mation of gaseous products on the other hand ac• or an electrolytic process produces vast amounts of counts for 50% of the reaction enthalpy. This figure C02. In the former process carbonaceous materials suggests that heat recovery from the hot products is are added as combustible and as reducing agent, in strongly desirable for implementing a viable produc• the latter, electricity generation is the source for C02 tion of solar Zn from ZnS. emission. 3 ZnS + /2 02 -> ZnO + S02 AH° = -441 kJ/mol (1 ) Zn(g) + 0.5 Si ZnS -> Zn + S AH" = 202 kJ/mol (2) 200 The decreasing demand for sulfuric acid and attempts 2 Cu(s) + S(s) v" 100 2 to reduce C0 emissions stimulated research activi• •J 2 Cu(l) + 0.5 S2(g) ties aiming at direct conversion of sulfides to the metal Zn(s) + S(s) and elementary sulfur. Direct conversion provides two benefits: i) S02 emission will be avoided and elemen• tary sulfur can be stored for later usage or deposition -100 and ii) the total energy demand for the metal extrac• Cu2S(s) tion will be lower, since the energy-intense reduction -200 of the intermediate metal oxide is avoided. Reaction 2 ZnS(s) exemplifies the decomposition of ZnS into Zn and S. Even though research resulted in valuable process 0 100 200 300 1 1 adaptations, direct conversion of sulfides into metal Entropy [J mol" K"] and sulfur is still an unresolved problem. Fig. 1 : Enthalpy-Entropy diagram for the decomposi• tion of ZnS (dotted line) and Cu2S (dashed line). A promising approach to realize direct conversion is the use of concentrated solar radiation. Thermo• Experimental studies on the decomposition of ZnS dynamic analyses indicated that many sulfides de• were initiated with experiments in a tube furnace inter• compose to the metal and sulfur under inert atmos• faced to a quench unit under nominally inert atmos• 2 pheres at temperatures between 1500 and 2500 K. phere (p(02) < 8-10 mbar). At temperatures up to Such temperatures are readily accessible in solar 1800 K no metallic Zn but ZnS was found on the cool 38 finger of the quench unit. These results indicate that 3 DECOMPOSITION OF COPPER SULFIDE recombination of Zn and S is probably as difficult to The situation looks different for copper sulfide (Cu2S). suppress as the oxidation of Zn vapour in the pres• The direct solarthermal decomposition of Cu2S is pro• ence of 02 and that rigorous measures will be needed mising from the viewpoint of avoiding both S02 and to prevent recombination. C02. Because Cu is more noble than Zn, less energy While physical quenching represents the only means is needed for decomposing Cu2S into molten copper Cu(l) and gaseous sulfur S2(g) than for decomposing to avoid oxidation of Zn by 02, alternative routes can be envisioned for the system Zn-S: ZnS. Although there is no evaporation of Cu, heat stored in the hot products accounts for 50% of the ZnS + 02 -> Zn + S02 T>Tn (3) total reaction enthalpy and heat recovery appears desirable. Unlike recombination of Zn and S, recombi• 2 Zn + S02 -> 2 ZnO + S T S02 is formed at temperatures above a minimum occur naturally in the course of the reaction. Experi• working temperature Tmin and with stoichiometric 2 ments under an inert gas flow (p(02) < 8-10' mbar) amounts of 02 (see reaction 3). Below Tmin reaction 4 produced Cu at temperatures as low as 1323 K. proceeds to the right and undesired ZnO besides S is formed. However, we expect that the reaction of Zn 4 SUMMARY AND CONCLUSION with the relatively stable S02 is slow enough such that Direct reduction of metal sulfides produces the metal Zn can be cooled to room temperature and collected and elementary sulfur. When concentrated solar with good yields even at moderate cooling rates. Re• radiation is used to effect the reduction, processes combination of Zn with S can also be suppressed by with virtually no emission of S02 and C02 can be envi• the addition of steam. We expect an endothermic sioned. Therefore, a benefit for the local environment reaction, with S02 and H2 being the products. By us• and the global climate is expected. ing concentrated solar radiation as heat source this Preliminary studies on the decomposition of ZnS indi• reaction combines the extraction of zinc with the solar cated that strong measures, e.g. fast cooling, will be production of hydrogen. Thermodynamic calculations needed to prevent the products Zn and S from react• show that the addition of steam as quenching agent ing after they will have left a solar reactor. To estimate decreases the minimum working temperature and the the cooling rates, data on the chemical kinetics are amount of the side-product ZnO. The reaction how• needed. These studies are scheduled as soon as the ever suffers from low yields. Only 5 mol-% of the experiment for studying the oxidation of Zn by 02 will added water react with ZnS to form Zn, S02 and H2. be available (see Ref. [2]). An alternative approach to prevent recombination is the addition of an 02/steam ZnS+1.4 H,O+0.7 O, 1800 mixture. Such a process can not reduce the S02 emis• sion but allows an autothermal extraction of Zn with 1600 no C02 emissions. a 1.5 Decomposition of Cu2S appears easier to realize. 1400 Metallic Cu was obtained already at 1323 K and natu• ing S02 and C02 emissions. 0.0 i , • — This report focussed on ZnS and Cu2S. However, the 0.0 o!l 0.2 0^3 OA 0.5 0.6 0.7 0.8 0.9 1.0 above made considerations are not limited to these ZnS + O. ZnS + 2 H20 compounds and further investigations will include any metal sulfide of technical relevance. Fig. 2: Calculated equilibrium composition for the 5 ACKNOWLEDGEMENT system ZnS + 2x H20 + (1-x) 02 at the minimum We would like to thank A. Frei and Th. Frey for ex• working temperature Tmin at atmospheric pressure. perimental support. Continuous financial support from Compounds with concentrations less than 0.03 mol the Swiss Federal Office of Energy is gratefully ac• (S, H2S) and ZnS were omitted for clarity. knowledged. An interesting feature was observed when ZnS was 6 REFERENCES reacted with mixtures of 02 and steam. At a composi• [1] B. Mishra, Proceedings of Sessions and Sympo• tion of 0.7 02 and 1.4 H20 the reaction enthalpy is sia sponsored by the Extraction and Processing close to zero. Division of The Minerals, Metals & Materials So• ciety, TMS, San Diego, California (1999). In summary, chemical quenching allows for direct extraction of Zn from ZnS. Although the approach [2] P. Bodek, I. Alxneit, Rekln, An Experiment to Study the Kinetics of the Oxidation of Zinc Vapor, does not reduce the S02 emission, it offers a path for an autothermal process for direct extraction of Zn from PSI«Scientific Report 2001/Volume V, Paul Scherrer Institut, Villigen PSI (2002). ZnS with zero C02 emission. 39 THE SOLZINC-PROJECT FOR UP-SCALING THE SOLAR CHEMICAL TECHNOLOGY FOR PRODUCING ZINC AS A SOLAR FUEL C. Wieckert, R. Palumbo, M. Epstein (Weizmann Institute, Israel), G. Olalde (CNRS-IMP), H.-J. Pauling (ChemTEK), J.F. Robert (CNRS-IMP), S. Santén (ScanArc), A. Steinfeld (ETH Zürich and PSI) A joint European research project by six partners, PSI (CH), ETHZ (CH), CNRS (F), WIS (IL), ChemTEK (D), and ScanArc (S), has been successfully negotiated with the European Community. The project, called "SOLZINC", aims at scaling-up the chemical reactor technology of the most promising process for the solar production of Zn by carbothermic reduction ofZnO. Furthermore, the ZnO-Zn cyclic process encom• passing the Zn-production solar plant combined with a Zn-air fuel cell will be developed to deliver solar electricity independent of location and time. 1 INTRODUCTION Partner Location/Country Main task (partners are active in further tasks) Intermittent solar energy can be converted into a stor- CNRS-IMP Odeillo/ France Administrative coordination, able and transportable fuel via the production of Zn thermal and energetic diag• from ZnO using concentrated solar radiation as the nostic source of high-temperature process heat [1]. The en• PSI Villigen/Switzerland Scientific coordination, solar reactor design, buildup, test ergy content of zinc can be recovered as electricity in ETHZ Zurich/Switzerland Solar reactor modeling and 70% efficient zinc-air fuel cells [2]. Zinc can also be optimization: solar simulator reacted with water in an exothermic reaction for pro• WIS Rehovot/ Balance of plant for pilot ducing high-purity hydrogen for H2-02 PEM fuel cells Israel Infrastructure: 1 MW beam [3]. In both power generating routes, the chemical down solar concentrator Zn-condensation (operation product is ZnO, which is recycled to the solar reactor. ScanArc Hofors/Sweden limits, pilot plant) Thus, Zn serves as the chemical energy carrier for ChemTEK Oberderdingen/ Zn-air fuel cell optimisation storing and transporting solar energy. Germany Treatment of spent cell products prior to reuse in The thermal dissociation of ZnO requires operating solar plant temperatures above about 2000 K. The use of carbo• naceous materials as reducing agents (e.g. coal, Table 1: The SOLZINC Consortium: two industrial coke, biomass, or natural gas) allows operation at partners (ScanArc, ChemTEK) and four research insti• much more moderate temperatures, in the range of tutes (PSI, ETHZ, CNRS, WIS). 1300-1600 K, but at the expense of releasing C02. If biomass is used as a reductant, the process has zero 2 PROJECT OBJECTIVES net C02 emissions. Nevertheless, compared to the The key objective of SOLZINC is to develop and to conventional fossil-fuel-based production of Zn, the experimentally evaluate a solar carbothermic ZnO- solar-driven carbothermic processes can reduce C02 reduction process at the solar power input level of emissions by a factor of 5 to 10. Furthermore, their about 0.5 MW. In addition, the project includes the development can profit from the traditional pyro- investigation of the material cyclic process and the metallurgical know-how. interface of Zn-air fuel cells with the solar process. (Figure 1). The stoichiometric carbothermic reduction of ZnO, using either C or CH4 as reducing agents, can be represented by the overall net chemical reactions: ZnO + C -> Zn(g) + CO (1) ZnO + CH4 -> Zn(g) + CO + 2H2 (2) Quench/Zn- Zn Zn-Anode Condensation Under-stoichiometric feeding of reducing agents Preparation would be more advantageous [4], but is more difficult to realize. These reactions have been successfully Preparation ZnO ^ Zinc-Air demonstrated in small-scale (5 kW) solar reactor pro• for Solar Reactor Fuel Gel! totypes [5]. A joint international research project with participation of 4 research laboratories and 2 industrial Zn-stream (Zn), in situ gleefftofry ¡zz& Zn/ZnO-stream (Zn/ZnO) potentially partners has been defined to perform the logical next including storage and/or transport Distributed Electric step in the solar chemical technology development, Other stream, in situ Power Supply Vehicles i.e. scale-up to a pilot plant. The project is partially financed by the European Community, with the Swiss contribution being funded by the BBW - Swiss Federal Fig. 1 : Material cyclic process for solar electricity Office for Education and Science. The SOLZINC Con• generation, using Zn as the solar fuel. sortium is listed in Table 1. 40 3 PROJECT METHODOLOGY AND WORK PLAN * Sun SOLZINC started in December 2001. The 4-years work plan consists of three major phases: Phase 1: Optimization on 5kW scale (year 1). Based on all available previous experience, the solar reduction technology that is most promising for scaling up to commercial size will be selected. Three reactor concepts are considered for this evaluation, all of which have already been tested on a 5kW scale: (a) a tubular reactor [6] for reaction (1), (b) a rotating hearth reactor originally designed for Electric Arc Furnace Dust treatment [7], which has been tested at PSI for reaction (1) in autumn 2001, (c) the Synmet-reactor [5] for reaction (2). PSI is in charge of the optimisation of the chosen reactor concept. The testing will be Heliostat Field performed in ETHZ's High-Flux Solar Simulator. In parallel, ScanArc will perform experimental evalua• tion on Zn-condensation techniques for addressing Fig.2: Scheme of the solar concentrating optical the re-oxidation issue of the off-gases exiting the solar configuration chosen for the SOLZINC-technology [8]. reactor. ChemTEK will work on the optimisation of the Zn-air cells for the specific goals of SOLZINC (e.g. 5 ACKNOWLEDGEMENT optimisation for maximal efficiency rather than maxi• mal power) and for solving the interface problems Funding by the BFE - Swiss Federal Office of Energy, (e.g. separation and reuse of KOH-electrolyte from the the BBW - Swiss Federal Office of Science and Edu• Zn-air fuel cell). cation, and the European Community's Research Directorate is gratefully acknowledged. Phase 2: Design and test in pilot scale (years 2-3). It will be based on the small-scale reactor optimisation 6 REFERENCES and will be assisted by detailed process modelling, performed by ETH. Design and build-up of the solar [1] A. Steinfeld, R. Palumbo, Solar Thermochemical reactor for the pilot plant will be mainly carried out by Process Technology, Encyclopedia of Physical PSI. ScanArc will realize the corresponding Zn- Science and Technology 15, 237 (2001). condensation unit. The diagnostic instrumentation equipment will be provided by the CNRS group in [2] lliev, A. Kaisheva, Z. Stoynov, H. J. Pauling, Me• Odeillo. ChemTEK will build and operate a 10 kW Zn- chanically Rechargeable Zinc-Air Cells, Battery- air cell module. The solar pilot plant will then be Recycling "97, Noordwijk (Netherland) July 1-4, erected and tested in the existing solar concentrating 1997. facility of the Weizmann Institute of Science (WIS), in [3] A. Berman, M. Epstein, The Kinetics of Hydrogen Israel. Figure 2 shows the set-up for a beam-down optical configuration, which allows operation of the Zn- in the Oxidation of Liquid Zinc with Water Vapor, plant on the ground [8]. Two extensive solar test cam• Int. J. Hydrogen Energy 25, 957 (2000). paigns are scheduled. [4] C. Wieckert, A. Steinfeld, Solar Thermal Reduction of ZnO using CH4:ZnO and C:ZnO Phase 3: Conceptual design of a demo unit (year 4). Molar Ratios less than 1, J. Solar Energy Engi• The results from the first two project phases will be neering, in press 2001. used to perform detailed design studies for the com• [5] S. Kräupl, A. Steinfeld, Experimental Investiga• plete solar to electricity cycle process, including eco- tion of a Vortex-Flow Solar Chemical Reactor for efficiency studies for different scenarios of technology implementation, such as electricity generation for the Combined ZnO-Reduction and CH4- peak demand, different consumer locations, etc. Reforming, J. Solar Energy Engineering 123, 237 (2001). 4 CONCLUSION [6] A. Steinfeld, M. Epstein, Light Years ahead, The SOLZINC-project marks a milestone in solar Chemistry in Britain 7, 30 (2001). chemistry R&D for storing and transporting solar en• [7] Swiss Patent Application Nr. 1240/01 (2001). ergy. A successful up-scaling of the solar production of zinc will provide the basis for a sound judgment of [8] A. Yogev, A. Kribus, M. Epstein, A. Kogan, Solar the potential implementation of this novel, sustainable, „Tower reflector" Systems: A New Approach for and clean electricity generation technology for sta• High-Temperature Solar Plants, Int. J. Hydrogen tionary and mobile applications. Energy 23, 239(1998). 41 PROGRESS IN THE DEVELOPMENT OF SMALL THERMOPHOTOVOLTAIC PROTOTYPE SYSTEMS W. Durisch, B. Bitnar, J.-C. Mayor, F. von Roth, H. Sigg, H.-R. Tschudi, G. Palfinger In GAZ D'AUJOURD'HUI N° 2(2000)21-24, we reported on a small grid-connected thermophotovoltaic sys• tem consisting of an ytterbia mantle emitter and monocrystalline silicon solar cells. This system produced an electrical output of 18 W, which corresponds to a thermal-to-electric conversion efficiency of 1.3 %. In the interim, progress has been made and efficiencies up to 2.4 % were achieved. To realize self-powered operation of the system, an electronic control was developed. Excess power is fed into the local 230 V utility grid. 1 INTRODUCTION avoid oxidation of the burner tube, it was replaced by heat-resistant metallic rod, on which the emitter was Thermophotovoltaic (TPV) devices convert radiant fixed. Larger reflectors were used to reduce axial ra• heat directly into electrical power. Integrating this prin• diation losses. Finally, smaller high-efficiency Si-cells ciple into residential heating systems opens a large were used to reduce series resistance losses and potential for combined heat and power generation. enhance the electrical output. The new prototype is Part of the electrical power can be used to realize self- shown in Figure 1. powered operation of the heating systems. Such sys• tems would continue to operate during grid failures (blackouts). Excess power can be fed into the house- grid to supply appliances, and/or placed to the utility- grid for external consumers. 2 AIMS OF THE PROJECT • Investigate influence of different components and configurations on electrical output • Improve system design and enhance device effi• ciency • Provide experimental data for modelling of larger systems • Demonstrate feasibility of continuous stand-alone operation • Demonstrate self-powered and/or grid-connected operation 3 TEST SET-UP Commercial butane burners with a nominal thermal output of 0.5 to 2 kW were used to develop small TPV prototypes. Butane and air are premixed and blown into the combustion space surrounded by a porous incandescent mantle made from ytterbia, Yb203. The hot mantle emits radiation, which is converted to elec• Fig. 1: Thermophotovoltaic prototype system. A cy• trical power by means of crystalline silicon photocells. lindrical ytterbia emitter is placed in the centre of a To obtain the electrical data of the cells under actual photocell generator. A glass tube between emitter and operating conditions, a specially developed current- photocells protects the cells against flue gases. The voltage (l/V) meas-uring system was applied. system produces about 50 W(e). 4 IMPORTANT STEPS 5 RESULTS A suitable glass tube between emitter and cells, pro• At a thermal input power of 1985 W an electric output tecting the cells against exhaust gases, replaced the of 47.9 W was attained, corresponding to a system infrared radiation absorbing water filter used in first efficiency of 2.4 %. Short circuit current and open cir• prototypes. Cell cooling was improved to reduce the cuit voltage were measured to be 4 A and 16 V (all temperature of the cells and to increase their conver• cells in series), respectively. Using tap water of 14°C sion efficiency. The shape of the ceramic emitter was the cell temperature was kept at approximately 25°C. changed to quasi-cylindrical geometry, in order to ob• Efficiencies of silicon cell-based TPV-systems found in tain a more homogeneous irradiation of the cells. To the literature do not exceed the value of 2%. 42 43 Combustion Research 44 COMBUSTION RESEARCH LABORATORY Konstantinos Boulouchos The Combustion Research Laboratory (CRL) at the the most prominent examples. Besides direct financial General Energy Research Department (ENE) of the support from industry, the Swiss Federal Office of Paul Scherrer Institut (PSI) focuses its research activi• Energy (BFE), the "Commission for Technology and ties first, on the in-depth understanding of fundamental Innovation" (KTI) and European Research Programs phenomena in reacting flows and here in particular on provide significant funding. turbulence-thermochemistry interactions and second, Research highlights in Year 2001 include: on transfer of insight from basic research to industrial applications with, as an ultimate goal, the realization of the successful evaluation (based on detailed (Near) Zero-Emission, energy-efficient combustion simulation and optical diag-nostics) of turbulent systems. models appropriate for the description of trans• port phenomena in reactive flows in the promixity Research at CRL/PSI is carried out in close coopera• of catalytic surfaces tion with the Laboratory of I.C. Engines and Combus• tion Technology LW at ETH; the two laboratories form the visualization of the NOx-distribution (in addi• a "Joint Combustion Research Program", exploiting tion to the OH-detection) by means of LI F as a thereby synergies and complementary competencies. function of mixture stoichiometry and pressure in Within the CRL the following groups are active in dif• aero-dynamically stabilized lean, turbulent pre- ferent fields of basic research. mixed flames of CH4 in air the identification of key intermediate components Combustion chemistry, comprising two directions for the suppression of soot-precursor formation of research in steady, high-pressure combustion, with oxygenated fuels in diffusion flames and the namely lean-premixed, turbulent combustion and measurement of soot volume fraction and particle catalytically supported laminar and turbulent size evolution in laminar diffusion flames as a combustion. Direct Numerical Simulation of Re• function of fuel chemical structure acting Flows is an additional research activity with long term potential. progress achieved in identifying flame structure and mixture formation features, of relevance to Reaction analysis, focusing on the characteriza• thermoacustic instabilities in turbulent lean pre- tion of molecular dynamics (up to the femtosec• mixed flames. In addition, first qualitative valida• onds range), with emphasis on the identification tion of DNS results, concerning the transition of key molecules and dominant reaction paths in from flat diffusion to premixed edge flames in the complex chemical systems. opposed-jet configuration Combustion diagnostics, aiming at developing the development and implementation of new and improving laser-based, mostly spectroscopic catalysts for SCR-based NOx-removal in an in• diagnostic techniques for temperature measure• dustrial heavy duty diesel engine for meeting fu• ment and species detection in "hostile" combus• ture emission standards; in this context also iden• tion environments. tification of the key-role that N02 plays in the Exhaust gas aftertreatment, dealing mainly with "fast-SCR" mechanism at low temperatures. SCR-deNOx processes and emphasis on low- Strategic priorities in future research at CRL refer to temperature catalytic processes, whereby soot soot suppression and/or removal in diffusion flames/ oxidation comes increasingly into focus as well. diesel engines on one hand and to optimization of Several industrial cooperations exist, among which combustion in gas turbines and gas engines on the projects with ALSTOM Baden/CH (Combustion diag• other. CH4 is strategically viewed as the ideal transi• nostics, gas turbine combustion) and LIEBHERR (de• tional fuel from higher hydrocarbons towards hydrogen velopment and implementation of deNOx catalysts) are in the decades to come. 45 HOMOGENEOUS IGNITION IN HIGH-PRESSURE COMBUSTION OF METHANE/AIR OVER PLATINUM M. Reinke, I. Mantzaras, R. Schaeren, R. Bombach, W. Kreutner, A. Inauen The gas-phase ignition of fuel-lean methane/air premixtures over Pt was investigated experimentally and numerically at pressures of up to 10 bar in laminar channel flow configurations with main objective to vali• date the applicability of various hetero/homogeneous chemical reaction schemes. At pressures of up to 6 bar, the measured and predicted (using the Deutschmann/Warnatz reaction schemes) homogeneous igni• tion distances were in good agreement with each other, whereas at pressures greater or equal to 8 bar a marked overprediction of the homogeneous ignition distances was evident ( > 25%). The Deutsch- mann/GRI-3.0 reaction schemes underpredicted substantially (-55-65%) the homogeneous ignition dis• tances at all pressures, clearly showing the inapplicability of GRI-3.0 under catalytically stabilized combus• tion (CST) relevant conditions. 1 INTRODUCTION Methane is the main fuel component of small-scale power systems (e.g. gas turbines) operating on Cata• lytically Stabilized Combustion (CST) and the under• standing of its heterogeneous kinetics on pre• cious-metal surfaces has progressed significantly the last years [1]. Complementing the purely heterogene• ous kinetic studies, we have recently validated com• bined hetero/homogeneous chemical reaction schemes of CHVair CST over Pt [2] at atmospheric- pressure. High-pressure operation, typical to many practical systems, exacerbates the potential of homo• geneous ignition due to the enhanced reactivity of hydrocarbons with increasing pressure [3]. The pre• sent study undertakes an experimental and numerical investigation of high-pressure CHVair CST over Pt, in laminar channel flow configurations, with main objec• tive to validate the CST-applicability of various het• ero/homogeneous reaction schemes. Fig. 1 : Schematic of the high-pressure catalytic com• 2 EXPERIMENTAL bustion test-rig and the OH PLIF set-up. All distances are in mm. The channel-flow reactor consisted of two Pt-coated horizontal ceramic plates (300mm long, 104mm wide, placed 7mm apart) and two quartz windows positioned the homogeneous ignition distances (x¡g). The agree• at the 300mm x 7mm reactor sides (see Figure 1); the ment between measured and predicted homogeneous reactor itself was positioned inside a high-pressure ignition distances was, irrespective of equivalence vessel. Planar laser induced fluorescence (PLIF) of ratio (ç), particularly good (within -10%) at pressures the OH radical monitored the onset of homogeneous of up to 6 bar. At even higher pressures, the devia• ignition and thermocouples embedded beneath the tions became larger ( > 25%, cases 6, 7). In case 5 catalyst provided the surface temperature. the predictions did not capture the formation of a V-shaped flame. Figure 3 illustrates the computed average (over the transverse direction) mole fractions 3 NUMERICAL of CH4, CO, OH, the fractional CH4 conversions, and Numerical predictions were carried out with a 2-D the measured wall temperature profiles. The homoge• elliptic code [2], using the elementary heterogeneous neous ignition locations shown in Figure 2 corre• scheme of Deutschmann [1] and two elementary sponded to the rise of the OH profiles of Figure 3. The gas-phase schemes: Warnatz [4] and GRI-3.0 [5] CH4 consumption was accompanied by the build-up of respectively. CO (see Figure 3); in cases 1 and 4 both CH4 and CO were consumed shortly after homogeneous ignition, 4 RESULTS AND DISCUSSION with practically no CH4 or unburned CO escaping at the channel exit. In case 7 (10 bar) of Figure 2, the Comparisons between measured and predicted numerical predictions indicated a weak ignition occur• (Deutschmann/Warnatz schemes) distributions of the ring -50% farther downstream of the measured loca• OH radical are illustrated in Figure 2;thearrows denote tion; moreover, the in-channel flame residence time 46 homogeneous ignition characteristics at pressures of up to 6 bar. The homogeneous scheme of GRI-3.0 was shown to be inapplicable under CST conditions. 1.0 1500 case 1 Tw ___—; 0.8 1300 0.6 4 1100 tí£V XoH-5x10 5CH4 •15 0.4 900 0.2 700 0.0 : • ~r • • . in• 500 _. case 4 Twj_^.—; —:r-^-_¿. ^£2 0.8 1300 f 0.6 S o t3 u as 0.4 I _ o 0.2 O m 0.0 _ ._ 0.8 rr 0.6 0.4 0.2 0.0 Fig. 2: PLIF-measured (1a-7a) and predicted (1b-7b) OH concentrations (ppm vol.). The predictions refer to the Deutschmann/Warnatz hetero/homogeneous Fig. 3: Computed average (over the channel trans• chemical reaction schemes. verse direction) species mole fractions (CH4: dashed-double dotted, CO: dotted, and OH: solid), fractional CH4 conversion (dashed-dotted lines), and was not sufficient, so that considerable amounts of measured wall temperature (dashed lines): The case unburned CO exited the reactor (1050 ppm vol.). This notation is the same as in Figure 2. All computations was even more pronounced in the predictions of refer to the hetero/homogeneous schemes of case 5, which did not capture the formation of a DeutschmannA/Varnatz. The predicted homogeneous V-shaped flame; large amounts of CH4 and CO exited ignition distances are shown by the vertical arrows. the reactor (e.g. 8% unburned CH4 and 3650 ppm vol. CO). The foregoing exemplified the importance of the hybrid CST combustion approach, since the heteroge• 6 ACKNOWLEDGEMENTS neous pathway itself -without a subsequent Support was provided by the Swiss Federal Office of post-catalyst flame- cannot provide complete CO Energy (BFE) and Alstom Power of Switzerland. burnout. The important conclusion reached from the comparisons of Figs. 2 and 3 is the validation of the Deutschmann/Warnatz schemes at pressures of up to 7 REFERENCES 6 bar, a range of interest to micro-turbine applications. Predictions with the Deutschmann/GRI-3.0 schemes [1] O. Deutschmann, L.I. Maier, U. Riedel, A.H. (not shown) underpredicted homogeneous ignition Stroemman and R.W. Dibble, Catalysis Today substantially (by -55-65%). The reason was the much 59:141 (2000). faster radical pool build-up of GRI-3.0: over the entire [2] U. Dogwiler, J. Mantzaras, P. Benz, B. Kaeppeli, pre-ignition zone, the OH, O and H radical concentra• R. Bombach and A. Arnold, Proc. Comb. Inst. tions were in GRI-3.0 at least 3 times higher than 27:2275 (1998). those of Warnatz's scheme. Therefore, GRI-3.0 has strong deficiencies at CST-relevant conditions. It is [3] I. Glassman, Combustion, Third Edition, Aca• clarified that the heterogeneous pathway cannot be demic Press, London, 1996, p. 156 held responsible for the performance of GRI-3.0, for [4] J. Warnatz and U. Maas, Technische Verbren• reasons similar to those stated in our earlier H2/air nung, Springer-Verlag, 1993, p. 102. CST work [6] (weak coupling of heterogeneous and homogeneous pathways under mass-transport-limited [5] GRI-3.0, Gas Research Institute, conditions). http://www.me.berkeley.edu/gri_mech, 1999. [6] C. Appel, J. Mantzaras, R. Schaeren, R. Bom• 5 CONCLUSION bach, A. Inauen, B. Kaeppeli, B. Hemmerling, and The hetero/homogeneous chemical recation schemes A. Stampanoni, A., accepted, Combustion and of Deutschmann/Warnatz reproduced the measured Flame, 2001. 47 AN EXPERIMENTAL AND NUMERICAL INVESTIGATION OF TURBULENT CATALYTICALLY STABILIZED CHANNEL FLOW COMBUSTION C. Appel, I. Mantzaras, R. Schaeren, R. Bombach, A. Inauen The turbulent catalytically stabilized combustion (CST) of hydrogen/air mixtures over Pt was investigated experimentally and numerically in channel-flow configurations. Three different low-Reynolds number near-wall turbulence models were examined, in conjunction with a thermochemistry model that included a presumed-shape (Gaussian) probability density function (pdf) approach for the gaseous reactions and a laminar-like closure for catalytic reactions. Comparisons between predictions and measurements have shown that key CST issues, such as catalytic fuel conversion and onset of homogeneous ignition, depend strongly on the capacity of the various turbulence models to capture the intense flow laminarization in• duced by the heat transfer from the hot catalytic surfaces. A turbulence model that yields good agreement with the measurements is presented as particularly suited for CST applications. 1 INTRODUCTION and the model of Ezato [7]. The thermochemical clo• sure was the same as in Ref. [2]. In previous laminar-flow catalytically stabilized com• bustion (CST) studies of H2/air mixtures over Pt, we Case <£_ L/|N (m/s) ñeiN validated various hetero/homogeneous chemical reac• tion schemes in their capacity to reproduce key CST _J 018 20 15390 issues such as catalytic fuel conversion and onset of 2 024 20 15080 homogeneous ignition [1]. In practical systems (e.g. gas-turbines), the reactor inlet Reynolds numbers 3 0.24 40 30160 range from -5000 to -35000, thus requiring the devel• opment and validation of turbulent CST models. We Table 1 : Experimental conditions of turbulent H2/air have recently developed a turbulent CST code and CST over Pt. investigated numerically the underlying processes [2]. In the present work, measurements of turbulent H2/air 4 RESULTS AND DISCUSSION channel-flow CST at atmospheric pressure are com• pared against detailed numerical predictions with main PLIF-measured and numerically predicted OH distribu• goal to validate the CST-applicability of various tions are depicted in Figure 1 ; the predictions refer near-wall low-Reynolds number turbulence models. only to those models that yielded homogeneous igni• tion. The model of Ezato captured (within 16%) the homogeneous ignition distance (x¡g) and the 2 EXPERIMENTAL post-ignition flame shape in all cases, the model of Lin The channel-flow reactor consisted of two Pt-coated predicted ignition only for case 2, however, with a re• horizontal ceramic plates (300mm long, 104mm wide, sulting very short flame length and, finally, the two- placed 7mm apart, see Ref. [1]) and two quartz win• layer model yielded no homogeneous ignition in all dows positioned at the 300mm x 7mm reactor sides. cases. Planar laser induced fluorescence (PLIF) of the OH radical monitored the onset of homogeneous ignition, To understand the origin of the model discrepancies, 1-D Raman measurements of major species and tem• the turbulent transport processes were analyzed; the perature assessed the turbulent scalar transport, La• computed turbulent kinetic energy profiles for the mod• ser Doppler Velocimetry (LDV) yielded the inlet veloc• els of Lin and Ezato are given in Figure 2. The corre• ity and turbulence, and thermocouples embedded sponding profiles of the two-layer model were similar beneath the catalyst provided the surface tempera• to those of the Lin model, but with up to 80% higher ture. Three cases were examined, with the equiva• values at the downstream axial positions. The lence ratios ( Figure 3: the overall agreement was particularly good and provided a direct validation for the turbulent trans• port of Ezato's model. Mean mole fractions XH2, XH20 0.00 0.07 0.14 0.21 0.07 0.14 0.21 0.07 0.14 0.21 7.01 100 150 200 Streamwise distance x (mm) Fig. 1: Measured (Figures 1a, 2a, and 3a) and pre• dicted (Figures 1b, 2b-c, and 3b) distributions of the 400 800 1200 400 800 1200 400 800 1200 OH mole fractions for cases 1, 2, and 3 of Table 1. Temperature (K) The onset of homogeneous ignition (shown by the yellow arrows) in both measurements and predictions Fig. 3: Measured and predicted (Ezato model) mean is defined by the sharp rise of the OH profile. The nu• values of temperature, H2 and H20 mole fractions: (a) merical predictions refer to the following models: Fig• x= 40, (b) x = 130 and (c) x= 205 mm. Cases 1 (top), ures 1b, 2b, and 3b: Ezato and Figure 2c: Lin. In Fig• 2 (middle) and 3 (bottom). Measurements: H2 ures 2b and 2c only half of the channel is shown. (squares), H20 (circles), temperature (triangles). Pre• dictions: H2 (dashed-dotted lines), H20 (dashed lines) and temperature (solid lines). i Case 1 k Case 2 A Case 3 5 CONCLUSION V *0.5 In turbulent CST, key issues such as the catalytic fuel conversion and the onset of homogeneous ignition o 2 rz depend strongly on the flow laminarization induced by CD O y 3 iv\:0;25 ft Support was provided by the Swiss Federal Office of if\\— Energy (BFE) and Alstom Power of Switzerland. 7 REFERENCES 012301230123 y (mm) [1] C. Appel, J. Mantzaras, R. Schaeren, R. Bom- bach, A. Inauen, B. Kaeppeli, B. Hemmerling, and Fig. 2: Transverse profiles of turbulent kinetic energy A. Stampanoni, A., accepted, Combustion and for the models of Ezato (top row) and Lin (bottom Flame, 2001. row); x=0 (solid lines), x=100mm (dashed lines), x=200mm (dashed-dotted lines). For reasons of [2] J. Mantzaras, C. Appel, P. Benz, P. and U. Dog- clarity, the turbulent kinetic energy in case 3 has been wiler, Catalysis Today 59:3-17, 2000. multiplied by a factor of 0.5 (Ezato) and 0.25 (Lin); the [3] O. Deutschmann, R. Schmidt, F. Behrendt and J. profiles at x = 100 and 200 mm of cases 1 and 2 in Wamatz, Proc. Comb. Inst. 26:1747 (1996). Ezato's model have been multiplied by a factor of 4. [4] J. Warnatz, and U. Maas Technische Verbren• nung, Springer-Verlag, 1993, p. 102. ture of case 2 was higher than that of case 1). In the model of Lin, the decreased turbulence levels and [5] H.C. Chen and V.C. Patel, AIAA J. 26, 6:641 increased ç of case 2 allowed for the development of (1988). a weak flame; however, as there was no laminariza- [6] C.B. Hwang and C.A. Lin, AIAA J., 36, 1:38 tion and the turbulent kinetic energy increased, the flame extinguished shortly. Raman measured and (1998). predicted (Ezato model) average profiles of the tem• [7] K. Ezato, A.M. Shehata, T. Kunugi, and D.M. perature, H2 and H20 mole fractions are shown in McEligot, ASME, 121:546 (1999). 49 STRUCTURE AND N0X EMISSION OF TURBULENT PREMIXED METHANE/AIR FLAMES AT HIGH PRESSURE P. Griebel, R. Bombach, A. Inauen, W. Kreutner, R. Schären The influences of pressure, equivalence ratio, and mean inlet velocity on mean flame front position, flame structure, and NOx emission have been investigated experimentally in a new high pressure combustor. Qualitative planar laser induced fluorescence (LIF) of OH and NO was used to study the flame front struc• ture and the NO emission. In addition the NOx concentration was measured with conventional exhaust gas analysis. Decreasing the equivalence ratio increases the flame length and increasingly corrugates the flame front. Increasing the pressure or the velocity only slightly, respectively does not effect the mean flame front position but increasingly corrugates the flame front. The NO concentrations measured with gas analysis at the exit of the combustor are in good agreement with the results of the NO-LIF measurements. 1 INTRODUCTION the combustor inlet (Figure 1). In the present study, a perforated plate with a blockage ratio of 50 % and hole Lean premixed combustion of gaseous fuels is widely diameter of 3 mm was used as a turbulence grid. used in stationary gas turbines because of a highly efficient energy conversion and low NOx emissions. Although this technique is well established, there is still no quantitative description of the turbulence - chemistry interaction at gas turbine relevant conditions available at the moment. Turbulent premixed flames can be classified with respect to the turbulent Rey• nolds number ReT, Damköhler number Da, and Kar- lovitz number Ka, which can be expressed as a func• tion of the characteristic turbulence parameters, turbu• lence intensity and integral length scale, both being x = 0 normalised with the corresponding characteristic pa• turbulence grid ICCD camera gas probe location Isolation rameters of laminar premixed flames (laminar flame speed and flame thickness). The flame regime, typical Fig. 1: High pressure combustor (horizontal section). for stationary gas turbines, is characterized by 4 ReT> 10 , Da=1, and Ka> 10. For the classification In the LIF measurements a laser light sheet was intro• of the studied flames, the characteristic laminar flame duced through the window at the combustor exit, and parameters have been calculated with a correlation the LIF signal was detected with an ICCD camera, 90° obtained from a numerical study [1]. For the turbu• orientated to the light sheet. The detailed descrip-tion lence parameters typical values have been chosen. of the experimental set-up is given in [2, 3]. 2 EXPERIMENTAL SET-UP 3 RESULTS The parameters ReT, Da, and Ka have been varied The new high pressure combustor, which is designed for pressures up to 30 bar, temperatures up to 1850 K, systematically by changing the equivalence ratio 0, and a maximum thermal power of 400 kW, is shown in the pressure p, and the inlet velocity um. Figure 2 Figure 1. Fuel (methane) and combustion air, which shows the OH-LIF results for a variation of Da and Ka, can be preheated up to 823 K, are mixed homoge• managed by changing the equivalence ratio. Plotted is neously and fed into the combustor. A hydrogen torch the OH fluorescence intensity, which is a measure of igniter is used to ignite the mixtures and flame stabili• the relative OH concentration. In the averaged images sation is accomplished aerodynamically via a recircu• on the left side, the same scale is used, whereas each lation of hot burnt gases, induced by a back-ward fac• single shot is scaled individually. The white colour ing step. The liner of the combustor consists of two corresponds always to the maximum intensity. In• coaxial quartz glass tubes, being convectively cooled creasing the equivalence ratio moves the mean flame with air. Three large high pressure windows are im• front position at the axis of symmetry further up• plemented in the water-cooled combustor casing to stream, towards the combustor inlet. Due to the higher achieve an excellent optical accessibility for laser di• combustion temperature at higher equivalence ratio, agnostics. The hot exhaust gases exit the combustor the reaction rate and therefore the turbulent burning via a water-cooled pressure throttle and are then velocity increases, resulting in a shorter flame length. transported into the chimney. With the aid of a water- cooled gas probe located at the exit of the combustor The onset of the mean flame front at the axis of sym• and conventional exhaust gas analysis, the concentra• metry, named xjlame, is marked in the images with a tion of the main species are measured. The turbu• white vertical line. For the determination of this value, lence parameters can be varied easily by mounting the point of intersection of the tangent at the turning different turbulence grids at different axial positions at point of each axial intensity profile with the axis of 50 symmetry is used [3]. The single shot images of Fig• high NO formation rate due to the high temperature in ure 2 show that the flame front is increasingly corru• the region near the axis of symmetry and the maxi• gated if the equivalence ratio is decreased. mum residence time at the exit of the combustor. averaged (1000 shots, same scale): single shot (auto scaled): y [mm] • increasing intensity increasing intensity averaged images (250 shots): 37.5 115 310 [mm] Fig. 4: Averaged fluorescence intensity of NO at o> = 0.71 (673 K, 1 bar, 60 m/s). Fig. 2: OH fluorescence intensity for a variation of i> (673 K, 5 bar, 30 m/s, ReT= 620). Figure 5 shows the intensity profiles of NO along the x-axis. Increasing the equivalence ratio results in In Figure 3 the influences of pressure, inlet velocity, an increase of the NO-LIF signal because of a higher and equivalence ratio on the normalized mean flame NO formation rate due to higher temperature. This front position are summarized. The value x_flame, is trend can also be observed in the NO concentrations herein normalized with the combustor inlet diameter d. measured with gas analysis at the combustor exit. 7000 - o +j 0.50 c 6000 - S! 3O -A—p-variation, 673 K, 45 m/s, phi=0.5 o 5000 - E •5 a -A - p-variation, 673 K, 30 m/s, phi=0.43 c 4000 - O) 4.5 °¡ —®—u_m-variation, 673 K, 1 bar, phi=0.5 0.40 5 O O" ñ 3000 - -o - u_m-var¡at¡on, 723 K, 5 bar, phi=0.43 111 LL '5 V _l -•—phi-Variation, 673 K, 5 bar, 30 m/s 2000 - 0.3S Ó -o - phi-Variation, 673 K, 10 bar, 30 m/s z 1000 - 3 4 5 6 7 8 0.30 Normalized mean flame position (x_flamme/d) 50 100 150 200 250 300 350 Axis of symmetry x [mm] Fig. 3: Influence of p, um, and 0 on the normalized mean flame front position at the axis of symmetry. Fig. 5: Averaged, axial intensity profiles of NO and NO concentration at the combustor exit for a variation Among the studied parameters [3] the strongest influ• of O (673 K, 1 bar, 60 m/s). ence on the normalized mean flame front position and therefore on the turbulent flame speed can be as• The NO-LIF signal levels have been scaled on the signed to the equivalence ratio. Increasing the pres• basis of the NO concentration at O = 0.50. Therefore sure results in a slight decrease of the normalized for higher equivalence ratios one has to consider that mean flame front position, which can be interpreted as the signal levels have to be slightly corrected because a small increase in turbulent burning velocity. These of density effects (higher temperatures). The NO con• results are quite astonishing because a greater and centrations measured with gas analysis at the exit of opposite influence of pressure on the mean flame the combustor are in good agreement with the results front position would have been expected from the of the NO-LIF measurements. comparison with laminar flames, of which the laminar flame speed strongly decreases with increasing pres• sure [1]. Obviously the influence of the laminar flame 4 ACKNOWLEDGEMENT speed on the turbulent flame speed is compensated The authors would like to thank the Swiss Federal by the increase of the turbulent Reynolds number. Office of Energy (BFE) for the financial support. Increasing the mean velocity and thereby the turbu• lence intensity increasingly corrugates the flame front 5 REFERENCES but does not effect the mean flame front position. [1] M. Witt, P. Griebel, Technical Report As a typical result of the NO-LIF measurements, Fig• TM-50-00-07, Paul Scherrer Institut, (2000). ure 4 shows an averaged image of 250 single shots measured at 673 K, 1 bar, 60 m/s, and O = 0.71. To [2] P. Griebel, R. Bombach, W. Kreutner, A. Inauen, enhance the laser light intensity in the light sheet, the R. Schären, M. Witt, K. Herrmann, VDI-Berichte vertical dimension of the light sheet has been re• Nr. 1629, 639, (2001). stricted to one half of the combustor diameter. The [3] P. Griebel, R. Bombach, A. Inauen, W. Kreutner, highest intensity of the NO-LIF signal is found in a R. Schären, Paper (submitted) for the 6th INFUB region near the axis of symmetry at the exit of the Conference, 02-05 April 2002. combustor. This has been expected because of the 51 EXPERIMENTS ON THE SOOT REDUCTION POTENTIAL OF OXYGENATED FUELS S. Kunte (ETH Zürich), T. Gerber, M. Tule], B. Bougie, P. Radi, P. Beaud, G. Knopp We investigate the features of oxygenated compounds like dimethylethers and acetáis as a fuel compo• nent with the aim of reducing particulate emissions of Diesel engines. Together with the ETH lab for inter• nal combustion we conduct experiments on diffusion flames stabilized on burners and on transient burning sprays in a high pressure combustion cell. The content of soot and the localization of flame fronts were measured for a quite comprehensive set of Wolfhard - Parker flames. The results are amenable to model testing and will provide a further step towards elucidation of soot production mechanisms. 1 INTRODUCTION A series of measurements were performed starting with flames fuelled by ethylene alone. A part of ethyl• The main pollutants produced by Diesel engines are ene was then replaced in 10% steps by the other fuels NOx and soot. In a technical engine layout both harm• to be tested. Undiluted flames (fuel/air) and diluted ful substances can not be reduced simultaneously, flames (fuel + nitrogen/air) were investigated. rather, minimization of NOx ends up in an increased soot exhaust and vice versa [1]. This fact results in a To specify the soot production and soot oxidation in NOx-soot trade-off which can only be overcome by an the flame Laser Induced Incandescence (Lll, [3]) was exhaust after - treatment technique or by the use of a used to measure the soot volume fraction fy, i.e. the less soot-prone fuel. An addition of oxygenated com• volume occupied by soot in a unit volume. The Lll pounds like dimethylether (DME) or acetáis (e.g. di- signal captured with a CCD camera yields a map of fy methoxymethane DMM) to conventional Diesel could covering the whole flame with one laser pulse. The produce such a fuel [2]. To investigate the features of acetáis as fuel compo• 16 8 nent, we perform experiments with two test rigs within a joint ETH/PSI project. Using a Wolfhard-Parker burner soot volume fractions are measured for a vari• ety of fuel mixtures. Spray propagation and spray combustion realized in an optical accessible constant volume combustion cell are visualized and character• ized by different laser diagnostic techniques. 2 FLAME EXPERIMENTS An experimental study of ethylene flames for a wide range of admixtures of ethane, DME and DMM has been performed. Measurements of spatially resolved soot volume fractions, flame front positions and tem• Fuel 0.13 l/min Air15l/min perature fields provide a comprehensive database for + N2 dilution model validation. Fig. 1 : Wolfhard-Parker burner. The overventilated, non-smoking, laminar diffusion Laser Induced Fluorescence (LIF) technique applied flames with basic fuel ethylene (C2H4) were stabilized on a Wolfhard-Parker burner (Figure 1). This slit to OH radicals provided the position of the flame front burner creates a 2-dimensional flame sandwiched which moved in a smooth and continuous way de• between two parallel air flows. The flame has a visible pending on the amount of admixed test fuel. A two- sooting height around 40 mm with an undiluted fuel color pyrometry technique was developed to measure flow of 0.13 l|M/min. the temperature field of the flame. Applying the three measurements on every single flame a comprehen• The admixture of oxygenated fuels influences the sive set of data is obtained: the position of every point sooting tendency of other fuels by several effects that can not be differentiated readily. To simplify the inter• relative to the flame front, the local soot content, and pretation of the results we tried to keep constant as the local temperature. These quantities are the targets many parameters as possible to avoid competing ef• that should be met by existing models and may serve fects that cannot be discriminated against each other as a guide to model improvement if agreement is not a posteriori. readily achieved. The investigated fuels were therefore selected to have 3 FLAME RESULTS a similar structure (aliphatic), a comparable content of C-atoms (ethylen, ethane and DME = C2, DMM = C3) Figure 2 shows a combination of Lll soot measure• and a comparable calorific value (1.46 - 1.98 MJ/mol). ments and flame front positions derived form OH LIF All those fuels indeed exhibit adiabatic flame tempera• measurements. The grey shades indicate maximal tures around 2330 ± 50 K. soot volume fraction at a height close to the flame tip 52 situated on the burner axis. The visible shape of the provide the required accuracy for a definite assess• flame corresponds approximately to the zone in which ment. Still, we believe that the obtained data in con• soot is observed. Other flame zones hardly emit light junction with flame modelling constitute a substantial in the visible and may, if at all, only be discerned by step towards an increased and a better understanding careful inspection against the luminous soot back• of flame mechanisms in the presence of oxygenated ground. The flame fronts off axis almost reach down to fuels. the burner orifice. Their width at the bottom corre• sponds approximately to the width of the fuel slit. 4 COMBUSTION CELL EXPERIMENTS A 10% substitution of ethylene by ethane, though less The experiments on our high pressure high tempera• prone to soot production than ethylene, unexpectedly ture test rig (HTDZ) allowing an assessment of spray results in a discernible increase of total soot content in combustion under engine like conditions could not be the undiluted flame. Only with higher concentrations of pursued as scheduled due to major upgrades urged the substituent the total soot volume decreases. As by earlier measurements. A failure in the electronic anticipated, it also decreases with increasing dilution. part of the common rail injector initiated installation of a totally novel controlling unit. It is possible now not Similar results [4] were obtained for the ethylene/DME only to gate the injector for intermittent action but to flames. (The second flame from left contains more control the injection rate during one pulse. Another soot than the left most in Figure 2). A stronger reduc• upgrade concerns the fuel line. With a mechanical unit tion of soot was observed for higher (>10 %) substitu• which uses the existing Diesel pump assembly as tions by DME than with equal amounts of ethane. An hydraulics, a fuel from a dedicated container is fed to even more pronounced effect is observed with the the combustion cell. The installation avoids purging of doubly oxygenated methylal. Comparing flames with the Diesel pump and therefore facilitates swift meas• 20 % and higher additions of the investigated fuels, urements necessitating a quick change of fuel blends. the soot reduction potential of DM M clearly outper• With these changes the HTDZ set up is fully opera• forms DME, both fuels being valuable candidates for tional again. future Diesel blends. 5 ACKNOWLEDGEMENT This work was supported by the Swiss Federal Office of Energy (BFE). The Acetáis used in our studies were provided by Lambiotte & Cie, Belgium. 6 REFERENCES [1] C.Y. Choi, R.D. Reitz, An experimental study on the effects of oxygenated fuel blends and multi• ple injection strategies on Dl engine emissions, Fuel 78, 1303 (1999). Fig. 2: Visualization of soot content in Ethylene/DME flames. Ethylene is replaced by DME in 10 % steps [2] A. Bertola, K. Boulouchos, Oxygenated Fuels starting at 0% (pure ethylene) for the flame left most. for Particulate Emissions Reduction in Heavy- The lines indicate the location of the flame front de• Duty Dl-Diesel Engines with Common-Rail Fuel rived from OH - LIF measurements. Injection, SAE-paper 2000-01-2885 (2000). [3] H. Zhao, N. Ladommatos, Optical diagnostics for soot and temperature measurements in Die• In earlier experiments we found that temperature sel Engines, Prog. Energy Combust. Sei., 24, changes can not explain the different sooting behav• 221, (1998). iour of the investigated flames. The changes are rather due to a modified chemistry in the presence of [4] S. Kunte, M. Tulej, P. Radi, T. Gerber, K. Bol- different fuel components. The evaluation of the py- ouchos, Flame experiments on the soot reduc• rometric measurements of the temperature field are tion potential of acetáis in diffusion flames, IEA still in progress. First attempts have shown that tem• Conference Proceeding, 23rd Task Leader peratures obtained with this technique possibly do not meeting, Kauai, Hawai (2001). 53 QUANTITATIVE ANALYSIS OF TWO-COLOR RESONANT FOUR-WAVE MIXING SPECTRA OF THE OH RADICAL P.P. Radi, A.P. Kouzov, P. Beaud, T. Gerber, G. Knopp, M. Tulej The theory of collision-induced resonances in two-color resonant four-wave mixing (TC-RFWM) spectra is refined. Rotational energy transfer (RET) accompanied by dephasing is shown to be the key process de• termining the observed TC-RFWM intensity distribution in the A 2E+- X 277¡ (0-0) band of OH. A fast- collision model of the generalized rotational relaxation is elaborated which applies to an arbitrary type of intramolecular rotation-spin-electronic momenta coupling. With a single set of parameters, it allows to simulate the rotational relaxation occurring in population, orientation and alignment gratings formed in the upper and lower vibronic state. Preliminary computations are performed to fit the observed satellite intensities. The results are in a qualitative agreement with the known Z-Z energy transfer data. In addition, new state-to-state rates on the lower potential energy surface in the 17-17 manifold are obtained. 1 INTRODUCTION To solve the problem B, we extended the fast-collision model of rigid rotators [8] in the case of diatomics with Four-wave-mixing techniques are utilized in numer• arbitrary spin-orbit-rotation couplings (different Hund's ous spectroscopic applications for combustion diag• cases). Based on the quantum equation of motion, the nostics. In fact, it has been shown that trace species model assumes the inverse collision duration to be like H, C2, CH, CO, OH, C3, CH3, CN, NH NO, N02, much greater than the level splittings in both vibronic NH3, HF and S2 are sensitively detected in combus• states. Taking into account the large number n of ma• tion environments [1]. In addition, the methods are trix elements needed for practical applications (typi• increasingly applied to the study of molecular dynam• cally, 103 sion-induced intensities (Table 1, column 4). Indeed, tain a particular line shape as a function of ^ and Q3. the RET rates decrease by more than a decimal order Total fitting of the accomplished experimental data in this range and, therefore, the PT intensities should (few tenth of TC-RFWM OH lines) is under way. Pre• drop by a factor of 102-103. However, the RET- liminary results on some RET-induced lines calculated induced resonances remain experimentally observ• with Hund's wave functions of cases A, B and inter• able for substantial energy gaps up to AE =1000 cm"1. mediate (A/B) are summarized in Table 1. In so doing, The extraordinary slow decrease of the observed the relaxation model parameters were fixed by scaling RET-induced signals as a function AE is a striking the values known for nitrogen [8]. For simplicity, it was feature of TC-RFWM that can be understood only if also assumed that these parameters remain the same the inverse relaxation matrix r for the F1-F1 satellites. Since our simulations show a high sensitivity of the grating terms to the relaxation Probed Exper• Calc. Calc. Calc. Calc. model parameters, the remaining misbalance for the Rotational iment A/B PT, B A RET-induced spin-flip (FrF2) transitions (lower part of Transiton A/B Table 1 ) possibly shows the necessity to use different sets of relaxation parameters for upper and lower Rid) 0.26 0.13 0.05 0.01 0.13 electronic states. Ri(2) 0.89 0.88 0.40 0.53 0.77 3 ACKNOWLEDGMENT 4.0 3.7 2.2 2.5 2.9 Ri(4) The financial support of the Swiss Federal Energy Ri(6) 1.4 2.1 1.5 1.1 0.95 Office (BFE) is gratefully acknowledged. Ri(7) 1.0 0.51 0.48 0.11 0.01 4 REFERENCES Ri(9) 0.41 0.13 0.03 0.41 1.22 [1] K. Kohse-Hoinghaus, J.B. Jeffries (Ed.), Applied Combustion Diagnostics, to be published. R2(3) 0.46 0.12 0.03 0.00 0 [2] P.H.Vaccaro, in E. Hirota, R.W. Field, J.P. Maier, R2(4) 0.52 0.32 0.03 0.05 0 S. Tsuchiya Nonlinear Spectroscopy for Molecu• lar Structure Determination Blackwell, London R2(5) 0.59 0.64 0.02 0.22 0 (1997). R2(6) 0.75 1.1 0.01 0.52 0 [3] P.P. Radi, H.-M. Frey, B. Mischler, A.P. Tzannis, R2(7) 0.39 1.5 0.01 0.92 0 P. Beaud, T. Gerber, Chem. Phys. Lett. 265, 271 (1997). [4] B. Hemmerling, P.P. Radi, A. Stampanoni- Panariello, A.P. Kouzov, D. Kozlov, C. R. Acad. Table 1 : Measured and computed peak intensities lk of Sei. Paris, Série IV, 2, 1001 (2001) selected rotational transitions in the (0-0) band of the 2X-2n¡ electronic transition of OH. The intensities are [5] A.P. Kouzov, P.P. Radi, Phys. Rev. 63A, 01070-1 given in % of l(Ri(5)). The pump laser is fixed on the (2000). P-\(5) transition. PT: Peturbation Theory, A: Hund's [6] A.P. Kouzov and P.P. Radi in Spectroscopy of case A, B: Hund's case B, A/B intermediate Hund's non-equilibrium plasma at elevated pressures, case. See text for details. Vladimir N. Ochkin (Ed.), SPIE, 4460 to be pub• lished in 2002 Interestingly, it is found that the signs of the rW 1 - [7] P.P. Radi, A.P. Kouzov, P. Beaud, T. Gerber, PSI matrix elements may vary. As a consequence, a con• - Scientific Report V, 54 (2000). structive and destructive interference between the [8] A.P. Kouzov, Phys. Rev. 60A, 2931 (1999). upper- and lower-state grating terms is possible. [9] P. Beaud, P.P. Radi, D. Franzke, H-M. Frey, B. Because of their complexity, the computer calcula• Mischler, A.P. Tzannis, T. Gerber, Applied Op• tions are time-consuming taking about 10 min to ob• tics, 37, 3354 (1998). 55 FEMTOSECOND PHOTODISSOCIATION OF THE ETHYL RADICAL G. Knopp, P. Beaud, P.P. Radi, M. Tulej, A.P. Kouzov, B. Bougie, T. Gerber The first observation of the ultrafast H atom release of the ethyl radical was achieved. Once electronically excited, C2H5 undergoes a rather complicated dissociation process, which is still not complete understood. With the pump probe multiphoton ionization technique we were able to show, that at least one product channel is present in the ultrafast time regime (fs). Further, a second 'slower' channel in the ps time re• gime was observed. 1 INTRODUCTION Alkyl radicals constitute a class of unstable hydrocar• C H + bon species with central importance in combustion 2 4 processes. Especially the dynamics of the H atom 3 Ip X B5„ loss and the generation of a double bond is of major interest. As one of the simplest alkyl radicals, ethyl (C2H5) represents an important prototype for even dynamically more complicated radicals. The first un• structured absorption band of ethyl refers to the 3s- ^ *»-2A'(3p) -i-A'B,. J Rydberg state, which is expected to decay very rap• A'(3s) 'Fast' ? idly by internal conversion to the ground electronic state after absorption of a UV photon. Calculations C H + I(2P ) 2 5 ia 'Slow' ? predicted reaction rates for the H atom loss in the CA + lfP^ -X'A, 2 order of 1011 s1 to 1012 s1 [1]. Gilbert et al. [2] have A' measured reaction rates of 1.8*107 s1 by nanosecond Ethyl Iodide Ethyl photo excitation and ion detection of the released Ethylen hydrogen atom. This discrepancy of 5 orders of mag• Fig. 1 : Energy level scheme of the C2H5 pump probe nitude between calculation and experiment is still not multiphoton ionization. understood. Recently Amaral et al. [3] investigated the photodissociation of ethyl, measuring the H atom en• state and an I or I* atom [4]. The branching ratio (l/l*) ergy-dependent angular distribution after UV excita• between the channels is approximately 1/3. Therefore, tion and concluded that at least two channels for the it has to be considered that the released ethyl radicals dissociation exist: A 'slow' channel, which is isotropic are energetically not cold. The 'initial' excess energy in character for H atom release and therefore ex• of the ethyl radical varies between 0.41 eV (I* channel pected to be comparable (or longer) in lifetime with a / 265 nm) and 0.78 eV (I channel / 250 nm) [5]. There• rotational period (~ ps), and a fast anisotropic channel fore the final excitation energy upon absorption of an with high kinetic energy release, suggesting a prompt additional UV photon within the same laser pulse is and direct dissociation from the excited 2A'(3s) state between 5.07 eV and 5.74 eV. This energy is not high via its C2V configuration 2Ai(3s). enough to excite the 3p-states of the radical. 2 EXPERIMENT 3 RESULTS AND DISCUSSION We report multiphoton induced ion signals of ethyl Figure 2 shows two typical ion signals for C2H5 and radicals after photo excitation from the X2A' ground C2H5I, as function of the probe delay. The data are electronic state into the 3s-Rydberg state on a femto• presented together with their least square optimized second time scale, yielding a first direct measurement fitted curves. The fit-model interactively fits the mother of the fast dissociation process of C2H5. For the deliv• and the ethyl signal, including the two coupled time erance of the radicals, ethyliodide (C2H5I) is used as constants (x-i, x2). These time constants reflect the precursor. The direct photodissociation of dissociation of the mother molecule into ethyl and C2H5I->C2H5+I and further excitation and dissociation iodine (x-i) and the dissociation from the 2 A'(3s)- of C2H5->C2H4+H upon absorption of a 250 nm (265 Rydberg state of the radical (t2). For a 250 nm pump nm) photon is used to extract information about the pulse these decay times could be determined to x-\ = ethyl radical dynamics as depicted in Figure 1. The 40 fs and x2 = 370 fs. The contributions at coincidence 250 nm pulse simultaneously serves as 'photolytic most probably originate from excitations to the C2H5I pump' for the mother molecule and as excitation for ion states, followed by fragmentation to ethyl ions and the radical. It is expected, that C2H5I dissociates rap• neutral iodine. But because of the different pump and idly (x!<60 fs) after photo excitation to its electronic-A probe power dependence they could be well distin• 1 3 3 state ( Qi, Q0, Qi) intoC2H5in its ground electronic guished from the desired signals. 56 fast dissociation channel. It can be related to the ani• sotropic signal contributions of the experiments from Amaral et. al. [3]. Changing the excitation wavelength from 250 to 265 nm reduced the fitted time to i2 = 233 fs fa = 93 fs). In this case the final excitation of the radical is -3000 cm1 lower in energy. The molecules seem to dissociate faster with decreasing excitation energy. Even though a good correspondence between fit and experiment has been found by using a single (x2) dis• -500 -250 250 500 750 1000 1250 1500 sociation process for ethyl in the model, it might not be sufficient for longer delay times. It is expected that 1 1 1 1 1 1 1 1 1 1 1 1 1 1 the molecule undergoes an avoided conical intersec• & • C2H5- tion on its way to the C2v configuration [6]. This could PS ° c2H5r fairly disturb the direct dissociation and especially the \ À = 265 nm ¡a pump dissociation after the internal conversion to the ground electronic state. For example the H atom could be CS C Í ft tch (fit)=233±30fs- reflected back to its classical position after hopping CO ' H onto the ground state potential energy surface. There• c ^ < ;,(fit)=93±5fs ; o i fore an additional second ('slower') dissociation rate has to be considered. Increasing the delay times in our experiments to several pico-seconds gives some 0.0 -500 -250 0 250 500 750 1000 1250 1500 clear evidence for an additional decay process as Probe delay [fs] shown in Figure 3. Considering a high 'conversion'- rate [3], this 'slow' decaying contribution appears un• Fig. 2: Ion signals as function of the probe delay and expectedly weak in intensity. However, the depend• their best fitted curves. The time constants reflect the ence of the photo ionization matrix element on the dissociation of C2H5I (ti) and C2H5 (x2). geometry of the molecule is not negligible, and par• ticularly when the wave packet moves through a re• Upon the absorption of the UV photon, the 3s state gion of an avoided crossing, a change in the ionization has the same classical Cs structure as the ground probability is expected [7]. This second time constant state ethyl and the excited molecule appears in A2A' could be fitted to xS|0W - 6-7 ps, which is comparable geometry. After photo excitation one proton from the to the rotational periods of the molecules. This can be CH3 part slides to the C2v bridging position over the interpreted as time for the tunnelling and moving out centre of the CC-bond. The resulting A2A state is ï of the 'ionization window'. For a more stable state• unstable with respect to H detachment and dissoci• ment concerning the 'slow' decay processes addi• 1 2 ates without any barrier to the C2H4 (X Ag) and H ( S) tional investigations including different precursors are products [6]. required. However, our results clearly confirm the presence of a fast dissociation channel with a disso• ciation rate in the order of -3*1012 s1 and a 'slower' t. = 6630 ± 654 fs process of -2*1011 s_1 as proposed in Ref. [1,3,6]. slow 3 cj 800- 4 REFERENCES [1] W. Hase, B. Schlegel, V. Balbyshev, M.Page, J. Chem. Phys., 100, 5354 (1996). [2] T. Gilbert, T. Grebner, I. Fischer and P. Chen, J. 5000 100O0 15000 20000 25000 Chem. Phys.,110, 5485 (1999). pq 200- Probe delay [fs] [3] G. Amaral, K. Xu, and J. Zhang, J. Chem. Phys., 114, 5164 (2001). Probe delay [fs] [4] N. Knoblauch, A. Strobel, I. Fischer and V. Bon- dybey, J. Chem. Phys., 103, 5417 (1995). Fig. 3: Ethyl ion signal from 2.5 to 28 ps probe delay. [5] W. Kang, er al., Chem. Phys. 196, 363 (1995). The signal shows evidence of a slow dissociation process. [6] A. Zyubin, A. Mebel and S.Lin, Chem. Phys. Lett., 323, 441 (2000). We believe that the x2 dissociation time observed in [7] Y. Arasaki, K. Takatsuka, J. Chem. Phys., 112, our experiments is the first direct observation of this 8871 (2000). 57 SOUND GENERATING FLAMES OF A GAS TURBINE BURNER OBSERVED BY LASER-INDUCED FLUORESCENCE W. Hubschmid, A. Inauen, R. Bombach, W. Kreutner, S. Schenker, M. Zajadatz (Aistom), C. Motz (Aistom), K. Haffner (Aistom), CO. Paschereit (Aistom) We performed 2-D OH LIF measurements to investigate the sound emission of a gas turbine combustor. The measured LIF signal was averaged over pulses at constant phase of the dominant acoustic oscillation. A periodic variation in intensity and position of the signal is observed and it is related to the measured sound intensity 1 INTRODUCTION sound from the loudspeakers (power maximum: 8 x 150 W) was irradiated into the combustor in order The sound emission by flames has found great inter• to obtain a steady sound level. The loudspeakers gen• est since many years and numerous works on the erated sound pressures of up to about 0.4 mbar in the origins and features of sound in combustion proc• combustion tube. esses have been published. The first investigations go even back to the 19th century. From the engineering For most of the experiments, in order to lower the and economic point of view the occurrence of acoustic sound reflection at the tube end, a sound-absorbing oscillations in gas turbine or other combustors is a orifice plate was mounted. Earlier measurements (see very serious phenomenon as it can lead to strong Ref. 3) proved that for the sound frequency domain vibrations, which may even damage the machine. considered by us, the orifice reduces the sound reflec• Ferguson et al. [1], e.g., review recent developments tivity to less than 50%. on instabilities and sound generation in combustion, To excite the OH molecules, laser light with a wave• and Paschereit et al. [2] among others focus their length of 286 nm was used. The laser beam originated attention specifically on combustion instabilities in gas from frequency doubling the light of a dye laser. By turbines. cylindrical lenses the beam obtained the shape of a In the present work, we report on laser optical meas• thin sheet, which was irradiated from below into the urements in a test rig with a gas turbine combustor, combustion chamber tube (see Figure 1). The sheet which emitted sound of a rather high intensity. OH LIF width was 11 cm at the entrance into the tube and measurements (LIF: laser-induced fluorescence), 14 cm at the exit of the tube. The direction of the sheet using the light sheet technique, were performed in plane was along the symmetry axis of the tube, i.e. the order to see correlations between optical quantities main flow direction. and the measured sound intensity. LIF data were taken for single laser pulses, as well as averaged over many pulses at the same phase angle of the dominant sound oscillation. The experimental set-up is de• scribed in more detail in Sec. 2 below. In Sec. 3 results of the OH LIF measurements are presented and an attempt to their interpretation is undertaken. To conclude (Sec. 4), we note a few re• marks on the building up of the flame oscillations. For the results of the measurements of the OH chemilu- minescence intensity that were performed simultane• ously, we refer to a forthcoming paper. 2 EXPERIMENTAL SET-UP Fig. 1 : Experimental set-up. The LIF signal was detected with a CCD camera at The combustor investigated was a commercial pre• right angles to the light sheet plane. The data obtained mixed gas turbine burner of Alstom, driven by natural were corrected (see Ref. 4) with respect to the men• gas. Upstream of the burner was the air and fuel sup• tioned beam divergence and to the extinction (up to ply and downstream a cylindrical tube, which served 60%) of the laser light while passing through the com• as combustion chamber and which guided the burnt bustion tube. gases outside of the laboratory. The part of the tube that surrounded the flame region was manufactured 3 RESULTS AND ANALYSIS from UV-transmitting quartz glass. Experiments were performed for a large number of burner configurations and operating conditions. We To measure the sound pressure in the combustion present here some preliminary results. The Figs. 2 chamber tube, a microphone was installed close to the and 3 depict examples of single-pulse and phase- flame zone. Furthermore, loudspeakers were posi• averaged LIF intensity distributions in the flame region tioned around the combustion tube and the fuel/air of the combustion chamber. supply. Because the flame sound often was of too a transient nature so that phase-averaged measure• The phase-averaged pictures show generally that the ments were not possible, for many of the experiments OH-zones oscillate in space and time synchronously 58 to the sound oscillation. In order to describe quantita• loudspeakers, and otherwise identical operating condi• tively the spatial motion of the OH zone, we deter• tions, sound pressures of up to about 12 mbar were mined from the data the mean of the phase-averaged generated. The temporal LIF intensity variations and OH signal intensity with respect to the axial (main flow) the amplitudes of the spatial motion of the LIF zone direction. We observe that, in general, the outer part of were roughly proportional to the sound pressures. the OH zone oscillates stronger, and oppositely to the 4 CONCLUDING REMARKS central part. Turbulent combustion in general produces heat re• lease that varies in time and position, and the sound generated has a broad frequency spectrum. For the combustor investigated by us, the reflection of the sound at the tube exit gives rise to a standing wave in the interior of the tube, and it feeds the acoustic dis• turbance back to the flame region. Constructive su• perposition of incident and reflected wave is only pos• sible for the fundamental and for overtone frequen• cies. This process of selection and amplification is Fig. 2: Single pulse OH LIF measurements in the presumably supported if the resonance frequencies combustion chamber at phase angle 0°; extinction and are in a favourable relation to the revolution frequen• divergence corrected; logarithmic brightness scale. cies of the dominant flow vortices in the tube. A num• ber of authors (see e.g. Ref. 6) could show experimentally that there is a strong influence of sound waves on turbulent motion. This is one of the effects discussed in the literature, which could eventu• ally lead to a flame surface area that oscillates in time, and therefore to a temporal and spatial oscillation of the flame heat release, which causes the strong emission of sound as observed in our experiment. 5 ACKNOWLEDGEMENT Fig. 3: Phase averaged corrected OH LIF measure• Financial support by the Federal Office of Energy ments for the oscillation phases 0°, 90°, 180°, 270°. (BFE) is gratefully acknowledged. The temporal oscillation of the integral OH LIF inten• 6 REFERENCES sity can be interpreted as a temporal oscillation in heat [1] D.Ferguson, G.A.Richards, S.D.Woodruff, release, as the OH LIF intensity is an approximate S. Bernai, M. Gautam, Effect of surface area measure for it. We assume proportionality between variation on heat release rates in premixed the two quantities, which is approximately correct for flames, Paper presented at 2nd joint Meeting of properly chosen spatial averages of the LIF intensity. the U.S. Sections of the Combustion Institute, The sound pressure amplitude emitted by the flame March 2001. can now be calculated. For that purpose we insert the heat release variation, represented by the phase- [2] CO. Paschereit, P. Flohr, B. Schuermans, Pre• averaged LIF signal intensity, as driving force into the diction of combustion oscillations in gas turbine acoustic wave equation [5]. We neglect any other combustors, Paper AIAA 2001-0484, presented source term, including the turbulence source term, at the 39nd AIAA Aerospace Sciences Meeting, and we assume the OH zone to be planar and homo• January 2001. geneous within the plane. With a sinusoidal temporal variation of the LIF intensity of ±8%, and using the [3] CO. Paschereit, E. Gutmark, W. Weisenstein, parameters of the burner operation, we find that a Excitation of thermoacoustic instabilities by the in• planar sound wave with pressure amplitude of about teraction of acoustics and unstable swirling flow, 1.7 mbar is generated. In the calculation the reflection AIAA Journal 38,1025 (2000). of the sound at the tube end, which amplifies the [4] A. Arnold, R. Bombach, W. Hubschmid, sound pressure within the tube and which gives rise to A. Inauen, B. Käppeli, Fuel-oil concentration in a a standing wave, is not yet taken into account. Hence gas turbine burner measured with laser-induced we didn't consider either how the standing acoustic fluorescence, Exp. Fluids 29, 468 (2000). wave is fed by the flame-generated sound wave. The strength of this process depends on the relative phase [5] U. Ingard, in Handbook of physics, 2nd edition, of the two waves. E.U. Condon, H. Odishaw, eds., McGraw-Hill, 1968. The 8% temporal variation of the LIF intensity was observed in an experiment without orifice plate and [6] T.J. Poinsot, A.C. Trouve, D.P. Veynante, without operation of the loudspeakers. The pressure S.M. Candel, E.J. Esposito, Vortex-driven acous• amplitude measured here was about 5 mbar, which tically coupled combustion instabilities, corresponds to 148 db. With acoustic forcing by the J. Fluid Mech. 177, 265 (1987). 59 INVESTIGATION OF COUNTER FLOW DIFFUSION FLAMES Ch. Frouzakis (ETH Zürich and PSI), A. Inauen, W. Kreutner Direct Numerical Simulations predict a novel flame shape and a hysteresis phenomenon for laminar diffu• sion flames. With a simple experimental setup the phenomenon could be demonstrated, and first meas• urements of two-dimensional laser induced fluorescence of OH could be obtained. 1 INTRODUCTION agreement with the hysteresis observed in the simula• tions. In the range of flow rates between the upper Laminar strained diffusion flames are important for the and lower critical value it was possible to "switch" from modeling of turbulent diffusion flames in the flamelet one flame type to the other by perturbing the flow with regime. In the usual plot of peak flame temperature a thin metal sheet. vs. Damköhler number, their dynamics are described by a well-established S-shaped curve which consists Figure 1a shows a disk-shaped diffusion flame hover• of a stable lower branch (corresponding to pure mix• ing between the two tube ends. Figure 1b shows the ing or slow reaction), an upper stable branch (in• toroidal edge flame, as can be noted by the absence tensely burning flame), and an unstable (physically of chemiluminescence in the center. The flame front, unrealizable) branch joining the other two. Using Di• whose shape and size depend on flow conditions, is rect Numerical Simulation (DNS) for the solution of the established off axis. The flame that was "blown out" in conservation equations of mass, energy and species, the center can re-ignite upon reduction of the strain workers at the ETHZ LVV analysed such flames in an rate. Figure 1c shows the 2-dimensional OH LIF sig• axisymmetric H2/air 2-D counterilow burner [1]. nal from the diffusion flame; the closed surface is ap• parent. Figure 1d shows the LIF signal from an edge It was found that in addition to the two stable solutions flame. The two almost spherical regions are the cross mentioned above, an additional intensely-burning sections of the left and right side of the flame torus. flame with a toroidal shape can be obtained. Further• more, over a large range of flowrates these two differ• The phenomena observed here have implications for ent types of flames can be obtained at the same pa• the modeling of turbulent technical flames. While DNS rameter values, and there is a strong hysteresis asso• gives a complete description of the counterilow diffu• ciated with the transition from the well-known disk- sion flame, its high computational cost makes it diffi• shaped diffusion flame to the toroidal edge flame. It is cult to cover large parameter ranges. Further experi• therefore expected that perturbations can induce a ments will be used both for validation and for paramet• "switching" of the system between these two flame ric studies, particularly for complex fuels. shapes. 2 EXPERIMENTAL A counterilow diffusion burner was set up, consisting of two vertical, axially aligned steel tubes. The tube lengths were chosen to give a laminar, parabolic flow profile. Plane disks attached to the tube ends reduce the effects of ambient air entrainment. Pure methane was issued from the lower tube, whereas the oxidizer (air) was supplied through the upper tube. Typical flowrates were in the range of 1.4 slm/cm2 for fuel and C d 3.3 slm/cm2 for air. Pictures of the visible flame emission were taken with Fig. 1 : Top row shows visible chemiluminescence a commercial digital camera. For flame-zone visuali• from a methane-air counterilow flame. Bottom row zation, two-dimensional Laser Induced Fluorescence shows two-dimensional OH LIF images. Left column: (LIF) measurements of the OH radical, an important Diffusion flame; right column: Toroidal edge flame. intermediate species marking the flame front, were obtained. The LIF signal provides a cross sectional 4 ACKNOWLEDGMENT view of the three-dimensional flame. Financial support from the Bundesamt für Energie 3 RESULTS AND DISCUSSION (BFE) is gratefully acknowledged. As expected, a strained disk-shaped diffusion flame 5 REFERENCES could be stabilized on the burner. By increasing the oxidizer flow velocity above a critical value the flame [1] CE. Frouzakis, A.G. Tomboulides, U.C. Lee, K. extinguished at the center, and an edge flame was Boulouchos, From diffusion to premixed flames in produced. Reduction of the flowrate below an other an H2/air opposed-jet burner: the role of edge critical value re-established the disk-shaped flame, in flames, submitted to Combust. Flame (2001). 60 FLOW VELOCITY MEASUREMENTS IN A HIGH ALTITUDE SIMULATION CHAMBER USING LASER-INDUCED GRATINGS B. Hemmerling, D.N. Kozlov (General Physics Institute, Moscow), M. Neracher Light scattering from laser-induced electrostrictive gratings has been used for instantaneous, non- intrusive, and remote velocity measurements during cold-flow tests of a sub-scaled thrust optimized pa• rabola rocket nozzle. For the first time the existence of a re-circulation zone in the center of the flow field at 10 bar, predicted by computational fluid dynamic calculations, has been experimentally proven. 1 INTRODUCTION beam is mixed with a reference beam of frequency CO3 three oscillation frequencies appear in the power Nozzles of launchers are supposed to operate from spectrum of the heterodyne signal, namely, Q0. sea level up to high altitudes. At a certain ratio of noz• w _ an v zle wall pressure to ambient pressure the flow within = 0.5 Q0 - <0s . d ^2 = 0.5 Q0 + s + with cos = co0 - co3. Knowing the grating vector one the divergent part of the nozzle separates from the can determine from Q0 the sound velocity and nozzle wall causing a system of shocks, which re- thereby, if the composition of the medium is known, compresses the flow to a pressure level close to am• the temperature. The difference Q2 - ^1 allows, as bient pressure. Two different flow patterns are possi• far as co- is normally well known, to evaluate the com• ble, either with the separated flow from the separation ponent of the flow velocity parallel to q and the direc• point on (free shock separation), or with reattachment tion of the flow. of the flow to the wall (restricted shock separation). Transition between these two flow patterns can lead 2 EXPERIMENTAL to high lateral forces on the nozzle wall, which, under unfavorable conditions, may cause damage to the A pulsed Nd:YAG laser (ÀE = 1064nm, energy ~ nozzle. For restricted shock separation computational 100 mJ, repetition rate 100 Hz, pulse length 3.5 ns, fluid dynamics (CFD) calculations predict a re• spectral bandwidth 250 MHz) provided the two excita• circulation zone downstream of the shock pattern, tion beams to create an electrostrictive grating in a which is not existent or significantly smaller in case of standard experimental arrangement. The excitation free shock separation. The intention of this work is to beams were focused by a lens (f = 750 mm). Focused validate CFD calculations of the flow field associated by the same lens the beam of a cw Ar+-laser with restricted shock separation by identifying the re• (X = 514.5 nm, 200 mW) was employed to probe the circulation zone. For that purpose we employed laser- R grating. To obtain phase matching of the three beams, induced electrostrictive gratings. we used a 2-D forward geometry. Symmetrically to the Laser-induced gratings are spatially periodic modula• probe beam the reference beam was adjusted to over• tions of material properties. They are generated as lap the signal beam. Two frequency shifters intro• response to the interference structure formed by two duced a frequency difference of 3.40 MHz between laser beams of wavelength A,E and wave vectors k-¡ probe and reference beam. A fast photomultiplier tube and k2 intersecting at a shallow angle. If the laser detected signal and reference beam, and temporal intensity is sufficiently high acoustic waves are gener• acquisition occurred with a digitizer. To avoid damage ated by électrostriction. Constructive interference of to the photomultiplier tube by the high continuous light the sound waves occurs only normal to the plane of level of the reference beam an acousto-optical modu• the fringes. Eventually two sound waves are formed lator was em§§ployed to gate the Ar+-laser (gate- propagating with velocity vs in opposite directions, q width ~ 2 us). Hence, probe and reference beam were and -q, normal to the planes of the grating. Here, only present during the lifetime of the grating. q = k-¡-k2 denotes the grating vector. The counter- propagating acoustic waves form a standing wave and Measurements were performed at test site P6 at DLR, thereby a spatially periodic density grating that oscil• Lampoldshausen, Germany, in a high altitude simula• lates in time. It can be detected by diffracting the tion chamber. Nitrogen up to a maximum pressure of beam of a probe laser with frequency coq. The fre• 40 bar was supplied to a sub-scaled thrust optimized quency spectrum of the resulting signal beam com• parabola rocket nozzle, with 200 mm exit diameter prises contributions originating from each of the two and an overall length of 125 mm from nozzle throat to sound waves. Their Doppler shifted frequencies are nozzle exit. We selected the x,y-plane of our coordi• given by co^ = (Oq ± qvs, respectively. Beating of nate system to contain the exit plane of the nozzle, these two signal contributions results in an oscillation and the z-axis to coincide with the symmetry axis of w w v 2c tne of the signal at frequency Q0 = i - 2 = l s • If the nozzle and to point in direction of the main flow. grating is formed in a flow with velocity vf the frequen• The laser beams were adjusted to lie within the y,z- cies of the two signal contributions are given by plane. Preliminarily, only two measurement locations v °>i,2 = wo + q(vf ± s)- The oscillation frequency of the were selected, M1 = (x=0, y=0, z=50 mm) and signal remains unchanged. However, if the signal M2 = (x=0, y=15 mm, z=50 mm). 61 3 RESULTS For measurements at location M2 the pressure of the main flow was increased up to 40 bar at a constant Preceding measurements in room air provided the rate of 1 bar/sec. Only within a window of 1 bar width grating vector q and the frequency difference co- be• centred at 10 bar velocity measurements were possi• tween the two frequency shifters. Prior to starting the ble. We determined a mean velocity of -9.2±1.6 m/s main flow through the nozzle, the chamber was and a standard deviation of 11.6±1.4 m/s. Outside of flooded with nitrogen. The single shot measurements the pressure window the measurements were domi• taken during this time exhibit a Gaussian shaped dis• nated by a strong background that prevented velocity tribution with a mean flow velocity of 1.5±0.3 m/s and measurements. We speculate that scattering of the a standard deviation of 2.7±0.2 m/s. probe beam on micro-turbulences causes this back• ground. Í2, j £22 n On I AA .¡te. I ' I 0 w5 10 15 20 25 30 -0.10 -0.05 0.00 0.05 0.10 0.15 frequency / MHz z-position / m Fig. 1 : Power spectrum of a single-shot measure• ment taken at 10 bar. Fig. 2: CFD calculations of the flow velocity on the centre line for 8 bar (dashed line) and 10 bar (solid As soon as the pressure of the main flow raised a line) [Courtesy of W.Kwan, DLR, Lampoldshausen]. strong and fluctuating background appeared that Velocities on the centre line of the nozzle, determined dominated the temporal evolution of the grating signal. by CFD calculations for pressures of 8 and 10 bar, The power spectrum exhibits peaks that cannot be respectively, are depicted in Figure 2. Negative veloci• indubitably assigned to the expected frequencies. At ties indicate the existence of a re-circulation zone at 10bar, however, the situation improved again and 10bar. Our measurements strongly support these velocity measurements could be performed. The pres• calculations in two aspects. Firstly we measured a sure was kept constant and about 1000 single-shot negative velocity component at M1, and secondly the measurements were acquired at location M1 and were re-circulation zone exists only in a relatively narrow subsequently analysed. The resulting velocities were pressure range. However, the absolute size of meas• compiled in a normalized histogram, which was fitted ured and calculated velocity is significantly different, by a normal (Gaussian) distribution (correlation coeffi• and the measurement location should have been cient > 0.97). The mean of the distribution is given by closer to the nozzle exit. Calculations for higher pres• -4.5±0.5 m/s and the standard deviation by sures indicate the existence of a re-circulation zone 16.4±0.4 m/s. The low absolute values of the velocity further downstream. together with the clear presents of a local flow com• The size of the re-circulation zone is associated with ponent with a direction opposite to the main flow indi• the reattachment of the separated flow to the nozzle cate the existence of a re-circulation zone. wall, inducing shocks and expansion waves that result The constraint on the selection of the peaks, required in wall pressure peaks with values above ambient to determine the flow velocity, is that their frequencies pressure. Our findings also agree with earlier per• formed side-load measurements because they explain obey the relation Q0 = + Q2. Figure 1 depicts the power spectrum of a single-shot measurement taken the appearance of a pronounced peak of the side-load at about 10 bar. at 10 bar. The two most prominent lines are assigned to the frequencies Qi and Q2 corresponding to a flow velocity of -17.4 m/s. However, as indicated in Fig• 4 ACKNOWLEDGEMENTS ure 1 there are other combinations of peaks that fulfil The authors are indebted to M. Oschwald, W. Clauss, the required constraint. A smaller frequency difference Ch. Böhm, D. Klimenko, W. Kwan, and R. Stark for corresponds to a smaller velocity and vice versa. their continuous support during the measurements in Thus, velocities between 131.0 m/s and -87.6 m/s are Lampoldshausen and during the analysis of the data. measured. A possible explanation of this observation Particular thank is addressed to P. Radi for writing the could be that the grating is segmented by density data acquisition software. Financial support by the gradients, and that these segments move with differ• Swiss Federal Office of Energy (BFE) is gratefully ent velocities. acknowledged. 62 SIDE REACTIONS IN THE SELECTIVE CATALYTIC REDUCTION OF NO WITH NH3 G. Madia, M. Koebel, M. Elsener, A. Wokaun The main and the side reactions of the SCR reaction with ammonia over Ti02-W03-V205 catalysts have been investigated using synthetic gas mixtures matching the composition of diesel exhaust. At high tem• peratures the selective catalytic oxidation of ammonia (SCO) and the formation of nitrous oxide compete with the SCR reaction. Water strongly inhibits the SCO of ammonia and the formation of nitrous oxide thus increasing the selectivity of the SCR reaction. However, water also inhibits SCR activity, most pronounced at low temperatures. 1 INTRODUCTION reactions (2)-(5) is usually observed. The experimen• tal signs of this are formation of N20 and consumption The Selective Catalytic Reduction (SCR) of nitrogen of ammonia in excess to the stoichiometry of the SCR oxides by ammonia is a highly developed and wide• reaction (1). With standard analyzing procedures the spread technology for the removal of NOx from sta• contributions of reactions (3) and (5) cannot be de• tionary sources. Moreover, this technique using urea termined. as a toxicologically and environmentally safer reduc• ing agent is presently considered as the most promis• 2 EXPERIMENTAL ing technique to remove NOx from lean exhaust gases of mobile diesel engines [1]. The experiments were performed in a flow-trough reactor (gas flow 380 lN/h). The test feed used was The reduction of nitric oxide with ammonia or other N- adapted to a typical diesel exhaust gas, containing 10 containing reducing agents by SCR is generally con• % 02, 5 % H20 with balance N2 and 300 ppm NO and sidered to be highly selective. The term "selective" NH3 each. A second series of experiments was made refers primarily to the oxidizing educts of the reduc• using the same feed without water. The gases at the tion: NO shall be reduced by NH3 in preference to 02, reactor outlet were analysed by means of an FTIR the latter being present in lean exhaust gases in much spectrometer. higher amounts. However, the term "selective" also 3 refers to the products. Elementary nitrogen (and wa• 7.3 cm of a ternary catalyst composed of Ti02, V205 ter) is the desired product of the DeNOx process, but and W03 was used in the form of a monolithic sample the formation of higher oxidized nitrogen species like resulting in a GHSV of 52,000 Ir1. Further details have N20, NO and N02 cannot be excluded. The following been given in [2]. reactions should be considered when discussing the SCR reaction: 3 RESULTS 4 NH3 + 4 NO + 02 -» 4 N2 + 6 H20 (1) The NOx-conversion ("DeNOx") was calculated ac• cording to: 4 NH3 + 4 NO + 3 02 -» 4 N20 + 6 H20 (2) NO(in)-NO(out) DeNOx = (6) 4 NH3 + 3 02 -» 2 N2 + 6 H20 (3) NO(in) 4 NH3 + 4 02 -> 2 N20 + 6 H20 (4) Various authors, e.g. Okzan et al. [3], have shown by isotope experiments that the formation of N20 pro• 4 NH3 + 5 02 -» 4 NO + 6 H20 (5) ceeds mainly according to reaction (2) and not ac• Reaction (1) is the SCR reaction. It has a 1/1 cording to (4). Therefore, considering the stoichiomet• stoichiometry for NHg/NO. Reaction (2) has the same ric factors of NH3, NO and N20 in equations (1) and NHs/NO stoichiometry but consumes more 02 thus (2), the selectivities have been defined as follows: yielding the higher oxidized, undesired product nitrous oxide. Reactions (3) to (5) represent the oxidation of NO reduced 'SCR (7) ammonia by oxygen. It is evident that the formation of NH3 consumed increasingly oxidized products of nitrogen N2, N20 and NO is accompanied by an increase of the N20 formed ,N20 (8) stoichiometric ratio 02/NH3. NH3 consumed When an SCR catalyst is tested at increasing tem• The results were evaluated according to these equa• peratures, a decreasing SCR selectivity due to side tions and are presented in Figures 1 and 2. 63 100 o ; At 450°C the sum of both selectivities is clearly lower than 100% suggesting that NH3 is oxidized by another 80 reaction, which we attribute to reaction (3), the so- 0" called Selective Catalytic Oxidation (SCO). This ex• E 60 "" planation is supported by the results of additional ex• periments carried out without NO in the feed. These d -O - DeNOx dry experiments have revealed that the oxidation of NH3 -•— DeNOx humid I 40 with 02 according to reaction (3) is very slow. For further details the reader is referred to the original 20 + publication [4]. This paper treats the aspects of selec• tivity also for gas mixtures containing N02, thus con• 200 250 300 350 400 450 sidering the fast SCR reaction (N02/NO = 1/1) and the T [°C] N02-SCR reaction (NOx = N02). 1 Fig. 1 : NOx conversion at GHSV = 52000 h" for dry Dry feed: The SCR selectivity begins to decrease at and humid feeds. much lower temperatures than in the case of a humid gas. At the same time the selectivity for N20-formation 120 starts to rise and reaches values of =35 % already at 400°C. Therefore, the main byproduct at intermediate loo • temperatures seems to be N20 formed by reaction (2). 80 At 450°C considerable amounts of N2 must be formed -•—SCR. humid by SCO of ammonia (3), because the sum of both -Q - SCR, dry 60 •A- • N20. dry selectivities is below 100%. -A— N20. humid en 40 It should be noted that the simple definitions for selec• tivity (7) and (8) come to their limits, if one considers 20 their sum at intermediate temperatures. This sum amounts to >100% at 350°C. This is due to the fact 0 4— that NO consumed in reaction (2), i.e. N20 formation, 200 250 300 350 400 450 will cause an overestimation of SScr- The value of 107 T [°C] % of SSCRnumid at 200°C is due to experimental uncer• Fig. 2: Selectivities of SCR and N20 formation at tainties at this temperature. GHSV = 52000 h"1 for dry and humid feeds. 4 CONCLUSION NOx Conversion (Figure 1) The conversions for both dry and humid feeds show a The selectivity of the SCR reaction is high at low to flat maximum of practically 100 % at intermediate intermediate temperatures, but starts to decrease temperatures. This maximum is due to the decreasing distinctly at high temperatures. The main side reac• SCR-activity at low temperatures and the decreasing tions are the formation of nitrous oxide by reaction (2) SCR selectivity at high temperatures. This maximum and the SCO of ammonia to nitrogen (3). is located at lower temperatures in the case of the dry Water decreases the SCR activity of the catalyst. feed indicating a higher activity than in the case of the However, water increases the SCR selectivity and this humid feed. In the case of the humid feed the useful effect is highly valuable in the practical application of maximum range is 300-400°C. Beyond =400°C a the SCR process to exhaust gases. rapid decline of DeNOx is observed in the case of the humid feed. This decline starts already at =300°C in case of the dry feed. 5 REFERENCES The general conclusion from these results is that wa• [1] M. Koebel, M. Elsener, M. Kleemann, Catal. To• ter inhibits the SCR reaction. Since exhaust gases day 2031 (2000), 1-11. typically contain several percent of water, realistic conditions are those for a humid feed. [2] M. Koebel, M. Elsener, G. Madia, Ind. Eng. Chem. Res. 40 (2001), 52. Selectivities (Figure 2) Humid feed: The selectivity for the SCR reaction re• [3] U.S. Ozkan, Y. Cai and M.W. Kumthekar, J. mains at roughly 100 % over a wide range (200- Catal. 149 (1994), 390-403 400°C). This corresponds to a low N20 selectivity. [4] G. Madia, M. Koebel, M. Elsener, A. Wokaun, N20 formation gets perceptible only at temperatures Ind. Eng. Chem. Res., to be published. above 400°C. 64 INVESTIGATION OF THE OXIDATION OF NO OVER PLATINUM CATALYSTS J. Despres, M. Koebel, M. Elsener, A. Wokaun The oxidation of NO to N02 over Pt/Si02 was investigated in the temperature range 150-450°C. Powdered catalysts were prepared by incipient wetness impregnation, followed by calcination and reduction. The feed gas typically contained oxygen, nitrogen monoxide, water and nitrogen. The concentration of NO in the feed was varied at constant concentration of 02 in order to study its influence on the reaction. A de• crease of the conversion with increasing concentration of NO was observed. A similar study was per• formed with various oxygen concentrations at constant concentration of NO. Oxygen involved in the sur• face reaction originates from the dissociative chemisorption of02 on the platinum surface. 1 INTRODUCTION BaO + 3 N02 -> NO + Ba(N03)2 (5) The removal of nitrogen oxides, soot, carbon monox• 3 GAS-PHASE EQUILIBRIUM ide and hydrocarbons from exhaust gases is a major topic of environmental catalysis. N02 plays an Figure 1 shows the thermodynamic stability of N02 as increasing role in advanced exhaust gas aftertreat- a function of temperature for various partial pressures ment techniques. Therefore, we are investigating the of 02. N02 is stable at low temperatures. At tempera• catalytic oxidation of NO to N02 over platinum cata• tures above 200°C, N02 dissociates into NO and 02. lysts in lean conditions: High P(02) increases the stability of N02. 1 NO + /202 -> N02 (1) I 2 N02: A KEY MOLECULE IN EXHAUST GAS -m- P(02) = 0.3 bar -»- PÍ02 = 0.2 bar AFTERTREATMENT TECHNIQUES -*-P(02 =0.1 bar -•- PÍ02 = 0.05 bar -*- P(02 = 0.01 bar The major part of NOx emitted by diesel engines con• sists of NO (95%). Selective catalytic reduction (SCR) using ammonia as a reducing agent is the most prom• ising process for removing NOx from lean exhaust V gases. A possible way to achieve a high DeNOx at low temperatures is to oxidize a part of NO to N02 over a platinum catalyst positioned upstream of the SCR catalyst. An ideal NOx mixture contains 50% NO and 50% N02 and reacts according to reaction 2, with 0 200 400 600 800 1000 a faster rate than the standard SCR reaction 3 [1]: T[°C] 4 NH3 + 2 NO + 2 N02 -» N2 + 6 H20 (2) Fig. 1 : Thermodynamic gas-phase stability of N02 for 4 NH3 + 4 NO + 02 -» N2 + 6 H20 (3) various partial pressures of oxygen. Another exhaust-gas cleaning process utilizes the better oxidizing properties of N02 compared to 02. For 4 EXPERIMENTAL example, the continuously regenerating trap (CRT) for soot removal from diesel exhaust gases utilizes an A catalyst sample containing 2.5 % Pt on Si02 was oxidation catalyst (Pt on alumina) positioned upstream prepared by incipient wetness impregnation using of a soot trap [2]. N02 generated by the oxidation Pt(NH3)4CI2 as precursor. The powder was calcined at catalyst oxidizes soot according to reaction 4, thus 300°C for 2 hours, and finally reduced at 450°C in 5% regenerating continuously the filter. The presence of H2/N2 for 1 hour. Figure 2 shows a TEM micrograph of N02 reduces the temperature of soot oxidation from the fresh sample. The platinum particle size was ~550°C to values below ~350°C: about 15 nm, corresponding to a low dispersion of Pt. The oxidation of NO was investigated in a microreac• C + 2 N02 -» 2 NO + C02 (4) -1 tor with 0.8 g Pt/Si02 at a gas flow rate of 150 l-h . N02 also plays a key role in the adsorption of NO over Analysis of the gases was achieved by infrared spec• NOx storage catalysts, e.g. Pt/BaO/AI203. The reac• troscopy. More details are given in [1]. Between suc• tion mechanism involves the oxidation of NO to N02 cessive oxidation tests, we observed a deactivation of over platinum as a first step [3] and the reaction of the catalyst. However, the initial activity could be re• N02 with the barium oxide to form Ba(N03)2 according covered by treating the sample for 1 hour at 650°C. to reaction 5: 65 Influence of 02 (Figure 4) Between 150°C and 300°C, we observed an increase of the conversion of 500 ppm NO with increasing con• centrations of 02. However, above 10% 02 in the feed, the conversion remains almost constant. Above 300°C, the conversion is limited by the thermody• namic equilibrium (Figure 1). Results obtained at low temperatures, i.e. in the kinetically controlled region, reflect a saturation effect with increasing oxygen feed concentration. Platinum is able to chemisorb oxygen dissociatively, even at room temperature, according to the following reaction: O2 (gas) -> 2 Oads (6) The capability of platinum to split small molecules like H2 or 02 has also been claimed for the dissociation of Fig. 2: TEM micrograph of a fresh Pt/Si02 catalyst. N02 on model Pt(111) surfaces [4]. Although platinum supported on SiÖ2 is expected to remain in the ele• 5 RESULTS mentary (metallic) state even in a feed containing oxy• gen, we could expect the change of its oxidation state Influence of NO (Figure 3) during the experimental test. The strong oxidizing Figure 3 shows the influence of the NO feed concen• properties of N02 might even lead to the formation of tration on the conversion with a feed containing 10% a platinum oxide layer around a Pt core. 02 and 5% H20. The conversion depends strongly on the concentration of NO in the feed. At 200°C, the 6 CONCLUSION conversion of 100 ppm NO is 55%, whereas it falls to 12% with 1000 ppm NO. At higher NO concentration, Experimental tests have shown a decrease of the the conversion remains constant. conversion with increasing feed concentrations of NO. Further studies (XPS, DRIFTS) will be performed in I order to obtain a better understanding of the reaction Equilibrium • 100 ppm NO mechanism and of the deactivation process. —•— 500 ppm NO * 1000 ppm NO x 1500 ppm NO 7 ACKNOWLEDGEMENTS We thank the Swiss Federal Office of Energy for fi• nancial support. The authors are grateful to R. Schaeublin and S. Abolhassani for TEM measure• ments and fruitful discussions. 8 REFERENCES 100 200 300 400 500 600 T[°C] [1] M. Koebel, M. Elsener, G. Madia, Reaction Path• ways in the SCR Process with NO and N02 at Fig. 3: Influence of NO on the conversion. 0.8 g Low Temperatures, Ind. Eng. Chem. Res. 40, 52 Pt/Si02, 150 yh, 10% 02, 5% H20, balance N2. (2001). I -•-30% 02 [2] US Patent 4902487 (1990), Applicant: Johnson -•-20% 02 -*-10%O2 Matthey. -•-5% 02 -*-1%02 -1-0.1% 02 [3] N. Takahashi, H. Shinjoh, T. lijima, T. Suzuki, K. Yamazaki, K. Yokota, H. Suzuki, N. Miyoshi, S. Matsumoto, T. Tanizawa, T. Tanaka, S. Tateishi, K. Kasahara, The New Concept 3-Way Catalyst for Automotive Lean-Burn Engine: NOx Storage and Reduction Catalyst, Proceedings of the 1st World Congress Environmental Catalysis, Pisa, 45 (1995). 100 200 300 400 500 600 T[°C] [4] J. Segner, W. Vielhaber, G. Ertl, Interaction of Fig. 4: Influence of 02 on the conversion. 0.8 g N02 with a Pt(111) Surface, Israel J. Chem. 22, Pt/Si02, 150 lis/h, 500 ppm NO, 5% H20, balance N2. 375 (1982). 66 67 Electrochemistry 68 LABORATORY FOR ELECTROCHEMISTRY Otto Haas The Laboratory for Electrochemistry is dedicated to logy transfer-projects to industry. The Zinc/Air Bat• modern aspects of electrochemical energy storage teries project made a successful technology transfer and conversion. The aim of our research is the devel• to a German company ZOXY and a final report to its opment of novel batteries, fuel cells, and capacitors EU-project manager. for electric vehicles, portable devices, and on-site load In the field of lithium-ion batteries a new, safe, and levelling. In addition, the Laboratory for Electrochem• inexpensive layered insertion oxide for positive elec• istry provides expertise and innovative solutions in the trodes was developed jointly with the Laboratory for fields of batteries, fuel cells, supercapacitors, elec• Inorganic Chemistry at ETHZ. The technology has trolysis, electrocatalysis, electrochemical material been successfully transferred in 2001 to the company science, and modern methods for electrochemical Ferro GmbH in Frankfurt/Main. Together with PSI the interface analysis. Our activities are partly supported production process is now scaled up and the oxide will by the Swiss Federal Office of Energy (BFE), the be offered commercially soon. Another very success• Commission for Technology and Innovation (CTI), the ful industrial collaboration of the Lithium-Ion Battery Swiss National Science Foundation (NF), the Board of group is that with the Swiss company TIMCAL SA with the Swiss Federal Institutes of Technology (BSIT), as the aim of understanding and improvement of syn• well as various industrial partners. thetic graphites for lithium-ion batteries. The main projects of the laboratory are The Characterisation / Catalysis projects was focused • Fuel Cells on several aspects of heterogeneous catalysis and surface reactions investigated by analytical in-situ • Lithium-Ion Batteries methods. In addition first measurements at the Sur• • Zinc/Air Batteries face and Interface Microscopy (SIM) beamline at the SLS were performed. In collaboration with the Nuclear • Supercapacitors Energy and Safety Department corrosion phenomena • Materials Development and Characterisation of stainless steel under Boiling Water Reactor (BWR) conditions were studied. The main activities of the fuel cell and supercapacitor project in 2001 were contributions to the BRESA- The main activities of the Materials Development / Project where six 8 kW fuel cell stacks and two 30 kW Ablation project are focused on studies of thin crystal• supercapacitor modules had to be built and integrated line films of electrocatalyst (oxides), which are pre• in the power system of the fuel cell supercapacitor pared by pulsed laser deposition (PLD). In another hybrid vehicle. The battery projects were both much project the structuring of glassy carbon for model- engaged with contributions to EU-projects and techno• micro fuel cells is studied. 69 LaCo03 PEROVSKITE, A NEW COBALT REFERENCE FOR EXAFS INVESTIGATIONS O. Haas, R.P.W.J. Struts, J. McBreen (Brookhaven National Laboratory USA) LaCo03 perovskite was investigated via EXAFS and XRD measurements. The Fourier transform of the extended X-ray absorption spectrum was simulated using the FEFF8 ab initio XAFS code, which simulates the contributions of the different scattering paths to the EXAFS spectrum. LaCo03 is a well characterized perovskite and therefore constitutes an interesting reference for data interpretation of related compounds such as Lai.xCaxCo03 and Lai.xSrxCo03, which are important compounds used in energy technology. INTRODUCTION RESULTS AND DISCUSSION Cobalt oxides, and particularly cobaltates with XRD Results and Structure of LaCo03 The XRD re• perovskite structure, are endowed with interesting sults of the LaCo03 powder are shown in Figure 1. catalytic, ion-conduction, magnetic, and semiconduct• ing properties. LaCo03 for instance exhibits catalytic activity above 700 °C, where CO can be oxidized and LaCo03 NOx decomposed!"!]. La^CaxCoOs can be used in 800 bifunctional porous oxygen diffusion electrodes as a catalyst to reduce and to evolve oxygen[2], while Lai_ 600 in „ „„ xSrxCo03 is widely used as an oxygen-ion-conducting g 400 and electron-conducting electrode material in high [018] [220] [208] temperature fuel cells[3]. - 200 / \/ P121; Synchrotron x-ray absorption spectroscopy is a very useful tool to investigate the electronic properties and 20 30 40 50 60 70 structure of these compounds. In many cases it even 2Theta offers the possibility for in-situ investigations during ongoing processes. Information about the valence state and electron configuration of cobalt can be ob• Fig. 1 : Powder X-ray diffraction pattern of LaCo03 tained from the XANES region, while the EXAFS re• prepared by the citrate-precursor method. gion offers structural information about nearest- neighbour atoms and geometrical arrangement They are in good agreement with published X-ray dif• around the absorbing atom. fraction data of this compound [4]. In a more recent neutron diffraction study [5] the crystal structure has 2 EXPERIMENTAL been classified with the space group R-3C (with index X-ray absorption was measured on beam line X-11A #167 in the International Tables of Crystallography). of the National Synchrotron Light Source (NSLS) at The coordinates of the La, Co, and O atoms having Brookhaven National Laboratory (BNL) with the stor• Co in the origin are listed in Table 1. age ring operating at 2.52 GeV beam energy and with beam currents between 340 mA and 140 mA. A Atom / M (Wy) * X Y Z Si(111) double-crystal monochromator was used for energy selection. The intensities of the incident and La / 2 (a) 0.25 0.25 0.25 transmitted X-rays were monitored by nitrogen-filled Co / 2 (b) 0.00 0.00 0.00 ionization chambers. O / 6 (e) 0.1982 0.3018 0.75 X-ray diffraction data were obtained using a Philips X- (* M=Multiplicity; Wy=Wyckoff letter) Pert Diffractometer with Cu Ka radiation. Table 1 : Coordinates of the elements in LaCo03. The perovskite catalyst was prepared by calcination of Figure 2 shows the raw Co K-edge EXAFS Spectrum citric La, Ca, and Co precursor salts at 700 °C, as pre• of LaCo03. The normalized, background-subtracted viously described [2]. and k3-weighted Co EXAFS spectrum is shown in Samples for the X-ray absorption measurements were Figure 3, while its Fourier Transform (Bessel function prepared by mixing the pure perovskite powder with weighted) provides the radial structure function plotted BN (1 : 5) and compressing this diluted sample to a in Figure 4. Figures 3 and 4 also show FEFF simula• pill. The samples were fixed to an adequate sample tion fit results for the first and second scattering shells holder and brought into the X-ray beam. (see below). 70 tion mentioned. Taken together with the crystal data, we obtained an almost perfect fit of the EXAFS spec• trum and its Fourier transform by using the most im• portant scattering paths indicated in Table 2. The FEFF parameters used to fit the EXAFS k3x(k) Fourier transform shown in Figure 4 are listed for the most important scattering paths in Table 2. FIT RESULTS S.G.= R-3C(#167) photon energy [keV] Path CN* R a2 AEo Fig. 2: Raw Co K-edge EXAFS spectrum of LaCoQ3. Co-0 6 1.925 4.67 1.66 Co-La 2 3.273 7.19 -6.25 Co-La 6 3.316 8.20 -5.75 Co-Co 6 3.826 7.21 2.61 Co-O-Co (MS) 12 3.826 6.78 -5.12 (*= Fixed in fit; MS=Multi-scattering) Table 2: Structural parameters of LaCo03 sample derived from Co-EXAFS analysis: Phase shifts (AE0, eV), Interatomic distances (R, Á), Coordination num• bers (CN), and Debye-Waller factors (a2, Á2.10"3). k [A"1 ] The fitted interatomic distances differed by less than Fig. 3: Normalized, background-subtracted and k3- 0.01 Á from the crystallographic data. The Debye- weighted Co EXAFS spectrum of LaCo03. Drawn Waller factors, a2, all below 0.01, indicate low thermal curve represents fitted results through the experimen• disorder in the sample. tally derived data points (o). 4 CONCLUSION 0.15 "T—;—i—j—¡—r~~f~~~r~~~r~Y~~r~~~r~~~¡—r~~~¡—i—i—i—i- The X-ray diffraction data of LaCo03 perovskite are Co-0(6x) |A\ . Co-0-Co(12x) helpful for an accurate simulation of EXAFS spectra of this compound and their Fourier transforms. The O.I FEFF fitting parameters obtained will be good starting values for the simulation of spectra of technically im• 0.05 portant related perovskites such as Lai.xCaxCo03 and La^S^Cou^ o.o 5 REFERENCES [1] R.J.H. Voorhoeve, Advanced Materials in Cataly• sis; Academic Press: New York, (1977), W.F. Fig. 4: Radial structure function from Fourier Trans• Libby, Science, 171, 499-500 (1971). formation of k3%(k) shown in Figure 3. Also shown are fitted shell contributions as discussed in the text. [2] S. Müller, K.A. Striebel, O. Haas, Electrochim. Acta, 39, 1661 (1994). The Fourier transform was performed using the k- space range between 5.0 and 11.6 A"1. It shows two [3] M.H.R. Bouwmeester H. Verweij, Solid State strong and well-defined peaks and two weaker, more Ionics 96, 21, (1997). structured peaks at higher interatomic distances. The [4] A. Wold, B. Post and E. Banks, J. Am. Chem. peak positions are close to the radius of the back- Soc. 79, 6365 (1957). scattering shells. However, to obtain the correct radius of the shells, the data have to be amplitude and phase [5] G. Thornton, B.C. Tofield, and A.W. Hewat, J. corrected. This can be done using the FEFF8 simula• Solid State Chemistry 61, 301-307 (1986). 71 THE INFLUENCE OF SURFACE MODIFICATIONS ON THE ELECTROCHEMICAL LITHIUM INSERTION PROPERTIES OF HEXAGONAL GRAPHITE P. Novák, M.E. Spahr (TIMCAL SA), H. Wilhelm (TIMCAL SA), F. Joho, J.-C. Panitz, J. Wambach, N. Dupont-Pavlovsky (University of Nancy, France) In lithium-ion batteries, hexagonal graphite shows very high irreversible capacity due to co-insertion of solvent molecules and exfoliation of the graphite structure. An oxidation of the graphite preserves its purely hexagonal crystal structure, however, the irreversible capacity decreases gradually with the oxidation tem• perature. Surface analyses indicated surface curing effects - the amounts of prismatic surfaces, low energy defects located on the graphite basal planes, disordered carbon on the graphite particle surface as well as the superficial oxygen concentration decreased as a result of the heat treatment. The results indicate that not the graphite crystal structure but the surface properties are the responsible parameters for the irre• versible capacity of graphite in lithium-ion batteries. 1 INTRODUCTION weeks in inert gas at 3000 °C. This heat-treated graphite was subsequently oxidized in a rotating tube In the development of rechargeable lithium-ion batter• furnace at 450 °C, 600 °C, and 800 °C, respectively. ies, highly crystalline graphites have attracted consid• The graphite was characterized by scanning electron erable attention recently. For such graphites, a re• microscopy (SEM), X-ray diffraction (XRD), X-ray pho- versible charge capacity of up to 372 mAh/g can be toelectron spectroscopy (XPS), Raman microscopy, obtained [1]. This reversible capacity corresponds to nitrogen and krypton gas adsorption measurements as the chemical composition LiC6 of the graphite interca• well as by standard electrochemical techniques follow• lation compound formed in the graphite negative elec• ing established procedures. trode during lithium insertion. The high degree of graphitization present in these carbon materials leads to their typical texture, porosity, and surface morphol• 3 RESULTS ogy. All these materials parameters are likely to be The sample SLX50 shows the typical electrochemical related to electrochemical parameters such as re• properties of graphite (Figure 1). The electrochemical versible charge capacity, first charge efficiency, as Li+ insertion process occurring at potentials below 200 well as rate capability of graphite negative electrodes. mV vs. Li/Li+ produces a step-shaped potential-time curve indicative for formation of the lithium graphite However, the key electrochemical parameter used intercalation compounds. Between 800 mV and 200 when selecting graphites suitable for negative elec• mV vs. Li/Li+ the SEI layer is formed giving rise to an trode materials is the irreversible capacity measured irreversible capacity of 25 mAh/g. The specific BET 2 during first electrochemical Li+ insertion. This irre• surface area of this graphite was found to be 4.0 m /g. versible capacity is due to formation of the solid elec• trolyte interphase (SEI) layer on the graphite particle surface by electrolyte decomposition. This layer then prevents further electrolyte decomposition [2]. This SEI formation concerns all of the graphite's surface area, which in addition to the geometrical particle sur• face includes the areas associated with the graphite's porosity and superficial roughness. Apart from surface area, the graphite's crystal structure has also been revealed as a factor for charge loss during first lithium insertion [3]. Thus, both the graphite's crystal structure and its surface morphology should be optimized in order to obtain the most effective SEI formation, and it will be necessary to understand the individual influ• ence of structural defects (rhombohedral stacking faults) and surface defects on the irreversible capacity. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Such studies require a characterization of samples x in LLC having a single crystalline phase, i.e., a purely hex• A 6 agonal graphite. We therefore investigated the crystal Fig. 1 : First galvanostatic insertion/de-insertion of Li+ structure, porosity, surface morphology, and electro• in graphites SLX50 and SLX50 heat-treated at 3000 chemical properties of such a graphite material before °C in inert gas. Curves recorded using 1 M LiPF6 in and after a progressive surface oxidation treatment. EC:DMC (1:1) as an electrolyte and a specific current of 10 mA/g. 2 EXPERIMENTAL Heating the SLX50 to 3000 °C in inert gas for several The purely hexagonal graphite was prepared by heat- days caused the crystallite size to increase, as re• treating synthetic graphite TIM REX® SLX50 for 2 vealed via XRD experiments. The specific BET sur- 72 face area decreased to 2.8 m2/g during the heat 1.00 treatment, yet the irreversible capacity measured dur• ing first Li+ insertion into SLX50 significantly increased upon heat treatment. An additional plateau due to co- insertion of solvated Li+-ions appeared at a potential of about 450 mV vs. Li/Li+ (Figure 1). The tendency to• wards solvated lithium ion co-insertion and graphite exfoliation is typically observed during electrochemical Li+ insertion into graphite materials having a smaller number of rhombohedral defects [3]. Thus, we hy• pothesized that the rhombohedral stacking defects of SLX50 were healed during the heat treatment. The results of XRD experiments shown in Figure 2 confirm this hypothesis. x in Li C x 6 Fig. 3: First electrochemical insertion/de-insertion of c heat-treated graphite SLX50 before and after progres• sive oxidation in air. Curves recorded using a constant current of 10 mA/g. TJ N From the results of Raman spectroscopy (Figure 4) « we conclude that the oxidation reaction increases the o.o E disorder on the graphite surface. Moreover, more sub• tle differences seen in Raman spectra might reflect SLX50 O changes in oxygen content at the surface. SLX50(HT) 41 42 43 44 45 46 47 48 SLX50(HT)ox. G-band 20 Fig. 2: XRD pattern of graphite SLX50 and heat- treated SLX50 before and after oxidation at 800 °C. H: hexagonal modification; R: rhombohedral modifi• cation. However, the electrochemical Li+ insertion properties of the heat-treated hexagonal SLX50 which was pro• gressively oxidized in air were not fully consistent with 1200 1275 1350 14251500 1575 1650 the above model. Thus, Figure 3 shows that the po• Wavenumber / cm"1 tential plateau at 450 mV vs. Li/Li+ gradually disap• Fig. Raman spectra of graphite samples. (A) peared with increasing oxidation temperature. When 4: SLX50, as received; (B) SLX50 after high temperature subsequently oxidized at 800 °C, the heat-treated treatment and subsequent oxidation at 800 °C; (C) SLX50 showed no further evidence of an exfoliation of SLX50 after high temperature treatment. The D-band the graphite structure during first electrochemical Li+ intensities are plotted on a 10 times larger scale (left- insertion. But according to the XRD pattern seen in hand-side intensity scale). Intensities are normalized Figure 2, the purely hexagonal structure of the graph• with respect to the maximum of the G-band. ite samples could actually be maintained during the oxidation reaction. Therefore, we conclude that the In the XPS spectra, the following trends were ob• same electrochemical properties of a graphite powder served: During heat treatment of the SLX50 the can be obtained with and without a certain fraction of amount of oxygen on the graphite surface significantly rhombohedral stacking faults in the hexagonal crystal decreased. During subsequent oxidation, it increased structure. Obviously the treatments affected the sur• again. SEM pictures of the heat-treated SLX50 face morphology of the graphite and, thus, influenced showed a highly ordered graphite surface (Figure 5, its electrochemical properties. top). Graphite subsequently oxidized exhibits in- 73 creased surface roughness, particularly at the crystal• samples show that heat treatment of the starting lite edges (Figure 5, bottom), which results in a higher SLX50 leads to a significant loss of polar edges and BET specific surface area (4.0 m2/g) as compared to low-energy defects, i.e., to a healing of defects on the the hexagonal graphite before the oxidation treatment graphite surface. The oxidation treatment does not (2.8 m2/g). affect the proportion of low energy defects but directly transforms basal planes into polar edges. The propor• Krypton adsorption provides a much more sensitive tion of the latter is doubled between the heat-treated response in the analysis of sample surface morphol• starting material and the sample oxidized at tempera• ogy than the nitrogen adsorption used to determine tures above 600 °C. The fraction of polar edges might the specific BET surface area. On a graphite surface, have an influence on the electrochemical properties adsorbing krypton yields a step-shaped isotherm in observed, particularly for the formation of an effec• which each step corresponds to the adsorption of one tively passivating SEI layer. This could suppress the individual monolayer of krypton atoms (Figure 6). The co-intercalation of solvated Li+-ions. However, on a first step yields information concerning the superficial surface having a larger amount of prismatic surfaces characteristics of graphite, notably its specific surface one also finds a larger number of surface groups satu• area, as well as the relative amounts of the different rating the free valences of the terminal sp -carbons at types of adsorption sites. The results for SLX50 before the polar edges. The chemistry of the surface groups and after the heat treatment as well as for the oxidized is also affected by the different surface treatments. 3 Vads (cm TPN) expanded graphite i f". ; low-energy defects > V l < heterogeneous graphite basal planes > K polar edges L f „ 0 10"3 3 10"2 Fig. 6: Schematic illustrating the isotherms expected for the first monolayer of krypton adsorbing on ex• panded graphite and on a polycrystalline graphite pow• der. 4 ACKNOWLEDGEMENTS The assistance provided by Dr. B. Ketterer, PSI, in the SEM work is gratefully acknowledged. Parts of this work were supported by the European Community and the Swiss Federal Office of Energy. 5 REFERENCES [1] M. Winter, J. O. Besenhard, M. E. Spahr, and P. Novak, Adv. Mater. 10, 725 (1998). [2] E. Peled, D. Golodnitsky, J. Pencier, in Handbook of Batteries, J. O. Besenhard, Editor, Ch. 6, Wiley-VCH, Weinheim (1999). Fig. 5: SEM pictures of heat-treated graphite TIMREX® SLX50 (top) and heat-treated SLX50 after [3] S. Flandrois and B. Simon, Carbon 37, 165 subsequent oxidation at 800 °C in air (bottom). (1999). 74 50 KW SUPERCAPACITOR MODULE FOR THE BRESA PROJECT M. Bärtschi, S. Müller, R. Kötz, R. Gallay (Montena Components S.A.), A. Schneuwly (Montena Components S.A.), V. Hermann (Montena Components S.A.) A supercapacitor (SC) module for a hybrid electrical drive train was realised, consisting of282 single cells (2 cells in parallel and 141 units in series) and voltage balancing-electronics. The rated voltage was 360 V and the series resistance 113 m£2. The module delivered a power of 50 kW for 15 seconds, which results in an energy content of 210 Wh. 1 INTRODUCTION ments of the car. Furthermore the boxes where equipped with a cooling system consisting of fans and In electrical vehicle propulsion hybrid drive trains were air distribution channels where required. intensively studied in the last few years. The fully elec• trical concept consists of a constant power source e.g. fuel cell or battery and a peak power source e.g. su• percapacitor (SC) [1]. With the hybrid concept the system is able to supply the needed peak power from the supercapacitor for acceleration processes al• though the constant power source is scaled down to deliver only the average needed power, which leads to smaller and lighter traction systems. In addition, supercapacitors allow energy recuperation from breaking processes, which can lead to energy savings of up to 25 % [2], and results in an increased mileage of the vehicle. In preceding work [3] a scaled-down drive train system Fig. 1 : The fully assembled SC-modules in their stor• consisting of a 6.5 kW fuel cell, a 60 V, 60 F superca• age boxes, the front module at the right and the rear pacitor module and the appropriate power electronics module at the left. were tested with a modified driving cycle. It was dem• onstrated that a supercapacitor is an efficient energy 2.2 Measurements storage device in vehicle applications for boosting To measure the series resistance (Rs) of the SC- peak power and recuperating braking energy. module, it was charged to approximately 200 Volts, and subsequently discharged with a resistance. The 2 EXPERIMENTAL voltage jump and the corresponding current were re• corded at the moment the resistance was discon• 2.1 Assembly nected. With use of the Ohms law the value of Rs could be calculated. The SC-module was assembled out of 282 single To measure the energy content and the power of the cells, which were connected pair wise to a 141 series module, a constant power supply or demand were connection (70 pairs in series for the front box and 71 generated by the dynamic test bed and the electrical pairs in series for the rear box, see also Figure 1). In motor to charge or discharge the capacitors between order to minimize interface corrosion effects between half (180 V) and full (360 V) rated voltage. The current the electrical contact and the capacitor, aluminium and the voltage during this constant power charge/ bars were chosen for the electrical connectors. Con• discharge process were recorded with an oscillo• tact resistance turned out to be higher when using scope. With aid of the recorded information the termi• different metals e.g. copper contacts on aluminium nal power of the module and the energy content for capacitor mounts [4]. To meet the given target for the the respective power could be calculated. series resistance it was necessary to treat all contact surfaces to remove the insulating oxide layer and to To verify the thermal properties of the module and its increase the contact area. A supplementary balancing cooling system, the module was equipped with 7 semi• electronic circuitry was mounted to equilibrate the cell conductor temperature sensors then the storage voltages inside the SC-module. boxes were closed and the module was charged and discharged with a 30 kW load (corresponding to a The capacitor modules where mounted into metal charge-/discharge-time of 30 seconds) generated from housings, shaped according to the space require• the test bed and the electrical machine. Between 75 charging and discharging a break of 30 seconds was maintained (50 % duty-cycle). The Capacitor was cy• 30 kW, 50 % duty cycle no cycling cled for 2700 seconds, then the module was allowed to cool down without further cycling. All measurements were carried out at the ETH Zürich in the engine Laboratory on a dynamic test bed. 3 RESULTS 3.1 Physical properties i i i i i I ' I ' The total mass of the module was 168 kg, made up of 0 1000 2000 3000 4000 Time / s 110 kg Supercapacitor-cells, balancing electronic and electrical contacts and 58 kg for the metal housings, Fig. 3: Measured temperature curves in the SC - contactors, fuses and supplementary electronic com• modules: curve 1, 3, 4 and 6 from the rear, and curve ponents e.g. power electronics- and CAN-bus-com- 2, 5 and 7 from the front module. ponents. 4 CONCLUSION The total volume of the SC-modules was 161 litres. Despite the great number of series connections, it was 3.2 Performance data possible to keep the series resistance Rs of the mod• ule low, which contributes to the high power capability The series resistance Rs of the front module was 57 and to a good efficiency, both essential for the use in a mQ, and for the rear module an Rs of 56 mQ was drive train system. The chosen cooling system seems measured. This leads to a total Rs of 113 mQ. to be sufficient to keep the module temperature at a tolerable level during cycling and helps to cool the The module was capable of providing a constant capacitors to a lower temperature during breaks, power of 50 kW during 15 seconds of discharge from which leads to a lower self discharge and a longer full (360 V) to half rated voltage (180 V), as shown in lifetime of the capacitors. Figure 2. This is equivalent to an energy content of 210 Wh @ 50 kW. The decline in power during the 5 ACKNOWLEDGMENTS last 3 seconds results from a current limitation at 170 amperes set by the power electronics. We thank Mr. D. Schlunke and Mr. M. Terra from montena components sa, for their technical support during the module assembly and Mr. F. Hurschler from the ETH Zürich for operating the dynamic test bed during the measurements. 6 REFERENCES [1] E. Faggioli, P. Rena, V. Danel, X. Andrieu, R. Mallant, H. Kahlen, Supercapacitors for the en• ergy management of electric vehicles, J. of power sources, 84, 261, (1999). [2] P. Dietrich, F. N. Büchi, M. Ruge, A. Tsukada, G. G. Scherer, R. Kötz, S. Müller, M. Bärtschi, P. Rodatz, O. Garcia, Proceedings of the 2nd Boost- cap meeting, supercapacitors for peak-power ap• 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1—T1"*! 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 plication with fuel cell system, Fribourg, Switzer• Time / s land, March 29 (2001). Fig. 2: Measured current, voltage and calculated [3] R. Kötz, S. Müller, M. Bärtschi, B. Schnyder, P. terminal power during a constant 50 kW discharge of Dietrich, F.N. Büchi, A. Tsukada, G. G. Scherer, the supercapacitor module. P. Rodatz, O. Garcia, P. Barrade, V. Hermann, R. Gallay, Supercapacitor for peak-power demand in The thermal behaviour of the supercapacitor module full-cell-driven cars, ECS Proc, PV 2001-21. The showed a maximum temperature increase of 15 °C Electrochem. Soc, Inc., Pennington, NJ. (Figure 3, curve 1) after 2700 s of cycling with 30 kW. [4] B. Schnyder, Kontaktwiderstand-Optimierung, During the following 1800 s break the temperature of Technische Mitteilung PSI, TM-50-01-02 (2001). curve 1 dropped about 10 °C. 76 BIPOLAR GLASSY CARBON HIGH POWER SUPERCAPACITOR M. Hahn, B. Schnyder, M. Bartsch, R. Kötz, M. Carlen (ABB), D. Evard (Leclanché S.A.) As the final step of the recently finished 'AStorCap' project a multi-cell supercapacitor was built and suc• cessfully tested. In this contribution this ß-devlce is compared with a previously built a-demonstrator. The performance limits of the technology are estimated from these data. 1 INTRODUCTION A single cell inside the stack consists of two adjacent porous layers (i.e. single-sided electrodes) and the Charge storage in a so-called supercapacitor takes electrolyte between them. Fig. 1 shows a CAD- place in the electrochemical double layer, i.e. at the drawing of the bipolar stack design. boundary between an electronic and an ionic conduc• tor inside the highly porous electrodes. Today's com• 3 ELECTRICAL PERFORMANCE mercial devices use a combination of activated carbon (as powders or fibres bound to a metallic current col• Due to an improved activation procedure, the active lector) and either an organic (low conductivity) or layer thickness of the ß-demonstrator - compared to aqueous (high conductivity) electrolyte [1, 2]. The spe• the a-demonstrator described in [3] - is doubled, re• cial approach of the recently finished 'AStorCap' pro• sulting in a proportional increase of capacitance, C. ject is to employ activated glassy carbon (gc) as the Additionally the nominal cell voltage, U, could be electrodes in a bipolar multi-cell device [3, 4]. Acti• raised from 24 V to 30 V. Thus the maximum energy, vated glassy carbon is unique with respect to its E = V2CU2, increased by a factor of 3.6 (Table 1). 'monolithic' structure: The thermally grown nanopor- ous (active) layer, some 10 urn thick, adheres tightly to the non-activated backbone, about 200 um thick, a-Demonstrator ß-Demonstrator thereby providing a very low resistivity compared to conventional powder-type electrodes. C[F] 0.43 1.00 RESR [mQ] 24.8 24.6 2 CAPACITOR DESIGN u\y] 24 30 The bipolar stack of both devices consists of 31 elec• trodes, 120 mm in diameter. A glass fibre cloth soaked E[J/dm3] 344 1250 with sulfuric acid and an elastomer gasket separate each two adjacent electrodes. Terminals are glued P [kW/dm3] 16.1 25.5 with conductive resin to the outermost electrodes. Table 1 : Electrical data of the two demonstrators. Since both devices have almost the same equivalent series resistance (ESR), the maximum power, P = lf/4RESR, of the ß-device is only enlarged due to the higher voltage. The constancy of the ESR can be un• derstood in view of the contributions of the different layers to the ESR, listed in Table 2. •HI a-Demonstrator ß-Demonstrator IIP ¡un d[um] ñ[mQ] d[um] ñ[mQ] a WBW~ acid 190 6.94 120 4.39 gc (bulk) 180 0.06 160 0.05 ÜH fflfflittiiH •l gc (porous) 10 13.80 20 16.26 endplates 200 4.00 800 3.90 Table 2: Thickness of the different (single) layers and their total contribution to the ESR of the two demon• Fig. 1 : CAD-drawing of the bipolar stack design (sec• strators. tional view). 77 Obviously, the resistance increase due to the thicker The dependence of maximum energy and power den• porous layer is just compensated by the resistance sity on the thickness of the porous film is calculated in decrease due to the thinner electrolyte layer. The con• Figure 3 for an optimized device, simultaneously tributions of the acidic electrolyte and the bulk-gc are showing the performance limits of the technology. calculated from literature data, while the value for the endplates is measured. The metallic endplates con• 4000 160 tribute to the ESR in terms of contact resistance. The resistance of the porous layer is then simply given as the difference between the total ESR and the sum of 3000 the other contributions. 33 2000 From the above data a volume resistivity of the porous layer of 22.65 Qcm (a) and 13.4 Qcm (ß) is calculated. LU Thus, the resistivity of the porous layer is still signifi• 1000 cantly higher than the resistivity of the bulk acid, 1.2 Qcm, and that of the bulk-gc, 0.01 Qcm, and domi• nates the ESR of the device. One explanation for this increased resistivity is the reduced mobility of the ions dp/um in the narrow pores of the activated carbon. Typical pore diameters are in the order of 2 nm. From litera• Fig. 3: Calculated dependence of maximum energy ture data [5] an increased resistance by a factor of 10 and power density on the thickness of the porous layer or more could be expected. of an optimized device. A thickness of 120 um for the acid gap was assumed. 4 OPTIMIZATION POTENTIAL The Ragone plots of the a- and ß-demonstrator are 5 CONCLUSION shown in Figure 2. The same housing was used for With respect to power density the ß-demonstrator both devices. exceeded the goals of the CTI project. A power den• sity of 25 kW/dm3 was demonstrated which is among the highest values ever reported for a supercapacitor. The performance limits of an optimized device (same P/E-ratio) are estimated to be higher by a factor of 2 (50 kW/dm3 and 2400 J/dm3). An increase in energy density above 2400 J/dm3 can only be achieved by a trade-off in power density. 6 ACKNOWLEDGEMENT Financial support by CTI (project no. 4096.1) is grate• fully acknowledged. 7 REFERENCES [1] B.E. Conway, Electrochemical Supercapacitors: E [J/dm3] Scientific Fundamentals and Technological Appli• cations, Kluwer, New York (1999). Fig. 2: Ragone plots of the a- and ß-demonstrator. [2] R. Kötz, M. Carlen, Principles and applications of In order to maximize energy and power density of the electrochemical capacitors, Electrochimica Acta, device, the portion of 'passive' components has to be 45, 2483 (2000). minimized: The thickness of the acid gap (and so the gasket), of the bulk-gc and of the endplate, as well as [3] M. Hahn, M. Bartsch, B. Schnyder, R. Kötz, M. the volume (and weight) of the housing-construction Carlen, C. Ohler, E. Krause, PSI Scientific Report have to be reduced as far as possible. According to 1999, V, 79 (2000). our experience with the two demonstrator units we [4] R. Kötz, M. Bartsch, M. Hahn, B. Schnyder, Bipo• estimated that the total volume might be reduced by a larer elektrochemischer Doppelschicht• factor of 2, which would result in a doubled energy and kondensator mit hoher Leistungsdichte, in: Elekt• power density. rochemische Verfahren für neue Technologien, Further increase of energy density would only be pos• GDCH-Monographie, 21, 158 (2001). sible on the expense of power density or vice versa. [5] B. Kastening, M. Heins, Electrolyte composition An upper limit for the film thickness of about 30 um is and ionic mobility in micropores, Phys. Chem. given by the activation procedure; thicker films tend to Chem. Phys., 3, 372(2001). fall off. 78 COMPARISON OF THE SELF-CHEMISORPTION OF AZURIN ON GOLD AND ON FUNCTIONALISED OXIDE SURFACES B. Schnyder, R. Kötz, D. Alliata (INFM, Viterbo), P. Face! (INFM) The formation of extended uniform protein monolayers by single or multiple-step self-chemisorption was investigated on gold and on functionalised oxide surfaces. Chemisorption on oxygen-terminated surfaces (Si02, mica) was preceded by exposure of the surface to 3-aminopropyl-triethoxysilane (3-APTS) and glu- taric dialdehyde (GD). The thickness could be verified after each chemisorption step by ellipsometry. On both substrates (gold and insulator) the protein layers appeared flat and robust under SFM imaging condi• tions. The multiple self-chemisorption approach reported herein could be applicable to similar proteins, since it relies on general principles of protein assembling. INTRODUCTION RESULTS The deposition, preparation, and characterization of In Figure 1 the two expected molecular architectures organic self-assembled monolayers (SAM) on metal, are sketched. Note the well-ordered azurin molecules semi-conductor or even insulator surfaces has poten• on gold, where specific adsorption involves a disulfide tial applications, for example in molecular electronic bridge [2]. The azurin adsorption on functionalised devices as well as in biosensors, biocatalysis and oxide surfaces does not yield a special orientation of biotechnology in general [1]. Self-chemisorption is a the protein molecules. Adsorption occurs randomly, particularly attractive approach to this goal. It takes since the protein molecules link to the preformed layer advantage of the specific reactivity of molecules and by the surface-exposed amino groups of the protein compounds with other molecules and/or the exposed [3]. chemical surface groups giving rise to complex su- pramolecular architecture. Other methods such as the Langmuir-Blodgett technique or spin coating would Azurin hardly be able to assemble such complex multilayer structures. Au (111) In the present work we have built up high-quality monolayers of a metallo-protein, azurin, on insulating, oxygen-terminated surfaces by a three-step supra- molecular reaction. The chemisorption on an insulat• ing substrate could be interessting for biomolecular electronic purposes. For comparison, the protein was also deposited on a gold surface. Si (100) 2 EXPERIMENTAL Azurin (molecular mass 14600) involved in respiratory Fig. 1: Scheme of immobilized protein molecules on phosphorylation of the bacterium Pseudomonas gold (top) and on silicon oxide (bottom). aeruginosa was purchased from Sigma and used with• out further purification. For the immobilized azurin on gold and on GD/3- APTS/Si02, the presence of copper and sulfur was Freshly prepared Au(111) substrates were immersed confirmed by X-ray photoelectron spectroscopy (XPS) 4 in 10" M azurin in 50 mM NH4Ac (Sigma) buffer of pH measurements. These two elements are only present 4.6 for 20-40 min, then rinsed in abundant NH4Ac in the azurin. Finding copper is important, since it im• buffer. plies that the redox site of the protein has not been In order to adsorb the azurin on an oxygen-terminated affected by the immobilization procedure to the extent surface such as the native oxide layer of silicon (p- of losing the redox-active ion. type, <100> orientation) or mica, some additional Ellipsometry performed after the deposition of several preparation steps are required. The samples were successive layers provided an average estimate of prepared in three steps: (i) incubating the substrates in layer thickness. This method is very sensitive (see 3-APTS (6.6% (VA/) in CHCI3) for 2 minutes and rins• Figure 2) and can be used to follow the different ing in abundant CHCI3 in order to remove 3-APTS phases of the immobilization procedure. For azurin on molecules not linked to the surface; (ii) exposing the 4 gold the thickness obtained is only 1.5 nm. Similar silanized sample for 10 min to GD (4 10" M in H20), results have been obtained for azurin on GD/3- then thoroughly washing it in ultrapure H20; (iii) expos• APTS/Si02. These values are low when compared to ing the promoted substrates for 20 min to azurin solu• the average protein size of about 3.5 x 3.5 x 4.4 nm3 tion and rinsing in NhUAc to get rid of the not chemi• known from x-ray crystallography [3]. cally adsorbed molecules. 79 the underlying layer. Therefore, different apparent heights of the bumps reflect different molecular orien• tations. Energy [eV] Fig. 2: Ellipse-metric spectra (only cos(A) is shown) of 300 the build-up of consecutive layers of native Si02, 3- APTS, GD, and azurin compared with bare silicon. Fig. 4: Topographic SFM images of azurin on GD/3- We performed Scanning Force Microscopy (SFM) APTS/mica. Contact mode under NH4Ac buffer with a measurements at low resolution under ambient condi• scanning frequency of 3 Hz; 300 x 300 nm2, Az = 3.0 tions. In Figure 3 the effects of a high-load scan over a nm. rectangular area of the sample with azurin on a func- tionalised oxide surface (GD/3-APTS/mica) are SFM measurements of azurin on Au (111) at low pro• shown. tein coverages show a similar width, but a constant height for all bumps of only about 1 nm, which could be an artifact produced by tip pressure. In investigations performed so far, but not presented here [4], evidence for retention of the functional activity of these molecules could be obtained. This is actually a very important point in view of possible biomolecular applications. 4 CONCLUSION 1.5 fjm Redox protein monolayers self-chemisorbed on func- Fig. 3: SFM image of azurin on GD/3-APTS/mica (a) tionalised oxide surfaces have been successfully built and profile (b) of a 1.5 x 1.5 pm2 area on which a 750 up by three-step supramolecular surface chemistry, x 350 nm2 rectangle had been engraved by the tip and compared with a protein monolayer on gold. The action at high load. immobilization method used in the present work should be a valuable approach to protein monolayer The adsorbed layers have been removed from the formation in general, because its principles apply to scanned area and piled up on the sides (Fig. 3a). The any kind of proteins such as other metalloproteins, profile (indicated in Figure 3a as a dashed white line) enzymes, antibodies etc. across the hole (Fig. 3b) indicates a film thickness of 4.5 nm, which is consistent with the theoretical thick• 5 ACKNOWLEDGEMENT ness of a structure involving one monolayer of azurin on top of the two precursor layers. The thickness dif• This work has been supported by the Istituto Nazion- ference with respect to the ellipsometric data (1.5 nm) ale per la Fisica della Materia (INFM) through the Ad• is understandable in view of the fact that in this tech• vanced Research Project SIN PROT. nique, a completely flat layer is assumed when deter• mining the monolayer thickness, rather than the 6 REFERENCES somewhat bumpy structure visible in Figure 4. [1] H.A.O. Hill, N.I. Hunt, Meth. in Enzymol., 227, 501 SFM imaging was also performed in the contact mode (1993). for azurin on GD/3-APTS/Si02 in physiological buffer solution. A compact film of bumpy structures is clearly [2] Q. Chi, J. Zhang, J.U. Nielsen, E.P. Friis, I. visible on the surface. These features have a lateral Chorkendorff, G.W. Canters, J.E.T. Andersen, J. size of about 10-15 nm and can readily be attributed to Ulstrup, J. Am. Chem. Soc, 122, 4047 (2000). a typical tip-sample convolution around azurin mole• [3] H. Nar, A. Messerschmidt, R. Huber, M. van de cules. Interestingly, the image corrugation is about 3.2 Kamp, G.W. Canters, J. Mol. Biol., 221, 765 nm and the brighter spots do not protrude above the (1991). average height by more than 1 nm. This last point confirms the random adsorption mechanism where the [4] P. Facci, D. Alliata, C. Cannistraro, Ultramicro- protein is linked via surface-exposed amino groups to scopy, 89, 291 (2001). 80 OXYGEN REDUCTION ACTIVITY OF Pt AND PtCo-ALLOY CATALYSTS: A COMPARISON BETWEEN KINETIC MEASUREMENTS AND POLYMER ELECTROLYTE FUEL CELL EXPERIMENTS U.A. Paulus, C. Draschil, T.J. Schmidt (LBNL and PSI), V. Stamenkovic (LBNL), N.M. Markovic (LBNL), P.N. Ross (LBNL), G.G. Scherer The oxygen reduction reaction (orr) has been studied on various carbon supported PtCo alloys in compari• son to carbon supported platinum in perchloric acid. The applied thin film rotating ring-disk electrode (rrde) technique allows both the investigation of the orr and their kinetic analysis and in parallel the detection and quantification of the amount of peroxide produced during the orr. Polymer Electrolyte Fuel cell (PEFC) experiments using commercially available gas diffusion electrodes (gdes) with Pt/C and PtCo/C respec• tively as active layers were carried out to investigate the above characterized catalysts under real PEFC conditions. 1 INTRODUCTION Tafel plots for the orr activity at 60°C are presented in Figure 2. Both Pt3Co and PtCo reveal a better activity Pt alloys are of great interest as orr catalysts in PEFC (by a factor 2-3) compared to Pt/C. Peroxide detection research. At the cathode side of a low temperature (data not shown) shows similar behavior for all three PEFC substitution of pure Pt with Pt alloys would lower catalysts with none of them producing a detectable the precious metal loading. To get inside in the kinetic amount of H202 at potentials higher than 0.7 V (poten• behavior and the performance under PEFC conditions tial range of main interest for PEFC cathodes). Activa• we investigated both, carbon supported catalyst pow• tion energies determined between 25°C and 60°C ders in HCIO4 using the rrde technique and gdes with gave equal values between 20 and 25 kJ/mol for the an active layer of PtCo or Pt supported on carbon in three catalysts. contact to a Nation membrane as well as in fuel cell tests. 0.8 2 EXPERIMENTAL The thin film rrde experiments were carried out in a thermostated three compartment electrochemical cell between 25°C and 60°C in 0.1 M HCI04 as electrolyte. Pt/C, Pt3Co/C and PtCo/C (all 20wt%) were received from E-TEK (DeNora, USA). Details concerning the experimental setup and the electrode preparation are described in reference [1]. Electrodes are prepared 0.0 0.2 0.4 0.6 0.8 1.0 2 with a resulting overall metal loading of 14 M.gmeta/cm . E [vRHE] Fig. 1 : Cyclic voltammograms of Vulcan supported 2 We tested commercially available gdes (0.6 mgPt/cm Pt, Pt3Co and PtCo in Ar saturated HCIO4 at 25°C. 2 and 0.6 mgPtCo/cm ) which were impregnated with Nation (0.6 mg/cm2). Cyclic voltammetry measure• ments were performed at room temperature with Nation 117 as electrolyte (procedure described in ref. [2]). PEFC tests were carried out with Nation 115 as electrolyte in a 30 cm2 test cell with graphite flow field plates with a meander flow field [3]. 3 RESULTS Thin film rrde-measurements 0.81—J— — — —^-i Figure 1 presents the base voltammograms obtained 1(H 101 10° 101 with the thin film electrodes at 25°C in 0.1 M HCIO4. 2 ik [mA/cm ] We find a decreasing hydrogen underpotential deposi• Fig. 2: Tafel plots of Vulcan supported Pt, Pt3Co and tion (Hupd) region A with increasing alloying component PtCo in 02 saturated HCIO4 at 60°C. (Apt/Apocc/Aptco = 1.0/0.71/0.37). This effect is attrib• uted to the reduced number of Pt surface atoms. Con• Measurements on gas diffusion electrodes sidering the stability, the base voltammograms show only slight changes over time and with increasing tem• Cyclic voltammograms for the Pt/C- and the PtCo/C- perature. gde (Figure 3) look only slightly different and the dif- 81 ferences could probably be related to properties of the nique. In addition we know that the particle size of the gde. Again the Hupd region decreases with decreasing alloyed catalyst is equal or even slightly larger (around Pt content (Ap,/AptCo = 1/0.20). 4 nm diameter) and therefore a similar number of 1 surface atoms is present on the catalysts. The similar 1 1 1 1 1 1 1 1 - activation energies point to an identical rate determin• ing step for the orr, and very similar product distribu• tion (reduction of 02 to H20 or H202) indicates that the - orr proceeds via the same reaction pathway. Both aspects serve as an indication for the same reaction _ _ mechanism. Literature suggests several possibilities to - explain the orr activity enhancement of Pt-alloys which Pt/Vulcan-Gde are in detail discussed in reference [1]. The enhanced PtCo/Vulcan-Gde (i*2) activity can be best explained by different OHad sur• 1 i.i.i, face coverages, which influence the pre-exponential 0.0 0.2 0.4 0.6 0.8 1.0 term in the kinetic rate equation. In addition differ• U [V/NHE] ences in the activation entropy (configurational en• Fig. 3: Cyclic voltammograms of the Pt-gde and the tropy) of the different metals can effect the formation PtCo-gde, Nation 117 as electrolyte, Ar saturated, of oxygenated species and the oxygen reduction on humidified environment, at room temperature. the platinum surface atoms (for details compare ref. [1])- In PEFC studies we find a slightly reduced orr activity for the PtCo-gde when compared to the Pt-gde. Consistent with this finding the ratio of the Hupd-region for the thin film catalysts amounts to Ap,/AptCo = 1/0.37 whereas for the gdes only a ration of 1/0.20 is found. These differences in Hupd-areas could point to a differ• ent surface composition of the catalyst particles in the gde modified during the electrode manufacturing process. An other possibility is a reduced catalyst utili• 0.2 1 ' 1 ' 1 ' 1 ' 1 ' ' ' ' ' 1 zation in case of the PtCo-gde due to different wetting 0 200 400 600 800 1000 1200 1400 conditions. 5 CONCLUSION Applying the thin film rrde technique we demonstrated that the orr activity of the alloyed catalysts is a factor of 2-3 higher compared to the Pt-catalyst. Similar activa• tion energies and peroxide yields give rise for the as• sumption of identical reaction mechanisms. The slightly inferior behavior of the commercially avail• able PtCo/C gde compared to the Pt/C gde is not yet completely understood. Different wetting properties of 0.2 ' ' ' 1 1 ' 1 1 1 1 !—1 the catalysts or modified surface compositions could 0 400 800 1200 1600 2000 serve as an explanation. i [mA/mgpJ Fig. 4: Current-Voltage plots obtained from PEFC 6 ACKNOWLEDGMEMENT tests; Pt and PtCo gdes as cathodes (60°C, ca. 80 h runtime, H2/02-operation) normalized to the geometric The rrde measurements were performed during UAPs area and to the overall Pt-loading of the gde. research stay at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley (USA) which was fi• Considering the activity of the gdes (Figure 4A) we nancially supported by the LBNL and the PSI. find that unlike for the thin film electrodes the activity for PtCo/C is slightly inferior to the activity of Pt/C de• 7 REFERENCES spite an again identical overall metal loading (accord• ing to the manufacturer). When, however, comparing [1] U.A. Paulus, A. Wokaun, G.G. Scherer, T.J. the activity based on the Pt-loading (Figure 4B) the Schmidt, V. Stamenkovic, V. Radmilovic, N.M. PtCo/C gde shows the better activity. Markovic, P.N. Ross, submitted to J. Phys. Chem. B (2001). 4 DISCUSSION [2] Z. Veziridis, Diss. ETH-Zürich Nr. 13397 (1999). For the alloyed catalysts we find enhanced orr activity compared to pure Pt applying the thin film rrde tech• [3] L. Gubler, Diss. ETH-Zürich Nr. 13954 (2001). 82 ASSESSMENT OF REFORMATE TOLERANCE IN A TWO-CELL POLYMER ELECTROLYTE FUEL CELL WITH 100 cm2 ACTIVE AREA L. Gubler, G.G. Scherer, A. Wokaun Different technology types of membrane electrode assemblies (MEAs) for the polymer electrolyte fuel cell (PEFC) can be conveniently assessed and compared in a multi-cell fuel cell stack. In this study, a PSI designed two-cell stack with 100 cm2 active area was used to investigate the reformate tolerance using a Pt catalyst in the anode of one cell, and a Pt-Ru catalyst in the other. Good tolerance to reformate contain• ing 100 ppm CO and stable operation was obtained in both cells with an airbleed of 5 %. 1 INTRODUCTION For reasons of fuel availability and fuel flexibility in the short term, and advantages of fuel storage compared to pure hydrogen, the operation of polymer electrolyte fuel cells (PEFCs) with reformed fuel is regarded as a key feature for wide-scale market introduction, and is therefore an important field of research and develop• ment. ^Iv ^^y N2, 20 % C02, and traces of CO (10-100 ppm). CO is with different anode technology types. particularly detrimental to the fuel cell performance, even at these low levels, as it is a strong poison for the Pt-based electrocatalyst in the anode. The develop• ment of CO tolerant H2 electrooxidation catalysts has been a research activity for over 30 years. Among a few others, Pt-Ru and Pt-Mo based catalysts have found to be promising. For fuel cell applications, these metals are supported on high surface area carbon black particles (e.g. Vulcan XC-72R) to maximize dis• persion. Different anode formulations for improved reformate tolerance, varying in catalyst type, microstructure, catalyst layer thickness, etc., can be efficiently as• sessed in a multi-cell stack containing the various technology types in their individual cells. In this study, a two-cell stack was employed with the two cells hav• ing different anode catalyst types. Fig. 2: Flow field design of the PSI 100 cm2 fuel cell. 2 EXPERIMENTAL One channel is highlighted to visualize the flow path. A two-cell stack was assembled with different anode 3 RESULTS AND DISCUSSION types (Figure 1). We employed fuel cell hardware de• veloped at PSI with an active area of 100 cm2 [1]. The In the first series of experiments, only the CO toler• flow field plates comprise 7 parallel fluid channels, ance of the two anode types was assessed using milled into graphite plates (Figure 2). The anode and H2/CO model gases with a CO concentration of up to cathode flow fields are identical. The anode of cell 1 100 ppm, because CO causes the main performance contained a carbon supported pure Pt catalyst (Pt/C), losses when using reformate as fuel. Polarization whereas cell 2 had a Pt-Ru/C anode. The cathode curves are shown in Figure 3 for the Pt/C containing catalyst of both cells was Pt/C. The noble metal load• anode, and in Figure 4 for Pt-Ru/C. It is obvious that ing on all the electrodes was 0.6 mg/cm2. The polymer Pt-Ru/C has a higher CO tolerance than Pt/C. It the electrolyte membrane used was Nation 112 from Du- literature, this is explained with the fact that the CO Pont. Operating temperature of the stack was regu• coverage is smaller on Pt-Ru than Pt, resulting in more catalyst sites availabe for the electrocatalytic lated to 60 °C, reactant (H2/air) pressure was 1 bara. hydrogen oxidation reaction. The polarization curves Fuel flow was 1.5 times stoichiometric for pure H2 as well as "synthetic" reformate. Air stoichiometry was using H2/100 ppm CO are not shown, because severe 2.0. The fuel gas was humidified to a dew point of voltage instabilities occurred, which are already visible 80 °C, whereas the air was fed dry to the cathode. in Figure 4 to some extent. 83 1.0 .H2 Stack Average .H2 / 10 ppm CO .H2 / 25 ppm CO .H2 / 50 ppm CO -0-H2 0.2 -- ___H2 / 100 ppm CO ..„!„.. H2 / 100 ppm CO / 40 % N2 H2 / 100 ppm CO / 40 % C02] " 0.0 -f- -+- -f- 0 100 200 300 400 500 600 100 200 300 400 500 600 Current Density [mA/cm2] Current Density [mA/cm ] Fig. 3: Polarization of the cell using Pt/C as anode Fig. 5: Reformate tolerance in the two-cell stack. electrocatalyst. T = 60 °C, p = 1 bara. T = 60 °C, p = 1 bara. 40 % N2 the cell performance does not seem to be 1.0 ,H2 affected, whereas 40 % C02 leads to a further de• Pt-Ru/C ,H2 / 10 ppm CO crease in cell voltage. It is known that also C02 forms H2 / 25 ppm CO poisonous adsorbates on the surface of Pt based ,H2 / 50 ppm CO catalysts - although to a much lesser extent than CO - wich leads to the observed additional cell voltage loss [3]. 4 CONCLUSION CO and reformate tolerance was investigated in a two- cell stack, which is a comfortable method for parallel assessment of technology types. One cell had Pt/C as 0.0 100 200 300 400 500 600 anode electrocatalyst, the other Pt-Ru/C. In the ab• sence of airbleed, the cell with Pt-Ru/C anode exhib• Current Density [mA/cm] ited the better CO tolerance. With a 5 % airbleed, the performances of the two cells were identical within Fig. 4: Polarization of the cell using Pt/C as anode 20 mV over the whole current density range investi• electrocatalyst. T = 60 °C, p = 1 bara. gated. The addition of 40 % N2 did not have an impact on performance. With 40 % C02, however, a small additional performance loss is observed. Also with the advanced Pt-Ru/C catalyst, however, the voltage losses are still considerable, even at a CO A stack with more than two cells can be used to com• content of only 10 ppm. An effective method to pare more technology types, or to introduce statistical achieve good CO tolerance up to 100 ppm CO is the analysis of cell variation, provided the individual cells injection of a few percent of air into the fuel gas experience the same operating conditions in the stack. stream [2]. The technique is known as 'airbleeding'. The oxygen in the air reacts with the adsorbed CO to 5 REFERENCES C02, freeing thereby catalysts sites for H2 turnover. [1] A. Tsukada, G.G. Scherer, I. Popelis, Proceed• Because the voltage difference between the two cells ings of the International Conference on "Portable was less than 20 mV after adding an airbleed of 5 %, Fuel Cells", June 21-24 1999, Luzern, Switzer• the average stack voltage is shown in Figure 5. With land, Ed. F.N. Büchi, p. 139. H2/100 ppm CO as fuel, there is still a difference in [2] S. Gottesfeld, J. Pafford, J. Electrochem. Soc, performance to the pure H2 baseline. It is speculated that the 5 % airbleed clears away the CO from the 135, 10, pp. 2651-2652 (1988). surface of the catalyst at only a fraction of the active [3] K.R. Weisbrod, N.E. Vanderborgh, Proc. 29th area, while some areas are still poisoned. Further Intersociety Energy Conversion Engineering Con• polarization curves were recorded with N2 and C02 ference (IECEC 94), Monterey CA, Aug 7-11, pp. admixed to the fuel to simulate "true" reformate. With 855-860 (1994). 84 INVESTIGATION OF TEMPERATURE DEPENDENCE ON CO-POISONING IN A POLYMER ELECTROLYTE FUEL CELL OPERATING WITH REFORMATE F. Hajbolouri, B. Andreaus, L. Gubler, G.G. Scherer, A. Wokaun The temperature dependence of CO-poisoning has been investigated in a 29 cm2 fuel cell equipped with graphite plates. The CO-poisoning proved to be extremely temperature sensitive in a temperature range of 90°C to 100°C. The AC-impedance spectroscopy in pseudo-galvanostatic mode was used to investigate the changes of the membrane- and electrode- resistances with increasing cell temperature. A pseudo- inductive impedance contribution at low frequency due to the CO-poisoning was observed which de• creased strongly at 100°C. 1 INTRODUCTION proximately 20 mV could be observed, (see inset in Figure 1). During the cell voltage drop the anode sur• The CO-poisoning of the anode in polymer electrolyte face will successively be covered by CO. When the fuel cells (PEFCs) operating with reformate gas cell voltage has reached a value of around 100 mV, a causes a large performance loss in these cells. Since removal of some CO by adsorbed OH takes place and the CO-poisoning of the electrode catalyst, Pt, is results in a small increase of the cell voltage. Once strongly temperature dependent, improvement of the again, when part of the Pt sites are free for CO- CO-tolerance can be achieved by increasing the fuel adsorption the cell voltage will drop. The fluctuation is cell temperature. However, operation of the PEFC therefore an interplay between CO- and OH- with Nation membrane at temperatures above 100°C adsorption/-desorption and -oxidation at the surface and at ambient pressure is almost impossible due to and probably the CO and OH coverage should reach their insufficient stability and humidification at higher a certain value before the oscillation can be visible temperature [1]. The fundamental understanding of [2,3]. Studies carried out on model catalysts have the CO-poisoning, its temperature dependence, and shown that these oscillations have different shapes on investigation of the different resistance contributions different Pt crystal planes. The reason for this is the from the cell components at various cell temperatures different affinity of the Pt crystal surfaces towards CO- are of essential importance for a performance im• adsorption. The irregularity of the potential oscillation provement of a reformate fuel cell system. Here, we can be explained by the poly-crystallinity of the Pt report some results from the CO-poisoning and AC- particles in the catalyst layer of the electrode. impedance measurements in a 29 cm2 fuel cell. 2 EXPERIMENTAL The cell design used in this study was a graphite cell, 29 cm2, with three parallel gas channels. E-TEK elec• trodes, 0.6 mg/cm2 Pt/C, were impregnated with Nation solution yielding 0.6 mg/cm2 ionomer and used for both anode and cathode. Nation 115 from DuPont (Wilmington DE, USA) served as electrolyte. The fuel, H2 or H2/CO, and the oxidant, 02, were pressurized at o.o r 1 3 bara and humidified at a dew point of 95°C. The cell was operated at 500 mA/cm2 for at least 100 h to 0 1000 2000 3000 4000 5000 6000 reach steady-state conditions before the measure• Time / s ments were started. The AC-impedance measure• Fig. 1 : Cell voltage drop as a function of time after 2 ments were performed using a Zahner IM6 work• changing the fuel gas at 500 mA/cm from pure H2 to station in addition with a current sink EL300 under a H2/100 ppm CO. The cell was operating at 70°C and 2 constant current density of 500 mA/cm within a fre• 3 bara. quency range between 50 mHz and 10 kHz. The amplitude and period of the voltage oscillation varied with cell temperature and the CO concentration 3 RESULTS of the fuel. CO-poisoning is extremely temperature Figure 1 shows an example of the cell voltage de• sensitive and it could be observed that at higher cell crease due to the CO-poisoning as a function of time. temperatures the period of the oscillation became The cell was operating at 70°C, 3 bara and a constant larger while their amplitude decreased. current density of 500 mA/cm2. At t=0 s the fuel was What is the physical meaning of these changes and changed from pure H2 to H2/100 ppm CO. Already how do they influence the cell performance? after a few seconds the cell voltage started to drop down from 625 mV to reach a value of 100 mV after The influence of the temperature on the CO-tolerance almost 1 h. Afterwards, an irregular oscillation or fluc• of the cell was investigated by operating the cell at 2 tuation of the voltage with small amplitudes of ap• 90°C and 100°C and at 100 mA/cm with H2 respec- 85 tive H2/100 ppm CO for at least 24 h before the adsorbed species CO, 0CO; the larger 9co, the bigger measurement. Figure 2 shows the polarization curves the loop's diameter. At 90°C, we find a much larger for the two fuel compositions and temperatures, re• 0CO than at 100°C, and subsequently also a larger spectively. The cell performance enhanced remark• value for the overall charge transfer resistance. For able when the cell temperature was increased from resolution problems the cell impedance for pure H2 is 90°C to 100°C. At temperatures below 90°C the not plotted in the same figure, it would appear as a measured cell voltage was very low. It is already dot. known from CO-oxidation on Pt in gas phase catalysis that a thermal desorption of CO occurs in the tem• 0.15 p H i i "i j " i11 " i , i ,•; * 0.15 perature range 80-100°C when H2 is present in the 0.10 •: vi • I- 0.10 reaction gas [4]. The fast kinetic of the H2 electro- : i S\~ \ \ \ 0.05 - :• ••/••••• : :->v ^0.05 oxidation confirms a significant improvement of the E SOmHzy : \ \ : E cell performance even for a small increase of the ° 000 •'• .„ , "A "¿lOHz1- 0.00 o : 10 kHzV^y I: : ~- number of free Pt active sites. At open cell voltage or S-0.05 ^ 'A i H -C.05 S very small current densities the poisoning effect of CO i ; i \ i i >\ \ Ü -0.10 -: Xx ' / i :" -0.10 is negligible due to the very high exchange current a 5 C15 density of H2, region I in Fig 2. As the current density • ' ; "t^ÍÍHZ: - is increasing the influence of the CO-poisoning be• .0.20 r. i . i i i i i . i i i . i I i . i . i I . . i 11 -0.20 comes more and more pronounced because of the 0.00 0.05 0.10 0.15 0.20 0.25 0.30 increasing charge transfer over-potential due to the Re (Z) / ohm limited availability of the Pt sites for the H2 oxidation, region II. Fig. 3: Nyquist plots of the fuel cell impedance at 90°C (dashed) and 100°C (solid) after CO-poisoning and decrease of the cell voltage to 140 mV respective 90 °C, H2 90 °C, H2/100 ppm CO 220 mV. The cell has been operated galvanostatically 2 100 °C, H2 at 500 mA/cm after changing of the fuel from H2 to 100 °C, H2/100 ppm CO H2/100 ppm CO. 4 CONCLUSION The CO-poisoning is a function of several parameters, temperature, CO-concentration, time, current density, and the other components in the fuel. A significant 0 200 400 600 800 1000120014001600 CO-tolerance could be achieved at a cell temperature Current density / mAcm"2 of 100°C. The most obvious reason is the CO- desorption at this temperature. The total cell imped• ance and also the pseudo-inductive behaviour of the Fig. 2: A comparison of the polarization curves at cell cell decreased by increasing the cell temperature from temperature 90°C and 100°C for H2 and H2/100 ppm 90°C to 100°C, while the membrane resistance re• CO. The cell has been operated at 100 mA/cm2 for 24 mained the same. h before the measurement. The curves in Figure 2 present the effect of CO poi• 5 ACKNOWLEDGEMENT soning when the cell has been poisoned and operated Financial support by Alliance for Global Sustainability at 100 mA/cm2 i.e. in the region where the effect of (AGS) in Switzerland is gratefully acknowledged. CO-poisoning is very small. When the cell was oper• ated at 500 mA/cm2 then a lower cell performance 6 REFERENCES was obtained. Figure 3 shows the Nyquist plots of the cell impedance at 90 °C and 100 °C when the cell [1] L. Gubler, Operating Polymer Electrolyte Fuel voltage has deteriorated to 140 mV respective 220 Cell with Reformed Fuel, Doctoral thesis, PSI mV after the CO-poisoning at 500 mA/cm2. From the (2001). high frequency end, we can extract the magnitude of [2] A.V. Oertzen, H.H. Rotermund, A.S. Mikhilov, G. the membrane resistivity. We find similar values for Ertl, Standing Wave Pattern in the CO Oxidation, both temperatures indicating that there is no problem J. Phys. Chem. B, 104, 3155 (2000). of membrane humidification at 100°C under the men• tioned operation condition. Both spectra show a [3] K. Beduerftig, S. Voelkening, Y. Wang, J. Wint- pseudo-inductive loop at the low frequency end, char• terlin, K. Jacobi, G. Ertl, OH adsorption on Pt(111),J. Chem. Phys., 111, 11147 (1999). acterized by lm(Z) > 0. This is typical for an electrode surface covered by an adsorbed species, the cover• [4] D.H. Parker, D.A. Fischer, J. Colbert, B.E. Koel, age of which changes with the potential. The diameter J.L. Gland, Low temperature CO displacement, of this loop is correlated to the surface coverage of the Surface Science Letters, 236, L372 (1990). 86 ON THE IMPORTANCE OF A SUFFICIENT WATER SUPPLY AT POLYMER ELECTROLYTE FUEL CELL ANODES B. Andreaus, A.J. McEvoy (EPF Lausanne), G.G. Scherer Investigations of polymer electrolyte fuel cells (PEFC) by electrochemical impedance spectroscopy (EIS) have shown that the water supply at the anode catalyst layer plays a crucial role for the performance of the cell, especially at high current densities. Insufficient water content in the active layer of the anode leads, in addition to the rise of the ionic electrolyte resistance, to a increased activation potential for the hydrogen oxidation reaction. This hypothesis is corroborated by experimental findings for H^Oz PEFC's, where we show that the water content in the anode active layer can be significantly increased by only a small positive pressure difference between cathode and anode, resulting in a substantial improvement of the cell per• formance. 1 OUTLINE OF THE PROBLEM At low frequencies, the water content in the electrolyte starts to oscillate with the potential perturbation and For mobile applications, a prerequisite for a success• induces that way the additional low frequency imped• ful commercialization of fuel cells is the compactness ance feature, which in return indicates a water short• of the system. We aim therefore for a system which is age in the electrolyte. able to deliver a high power density. Consequently, the fuel cell must deliver high current densities without For a long time, the potential decay and the appear• significant potential losses. For PEFC's, an increased ance of the low-frequency impedance feature at high performance loss may occur, particularly when thicker current densities was mainly associated with the cath• polymer electrolyte membranes are used for their bet• ode flooding [2]. The only point which portends to the ter mechanical stability or when the oxygen is provided flooding is that with thicker membranes, the net from air. amount of water transported from the cathode to the anode is reduced and more water must be leaving on In the latter case, we can simulate the drying of the the cathode side. Under the studied operational condi• membrane by using thick electrolyte membranes in a tions, there was no indication for this kind of limitation. fuel cell fed with H2 and pure 02. For these experi• 113.5 mental conditions, at high current densities, an addi• tional performance loss occurs resulting in a potential decay in a current-voltage curve. It can be analyzed by means of impedance spectroscopy, EIS. In the spec• tra, this operation regime is characterized by an addi• tional impedance feature at low frequency, an increase in the overall charge transfer resistance of the cell at medium frequencies and the rise of the membrane resistivity at high frequencies. At medium and high frequencies, the time constant for the water transport in the membrane is too large com• pared to the potential perturbation cycletime, and hence the water content in the membrane remains ' '8.5 constant. We have recently shown [1] that the ob• 0 0.1 0.2 0.3 0.4 0.5 O.S Current density [A/cm2] served pheno-mena are mainly evoked by the follow• Fig. 1: Charge transfer resistances Rct,anode/cathode and ing two step mechanism: r a the membrane resistivitiy Rmembrane f° cell with a a) The electrolyte dries out, particularly close to the 254 umdry thick membrane. anode side and in the fine ionomer channels in the active layer of the anode. In the impedance spec• If the water content on the anode side is limiting, the tra, this effect is referred to by an increase of the question arises how to bring more water to this place, high frequency resistance, the electrolyte specific without the energy-costly humidification of the anode resistivity grows. gas, which, in addition, cannot be sufficient [1]. b) This water shortage in the anode catalyst layer Our approach is to ease the transport of product water inhibits the hydration of the protons at many cata• from the cathode towards the anode. To this end, we lytic sites, which become effectively inactive. have applied a slight positive pressure drop from the Therefore, the active area for the hydrogen oxida• cathode to the anode side. Such pressure drops are tion shrinks, the increase in the charge transfer re• currently being used for direct methanol fuel cells to sistance of the anode may be seen in Figure 1. prevent the crossover of methanol through the mem- 87 brane to the cathode side. For PEFC's, the pressure to the anode, show a less accentuated potential im• drop was discussed theoretically by Eikerling et al. [3] provement when a pressure difference is applied. on the basis of a convective water transport model. When the pressure drop is applied, the cell potentials at a certain current density of all cells with different 2 EXPERIMENTAL membranes group in the same range. 2 We used 28.3 cm active area stainless steel cells Additionally, we compared the water flux jH2o,c leaving without a flow field to keep the current distribution as the cathode of a cell operated with dry gases at homogeneous as possible. The cell was operated with 500 mA/cm2 with Ap = 0, to the one established at 2 H2/02 with an excess of 50% in stoichiometric gas 835 mA/cm but with Ap = 46 mbar. We found that the flow, at ambient pressure, and at 75°C. We used elec• low frequency impedance was of comparable value 2 2 trodes from E-Tek with 0.6 mg/cm Pt/C and Nation although jH2o,c (approx. 25 (xg/cm /s) was almost 3.5 membranes. A pressure difference of 45 mbar was times higher for the cell with the pressure difference. created by increasing the cathode gas outlet pressure Nevertheless, the impedance spectra showed a simi• by a water column. The EIS spectra were recorded lar low frequency behaviour, where the mass transport with a Zahner IM6 at constant current, applying a po• hindrance induces an additional resistance in the tential perturbation of 5 mV. range of 0.3-0.5 Qcm2. Hence, an increased water flux through the cathode together with a higher need for 3 RESULTS & DISCUSSION oxygen due to the higher current density does not translate to an augmentation in the mass transport When the small pressure difference between anode limitation and an increasing Rct as observed in Fig• and cathode is applied, the cell performance at high ure 1. Therefore, the cathode flooding cannot be the current densities is significantly improved as one can reason for the additional performance loss at higher see from Figure 2. The enhancement is more pro• current densities for the studied cell type. nounced for cells with thicker membranes, as in this case, the water shortage on the anode side at equal 4 CONCLUSION gas pressures is accentuated. When we apply a minor positive pressure difference between the cathode and the anode of a H2/02 fuel cell, we can observe a substantial increase in the cell performance, particularly when thicker electrolytes or those with a low intrinsic water content are used. From these findings, we can draw the following conclusions: 1. The performance loss at high current densities is due to the drying out of the electrolyte on the anode side, with the result that the membrane resistivity as well as the charge transfer resistance for the hydrogen oxidation increase. 2. The application of a pressure difference constitutes Current density [mA/cm2] a very efficient way to improve the cell performance at almost no costs, provided that there is no water Fig. 2: Comparison of the current-voltage curves shortage on the cathode side. For real systems op• showing the improvement of the cell performance erated with air however, this requirement can al• when a pressure drop is applied. ready be critical. From the figure above, one can see that the mem• 3. On the other hand, when one studies fundamental brane resistivity is a main factor for the performance aspects of pressurized fuel cells, the pressure must impairment at high loads. This resistivity is significantly be under a very accurate control, as already very reduced if the pressure difference is applied. But it is small pressure differences may fundamentally not the only factor for the improvement. The analysis change the water balance in the cell. of EIS spectra at a current density of 500 mA/cm2 revealed that also the integral charge transfer resis• 5 REFERENCES tance of the full cell decreases by more than 30 % [1] B. Andreaus, A.J. McEvoy, and G.G. Scherer, from 10.0 mQ to 6.8 mQ. The double layer capacity, Electrochim. Acta, in press. however, did not show a significant change. [2] T.J.P. Freiré, E.R, Gonzalez, J. Electroanal. With the pressure difference, the cell potential rises at Chem. 503, 57 (2001). 500 mA/cm2 by roughly 100 mV to 573 mV. Cells with thinner membranes or membranes with lower equiva• [3] M. Eikerling et al., J. Electrochem. Soc. 145(8), lent weight, which both improve the net water transport 2684 (1998). 88 EFFICIENCY IMPROVEMENTS BY PULSED HYDROGEN SUPPLY IN POLYMER ELECTROLYTE FUEL CELL (PEFC) SYSTEMS A. Tsukada, P. Rodatz (ETH Zürich) The PEFC has to be wet for the cell to work efficiently. However too much water (liquid) impedes the deliv• ery of reactants and impairs the electrochemical reaction. A well-known method to correct this is to in• crease the stoichiometric ratio of reactant gas well above one. In the air circuit, the ratio is always about 2. However, in the hydrogen circuit it must remain as close as possible to unity to avoid a decrease of the total efficiency. The conventional method to alleviate this drawback is to install a re-circulating fan to achieve the same result. In this report, a simpler arrangement is presented which uses pressure waves to remove water droplets and inert gas blankets from the fuel cell. 1 INTRODUCTION For the air supply, an Opcon twin-screw charger OA 1040 was used. The air was humidified using a PEFC's only work efficiently if the membrane electrode Lechler™ piezoelectric atomizer. The cathode was assembly (MEA) is wet. If the membrane dries out, the supplied with 100% excess air. electrochemical reaction stops in that area. However, if the MEA is too wet, the delivery of the reactants is The hydrogen is supplied from a high pressure cylin• impeded. Therefore good humidification is necessary der at pressures up to 200 bar. and excess product water and/or excess humidi• fication water has to be removed from the fuel cell. 3 RESULTS AND DISCUSSION Although many studies have been made to optimize fuel cell system performance, there is still little agree• The most simple arrangement to supply the fuel cell ment for mobile solutions [1], [3]. with hydrogen is a dead-end system (arrangement A in Figure 2). In this arrangement, only the amount of This study focuses on the hydrogen supply. Several hydrogen which is needed to sustain the reaction is system configurations were investigated and com• fed to the entrance of the fuel cell. The exit is sealed pared. A feasible solution that produced good results off by a valve which is only opened sporadically to was found. The voltage levels are similar to static test remove inert gases which may have accumulated bench experiments where the fuel cell is operated inside the fuel cell. under optimal conditions (favorable humidification, Since only the amount of hydrogen which is consumed favorable temperature level, excess reactants flow at by the fuel cell enters the stack, the dynamics that can the anode and cathode sides). be achieved are very limited. This disadvantage can be overcome if excess hydrogen is available. In this 2 EXPERIMENTAL case, a flow larger than required is passed through the fuel cell by opening the exit valve. If the excess hydro• gen is released to the surroundings, the overall system efficiency will drop to a very low level. The hydrogen released to the environment not only leads to a dete• rioration of the efficiency, but is also a potential safety hazard, since it may react in an uncontrolled way with oxygen in the air. A possible solution is the recircula• tion of the excess hydrogen to the stack entrance by means of a fan which compensates the pressure drop across the fuel cell (arrangement B). Although the fan is a parasitic power consumer, the system efficiency increases substantially when compared with the ar• rangement where excess hydrogen is not circulated. The hydrogen can also be recirculated using an ejec• tor (arrangement C). In this device, hydrogen is fed at high pressure and relatively low velocity into a nozzle Fig. 1 : View of test bench. where it changes to a low pressure and high velocity stream. The relative low pressure attracts hydrogen to The test bench comprises a PEFC stack which was be pumped from the exit of the fuel cell stack. Momen• developed at the Paul Scherrer Institut. It consists of tum is exchanged between the fluids, raising the pres• 100 cells, each with an active area of 204 cm2. The sure of the hydrogen being pumped. The mixture is nominal power output is 6.5 kW. The stack is supplied then discharged and released to the entrance of the fuel cell stack. The ejector is a static device, and with pure hydrogen and air. It is operated at 2 bara and at temperatures below 70°C. The fuel cell is described therefore works well only at one point of the flow spec• in more detail in [2]. trum. 89 In arrangement A, the fuel cell voltage dropped slowly, Further the diffusion layer which is situated between but continously, during two purging events when the the flow channel and the MEA is dynamically inflected exit valve remained closed, whereas the voltage re• by the pressure wave. These recurring expansions generated with each purging cycle. When the fre• and contractions assist the removal of unwanted liquid quency of the purging events was increased, the mean from the MEA and the supply of hydrogen to it. Also, voltage also increased. At high frequencies, the volt• blankets of inert gases (such as accumulated nitro• age could almost be stabilized at levels similar to ar• gen) that may have formed in the flow field and/or the rangement B, where the fuel cell was operated with diffusion layer, and thus impeded the supply of hydro• excess hydrogen. gen to the MEA, are carried away. Arrangement D shows a system that is able to gener• A SanaoM Magnetic ate these pressure waves without losing any hydrogen Vate "a" valve M to the environment. Using a small pump, a low pres• n sure (relative to the operating pressure of the fuel cell) ±5L PEFC —i .,.•) is created inside a vessel. A magnetic valve is in• B stalled between the fuel cell stack and the low pres• Vahns * a* Sensor 1 sure vessel. The pressure drop across this valve is H9 ; similar to the pressure drop across the purging valve. PEFC Therefore, using the pump, near-atmospheric condi• tions are created inside the vessel and the same effect Fan as purging to the environment is achieved. The para• sitic power loss by the pump is 5 to 10 times lower ••ifcT than the fan used in arrangement B. C Valva* a* Sensor 1 In arrangement D, the pressure waves resulted in a difference in pressure between the fuel cell and the I 1« PEFC vessel, whereas the operating pressure of the fuel cell is higher than that inside the vessel. Another possibility is to have a vessel where the pressure is higher than the operating pressure of the fuel cell (arrangement E). As the relative pressure difference is the same, the effect of the pressure wave is also approximately the Senear 1 Valve " a" same. When using high pressure hydrogen storage, Hn this pressure elevation is, of course, easily achieved. • "~i— PEFC With the pressure wave originating from the low pres• sure vessel, water-droplets are extracted, whereas in Pump M1 the arrangement with the high-pressure vessel the droplets are pushed out. A logical next step is the combination of both systems to maximize the effect. Sensor2 The arrangement of the hydrogen supply installed on (p\ M2 the test bench is the following: Vesse! The hydrogen is stored in a high-pressure cylinder, with a volume of 50 liters. The cylinder is separated —*rxi— PEFC from the rest of the system by a pressure reduction Vafe» " »" valve, which reduces the pressure from a maximum value of 200 bara to 8 bara. The control valve "a" is Fig. 2: Schematics of different hydrogen supply sys- installed in the main hydrogen stream ahead of the terns. ejector. This valve controls the pressure at the en• trance to the fuel cell stack, using the signal from The positive effect of the purging cannot be explained pressure sensor 1. In the ejector, the main stream is solely by the removal of inert gases from the system. mixed with the excess hydrogen flow which was not Because of the pressure difference between both consumed in the fuel cell reaction. sides of the valve, and because of the fast opening of the valve, a shock wave is generated. This wave Between the pressure reduction valve and the control moves through the service channel and the fuel cell valve "a", part of the hydrogen flow is led off and fed to flow field at high speed. Thereby, any water droplets the high-pressure vessel. The pressure inside this that may have formed inside the fuel cell are dis• vessel is controlled by means of control valve "b", persed. The wave is followed by a temporary increase using the signal from pressure sensor 2. With the help in flow velocity. Consequently, the liquid water parti• of the magnetic valve M1, pressure waves are gener• cles are blown out from the fuel cell, allowing for the ated which are routed to the entrance of the fuel cell. delivery of additional hydrogen and thus preventing the This secondary hydrogen flow is combined with the reactant starvation of part of the fuel cell. main stream between the ejector and the fuel cell. The 90 hydrogen that leaves the fuel cell at the exit of the is very poor. The polarization curve has a steeper stack is branched into three paths. The main flow is gradient and the voltage falls 30% short of the result recirculated to the ejector, where the pressure is from the static test. Measurements with arrangement raised again to the level at the fuel cell entrance. In the B are represented by diamonds. The results have second branch, hydrogen is released periodically to increased substantially from arrangement A but are the low pressure vessel. A diaphragm pump is used to still below those of the static test bench. In contrast, create a low-pressure inside this vessel. The pump very good performance was achieved with arrange• discharges to the hydrogen feed between the ejector ments D & E (denoted by the circles). At some point, and the stack entrance. Similar to the high-pressure even the results from the static test bench could be vessel branch, the magnetic valve M2 is used to gen• impoved upon. erate pressure waves. In this case the pressure waves are routed to the exit of the fuel cell, as the pressure 4 CONCLUSION wave values are lower than the operating pressure of the fuel cell. Further, a third branch with a purging It is very difficult to obtain satisfactory humidification of valve is installed, allowing the removal of inert gases the PEFC membrane. A device by which excess water which inevitably accumulate inside the system. The is removed from the fuel cell is highly desirable. Two operation of this purging valve is managed by open- pressure waves are used to clear the hydrogen side of loop control every 30 minutes. the fuel cell of water droplets. Compared with con• ventional dead-end systems, a substantial increase in system efficiency is achieved with the hydrogen supply arrangement described. In addition, experiments show good long-term stability of the arrangement. Stati 3 Test Jenen Water droplets that are formed on the air side are "I ieferen :e" more easily removed from the fuel cell because of the much larger mass flow. Therefore, the need for addi• K tional devices is less urgent. However, it is assumed fr--«X ^x- that pulses will assist the removal of water droplets > 1 i—i r--—< i > and/or nitrogen blankets. Hence, further research will X focus on the expected gains of the scavenging effect ) c on the air side of the fuel cell. o Arrangements D & E • Arrangement B 5 ACKNOWLEDGEMENTS x Arrangement A Reference Financial support by the Swiss Federal Energy Office 1 1 1 1 1 1 1 is gratefully acknowledged. The authors thank Prof. Guzzella and Mr. M. Mladek (Measurement and Con• 0 10 20 30 40 50 60 70 80 trol Laboratory of the Swiss Federal Institute of Tech• Current [A] nology Zurich) for excellent technical support and Mr. R. Marcolongo (PSI) for mechanical assistance. Fig. 3: Polarization curves. 6 REFERENCES Polarization curves in Figure 3 show the performance of different arrangements. The measuring points de• [1] Carlstrom, CM. and W.B. Maynard (2000). Fuel note the mean value taken over a time span of 15 sec Cell with Selective Pressure Variation and after the system had settled down. As a reference, the Dynamic Inflection. US Patent 6093502. fuel cell stack was run on a static test bench where the [2] Ruge, M. and F.N. Büchi (2001). Bipolar fuel cell was operated under optimal conditions. The Elements for PE Fuel Cell Stacks Based on the operating temperature was 70°C, the relative humidity Mould to Size Process of Carbon/Polymer at the anode was 50%, and 70% at the cathode, the Mixtures. 1st European PEFC Forum, pp. 299. excess flow was 100% on both sides, and the system [3] Schott, P., J.-P. Poirot and P. Baurens (2000). pressure was 2 bara. The results are shown in Figure 3 by the solid line. Modélisation et Simulation de la Source d'Energie à Pile à Combustible du Véhicule Hydrogen. The crosses denote measurements made with ar• Colloque P.à C. et Interfaces pour le transport, rangement A. As can be seen clearly, the performance Belfort. 91 CURRENT DISTRIBUTION MEASUREMENTS IN PE FUEL CELL OF TECHNICAL RELEVANCE F.N. Büchi, A.B. Geiger R.P.C. Neto (Instituto Superior Técnico, Lisbon) Measuring local currents in PE fuel cells is an important tool for diagnostics and development. A semi- segmented cell has been developed, which can serve as an key instrument to investigate different phe• nomena in cells and stacks of technical relevance. Results with respect to water management are presented. 1 MOTIVATION the active area of the cell. Knowledge of the current distribution over the active area is useful for optimizing The performance of a PE fuel cell depends on many components and to support modeling. interdependent parameters. These are on the one hand the properties of the electrochemical compo• In principle two different approaches are feasible: (i) nents such as activity of the electro-catalyst, transport Construction of a model-cell, optimized for local properties of the electrode and conductivity of the current density measurements with respect to membrane. On the other hand the properties of the accuracy and resolution; (ii) Adopting a "real" cell with bipolar plate with respect to distribution of the gases the necessary "instrumentation". In the first case over the active area, heat dissipation properties and accurate measurements are possible, but these would electric conductivity in the bipolar arrangement influ• be difficult to be transposed to cells of technical ence the performance. Finally, also the operation importance, mainly due to scaling factors and thermal parameters such as gas pressures, gas management. In the second case the challenge is to stoichiometries, gas dew points, and cell temperature include the instrumentation for locally resolved current are important for the overall performance. A number of measurement without making changes to the gas flow the parameters are interlinked, and especially the field, thermal properties (cooling, temperature profiles) water management depends on several parameters or even the possibility of including the measurement such as water sorption and transport properties of the principle in a big, multi-cell stack. membrane and the electrodes, transport of water in the flow field, the cell temperature, gas dew points, 2 SEMI-SEGMENTED PLATE PRINCIPLE gas stoichiometries, and current density. The principle of adopting a real cell for the local cur• In a standard fuel cell experiment changing voltage or rent density measurements was chosen, because changing average current density of the cell is the only inclusion of the measurement principle into a big stack measurable response on variation of any of the should be possible. For this purpose a "semi-seg• parameters influencing the water management. The mented" cell was newly developed which allows for interpretation of the measurement with regard to opti• local current density measurements but conserves the mization of the cell performance remains difficult. This fluid dynamic properties, the electrical and thermal is because the reasons for the change in cell perform• properties exactly equivalent to those in a stack. The ance are not deductible in a straight forward manner. semi-segmented part of the cell may also be included There are several options to gain more information from such experiments, one of these is measuring the current density locally resolved at different locations of Air Flow Cooling Field Channel Cut for Segmentation Fig. 2: Arrangement of segments in semi-segmented Fig. 1 : Schematic of semi-segmented plate: A : plate. Arrow indicates schematic path of air flow in the molded low conductivity plate with flow field; B: high plate, flowing from manifolds B to C. Hydrogen flows conductivity graphite plate; C: metal current collector. in a similar manner from A to D. 92 as endplate in a stack. The semi-segmented endplate 4 RESULTS is shown schematically in Figures 1 and 2. It is based Single cells can be operated in different regimes, con• on the idea, that the highly conducting part of the stant current (CC) or constant voltage as the electrical plate, made from sintered graphite (p= 1 mQcm) is regimes and constant flow or stoichiometric flow (SF) completely segmented after being glued to the flow as the mass flow regimes. Out of the four possible field plate, while this thin, lower conducting flow field combinations the CC/SF regime is the one seen by a plate (pressure molded, equivalent to plates in a stack, cell in a stack, and therefore of practical interest. Con• p » 25 mQcm) remains intact and guarantees for stant current means that the total current must be unchanged electrochemical, fluid dynamics, and ther• carried by the cell. If in one location, i.e. due to drying, mal properties, as well as the compatibility with the the current density is reduced, then another segment stack. The molded flow field plate has a maximum of the cell has to produce more current. thickness of 1.5 mm, but an average thickness in the flow field of less than 1 mm and therefore communi• If the cell is operated under well humidified conditions cating currents between individual segments are (see Figure 3), the current density distribution in the acceptably small (resistance between segments is > cell is very homogeneous for À.air > 1.5. If the 1 mQ). stoichiometry is lowered, then the segments at end of the air path start to produce less current due to oxygen The location of the individual segments was chosen in depletion, and consequently the segments early in the order to cover the interesting parts of the active area, air path have to produce more current. At A,air = 1.1 namely the locations of air and hydrogen in- and out• the current density in the first segment (1) is almost 3 lets. These are in the corners of the flow field. The times higher than in the last segment (4). active area was split up in 10 segments, 9 small seg• ments of 10 cm2 and a big central segment of The situation is completely different if the cell is oper• 110 cm2. ated with air of a dew point of 30 °C (see Figure 4). Still, the oxygen depletion effect is observed at low 600 600 550 550 500 500 450 450 400 400 350 350 300 300 250 250 t 1 1 1 1 1 1 1 1 r 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 Air Stoichiometry [-] Air Stoichiometry [-] Fig. 3: Current density in the segments 1-4 as Fig. 4: Current density in the segments 1-4 as function of air stoichiometry. Avg. current density 400 function of air stoichiometry. Avg. current density 400 mA/cm2. Dew point of air 70 °C. mA/cm2. Dew point of air 30 °C. stoichiometries, but at high À.air the order of the 3 EXPERIMENTAL segments with respect to current density is reversed. The last segment in the air path (4) carries the highest Nation 112 and standard E-Tek electrodes (1 mg current. This is due to the drying of the membrane Pt/cm2 MEA) were used as electrochemical compo• (and increasing its resistance) early in the air path. nents. The dew point of the air increases along the path due In this report measurements of the local current den• to the product water and the current density increases. sity as function of air stoichiometry (A-air) and air These results show, that these kind of measurements humidity are reported. With respect to the other oper• are a very useful tool for investigation of the water ating parameters, the cell was operated under PSI management in PE fuel cells. standard conditions of 70 °C cell temperature, gas pressures of 2 barabs hydrogen stoichiometry of 2 and 5 ACKNOWLEDGMENT hydrogen dew point of 70 °C. The measurements reported are steady state data, acquired under isother• Development of multi-channel current measurement mal conditions (cooling water in- and outlet less than instrumentation by R. Eckl, and technical support from 0.5 °C difference). C. Marmy are gratefully acknowledged. 93 DEVELOPMENT OF A 40 kW FUEL CELL SYSTEM BASED ON AN ARRAY OF 6 POLYMER ELECTROLYTE FUEL CELL STACKS F.N. Büchi, M. Ruge (ETH Zürich), P.Dietrich, F.Geiger, P. Hottinger, CA. Marmy, R. Panozzo, G.G. Scherer, P. Rodatz (ETHZ), A. Tsukada, F. von Roth A 40 kW fuel cell system, based on an array of 6 Stacks of 125 cells each has been developed. Based on the modular nature of the fuel cell technology, the development of a 200 cm2 polymer electrolyte fuel cell served as nucleus for the system. Development of a bipolar element, in order to build stacks from the sin• gle cell and the manifolding of the stacks to an array were the important development steps. 1 INTRODUCTION 2 DEVELOPMENT STEPS In 1999 PSI and ETHZ took up the challenge to de• The first task in the development of the stack array velop and build a 40 kW fuel cell system as the base was the evaluation of the electrochemical components load unit of an advanced fuel cell super capacitor hy• (membranes from DuPont, electrodes from E-Tek) brid power train for a passenger vehicle [1]. The reali• and development of the final preparation procedures zation of such a challenging project with limited re• for these parts. Compromises had to be taken be• sources (< 20 man years) is possible, because one of tween maximum electrochemical performance and the advantages of the fuel cell technology is its modu• effort for preparation. larity. The second step was the development of a new bipo• lar plate, as described in detail in [2] in order to be Based on the science and technology developed for a able to build volume and weight efficient stacks. Also single cell with a power of less than 100 W, a con• for this task, not only performance was a relevant cri• verter being the heart of a power train for a fuel cell terion, but attention was also paid to the optimization electric car can be developed and realized. Many sin• of the manufacturing process of the bipolar plate. gle cells can be connected in series to multi-kW About 1100 bipolar plates were produced and leak stacks by developing an optimized bipolar element [2]. tested. For the assembly of the stacks a special in• The stacks then can be arrayed through thoughtful strument was developed. Eight stacks were built and manifolding to a multi-10 kW system. tested. The main problem found was the mechanical tolerance with respect to the depth of the flow field channels. Deviations as small as 0.12 mm made However, it must be born in mind, that the cells, stacks bipolar plates unusable, because the flow rate of the and stack-array themselves are not power producing process gas was then out of tolerance and the af• systems. An task equivalent to elaborating the con• fected electrochemical cell showed an extremely bad verter unit, is the development of the auxiliary sub- performance. This problem was found to be more units for fuel supply, air supply, cooling and controlling severe on the hydrogen side, because here the abso• of all the system components. This task is especially lute dimensions of the flow field channels are smaller demanding under the very restricted availability of than on the air side. packaging space in a vehicle. Some details of these 1.0 auxiliary system units are given elsewhere [3]. 0.9 The modularity of a fuel cell system however, does 08 also have disadvantages. The main disadvantage is E * V-Tfi^iijfcivÂ., the large number of parts, which are needed for pow• • ••^w•"¡I^LJJ•*••. erful systems. The array of six stacks shown in Figure Stack 1 2 contains more than 5000 parts. Most of these parts Stack 2 • ••••T- Stack 3 have to be handled, prepared, controlled and finally Stack 4 assembled individually. Except for few standard parts, Stacks such as screws, springs, and tie rods, all parts are Stack 6 Single Cell customized. A small error in one of these parts can be 1 1 1 1 1 detrimental for the performance of the entire array of 0 20 40 60 80 100 120 the 6 stacks. This requires an extreme carefulness for the preparation of the parts and assembly of the sys• Current [A] tem, which is a big challenge for academic institutions Fig. 1 : Current/voltage characteristics of a single cell such as PSI and ETHZ, normally dealing with much and of the six stacks (scaled down 1:125) used for smaller fuel cell systems. construction of the stack array. Conditions see text. 94 Otherwise the scale-up from a single cell (64 W) to a 125 cell stack (8 kW) could be realized with small deviations only. Figure 1 shows the current/voltage characteristics of the 6 stacks used for the construc• tion of the stack array and the characteristics of a single cell under standard test conditions (70 °C, cool• ing water exit temperature AT 5-8 °C, 2 barabs (exit) gas pressures, stoichiometries of 2 for both process gases, and dew points of 55° and 50° C for hydrogen and air respectively). The difference between the dif• ferent stacks is fairly low. The performance of stack 6 is slightly lower because this stack has been severely overheated during testing. The performance of the single cell is comparable to the average cell perform• ance in the stacks. This shows that design of bipolar plates and stacks as well as preparation procedures for all components were appropriate for this task. Third and last task is the assembling of six stacks to an array. In this array the stacks are connected gas- Fig. 3: Complete fuel cell system, array with six wise in a parallel. Electrically they are connected as stacks, and all auxiliary components on the power two parallel strings of 3 stacks in series in order to train test bench. match the voltage requirements of the power train. For The systems for air supply, hydrogen supply, cooling efficient manifolding of the process gases and the and control were developed simultaneously, and the cooling liquid, requiring 6 connections to each stack, stack array and the auxiliary systems were married. these media are connected to all stacks through a The complete system on the power train test bench is manifolding plate of a thickness of less than 10 cm, shown in Figure 3. delivering gases and coolant liquid with equal pressure drop to all stacks. Figure 2 shows the set-up of the 6- 3 RESULTS stack array including manifolding plate. The weight of the complete array is 185 kg (stacks 140 kg and mani• At the time of writing this report, the complete system folding plate and structure 45 kg). has not yet been tested up to full load and therefore the fulfillment of the specifications has not yet been proven. i— mu. 1 &tfítW i il i il.. J.. "vi'"m**"*^**- * 4 ACKNOWLEDGMENT Technical support from U. Bachmann (PSI), R. Mar- colongo (PSI) R. Neto and C. Siegenthaler and the PSI workshop as well as financial support by the Swiss Federal Office of Energy (BFE) are gratefully acknowledged. 5 REFERENCES [1] P. Dietrich, F.N. Büchi, M. Ruge, A. Tsukada, G.G. Scherer, R. Kötz, S. Müller, M. Bärtschi, P. Rodatz, O.Garcia, Fuel Cells for Transportation - A Pilot Fuel Cell Propulsion System, Proceedings 3k of the 8th European Automotive Congress, Brati• slava, Slovakia, June 18-20, 2001 [2] M. Ruge, F. N. Büchi, Bipolar Elements for PE Fuel Cell Stacks Based on the Mould to Size •I^HIIII Process of Carbon/Polymer Mixtures, Proceed• ings of the 1st European PEFC Forum, Lucerne, Switzerland, July 2-6, 399, 2001 Fig. 2: Array of six stacks of 125 cells each with [3] A. Tsukada, et al., PSI Scientific Report 2001, V, manifolding plate (below and left side). Total weight 88 (2002). 185 kg. 95 LONG-TIME PERFORMANCE OF RADIATION GRAFTED PSI MEMBRANES IN H2-O2 POLYMER ELECTROLYTE FUEL CELLS T.J. Schmidt, T. Rager, G.G. Scherer This contribution describes measurements on the long-time performance and stability of membrane elec• trode assemblies (MEA) based on radiation grafted and subsequently sulfonated FEP 25 membranes pre• pared at PSI. Under the experimental conditions (H2/O2 PEFC, 60°C to 80°C) no significant degradation of the PSI membranes could be observed in an evaluation period ofca. 2500 hours. 1 INTRODUCTION the membrane resistance (distance from the imagi• nary axis to the onset of the half circle), confirming One of the focuses in polymer electrolyte fuel cell that electrode degradation is responsible for the ob• (PEFC) research at PSI is the development of a low- served performance loss. cost polymer electrolyte membrane with similar prop• erties and performance than the state-of-the-art Nation membranes. Recently, similar PEFC perform• ance results as observed in Nation 112 based cells could be obtained with PEFC consisting of MEA's with radiation-grafted sulfonated FEP 25 membranes at 60°C over ca. 2000 h [1]. However, based on PEFC system aspects, an increase of the cell temperature to 80°C is highly favorable. Therefore, we investigated the long-time performance of PSI membranes at 60°C, 70°C, and 80°C, respectively. The total testing period was ca. 2500 hours. 2 EXPERIMENTAL The experiments were carried out using graphite- based single cells with a geometric active electrode 1000 1500 2000 2500 2 2 2 area of 30 cm (0.6 mgPtCm" , 0.6 mgnafioncm" ) on runtime [h] each electrode. Measurements were carried out at Fig. 1 : (a) Performance of a H2-02 PEFC with PSI 60°C, 70°C, and 80°C, respectively, ambient pressure, membrane at 0.5 Acm"2 over 2500 h at different tem• humidified H2 and dry 02 (A, = 1.5). The membrane peratures, (b) in-situ membrane resistivity over 2500 h was a radiation grafted and sulfonated FEP 25 (de• at 0.5 Acm . gree of grafting ca. 18 %, from hereafter called FEP) [2]. The membrane-electrode assemblies (MEA) were -4 hot-pressed according to [1]. o 50hat80°C e 680hat80°C 3 RESULTS -3 - CS The performance of the PEFC with a FEP membrane during ca. 2500 h is illustrated in figure 1a. The cell -2 - was constantly running at 0.5 Acm" . During the first 1000 h at 60°C, a constant power density of ca. -1 - 0.315 Wem"2 at 0.63 V could be observed. Subse• quently, during 500 h at 70°C, a slightly improved sta• ble power density was obtained (0.32 Wem'2 at 0.64 V). Finally, after switching to 80°C, the cell volt• 0 2 4 6 8 10 12 14 16 age was slightly decreasing as a result of the decreas• Re (Z) [míí] ing H2 partial pressure in the humidified gas stream. Close inspection of figure 1a shows that the perform• Fig. 2: Nyquist plot at 0.5 Acm"2 after 50 h and 680 h ance is also decreasing with time (ca. 0.05 mV/h). at 80°C, respectively (f=100mHz to 15kHz). However, based on in-situ membrane resistivity measurements (Figure 1b), it can be proven that ex• 4 REFERENCES cept the temperature induced changes, no increase in [1] J. Huslage, T. Rager, J. Kiefer, L.Steuernagel, the membrane resistivity can be observed, suggesting G.G. Scherer, in Micro-Power Sources , H.Z. that no membrane degradation took place. Electro- Massoud, I. Baumvol, M. Hirose, E.H. Poindexter chem. impedance spectroscopy (Figure 2) demon• (Eds.), ECS, Pennington, NJ, PV 2000-3 (2000). strate that the performance loss at 80°C is a result of an increasing charge transfer resistance (diameter of [2] T. Rager, D. Beckel, C. Noirtin, this Annex V, 97 the half circle in Figure 2) rather than an increase in (2002). 96 IMPROVEMENT OF THE INTERFACE IN MEMBRANE-ELECTRODE ASSEMBLIES BASED ON RADIATION-GRAFTED MEMBRANES J. Huslage, T. Rager, T.J. Schmidt, G.G. Scherer Recent progress is reported in preparing membrane-electrode assemblies (MEAs) for polymer electrolyte fuel cells based on radiation-grafted membranes. MEAs with an improved interface between the membrane and commercially available gas diffusion electrodes were obtained by Nafiorf-coating of the membrane and hot-pressing. The improved MEA showed both, performance data comparable to those of MEAs based on Nation® 112, and a good operation lifetime of more than 2000 h. 1 INTRODUCTION Both modifications resulted in markedly improved adhesion between membrane and electrodes, and Since the early 90ties radiation-grafted proton-con• lower charge transfer and membrane resistance. As a ducting membranes for fuel cells are developed at result of the improved interface, MEAs based on radia• PSI. Styrene and divinylbenzene are grafted onto base tion-grafted membranes showed fuel cell perfor• materials such as FEP, followed by sulfonation of the mances similar to Nation® 112 (Figure 1) [3] and long polystyrene part. Over all that time high performance term stability (Figure 2) at the same time. and durability have remained incompatible to a large extent. One of the major problems, poor mechanical 900 stability, was alleviated more recently by using ETFE as base material, but only at the expense of more 800 serious chemical degradation. 700 600 As an alternative strategy for improving the mechani• 500 cal properties we have therefore limited ourselves to membranes with rather low graft levels and focused 400 on thin membranes in order to compensate for losses 300 in conductivity. In addition, we concentrated on impro• Standard —•- 200 ving the membrane/electrode interface, since it had Nafion-coated + hot pressed —C— 100 been realized quite some time ago that MEAs with Nation 112 without hot-pressing —I— radiation-grafted membranes suffer from poor elec• 0 200 400 600 800 1000 1200 trode/electrolyte contact [1]. current density [mA/cm2] Fig. 1 : Performance of radiation-grafted membranes 2 EXPERIMENTAL (35 um thickness) in comparison with Nation® 112. 2 Radiation-grafted films were prepared in analogy to [2] 30 cm graphite cell, 60 °C, 1 atm, A,(H2) = A,(02) = 1.5, and subsequently sulfonated with 2 vol-% CIS03H in H2 humidified at 80 °C. CH2CI2. For surface coating, membranes were im• mersed in 0.5% ethanolic Nation® solution (EW 1100), dried at r.t. and heated to 130 °C for 2 h. The re-swollen membrane and ELAT-electrodes from E-Tek with 0.6 mg/cm2 Pt (20 % on C) and impreg• nated with solubilized Nation® (0.6-0.7 mg/cm2), were hot-pressed together by applying a compaction pres• sure of 50 bar. at 115 °C for 3 min. 3 RESULTS AND DISCUSSION Fig. 2: Long-term testing of the Nafion®-coated and A well-known technique for improving the contact be• hot-pressed membrane from Figure 1 at 60 °C. tween membrane and electrodes is hot-pressing. At• 4 REFERENCES tempts to apply this technique to our membranes had repeatedly failed because of brittleness and sensitivity [1] F.N. Büchi, B. Gupta, O. Haas, G.G. Scherer, toward drying out. The recent use of low irradiation Electrochim. Acta 40, 345 (1995). doses [2], graft levels of ~ 20 wt% and thin, flexible [2] T. Rager, D. Beckel, C. Noirtin et al., this Annex and more homogeneously grafted membranes led to V, 97 (2002). sufficiently improved mechanical properties to allow for hot-pressing. Additional improvement of the elec- [3] J. Huslage, T. Rager, J. Kiefer, L. Steuernagel, trode/electolyte interface was achieved by surface G.G. Scherer, in 'Micro-Power Sources', ECS coating of the membrane with solubilized Nation®. Proceedings Vol. 2000-3 (2000). 97 RADIATION-GRAFTED POLYMER FILMS WITH IMPROVED MECHANICAL PROPERTIES T. Rager, D. Beckel, C. Noirtin, P. Muff, S. Schweri, O. Haas, J. Huslage, G.G. Scherer The process of pre-irradiation grafting of styrene/divinylbenzene onto FEP has been improved with respect to the mechanical properties of the resulting copolymer films. Performing the reaction in a non-solvent for the polymers (FEP and newly formed polystyrene) resulted in a significant increase in radical lifetime. As a consequence a specific degree of grafting has become accessible with irradiation doses more than an order of magnitude lower than those used in earlier times. This greatly reduces radiation damage of the base material FEP and therefore alleviates a major reason for deterioration of mechanical properties in radiation grafting of perfluorinated materials. 1 INTRODUCTION with doses ranging from 1 kGy to 30 kGy and stored at -80 °C. Grafting reactions were performed by introduc• Radiation grafting has been used for several decades ing each film into 50 mL of the particular grafting solu• to modify polymers at the surface and in the bulk. tion in a gas washing tube with threaded joint. The Since the early 90ties radiation grafting of crosslinked solution was purged with N2 for 30 min and subse• styrene onto different base materials is applied at PSI quently heated to 60 °C in a water bath. The grafted as the first step for preparing proton-conducting mem• film was extracted with toluene over night and dried branes for fuel cells [1-3]. For many years the grafting under vacuum at 80 °C. The degree of grafting (de• step was performed in either benzene or toluene as fined as the ratio of PS to FEP) was calculated from solvent. This was based on the belief that a good sol• the initial and final weights of each film. vent for polystyrene should be used in order to in• crease swelling of the polystyrene phase and to facili• Stress-strain measurements were performed with an tate the access of monomer to the reactive sites this Instron 4464 instrument. Samples of 4 mm width and way [4]. 15 mm length were elongated at a rate of 100%/min. On the other hand for simultaneous-irradiation grafting 3 RESULTS AND DISCUSSION of styrene it was already observed in 1960 that increa• sed grafting rates are achieved when diluting the mo• Grafting reactions in different solvents were evaluated nomer with methanol [5]. A lower recombination rate by comparing the grafting kinetics in 1:1 mixtures of for radicals due to reduced swelling of the polymer (gel monomer and solvent (Figure 1). Assuming recombi• effect) was shown to be the origin of this pheno• nation to be the dominant pathway for radical loss, the menon. Since then non-solvents for the polymer have concave part of the kinetic curves may be approxima• been frequently used as dilutant in radiation-grafting. ted by Later it was shown that an additional improvement in degree of grafting = arln(1+(t-t )/T) grafting yields can be achieved by adding acids and 0 salts that shift the partitioning equilibrium of the monomer between the liquid and the solid phase to• with t0 representing a delay time caused by factors ward the latter (salting out effect) [6]. such as heating up of the solution and slow initiation. Here, we present the application of these concepts to i i i i i i ! i i i ! i i i ! i the grafting of poly(styrene-co-divinylbenzene) (PS) 70 onto poly(tetrafluoroethylene-cohexafluoropropylene) # * (FEP). It was the objective of these investigations to 60 •^2-Propanol make high graft levels more easily accessible in order to allow for a reduction in monomer concentration, ^ 50 Acetic acid reaction time and irradiation dose. The latter is of par• —• • ticular interest since it is well known that perfluorinated materials degrade at high irradiation doses, which is Methanol A obviously unfavorable for the mechanical properties of o THF the end product. re e o f graftin g Cyclohexane 2 EXPERIMENTAL 20 £ m 5? t— • Toluene 10 1 O All chemicals were purchased either from Fluka or Merck, mostly in purum quality, and used without fur• n r. . , ther purification. The monomer in all grafting solutions 0 4 8 12 16 consisted of styrene and DVB (80%) at a ratio of 9:1. time [h] Teflon FEP films of 25 urn thickness and a size of Fig. 1: Grafting kinetics in different solvents (irradia• 70 cm2 (-0.4 g) were electron-beam irradiated in air tion dose 10 kGy). 98 ing the elongation at break as a function of the degree Solvent a [h"1] h M m of grafting. Figure 3 clearly shows that the type of sol• 2-Propanol 0.9 145 0.09 vent used has no effect on the elongation at break by Acetic acid 0.9 500 0.02 itself. However, an increase of the irradiation dose Methanol 0.7 53 0.14 from 3 kGy to 30 kGy (as needed for achieving high THF 0.6 42 0.19 degrees of grafting in solvents such as toluene [7]) Cyclohexane 1.0 2x 105 5x 10"6 leads to a significant deterioration of the mechanical Toluene 1.0 105 10"5 properties. Table 1 : Fitting results from Figure 1. a> 1 kGy The parameter a gives the initial slope and t is an • 3 kGy indicator for the radical lifetime. As can be seen from o 30 kGy the fitting results in Table 1, high initial reaction rates • Toluene and long radical lifetimes are observed for reactions in • 2-Propanol the non-solvents 2-propanol and acetic acid. Radical • 2-Propanol/water lifetimes are even slightly higher in methanol and THF, but lower initial reaction rates indicate a somewhat less efficient monomer supply. On the contrary, initial reaction rates are high in toluene and cyclohexane, but at the expense of a much shorter radical lifetime. High grafting yields in 2-propanol and acetic acid can therefore be ascribed to a successful compromise between good monomer supply and fast radical re• combination. 10 20 30 40 50 degree of grafting [wt%] We attempted to profit from the solvent effect even more by further lowering the solvent quality. To do so, grafting reactions were performed in 2-propanol/water Fig. 3: Elongation at break for polymer films prepared mixtures. In order to avoid two-phase systems while with different solvents and irradiation doses. keeping the water influence as high as possible, water was added until the saturation limit was reached. The 4 CONCLUSION effect of water is nicely seen when looking at the graft• An appropriate choice of solvent in pre-irradiation ing yields as a function of monomer concentration grafting allows to work with drastically reduced irradia• (Figure 2). While all alcohols except methanol show tion doses and thus to improve the mechanical proper• almost identical concentration dependence of the ties of grafted films. grafting yield, significantly higher degrees of grafting are achieved in 2-propanol/water at low monomer 5 ACKNOWLEDGEMENT concentrations. We would like to thank M. Kristiansen and J. Visjager i 1 i 1 (ETH Zürich) for assisting at the stress-strain meas• 1 1 i 1 1 urements, and Adam Opel AG, GAPC (Mainz-Kastel) for financial support of this work. / 2-Propanol/water ç/^" 6 REFERENCES • / ^Ethanol X ~ 1 Á ° 1-Propanol\ [1] J. Huslage, T. Rager, T.J. Schmidt, G.G. Sche• o/ 2-Propanol \ c rer, this Annex V, 96 (2002). ic 1-Butanol \ CO 1_ f-Butanol \ O) / o • [2] T.J. Schmidt, T.Rager, G.G. Scherer, this Annex M— V, 95 (2002). o Methano1 —m , i i , i [5] G. Odian, M. Sobel, A. Rossi, R. Klein, J. Polym. 20 40 60 80 100 concentration [vol%] Sei. 55, 663 (1961). [6] P.A. Dworjanyn, B. Fields, J.L. Garnett, in: E. Fig. 2: Influence of the monomer concentration on Reichmanis, J.H. O'Donnell (eds), The Effects of the degree of grafting for different solvents (irradiation Radiation on High-Technology Polymers, ACS dose 3 kGy, reaction time 20 h). Symposium Series 381, 112 (1989). The effect of irradiation dose and grafting solution on [7] H.-P. Brack, G.G. Scherer, Macromol. Symp. the mechanical properties was evaluated by measur• 126, 25 (1997). 99 NOVEL MEMBRANES FOR APPLICATION IN DIRECT METHANOL FUEL CELLS A.B. Geiger, T. Rager, G.G. Scherer, A. Wokaun Different radiation-grafted proton conducting membranes based on perfluorinated ethylene-propylene copolymer films (FEP) were investigated under direct methanol fuel cell (DMFC) operating conditions. The effect of the variation of membrane properties such as the degree of graft level and the degree of cross- linking on the DMFC performance and on the methanol cross-over were studied in single cell tests. Ex• perimental results are shown for an aqueous methanol fuel feed of 0.5 M at an operating temperature of 90 and 110°C, respectively. 1 INTRODUCTION at 60°C and hereon preheated to the cell temperature. Aqueous methanol solution was preheated to cell DMFCs using polymer electrolytes could provide an temperature and fed to the anode at a constant flow attractive alternative to fuel cells operating on refor• rate of about 10 ml/min. - A flow rate of 10 ml/min of a mate as power sources for portable and vehicular 0.5 M aqueous methanol solution corresponds to a applications. However, the development of DMFC stoichiometry of 8 at a current of 6 A. The pressure at systems is hindered at present by a number of prob• the anode as well as at the cathode side was 3 barabs. lems. Among these, one of the main obstacles today is the methanol permeability of commercially available Since the methanol permeation rate across the mem• proton conducting membranes such as Nation®, be• brane is an important factor not only affecting the cause the methanol cross-over to the oxygen/air cath• DMFC performance but also the efficiency of the ode causes losses in terms of lost fuel and depolariza• DMFC system, the leakage rates of methanol across tion of the cathode. In consequence, the overall effi• the membrane were determined by monitoring the ciency of a DMFC system is lowered considerably. C02 concentration in the effluent of the cathode Furthermore, commercially available proton conduct• stream. It was assumed that the entire methanol that ing membranes are a significant cost factor for the reached the cathode was converted to C02 and that entire DMFC system [1]. Therefore, it is a major con• cern to develop low-cost polymer electrolytes with low the membrane is impermeable for any C02. Methanol methanol permeation. leakage rates will be presented in current densities that correspond to the current produced by total oxida• Based on the experience obtained with the process of tion of methanol. radiation grafting and subsequent sulfonation to pre• pare membranes for use in hydrogen fuel cells (e.g. 3 RESULTS AND DISCUSSION [2], [3]), novel polymer electrolytes with varying mem• The cell performance data of the differently grafted brane properties were prepared and investigated un• membranes are given as polarization curves in Figure der DMFC operating conditions. 1 for type I membranes and in Figure 2 for mem• branes of type II. Figures 1a and 2a display the polari• 2 EXPERIMENTAL zation curves for an operating temperature of 90°C The DMFC tests were performed in a single cell with and in Figures 1 b and 2b, the cell data are shown for an active area of 30 cm2. The flow-field plates were a temperature of 110°C. The corresponding methanol made of graphite comprising serpentine flow channels leakage of each membrane is shown in the insets of for the supply of the reactants and the removal of the Figures 1 and 2. products. The anode consisted of a Pt-Ru catalyst and For membranes of type I an optimum in cell perform• the cathode of a Pt catalyst with 1 and 4 mg/cm2 Pt- ance is obtained for both temperatures at a degree of loading, respectively. All membranes investigated graft level of 12 wt.%, as shown in Figure 1. At 90°C were based on FEP polymer films with a thickness of and a cell voltage of 0.5 V, a current density of 200 25 u~i (FEP 25). Lower cross-linked FEP 25 mem• mA/cm2 and at 110°C, a slightly higher current density branes have been studied at degrees of graft level of of 225 mA/cm2 is obtained for the best membrane (12 8, 12, 15, and 21 wt.%. The cell performance and wt.% graft level). However, the dependency of the cell methanol permeability of highly cross-linked mem• performance on the degree of grafting is smaller with branes were investigated at degrees of graft level of increased cell temperature (Figure 1b). The methanol 10, 12, and 14 wt.%. To avoid any misunder-standing leakage of type I membranes nicely correlates with lower cross-linked membranes will be indicated as the degree of graft level at an operating temperature type I membranes; type II membranes will refer to of 90°C (inset of Figure 1a). The lowest grafted mem• higher cross-linked polymer electrolytes. brane (8 wt.%) has a methanol leakage current den• For each MEA, the cell data were obtained at operat• sity of 64 mA/cm2, while the highest grafted mem• ing temperatures of 90 and 110°C for a 0.5 M aque• brane shows a methanol leakage current density of ous methanol fuel feed. All MEAs were investigated 110 mA/cm2 at a current density of 200 mA/cm2. In with air as oxidant at a stoichiometry of 2 and a mini• contrast, at 110°C the methanol leakage is essentially mum airflow rate of 0.3 l/min. The air was humidified the same for all membranes (155 mA/cm2 @ 100 CD ü 8wt.% # 12wt.% —M— 15wt.% 0.3 -V- 21 wt.% " 0.5 0.3 100 200 300 300 Current Density [mA/cm ] Current Density [mA/cm ] Fig. 1 : Cell data of differently grafted type I mem• Fig. 2: Cell data of highly cross-linked membranes branes based on FEP 25. The polarization curves (type II) based on FEP 25. In Figure 2a, the polari• given in Figure 1a were measured at 90°C; the data zation curves are given at 90°C; the data shown in given in Figure 1 b were obtained at 110°C. Figure 2b were obtained at 110°C. 200 mA/cm2) except for the lowest grafted membrane degree of graft level at a cell temperature of 90°C, as (108 mA/cm2). shown in the insets of Figures 1a and 2a. Figure 2 indicates that higher cross-linked membranes 4 SUMMARY (type II) have an optimum in cell performance for a Radiation-grafted cross-linked membranes were suc• degree of graft level of 14 wt.% at 90 and 110°C. For cessfully short-term tested under DMFC operating this membrane a current density of 190 mA/cm2 is conditions at 90 and 110°C. So far, an optimum in cell obtained at a cell voltage of 0.5 V for both tempera• performance has been achieved with low cross-linked tures. Once more, the differences in cell performance FEP 25 membranes with a graft level of about 12 of the differently grafted membranes almost vanishes wt.%. However, the methanol leakage across the at the higher temperature and is only 17 mA/cm2 at a polymer electrolyte for membranes of type I is the cell voltage of 0.5 V (Figure 2b). The methanol leak• highest. As shown, the methanol permeation rate can age of type II membranes also correlates well with the be reduced by increased cross-linking of the mem• degree of grafting at 90°C and is in the range between brane (type II membranes) while only slightly affecting 64 and 76 mA/cm2 at a current density of 200 the cell performance. mA/cm2, as depicted in the inset of Figure 2a. At the 5 ACKNOWLEDGEMENT higher cell temperature of 110°C, the methanol cross• over is also increased and is in the range between Financial support of the Adam Opel AG, GAPC, is 103 and 138 mA/cm2 at a current density of 200 gratefully acknowledged. mA/cm2. However, a clear correlation of the methanol 6 REFERENCES leakage with the degree of graft level cannot be ob• served (inset of figure 2b). A reason for the higher [1] A.S. Arico, S. Srinivasan, V. Antonucci, DMFCs: methanol cross-over of the membrane with a degree From Fundamental Aspects to Technology De• of graft level of 12 wt.% is not known yet. velopment, Fuel Cells 1, 133 (2001). [2] J. Huslage, T. Rager, J. Kiefer, L. Steuernagel, In the investigated graft level range, both types of G.G. Scherer, in Micro-Power Sources, H.Z. membranes show an optimum in cell performance for Massoud, I. Baumvol, M. Hirose, E.H. Poindexter a specific degree of graft level at 90°C. For both types (Eds.), The Electrochemical Society, Pennington, of membranes the cell performance is slightly in• NJ, PV 2000-3 (2000). creased at higher operating temperature and the in• fluence of the degree of grafting on the polarization [3] H.-P. Brack, G.G. Scherer, Modification and curves is smaller. However, the methanol leakage of characterization of thin polymer films for electro• both types of membranes also increases with an in• chemical applications, Macromol. Symp. 126, 25 crease in cell temperature and with an increase in the (1997). 101 ACTIVATION OF EDGE-PLANE PYROLYTIC GRAPHITE ELECTRODE SURFACES BY MECHANICAL ABRASION FOR ATTACHING SULFONIC ACID GROUPS B. Steiger, G.G. Scherer Aromatic sulfonic acid groups could be attached to edge-plane pyrolytic graphite electrode surfaces by reaction of the dangling bonds generated by mechanical abrasion of the graphite surfaces with aqueous solutions of salts of 4-vinylbenzenesulfonic acid. The modified electrodes were investigated by cyclic volt- 3+ ammetry of electrostatically bound Ru(NH3)6 to the sulfonate groups. 1 INTRODUCTION 3 RESULTS AND DISCUSSION The formation of covalent bonds between carbon The modification of edge-plane pyrolytic graphite elec• electrode surfaces and chemical reagents is an impor• trode surfaces with 4-vinylbenzenesulfonate by me• tant method in the molecular design of carbon elec• chanical abrasion as described in the experimental trode surfaces [1,2]. Covalently attaching molecules to section was demonstrated by the electrostatic attach• the surface of carbon electrodes usually involves sur• 3+ ment of Ru(NH3)6 to the sulfonate groups (Figure 1) face carbon-oxygen functionalities such as oxides, and subsequent cyclic voltammetric experiments. hydroxides or carboxylates [2,3]. With the goal of pro• ducing high coverages of desired functionalities, the s 3 carbon electrode surface is exposed to strong oxida• tion processes, resulting in difficulties to identify and -~0~ ° " _, _ NH3 k control the nature and number of carbon-oxygen 1 /=\ H3N I NH3 groups. The desire to develop alternative strategies for modifying carbon electrode surfaces lead to meth• _ _ NH3 ods for producing oxide-free carbon. These include thermal cleaning [4], argon plasma etching [5], and mechanical abrasion in the presence of vinyl- ferrocene, vinylpyridine [6], and ammonia [7]. Avoiding Fig. 1 : Schematic picture of electrostatically attached oxidative processes by grafting functionalized aryl 3+ radicals produced from electrochemical reduction of Ru(NH3)6 to the phenylsulfonate groups bound to diazonium salts has recently gained much attention the graphite surface. [8-10]. Considering the simplicity of the mechanical abrasion method we were attracted to examine the Well defined cyclic voltammograms showing the typi• reaction of activated edge-plane pyrolytic graphite cal characteristics for surface attached redox-systems electrode surfaces with aqueous solutions of salts of were obtained (Figure 2). 4-vinylbenzenesulfonic acid. Pronounced changes in 8-1 1 surface properties can be expected upon attaching strong acidic sulfonic acid groups. 2 EXPERIMENTAL Pyrolytic graphite (ultra-pure, extremely anisotropic, density of 2.18 - 2.22 g cm3) with the edge of the graphite planes exposed was obtained in the form of cylindrical rods 6.35 mm in diameter (Advanced Ce• ramics Co.). Short segments of the rods were either mounted on shafts with heat-shrinkable polyolefin -6- tubing (Alpha Wire Co.) to construct electrodes for -800 -600 -400 -200 0 200 400 600 800 cyclic voltammetry or directly used for X-ray photo• electron spectroscopy. The base of the cylindrical Potential [mV] (vs Ag/AgCI) segments was abraded on 600-grit SiC paper (3M 3+/2+ Co.) in aqueous solutions (1 M) of 4-vinyl• Fig. 2: Cyclic voltammogram of the Ru(NH3)6 benzenesulfonic acid sodium (or potassium) salt couple electrostatically attached to the phenyl- (Fluka) followed by washing and sonication in purified sulfonate groups bound to the electrode surface. The water. The modified graphite electrodes were im• dotted curve was recorded with an electrode that had been abraded in pure water followed by immersion mersed in an aqeous solution (1 mM) of [Ru(NH3)6]CI3 (Alfa Aesar Co.) for 1 min followed by washing with into [Ru(NH3)6]CI3 solution. Supporting electrolyte: purified water and transferring to a pure supporting 0.01 M Na2S04 saturated with nitrogen. Scan Rate = electrolyte for cyclic voltammetric measurements. 50 mV s-1. 102 The background current (dotted curve) arises from We believe that the strong adsorption observed after double-layer charging. The pair of current peaks near mechanical abrasion of the electrode surface, is re• 3+/2+ sulting from a covalent attachment of the phenyl- -300 mV arises from the Ru(NH3)6 couple electro• statically attached to the phenylsulfonate groups sulfonate groups by cycloaddition of 4-vinylbenzene• bound to the graphite surface. The formal potential of sulfonate to dangling bonds (Figure 4) formed by me• chanical abrasion in analogy to the chemistry pro• -294 mV (vs Ag/AgCI reference electrode) is essen• posed by Mazur [4]. tially identical to the one measured for a Nation® 3+ coated electrode in which Ru(NH3)6 was incorpo• rated (-290 mV). The peak currents in Figure 2 were stable for many scans. When the cyclic voltammetric experiment was repeated in 0.5 M Na2S04 as the supporting electrolyte, the response for the 3+/2+ Ru(NH3)6 couple disappeared during a few scans, 3+/2+ showing that the Ru(NH3)6 cations undergo fast cation exchange with the sodium ions in the support• ing electrolyte. Cyclic voltammograms of electrodes that were not Fig. 4: Reaction scheme for the cycloaddition of 4- thoroughly washed with purified water prior to the vinylbenzenesulfonate to dangling bonds formed by 3+ binding of Ru(NH3)6 showed a gradual decrease of mechanical abrasion of edge-plane pyrolytic graphite 3+/2+ the currents corresponding to the Ru(NH3)6 cou• surfaces (crystallographic orientation {112/} shown). ple, indicating desorption of physisorbed 4-vinyl- benzenesulfonate. The time dependence of the de• X-ray photoelectron spectroscopy also revealed the sorption of 4-vinylbenzenesulfonate as a function of presence of sulfur on the surface of the edge-plane the coverage is shown in Figure 3. After about 30 min pyrolytic graphite as peak at 168 eV (S2p). No sulfur the coverage became steady as shown by the dotted impurities were detected on graphite that was abraded line in Figure 3. Some of the sulfonate groups are in air or purified water. apparently much stronger bound. A coverage of about 10 2 3+ 2 x 10" mol cm" (geometric area) Ru(NH3)6 re• 4 ACKNOWLEDGEMENTS mained unchanged, even after prolonged extraction We are grateful to Dr. Bernhard Schnyder for XPS with purified water. measurements and to Ursula Paulus for numerous helpful discussions. 10-| 1 9- 5 REFERENCES [1] R.W. Murray, Acc. Chem. Res. 13, 135 (1980). [2] R.W. Murray, in: A.J. Bard (Ed.), Electroanalytical Chemistry, Marcel Dekker, New York, 13, 191 (1984). [3] R.L. McCreery, in: A.J. Bard (Ed.), Electro- analytical Chemistry, Marcel Dekker, New York, 17, 221 (1991). 1- [4] S. Mazur, T. Matusinovic, K. Cammann, J. Am. 0T 1 1 1 1 ' 1 1 1 1 1 1 —r Chem. Soc. 99, 3888 (1977). 0 10 20 30 40 50 60 Desorption Time [min] [5] N. Oyama, A.P. Brown, F.C. Anson, J. Electro- anal. Chem. 87, 435 (1978). Fig. 3: Desorption of 4-vinylbenzenesulfonate into [6] R. Nowak, F.A. Schultz, M. Umaña, H. Abruña, water. The coverage, r, was evaluated by measuring R.W. Murray, J. Electroanal. Chem. 94, 219 the area (after correction for background currents) (1978). defined by the anodic peak in cyclic voltammograms [7] A. Anne, B. Blanc, J. Moiroux, J.-M. Savéant, like the one in Figure 2. Langmuir 14, 2368 (1998). The behavior shown in Figure 3 could be repeated by [8] M. Delamar, R. Hitmi, J. Pinson, J.-M. Savéant, exposing the electrodes to aqueous solutions of salts J. Am. Chem. Soc. 114, 5883 (1992). of 4-vinylbenzenesulfonic acid without mechanical [9] P. Allongue, M. Delamar, B. Desbat, O. Fage- abrasion of the graphite surface, followed by attach• baume, R. Hitmi, J. Pinson, J.-M. Savéant, J. Am. 3+ ment of Ru(NH3)6 to the vinylbenzenesulfonate Chem. Soc. 119, 201 (1997). groups. However, the coverage gradually decreased below the dotted line in Figure 3. After about 60 min [10] C. Saby, B. Ortiz, G.Y. Champagne, D. Bélanger, essentially all 4-vinylbenzenesulfonate had desorbed. Langmuir 13, 6805 (1997). 103 HYDROGEN PRODUCTION BY METHANOL REFORMING: POST-REACTION CHARACTERISATION OF A Cu/ZnO/AI203 CATALYST F. Raimondi, K. Geissler, J. Wambach, A. Wokaun Post-reaction X-ray photoelectron spectroscopy (XPS) experiments have been carried out after exposure of a commercial Cu/ZnO/AI203 catalyst to methanol reforming conditions in the presence of 02 and H20. It was found that the Cu oxidation state and the Cu surface concentration were strongly influenced by the applied reaction conditions. 1 INTRODUCTION Hydrogen is expected to play a major role in the future as a carbon free energy-carrier. Efficient and safe storage of hydrogen with a reasonable energy density could be achieved by the use of liquid organic hydro• gen carriers, such as methanol. Various reactions can be used for the production of hydrogen from metha• nol: 1 CH3OH + /2 o2 -> C02 + 2 H2 [dry partial oxidation (dry POX)] CH3OH + H20 -» C02 + 3 H2 [sfeam reforming] 912 914 916 918 920 922 1 (n+1) CH3OH + n H20 + /2 02 -> (n+1) C02 + (3n+2) H2 Kinetic Energy [eV] [wet partial oxidation (wet POX)] Fig. 1 : XPS Cu LMM spectra after wet POX. Among these reactions, methanol wet POX is consid• ered the most promising option for practical applica• 0.35- ••••O- methanol dry POX (0,/CH3OH = 0.42) tion in non-stationary systems [1]. This is due to the methanol decomposition (0,/CH3OH = 0) —a—methanol wet POX (OJCHflH = 0.1 fact that the thermal balance of the reaction can be 0.30- H„0/CH,OH = 0.75) controlled by changing the H20/02 ratio in the feed. 0.25- In the present study, the state of the catalyst after o exposure to various methanol reforming conditions ISS 0.20- S after reduction was studied by XPS as a function of the reaction tem• Q. CM 0.15' perature and of the 02/CH3OH ratio in the feed. The XPS analysis was carried out without exposing the 0.10- catalyst to air after the catalytic test. Ü 0.05- 2 RESULTS AND DISCUSSION 0.00 460 600 Figure 1 shows the XPS Cu LMM spectra collected T[K] after exposure of the catalyst to wet POX conditions Fig. 2: XPS Cu 2p3/2/Zn 2p3/2 atomic ratio after expo• (02/CH3OH = 0.1 and H20/CH3OH = 0.75) at various sure to various reaction conditions. temperatures. Decreasing the reaction temperature caused an increase of the Cu oxidation state. At 470 methanol dry POX conditions, the Cu surface concen• K Cu was prevalently in the +2 oxidation state and the tration decreased for T > 530 K, probably due to par• catalytic activity towards H2 production was very low. tial encapsulation of the Cu crystallite size by ZnO. A similar trend was observed after exposing the cata• This effect was not observed under wet POX condi• lyst to dry POX conditions. However no Cu(ll) was tions. Since the decrease of Cu surface area is the observed in this case and the catalyst maintained its main cause of catalytic activity loss, the absence of activity over the whole range of reaction conditions Cu crystallite coverage under wet POX conditions tested. implies that the catalyst stability is enhanced by the presence of water in the feed. Under wet POX condi• Figure 2 shows the variation of the XPS Cu 2p3/2/Zn tions at T < 510 K, the Cu surface concentration in• 2p3/2 atomic ratio with the reaction temperature for creases due to spreading of CuO on the surface. various feed compositions. The XPS Cu 2p3/2/Zn 2p3/2 atomic ratio is a measure of the Cu concentration in 3 REFERENCES the surface region of the catalyst (analysed thickness < 3 nm). The Cu surface concentration resulted unaf• [1] K. Geissler, E. Newson, F. Vogel, T.-B. Truong, fected by exposure of the catalyst to methanol de• P. Hottinger, A. Wokaun, Phys. Chem. Chem. composition conditions up to 590 K. However, under Phys. 3, 289-293 (2001). 104 PULSED REACTIVE CROSSED-BEAM LASER ABLATION OF LaoeCao^CoOs FOR THE PREPARATION OF ELECTROACTIVE THIN FILMS M.J.Montenegro, T. Lippen, S.Müller, A. Wokaun, P.R. Willmott (University of Zürich), A. Weidenkaff (University of Augsburg) La0.eCaoACo03 (LCCO) films are deposited on MgO(001), stainless steel and gold by a congruent material transfer from their target using pulsed reactive crossed-beam laser ablation. The quality of the deposited films was analysed by XRD and HRTEM. The analysis suggests that the deposition as well as the cooling conditions play an important role for the film quality. 1 INTRODUCTION er intensity of the LCCO(200) peak indicates that the LCCO is preferentially orientated in this direction. Perovskite type oxides (AB03) with high conductivity are promising candidates in electrochemistry as cata• lysts for solid oxide fuel cells [1] and metal-air batter• ies [2]. The perovskites containing a lanthanide in A and a transition metal in B show high catalytic activity for several reactions. Particularly, the perovskites containing Co, Mn, Fe, Cu and Ni reveal catalytic ac• tivity for oxygen evolution while pyrochlores reveal LCCO (200) superior properties for oxygen reduction. LCCO was LCCO applied as bifunctional catalyst for metal-air batteries (110) by Mueller et al. [2]. To study and compare the mechanism of the oxygen reaction on different mate• rials, it is necessary to prepare electrodes with a well defined interface, where the substrate is inactive for the desired reaction. One candidate for the prepara• tion of these model electrodes is pulsed reactive crossed-beam laser deposition (PRCLA), which has been successfully applied to the growth of many types Fig. 1 : XRD spectra of the LCCO films. A: cooling of multicomponent materials [3]. with oxygen background. B: cooling without oxygen background. 2 EXPERIMENTAL LCCO films were deposited using a KrF excimer laser 4 CONCLUSION from a rotating (stoichiometric) La0.6Ca0.4CoO3 target. The films were grown on MgO(001), stainless steel The analytical data reveal, that the LCCO film have a (SS), and gold substrates (10 x 10 x 0.5 mm). The high crystallographic orientation and quality. In gen• films were characterized by Rutherford Back Scatter• eral, better film qualities are obtained for cooling with• ing (RBS), X-ray Diffraction (XRD) and X-ray photo• out oxygen, independent on the cooling rate. HRTEM electron spectroscopy (XPS) analysis. The electro• shows that the films grow epitaxial on the MgO sub• chemical activity of the LCCO films for oxygen strate. After electrochemistry measurements the or• generation was measured with a three electrodes dered perovskite structure keeps almost unchanged arrangement. except an amorphous layer of a few nm thickness on the surface. 3 RESULTS AND DISCUSSION 5 REFERENCES The films obtained by PRCLA present the same stoichiometry as the target, i.e. Lao 6Ca0.4CoO3. The [1] J.T. Cheung, E.D. Morgan, D.H. Lowndes, X.Y. variation in the stoichiometry, calculated from the RBS Zheng and J. Breen, Appl. Phys. Lett. 62, 2045 spectra, is ca. 5%. The XRD analysis of the films indi• (1993). cates that cooling of the LCCO films in absence of [2] S. Müller, O. Haas, C. Schlatter and C. Comni- oxygen produce only LCCO(200) with a peak at nellis, J. Appl. Electrochem. 28, 305 (1998). 47.97° (Figure 1B). If the cooling is carried out in the presence of oxygen (8x10'4 mbar), LCCO(200) and [3] P.R. Willmott, J.R. Huber, Rev. Mod. Phys. 72, LCCO(110) peaks are observed (Figure 1 A).The high• No. 1 (2000). 105 FABRICATION OF MICROOPTICAL ELEMENTS IN QUARTZ BY LASER - INDUCED BACKSIDE WET ETCHING G. Kopitkovas, C. David, T. Lippert, A. Wokaun Quartz was structured by laser-induced back side wet etching. With this method quartz can be structured with micrometer precision using the 4-th harmonic of a NdP+:YAG laser, a solution of pyrene in acetone and laser fluences well below the damage threshold of quartz. 1 INTRODUCTION Q The miniaturization of optical and mechanical ele• L2 PH LI ments is a driving a revolution in modern optics, medi• 266 nm cine and sensorics. Arrays of microoptical elements, especially in quartz are applied as beam homogeniz- ers for high power excimer and Nd3+:YAG lasers. Quartz is an important material in optics and optoelec• tronics, because it is transparent over a wide wave• J J j 7M, length range, has a strong damage resistance for +, laser irradiation, and a high thermal and chemical Nd :YAG KDP KTP Il H IV H stability. However, these properties make it difficult to fabricate microelements in quartz. There are several ways to fabricate microoptical elements in quartz Fig. 1: Experimental setup. (M1, M2: Mirrors, L: lens glass; i) by electron beam lithography [1], ii) by struc• (f=100 mm), Q: quartz plate). turing with VUV lasers (e.g. 157 nm), iii) by structuring with femtosecond lasers and iv) by laser - induced backside wet etching (LIBWE). The latter method was used for the high resolution laser ablation of fused silica using a pyrene-acetone solution [2]. It has been suggested, that a cyclic multiphotonic absorption process of pyrene "superheats" the solution at the quartz-liquid interface, resulting in etching of the is quartz [3]. This takes place with fluences below the 0 ablation-damage threshold of quartz [4]. eooimn 2 EXPERIMENT 600pm GOOiim A quartz glass plate with a thickness of 0.5 mm was 200pm used as sample. A quadrupled nanosecond Nd3+:YAG laser (266 nm, FWHM 5 ns, Quantel) was applied as irradiation source. The wet etching solution was Fig. 2: 3D profile of the laser ablation in the quartz pyrene in aceton at a concentration of 0.4 mol/l. The sample. experimental set up is shown in Figure 1. 4 REFERENCES 3 RESULT AND DISCUSIÓN [1] C. David, T. Lippert, J. Wei, A. Wokaun, Micro- elec. Eng., 57-58, 453 (2001). The Nd3+:YAG laser was applied, because the spatial and temporal coherence may allow to fabricate micro [2] J. Wang, H. Niino, A. Yabe, Appl. Phys. A. 69, diffractive gratings by using an interference setup 271 (1999). similar to Ref. [5]. The disadvantages of the Nd3+:YAG laser is the intensity profile of the beam, i.e. super- [3] H. Fukumura, M. Masuhara, Chem. Phys. Lett. Gaussian. The etch profile was measured with a pro• 221,373 (1994). filer (Dektak-8000). A 3D scan is shown in Figure 2. [4] J. Wang, H. Niino, A. Yabe, Appl. Surf. Sei. 154- The profile does not follow a smooth curve but exhib• 155, 571 (2000). its diffraction rings. If the diffraction rings can not be eliminated it will be difficult to apply this laser for the [5] T. Lippert, T. Gerber, A. Wokaun, Appl. Phys. fabrication of microoptical elements in quartz. Lett. 75, 1018(1999). 106 COMPARISON OF LIBS AND LA-ICP-MS FOR THE ANALYSIS OF TRACE METALS K. Meissner, T. Lippeñ, A. Wokaun, D. Günther (ETH Zürich), U. Pfeifer-Fukumura (FH-Wiesbaden) Trace metals in heterogeneous matrices were analyzed with LIBS and LA-ICP-MS. LIBS is less sensitive to the sample preparation than LA-ICP-MS. The detection limits of LA-ICP-MS are lower than for LIBS. The influence of different parameters, such as oxidation states of the trace metals, on the detection limits have been analyzed for LIBS. 1 INTRODUCTION For example, Cu can be detected with LIBS down to 10 ppm, while LA-ICP-MS allows detection below 5 Laser-induced Breakdown Spectroscopy or LIBS [1], ppm. The detection limit of Cr with LIBS is dependent is an elemental analysis method in which a focused on its oxidation stage, but is typically between 5 and laser pulse is directed onto a sample surface. The 50 ppm (shown in Figurel). energy from the pulse heats, vaporizes, atomizes, and ionizes the material. This results in a hot plasma, from which excited atoms and ions emit light that is ana• lyzed with a spectrometer. This allows the detection of most elements by their unique spectral signatures [2]. LA-ICP-MS (Laser ablation inductively coupled f plasma mass spectrometry is another laser ablation I 150000 - based analytical technique [3]. The laser pulse is used to ablate the sample and the ablated material is trans• ported by an argon flow to the secondary plasma source. The material is dissociated and the atoms are ionized in the plasma and subsequently analyzed in a quadrupole mass spectrometer. The ions are sorted by mass and detected using a scanning electron mul• Fig. 1 : Comparison of the emission intensity for dif• tiplier. ferent Cr-compounds. LA-ICP-MS is the standard method for analysis of The organic Cr(lll) compound and Cr(ll)chloride reveal trace elements (less then 1 ppm). The preparation of the highest signal intensity, while Cr(lll)oxide has the the sample is very important for quantitative determi• highest detection limit. nations. The samples should have a very homogene• ous dispersion and the best results are obtained with Another important parameter for the detection limit glass matrices. LA-ICP-MS is a laboratory-based and accuracy is the irradiation wavelength. The abla• technique and can, contrary to LIBS, not be used for tion rate is for the same laser fluence 10 times higher field measurements. for 308 nm irradiation (6 |am/pulse) than for irradiation with 193 nm (0.5 uxn/pulse). Irradiation with 193 nm LIBS can be used as complementary analysis method and larger ablation diameter result also in higher and is suitable for screening analysis, to select sam• emission intensities for the same amount of ablated ples, e.g. of soil, which should be measured with a material. high resolution method, such as LA-ICP-MS. Different parameters which influence the detection limits and 3 CONCLUSION accuracy are investigated in this study. The study shows that LIBS can be used for screening The samples were prepared (matrix: 80% KBr, 15% analysis. The detection limit is dependent on the metal CaC03 and 5% Al203; trace of metals: Cu, Cr, Pb) by and its oxidation stage, but less on the sample prepa• pressing pellets containing various amounts of the ration. trace metal. The pellets were then analyzed by both analytical techniques. 4 REFERENCES [1] L.J. Radziemski, D. A. Cremers, (eds.), Laser- 2 RESULTS AND DISCUSSION Induced Plasmas and Applications, Marcel Dek- The results of this study show that the sample- ker, New York, 1989. preparation has only a minor influence on the detec• [2] U.S. National Report to IUGG, 1991 -1994, tion of LIBS (RSD < 10%). Samples with a high metal Rev.Geophys.Vol.33, 1995 American Geophysi• concentrations, i.e. > 500 ppm, were not homogene• cal Union. ous, resulting in variation of the LA-ICP-MS data by more than 100% especially in the case of Pb. The [3] D. Günther, C. A. Heinrich, J. Anal. At. Spectrom. detection limits of LIBS and LA-ICP-MS are different. 14, 1369 (1999). 107 FABRICATION OF RIE MASKS BY ArF LASER ABLATION OF THIN METAL FILMS ON GLASSY CARBON M. Kuhnke, C. David, T. Lipped, G.G. Scherer, A. Wokaun Metal masks for reactive ion etching of glassy carbon (GC) were fabricated by metallizing the GC sub• strates and subsequent ablation of the metal films. The metal layers consist of a thin adhesion promoting Cr layer and a thick layer of Al on top, deposited by thermal evaporation or sputtering. The ablation thresholds of bulk AI, the GC substrate and metal films of different thickness are determined. 1 INTRODUCTION 500 :\i AB CD Structuring of glassy carbon by various methods has I 400 been studied at PSI for several years. One possible ~3 U j £ 300 —— application for micro structured GC are electrodes for micro fuel cells. These require structures with a depth 8 200 1 8 1 • evaporated of ~ 200 urn and a width of ~ 50 um. § 100 _ • sputtered One possible and precise structuring method is micro sawing of the channels with a wafer saw, but only 10/150 20/300 straight lines can be obtained. Laser ablation of the Cr/AI film thickness / nm GC is also possible, but it is difficult to achieve a flat channel bottom. Additionally, both previously de• Fig. 1 : Fluence ranges for partial ablation. scribed methods are sequential and consequently No ablation below, complete ablation above, the slow. Therefore we have developed a process that is range indicated by the bar. based on reactive ion etching of GC using oxygen The data suggest that the start of ablation is depend• plasma and metal masks. As a fast prototyping ent on the film thickness, while the threshold for com• method for different flow fields, laser ablation is used plete removal is influenced by the deposition tech• for structuring the metal masks. The preferred mask nique. The ablation threshold for bulk aluminium (650 material is aluminium due to its very low degradation mJ cm"2) is higher than the threshold for the thin films. in the oxygen plasma. This suggests that the ablation is due to laser induced mechanical stress. 2 EXPERIMENTAL CD Glassy carbon is cleaned in an ultrasonic bath with The ablation thresholds are nearly independent from 4 CONCLUSION the number of pulses, and smoothing of the metal edges after repetitive pulsing is observed. The thresh• The presented results show that laser ablation of thin olds for partial and complete lateral removal of the AI films on GC at 193 nm occurs below the threshold metal film were evaluated after 5 pulses (Figure 1), of the bulk material. This suggests, that mechanical because the pulse-to-pulse intensity variation of the stress contributes significantly to the ablation mecha• laser is >10%. One interesting point is the fact, that nism. the film is always completely removed from the sub• 5 REFERENCES strate, but not necessarily in the whole irradiated area. The sharpest edges are obtained for at least 10 [1] R. Srinivasan, B. Braren Chem. Rev. 89, 1303 pulses at fluences > 400 mJ cm'2. (1989). 108 TIME RESOLVED MEASUREMENTS OF THE LASER ABLATION PROCESS OF A TRIAZENE-POLYMER BY NANOSECOND INTERFEROMETRY M. Hauer, D.J. Funk (Los Alamos National Laboratory, USA), T. Lippert, A. Wokaun A photolabile triazene polymer was irradiated with an excimer lasers emitting at 308 nm. The ablation process was studied by a time resolved surface morphology sensitive method, i.e. nanosecond interfer- ometry. The measurements reveal that the etching of the polymer starts and ends with the laser pulse, suggesting a pronounced photochemical part in the ablation mechanism. 1 INTRODUCTION Laser ablation of polymers is a versatile tool for the creation of 3D microstructures. Most commercially 2 a 10 mJ cm" EE. o available polymers exhibit quite poor laser ablation \ \ • 65 mJ cm"2 =• properties (e.g. carbonisation and low etch rates). A 2 -100 m \ \ m 210 mJ cm -o specially developed triazene polymer with a photola- bile group in the polymer main chain exhibits superior 01 laser ablation properties. The ablation process of this in -200 S polymer was studied by ns- interferometry. á — pulse shape i| deposited energy -300 Nanosecond-interferometry allows the observation of the surface morphology in the nano- to microsecond -400 = time range. The triazene polymer was irradiated with XeCI excimer laser light (308 nm) at fluences below -500 and above the ablation threshold (25 mJ cm'2). A fre• quency doubled Nd:YAG Laser (532 nm) is used to 80 120 2000 create the interference patterns on the polymer sur• time delay / ns face with specific delay times after the pump pulse (Figure 1). Fig 2: Time-dependence of the surface profile. At fluences above the ablation threshold the etching starts and ends with the laser pulse and no swelling is detected. At 210 mJ cm"2 a decrease of the phase shift can be observed. A part of this decrease, which is most apparent from 20 to 200 ns, may be due to a transient change of the optical density of the polymer during laser ablation. Excimer Laser (XeCI, KrF, ArF) 4 CONCLUSION Fig 1 : Setup for ns-interferometry. The data above the threshold reveal that the etching of the polymer starts and ends with the laser pulse. By comparing the interference patterns before and This suggests a pronounced photochemical decom• during, respectively after the irradiation, it is possible position mechanism. Pronounced swelling and a time- to extract the phase shift of the interference fringes. delayed etching is observed in the case of a photo- This phase shift is proportional to the height changes of the polymer surface and allows the measurement of thermal ablation mechanism, which has been ob• the surface profile during and after the laser irradia• served with several other polymers [1,2]. tion. 5 REFERENCES 3 RESULTS AND DISCUSSION In Figure 2 the etch depths are shown for three differ• [1] H. Furutani, H. Fukumura, H. Masuhara, Appl. ent fluences at various delay times. The pulse shape Phys. Lett. 65 (26), 3413 (1994). and deposited energy of the laser pulse is included in 2 Figure 2. The measurement at 10 mJ cm" (below the [2] H. Furutani, H. Fukumura, H. Masuhara, S. Kam- ablation threshold) reveals a slight swelling of the bara, T. Kitaguchi, H. Tsukada, T. Ozawa, J. polymer surface, which starts with the laser pulse and Phys. Chem B 102, 3395 (1998). decreases after about 3 u,s. 109 FAST AND SLOW PARTICLES DURING ABLATION OF A PHOTOLABILE POLYMER T. Lippen, M. Hauer, A. Wokaun, J.T. Dickinson (Washington State University, USA), S.C. Langford (Washington State University, USA) The laser ablation products of a photolabile polymer were studied by time-of-flight mass spectrometry. The main product, i.e. N2, consists of three different components, a slow and a very fast component in the neutral ground state and one additional metastable species. 3 + 1 INTRODUCTION first excited electronic state of N2 (A EU ) has 6.17 eV of internal energy, more than enough to produce a Laser ablation of polymers has been studied exten• sively with various analytical techniques. The ablation mechanisms, i.e., photothermal vs. photo-chemical, are still often controversial. Srinivasan [1] has repeat• edly emphasized the importance of looking at the product distribution in order to establish and/or test ablation mechanisms. In general, most TOF-MS stud• ies have given strong indications for photothermal ablation mechanisms. To test whether a photo• chemical mechanism could be identified with TOF- MS, we chose a polymer considered photolabile, which also has excellent properties as a resist for high resolution microlithography. 2 RESULTS AND DISCUSSION When the quadrupole mass spectrometer is tuned to detect particles with a charge to mass ratio of 28 amu/e, the resulting signal shows highly energetic 0 100 200 300 400 500 components (short TOF range in Figure 1), very slow components consistent with emission long after the Fig. 1 : TOF curves with corresponding fits for the 28 laser pulse, and a sharply peaked component of in• amu fragment. Irradiation with 260 mJ cm"2 a) at 308 termediate energies. The fast and slow components nm b) at 248 nm. have been described in previous work at 248 nm [2]. The peak at intermediate energies was only observed secondary electron at the front cone of the quadrupole when the quadrupole was aligned perfectly along the particle detector. line of sight from the sample. This was most probably not the case in our previous experiments. A possible 3 CONCLUSION explanation for this peak could be a metastable spe• cies, because metastable particles are not focused by The detection of an ablation product in an excited the electric fields of the quadrupole. The narrow peak state proves the involvement of electronic excitation 50-100 |is after the laser pulse was most remarkable during laser ablation, strongly suggesting the involve• in that it was only weakly affected by the mass filter ment of photochemical pathways in the ablation setting and was surprisingly resistant to modification mechanism. by modest electric fields and appeared even with a grounded ionizer. Since ground state neutrals are not 4 REFERENCES capable of producing a signal in the quadrupole detec• tor, these particles must be in an excited, metastable [1] R. Srinivasan, Appl. Phys. A 56, 417 (1993). state. [2] T. Lippert, S.C. Langford, A. Wokaun, A most likely candidate for the metastable peaks is S. Geogiou, J.T. Dickinson, J. Appl. Phys. 86, molecular nitrogen. In its lowest vibrational level, the 7116 (1999). 110 111 Atmospheric Chemistry 112 THE LABORATORY OF ATMOSPHERIC CHEMISTRY (LAC) Urs Baltensperger After its foundation in January 2000, the Laboratory of Continuous progress is also made in the linking of the Atmospheric Chemistry (LAC) defined its mission as Laboratory's isotope ratio mass spectrometry compe• follows (see Figure 1 and http://lac.web.psi.ch): tence with the other groups, and it is anticipated that the next annual report will reflect this progress. • Investigation of key processes determining the gas phase and aerosol composition in the Our effort of efficient communication resulted in 23 polluted atmospheric boundary layer, and the peer-reviewed papers and book chapters, with the identification of their sources and sinks isotope ratio mass spectrometry having the best ratio of papers per scientist (congratulations!). It is our goal • Study of the impact of anthropogenic air pollu• to continue with this effort and to even surpass this tion on the Alpine region, including the bio• number in the next year. sphere Among the highlights that are to be found on the fol• lowing pages, a few shall be mentioned also here. With ferragosto (the time when most of Italy is on va• cation), Italy performs a huge 'experiment' each year, where the reduction of emissions (seen in a reduction in N02) results in a significant reduction of the ozone maximum concentration, which could be used for vali• dation of reduction scenarios in photochemical models (see Weber and Prévôt). The new instrument for the determination of the hygroscopicity of aerosol parti• cles at low temperatures demonstrates its ability to follow also relatively rapid changes in air masses, e.g. during a Saharan dust event. This hygroscopicity strongly influences the aerosol impact on climate both directly and indirectly (Weingartner et al.). In the con• Fig. 1 : The various elements of the LAC mission. text of global change studies the use of the stable carbon isotope revealed that the carbon transfer from The year 2001 was a very successful year for the tree crowns into the soil was much faster than so far LAC, since it made major progress towards reaching assumed. Furthermore, the analysis of the oxygen its ambitious goal. Several projects were already isotopes in plant material indicates a distinct reduction started which benefit from the synergy between more in the transpiration of trees exposed to elevated C02. than one of the three individual groups, thus justifying Both findings are new and essential for the under• the new structure. standing of potential physiological changes in trees due to elevated atmospheric C02 (see Steinmann et Among these activities the new mobile atmospheric al.; Sigrist et al.). pollutant laboratory (MOSQUITA) of the LAC is worth mentioning, which is equipped with a suite of state of An outstanding characteristic of the year 2001 was the the art gas phase and aerosol instruments and allows extensive communication with the public, many of for a fast assessment of regional distribution of at• them triggered by the mobile laboratory MOSQUITA. mospheric pollution. The following individual reports In May, our Laboratory participated with the MOS• contain several contributions obtained with this new QUITA at the 'Zürcher Festival des Wissens' at the facility. Zurich main train station, and at the 'Energietag' at the Paul Scherrer Institute, where all participants were A second project relying heavily on the collaboration rewarded with a high number of interested visitors. In of more than one group is the new smog chamber, addition, the Laboratory had an extended article in the where the formation of new particles from gaseous Neue Zürcher Zeitung in January as well as two con• precursors is investigated. Obviously, a combination tributions to the Swiss Television broadcast 'Men• of gas phase and aerosol competence is highly bene• schen-Technik-Wissenschaft' (MTW). ficial also in this context. However, the successful start of this project would not have been possible The major goal for the coming year is the extension of without the excellent support by a number of people the smog chamber facility to its full capacity and to representing specific PSI competence far beyond the establish it as a user facility. Furthermore, the year own laboratory, and I would like to thank all these 2002 will see a number of different field campaigns, persons for their highly valuable contribution. This which will require a good planning of the available facility has already attracted other researchers for instrumentation and manpower. On the whole, we can collaboration, and it is anticipated to grow into a small expect a year full of exciting events, and look forward but successful user facility in the near future. to evenly exciting results. 113 LOCAL ANALYSIS OF PHOTOCHEMISTRY IN THE PO BASIN AROUND MILANO J. Dommen, A.S.H. Prévôt, B. Neininger (MetAir), M. Baumle (MetAir) High mixing ratios of the precursors of photochemical smog as well as of ozone and other photooxidants were measured with a motorglider south and north of Milano. A steady state analysis revealed a VOC- sensitive ozone production in the strongly polluted metropolitan area of Milano. 1 INTRODUCTION The width of the regional plume is about 50 km. The ozone level in the regional plume exceeded that in The Po-basin in northern Italy is a densely populated adjacent areas by 32 ppb. HCHO was also highest in and strongly industrialized region. However, it is also the photochemical plume and reached 5.5 ppb. HCHO one of the high-emission-rate regions in Europe and is emitted by vehicles and is produced by photo• belongs to those areas, which are most affected by chemical degradation of volatile organic compounds. high ozone mixing ratios. Before costly measures are Nitrogen oxides and hydrocarbons (not presented in taken to control elevated ozone concentrations, the Figure 1) also show maximum mixing ratios in the dependence of ozone production on the ambient lev• plume. els of ozone precursors, nitrogen oxides (NO*) and volatile organic compounds (VOC) must be thoroughly From Kleinman's [1] steady state model a parameter understood. In recent years, an observation based can be calculated, which determines whether the local analysis of the current state of an air mass including ozone production is rather VOC- or NOx-sensitive. The analysis of the flight measurements is shown in 03 production rate and the sensitivity of that rate to Figure 2 [2]. Air masses in the most polluted area NOx and VOC was developed [1]. This so-called steady state model makes use of a comprehensive around and north of Milano are VOC-sensitive (A). set of measured species concentrations as input val• That means that a reduction of hydrocarbon emis• ues to calculate local chemical production rates and sions would decrease most efficiently the ozone con• photochemical sensitivities. centrations in this area. 120 2 EXPERIMENTAL A field experiment, Pianura Padana Produzione di Ozono (PIPAPO) was conducted in the summer of 1998 south and north of Milano. Measurements were made on ground based and airborne platforms. On the motorglider of the MetAir company we were able to measure ozone (03), NO, N02, formaldehyde (HCHO), hydrogen peroxide (H202), and hydro• carbons from C4 to C10. 3 RESULTS 660 700 740 780 820 On May 13, 1998, thermally induced southerly winds Fig. 2: Symbols denote measured air masses, which developed transporting the urban pollutants plume are VOC-sensitive (A) or NOx-sensitive (o). over the high-emission region north of Milan towards the Alps. Extremely high peak ozone values were reached with 195 ppb. Figure 1 shows a west to east 4 ACKNOWLEDGEMENT flight section across the pollutants plume around 30 This work was funded by the Commission for Tech• km north of Milano. Ozone values reached 167 ppb. nology and Innovation, contract numbers 3562.1, 4138.1 and 3635.1. 5 REFERENCES [1] L.I. Kleinman, P.H. Daum, J.H. Lee, Y.-N. Lee, L.J. Nunnermacker, S.R. Springston, L. Newman, Dependence of Ozone Production on NO and Hydrocarbons in the troposphere, Geophys. Res. Lett. 24, 2299 (1997). 690 710 730 750 770 [2] J. Dommen, A.S.H. Prévôt, B. Neininger, M. position East (Swiss km-grid) Baumle, Characterization of the Photooxidant Fig. 1 : Mixing ratio of ozone (solid line) and HCHO Formation in the Metropolitan Area of Milan From (dashed line) measured during the west to east flight Aircraft Measurements, J. Geophys. Res., in traverse 30 km north of Milano on May 13 at 3.45 p.m. press (2002). 114 EVALUATING PHOTOCHEMICAL MODEL RESULTS IN THE LOMBARDY REGION N. Ritter, J. Dommen, A.S.H. Prévôt A measuring campaign was carried out in the Lombardy region in Italy in the early summer 1998 within the LOOP project (Limitation of Oxidant Production), a subproject of EUROTRAC-2. Various gases, e.g. NO, N02, NOx, NOy, HCHO, H202, HN03) and meteorological parameters (e.g. wind speed and direction, tem• perature, solar radiation) were measured at ground based monitoring stations and on an airborne plat• form. The dataset offers an exceptional possibility to evaluate model results. Model simulations with the three-dimensional photochemical Urban Airshed Model with variable grid (UAM-V) were performed in the area of investigation. The simulation period is May 12-13, 1998, with one additional start-up day to limit the influence of the initial concentrations. The largest errors in model results are usually due to an unsatis• factory input of the meteorology and emissions. After a thorough validation and correction of those inputs, good agreement between model and measurements was obtained for photooxidants and precursors. 1 INTRODUCTION the domain is biased to around 20 ppb lower values due to the boundary concentrations which differ by the The Lombardy region is one of the most densely same magnitude. From Figure 1b it can be seen, that populated and strongly industrialized areas in Europe. the temporal and spatial variation of N02 is in good High emissions concurrent with high radiation and agreement with the airborne measurements. After temperature lead to frequent elevated ozone concen• 16 h and around 1730 h, the aircraft flew vertical trations. The LOOP project aims at understanding the profiles. temporal and spatial dynamics of such highly effective photooxidant production events in this area. The highest uncertainties in the model simulation could be minimized which resulted in a good spatial 2 UNCERTAINTIES IN MODEL SIMULATIONS and temporal agreement with measurements at ground and upper levels. The highest uncertainties in photochemical simula• tions result usually from meteorological and emission input. Thus, realistic input files are needed: The three-dimensional meteorological model SAI MM was used for the input preparation. Hourly surface data are taken from the monitoring network ANETZ operated by MeteoSwiss and from the various ground stations operated during the measuring campaign. Information about upper air levels is available every 6 hours from balloon soundings at Linate airport and hourly from a windprofiler. SAIMM reproduces realistic wind fields with 2-3 m/s during day, but the height of the mixing layer had to be restricted to the fourth model layer, which corresponds to about 1200 m a.s.l. as measured by aircraft on May 13, 1998. Ratios of mixing ratios measured in the morning at different stations were used to evaluate the emission inventory. These stations are representative concern• ing the dominant emission mix at these sites. The comparison led to a correction of the emission inven• tory in urban and rural areas. 3 RESULTS In this work, a comparison of the model results with airborne measurements of 03 and N02 during the afternoon flight on May 13 is given in Figure 1. The highest measured 03 mixing ratios at ground (not 14 15 16 17 18 19 shown here) reached more than 190 ppb. The aircraft time (CET) (dotted lines) caught a polluted plume south of its centre before 15h CET (Central European Time) Fig. 1 : Modelled ozone (a) and N02 (b) mixing ratios measuring around 160 ppb 03. The model (solid line) (solid lines) are compared to airborne measurements reaches 180 ppb 03. The simulated 03 mixing ratio in (dotted lines) during the afternoon of May 13, 1998. 115 LESS OZONE IN TICINO DURING FERRAGOSTO R.O. Weber, A.S.H. Prévôt In southern Switzerland, considerably less ozone can be found in August compared to other months at similar meteorological conditions. Lower emissions during the Italian vacation ferragosto yield lower con• centrations of nitrogen dioxides and less ozone production. This 'natural' variation in emissions and result• ing photo-oxidant production could be used for validation of photochemical model reduction scenarios. 1 DATA At similar meteorological conditions, differences in Air pollutants are monitored at the station Mendrisio ozone can be interpreted as effect of lower emissions by the Office for Air Pollution Control of the Canton of precursors like nitrogen oxides and volatile hydro• Ticino. The station is located outside the town and has carbons resulting in less ozone production. During the no strong emission sources in its immediate vicinity. It Italian summer vacation ferragosto, the people in the is situated at 350 m a.s.l. in the hilly terrain at the Po Basin and in Canton Ticino spend their time at the northern edge of the Po Basin south of the Alps. The coast, and the industrial activity and traffic in the inner location is open to the south and its pollution concen• part of the country are reduced. The reduction of trations can be strongly influenced by air from the these precursor emissions can be seen in the signifi• heavily industrialized area around Milano. Data from cantly lower nitrogen dioxide concentrations during the period 1991 to 1999 are available. For each day afternoon at Mendrisio (Figure 1). the maximum ozone concentration is determined as the largest one-hour mean ozone value between 12 and 24 Central European time. 3 DISCUSSION 2 RESULTS The decrease of ozone in August is only significant for As air temperature is one of the most important mete• the high maximum ozone concentrations and not for orological factors determining the amount of ambient daily mean values. This can also be seen in the 1999 ozone concentration, we selected days with similar report of the Ticino authorities [1]. This remarkable meteorological conditions by defining two temperature decrease in precursors and ozone in August is actu• classes. For the first class, the mean afternoon tem• ally a very interesting 'experiment' that could be used perature has to be in the range 20 to 25 °C, for the for model validation. In 1994, a large and expensive second class it has to be between 25 and 30 °C. This effort was undertaken at Heilbronn to study the effect selects only days from May to September. For each of reduced emissions on ozone production [2]. In that month the box-plots of the daily maximum ozone con• study, only minor influence on ozone could be de• centration is shown in Figure 1 for both temperature tected because emissions were not reduced enough classes. A standard ANOVA test shows that the mean and in a too small area. In the Po basin, such a 'natu• of the August ozone maxima is significantly lower than ral' experiment takes place every year on large scale the mean ozone maxima of the other months. with significant impacts on air quality. 4 ACKNOWLEDGEMENT This work was supported by BUWAL, Canton Ticino, and Canton Graubünden. Data was also provided by 40- 1 1 1 1 MAY JUN JUL AUG SEP MeteoSwiss. 140- Ö 100- 5 REFERENCES O „ ï Ï [1] Ufficio Protezione dell'Aria del Cantone Ticino, 60- MAY JUN JUL AUG SEP MAY JUN JUL AUG SEP Analisi Delia Qualité Dell' Aria (1999), Bellinzona (2000). Fig. 1 : Box plot of the daily maximum ozone concen• trations (left) and afternoon nitrogen dioxide concen• [2] N. Moussiopoulos et al., High-resolution Simula• trations (right) at Mendrisio: a) for afternoon tempera• tions of the Wind Flow and the Ozone Formation tures from 20 to 25 °C and b) for afternoon tempera• During the Heilbronn Ozone Experiment, Atmos. tures from 25 to 30 °C. The 10th, 25th, 50th, 75th and Environ. 31, 3175 (1997). 90th percentiles are shown. 116 A NEW METHOD TO DEFINE NOx AND VOC SENSITIVITY OF 03 FORMATION S. Andreani-Aksoyoglu, J. Keller, A.S.H. Prévôt A new approach for defining NOx and VOC sensitivity for ozone production is proposed. Air quality during a smog episode was simulated using a 3-dimensional photochemical model and the results were evalu• ated on the basis of various definitions ofNOx and VOC sensitivity of 03 production. 1 INTRODUCTION sion inventory, yielding up to 70 ppb ozone, and with reduced emissions of NOx and VOC (50%). It is important for the ozone control strategies to know whether 03 formation is sensitive to NOx or VOC 3 RESULTS AND DISCUSSION emissions to avoid unfavorable effects due to non- linearity of the photochemistry. Indicator species (e.g. The effects of emission reductions on ozone are H202/HN03) can be useful to investigate the sensitivi• shown in Figure 1 for each model grid point at the ties [1]. surface. Various definitions of the distinction between NOx and VOC sensitivity are shown in Figure 1a-c. Sillman's definition (Figurel a) [1] indicates whether NOx or VOC control is more effective. The definition of Lu and Chang (Figurel b) [2] attributes locations to the NOx sensitive regime, if NOx emission reductions yield a lower and VOC emission reductions a higher ozone concentration and vice versa. Many locations where the NOx sensitivity is much higher than the VOC sensitivity are attributed to the transition range. Therefore, we proposed a modified approach using boundaries with varying slopes delineating NOx and VOC sensitivity. In this study, a boundary slope of 10 -20 -10 0 10 20 30 03 reduction [VOC control], in ppb was chosen (Figure 1c) [3]. The variation of thresh• olds with the definition of sensitivity is shown in Figure 2 for two indicators. It was concluded that the thresh• old values of indicators depend on the definition of NOx and VOC sensitivity of 03 production and the new method proposed here can well distinguish the loca• tions with different regimes. -20 -10 0 10 20 30 03 reduction [VOC control], in ppb 0 5 10 15 20 25 •- : NOy (ppb) H202/HN03 ¡ NOx-, VOC- sensitive J i Fig. 2: Variation of indicator values with definition V//////////A VOC-sensitive K\\\\SW1 NOx-sensitive. ! " : . • ¿¡/ 4 REFERENCES [1] S. Sillman, The use of NOy, H2Os and HN03 as • ' Indicators for Ozone-NOx Hydrocarbon Sensitivity -20 -10 0 10 20 30 in Urban Locations, J. Geophys. Res. 100, 03 reduction [VOC control], in ppb 14175-14188, (1995). Fig. 1: Distribution of grid cells among various sensi• [2] C.-H. Lu and J. Chang, On the Indicator-Based tivity ranges using the definition of (a) Sillman [1], (b) Approach to Assess Ozone Sensitivities and Lu and Chang [2], (c) Andreani et al. [3]. Emission Features, J. Geophys. Res. 103, 3453-3462, (1998). 2 MODELLING [3] S. Andreani-Aksoyoglu et al., Variability of Indica• The 3-dimensional Urban Airshed Model was used to tor Values for Ozone Production Sensitivity: A simulate the air quality in Switzerland during July 27- Model Study in Switzerland and San Joaquin Val• 30, 1993. Model simulations with 5 km x 5 km horizon• ley (California), Atmos. Environ. 35, 5593-5603, tal resolution were conducted with the regular emis• (2001). 117 CHAPOP (CHARACTERIZATION OF HIGH ALPINE POLLUTION PLUMES) S. Henne, M. Steinbacher, S. Nyeki, J. Dommen, M. Furger, A.S.H. Prévôt To enhance the knowledge of photochemical processes and vertical transport of air pollutants in the high alpine atmosphere the Laboratory of Atmospheric Chemistry participated in a field campaign in the Gott• hard region during August and September 2001. Three airplanes, the PSI mobile van and several ground stations were used to collect dense information about meteorology and air pollution within and above a deep alpine valley. We describe here the main concept and the field campaign of the CHAPOP project. 1 INTRODUCTION ley atmosphere were made at a balloon sounding station (open circle). Continuous measurements of Due to thermally induced wind systems during the standard chemical and meteorological parameters summer months Alpine valleys contribute effectively to were conducted during one month at three sites vertical mixing between the atmospheric boundary (squares), including formaldehyde and detailed VOC layer and the lower free troposphere (LFT). In former analysis in Dalpe [2]. The station Matro, on top of the studies it was shown that up to five times the valley crest at 2.2 km asl, measured within the injection layer volume is exported to the LFT during one upwind and the LFT. Wind profiles up to 1 km agi were also phase in the Mesolcina valley, southern Switzerland acquired at this site. Meteorological data was gath• [1]. Emissions from the valley floor are carried up• ered at two additional sites (diamonds) at the valley's wards in thermal plumes and start to accumulate in south-orientated slope. Temperature sensors (trian• the so-called injection layer Figure 1. Due to dilution of gles) were distributed in a vertical profile up to 2.5 km the air pollutants the ozone production efficiency asl to get further information about the slope winds. (molecules ozone produced per molecule NOx con• sumed) might increase while the air mass is lifted from the valley floor to the mountain tops. The main goals of the CHAPOP project are to quantify the vertical transport of air pollutants in the transalpine traffic re• gions and to understand the chemical processes in the transported air mass. 125 «"•-»» ^ ! ! ! 680 685 690 695 700 705 710 715 720 725 East [km] Fig. 2: Measurement sites in the Leventina valley. Fig. 1 : Slope winds and injection layer, schematic 3 DATA ANALYSIS view. The recorded data set will be analysed with respect to 2 FIELD CAMPAIGN the air mass balance in the valley, quantification of The activities in the Leventina valley south of the Gott• vertical transport along the valley slopes and chemical hard region during five weeks in the summer of 2001 processes in the affected atmospheric layers. are summarized in Figure 2. On three flight days Met- Air's DIMONA, a motor glider, acquired meteorologi• 4 ACKNOWLEDGEMENT cal, chemical and aerosol parameters by flying cross Financial support by the EU CAATER project is grate• sections within the valley (dotted lines). The MERLIN fully acknowledged. (Meteo France) flew within the injection layer, 3 - 4 km asl, measuring similar parameters as the 5 REFERENCES DIMONA. The FALCON (DLR) carried a nadir-pointing aerosol LIDAR at a height of 8 km asl that supplied [1] M. Furger et al., The VOTALP Mesolcina Valley important information about boundary layer develop• Campaign 1996 - Concept, Background and ment and aerosol distribution. Both MERLIN and FAL• Some Highlights. Atmos. Environ. 34, 1395 CON flew patterns similar to that in Figure 2 (solid (2000). line). The PSI mobile laboratory MOSQUITA meas• [2] M. Steinbacher et al., First Measurements with a ured gases and aerosols along the valley floor and at Proton-Transfer Reaction Mass Spectrometer the slopes (thin solid line). Vertical profiles of the val• (PTR-MS). this Issue. 118 FIRST MEASUREMENTS WITH A PROTON-TRANSFER-REACTION MASS SPECTROMETER (PTR-MS) M. Steinbacher, J. Dommen, A.S.H. Prévôt, C. Ammann (FAL, Bern-Liebefeld), A. Neftel (FAL) A new instrument for the measurement of volatile organic compounds has been implemented. This proton- transfer-reaction mass spectrometer (PTR-MS) allows the determination of a large variety of VOCs (Vola• tile Organic Compounds) at a high time resolution in combination with a low detection limit. The data set gained with the PTR-MS could contribute to a progress in the detailed understanding of the formation of the photooxidation products and the formation of secondary aerosols in the atmosphere. 1 EXPERIMENTAL methacrolein, and toluene, respectively for August 29. The measurement site was in Dalpe at 1200 m asi The proton-transfer-reaction mass spectrometer and about 300 m above the valley floor. Each individ• (PTR-MS) used here was developed at the University ual mass was measured for 10 seconds every 3 min• of Innsbruck and is now commercially available by utes, allowing the detection of short term variations. lonicon Analytik GmbH, Innsbruck. Figure 1 shows an Isoprene is of biogenic origin, toluene is an indicator outline of the instrument. The measuring method is for traffic emissions, and methyl vinyl ketone (MVK) + based on a proton-transfer reaction of H30 to com• and methacrolein (MACR) are photooxidation prod• pounds with higher proton affinity which are then ucts of the isoprene degradation in the atmosphere. measured by mass spectrometry. Higher proton affini• ties are found for the common volatile organic com• m69 (isoprene) pounds, including alkenes, aldehydes, ketones, acids, m71 (methyl vinyl ketone + and aromatics. methacrolein) ?*. m93 (toluene) a10 o "g 0.8 • • • •:•* í Ol I 06 E gas Utlvt H20 *- vapor [air to be analyzed] inlet 1 high vacuum 29.08.01 12:00 1 pump time Fig. 2: First results of PTR-MS measurements during ton setüfce tinft tafee loît detection system CHAPOP campaign. Fig. 1 : Schematic of the PTR-MS (HC: hollow cath• The low toluene mixing ratios indicate that the sam• ode, SD: source drift region) [1]. pling site is not strongly influenced by aromatic com• The proton transfer reaction is a soft ionization tech• pounds from road traffic emissions. The diurnal varia• nique which causes less fragmentation than other tion of isoprene reflects the occurrence of biogenic ionization techniques. Consequently, no complex emissions during the day. Strong solar radiation break-down patterns originate which could lead to caused an effective photochemical decomposition of difficulties with the quantification of the compounds. isoprene leading to mixing ratios of the degradation However, the measuring method allows no unambigu• products MVK and MACR even higher than their pre• ous identification of species with isobaric masses. cursor. 2 RESULTS 3 ACKNOWLEDGEMENT After several tests in the lab a first field campaign took This work was supported by the Swiss National Sci• place in the city of Berne in March 2001. Tests con• ence Foundation. cerning the efficiency of the PTR-MS were carried out by comparison of hydrocarbon measurements with a 4 REFERENCES gas Chromatograph. In August and September 2001 a [1] W. Lindinger et al., On-line Monitoring of Volatile second field campaign took place in Ticino within the Organic Compounds at pptv Levels by Means of scope of the CHAPOP (Characterization of High Al• Proton-Transfer-Reaction Mass Spectrometry pine Pollution Plumes) project. Among other instru• (PTR-MS). Medical Applications, Food Control ments the PTR-MS was operated to study the effects and Environmental Research, Int. J. Mass Spec- of the traffic emissions in the Gotthard valley [2]. trom. Ion Processes 173, 191 (1998). Figure 2 shows the mixing ratios of masses 69, 71, [2] S. Henne, et al., CHAPOP (Characterization of and 93, attributed to isoprene, methyl vinyl ketone + High Alpine Pollution Plumes), this issue. 119 THE YEAR OF GASPHASE AND AEROSOL MEASUREMENTS (YOGAM) - PRELIMINARY AEROSOL RESULTS N. Bukowiecki, I. Polo, A.S.H. Prévôt, J. Dommen, R. Richter, E. Weingartner, U. Baltensperger On occasion of the project YOGAM (Year of Gasphase and Aerosol Measurements) a mobile atmospheric pollutant laboratory was designed. In spring 2001 regular on-road measurements started in the Zürich area with full measuring equipment and will be continued until spring/summer 2002. Preliminary aerosol data analysis shows that the occurrence of nanoparticles (diameter D < 50 nm) in the ground-near atmos• phere is highly dynamic and shows a strong dependence on meteorological conditions. 1 INTRODUCTION [2]). The formation of both types of particles has been shown to be extremely dependent on factors such as In the last decades large efforts have been made to ambient temperature or global radiation. The ultrafine investigate the role of airborne particles in the diame• particles measured during the Zurich downtown morn• ter range D = 0.01 - 10 um in atmospheric key proc• ing rush hour and the suburban evening rush with esses, triggered by studies showing that aerosol parti• diameters around 30 nm can be considered as mainly cles from anthropogenic emissions have adverse primary ultrafine particles, while secondary ultrafine health effects [1]. However, there are still many unan• particles, which often are characterized by diameters swered questions when it comes to the understanding around 10 nm, are probably responsible for the large of interactions between aerosol parameters, levels of amount of ultrafine particles at 13:00. The investiga• gaseous species and meteorological conditions. For tion of the different formation patterns of these two many regions, experimental data for detailed analysis types of ultrafine particles is an urgent issue in current of the above processes are still scarce. research, and it is anticipated that the complete YOGAM data will contribute to the solution of open questions in this field. 2 EXPERIMENTAL Within YOGAM a mobile laboratory was constructed Zürich Zürich Suburban Rural Suburban Rural Suburban Downtown Downtown at Paul Scherrer Institute, allowing for on-road meas• urements of six different aerosol parameters (size distributions D = 7 - 330 nm and D = 0.3 - 20 urn, total number concentration, as well as the concentra• tions of black carbon, active surface area and PM2.5) and nine gas phase parameters (03, C02, CO, NOy, NOx, HN03, PAN, H202 and HCHO), along with geo• graphical information (GPS) and meteorological data. Since measurements can be performed while driving, 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 highly time and space resolved information on the Time (July 26, 2001) ground pollutant level in the testing area is obtained. I dN/d(logDp)(cm"3) : M 30000 M 20000 —15000 5000 | During YOGAM, a selected route in the Zürich area, including Zürich downtown, suburban areas as well as remote sites is driven on a highly regular base Fig. 1 : On-road particle number size distributions throughout the course of a year. For the time frame measured with the PSI mobile laboratory on July 26, chosen, additional data from official monitoring sta• 2001. tions are available for comparison. 4 ACKNOWLEDGEMENTS 3 RESULTS We thank the canton of Zürich, the BUWAL and the Figure 1 shows a 3D-contour plot of the SMPS (Scan• Zürich city authorities for their support and funding. ning Mobility Particle Sizer) particle number size dis• tributions measured during a summer day (July 26, 5 REFERENCES 2001). Accumulation mode particles with a diameter [1] D.W. Dockery et al., An Association Between Air around 100 nm are observed throughout the whole Pollution and Mortality in Six U.S. Cities, Massa• day with different concentrations, regardless their chusetts Medical Society Journal of Medicine sampling location. Focussing on particles < 50 nm, 329, 1753 (1993). the situation becomes more complicated and involves the distinction of primary ultrafine particles (condensa• [2] U. Baltensperger et al., Urban and Rural Aerosol tion of hot traffic exhaust gas without atmospheric Characterization of Summer Smog Events During reactions) and secondary ultrafine particles (conden• the PIPAPO Field Campaign in Milan, Italy, Geo• sation of products from atmospheric reactions, see phys. Res., in press (2002). 120 MOBILE MEASUREMENTS OF AIR POLLUTANTS IN THE ZURICH REGION: FIRST RESULTS G. Widmer, N. Bukowiecki, A.S.H. Prévôt, J. Dommen, E. Weingartner, U. Baltensperger During one year, periodical measurements of a large number of atmospheric trace gases are performed with the PSI Atmospheric pollutant laboratory to get a more detailed insight into the seasonal variation of concentrations of harmful substances and tropospheric ozone production in the Zurich region. An example of the variability of carbon monoxide and ozone during one measurement day is shown. 1 MEASUREMENTS lower in the urban region around Zurich and in vehicu• lar plumes, due to titration of ozone by nitrogen oxide. Within the YOGAM project (Year Of Gas and Aerosol Measurements), various species (nitrogen oxides, ozone, carbon monoxide, peroxides, formaldehyde, 2000n and aerosol parameters) have been measured with the goal to improve the understanding of tropospheric Q. v. ozone production in different seasons. The route of Q. data collection leads through urban and rural areas 1000 within the Zurich region (Figure 1). The van starts in O the morning at PSI and does the route twice counter• O clockwise with a noon break in Zurich. This new kind of measurements allows observation of spatial con• v~i 1 1 1 1 1 1 1 1 1 1 centration gradients of a large number of species over a whole season. 8 10 12 14 16 18 local time Fig. 2: Measurements of carbon monoxide along the route (symbols, every 20th data point is shown) with 5% percentile values (line). Symbol notation according to Figure 1. 80 Ee-fitel Q. CL WIND VELOCITY CROSS SPECTRA MEASURED IN THE RHINE VALLEY M. Furger, R.O.Weber, S. Gubser (ETH Zürich) Scintillometers measure the wind component perpendicular to the light path between transmitter and re• ceiver. Our instruments measure the horizontal and vertical wind components simultaneously. Cross spec• tra of horizontal and vertical wind measurements should reveal information about the occurrence of at• mospheric waves. However, our crosswind measurements do not unequivocally reveal wave signatures. 1 INTRODUCTION The spectra represent a continuous, gradual change from steady mountain waves to unsteady short-period Horizontal and vertical crosswind measurements with lee waves and even non-deterministic turbulence for scintillometers have been obtained in the Rhine Valley higher frequencies within the foehn flow. Instrumental north of Sargans, Switzerland, during strong foehn noise is present for frequencies greater than 1/min. flows. The measurements were part of the Mesoscale Alpine Program (MAP) field campaign in autumn 1999, an international field program to study the ef• fects of mountains on precipitation and airflow dynam• 1 1 ics. The generation of lee waves downstream of Eraellen mountains is a common experience under foehn con• Flijs a ditions, and has been observed with various instru• ments. Here we show measurements of one foehn case and discuss the cross spectra obtained with ! \ PSI's scintillometers. E 2 DATA AND METHODS win Two scintillometers were installed in the area of Seve• ' Mi len, Switzerland. Transmitters and receivers were placed on opposite sides of the valley, and the 6.5-km light beams crossed the valley centre at about 500 m 0.001 0.01 0.1 1 10 above ground level (see [1] for details). Measure• Frequency (1/minute) ments were sampled every 7 s. The time series ana• lysed here spanned an interval from 0741 UTC on 22 Fig. 1 : Amplitude spectra of the horizontal and verti• Oct through 0205 UTC on 23 Oct 1999. cal wind components for 22-23 Oct 1999. The data were divided into equally long segments of 400-, , 1 1 1 2048 data points. The segments overlapped by one- half of their length. The cross-spectra were calculated for each segment by applying a Welch filter and using a fast Fourier transform. Then the spectra of all seg• ments were averaged. For each calculation, the hori• zontal (u) component was the leading variable. 3 RESULTS Cross-spectra between horizontal and vertical wind components are shown in Figures 1 and 2. Strong peaks in the amplitude spectra are absent, although significant wave activity has been observed on that 0.001 0.01 0.1 1 10 day with aircraft and ground-based microbarographs. Frequency (1/minute) The spectra exhibit a slope of approximately -5/3. This power law behaviour can neither be explained Fig. 2: Phase spectra of the horizontal and vertical with a stationary mountain wave (with constant verti• wind components for 22-23 Oct 1999. cal velocity w) nor with propagating lee waves (oscil• lating w). The phase spectra in Figure 2 show a differ• 4 REFERENCES ent behaviour of the two scintillometers. The Ergellen vertical wind component lags behind the horizontal [1] M. Furger, S. Gubser, F. von Arx, Vertikal-winde component by 180° for periods of 10 to 100 minutes. und Schwerewellen in einem Föhntal - Fallstu• The Flusa components for these periods are in phase dien mit Szintillometern und Mikrobarographen with each other. For stationary wave events, a linear während MAP-FORM, DACH-Meteorologen- phase relationship is expected. Tagung 2001, Vienna, Austria, CD-ROM (2001). 122 PRELIMINARY COMPARISON OF THE SATELLITE-BASED AEROSOL PRODUCT OF MISR AND SUNPHOTOMETER DATA FOR WESTERN SWITZERLAND J. Keller, C. Bore! (Los Alamos National Laboratory, USA) The Multi-Angle Imaging Spectro-Radiometer (MISR) onboard the NASA satellite Terra observes the earth with 9 cameras at different view angles and at 4 spectral bands. Geo-rectified radiances at 275 m and 1100 m resolution are available. On a 17.6 km scale, an aerosol operational product is delivered, which includes gridded aerosol optical depths and aerosol mixtures typical for maritime and continental environ• ments. In a preliminary study we analyzed data taken on September 11, 2000 and compared the aerosol optical depth (AOD) with sunphotometer measurements at Bern. 1 MISR RADIANCE AND AEROSOL DATA closest to the site of the instrument. Pixel 2 and 3 are significantly lower (0.05), whereas pixel 7 shows the The Multi-Angle Imaging Spectro-Radiometer (MISR) maximum value (0.24) of the domain. Depending on onboard the NASA satellite Terra has 9 cameras with the aerosol model, the Angstrom coefficient a of the 9 different view angles in the forward, nadir and aft- power law approximation AOD(À) = bx " of the spec• ward direction (0, 26.1, 45.6, 60.0 and 70.5 deg) and tral dependence varies roughly between 0.9 and 1.3. 4 spectral bands (blue: 446 nm, green: 557 nm, red: The coefficient of the sunphotometer data, however, is 672 nm and NIR: 866 nm). The spatial resolution of about 1.8, which is similar to those measured at Lo• the radiance product is 275 m or 1100 m. An opera• carno (1.9) and Ispra (1.9). We suppose that the very tional aerosol product is available on regional grids fine particles are not sufficiently taken into account in with a grid resolution of 17.6 km x 17.6 km ([1]). This the retrieval algorithm. product contains gridded aerosol optical depths (AOD) over water and over land together with the best fit aerosol mixture (best fit aerosol model). An aerosol model is defined as a mixture of 3 different aerosols, where the proportions are given in terms of AOD frac• tions. MISR currently supports 63 different mixtures. We analyzed the data for the satellite path 197 cov• Fig. 1 : True color radiance image of the aftward- ering a region including partly Switzerland and France looking camera Da (nominal zenith angle 70.5 deg). on September 11, 2000. Figure 1 shows the true color image of the geo-rectified radiance of the camera Da Best Fit Optical Depth looking aftward at 70.5 deg. The topography of west• ern Switzerland is given in Figure 2. Hazy areas due to increased aerosol loads are predominantly located at lower altitudes, whereas mountainous areas appear clearer. The best fit optical depth of the green band is shown in Figure 2. Over large areas of France, the I AOD varies between 0.05 and 0.12. In the western 0.00 0.05 0.10 0.15 0.20 0.25 part, e.g. in the Swiss Midlands, increased values of optical depth [—] 0.18 to 0.25 are found. For higher altitudes such as Fig. 2: Best fit optical depth of the green MISR band, the Jura and the Alps the MISR algorithm is not al• and contours of the topography. The diamond denotes ways able to compute AODs. The predominant mod• the location of the sunphotometer at Bern. The pixels els in the Swiss area are the models 51 (clean conti• used for comparison are labeled with "1 " to "8"). nental, 95% sulfate/nitrate, 5% soot) and 55 (dusty continental, 75% sulfate/nitrate, 25% mineral dust). 3 ACKNOWLEDGEMENT 2 COMPARISON WITH SUNPHOTOMETER DATA MISR Radiance and AOD data were obtained from the Earth Observing System (EOS) Data Gateway. The closest sun photometer that was operational on September 11, 2000 was the instrument of the Insti• 4 REFERENCES tute for Applied Physics of the University of Bern (Switzerland). At the overpass time, AOD(557 nm) [1] D.J. Diner, A. Abdou Wedad, K. Crean, H.R. values were derived from the sunphotometer and the Gordon, R.A. Kahn, J.V. Martonchik, S. McMul- MISR data. Eight pixels located in the Swiss Midlands droch, S.R. Paradise, B. Pinty, M.M. Verstraete, were taken for comparison. The AOD (557 nm) of the M. Wang, R.A. West, MISR Aerosol Retrieval MISR pixels 1 (0.13), 5 (0.13) and 8 (0.14) match well Algorithm Theoretical Basis, JPL, Pasadena, JPL D-11400, Revision D (1999). with the value of the sunphotometer (0.145). Pixel 1 is 123 SPATIAL MAPPING OF AEROSOLS ON THE BASIS OF AIRBORNE IMAGING SPECTROSCOPY S. Bojinski (RSL, University of Zürich), J.Keller, M. Schaepman (RSL), D. Schläpfer (RSL) Quantification of the change in upwelling radiance at the top of atmosphere due to the presence of tropo- spheric aerosols (aerosol optical effect) by means of airborne imaging spectroscopy is a prerequisite for spatial mapping of aerosol parameters, such as optical depth and size distribution. In turn, the retrieval of Earth surface bio-/geophysical parameters from spectral imagery, e.g. chlorophyll content of vegetation, needs correction of the atmospheric radiance. The problem of separation between radiative contributions of surface and atmosphere in the spectrometer signal based on image pixels, especially over land areas, is being addressed in this work. 1 MODELLING deviation of the aerosol optical effect from an as• The atmospheric transfer code Modtran4 [1] with a sumed standard aerosol model (Figure 2). Change of Mie scattering pre-processor was used to simulate aerosol optical depth with topography is well detected the at-sensor radiance for different boundary layer in the valley centered in the image. Numerical inver• aerosol regimes and surface reflectances. Aerosol sion of this result will later provide the spatial varia• regimes are characterized by prevalent aerosol types tion of aerosol characteristics. that differ in size distribution, usually described by Mask (=0) modes, and particle composition. Figure 1 shows the apparent reflectance change relative to an aerosol- free atmosphere (aerosol optical effect) at 20 km height, for a mixed rural-urban and two rural aerosol types and four levels of optical depth. Soot absorp• tion for the rural-urban aerosol as well as marked backscattering in the visible due to a high fine particle fraction in the two-mode case are discernible. These simulations are used for numerical inversion of the aerosol optical effect by means of look-up tables. -0.03 Li I . . , , I . . , . I . , , . I . , . . 500 lOOO 1500 2000 2500 Wavelength [nm] Fig. 2: Aerosol optical effect variation at 0.67u.m Fig. 1 : Simulated aerosol optical effect for surface wavelength over complex topography. Pixels not albedo p=0.1. The effect increases with larger optical considered for evaluation are masked out. depth x. 4 ACKNOWLEDGEMENT 2 AIRBORNE DATA Support by the Swiss Science Foundation is greatly Airborne imaging spectrometer data in 224 spectral acknowledged. bands at wavelengths between 400 and 2500 nm and 10 nm resolution, and a spatial ground resolution 5 REFERENCES of 20 m are provided by the AVI RIS sensor [2]. We [1] A. Berk, L.S. Bernsten, D.C. Robertson, Modtran use an image scene with strong topography and sur• - A Moderate Resolution Model to Lowtran7, GL- face variation (Californian coast near Santa Monica), TR890122, Hanscom AFB (1989). and expected spatial change of aerosol properties to develop methods for aerosol parameter mapping [2] R.O. Green, M.L Eastwood, CM. Sarture, T.G. over land, a problem that is yet to be solved generally Chrien, Imaging Spectroscopy and the Airborne [3]. Visible/Infrared Imaging Spectrometer (AVIRIS), Rem. Sens. Env. 65, 227 (1998). 3 RESULTS [3] M.D. King, Y.J. Kaufman, D. Tanré, T. Nakajima, After removing the radiative Rayleigh contribution Remote Sensing of Tropospheric Aerosols from and topographic illumination effects, application of Space - Past, Present, and Future, Bull. Am. the band ratio method [3] yields an estimate of the Meteor. Soc. 80, 2229 (1999). 124 THE NEW PSI SMOG CHAMBER FACILITY FOR CONTROLLED ATMOSPHERIC CHEMISTRY EXPERIMENTS U. Baltensperger, D. Baechle, B. Bitnar, J. Dommen, M. Furger, D. Paulsen, A. Prévôt, R. Richter, M. Steinbacher, E. Weingartner, M. Kalberer (ETH Zürich), M. Sax (ETHZ) R. Zenobi (ETHZ) A chamber for the investigation of aerosol formation and aging processes was built at PSI and success• fully tested. Experiments on the formation of secondary organic aerosol and the aging of soot particles are planned. 1 INTRODUCTION Various bag materials were tested (see transmission spectra in Figure 2). The Tediar™ material TST would Among the open questions in atmospheric chemistry have been ideal, since it cuts off most of the UV light is the formation of secondary aerosol particles, as well having wavelengths shorter than 290 nm, which is as aging processes of primary aerosol particles, e.g. similar to the atmosphere at the earth's surface. How• soot particles from tailpipe emissions. The formation ever, due to problems in manufacturing a bag of this of secondary organic aerosol from gaseous precur• size from Tediar™, Teflon™ was chosen, which gives sors is of great current interest for several reasons. the highest transmission throughout the spectrum. First, the estimates for the relative importance of sec• ondary vs. primary (i.e., directly emitted as particles 100- from the sources) particulate organic carbon still vary greatly. Second, the composition of organic aerosol particles on the molecular level is difficult to analyze, even when starting with a single gaseous precursor [1]. A smog chamber (air volume of 27 m3) was built at PSI to address these questions. t (TST20SG4), % 2 EXPERIMENTAL t (FEP), % The chamber is contained in a wooden housing. Four t(TUT10BG3), % xenon arc lamps (4 kW each) are used to simulate the solar light spectrum as closely as possible and to I • I • I 200 300 400 500 600 700 800 900 1000 mimic natural photochemistry. The housing walls were Wavelength, nm covered with aluminum foil to optimize the light inten• sity (matching daylight at the earth's surface) and Fig. 2: Transmission of various bag materials. TST, minimize electrical power requirements. Figure 1 TUT = Tediar™, FEP = Teflon™. gives an impression of the facility. The chamber temperature is controlled by two cooling units (total capacity 19.5 kW), allowing for tempera• ture stabilization of ±1°C within the range of 15 to 22°C. The bag is filled using particulate-filtered air and a pure air generator (250 I min'1), eliminating methane and non-methane hydrocarbons. Reactants are added either directly from appropriate gas bottles (NO, N02, and propylene), by means of an ozone generator, or via evaporation of liquid reactants (e.g., 1,3,5- trimethylbenzene or 1,3,5-TMB). Seed aerosols may be added by nebulization of appropriate solutions. Flows are regulated with mass flow controllers. Ozone and NOx are monitored with commercial gas analyz• ers. The mixing ratio of a reactant (e.g., 1,3,5-TMB) is followed online with a GC-FID connected to the smog chamber. In a later phase, a proton transfer reaction mass spectrometer (PTR-MS) will be available for on• line determination of reactants and products with a time resolution on the order of seconds. Light intensity is monitored with a spectrometer and appropriate fiber Fig. 1 : A picture of the smog chamber taken during optics. Aerosol formation is monitored with a Scanning the installation of the bag inside the wooden housing. Mobility Particle Sizer providing a size distribution of Above the entrance door is one of housings for the particles with diameters between 7 and 220 nm at a xenon arc lamps. time resolution of 3 minutes. The total number con- 125 centration is determined with an additional condensa• performed using gas chromatography coupled to tion particle counter. mass spectrometry as well as quasi-on-line determi• nation of organic acids using a wet effluent dénuder / 3 RESULTS aerosol collector system coupled to ion chromatogra• phy. Volatility and hygroscopicity will be determined Figure 3 shows the evolution of the size distribution by means of tandem differential mobility analyzers. formed during the photooxidation of 1,3,5-TMFJ (650 ppb) in the presence of 1200 ppb NOx and the artificial One of the following air sampling systems is used for light. New particles were formed within 30 minutes identifying and quantifying the gas and aerosol phase after illuminating the bag. A preliminary analysis re• oxidation products of 1,3,5-TMB that occur during an sults in an aerosol yield of 6.2% at the maximum experiment. Either a filter-polyurethane (PUF) system aerosol mass concentration, which compares well with consisting of a Teflon™ coated quartz fiber filter and literature values [2]. two PUFs in line, or a system with two annular denud- ers and a filter at the end of the line will be attached to the bag. Both systems suffer from positive as well as negative sampling artifacts when a separation of 6.0x10° light exposure = 120 min gaseous and particulate fraction is required. Further 4.0x106 -j Total conc.= 7.61 E4 pt/cm" investigations will determine which system is most suitable. 2.0x10s - After sampling the oxidation product, the filter and the E 0.0 PUFs/denuders are extracted with appropriate sol• f. 6.0x10s vent. The obtained samples are derivatized with a. light exposure = 60 min PFBHA (0-(2,3,4,5,6-pentafluorobenzyl)-hydroxyl- ra 4.0x10s - Total conc.= 7.57E4 pt/cm amine) for carbonyl groups to form oximes, and with o 5 5 MTBSTFA (W-ferf-Butyldimethylsilyl-W-methyltrifluoro- •z 2.0x10 acetamide) for carboxyl- and hydroxyl groups to form T3 fe/T-butyldimethylsilyl derivatives. The derivatization 0 0.0 i i—i—i—i i i reaction converts polar compounds into less polar S 6.0x10s c light exposure = 30 min derivatives enabling analysis by GC-MS. tu = Total conc.= 6.19E4 pt/cm3 g 4.0x105 With the successful initiation of the PSI smog cham• o s ber, a new user lab facility for the simulation of at• m 2.0x10 g mospheric chemistry has been established. We are T 1 1 1 l^'l I I j looking forward to many exciting new experiments. Further collaborations are welcome. 1 0.0 Background scan before exposure 5 ACKNOWLEDGMENT The PTR-MS is partially funded by the Swiss National Science Foundation. 6 REFERENCES Particle mobility diameter [nm] [1] U. Baltensperger, The Organic Component of the Atmospheric Aerosol: Facts and Fiction, J. Aero• Fig. 3: Evolution of the particle size distribution of sol Sei. 32, Suppl. 1, S901-S902 (2001). secondary organic aerosol formed by the photo- [2] D.R. Cocker III, BT. Mader, M. Kalberer, R.C. oxidation of 1,3,5-trimethylbenzene in a NOx mixture. Flagan, J.H. Seinfeld, The effect of water on gas- particle partitioning of secondary organic aerosol: 4 OUTLOOK II. m-xylene and 1,3,5-trimethylbenzene photo- In a later phase, detailed physical and chemical char• oxidation systems, Atmos. Environ. 35, 6073- acterization of the secondary organic aerosol will be 6085. 126 A DMA FLOW SYSTEM TO IMPROVE ULTRAFINE AEROSOL SIZE DISTRIBUTION MEASUREMENTS D. Paulsen, E. Weingartner A number of Differential Mobility Analyzers (DMA) have been designed or modified to improve the quality of ultrafine particle (<50 nm) measurements. However, measures can be taken to ensure the best possible results from lesser-optimized models. A flow system was designed to accurately maintain high sheath-air flow rates to improve measurements of ultrafine particle sizes. 1 INTRODUCTION the higher aerosol flow rate of 1.5 L/min (15 L/min sheath flow) than for 0.3 L/min. Obtaining quality particle size characterization using a DMA requires precise measurement and matching of flow rates. A closed-loop sheath flow system similar to the recirculating system of the TSI 3080 classifier platform was designed to provide accurate and auto• matic control of the DMA sheath air up to 20 L/min [1]. The system will be used to study characteristics of newly formed ultrafine particles in the new PSI smog chamber. 2 EXPERIMENTAL The closed-loop flow system (Fig. 1) consists of a sealed regenerative DC blower. This type of blower is capable of higher pressures than most positive dis• placement blowers of comparable size. In addition, the blower gives pulsation free airflow. The blower does work on the air and thus increases the sheath-air temperature requiring the use of a finned-tube heat exchanger to bring the temperature to atmospheric conditions. A low pressure-drop laminar flow element (LFE) measures the actual volumetric flow rate (range of 0-20 L/min). The pressure drop across this element is linear with flow rate, thus a pressure transducer is Fig. 1 : DMA closed-loop flow system used to generate a proportional signal for feedback control. The LFE and pressure transducer were cali• brated together and are accurate to less than 1% of the reading. Aerosol flow 1.5 LPM 1 LPM The TSI model 3080 classifier platform also uses a 0.3 LPM similar blower in their recirculating flow design to maintain the DMA sheath flow. TSI recommends plac• ing the two included blowers in series (the second blower is used for the optional Nano DMA bypass flow) to more easily obtain a sheath flow of 15 L/min. However, if care is taken to use sufficiently large tub• ing diameters and a minimal amount of restrictive fittings, one can easily obtain 20 L/min of sheath flow with one blower, without exceeding the rated blower voltage and current. Mobility particle diameter Dp, [nm] Fig. 2: DMA particle penetration for different flow 3 RESULTS rates (in liters per minute, LPM). One advantage of using higher sheath and aerosol flow rates is easily illustrated by plotting the particle 4 REFERENCES penetration as a function of flow rate for the TSI 3071 [1] TSI, Model 3936 SMPS (Scanning Mobility DMA [2]. Figure 2 shows that particle losses at low Particle Sizer) - Instruction Manual (2001). aerosol flow rates (0.3 L/min aerosol, 3 L/min sheath flow) are not negligible. Furthermore, particle penetra• [2] A. Reineking, J. Porstendörfer, Aerosol Sei. tion for a 10 nm particle is nearly 4 times greater for Technol. 5 483-486 (1986). 127 ONLINE QUASI-CONTINUOUS MEASUREMENT OF ORGANIC ACIDS IN THE ATMOSPHERE R. Fisseha, L. Gutzwiller, E. Weingartner, U. Baltensperger The concentration of some organic acids in the atmosphere was determined using a wet effluent diffusion denuder-aerosol collector coupled with Ion Chromatography. Three organic acids and four inorganic ani• ons were identified and quantified in the air sample, taken from the backyard of PSI. 1 INTRODUCTION Organic compounds are major components of tropo- spheric aerosols [1], of which a greater fraction is be• lieved to consist of mono-carboxylic and di-carboxylic acids [2]. Even though several processes such as burning of fuel and oxidation of alkenes have been identified as primary and secondary sources of these organic acids, a full understanding of their sources is not yet achieved. We adapted a method that has been used for online measurement of inorganic anions to measure different water soluble organic acids in the atmosphere. The work will further be extended to identify the sources of Fig.1: Chromatograms for gas phase and aerosol. these different acids using stable isotope techniques. 11 components were identified in the winter air sample from PSI (peak number 7: carbonate; peak number 8: 2 EXPERIMENTAL unknown, peak number 11: phosphate (contaminant)). A wet effluent diffusion denuder-aerosol collector Peak Compound Aerosol Gas (WEDD/AC) was used to simultaneously sample the no. water-soluble gaseous organic acids and inorganic Det. Mixing Det. Mixing anions (in the dénuder) and aerosol phase (in the limit ratio limit ratio (pptv) (pptv) (pptv) (pptv) aerosol collector) from the atmosphere [3]. A volume of 30 liters of air was sampled (from the backyard of 1 Fluoride 100 600 100 140 PSI)(1l/min during 30min) in November 2000 and 2 Acetate 100 160 100 475 passed through the WEDD/AC. The effluent from both samplers was pumped through a concentrator trap, 3 Formate 250 625 250 1180 which was then analysed using ion chromatography 4 Chloride 100 710 100 80 (IC). The IC system was calibrated using a standard 5 Nitrite ---- solution of 12 anions, including 7 organic acids in or• der to quantify the atmospheric concentrations of the 6 Nitrate 100 1000 100 230 respective gas and particle phase. 9 Sulphate 20 980 20 715 10 Oxalate 20 115 20 320 3 RESULTS The efficiency of the dénuder was measured for gase• Table 1 : Detection limits and measured concen• ous acetic and formic acid to be at least 85% and trations for the identified peaks in the air sample from 75%, respectively. In the atmospheric measurements PSI. only three of the calibrated organic acids; i.e. acetic acid, formic acid and oxalic acid were observed above 4 ACKNOWLEDGEMENT the detection limit (Figure 1). The concentration of all the organic acids that are measured was found to be This work was supported by the Swiss National Sci• higher in the gas phase than in the aerosol phase, ence Foundation. whereas all the inorganic anions that are measured in the atmosphere from the PSI were higher in the aero• 5 REFERENCES sol phase compared to the gas phase. The concentra• [1] J. Heintzenberg, Tellus, 41B, 149-160 (1989). tion of nitrate was higher than any other anion in the aerosol phase whereas formate exhibits the highest [2] A. Limbeck and H. Puxbaum, Atmos. Environ., concentration in the gas phase. Sulphate, fluoride and 33, 1847-1852 (1999). chloride were also measured in the atmosphere and their respective concentrations are given in Table 1. [3] C. Zellweger, M. Ammann, P. Hofer, U. Baltens• perger, Atmos. Environ., 33, 1131-1140 (1999). 128 VERTICAL SIZE DISTRIBUTION OF PARTICLES NEAR A MOTORWAY D. Imhof, U. Corsmeier (IMK), M. Kohler (IMK), F. Fiedler (IMK), E. Weingartner, U. Baltensperger Within the framework of the BAB II project organized by the Institut für Meteorologie und Klimaforschung (IMK) at the Forschungszentrum Karlsruhe, Germany, the vertical profile of the gaseous and particulate traffic emissions were measured close to a highly frequented motorway in Germany. 1 INTRODUCTION emissions, but from abrasion products and resuspen- sion rather than tailpipe exhaust. No height depend• During May 2001 the field campaign BAB II (BAB = ence was observed in the intermediate size range Bundesautobahn) was performed in the area of Hei• because car traffic produces almost no particles in this delberg-Mannheim, Germany, with the participation of size range. a number of different research groups in Europe. The objective was to investigate the emission of particles and of the precursor substances for the formation of photo oxidants along a freeway section. The observed emissions will be compared with modelled emission data. 2 INSTRUMENTAL SET-UP Lifts were installed in two towers (50 m height) on the windward and leeward sides in a distance of 60 m from the motorway on which vertical profiles of the traffic emissions were measured. One lift was 50 100 150 equipped with an Electric Low Pressure Impactor DC Signal [ixm2/cm3] (ELPI, Dekati Ltd., Finland; measuring the particle size distribution between Dp = 40 nm and 8 um) and a Fig. 1 : Vertical profile of the particles active surface Diffusion Charger (LQ 1-DC, Matter Engineering AG, area on the leeside of the motorway (DC). Switzerland, measuring the particle "active" surface area concentration). The time resolution of both in• struments was 3 seconds. Number concentration dN/dlogDp [cm'3] ^•21290 - 45000 10070 - 21290 3 RESULTS ••4767 10070 4767 BU 2255 1067 2255 In the early morning of a clear day with unhindered ÜB 1067 UHU505 - nocturnal radiation and temperatures of about 12 °C ¡ÜÜ239 - 505 239 vertical profiles were taken with the DC and the ELPI «53.5 - 113 ;;;;;;;;; 25.3 - 53.5 on the leeside of the motorway (Fig. 1 and 2). The 12.0 - 25.3 5 66 - 12.0 highest concentrations of particles in the ultrafine 2.68 - 5.66 mode (Dp < 100 nm) and the coarse mode (Dp > 1 1.27 - 2.68 0.04 0.1 0.60 - 1.27 urn) were found near ground; above that level the Particle diameter Dp [uml concentration decreases continuously up to a height of h = 50 m. The change of the concentrations with the Fig. 2: Vertical distribution of mean particle size con• beginning of the morning rush hour can clearly be seen from the six successive profiles. Between 4:50 centrations on the leeside of the motorway (ELPI). and 5:20 a.m., almost the same values were meas• ured. Around 6 a.m., the heavy morning traffic sets in, 4 ACKNOWLEDGMENT which results in a rapid increase of the particle con• centration below h = 20 m. This work was supported by the Bundesamt für Stras• sen (ASTRA). It is interesting to note in Fig. 2 that both, the smaller as well as the larger particles show a distribution very 5 REFERENCES similar to the DC signal. In contrast, no height de• pendence is observed in the intermediate size range [1] D.B. Kittelson, J. Johnson, W. Watts, Q. Wei, M. (Dp = 0.2 - 0.7 urn). This can be explained by the Drayton, D. Paulsen, N. Bukowiecki, SAE Paper primary traffic emission characteristics. The ultrafine No. 2000-01-2122 (2000). particles are mainly composed of soot particles and [2] U. Baltensperger, N. Streit, E. Weingartner, S. particles that are formed during the cooling of the ex• Nyeki, A.S.H. Prévôt, R. Van Dingenen, A. Virk- haust gas directly after emission [1]. The latter parti• kula, J.P. Putaud, A. Even, H. ten Brink, A. Blat• cles are volatile and do not contain soot [2]. The ter, A. Neftel, H.W. Gäggeler, J. Geophys. Res., coarse mode particles are likewise formed by traffic in press (2002). 129 HYGROSCOPIC PROPERTIES OF JET ENGINE COMBUSTOR PARTICLES DURING THE PARTEMIS CAMPAIGN M. Gysel, S. Nyeki, E. Weingartner, U. Baltensperger, A. Petzold(DLR), C.W. Wilson (QinetiQ) The influence of fuel sulphur content (FSC) on particle properties from a jet engine combustor test rig was investigated during the EC-project PartEmis. Hygroscopic growth factors were measured using a Hygro- scopicity Tandem Differential Mobility Analyser (H-TDMA). While particles were hydrophobic at low FSC, hygroscopic growth factors increased significantly with increasing FSC. Under similar conditions small particles were more hygroscopic than large particles. 1 INTRODUCTION Hygroscopic growth is attributed to water uptake of sulphuric acid adsorbed onto a hydrophobic soot core. Particles from aircraft emissions, especially their hy• Experimental results indicate that a small size reduc• groscopic properties, play an important role in contrail tion (< 10%) of the soot core takes place during water formation and cirrus cloud modification. It has been uptake. Theoretical growth curves (solid lines in Figure suggested that natural cirrus clouds are modified [1], 1 ) are fitted to the experimental data by variation of the and that additional cirrus clouds are formed by parti• sulphuric acid volume fraction and the magnitude of cles from aircraft emissions [2]. The potential impact restructuring of the uncoated aggregate. of cirrus cloud change on climate may therefore in• crease due to large growth rates in air traffic. Figure 2 shows the estimated sulphuric acid volume fraction delivered by the fitting procedure. The sul• 2 EXPERIMENTAL phuric acid content appears to increase linearly as a function of FSC. The slope depends on the particle A jet engine combustor was operated on a high pres• size because the sulphuric acid uptake from the gas sure test rig at DERA Farnborough (UK) during the phase is more efficient for small particles. first PartEmis test campaign in January/February 2001. The exhaust was immediately cooled and di• luted before measurement. The fuel sulphur content (FSC) was 50, 410, and 1270 u,g S/g fuel, and is de• —•— 30 n m particles - -o- • 50 n m particles fined here as Low, Mid, and High FSC, respectively. - - - A- - 100 nm particles The hygroscopic growth factor (i.e. D/D0 where D0 = E particle diameter at RH < 10%) of D0 = 30, 50 and 100 — nm particles at relative humidity RH < 95% was meas• ured using a Hygroscopicity Tandem Differential Mo• bility Analyser (H-TDMA) [3-4]. 0 200 400 600 800 1000 1200 1400 3 RESULTS Fuel Sulfur Content [ng/g] 1.20' Fig. 2: Estimated sulphuric acid volume fraction of jet High FSC experiment engine combustor particles as a function of FSC. 1.15' Mid FSC experiment Low FSC experiment 1.10- - Fitted theoretical model 4 ACKNOWLEDGEMENTS 1.05' We thank all PartEmis project partners who contrib• 1.00' uted to successful combustor test rig measurements. 0 10 20 30 40 50 60 70 The financial support of the Bundesamt für Bildung Relative Humidity RH [%] und Wissenschaft, BBW (PartEmis project) is highly appreciated. Fig. 1 : Hygroscopic growth factors of D0 = 50 nm particles at different FSC. 5 REFERENCES [1] J. Ströhm, S. Ohlsson, J. Geophys. Res. 103, Figure 1 shows the hygroscopic growth factors of D0 = 11355 (1998). 50 nm particles at different FSC. At low FSC the parti• cles are hydrophobic with a growth factor of only 1% at [2] O. Boucher, Nature 397, 30 (1999). 95% RH. The particles are significantly more hygro• [3] E. Weingartner, M. Gysel, U. Baltensperger, Envi• scopic at mid and high FSC with growth factors of 10 ron. Sei. Technol. 36, in press (2002). and 16%, respectively. Small 30 nm particles are more hygroscopic than larger 100 nm particles under similar [4] M. Gysel, E. Weingartner, U. Baltensperger, Envi• conditions. ron. Sei. Technol. 36, in press (2002). 130 VOLATILE PROPERTIES OF JET ENGINE COMBUSTOR PARTICLES DURING THE PARTEMIS CAMPAIGN S.Nyeki, M.Gysel, £ Weingartner, U. Baltensperger, A. Petzold(DLR), C.W. Wilson (QinetiQ) The influence of fuel sulphur content (FSC) on exhaust particle properties from a jet engine combustor test rig was investigated during the EC PartEmis project. Volatile properties were measured using a Volatility Tandem Differential Mobility Analyser (V-TDMA). Measurements indicated that particles with diameter d < "30 nm were more volatile than larger particles. 1 INTRODUCTION J.05 O a) V-DTMA 120°C, Combustor "high" Setting Global gaseous and particulate emissions from the CM ever-increasing fleet of aircraft are suspected of causing a small but possibly significant effect on climate [1]. •81.00 Particles may increase cirrus cloudiness, hence result• ing in a reduction of radiative forcing [2]. ê • A U (0 2 EXPERIMENTAL LL a>0.95 A #Low FSC(50ppm) Ol o A jet engine combustor was operated on a high pressure (0 Mid FSC(410ppm) test rig at DERA Farnborough (UK) during the first Par• c A High FSC(1270ppm) CO tEmis test campaign in Jan.-Feb. 2001. The combustor 0.90 was operated under two different compressor and fuel 0 20 40 60 80 100 120 flow conditions, so-called "High" (770 K) and "Low" (570 Aerosol Diameter do (nm) K) combustor temperature settings. Exhaust gases and particles were first cooled and diluted before measure• ment. Three different FSC concentrations were tested: J.05 50, 410, and 1270 ppm, and are defined here as Low, b) V-DTMA 300°C, Combustor "high" Setting O Mid and High FSC, respectively. The volatility of the aero• o CO sol number spectrum was measured at three different temperatures T = 25,120 and 300°C. •81.00 • O O 3 RESULTS A * A u A (0 LL Figure 1 shows the shrinkage factor (i.e. d/d0 where d0 = a>0.95 CA #Low FSC(50ppm) particle diameter at 25°C) as a function of d0 for T = 120 Ol _ O o Mid FSC(410ppm) (0 and 300°C, and for High temperature conditions. The A High FSC(1270ppm) influence of FSC on aerosol volatility at T = 120°C in c CO Figure 1a is not evident. However, smaller particles at 0.90 0 20 40 60 80 100 120 each FSC tend to increase in volatility (i.e. greater Aerosol Diameter do (nm) shrinkage) with decreasing aerosol size. The same phenomenon is seen at T = 300°C in Figure 1 b, where the FSC influence is more apparent. Low temperature Fig. 1 : Combustion particle shrinkage factor for (a) conditions exhibited similar results. T = 120 and (b) 300°C. The greater shrinkage for the High FSC case implies a trend. However, concentrations were less at the ex• larger fractional H2S04 composition, under the proviso treme positions (i.e. 1 and 11). that other parameters are equal i.e. volatile organic carbon compounds. Hygroscopicity measurements also 4 ACKNOWLEDGMENT support the above hypothesis (see Gysel et al., this issue). Additional V-TDMA findings include: We thank all PartEmis project partners who contributed to successful combustor test rig measurements. The 1) Shrinkage factors were measured after adding a financial support of the Bundesamt für Bildung und Shell jet fuel additive (1x and 5x concentration). Aver• Wissenschaft, BBW is highly appreciated. age values d/do = 0.98-1.00 were found at all three V- TDMA temperatures, at both additive concentrations 5 REFERENCES and at low FSC (Mid and High FSC not measured). [1] Aviation and the Global Atmosphere, I PCC Re• 2) Absolute particle number concentrations (cm"3; only port, (1999). dilution corrected) versus inlet probe position (11 rela• tive to the combustor flame) exhibited no significant [2] O. Boucher, Nature 397, 30 (1999). 131 CHEMICAL CHARACTERIZATION OF THE ATMOSPHERIC AEROSOL AT THE HIGH-ALPINE RESEARCH STATION JUNGFRAUJOCH (3580 m ASL) S. Henning, E. Weingartner, M. Schwikowski, U. Baltensperger Aerosol filter samples have been taken continuously in two size classes (total and PM1) at the high-alpine research station Jungfraujoch (3580 m asl, 46°33', 7°59') since July 1999. On these filters major anions and cations within the particulate matter are analyzed by ion chromatography. 1 INTRODUCTION sionally up to JFJ. This effect is less distinct for cal• cium than for the other ions, because its source is Within the Global Atmosphere Watch (GAW) Aerosol mainly mineral dust, which is also locally present and Program of the World Meteorological Organisation, therefore independent of convection. the aerosol chemical composition has been continu• ously measured since July 1999 at the Jungfraujoch • TSP TSP monthly mean EMPA(S0 'l (JFJ). Sampling is performed in two size classes (total 4 O PM1 PM1 monthly mean suspended particles (TSP) and particles with aerody• -, sulphate namic diameters smaller than 1 um (PM1)). Daily TSP and PM1 samples are taken every sixth day, while during extensive field campaigns filters were changed more often. I"" ammonium ÖJ 2 EXPERIMENTAL c .2 io1i The aerosol filters are connected to a heated aerosol inlet (20°C), which is used for all continuous aerosol ï< nitrate measurements at JFJ [1]. c 8 «*i Inside the building the aerosol sam• TSP PM1 c pling line is split into two paths: one 8 "'1 » line samples TSP (left-hand side Fig• S 10-, (d) ure 1) while the other samples PM1 calcium using a 4-stage cascade impactor with a cut-off of 1 um at 11 I min"1. The impactor stages are lubricated with high-vacuum grease to prevent SS88SSSSSSS particle bounce. The flows are main• 00000000000 tained by mass flow controllers. Date 2 + Fig. 2: Mass concentrations of S04 " (a), NH4 (b), 2+ Fig. 1: Filter set-up at JFJ (left-hand side TSP line N03" (c) and Ca (d) in two size classes (TSP and and right-hand side PM1). 2 PM1). For S04 " data from EMPA obtained at the same site are shown also (dashed line in (a)). Each sampling line is equipped with 4 filter-holders. Sample air flows are controlled electronically with a Sulfate (panel a) and ammonium (b) are mainly found system of solenoid valves connected to a vacuum in PM1. These ions are present as ammonium sulfate, pump. During sampling, one filter of each line is ex• which is confirmed by the good correlation between posed at the same time. Each filter-holder consists of these ions (R2 = 0.87). Nitrate (c) is present in PM1 as a filter-pack, which includes first a Teflon and then a well as in the coarse mode (d > 1 um). PM1 nitrate Nylon filter. The downstream Nylon filter is used for originates from ammonium nitrate, whereas calcium the collection of gas-phase nitrate, which might have nitrate and/or sodium nitrate are present in the coarse been evaporated from the first filter. mode. Calcium (d) is predominately present in the coarse mode. 3 RESULTS 4 ACKNOWLEDGEMENTS The filters are analyzed for major ions such as F", 2 CH3COO", HCOO", CH3SO3", CI", N03", SO42', C204 ", We thank the International Foundation Jungfraujoch + + 2+ 2+ and Gornergrat. This work was founded by Meteo- Na , NH4 , rC, Mg and Ca . In Figure 2 the first 1.5 2 + Schweiz under the auspices of the Global Atmosphere year datasets of TSP and PM1 for S04 ", NH4 , N03" and Ca2+ are presented. The observed seasonality is Watch (GAW). explained as follows: during wintertime the JFJ is mainly influenced by the clean free troposphere (FT). 5 REFERENCES Higher mass concentrations are found during summer [1] E. Weingartner, S. Nyeki, U. Baltensperger, J. when convection transports polluted air masses occa• Geophys. Res. 104, 26809 (1999). 132 HYGROSCOPICITY OF AEROSOL PARTICLES AT LOW TEMPERATURES E. Weingartner, M. Gysel, S. Henning, N. Bukowiecki, U. Baltensperger An extensive field campaign was performed at the high alpine site Jungfraujoch (JFJ, 3580 m asi, Switzer• land) with a new Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA). This instrument allows for a fast and accurate determination of the growth distribution of a dry monodisperse aerosol as a function of RH. Aerosol particles from the free troposphere were very hygroscopic, while Saharan dust particles, occasionally also present in the sub micrometer size range, showed a low hygroscopicity. 1 INTRODUCTION Case 2: Saharan dust events. During a few days, dust plumes from North Africa influenced the station. Even At high relative humidity (RH) water is often the domi• though the Saharan dust particles were mainly present nant component of the atmospheric aerosol. The hy• in the coarse mode (D > 1 UJTI) the D0 = 250 nm parti• groscopic properties of aerosol particles are important cles exhibited a bimodal growth distribution, i.e. they because they determine to what extent the particles were present as an external mixture. This is in con• are able to reflect the incoming short-wave solar radia• trast to the simultaneously determined growth spectra tion back to space (direct aerosol effect). In addition, of smaller particles, which were mostly characterized the aerosol hygroscopic properties determine which with a "more" hygroscopic mode only. We attribute the particles may act as nuclei for cloud condensation and "less" hygroscopic mode of the D0 = 250 nm particles thus contribute to the indirect aerosol effect, which to the Saharan dust particles, which were to some refers to the fact that an increased number of cloud extent also present in the sub-micrometer size range. droplets may alter the albedo of a cloud. 2 EXPERIMENTAL During an extensive field campaign at the JFJ (from 15/2/2000 until 31/3/2000) the hygroscopic growth was determined by means of a new Hygroscopicity Tan• dem Differential Mobility Analyzer (H-TDMA) [1]. In this instrument the ambient aerosol is dried and a monodisperse fraction with a certain dry size D0 is exposed to a well-defined higher RH. The resulting new size distribution is measured and a growth factor D/D0 (defined as the ratio of the humidified diameter D to D0) is determined. To ensure a constant tempera• ture within the entire H-TDMA system all components are submersed in a water/ethylene glycol bath, which can be cooled to temperatures below 0°C. At the JFJ, 0.6 0.8 1 1.2 1.4 1.6 1.8 2 measurements were performed close to ambient tem• 35 n i i i i i i i peratures (T = -10°C) to prevent artefacts due to vola• tilization of semi-volatile material (such as organic material and nitrates) from the particles. 3 RESULTS 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Figure 1 shows typical growth distributions of particles Growth factor D/D0 with D0 = 50, 100, and 250 nm. It was found that dur• ing the campaign the particles hygroscopic behavior Fig. 1 : Hygroscopic growth factors at the Jungfrau- can be divided into the following two cases: joch at RH = 85% and T = -10°C for free tropospheric Case 1: Free troposphere (FT). Most of the time conditions (solid points) and during a Saharan dust (-95%), the station was located in the FT, and the event (open squares). shape of the humidified H-TDMA size spectra were characterized by a narrow monomodal growth distribu• 4 ACKNOWLEDGEMENT tion with average growth factors of -1.5 at RH = 85%. This work is supported by MeteoSwiss (Global Atmos• This implies that these particles were to a large extent phere Watch Program). internally mixed regarding their hygroscopic proper• ties. In contrast to the behavior of pure salts, the free tropospheric particles showed no distinct deliques• 5 REFERENCES cence. This indicates that even at low RH a multi- [1] E. Weingartner, M. Gysel, U. Baltensperger, Envi• component aerosol was present in a liquid state. ron. Sei. Technol. 36, in press (2002). 133 STUDY OF THE TROPOSPHERIC AEROSOL AT JUNGFRAUJOCH BY MEANS OF SIMULTANEOUS LIDAR AND IN-SITU MEASUREMENTS R. Nessler (EPF Lausanne and PSI), G. Larchevêque, I. Balín, H. Van den Bergh, B. Calpini (EPFL), N. Bukowiecki, E. Weingartner, U. Baltensperger The Jungfraujoch High Alpine Station is a unique site for atmospheric observation, located at an altitude of 3'580 m and most of the time in the free troposphere. The Paul Scherrer Institute performs various in-situ aerosol measurements at the dungfraujoch, among others particle size distribution, (back)scattering coeffi• cients at three wavelengths (450 nm, 550 nm and 700 nm) and absorption coefficient [1 ]. The latter two are operated continuously within the World Meteorological Organisation's Global Atmosphere Watch (GAW) Program. The EPFL lidar group recently has installed a lidar system based on three wavelengths (355 nm, 532 nm and 1064 nm) which allows the measurement of the aerosol extinction and backscatter properties for altitudes between typically 4 km and 60 km asl [2]. 1 INTRODUCTION 1 hour averages (28/3/2000 from 3.30 until 4.30) The aim of this project is the comparison of the in-situ measured aerosol parameters with the parameter retrieved with the lidar. Since aerosol in-situ meas• urements are mainly performed by sampling through an inlet system into the laboratory at room tempera• ture and thus at dry conditions, the measured aerosol properties may differ from those at outdoor conditions. Results from an intensive measurement campaign on the Jungfraujoch during February and March 2000 (Cloud and Aerosol Characterization Experiment, CLACE), where additional simultaneous in-situ meas• urements were performed indoor and outdoor at am• bient conditions, were used to investigate this bias. -- ... - 2 RESULTS i For certain microphysical properties, a good link be• 10 particle diameter D [nm] tween the measurements at indoor and outdoor condi• tions can be achieved by the following simplifying as• sumption: The indoor aerosol consists only of a dry Fig. 1: Measured number (n), surface (s) and volume core, whereas the outdoor aerosol additionally con• (v) size distributions for indoor (RH < 10%, T= 20°C; tains a certain amount of water which is in equilibrium dashed line) and outdoor conditions (RH = 85%, T= - with the (higher) relative humidity (RH). Thus we are 10°C; dotted line) and the indoor size distributions confronted with the problem of hygroscopic particle corrected to the outdoor conditions (solid line). growth, described by the Köhler theory. To calculate the size of the outdoor aerosol, we used the modified 3 ACKNOWLEDGEMENT Köhler equation [3]. The two unknown chemical pa• We thank the Swiss National Science Foundation and rameters were determined by fitting this model to data MeteoSwiss (GAW Program) for their financial sup• obtained from hygroscopicity tandem differential mo• port, and the International Foundation High Altitude bility analyser (H-TDMA) measurements performed at Research Stations Jungfraujoch and Gornergrat the same time at the Jungfraujoch [4]. (HFSJG) for the possibility to perform the measure• Figure 1 shows as an example size distributions ments. (number, surface and volume concentration), meas• ured at indoor and outdoor conditions together with the 4 REFERENCES corresponding values obtained by correcting the in• [1] S. Nyeki, U. Baltensperger, I. Colbeck, D.T. Jost, door values according to the outdoor relative humidity, E. Weingartner, H.W. Gäggeler, J. Geophys. as described above. This correction works well for the Res. 103, 6097 (1998). surface and volume concentrations and is quite sig• nificant for enhanced RH. It was found that for the [2] B. Calpini, P. Quaglia, Laser Opto 6, 55 (2000). number concentration the reconstruction of the out• [3] F.J. Brechtel, S.M. Kreidenweis, J. Atmos. Sei. door distribution often fails for small particles (D<100 57, 1854 (2000). nm). The reason for this failure is most probably the high volatility of small particles, which causes losses [4] E. Weingartner, M. Gysel, U. Baltensperger, Envi• during the drying process. ron. Sei. Technol. 36, in press (2002). 134 ISOTOPE STUDIES IN THE SWISS CANOPY CRANE PROJECT (SCC) R. Siegwolf, Ch. Körner (University of Basel) In the context of increasing global C02 one focus is, if and to what degree terrestrial vegetation in particular forests can sequester the carbon dioxide in the atmosphere. This topic is assessed with a number of so• phisticated experiments, contributing to an increased understanding of the terrestrial carbon cycle. 1 INTRODUCTION crowns of 62 trees can be accessed with a gondola While 164 nations signed the Kyoto Protocol to limit mounted to a crane of 40 m height, covering an area of 60 m in diameter, which is located in a mixed forest, the C02 emissions, fundamental questions about the carbon cycle in terrestrial ecosystems remain unre• in Hofstetten (47°28' N, 7° 30' E) near Basel. Thus the solved. A number of experiments showed that growth response of adult trees to elevated C02 can be stud• of wheat crop plants was stimulated up to 30% by ied directly without disturbances or changes in the forest microclimate. elevated C02. Similar results were found for tree sap• lings and seedlings. This however, is not applicable for A major focus in the context of elevated C02 is the natural ecosystems and grown forests. Most of the question of where the carbon is going. An ideal tool to conclusions regarding the C02 fertilizing effect rely on trace the fate of carbon is the use of stable C- the extrapolation of short term and small scale ex• isotopes. The gas, which is used to expose the plants 13 13 periments under optimal growth conditions and unlim• to elevated C02 is C depleted (8 C « -31 %<>; ambi• ited nutrient and water supply [1]. Yet the possibility ent air 813C « -8%o), representing an ideal tracer for 3 that C02 fertilisation may be a sink representing the carbon. Via photosynthesis this C-depleted C02 is "missing" atmospheric C02 has stimulated research of incorporated into the plant tissue, leaving its distinct C- the terrestrial carbon cycle, its interactions and limita• isotope signature, allowing the tracing of carbon. Thus tions [2]. In the past ten to fifteen years the focus of one can address questions like i) how much of the interest shifted from single plants and plant communi• newly acquired carbon was used to form new bio• ties to the ecosystem level responses and plant inter• mass, ii) how much was transferred into the soil, in• actions. This has stimulated new generations of tech• creasing the C-reservoir and iii) how much was used nologies and research approaches from constant envi• for maintaining the metabolic processes (respiration). ronment chamber studies via Open Top Chambers to Other aspects like subtle changes in the tree water Free Air C02 Enrichment (FACE) experiments. regime caused by elevated C02 can be revealed by the use of the stable oxygen isotope, which is enriched 2 INSTRUMENTATION in the leaf water during transpiration. The application of stable isotopes in the web-FACE opens new ways The Swiss Canopy Crane project (SCC, carried out by in tracing carbon fluxes and changes of the carbon the Botanical institute of the University of Basel [3, 4]) pools due to increased C02. First results are pre• represents a new design, to expose adult trees to sented by [5, 6]. elevated C02 in their natural environment (Figure 1). 3 REFERENCES [1] Ch. Körner, Towards a Better Experimental Basis for Upscaling Plant Responses to Elevated C02 and Climate Warming. Plant Cell & Environ. 18, 1101-1110 (1995). [2] R.J. Norby, S.D. Wullschleger, CA. Gunderson, D.W. Johnson, R. Ceulemans, Tree Responses to Rising C02 in Field Experiments: Implications for the Future Forest, Plant Cell & Environ. 22, 683-714(1999). [3] SCC-Website:http://www.unibas.ch/botschoen/ G Besteuerung see "Projekte", "Swiss Canopy Crane Project". [4] S. Pepin, Ch. Körner. Web-Face: A New Canopy Fig. 1 : Set up of the web-FACE as applied in the Free-Air C02 Enrichment System for Tall Trees in Swiss Canopy Crane Project [3]. Mature Forests, Oecologia (2002), in press. 3 [5] S. Sigrist, M. Saurer, S. Pepin, Ch. Körner, R. From a 22 m tank pure C02 is released directly to the l8 leave canopy (ca. 2 tons d"1) via a network of irrigation Siegwolf, S 0 Values of Leaf Water in C02 En• tubes (7.5 km of microtubing), installed within the riched Tree Species, this volume (2002). crowns (called web-FACE). The C02 concentration in [6] K. Steinmann, M. Saurer, S. Pepin, Ch. Körner, the crown is monitored and kept at an average of 560 R. Siegwolf, Carbon Transfer in a Mixed Forest ppm by a computer controlled valve system. The Under Elevated C02, this volume (2002). 135 CARBON TRANSFER IN A MIXED FOREST UNDER ELEVATED C02 K. Steinmann, M. Saurer, S. Pepin (University of Basel), C. Körner (University of Basel), R. Siegwolf Besides the terrestrial biomass the soil is considered as one of the most significant carbon sink. Of great interest are forest soils, retaining a considerable amount of carbon. Therefore the carbon exchange be• tween the forest soil and the atmosphere is studied over space and time. First results show that recently fixed C02 is found in the soil respiration in less than three weeks. 1 INTRODUCTION posure of the crowns. The difference reached its maximum in June and October. Since plants act like "carbon pumps" transferring C from the atmosphere into the soil, related processes are highly relevant in the global carbon cycle. About 80% of the terrestrial biomass consists of forests, which contribute 60% of the net primary production. Besides the anthropogenic carbon release rate, the future atmospheric C02 concentration depends also on i) the C02 uptake capacity of the vegetation cover, ii) the soil carbon storage capacity and iii) the respira• tory processes. Since a considerable part of the car• bon loss from the ecosystem is respiration, its tracing and quantification is of great relevance. Therefore a particular focus is given to the tracing of the ecosys• tem carbon fluxes where in this subproject the soil and atmosphere exchange is investigated within the Swiss CO2 enriched area Canopy Crane Project (SCC). 2 EXPERIMENTAL SET-UP Fig. 1: Spatial variability of ô13C-values from soil res• The SCC study site is a highly diverse mixed forest piration in the forest soil, observed in June 2001. stand 15 km south of Basel [1]. A completely new technique, the "web-Face", supplied a constant C02 After the development of leaves in spring, formed from concentration of 560 ppm in the tree crowns. Further reserve carbohydrates, trees show a high demand in details see [2]. Since the C02 used for the fumigation nutrients, when photosynthesis is high. Therefore an 13 is depleted in C (-31%o, atmospheric C02 ~8%o), it investment of carbohydrates into the roots for the de• can be used as a tracer. To follow the transport of the velopment of a big network pays off in favor of the newly assimilated carbon from the crown to the roots acquisition for more nutrients via mycorrhiza. Besides and its temporal and spatial distribution in the soil, we metabolic respiration loss a considerable amount of inserted plastic tubes (15 cm length and 2.5 cm in root biomass dies off, decomposes and is released diameter) into the soil, capped with an airtight septum again as C02. The carbon released from the soil thus on top. 168 tubes were arranged in a grid of 54 m x 60 carries partly the isotopic fingerprint of the freshly m in 3 m distance from each other. Every three weeks formed carbohydrates. In combination with flux meas• the air from the tubes was sampled, and analyzed with urements it is possible using this isotopic signal to an Isotope Ratio Mass Spectrometer (Delta Plus XL), partition the carbon efflux between root and microor• via the Gas Bench II (All equipment by Finnigan MAT, ganism respiration, which will be the topic of further Germany). studies. 3 RESULTS AND DISCUSSION 4 ACKNOWLEDGEMENT Although the spatial variability is considerable (Fig. 1) The Swiss canopy crane project is carried out by the 13 Botanical Institute of the University of Basel. we find a distinct pattern of C-depleted C02 in the soil. This pattern, highly congruent with the C02 expo• sure of the crowns was found already two weeks after 5 REFERENCES the beginning of the C02 fumigation. Thus we see a [1 ] SCC-Website:http://www.unibas.ch/botschoen/ rapid transfer of newly fixed carbon from the tree see "Projekte", "Swiss Canopy Crane Project". crown to the roots and the forest soil. Although the [2] S. Pepin, Ch. Körner, Web-Face: A New Canopy isotopic difference of the soil C02 between the control Free-Air C02 Enrichment System for Tall Trees in and C02 exposed area is small (0.7%o to 1.4%o), we Mature Forests, Submitted to Oecologia (2002). find a distinct signal, caused by the elevated C02 ex• 136 18 5 0 VALUES OF LEAF WATER IN C02 ENRICHED TREE SPECIES S. Sigrist, M. Saurer, S. Pepin (University of Basel), Ch. Körner (University of Basel), R. Siegwolf The increasing C02 concentration in the atmosphere impacts the plant water balance. Stomata (leaf pores releasing water vapor) tend to close, thus reducing transpiration. Oxygen isotope analysis (180/60) in leaf water is used to detect differences in transpiration between C02 enriched and control trees in situ. 1 INTRODUCTION C02 exposed ones. Our data confirm the assumption that elevated C02 reduces transpiration in grown trees Long before global change was a widely discussed as well. issue, it was known that an increase in C02 causes a reduction in stomatal conductance, reducing transpira• tion. In open top chambers [1] the investigation of the C02 effect on transpiration was confirmed, for a model ecosystem, where beech and spruce were growing competitively. It is expected that trees in natural for• ests respond similarly. Yet, with classical plant physio• logical methods subtle differences in tree transpiration are difficult to detect. A promising alternative is the use of stable isotopes. Stable O-isotopes in leaves characterize the plant water regime. The 180/160 iso• tope ratio increases, when air humidity decreases [2]. Tp Qr Pr F3 Cb Ac 18 An other effect however, counteracts H2 0 enrich• species ment: At a given relative humidity increasing transpira• 18 tion decreases the 180/160 isotope ratio, known as the Fig. 1: ô 0 values in leaf water of six tree species. "wash-out" or Péclet effect [3]. Treated (560 ppm), and control trees (375 ppm). Re• peated measures analysis showed significant species 2 EXPERIMENTAL SET-UP effect (p < 0.0001) and treatment effect (p < 0.001) (mean + SE (standard error) for n = 1-8 per treatment As part of the Swiss Canopy Crane project in Hofstet• per species). ten, 14 trees out of 62 were exposed to an average C02 concentration of 560 ppm [4, 5]. Leaves were 4 ACKNOWLEDGEMENT picked from the crane gondola, investigating six differ• ent species; Quercus robur (Qr), Fagus silvática (Fs), Maya Jäggi contributed with valuable discussions and Carpinus betulus (Cb), Prunus silvestris (Pr), Tilia Kathrin Streichenberg with the leaf water extraction. platyphyllos (Tp) and Acer campestre (Ac). At noon time two leaves per tree were sampled at 9 dates be• 5 REFERENCES tween 1 June and 18 September. The leave water was [1] A.J. Jarvis, T.A. Mansfield, W.J. Davies, Stomatal extracted by vacuum distillation, following a high tem• Behaviour, Photosynthesis and Transpiration Un• perature pyrolytic decomposition. The resulting CO der Rising C02, Plant, Cell & Environ. 22, pp639- was analyzed for the 180/160 ratio with a mass spec• 648, (1999). trometer (DELTA Plus XL; Finnigan MAT, Germany). [2] G. Dongmann, H.W. Nürnberg, H. Forstel, 18 3 RESULTS AND DISCUSSION K.Wagener, On the Enrichment Of H2 0 in the Leaves of Transpiring Plants, Rad. and Environ. 18 16 The 0/ 0 ratio in the leaf water of C02 enriched Biophys. 11, (1974). trees was greater than in the control trees [Figure 1]. [3] G.D. Farquhar, L. Lloyd, Carbon and Oxygen According to Dongman et al. [2], the 180/160 ratio in• Isotope Effects in the Exchange of Carbon Diox• creases with decreasing humidity. During our experi• ide Between Terrestrial Plants and the Atmos• ment no differences in ambient relative humidity be• phere In: J.R. Ehleringer, A.E. Hall, G.D. Farqu• tween the C02 exposed and control trees was ob• har, eds., Stable isotope and PlantA/Vater Rela• served. Consequently the differences in transpiration tions, New York, Academic Press, pp 47-70 had physiological causes. Based on the increased (1993). 18 16 0/ 0 ratio of the C02 exposed trees we conclude that the stomatal conductance was reduced for these [4] S. Pepin, Ch. Körner, Web-Face: A New Canopy plants. Therefore the difference in the 180/160 ratio Free-Air C02 Enrichment Systerm for Tall Trees in Mature Forests, submitted to Oecologia (2002). between the C02 exposed and the control plants was caused by the washout (Péclet) effect in the control [5] SCC-Website : http://www. u n ibas .ch/botschoen/ trees, indicating a higher transpiration relative to the see "Projekte", "Swiss Canopy Crane Project". 137 NATURAL C02 SPRINGS: A UNIQUE OPPORTUNITY FOR STUDYING CARBON SEQUESTRATION M. Saurer, P. Cherubini (WSL Birmensdorf), G. Bonani (ETH Zürich), R. Siegwolf Natural C02 springs can be used to study the long-term effects of elevated C02 on plant growth. We ana• lysed 14C and 13C isotope variations over a 50-year period in tree rings of oak trees (Quercus ilex) growing 1 in a Mediterranean ecosystem close to a natural C02 spring. The C02 from the spring is free of C, thus this carbon can be traced in the wood and the amount of carbon uptake from the spring can be calculated. 13 Furthermore, C isotope discrimination under elevated C02 gives clues on physiological changes of the trees. Higher discrimination of trees growing near the spring indicated reduced photosynthetic capacity as a downward adjustment of photosynthesis. The trees in this dry environment may therefore not be able to profit from enhanced levels of C02. 1 INTRODUCTION 1000 atmospheric C02 Forests constitute a large reservoir of carbon, and a 800 • tree rings control change in the carbon storage capacity induced by the 600 • tree rings spring site o fertilizing effect of C02 may have an impact on future 400 atmospheric concentrations. Whereas many studies O 200 on the C02 effect have been carried out on seedlings, the growth response of mature trees is difficult to as• 0 sess. The most serious limitation of artificial fumiga• -200 tion systems is the short time of exposure in compari• -400 son with the life cycle of trees. To overcome this prob• 1 1 1 —i lem C02 springs have been used as a natural experi• 1 950 1960 1970 1980 1990 2000 mental set-up to study the effects of increased levels of C02 on a diverse range of ecosystems. Mineral Fig. 1 : The dashed line indicates the average of at• C02 springs are found, for instance, in volcanic active mospheric 14C-activity for the periods 1951-60, 1961- regions and emit gas with C02 concentrations up to 70, 1971-80, 1981-90 and 1991-98. The full squares 100%. The gas diffuses away from the vent (some• are the tree ring A14C values from the control site, the times a point source) and produces an area of en• open squares are the values from the site near the riched levels of C02. spring. We studied a Mediterranean ecosystem in the To- The 13C-discrimination during photosynthesis ^differ• scana (Italy), where the growth of plants is mainly ence between the isotope ratios of C02 and plant mat• limited by water. At this C02 spring the tree-ring re• ter) is usually difficult to determine in elevated C02- sponse of Quercus ilex was already measured in studies, because of the distinct isotope signal in fumi• comparison with trees growing under normal ambient gation gas and background air. We developed an 2 C0 concentration, but some uncertainties exist on the 14 equation, which uses the C-calculated C02 concen• potential growth stimulation by enhanced levels of tration in the canopy to accurately correct for this ef• C02. Here, we evaluate the use of a dual carbon iso• fect. Our data on the 13C-discrimination indicate an tope method to gain more insight into the uptake of adaptive downregulation of photosynthesis under ele• carbon from the C02 spring into the wood and the vated C02. Mediterranean forests may therefore not physiological reaction of the trees under elevated C02 contribute to carbon sequestration of C02 from fossil [1]- fuel combustion. 2 RESULTS AND DISCUSSION 3 ACKNOWLEDGEMENTS The 14C-activity of wood from trees growing near the Part of the project was funded by CRICEPF (ETHZ) and the Swiss Long-Term Forest Ecosystem Re• C02 spring was consistently lower in comparison with the control site, indicating the uptake of "dead" oc• search Programme (LWF). tree) C02 near the spring (Fig. 1). From these values 4 REFERENCES the effective C02-concentrations in the canopy during the last 50 years can be estimated with a mass bal• [1] M. Saurer, P. Cherubini, G. Bonani, R. Siegwolf ance equation. Surprisingly, the trees from the control Tracing the Carbon Uptake from a Natural C02 site were lower than the 14C-activity of atmospheric Spring in Tree Rings: A Dual Isotope Approach C02, showing that the control trees did also take up (14C and 13C). Submitted to Plant Cell & Environ• some spring C02 (in a distance of 150 m from the ment. spring). 138 VALIDATION OF AN 0-18 LEAF WATER ENRICHMENT MODEL M. Jäggi, M. Saurer, R. Siegwolf 18 The seasonal trend in 8 00/ in leaf organic matter of spruce needles of mature trees could be modelled for two years. The seasonality was mainly explained by the 8180 of top-soil water, whereas between years differences were due to variation in air humidity. Application of a third year's data set improved the correla• 18 tion between modelled and measured 8 00/ and thus validated our extended Dongmann model. INTRODUCTION 18 T3 The model, describing the 0 enrichment in leaf water CD i_ (8180|), proposed by Dongmann [1], is mainly driven D CO CO by air humidity (ea/e¡=ratio of vapor pressures in the cu atmosphere and in the intercellular spaces) and the Ê 18 18 8 0 value of the source water (8 Os), (equation 1): Si Ö l l =S«Os + ek +ee +(S™0V -S«Os-ek)^ (1) o 00 where first, e is the kinetic factor, and second, e is k e -1— -1— —i— the equilibration factor, which is due to the change of 24 25 26 27 28 29 30 18 phase from liquid to vapor, and 8 Ov is the isotopic 18 S 00| [%o] modeled composition of water vapor in the air. This model (equation 1) was adapted for wood cellulose by Saurer 0 et al. [2], introducing a biochemical fractionation (ec) Fig. 1 : Correlation between 8 0 i of modelled and and a dampening factor (/), summarizing the effect of measured spruce needle organic matter in mature leaf water inhomogeneity and the exchange of oxygen trees for three experimental years (1998-2000). atoms of sucrose with stem water. More important, however, is the fact that the slope of Our field experiment allowed us to test, if 8180 of the modelled versus the measured data for the three 18 whole leaf organic matter (termed 8 00|) in current years increased up to 0.82 (for 1998-1999: 0.74). This needles of mature trees can be modelled for a two- indicates further that adding a third year of data clearly year dataset and if a third year of data will validate our reduced the overestimation by the model, and that proposed extended Dongmann model [3]. differences between years can mainly be explained by changes in air humidity, irrespective of the precipita• 2 EXPERIMENTAL SET-UP tion amounts. The site Schladholz in Unterehrendingen, Switzerland, 18 These results point out that 8 00| in whole needle was replanted in 1930 and consists mainly of spruce organic material can be modelled reliably in field (Picea abies), and beech trees (Fagus sylvatica). For grown mature spruce trees, and can thus be used for three consecutive years (1999: wet year; 1998 and reconstruction of the seasonal climate course. 2000: dry years), current spruce needles were sam• pled at various times from 16 experimental trees. Soil 4 ACKNOWLEDGEMENT water was additionally sampled (10-25 cm depth). The oxygen isotopic composition of whole needle organic This experiment was part of the COST E6 and material and of soil water was determined with a con• HARWA (BUWAL) project. tinuous flow mass spectrometer (Delta-S Finnigan). 5 REFERENCES 3 RESULTS AND DISCUSSION [1] G. Dongmann, H.W. Nürnberg, H. Forstel, K. We were able to extend the model (equation 1, Wagener, Radiât. Environ. Biophys. 11, 41-52 18 adapted for cellulose [2]) for 8 00| values of whole (1974). needle organic matter, adapting (/) as (forg) and (ec) as [2] M. Saurer, K. Aellen, R. Siegwolf, Plant Cell Envi• (e0rg). with the two factors calibrated with a controlled experiment of spruce saplings (equation 2): ron. 20, 1543-1550 (1997). [3] M. Jäggi, M. Saurer, J. Fuhrer, R. Siegwolf, ô180 ol s + org (2) S^ -6^ f ek+ee + (ô^v-ô^s-ek)^ + e in Needles of Picea Abies Responds to Environ• org mental Conditions, but not to Treatments with Adding the third year's dataset (2000), allowed us to Fertilizer, Irrigation, or Wood-Ash. Submitted to 18 Tree Physiol. explain 62 % of the variation in 8 00|. 139 Energy Systems Analysis 140 141 A MERGE MODEL WITH ENDOGENOUS TECHNOLOGICAL CHANGE S. Kypreos, O. Bahn A new version of the MERGE model, called MERGE-ETL, has been developed to consider endogenous technological change in the energy system. The basic formulation of MERGE-ETL as well as some first results are reported here. 1 INTRODUCTION lative cost (TC) curve expressed as the integral of the specific cost curve. TCkt serves to compute the in• Several energy optimisation models have introduced vestment cost ICKt as the difference of two time con• lately an endogenous representation of technological secutive values of TC. ICkit is in turn used to compute change; see for instance Messner [1], Mattsson and the energy production cost PCkt as follows: Wene [2], or Kypreos et al. [3]. They typically repre• sent specific investment cost of a given technology as a function of its cumulative capacity; reflecting that where frk is the fraction of the production cost not in• some technologies experience declining costs with an cluded in the endogenous cost reduction process. It is increasing adoption, see Grübler [4]. PSI has imple• related to O&M and fuel costs. mented such an approach in the MERGE model of Manne and Richels [5] for a set of electric and non• electric energy technologies. 3 SOLVING TECHNIQUES Endogenous learning is associated with increasing 2 MODELLING FRAMEWORK returns, and the mathematical formulation of MERGE- ETL corresponds to a non-linear and non-convex op• 2.1 Merge timisation problem. Because of this non-convexity, the MERGE is a Model for Evaluating the Regional and commercial solver MINOS [6] traditionally used to Global Effects of GHG reduction policies. In MERGE, solve MERGE does not guarantee to find the global the world is divided into nine geopolitical regions. An optimum of MERGE-ETL, but only a local one. In or• ETA-MACRO model describes each of these regions. der to find a global optimum, we have developed a This latter model is itself a link of two sub-models, three steps approach. ETA and MACRO. ETA is a 'bottom-up' engineering MERGE is first solved to define equilibrium energy model. It describes the energy supply sector of a given demands. These (fixed) demands are input into a region, in particular the production of non-electric en• regional ETA-ETL model, which corresponds to the ergy and the generation of electricity. MACRO is a bottom-up part of MERGE-ETL. Following Barreto and 'top-down' macro-economic growth model. It balances Kypreos [7], ETA-ETL is linearised and solved using the rest of the economy of a given region using an mixed integer programming techniques. In a second aggregated production function. The mathematical step, MERGE-ETL is solved by MINOS, using as start• formulation of MERGE can be cast as a convex non• ing points for the energy sector the optimum values linear optimisation problem, where the economic equi• found by ETA-ETL and the ones found by MERGE for librium is determined by a single optimisation. MERGE the rest of the economy. This usually provides a rea• is thus an optimisation equilibrium model. sonable approximation for the localisation of the global 2.2 Merge-ETL optimum. A third step may be necessary if cumulative capacities (of the learning technologies) differ between In MERGE, technological learning is not considered. ETA-ETL and MERGE-ETL. In that case, one repeats Instead, energy technologies have over time fixed the solving of these two models until cumulative ca• characteristics, e.g., fixed production cost. In MERGE- pacities are equal. ETL, endogenous technological learning (ETL) is ap• plied to specific energy technologies. 4 CASE STUDIES In the so-called 'one-factor learning curve' formulation As an illustration, we have considered scenarios re• considered here, the cumulative capacity CCkt is used lated to C02 emissions and technological learning. In as a proxy for the accumulation of knowledge that the baseline (Ba) case, emissions are not limited. It affects the specific investment cost SCkit of a given assumes a world population level of 10 billion by 2050 technology k at period of time f. CCkit is computed as in the IPCC B2 scenario. Between 2000 and 2050, based on the energy production, whereas SCkit is de• world GDP grows 3.5 times, whereas primary energy fined as: supply and carbon emissions grow by 2.6 only. In the 2 SC/cr = a . CCkt control (Co) case, C0 emissions are limited as fol• lows. Annex I regions must fulfil their Kyoto target by where a is a parameter given by the initial point of the 2010 and reduce their emissions by 5% per decade learning curve and ó is a learning index that defines afterwards. Non-Annex I regions have the same re• the speed of learning. Rather than this specific in• duction rate between 2030 and 2050, and before, vestment cost curve, MERGE-ETL uses a total cumu• emissions are bounded by their baseline levels. The 142 Co case assumes also trading of C02 emissions per• mits among the regions. Notice that the last letter of • SOLAR PV the full scenario name serves to distinguish whether • WIND Turbine technological learning is considered (L case) or not (A/ • HYDRO case). In the L case, six learning technologies have • NUCLEAR been considered for the generation of electricity: ad• • GAS Fuel Cell vanced coal, gas combined cycle, gas fuel cell, new • GAS Removal nuclear, solar PV and wind turbine. • GAS CC • GAS Turbine Figure 1 gives first the implication of considering en• • OIL • COAL Removal dogenous technological change on world GDP. • COAL Adv. • COAL Conv. 95.00 1990 BaN BaL CoN CoL 94.00 93.00 Fig. 3: World electricity generation in 1990 and in 2050 per case. O 92.00 to 3 5 CONCLUSION E 91.00 » 90.00 a. MERGE-ETL is a valuable tool to assess endogenous Q technological change in the energy system and study O 89.00 the implications of C02 control policies. This model 88.00 shows in particular that early investments in cleaner 87.00 and more efficient energy technologies pay off, as this BaN BaL EHCoN ECoL brings low-cost reduction options and hence reduces GDP losses for C02 emission reduction. Fig. 1 : World GDP per case in 2050. 6 ACKNOWLEDGMENT Figure 1 shows that technological learning yields GDP This research has been funded by BBW (Contract N. growth in the Ba case and reduces GDP losses in the 99.0185) as part of the EU Research Project ENG2- Co case. Indeed, through the learning mechanism, the 1999-0003 'SAPIENT. production of energy becomes cheaper and absorbs thus less economic resources. Figure 2 gives next 7 REFERENCES implications on global primary energy use. [1] S. Messner, Endogenised technological learning in an energy systems model, J. Evolutionary Eco• nomics?, 291-313 (1997). [2] N. Mattsson, CO. Wene, Assessing new energy technologies using an energy system model with • WND+SOL endogenized experience curves, Int. J. Energy M HYDRO+BIO Research 21, 385-393 (1997). • NUCLEAR • GAS [3] S. Kypreos, L. Barreto, P. Capros, S. Messner, • OIL ERIS: A model prototype with endogenous tech• • COAL nological change, Int. J. Global Energy Issues 14, 374-397 (2000). [4] A. Grübler, Technology and Global Change, 1990 BaN BaL CoN CoL Cambridge University Press, Cambridge (1998). [5] A.S. Manne, R.G. Richels, Buying Greenhouse Insurance: The Economic Costs of C02 Emission Fig. 2: World primary energy use in 1990 and in 2050 Limits, MIT Press, Cambridge (1992). per case. [6] B.A. Murtagh, M .A. Saunders, MINOS 5.4 User's Figure 2 shows that technological learning yields for Guide, SOL 83-20R, Stanford University, Stan• both cases, on the one hand, an increase of primary ford (1995). energy use as energy production becomes less ex• pensive and substitutes for capital and labour, and on [7] L. Barreto, S. Kypreos, Technological Learning in the other hand, an increase of the use of renewables Energy Models: Experience and Scenario Analy• in particular for electricity generation as shown in Fig• sis with MARKAL and the ERIS Model Prototype, ure 3. PSI Report 99-08, Villigen (1999). 143 THE ROLE OF SPILLOVERS OF TECHNOLOGICAL LEARNING IN A "BOTTOM-UP" MARKAL MODEL OF THE GLOBAL ENERGY SYSTEM L. Barreto, S. Kypreos An important criterion in the analysis of climate policy instruments is their ability to stimulate the techno• logical change necessary to enable the long-term shift towards a low-carbon global energy system. In this paper, using a multi-regional "bottom-up" MARKAL model of the global energy system, which incorporates endogenous technological learning, the effect of spillovers of technological learning in the deployment of electricity generation technologies is examined when Kyoto-like C02 constraints are imposed on the global energy system. 1 INTRODUCTION using and learning-by-interacting processes [2]. The specific investment cost (SC) is formulated as: The implementation of C02 reduction goals will cer• tainly influence the technological path of the energy SC(CC) = a*CC-b systems of committed and non-committed regions. There has been a debate as to how targets, such as Where: those agreed upon in Kyoto, and the flexibility mecha• CC: Cumulative capacity nisms allowed in their implementation would affect the b: Learning index energy technology innovation necessary to achieve a a: Specific cost at unit cumulative capacity low-carbon energy system in the long run. It has been Learning curves are incorporated in the MARKAL argued, for instance, that the unrestricted allowance of model using Mixed Integer Programming (MIP) tech• emissions trading could discourage the development niques. The MIP approach provides a linearisation of and introduction of more efficient and clean energy the otherwise non-linear and non-convex problem by technology innovations in permit-buying regions, be• applying a piece-wise interpolation of the cost curve. cause of the availability of cheaper mitigation options Integer variables are used to control the sequence of elsewhere. It becomes important to examine the inter• segments along the curve [1]. actions between climate policies and energy technol• ogy dynamics mechanisms. The link between climate change mitigation policies Investment Costs (USVkW) 10000 and energy technology innovation is complex and Solar Photovoltaics , many different factors intervene. Nonetheless, our PR=81% Advanced Coal New Nuclear PR=94% PR=96% understanding of the forces involved must be im• proved. Here, using a five-region "bottom-up" global MARKAL model of the global energy system that en- dogenises technological learning, some insights are 1000 gained into the role of spillovers of technological learn• ing across regions [1]. For such purpose, the deploy• ment of electricity generation technologies, whose investment costs follow learning curves, is analyzed Wind Turbine Gas Combined Cycle PR=90% PR=90% under different C02 constraints. 100 "+- 0.1 1 10 100 1000 10000 2 MODELLING APPROACH Cumulative Capacity (GW) Addressing the question of the feedbacks between climate change policies and energy technology innova• Fig. 1 : Learning curves assumed for different electric• tion requires an adequate treatment of technology ity generation technologies in this analysis. dynamics in energy-systems models. Here, the atten• tion focuses on technological learning, a key driving The attention has primarily been concentrated in a force of technological progress. Learning plays an global learning scenario. Capacities deployed across important role in cost/performance improvement of all regions are added up to obtain the global cumula• technologies, stimulating the competition and continu• tive capacity, which is used for the computation of the ous substitution between them in the marketplace. corresponding investment costs. Assuming global learning has an important implication for the diffusion A typical learning curve describes the specific cost of of the learning technologies. With all regions contribut• a given technology as a function of the cumulative ing to the cost reduction, deploying the technology in capacity, a proxy for the accumulated experience. It one of them translates into a reduction of the specific reflects the fact that some technologies may experi• cost common to all of them. Thus, installations in a ence declining costs as a result of their increasing given region will contribute, through the so-called adoption, due to the accumulation of knowledge learning spillovers, to render a learning technology through, among others, learning-by-doing, learning-by- more cost-effective also in other regions. 144 Here, a model of the full global energy system is ap• spillover across regions is possible, other regions can plied. Five regions are considered: Two regions repre• benefit from the learning stimulated by tighter envi• sent industrialised countries: North America (NAM) ronmental policies in a given region. and the rest of the OECD (OOECD). One region brings together economies-in-transition in the Former Soviet Union and Eastern Europe (EEFSU). Two addi• Gas Combined-Cycle tional ones portray the developing world: One of them groups the developing countries in Asia (ASIA) and the other comprises Latin America, Africa and the § 18000 i Middle East (LAFM). • Reference a 12000- O Kyoto Trend-No Trade 3 SOME RESULTS (5 H Kyoto Global-No Trade As an illustrative example we consider two carbon- u constrained scenarios: The first is a "Kyoto trend" sce• a nario where Annex I regions (i.e. NAM, OOECD, LU EFFSU) are compelled to reach their Kyoto targets by NAM OOECD EEFSU ASIA LAFM 2010 and to follow, from this target, a linear reduction of 5% per decade until the end of the horizon. The second is a "Kyoto global trend" scenario, which as• Solar PV sumes that non-Annex I regions (i.e. ASIA and LAFM) ^ 6000 commit themselves to an emissions reduction of 5% c per decade from their baseline values in 2030, while g Annex I regions face the same targets as in the Kyoto- "•E5 v trend. c o • Reference (5 B Kyoto Trend-No Trade The results of these scenarios are used here to illus• H Kyoto Global-No Trade S& 2000 trate the difference between a model with multi- o II regional spillover of learning and one without it. Fig. 2 O compares the outputs of two learning electricity tech• o LU • nologies (gas combined-cycle and solar photo-voltaics NAM OOECD EEFSU ASIA LAFM (SPV)) for the year 2050 in the different regions in the Kyoto-trend and Kyoto-global trend cases when no Fig. 2: Electricity generation of two learning technolo• C02 emissions trade is permitted. That is, when the gies in 2050. A comparison between Kyoto-trend and only link between regions is the (here assumed full Kyoto global-trend cases without emissions trading. global) learning spillover. Global learning. Despite the fact that Annex I regions face the same constraint in both cases and are compelled to fulfil it 4 CONCLUSION with their "in-house" mitigation efforts, the technology The effects of spatial spillovers of learning in the de• outcome is not the same in those regions for both ployment of energy technologies under different C02 cases. In the second case, the fact that non-Annex I constraints have been studied here. The role of cli• regions also commit themselves to achieve reductions mate change policies in stimulating/hindering techno• alters the dynamics of diffusion of some of the learn• logical learning is complex and dependent upon many ing technologies. In particular, solar PV penetrates in factors. The final effects are highly dependent on the Annex I regions under the Kyoto global-no-trade sce• configuration of the learning networks, the policy nario. Also, the gas combined-cycle alters its penetra• mechanisms implemented to fulfil the commitments, tion as compared with the Kyoto-trend-no-trade one. the magnitude of learning spillover between regions This effect cannot be taken into account in a conven• and the level and location of the carbon constraint tional linear programming model. In such model, the imposed. technology mix in the Annex I regions is bound to be the same in both cases because no mechanism of 5 REFERENCES interaction between regions is present. Thus, consid• ering multi-regional learning spillovers improves the [1] L. Barreto, Technological Learning in Energy modelling of technological change induced by environ• Optimisation Models and Deployment of Emerg• mental constraints. First, under the presence of the ing Technologies. Dissertation ETH Zurich No learning mechanism, the imposition of environmental 14151 (2001). constraints can induce cost reductions (increasing competitiveness and likelihood of diffusion) of envi• [2] L. Argote, D. Epple, Learning Curves in Manufac• ronmentally compatible technologies. Second, when turing, Science 247 920-924 (1990). 145 INTEGRATING LCA DATA INTO A MARKET ALLOCATION MODEL FOR CAR POWERTRAINS A. Röder A new approach has been used for the assessment of different car powertrains and fuels. This approach combines two methods that have been in use at PSI for many years: Life-Cycle Assessment (LCA) and Energy-Economic Modelling. This combination allows taking into account all emissions and costs caused by the use of a car over its whole life cycle, but also makes possible the inclusion of other aspects such as endogenous learning or restricted resource availability. The results show that boundary conditions such as fuel costs or emission taxes have an enormous influence on the ranking of the different powertrains and fuels. 1 INTRODUCTION (CNG), methanol (MeOH) and compressed hydrogen (CH2) from various sources, and some biofuels, e.g. The transportation sector is one of the major sources ethanol (EtOH) from wheat. for emissions of pollutants and greenhouse gases. Already in 1998 a paper was presented in PSI Scien• In the reference scenario (no caps, no emission taxes, tific Report Volume V that discussed the options and constant prices for fossil fuels, moderate assumptions limitations of reducing greenhouse gas emissions by on emerging technologies) there is no switch of fuels switching to new car powertrain concepts and alterna• or powertrains: the advanced gasoline vehicle domi• tive fuels [1]. This work has meanwhile been extended nates the market (Figure 1). to pollutant emissions such as S02 or NOx; costs for car manufacturing, maintenance and the various steps of the different fuel chains have also been analysed. Shares of Vehicle Technologies IT Conventional gasoline & Conventional diesel These environmental and cost data have then been PAdvanced gasoline integrated into MARKAL, an energy-economic plan• ning tool that has been in use at PSI for different stud• ies. Shortly said, MARKAL shows how predefined de• mands (in our case: transport by cars in OECD Europe plus Turkey from 1995 to 2040) can be most cost-efficiently met with given technologies and under given boundary conditions. Environmental externalities can be considered by either 2000 2005 2010 2015 2020 2025 2030 2035 2040 Year > applying a tax on emissions Fig. 1 : Shares of vehicle technologies over time in or the reference scenario, mid-class cars. > defining caps, i.e. maximum allowable totals, for emissions. Despite growing demand total consumption of final energy slightly decreases until around 2030 due to the Compared to a static cost comparison (where emis• assumed efficiency gains (Figure 2). sion taxes can also be included) this sophisticated model allows taking into account additional aspects. One of the most important advantages especially for Energy Consumption the evaluation of emerging technologies is the possi• ^Gasoline SDiesel BMeOH from NG bility to model endogenous technological learning (e.g. 7000 by considering reduced costs due to accumulation of 6000 experience expressed as the cumulative deployment 5000 of these technologies) [2]. 2 SOME RESULTS In the analysis environmental and economic data for three vehicle classes that cover the majority of total i r car transport demand (small, compact, and mid-class 2000 2005 2010 2015 2020 2025 2030 2035 2040 cars) are included. The powertrain configurations Year available are the conventional power train with internal Fig. 2: Consumption of final energy in the reference combustion engine (ICE) and a hybridised fuel cell scenario. (FC) powertrain with supercapacitors for short-term storage of electrical energy. The fuels include gasoline A completely different picture is evolving when rather and diesel from crude oil, compressed natural gas high taxes on emissions of pollutants (e.g. 34 Fr/kg 146 N0X) and greenhouse gases (0.21 Fr/kg C02-eq) are 3 CONCLUSION introduced: In the mid-class sector, the CNG car with internal combustion engine is the most cost-efficient The new approach is a sophisticated tool for a com• option (Figure 3); in the class of the small cars, how• prehensive and consistent evaluation of technologies. ever, the relative efficiency advantage of the fuel cell It can significantly enhance understanding the poten• powertrain is more noticeable, and thus this technol• tials of competing technologies. ogy dominates the market in the last periods (Figure For the analysis of different car powertrains and fuels 4). The main feedstock for methanol is natural gas; much more scenarios than the ones depicted above the production from scrap wood is limited to a small were analysed. The results on the technology level share of the total demand. can be summarized as follows: It is interesting to note that, due to the time required > with constant prices for fossil fuels and without for technological learning, the FC vehicle is introduced specific measures to mitigate emissions of only after a delay of about 10 years. In the meantime, pollutants and greenhouse gases today's pre• the CNG car dominates. dominant fuels (gasoline and diesel) and ma• jor conversion devices (internal combustion Shares of Vehicle Technologies engine) are very likely to continue dominating m Conventional gasoline B Conventional diesel the market. Even in a long-term perspective • Advanced gasoline B Advanced diesel other concepts are only competitive if very op• S CNG HMeOH ICE timistic goals for their costs can be achieved. 100% wttfwssssssssssssa,^^ > fuels made from biomass become an interest• ing option in scenarios where a reduction of greenhouse gas emissions is pursued or when the prices for fossil fuels increase. > the combination of a conventional powertrain (internal combustion engine) and fuels that are derived from natural gas (especially com• pressed natural gas, but also methanol) offer 2040 a cost-effective option for mitigating pollutant emissions and moderate reductions of green• house gas emissions. Fig. 3: Shares of vehicle technologies over time in the scenario with high pollutant and greenhouse gas > if conditions require significant improvements taxes, mid-class cars. in the overall efficiency of the whole fuel chain from well to wheel, e.g. because of escalating Shares of Vehicle Technologies fossil fuel prices or the need to significantly m Conventional gasoline B Conventional diesel reduce greenhouse gas emissions, the fuel • Advanced gasoline B Advanced diesel cell has the potential to drive the conventional powertrain out of the market. Early invest• H CNG 0 MeOH FC ments are necessary to mature this technol• • CH2FC ogy, but if the long-term cost goals for fuel 100% cells are achieved, these investments are more than offset by savings in later periods. These results are based on today's knowledge and some very coarse estimates; a regular update and further development of both methodology and data• base are desirable. 4 REFERENCES 2040 [1] A. Röder, GHG-Emissions for Cars with Different Power Trains over the Whole Life Cycle, PSI Sci• Fig. 4: Shares of vehicle technologies over time in entific Report 1998 Vol. V, 106-107. the scenario with high pollutant and greenhouse gas taxes, small cars. [2] L. Barreto, Technological Learning in Energy The consumption of final energy is also smaller than in Optimisation Models and Deployment of Emerg• the reference case, mainly due to the significantly ing Technologies, Dissertation, ETH Zürich higher efficiency of the fuel cell powertrain. (2001). 147 Appendix 148 149 APPENDIX PROJECT COLLABORATIONS WITH EXTERNAL Projektleiter: I. Mantzaras PARTNERS AZEP: (Advanced Zero Emissions Power Plants EU-Projekt ALLIANCE FOR GLOBAL SUSTAINABILITY Projektleiter: A.S.H. Prévôt, U. Baltensperger Projekleiter: S. Kypreos ARTEMIS (Assessment and Reliability of Transport Energy Modelling, The China CETP Programme Emission Models and Inventory Systems) EU-Projekt Projektleiter: A. Wokaun The Future of Mobility: New Technologies and Projektleiter: R.T.W. Siegwolf Policies Shaping Transportation Supply and Demand Effects of Elevated C02 and N on Carbon Uptake Allocation, Respiration and Sequestration in ASTRA/BUWAL Grass/Clover Mixtures in a Face Study EU-Projekt Projektleiter: R. Gehrig*, U. Baltensperger, E. Weingartner Projetkleiter: R.T.W. Siegwolf, J. Fuhrer* Verifikation von PM10-Emissionsfaktoren des Eurosilva - HARVA (Optimale Ernährung und Strassenverkehrs Holzasche - Recycling im Wald) * EMPA, Dübendorf EU-Projekt * IUL Birmesdori BAUGARTEN FOUNDATION BFE Projektleiter: A. Steinfeld SYNMET (Solar Combined ZnO-Reduction and Projektleiter: S. Biollaz Natural Gas Reforming for the Co-Production of Zinc Redox Filter: Decentralised Production of Pure and Syngas) Hydrogen from Wood BBW Projektleiter: T. Gerber Investigation of Soot and NO Production in Spray Projekleiter: O. Bahn Combustion of Acetal/Diesel Mixtures TCH-GEM-E3: The Role of Innovation and Policy Projektleiter: T. Gerber Design in Energy and Environment for a Sustainable Growth in Europe Darstellung und Spektroskopie von ZnO bzw. ZnxOy EU-Projekt in der Gasphase Projektleiter: T. Gerber Projektleiter: U. Baltensperger Verbrennungsreaktionen in Gegenwart sauerstoff• SINGADS (Synthesis of Integrated Global Aerosol Data Sets) haltiger Brennstoffe EU-Projekt Projektleiter: P. Griebel Projektleiter: U. Baltensperger, E. Weingartner Struktur turbulenter Vormischflammen unter Hoch• PARTEMIS (Measurement and Prediction of druck Emissions of Aerosols and Gaseous Precursors from Gas Turbine Engines) Projektleiter: W. Hubschmid EU-Projekt Laserspektroskopische Methoden zur Analyse von Flammen und Brennstoff-Sprays Projektleiter: S. Kypreos ACROPOLIS (Assessing Climate Response Options: Projektleiter: W. Hubschmid Policy Simulations - Insights from Using National and Quantitative Laser-Induced Fluorescence in International Models) Combustion EU-Projekt Projektleiter: M. Koebel Projektleiter: S. Kypreos NOx-Verminderung bei mobilen Dieselmotoren mittels SAPIENT (Energy Systems Analysis for Progress and Harnstoff-SCR Innovation in Energy Technologies) EU-Projekt Projektleiter: R. Palumbo, A. Steinfeld Solar Thermal Production of Zinc 150 Projektleiter: G.G. Scherer EU Polymer Elektrolyt Brennstoffzellen mit H2 und Methanol als Brennstoff Projektleiter: P. Novák High Performance Smart-Card with Inductive Projektleiter: A. Steinfeld Charging SolarPACES: Solar Power and Chemical Energy Systems EU-Project CRAFT Projektleiter: M. Sturzenegger Projektleiter: P. Novák Auf dem Weg zu solaren Brennstoffen - Physikalisch• Solvent-Free Lithium Polymer Starter Battery. 5th EU chemische Beiträge zur Entwicklung von Solar• Program - Energy, Environment and Sustainable reaktoren Development Projektleiter: A.S.H. Prévôt, S. Nyeki BFE AND INDUSTRIAL PARTNER CHAPOP (Characterisation of High Alpine Pollution Plumes) Projektleiter: W. Hubschmid Teilprojektleiter: A. Inauen GEBERT RUF STIFTUNG Homogene Gasverbrennung Aistom (Schweiz) AG Projektleiter: Ch. Ludwig TG-ICP-OES unterstütze Thermo-Desorptions- Projektleiter: A. Meier Spektrometrie Solar Production of Lime QualiCal, Bergamo, Italy HSK Projektleiter: A. Steinfeld, W. Hoffeiner Projektleiter: F. Gassmann Solar Thermal Processes for Closed Materials Cycles ADPIC- Aktualisierung RWH Consult GmbH, Oberrohrdorf AG IEA BUWAL Projekleiter: S. Kypreos Projektleiter: U. Baltensperger Activities Implemented Jointly to Curb CO2 Emissions PM10-Immission IEA-ETSAP/Annex VII Projektleiter: A.S.H. Prévôt INDUSTRY TOSS (Trends of Ozone in Southern Switzerland) Projektleiter: S. Biollaz Projektleiter: A.S.H. Prévôt Commercialisation of integrated waste incineration YOGAM (Year of Gasphase and Aerosol and ash treatment technology Measurements) Consortium PECK (PSI, Eberhard Recycling AG, CT Umwelt AG, Küpat AG) DOE/FHA Projektleiter: W. Durisch Projektleiter: U. Baltensperger, E. Weingartner, Thermophotovoltaische Erzeugung von Wärme und H. Burtscher*, D.B. Kittelson** Strom mit Erdgas Spark Ignition Engines Forschungs-, Entwicklungs- und Förderungsfonds der * Fachhochschule Aarau Schweizerischen Gasindustrie (FOGA) ** University of Minnesota, Minneapolis, USA Projektleiter: W. Durisch EPFL Verhalten von Photovoltaik-Generatoren unter realklima tischen Betriebsbedingungen Projektleiter: U. Baltensperger, E. Weingartner Projekt- und Studienfonds der Elektrizitätswirtschaft Synthesis of Lidar, Optical Depth and in Situ Aerosol (PSEL) Data at the Jungfraujoch Projektleiter: O. Haas, S. Müller ETH-Rat Technologie-Transfer-Projekt "Elektrisch Wiederauf- ladbare Zink-Luft Batterie" Projektleiter: S. Biollaz Zoxy Energy Systems AG, Halsbrücke, Deutschland Methanation of Biomass: Feasibility Study (Pilotprojekt im Rahmen der Strategie Nachhaltigkeit) Projektleiter: W. Hubschmid Messungen an Gasturbinen Projektleiter: E. Weingartner, H. Burtscher* Aistom (Schweiz) AG CCN Counter * Fachhochschule Aargau 151 Projektleiter: M. Koebel Projektleiter: I. Mantzaras Entwicklung eines mobilen SCR-Systems für Modellierung und Auslegung eines C02 und NOx Dieselmotoren freien Brenners für Aistom Power Gasturbinen Liebherr Machines Bulle SA und Oberland Mangold, Garmisch-Partenkirchen, Germany Projektleiter: A. Wokaun, I. Mantzaras, J. Wambach, F. Ferroni* Projektleiter: E. Newson Experimentelle Untersuchung von extrem dünnen Hydrocarbon Reforming Schichten (Nanoschichten) für die Katalyse Robert Bosch GmbH, Germany (Rekombination von Wasserstoff) * Electrowatt Engineering AG, Zürich Projektleiter: E. Newson Catalytic Hydrogen Burner Projektleiter: J. Wochele, Ch. Ludwig Giacomini s.p.a., Italy PyroBat Projektleiter: E. Newson BATREC AG, Wimmis Ambient Temperature Ignition of Methane/Hydrogen/ Air Mixtures on Catalytic Combustion Catalysts METEO SCHWEIZ Gaz de France, France Projektleiter: U. Baltensperger, E. Weingartner GAW (Global Atmosphere Watch Programme: Projektleiter: E. Newson Aerosol Research at the Jungfraujoch) Partial Oxidation, Preferential Oxidation ofHydro- carbons/Methanol NATIONALFONDS Alcoa, USA, Johnson Matthey UK, Haldor Topsoe A/S, DK, Nucat Ltd., UK, Süd Chemie AG, Germany Projektleiter: U. Baltensperger Sources, Formation and Composition of Particulate Projektleiter: P. Novak Organic Carbon in the Lower Troposphere Entwicklung eines Batterieseparators auf Basis der keramischen Membranfolie der CREAVIS; Projektleiter: U. Krähenbühl*, R.T.W. Siegwolf CREAVIS Gesellschaft für Technologie und Reconstruction of Anthropogenic Pollution by S- and Innovation mbH, Marl, Germany N-Bearing Compounds: Isotopic Signatures Since the Turn of the Century through Study of Environmental Projektleiter: P. Novák Archives Entwicklung und Optimierung einer negativen Elektrode für Lithium-Ionen-Batterien * University of Bern lonity AG, Kamenz, Germany Projekleiter: S. Kypreos Projektleiter: P. Novák NCCR-Climate, WP4: Climate Risk Assessment Elektrochemische Charakterisierung von Oxiden für Projektleiter: Ch. Ludwig, S. Hellweg*, S. Stucki Lithium-Ionen-Batterien Waste Book Partners from Industry, Consulting Firms, and Ferro GmbH (ex dmc2 AG), Frankfurt/Main, Germany Universities * ETH Zürich Projektleiter: P. Novák Behandlung der Graphite für die negative Elektrode Projektleiter: H. Lutz, Ch. Ludwig, S. Biollaz, S. Stucki der Lithium-Ionentransferbatterie PECK-Techtransfer: Filteraschebehandlung TIMCAL SA, Bodio Partners from CT Umwelttechnik, ETH Zürich, Projektleiter: G.G. Scherer University of Bern, Membranen für die Direkt Methanol Brennstoffzelle Zürich University of Applied Sciences Winterthur Automobilindustrie Projektleiter: A.F. Neftel*, A.S.H. Prévôt Projektleiter: S. Stucki COCA (Characterization of Organic Compounds in the Auswahl von Resh-Verwertungsverfahren (ARVE) Atmosphere) Verband Schweizerischer Automobilimporteure (VSAI) * IUL Liebefeld, Bern Interessengemeinschaft für die umweltgerechte Entsorgung von Altautos Projektleiter: P. Novák Synthesis and Characterization of Advanced KTI Electroactive Materials for Electrodes of Rechargeable Lithium-Ion Batteries Projektleiter: J. Keller Influence of the Transboundary Pollution on the Air Projektleiter: A.S.H. Prévôt Quality in Switzerland PROSMOG (Proton Transfer Mass Spectrometer for (Contribution to the EUROTRAC-2 Subproject Measurements of Organic Compounds with High Time GLOREAM) Resolution in Smog Chamber Experiments) 152 Projektleiter: P. Schleppi*, R.T.W. Siegwolf Prof. Dr. R. Palumbo IRISALP (Isotope S15N and Research on Impacts of Thermodynamics II Nitrogen Deposition in Subalpine Ecosystems) Mechanical Engineering Department * WSL Birmensdorf Valparaiso University, IN, USA August-December, 2001. Projektleiter: A. Wokaun Co-Projektleiter: T. Lippert Prof. Dr. R. Palumbo Laser Ablation as a Tool for Trace Analysis and High Mechanical Measurements Resolution Material Transfer Mechanical Engineering Department Valparaiso University, IN, USA SWISSCOM August-December, 2001. Projektleiter: E. Weingartner Prof. Dr. R. Palumbo Swisscom Forum Senior Design Project I Mechanical Engineering Department UNIVERSITIES Valparaiso University, IN, USA August-December, 2001. Projektleiter: H. Armbruster, S. Stucki On-Board Production of Ethers Dr. R.T.W. Siegwolf Combustion Engine Research Center, Chalmers Einsatz stabiler Isotope in der Oekologie und University, Göteborg, Sweden Physiologie der Pflanzen Lecture at the University of Basel, SS 2001. Projektleiter: J. Keller Retrieval of Biogeophysical and Biogeochemical Dr. R.T.W. Siegwolf Parameters Using Hyperspectral Remote Sensing Einführungspraktikum zur Vorlesung Einsatz stabiler Data Isotope in der Oekologie Remote Sensing Laboratories (RSL), Lecture at the University of Basel, SS 2001. University of Zürich Prof. Dr. A. Steinfeld Projektleiter: M. Koebel Energieübertragung durch Wärmestrahlung Messgerät für gasförmiges Ammoniak und ETH Zürich, WS 2001/2002. Isocyansäure University of Kaiserslautern, Germany Prof. Dr. A. Steinfeld, Dr. J. Gass, V. Dorer Technik erneuerbarer Energien - Teil 1 Projektleiter: J. ter Meulen*, R. Baert**, T. Gerber ETH Zürich, SS 2001. Modelling of Combustion Processes in a Direct Injected Diesel Engine Prof. Dr. A. Steinfeld, Prof. Dr. A. Wokaun, * University of Nijmegen, The Netherlands Prof. Dr. G. Yadigaroglu, Prof. Dr. W. Kroeger, ** University of Eindhoven, The Netherlands Prof. Dr. E. Jochem, Prof. Dr. M. Filippini Vertiefungseinführung in Energietechnik: TEACHING ACTIVITIES Nachhaltige Energienutzung ETH Zürich, WS 2001/2002. University Level Teaching Prof. Dr. A. Wokaun PD Dr. U. Baltensperger, Prof. Dr. H. Burtscher, Erneuerbare Energien Prof. Dr. T. Peter ETH Zürich, SS 2001. Aerosole I ETH Zürich, WS 2001/2002. Prof. Dr. A. Wokaun, Dr. J. Gass Technik erneuerbarer Energien, Teil 2 PD Dr. U. Baltensperger, Prof. Dr. H. Burtscher, ETH Zürich, WS 2001/2002. Prof. Dr. T. Peter Aerosole II Lecture Courses at Other Schools ETH Zürich, SS 2001. Dr. F. Gassmann Prof. Dr. K. Boulouchos Umweltethik Verbrennung: Grundlagen und Anwendungen FH Aargau, Brugg-Windisch ETH Zürich, SS 2001. Interdisziplinärer Wahlfachkurs, WS 2000/2001. Prof. Dr. K. Boulouchos Gemischbildung und Energieumsetzung in Verbrennungskranmaschinen ETH Zürich, WS 2001/2002. 153 Contributions to Courses at Universities, FHL and Dr. F. Gassmann Other Institutes Komplexität — Vom linearen zum zirkulären Denken Vorlesung für Baumanager der FH Aargau, Windisch, Dr. O. Bahn May 28, 2001. Applications de Systèmes d'Information et d'Aide à la Décision Environnementale à l'Institut Paul Scherrer Dr. F. Gassmann Formation Continue en 'Gestion de l'Environnement et Von den Grenzen des Wachstums zu einer Entreprise', University of Geneva, October 11-12, nachhaltigen Entwicklung 2001. Grundkurs Ökologie, HTA Luzern, Horw, October 15, 2001. Dr. O. Bahn Modèles E3 (Économie - Énergie - Environnement): Dr. P. Griebel Application au Protocole de Kyoto Verbrennung in Fluggasturbinen Ingénierie et Gestion de l'Energie, École Nationale Beitrag zur Vorlesung "Gemischbildung und Energie• Supérieure des Mines de Paris, France, March 20, umsetzung in Verbrennungskraftmaschinen", ETH 2001. Zürich, January 2001. Dr. S. Biollaz Prof. Dr. W. Kröger, Dr. W. Durisch Herstellung von Biotreibstoffen Einführung in energiewandelnde Systeme mit Blick Beitrag zur Vorlesung "Instationäre Arbeitsprozesse auf sicherheitsrelevante Aspekte und Verbrennungstechnik", Prof. Dr. M. Eberle, (Kernenergie und Photovoltaik als Beispiele) ETH Zürich, June 14, 2001. Nachdiplomkurs Risiko und Sicherheit, ETH/HSG/EPFL, 4. Kurs 2000/2001, Modul G1, Dr. S. Biollaz Kandersteg, March 18-21, 2001. Biomasse Beitrag zur Vorlesung "Technik erneuerbarer Dr. O. Haas Energien 2", Prof. Dr. A. Wokaun, ETH Zürich, Elektrochemische Energiespeicherung und December 11, 2001. Umwandlung Beitrag zur Vorlesung "Physikalisch-chemische Dr. F.N. Büchi Grundlagen der Energienutzung" Brennstoffzellenstapel und System Prof. A. Wokaun, ETH Zürich, February 6, 2001. Beitrag zur Vorlesung "Technik erneuerbarer Energien 2", Prof. A. Wokaun, ETH Zürich, January 23, 2001. Dr. T. Lippert Photochemistry Dr. W. Durisch Beitrag zur Vorlesung "Physikalisch-chemische Photovoltaik - Strom aus Sonnenlicht Grundlagen der Energienutzung" Energietechnische Aus- und Weiterbildung für Prof. A. Wokaun, ETH Zürich, May 22, 2001. nichttechnische Fach- und Führungskräfte, ABB Technikerschule, Baden, May 30, 2001. PD Dr. P. Novák Elektrochemische Energiespeicherung Dr. W. Durisch 1. Grundlagen Photovoltaik-Praktikum 2. Batterien Hochschule für Technik + Architektur, HTA Luzern, Beitrag zur Vorlesung "Technik erneuerbarer July 10, 2001. Energien", Prof. Dr. A. Wokaun, ETH Zürich, January 9 + 16, 2001. Dr. F. Gassmann Treibhauseffekt und IPCC-Bericht 2001 Dr. G.G. Scherer Schweiz. Drogistenschule, Neuenburg, May 10, 2001. Brennstoffzellen Beitrag zur Vorlesung "Technik erneuerbarer Dr. F. Gassmann Energien", Prof. A. Wokaun, ETH Zürich, Wichtigste Aussagen des IPCC-Berichtes 2001 zum January 23 and 30, 2001. Stand des Treibhauseffektes ETHZ, Beitrag zur Vorlesung „Ökologische Aspekte Dr. R.T.W. Siegwolf der individuellen Mobilität", Zürich, May 10, 2001. Stable Isotopes in Community and Ecosystem Studies Dr. F. Gassmann Spring School, Èvora, Portugal, EU-Programme C02-Emissionen und Klimaproblematik LINKECOL: Linking Community and Ecosystem ETHZ, Beitrag zur Vorlesung „Erneuerbare Energien" Ecology, March 27 - April 8, 2001. Prof. A. Wokaun, ETH Zürich, June 28, 2001. Dr. M. Sturzenegger Dr. F. Gassmann Produktion von solaren Brennstoffen und Materialien Technikethik in den Unterricht einbauen: Vom linearen Beitrag zur 5. Sommerschule des Schwerpunktes 5 zum zirkulären Denken, Komplexität der AG Solar NRW: Nutzung des Sonnenlichts in Didaktischer Weiterbildungszyklus 2000/01 der FH Chemie und Verfahrenstechnik Freiburg, Windisch, January 19, 2001. Bonn, Germany, August 20-23, 2001. 154 PUBLICATIONS K. Baumann*, H. Maurer*, G. Rau*, M. Piringer*, U. Pechinger*, A. Prévôt, M. Furger, B. Neininger**, Books U. Pellegrini*** The Influence of South Foehn on the Ozone U. Baltensperger, E. Weingartner, H. Burtscher*, Distribution in the Alpine Rhine Valley - Results from J. Keskinen** the MAP Field Phase Aerosol Measurement, Principles, Techniques, and Atmos. Environ. 35, 6379-6390 (2001). Applications. Dynamic Mass and Surface Area * ZAMG, Vienna, Austria Measurements ** MetAir AG, lllnau Wiley-lnterscience, Second Edition, 387-418 (2001). *** CESI Spa, Segrate, Italy * Fachhochschule Aargau, Brugg-Windisch ** University of Tampere, Finland I. Baur*, Chr. Ludwig, CA. Johnson* The Leaching Behavior of Cement Stabilized Air F.N. Büchi, G.G. Scherer, A. Wokaun Pollution Control Residues: A Comparison of Field Proceedings of the „1st European Polymer Electrolyte and Laboratory Investigations Fuel Cell Forum" Environ. Sei. Technol. 35, 2817-2822 (2001). Luzern, July 2-6, 2001. * Swiss Federal Institut for Environmental Science and Technology (EAWAG), Dübendorf A. Steinfeld, R. Palumbo Solar Thermochemical Process Technology P. Beaud, H.-M. Frey*, T. Lang**, M. Motzkus** Encyclopedia of Physical Science and Technology Flame Thermometry by Femtosecond CARS R. A. Meyers Ed., Academic Press, ISBN 0-12- Chem. Phys. Lett. 344, 405-412 (2001). 227410-5, 15, 237-256 (2001). * now University of Berne ** Max Planck Institute, Garching, Germany Peer Reviewed Papers S. Biollaz, M. Sturzenegger, S. Stucki E. Ammann*, C. Beuret**, P.-F. Indermühle**, R. Kötz, REDOX Process for the Production of Clean N.F. de Rooij**, H. Siegenthaler* Hydrogen from Biomass Local pH-controlled Reactivity Investigations by Thin- Progress in Thermochemical Biomass Conversion 1, Layer Scanning Tunneling Microscopy Bridgewater A.V (Ed.), Blackwell Science, 388-395 Electrochim. Acta 47, 327-334 (2001). (2001). * University of Bern ** University of Neuchâtel S. Biollaz, Th. Nussbaumer, CH. Onder Measuring and Modelling the Gas Residence Time S. Andreani-Aksoyoglu, C.-H. Lu*, J. Keller, Distribution in Biomass Furnaces A.S.H. Prévôt, J.S. Chang* Progress in Thermochemical Biomass Conversion 1, Variability of Indicator Values for Ozone Production Bridgewater A.V (Ed.), Blackwell Science, 573-584 Sensitivity: a Model Study in Switzerland and San (2001). Joaquin Valley (California) Atmos. Environ. 35, 5593-5603 (2001). F.N. Büchi, G.G. Scherer * University of New York at Albany, USA Investigation of the Transversal Water Profile in Nafion Membranes in Polymer Electrolyte Fuel Cells F. Arens, L. Gutzwiller, U. Baltensperger, J. Electrochem. Soc. 148, A183-A188 (2001). H.W. Gaeggeler, M. Ammann Heterogeneous Reaction of N02 on Diesel Soot M. Bundt*, M. Jäggi, P. Blaser*, R. Siegwolf, Particles F. Hagedorn* Carbon and Nitrogen Dynamics in Preferential Flow Environ. Sei. Technol. 35, 2191-2199 (2001). Paths and Matrix of a Forest Soil Soil Sei. Soc. of America J. 65, 1529-1538 (2001). O. Bahn * WSL Birmensdorf Combining Policy Instruments to Curb Greenhouse Gas Emissions H. Burtscher*, U. Baltensperger, N. Bukowiecki, Eur. Environ. 11, 163-171 (2001). P. Cohn**, C. Hüglin***, M. Mohr***, U. Matter, O. Bahn, L. Barreto, S. Kypreos S. Nyeki, V. Schmatloch***, N. Streit, E. Weingartner Modelling and Assessing Inter-Regional Trade of C02 Separation of Volatile and Non-Volatile Aerosol Emission Reduction Units Fractions by Thermodesorption: Instrumental Environ. Modeling and Assessment 6,173-182 Development and Applications (2001). J. Aerosol Sei. 32, 427-442 (2001). * Fachhochschule Aargau, Windisch ** ETH Zürich *** EM PA Dübendorf 155 C. David, J. Wei, T. Lippert, A. Wokaun M. Furger, P. Drobinski*, A.S.H. Prévôt, R.O. Weber, Diffractive Grey-Tone Phase Masks for Laser Ablation W.K. Graber, B. Neininger** Lithography Comparison of Horizontal and Vertical Scintillometer Microelectronic Engineering 57-58, 453-460 (2001). Crosswinds During Strong Foehn with Lidar and Aircraft Measurements E. Deiss, D. Häringer, O. Haas, P. Novák J. Atmos. and Oceanic Technol. 18, 1975-1988 Modeling of the Charge-Discharge Dynamics of (2001). Lithium Manganese Oxide Electrodes * Ecole Polytechnique, Palaiseau, France ITE Letters on Batteries 2, 15-19 (2001). ** MetAir AG, lllnau E. Deiss, D. Häringer, P. Novák, O.Haas R. Gehrig*, Ch. Hueglin*, W. Devos*, P. Hofer*, Modeling of the Charge-Discharge Dynamics of J. Kobler*, W.A. Stahel**, U. Baltensperger, Lithium Manganese Oxide Electrodes for Lithium-Ion Ch. Monn** Batteries Contribution of Road Traffic to Ambient Fine Particle Electrochim. Acta 46, 4185-4196 (2001). Concentrations (PM10) in Switzerland Int. J. Vehicle Design 27, 55-64 (2001). J. Dommen, A.S.H. Prévôt, I. Polo, B. Neininger*, * EM PA Dübendorf M. Baumle* ** ETH Zürich Airborne NMHC Measurements Under Various Pollution Conditions K. Geissler, E. Newson, F. Vogel, T.-B. Truong, Int. J. Vehicle Design 27, 217-227 (2001). P. Hottinger, A. Wokaun * MetAir AG, lllnau Autothermal Methanol Reforming for Hydrogen Production in Fuel Cell Applications J.-F. Drillet*, F. Holzer, T. Kallis**, S. Müller, Phys. Chem. Chem. Phys. 3, 289-293 (2001). V.M. Schmidt* Influence ofC02 on the Stability of Bifunctional T. Gradinger, A. Inauen, R. Bombach, B. Käppeli, Oxygen Electrodes for Rechargeable Zinc/Air W. Hubschmid, K. Boulouchos Batteries and Study of Different C02 Filter Materials Liquid-Fuel/Air Premixing in Gas-Turbine Combustors: Phys. Chem. Chem. Phys. 3, 368-371 (2001). Experiment and Numerical Simulation * University of Applied Sciences, Mannheim, Comb. Flame 124, 422-443 (2001). Germany ** Competence Centre for Zero Emission Commerc. L. Gubler*, G.G. Scherer, A. Wokaun Vehicles, Daimler Chrysler AG, Germany Methods for the Quantitative Characterization of the CO Tolerance in a One-Dimensional Polymer W. Durisch, J.-C. Mayor, F. von Roth, B. Bitnar, Electrolyte Fuel Cell H.R. Tschudi Chem. Eng. Technol. 24, 59-67 (2001). Thermophotovoltaische Erzeugung von Wärme und * now Johnson Matthey, UK Strom gwa 81, 355-364 (2001). L. Gubler*, G.G. Scherer, A. Wokaun Effects of Cell and Electrode Design on the CO- S.H. Ehrman, M. Schwikowski, U. Baltensperger, Tolerance of Polymer Electrolyte Fuel Cells H.W. Gaeggeler Phys. Chem. Chem. Phys. 3, 325-329 (2001). Sampling and Chemical Analysis of Ice Crystals as a * now Johnson Matthey, UK Function of Size Atmos. Environ. 35, 5371-5376 (2001). F. Guthe*, M. Tulej, M.V. Pachkov*, J.P. Maier* Photodetachment Spectrum of l-C3H2~ Anion: the Role K. Eleftheriadis*, S. Nyeki, K. Torseth**, I. Colbeck*** of Dipole Bound States for Electron Attachment in Black Carbon and Ionic Species in the Arctic Aerosol Interstellar Clouds Mem. Nat. Inst. Polar Res. 54, 91-99 (2001). Astrophys. J. 555, 466-471 (2001). * NCSR Demokritos, Greece * University of Basel ** NILU, Norway *** University of Essex, England F. Hagedorn*, S. Maurer*, P. Egli*, P. Blaser*, J.B. Bucher*, R. Siegwolf J. Feader*, I. Pinkas*, G. Knopp, Y. Prior*, D. Tannor* Carbon Sequestration in Forest Soils - Effects of Soil Vibrational Polarization Beats in Femto Second Type, Atmospheric C02 Enrichment and N Deposition CARS: A Signature of Dissociative Pump - Dump - Eur. J. Soil Sei. 52, 619-629 (2001). Pump Wavepacket Dynamics * WSL, Birmensdorf J. Chem. Phys. 115, 8440-8454 (2001). * Weizmann Institute of Science, Israel B. Hemmerling, P.P. Radi, A. Stampanoni, A.P. Kouzov, D. Kozlov T. Frey, E. Steiner, D. Wuillemin, M. Sturzenegger Novel Non-Linear Techniques for Diagnostics: Laser- TREMPER — A Versatile Tool for High-Temperature Induced Gratings and Two-Color Four-Wave Mixing Chemical Reactivity Studies Under Concentrated CR. Acad. Sei. IV-Phys. 2, 1001-1012 (2001). Solar Radiation J. Sol. Energy Eng. 123, 147-152 (2001). 156 B. Hemmerling, A. Stampanoni S. Kräupl, A. Steinfeld Investigation of Soot by Two-Colour Four-Wave Experimental Investigation of a Vortex Flow Solar Mixing Chemical Reactor for the Combined ZnO-Reduction Chemosphere 42, 647-653 (2001). and CH4 Reforming J. Solar Energy Eng. 123, 237-243 (2001). D. Hirsch*, M. Epstein**, A. Steinfeld The Solar Thermal Decarbonization of Natural Gas M. Kraus, B. Eliasson*, U. Kogelschatz*, A. Wokaun Int. J. Hydrogen Energy 26, 1023-1033 (2001). C02 Reforming of Methane by the Combination of * ETH Zürich Dielectric-Barrier Discharges and Catalysis ** Weizmann Institute of Science, Rehovot, Israel Phys. Chem. Chem. Phys. 3, 294-300 (2001). * ABB Baden F. Joho, B. Rykart, A. Blome, P. Novák, H. Wilhelm* M.E. Spahr* Z. Krivácsy*, A. Gelencsér*, G. Kiss*, E. Meszaros*, Relation Between Surface Properties, Pore Structure A. Molnár*, A. Hoffer, T. Mészáros*, Z. Sárvári*, and First-Cycle Charge Loss of Graphite as Negative D. Temesi*, B. Varga*, U. Baltensperger, S. Nyeki, Electrode in Lithium-Ion Batteries E. Weingartner J. Power Sources 97-98, 78-82 (2001). Study on the Chemical Character of Water Soluble * TIMCAL SA, Bodio Organic Compounds in Fine Atmospheric Aerosol at the Jungfraujoch M. Kasper*, U. Matter*, H. Burtscher**, N. Bukowiecki, J. Atmos. Chem. 39, 235-259 (2001). A. Mayer*** * University of Veszprém, Hungary NanoMet, a New Instrumentation for On-line Size- and Substance-Specific Particle Emission Analysis Z. Krivácsy*, A. Hoffer*, Zs. Sárvári*, D. Temesi*, SAE Technical Paper Series 2001-01-0216 (2001). U. Baltensperger, S. Nyeki, E. Weingartner, * Matter Engineering AG, Wohlen S. Kleefeld**, S.G. Jennings** ** FH Aargau, BruggAA/indisch Role of Organic and Black Carbon in the Chemical *** Technik Thermische Maschinen, Niederrohrdorf Composition of Atmospheric Aerosol at European Background Sites M. Koebel, M. Elsener, G. Madia Atmos. Environ. 35, 6231-6244 (2001). Reaction Pathways in the Selective Catalytic * University of Veszprém, Hungary Reduction Process with NO and N02 at Low ** University of Ireland, Galway, Ireland Temperatures Int. Eng. Chem. Res. 40, 52-59 (2001). T. Lang*, M. Motzkus*, H.M. Frey**, P. Beaud High Resolution Femtosecond CARS: Determination M. Koebel, M. Elsener, G. Madia of Rotational Constants, Molecular Anharmonicity, Entstickung von Dieselabgasen mit Harnstoff-SCR bei Collisional Lineshifts, and Temperature tiefen Temperaturen J. Chem. Phys. 115, 5418-5426 (2001). Motortechn. Zeitschrift 62, 166-175 (2001). * Max Planck Institute, Garching, Germany ** now University of Bern M. Koebel, M. Elsener, G. Madia Recent Advances in the Development of Urea-SCR M. Lanz, P. Novák for Automotive Applications DEMS Study of Gas Evolution at Thick Graphite SAE Technical Paper Series 2001-01-3625 (2001). Electrodes for Lithium-Ion Batteries: The Effect of y-Butyrolactone R. Kostecki*, B. Schnyder, D. Alliata, X. Song*, J. Power Sources 102, 278-283 (2001). K. Kinoshita*, R. Kötz Surface Studies of Carbon Films from Pyrolyzed M. Lanz, E. Lehmann, R. Imhof*, I. Exnar*, P. Novák Photoresist In-Situ Neutron Radiography of Lithium-Ion Batteries Thin Solid Films 396, 36-43 (2001). during Charge/Discharge Cycling * Lawrence Berkeley Nat. Lab. Berkeley, CA, USA J. Power Sources 101, 177-181 (2001). A.P. Kouzov*, P.P. Radi * Renata AG, Itingen Collision-Induced Resonances in Two-Color Resonant Four-Wave Mixing Spectra T. Lippert, A. Wokaun Phys. Rev. 630/1 (1) January (2001). Laser Processing of Novel Functional Materials * on leave from University of Saint Petersburg, Chimia 55, 783-786 (2001). Russia S. Kräupl, A. Steinfeld Pulsed Gas Feeding for Stoichiometric Operation of a Gas-Solid Vortex Flow Solar Chemical Reactor J. Solar Energy Eng. 123, 133-137 (2001). 157 T. Lippert, C. David, J.T. Dickinson*, M. Hauer, A. Nickel*, O. Pelz*, D. Hahn**, M. Saurer, U. Kogelschatz**, S.C. Langford*, O. Nuyken***, R. Siegwolf, J. Zeyer* C. Phipps****, J. Robert***, A. Wokaun Effect of Inoculation and Leaf Litter Amendment on Structure Property Relations of Photoreactive Establishment of Nodule-Forming Frankia Polymers Designed for Laser Ablation Populations in Soil J. Photochem. Photobiol. A: Chem. 145, 145-157 Appl. and Environ. Microbiology 67, 2603-2609 (2001). (2001). * Washington State University, USA * Institute of Terrestrial Ecology, ETHZ, Schlieren ** ABB Baden ** Institute of Technology, Newark, New Jersey, *** TU Munich, Germany USA **** Photonic Associates, Santa Fe, USA P.A. Nikiaus*, E. Glöckner*, R. Siegwolf, Ch. Körner* T. Lippert, C. David, M. Hauer, A. Wokaun, J. Robert*, Carbon Allocation in Calcareous Grassland Under 13 O. Nuyken*, C. Phipps** Elevated C02: A Combined C Pulse Labeling/Soil Polymers for UV and Near-IR Irradiation Physical Fractionation Study J. Photochem. Photobiol. A: Chem. 145, 87-92 (2001). Functional Ecol. 15, 43-50 (2001). * TU Munich, Germany * Institute of Botany, Basel ** Photonic Associates, Santa Fe, USA P.A. Niklaus*, M. Wolfender*, R. Siegwolf, T. Lippert, C. David, M. Hauer, C. Phipps*, A. Wokaun Ch. Körner* Tailor-Made Polymers for Laser Applications Effects of Six Years Atmospheric C02 Enrichment on Rev. Laser Engineering 29, 734-738 (2001). Plant, Soil, and Microbial Cofa Calcareous * Photonic Associates, Santa Fe, USA Grassland Plant and Soil 223, 189-202 (2001). Chr. Ludwig, H. Lutz, J. Wochele, S. Stucki * Institute of Botany, Basel Studying the Evaporation Behavior of Heavy Metals by Thermo-Desorption Spectrometry P. Novák, F. Joho, M. Lanz, B. Rykart, J.-C. Panitz*, Fres. J. Anal. Chem. 371, 1057-1062 (2001). D. Alliata**, R. Kötz, O. Haas The Complex Electrochemistry of Graphite Electrodes J. Mantzaras, C. Appel, P. Benz in Lithium-Ion Batteries Catalytic Combustion of Methane/Air Mixtures over J. Power Sources 97-98, 39-46 (2001). Platinum: Homogeneous Ignition Distances in * now Chemetall GmbH, Frankfurt am Main, Channel Flow Configurations Germany Proc. Combustion Institute 28, 1349-1357 (2001). ** now I.N.F.M. Dipart. Scienze Ambientali, Università della Tuscia, Viterbo, Italy P. Mizsey, E. Newson, T.B. Truong, P. Hottinger The Kinetics of Methanol Decomposition: a Part of E. Ortelli, F. Geiger, T. Lippert, A. Wokaun Autothermal Partial Oxidation to Produce Hydrogen Pyrolysis ofKapton®: An in situ DRIFT Study for Fuel Cells Appl. Spectrosc. 55, 412-419 (2001). Applied Catalysis A: General 213, 233-237 (2001). E. Ortelli, J. Wambach, A. Wokaun Methanol Synthesis Reactions over a CuZr Based P. Mizsey, E. Newson Catalyst Investigated Using Periodic Variations of Comparison of Different Vehicle Power Trains Reactant Concentrations J. Power Sources 102, 205-209 (2001). Appl. Catal. A: General 216, 227-241 (2001). S. Möller*, R. Palumbo Solar Thermal Decomposition Kinetics of ZnO in the M.V. Pachkov*, T. Pino*, M. Tulej, J.P. Maier* Temperature Range 1950-2400 K Electronic Transition of the C3H~ in the Vicinity of the Chem. Eng. Sei. 56, 4505-4515 (2001). Lowest Photodetachment Threshold * now DLR Stuttgart, Germany Mol. Phys. 99, 1397-1405 (2001). * University of Basel S. Möller*, R. Palumbo The Development of a Solar Chemical Reactor for the J.-C. Panitz*, P. Novák, O. Haas Direct Thermal Dissociation of Zinc Oxide Raman Microscopy Applied to Rechargeable Lithium- J. Solar Energy Eng. 123, 83-90 (2001). Ion Cells-Steps Toward in-Situ Raman Imaging with * now DLR Stuttgart, Germany Increased Optical Efficiency Appl. Spectroscopy 55, 1131-1137 (2001). D.S. Moore*, KT. Gahagan*, J.H. Reho*, D.J. Funk*, * now Chemetall GmbH, Frankfurt am Main, S.J. Buelow*, R.L. Rabie*, T. Lippert Germany Ultrafast Non-Linear Optical Method for Generation of Flat-Top Shocks Appl. Phys. Lett. 78, 40-42 (2001). * Los Alamos National Laboratory, USA 158 I. Pinkas*, G. Knopp, Y. Prior* R. Siegwolf, R. Matyssek*, M. Saurer, S. Maurer, Preparation and Monitoring of High Ground State M.S. Günthardt-Georg**, P. Schmutz**, J.B. Bucher** Vibrational Wavepackets by Femtosecond Coherent Stable Isotope Analysis Reveals Differential Effects of Anti-Stokes Raman Scattering Soil Nitrogen and Nitrogen Dioxide on the Water use J. Chem. Phys. 115, 236-244 (2001). Efficiency in Hybrid Poplar Leaves * Weizmann Institute of Science, Israel New Phytologist 149, 233-246 (2001). * Maximilians University of Munich, Germany M. Saurer, R.T.W. Siegwolf, Y. Scheidegger ** WSL Birmensdorf Canopy Gradients in Delta 180 of Organic Matter as Ecophysiological Tool M.E. Spahr*, H. Wilhelm, F. Joho, P. Novak Isotopes in Environmental and Health Studies 37, Structure, Texture, and Surface Morphology 13-14(2001). Modifications of Highly Crystalline Graphite and the Consequences for its Electrochemical Lithium Insertion Behavior T. Schildhauer, E. Newson, St. Müller The Equilibrium Constant for the Methylcyclohexane- ITE Letters on Batteries, New Technologies & Toluene System Medicine 2, 370-375 (2001). J. Catal. 198, 355-388 (2001). * TIMCAL SA, Bodio H. Schmid', L. Laskus", H.J. Abraham'", R. Stöckle*, P. Setz*, V. Decken*, T. Lippert, A. Wokaun, R. Zenobi* U. Baltensperger, V. Lavanchy, M. Bizjaklv, Nanoscale Atmospheric Pressure Laser Ablation- P. Burbav, H. Cachiervl, D. Crowv", J. Chowv", Mass Spectrometry T. Gnaukvl", A. Evenlx, H.M. ten Brinklx, Anal. Chem. 73, 1399-1402 (2001). K.-P. Giesenx, R. Hitzenberger*, C. Hueglinx", * ETH Zürich W. Maenhautxl", C. Pioxlv, A. Carvalhoxl , J.-P. Putaud™, D. Toom-Sauntry™, H. Puxbaum' R.P.W.J. Struis, C. von Scala, S. Stucki, R. Prins* Results of the 'Carbon Conference' International Gasification Reactivity of Charcoal with C02 at Aerosol Carbon Round Robin Test Stage I Atmos. Environ. 35, 2111-2121 (2001). Elevated Conversion Levels ' Institute of Analytical Chemistry,Vienna, Austria Progress in Thermochemical Biomass Conversion 1, " Umweltbundesamt, Institute of Water, Soil and Bridgwater A.V. (Ed.), Air Hygiene, Berlin, Germany Blackwell Science, 73-91 (2001). '" Ministry of Urban Development, Berlin, Germany * ETH Zürich lv National Institute of Chemistry, Ljubljana, Slovenia R.P.W.J. Struis, S. Stucki v Institut für Spektrochemie und angewandte Verification of the Membrane Reactor Concept for the Spektroskopie, Dortmund, Germany Methanol Synthesis. Vl Laboratoire des Sciences du Climate de de Appl. Cat. A: General 216, 117-129 (2001). l'Environment, Gif sur Yvette, France v" Desert Research Institute, Reno, USA M. Tulej, F. Güthe*, M.V. Pachkov*, K. Tikhomirov*, Vl" Institute for Tropospheric Research, M. Jungen*, J.P. Maier* Leipzig, Germany Feshbach States of Propadienylidene Anion C3H2" lx ECN - Energy Research Foundation, Petten, Phys. Chem. Chem. Phys. 3, 4674-4678 (2001). The Netherlands * University of Basel x Niedersächsisches Landesamt für Ökologie, Hannover, Germany A. Thielmann*, A.S.H. Prévôt, F.C. Gruebler*, Xl Institute für Experimentalphysik, Vienna, Austria J. Staehelin* x" Abteilung Luftfremdstoffe/Umwelttechnik, EMPA, Empirical Ozone Isopleths as a Tool to Identify Ozone Dübendorf Production Regimes Xl" Institute for Nuclear Sciences, Gent, Belgium Geophys. Res. Lett. 28, 2369-2372 (2001). XIV University of Aveiro, Aveiro, Protugal * ETH Zürich ™ Joint Research Centre Ispra, Environment Institute, Ispra, Italy H.-R. Tschudi, G. Morian ^ Remote Regions Atmospheric Chemistry Pyrometric Temperature Measurements in Solar Laboratory, Downsview, ON, Canada Furnaces B. Schnyder, D. Alliata*, R. Kötz, H. Siegenthaler** J. Sol. Energy Eng. 123, 164-170 (2001). Electrochemical Intercalation of Perchlorate Ions in HOPG-.A SPM/LFM And XPS Study R.O. Weber, M. Furger Appl. Surface Science 173, 221-232 (2001). Climatology of Near-Surface Wind Patterns over * now I.N.F.M. Dipart. Scienze Ambientali, Université Switzerland della Tuscia, Viterbo, Italy Int. J. Climatology 21, 809-827 (2001). ** University of Bern 159 R.O. Weber, P. Talkner U. Baltensperger Spectra and Correlations of Climate Data from The Organic Component of the Atmospheric Aerosol: Days to Decades Facts and Fiction J. Geophys. Res. 106, 20131-20144 (2001). Proc. European Aerosol Conference 2001, Leipzig, Germany J. Wei, T. Lippert, N. Hoogen*, O. Nuyken*, A. Wokaun J. Aerosol Sei. 32, Supplement 1, S901-S902 (2001). Novel Laser Ablation Resists for Excimer Laser Ablation Lithography. Influence of Photochemical U. Baltensperger Properties on Ablation The Art of Aerosol Measurement and Modelling within J. Phys. Chem. B 105, 1267-1275 (2001). AEROSOL * TU Munich, Germany Proc. Eurotrac-2 Symposium 2000, Garmisch- Partenkirchen, Germany A. Weidenkaff*, A. Relier*, A. Steinfeld Springer-Verlag Berlin, Heidelberg, Germany, 39-44 Solar Production of Zinc from Zinc Silicate Ore (2001). Willemite B. Bitnar, W. Durisch, D. Grützmacher, J.-C. Mayor, J. Solar Energy Eng. 123, 98-101 (2001). Ch. Müller, F. von Roth, J.A. Anna Selvan, H. Sigg, * University of Augsburg, Germany H.R. Tschudi, J. Gobrecht A TPV System with Silicon Photocells and a Selective Other Papers Emitter Conference Record of the 28th IEEE Photovoltaic S. Andreani-Aksoyoglu, J. Keller, A.S.H. Prévôt Specialists Conference, Anchorage, Alaska, Applicability of Indicator-Based Approach to Assess September 15-22, 2000, 1218-1221 (2001). Ozone Sensitivities: A Model Study in Switzerland Proc. 2nd International Conference on Air Pollution S. Biollaz, R. Bunge, M. Schaub, H. Künstler Modelling and Simulation, Champs-sur-Marne, France Better Quality of MSW Incinerator Residues for Lower Springer Geosciences (2001). Cost Incineration 2001, 3rd International Symposium on S. Andreani-Aksoyoglu, J. Keller, J. Dommen, Incineration and Flue Gas Treatment Technologies A.S.H.Prévôt Brussels, July 2-4, 2001. Modelling of Air Quality with CAMx: A Case Study in Switzerland F.N. Büchi Proc. Air Quality Management at Urban, Regional and Wasserstoff für's Handy Global Scales, Istanbul, Turkey Spektrum der Wissenschaft 2001, July, 48-51 (2001). Istanbul Technical University 1, 306-313 (2001). N. Bukowiecki, I. Polo, A.S.H.Prévôt, E. Weingartner, S. Andreani-Aksoyoglu, J. Keller U. Baltensperger Comparison of Model Results for Winter and Summer Atmospheric Aerosol and Gaseous Compounds in the Air Quality Zurich Area: A One-Year Study with a Mobile Proc. Eurotrac-2 Symposium 2000, Garmisch- Laboratory Partenkirchen Proc. ISAM 13th International Congress, Interlaken, Springer-Verlag Berlin, Heidelberg, Germany CD- Switzerland ROM (2001). J. Aerosol in Medicine 14, 3 420 (2001). B. Andreaus, A. McEvoy*, G.G. Scherer N. Bukowiecki, I. Polo, A.S.H. Prévôt, E. Weingartner, Impedance Response of Polymer Electrolyte Fuel U. Baltensperger Cells at High Current Densities Seasonal and Spatial Distribution of Atmospheric Proc. 1st European PEFC Forum, Eds. F.N. Biichi, Aerosols and Gaseous Compounds in the Zurich Area G.G. Scherer, A. Wokaun, Luzern, Switzerland, Measured by a Mobile Laboratory 135-141, July 2001. Proc. European Aerosol Conference (EAC) 2001, * EPF Lausanne Leipzig, Germany J. Aerosol Sei. 32, Supplement 1, S185-S186 (2001). C. Appel, J. Mantzaras, R. Schären, R. Bombach, A. Inauen N. Bukowiecki, D.B. Kittelson*, W.F. Watts*, Catalytic Combustion of Hydrogen-Air Mixtures over U. Baltensperger, E. Weingartner Platinum: Validation of Hetero/Homogeneous Comparing SM PS Size Distributions with DC, PAS Chemical Recation Schemes and CPC Data Sixth International Conference on Technologies and Proc. 4th ETH Conference on Nanoparticle Combustion for a Clean Environment, Porto, Portugal, Measurement, Zürich, Switzerland (2001). July 9-12, Book of Abstracts, 735-743 (2001). * University of Minnesota, Minneapolis, USA O. Bahn, S. Kypreos, S. Hirschberg Flexible Mechanismen für den Klimaschutz BWK — Das Energie-Fachmagazin 9, 63-65 (2001). 160 I. Colbeck*, C. Bryant*, S. Nyeki, K. Eleftheriadis**, W. Durisch, M. Leutwyler* J. Smolik***, V. Zdimal***, M. Lazaridis****, Performance and Spectral Sensitivity of a Copper N. Mihalopoulos**** Indium Gallium Diselenide Module Optical Properties of Atmospheric Aerosol at Finokalia Extended Abstract, Book of Abstracts, Sharjah Solar (Greece) Energy Conference, Sharjah, UAE, 12, J. Aerosol Sei. 32, Supplement 1, S445-S446 (2001). February 19-22, 2001. * University of Essex, UK * ETH Zürich ** NCSR Demokritos, Greece *** ACSR, Czech Republic W. Durisch, J.-C. Mayor **** University of Crete, Greece Anwendung eines neuen Kennlinienmodells auf Freilandmessungen an einem kommerziellen P. Dietrich, F. Büchi, M. Ruge*, A. Tsukada, Photovoltaikmodul G.G. Scherer, R. Kötz, S. Müller, M. Bärtschi Bulletin SEV/VSE 10/01, 13-15 (2001). P. Rodatz*, O. Garcia* Fuel Cells for Transportation - A Pilot Fuel Cell M. Frioud*, V. Mitev*, R. Matthey*, H. Richner**, Propulsion System S. Gubser**, M. Furger Congress Proc. "8th European Automotive Congress", Backscatter Lidar Detection of the Evolution of the Bratislava, Slovakia, June 18-20, 2001, 1 (2001). Aerosol Stratification in the PBL During Föhn Events * ETH Zürich in FORM Proc. MAP Meeting 2001, Schliersee, Germany P. Dietrich, G.G. Scherer MeteoSchweiz 15, 179-182 (2001). Das Potenzial der Polymer-Elektrolyt Brennstoffzelle * Observatory of Neuchâtel unter Berücksichtigung verschiedener Treibstoffketten ** ETH Zürich Proc. Internal Combustion Engine versus Fuel Cell - Potential and Limitations as Automotive Power M. Furger, K. Baumann*, P. Drobinski**, C. Häberli***, Sources, Graz, Austria, 287-298, September 6-7, B. Neininger****, S. Vogt***** 2001. Vertical Velocity Measurements During the Föhn of 24 October 1999 in the Rhine Valley P. Drobinski*, R. Benoit**, A. Dabas***, Proc. European Geophysical Society XXVI General P.H. Flamant*, M. Furger, C. Häberli****, Assembly, Nice, France, 3 CD-ROM (2001). R. Steinacker*****, C. Boitel*, A. Délavai*, P. Delville*, * ZAMG - Zentralanstalt für Meteorologie J. Donier***, C. Loth*, B. Romand* und Geodynamik, Wien, Austria Unstationary Aspects of Flow Splitting in the Rhine ** Laboratoire de Météorologie Dynamique, Valley: IOP 12 Case Study Ecole Polytechnique, Palaiseau, France Proc. MAP Meeting 2001, Schliersee, Germany *** MeteoSchweiz, Zürich MeteoSwiss 15, 138-141 (2001). **** MetAir AG, lllnau * Laboratoire de Météorologie Dynamique, ***** Institut für Meteorologie und Klimaforschung, FZ, Palaiseau, France Karlsruhe, Germany ** Meteorological Service of Canada, Dorval, Canada M. Furger, S. Gubser*, F. von Arx* *** CNRS - Météo-France, Toulouse, France Vertikalwinde und Schwerewellen in einem Föhntal - **** MeteoSwiss, Zürich Fallstudien mit Szintillometern und Mikrobarographen ***** University of Vienna, Austria während MAP-FORM Proc. DACH-Meteorologen-Tagung 2001, Vienna, W. Durisch, K. Robert*, J. Meier** Austria, ZAMG 27 CD-ROM (2001). Effect of Climatic Parameters on the Performance of * ETH Zürich Silicon Thin-Film Multijunction Solar Cells Extended Abstract, Book of Abstracts, Sharjah Solar A.B. Geiger, E. Lehmann, P. Vontobel, G.G. Scherer, Energy Conference, Sharjah, UAE, 311, A. Wokaun February 19-22, 2001. In-Situ Investigation of Carbon Dioxide Patterns in * now Technical College Lübeck, Germany Anode Flow Fields of Direct Methanol Fuel Cells by ** IMTNeuchâtel Neutron Radiography Proc. 1st European PEFC Forum, F.N. Büchi, W. Durisch, A. Grey* G.G. Scherer, A. Wokaun (Eds.), Luzern, 349-354, Application of a Generalized Model for Solar Cells to July 2001. Outdoor Measurements on a Commercial Module Extended Abstract, Book of Abstracts, Sharjah Solar A.B. Geiger, T. Rager, L. Matejcek*, G.G. Scherer, Energy Conference, Sharjah, UAE, 23, A. Wokaun February 19-22, 2001. Radiation-Grafted Membranes for Application in Direct * now University of Bristol, UK Methanol Fuel Cells Proc. 1st European PEFC Forum, F.N. Büchi, G.G. Scherer, A. Wokaun (Eds.), Luzern, 129-134, July 2001. * Adam Opel AG, Rüsselsheim, Germany 161 D. Goers, M. Lanz, P. Novák M. Hahn, M. Bartsch, B. Schnyder, R. Kötz, Gamma-Butyrolactone as an Additive for Electrolyte M. Carlen*, Ch. Ohler*, D. Evard** Solutions in Lithium-Ion Batteries A 24 V Bipolar Electrochemical Double Layer Chimia 55, 649 (2001). Capacitor Based on Activated Glassy Carbon Power Sources for the New Millenium, M. Jain, M.A. D. Goers, M. Lanz, P. Novák Ryan, S. Surampudi, R.A. Marsh, and G. Nagarajan. Gamma-Butyrolactone: A Useful Component for Eds., Proc. 2000-22, The Electrochemical Society, Lithium-Ion Batteries? Inc., Pennington, NJ (2001). GDCh, Angew. Elektrochem., Pommersfelden, * ABB Corporate Research, Baden Abstract No. P3 (2001). ** Leclanché SA, Yverdon P. Griebel, R. Bombach, W. Kreutner, A. Inauen, F. Hajbolouri, C. Lagergren*, Q.H. Hu**, R. Schären, M. Witt, K. Herrmann* G. Lindbergh*, B. Kasemo**, P. Ekdunge*** Untersuchung zur Stabilität und Struktur von turbulen• Pt and PtRu Model Electrodes for Electrochemical ten Methan/Luft-Vormischflammen Oxidation of Methanol VDI-Berichte Nr. 1629, 639-644 (2001). Proc. 1st European PEFC Forum, Eds. F.N. Büchi, * ETH Zürich G.G. Scherer, A. Wokaun, Luzern, Switzerland, 21-27, July 2-6, 2001. L. Gubler*, G.G. Scherer, A. Wokaun * Volvo Technologica Development,Göteborg, Reformate Tolerance in the PSI 100 cm2 Polymer Sweden Electrolyte Fuel Cell ** Department of Applied Physics, CTH, Göteborg, Proc. 1st European PEFC Forum, Eds. F.N. Büchi, Sweden G.G: Scherer, A. Wokaun, Luzern, Switzerland, *** Applied Electrochemistry, KTH, Stockholm, 247-254, July 2-6, 2001. Sweden * now Johnson Matthey, UK S. Henning, E. Weingartner, S. Schmidt, S. Gubser*, M. Furger, F. von Arx*, H. Richner* H.W. Gäggeler, U. Baltensperger Wave Activity in the Boundary Layer and the Erosion Aerosol-Clouds Interactions at the High Alpine Site of the Cold Air Pool in the Rhine Valley - A Case study Jungfraujoch (3580 m asi) - Experimental Data and (22 October 1999) Modelling Results Proc. MAP Meeting 2001, Schliersee, Germany Proc. European Geophysical Society XXVI General MeteoSchweiz 15, 30-31 (2001). Assembly, Nice, France, CD-ROM (2001). * ETH Zürich S. Henning, E. Weingartner, S. Schmidt, M. Gysel, S. Nyeki, E. Weingartner, U. Baltensperger M. Wendisch, U. Baltensperger Measurement of Particle Hygroscopic Properties on a Results from Simultaneous Measurements of Aerosol Jet Engine Combustor Test Rig and Cloud Parameters at the dungfraujoch Proc. ISAM 13th International Congress, Interlaken, Proc. European Aerosol Conference (EAC) 2001, Switzerland Leipzig, Germany J. Aerosol in Medicine 14, 3 421 (2001). J. Aerosol Sei. 32, Supplement 1, 975-976 (2001). O. Haas, M. Lanz, C. Kormann*, P. Novák D. Hirsch*, P. v. Zedtwitz*, B. Schaffner, S. Kräupl Performance and Rate Capability Measurements on Brennstoffe aus Sonnenlicht für das 21. Jahrhundert - LiMn204 Spinels for Lithium-Ion Batteries. Fossile Brennstoffe werden ersetzt 4th Int. Symp. on New Materials for Electrochemical ETH-Intern, February 10, 2001. Systems, Extended Abstracts, Montreal, Canada, * ETH Zürich 159-161 (2001). D. Hirsch*, P. von Zedtwitz*, B. Schaffner, S. Kräupl, * BASF AG, Ludwigshafen, Germany M. Keunecke O. Haas Neuer Hochfluss-Sonnensimulator für solarchemische Neue elektrochemische Energiespeicher und Hochtemperatur-Prozesse Energiewandler PSI Spectrum 2, 24 (2001). GUTOR UPS Engineering Fachtagungsunterlagen * ETH Zürich March 30, 2001. A. Hoffer*, A. Gelencsér**, A. Molnár**, O. Haas E. Weingartner, U. Baltensperger Membrane Fuel Cells and Electrochemical Double- Comparative Study on the Concentration and Mass Layer Capacitors for Electric Vehicle Applications Absorption of Black Carbon Aerosol at the Extended Abstracts, Symposium of the China dungfraujoch International Battery Fair Peking, June 8-11, 2001. Proc. European Aerosol Conference 2001, Leipzig, Germany J. Aerosol Sei. 32, Supplement 1, S679-S680 (2001). * University of Veszprém, Hungary ** Air Chemistry Group of the Hungarian Academy of Sciences, Veszprém, Hungary 162 J. Huslage, T. Rager, J. Kiefer, L. Steuernagel, J. Keller, S. Andreani-Aksoyoglu, N. Ritter, G.G. Scherer A.S.H. Prévôt, J. Dommen Improved Membrane-Electrode Assemblies for Wind and Vertical Turbulent Exchange over Polymer Electrolyte Fuel Cells Based on Radiation Switzerland and their Influence on Short-Term Air Grafted Membranes Quality. Simulations with SAI MM and UAM-V in H.Z. Massoud, I. Baumvol, M. Hirose, Proc. Eurotrac-2 Symposium 2000, Garmisch- E.H. Poindexter (eds.): Micro-Power Sources, Partenkirchen, Germany Electrochemical Society (ECS) Proceedings Vol. Springer-Verlag, Berlin, Heidelberg, Germany, CD- 2000-3 (2001). ROM (2001). R. Imhof*, I. Exnar*, M. Lanz, E. Lehmann, P. Novák M. Keunecke Vom Labormuster zur Serienfertigung. Batteriebau in Steigender Energiebedarf: Chancen für solare der Schweiz am Beispiel von Lithium-Ionen Batterien Brennstoffe Anwender-Workshop zur Nutzung der Neutronen- PSI Spectrum 4, 22 (2001). radiographie, Proc., PSI Villigen, Switzerland, 72-77 (2001). R. Kötz, M. Bartsch, M. Hahn, B. Schnyder * Renata AG Hingen Bipolarer elektrochemischer Doppelschicht• kondensator mit hoher Leistungsdichte G. Ingold, A. Streun, B. Singh, R. Abela, P. Beaud, Elektrochemische Verfahren für neue Technologien, G. Knopp, L. Rivkin, V. Schlott, Th. Schmidt, H. Sigg, Gesellschaft Deutscher Chemiker, Frankfurt am Main, J.F. van der Veen, A. Wrulich, I. Khan Germany, GDCH-Monographie, Bd. 21; 2000, 158- Sub-Picosecond Optical Pulses at the SLS Storage 166 (2001). Ring PAC2001, Chicago, USA (2001). S. Kräupl, A. Steinfeld Experimental Investigation of a Vortex Flow Solar T. Jentsch*, S. Biollaz, M. Davidovic**, Chemical Reactor for the Combined ZnO-Reduction M. Beckmann** and CH4 Reforming Investigation of Heavy Metal Evaporation in a Pilot Proc. FORUM 2001 Solar Energy: The Power to Plant Scale Municipal Solid Waste Incinerator by Choose, Washington, D.C., USA, April 21-25, 2001. Radiotracers Tracers and Tracing Methods 15, No. 79, 439-448 S. Kunte, M. Tulej, P.P. Radi, T. Gerber, (2001). K. Boulouchos * Fraunhofer Institut für zerstörungsfreie Flame Experiments on the Soot Reduction Potential of Prüfverfahren (IzfP), Germany Acetáis in Diffusion Flames ** Clausthaler Umwelttechnik-Institut GmbH, IEA Conference Proc., 23rd Task Leader Meeting, (CUTEC), Germany Kauai, Hawai (2001). T. Jentsch*, S. Biollaz, M. Davidovic**, M. Lazaridis*, R. Gehrig**, K. Torseth**, K. E. Yttri***, M. Beckmann** A. Semb***, S. Larssen***, F. Stordal***, J. Schaug***, Application of Radioisotopes to Optimize Environ• O. Hov***, A.-G. Hjellbrekke***, J. E. Hanssen***, mental Technology Processes at Example of Heavy C. Dye***, C. Hüglin**, P. Hofer**, J. Smolik****, Metal Release at Thermal Waste Treatment V. Zdimal****, K. Eleftheriadis*****, I. Colbeck******, NAARRI International Conference 2001, Mumbai, S. Nyeki, N. Mihalopoulos*, V. Havranek**** India, December 12-14, 2001. Measurements of Particulate Matter in EMEP * Fraunhofer Institut für zerstörungsfreie NILU Report (2001). Prüfverfahren (IzfP), Germany * University of Crete, Greece ** Clausthaler Umwelttechnik-Institut GmbH, EM PA Dübendorf (CUTEC), Germany *** NILU, Norway **** ACSR, Czech Republic F. Joho, P. Novák, M.E. Spahr* ***** NCSR Demokritos, Greece Safety Investigations on the Negative Electrode of a ****** University of Essex, England Li-Ion Battery by Differential Scanning Calorimetry 200th Electrochem. Soc. Meeting and 52nd ISE Chr. Ludwig Meeting, Meeting Abstracts 2001-2, San Francisco, On-line Analyse von Metallen in Gasen USA, Abstract No. 228 (2001). Tagungsband zur ISWA-Tagung Schweiz * TIMCAL SA, Bodio Hochschule Rapperswil (2001). H. Lutz, Chr. Ludwig, R.P.W.J. Struis On-line Monitoring of Heavy Metal Evaporation Using Inductively Coupled Plasma Optical Emission Spectrometry ICP Information Newsletter 27,1-7 (2001). 163 G. Maier*, C.-K. Shin*, G.G. Scherer P. Novák, F. Joho, M.E. Spahr* Sulpho-Pendent Poly(Ether Ketone)s for Solid Solid State Electrochemistry of Graphite for Lithium- Polymer Electrolyte Membranes Ion Batteries Proc. 1st European PEFC Forum, Eds. F.N. Büchi, 8th Euroconference on Science and Technology of G.G. Scherer, A. Wokaun, Luzern, Switzerland, Ionics, Book of Abstracts, Carvoeiro, Portugal 193-202, July 2-6, 2001. 36-37 (2001). * TU München, Germany * TIMCAL SA, Bodio A. Meier, R. Palumbo, A. Steinfeld P. Novák, R. Nesper*, M. Coluccia, F. Joho, A. Piotto Chemische Brennstoffe aus Sonnenlicht Piotto MTZ Motortechnische Zeitschrift 3, 242-249 (2001). Layered Mixed Metal Oxide with Superior Cycleability Lithium Battery Discussion - Electrode Materials, A. Meier, R. Palumbo, A. Steinfeld Extended Abstracts, Arcachon, France, Abstract No. 5 Chemical Fuels and Materials from Sunlight (2001). - MTZ worldwide 3,15-19 (2001 ). * ETH Zürich - Proc. 5th Cologne Solar Symposium, Cologne, Germany, June 21, 106-115 (2001 ). U.A. Paulus, E. Deiss, A. Wokaun, G.G. Scherer Fundamental Studies of the Catalyst Utilization at the A. Meier, E. Bonaldi*, A. Relier**, A. Hintermann*** Electrode/Electrolyte Interface Using Model Wenn Steine glühen Electrodes ENET-NEWS, Dezember 2001, 50, J. Wellstein ed., Proc. 1st European PEFC Forum, Eds. F.N. Büchi, 11-13 (2001). G.G. Scherer, A. Wokaun, Luzern, Switzerland, * QualiCal AG, Lugano 155-162, July 2-6, 2001. ** University of Augsburg, Germany *** BFE Bern U.A. Paulus, T.J. Schmidt*, V.R. Stamenkovic*, N.M. Markovic*, P.N. Ross* B. Neininger*, W. Fuchs*, M. Baumle*, A. Volz- Oxygen Reduction Activity of Pt and Pt-Alloys in Acid Thomas**, A.S.H. Prévôt, J. Dommen Electrolyte A Small Aircraft for More than Just Ozone: MetAir's Proc. 1st European PEFC Forum, Eds. F.N. Büchi, 'Dimona' After ten Years of Evolving Development G.G. Scherer, A. Wokaun, Luzern, Switzerland, Proc. 11th Symposium on Meteorological 51-58, July 2-6, 2001. Observations and Instrumentation, Albuquerque, * Lawrence Berkeley National Laboratory (LBNL) 14-19 January, Am. Meteorological Soc, 123-128 Berkeley, CA, USA (2001). * MetAir AG, lllnau A.S.H. Prévôt, A. Neftel* ** Institute for Chemistry of the Polluted Atmosphere, Subproject LOOP: Limitation of Ozone Production on Research Center Jülich, Germany a Local and Regional Scale Proc. Eurotrac-2 Symposium 2000, Garmisch- R. Nesper*, P. Novák, M. Coluccia, F. Joho, Partenkirchen, Germany A. Piotto Piotto Springer-Verlag Berlin, Heidelberg, Germany, 81-88 Quaternary Mixed Metal Oxide with High Specific (2001). Charge and Improved Cycling Stability at Ambient and * Federal Research Station of Agroecology at Elevated Temperatures and Agriculture, Bern International Conference on Solid State Ionics SSI 2001, Materials and Processes for Energy & T. Rager, J. Huslage*, G.G. Scherer Environment, Extended Abstracts, Cairns, Australia, Membranelektrolyte für elektrochemische Zellen Abstract No. A-OR-23, 46 (2001). Dechema Monografien 21, 230 (2001). * ETH Zürich * now VW Wolfsburg, Germany R. Nessler, G. Larcheveque*, I. Barlin*, N. Ritter, S. Andreani-Aksoyoglu, J. Keller, N. Bukowiecki, E. Weingartner, U. Baltensperger, A.S.H. Prévôt, J. Dommen H. van den Bergh*, B. Calpini* Modelling with UAM-V: Influence of Different Study of the Tropospheric Aerosol at the Jungfraujoch Boundary Concentrations on the Ozone Formation in Alpine Station by Mean of Simultaneous Lidar and In- Switzerland Situ Measurements Proc. EUROTRAC-2 Symposium 2000, Garmisch- Proc. European Aerosol Conference 2001, Leipzig, Partenkirchen, Germany Germany Springer-Verlag Berlin, Heidelberg, Germany, CD - J. Aerosol. Sei. 32, Supplement 1, S447-S448 (2001). ROM (2001). * EPF Lausanne 164 M. Ruge*, F.N. Büchi G. Strub*, U. Beisl**, M. Schaepman*, D. Schlaepfer*, Bipolar Elements for PE Fuel Cell Stacks Based on C. Dickerhof*, K. Itten* the Mould to Size Process of Carbon/Polymer Evaluation of Diurnal Hyperspectral BRF Data Mixtures Acquired with the RSL Field Goniometer During the Proc. 1st European PEFC Forum, Eds. F.N. Büchi, DAISEX'99 Campaign G.G. Scherer, A. Wokaun, Luzern, Switzerland, Proc. on Imaging Spectroscopy, Ed. Enschede, 399-308, July 2-6, 2001. (2001). * ETH Zürich * RSL, University of Zürich ** German Aerospace Center, German Remote G.G. Scherer, A. Röder Sensing Data Center, Wessling, Germany Auswirkungen der Brennstoffzellen-Technologie auf die Entwicklung alternativer Antriebe im Automobil• S. Stucki, S. Biollaz bereich Treibstoffe aus Biomasse Automobiltechnische Zeitschrift (ATZ) 103, 274-281 MTZ Motortechnische Zeitschrift 4/2001, 309-312 (2001). (2001). Impact of Fuel Cell Technology for Automotive Applications A. Thielmann*, A.S.H. Prévôt, F. Grüebler*, ATZ Worldwide, April 2, 2001. J. Staehelin* Identifying Ozone Production Regimes on Basis of M.E. Spahr*, H. Wilhelm*, F.Joho, P. Novák Measurements Structure, Texture, and Surface Morphology Proc. 8th European Symposium on the Physico- Modifications of Highly Crystalline Graphite and the Chemical Behaviour of Air Pollutants, Torino, Italy, Consequences for its Electrochemical Lithium (2001). Insertion Behavior * ETH Zürich 14th International Battery Association Symposium, Book of Abstracts, Kwa-Maritane, South Africa, 8 A. Thielmann*, A.S.H. Prévôt, F. Grüebler*, (2001). J. Staehelin* Field Measurements of Nitrogen Oxides, Ozone and * TIMCAL SA, Bodio Reactive Organic Gases in the Po Basin: Sensitivity of Photooxidant Production A. Steinfeld Proc. Eurotrac-2 Symposium 2000, Garmisch- International Energy Agency - SolarPACES Partenkirchen, Germany Annual Report 2000, W. Grasse ed., Chapter 4 Springer-Verlag Berlin, Heidelberg, Germany, (2001). 81-88 (2001). A. Steinfeld, M. Epstein* * ETH Zürich Light Years Ahead Chemistry in Britain 37, 30-32 (2001). E. Weingartner, S. Henning, M. Gysel, N. Bukowiecki, * Weizmann Institute of Science, Rehovot, Israel U. Baltensperger Hygroscopicity of Aerosol Particles at low A. Steinfeld Temperatures Fuel from Sunlight Proc. European Aerosol Conference 2001, Leipzig, Vision - Science and Innovation Made in Switzerland Germany 4, 28 (2001). J. Aerosol Sei. 32, Supplement 1, S977-S978 (2001). N. Streit, E. Weingartner, U. Baltensperger, E. Weingartner, S. Henning, N. Bukowiecki, M. Gysel, H.W. Gäggeler S. Nyeki, N. Streit, U. Baltensperger Physical Parameters for Chemical Characterization: The Cloud and Aerosol Characterization Experiment Linking Hygroscopitcity and Volatility (CLACE) at the Jungfraujoch Proc. Eurotrac-2 Symposium 2000, Garmisch- International Foundation HFSJG, Bern, Switzerland, Partenkirchen, Germany Activity Report, 53-56 (1999/2001). Springer-Verlag Berlin, Heidelberg, Germany, 2001, CD-ROM (2001). J. Wochele, Chr. Ludwig, A.J. Schuler, A. Krebs* Optimisation of Metal Recycling from Batteries G. Strub*, J. Keller, M. Schaepman*, U. Beisl**, Proc. EMC Conference, Friedrichshafen, Germany, K. Itten* 165-173 (2001). Comparison of Modeled and Measured Directional * BATREC AG, Wimmis Reflectance Data of an Alfalfa Canopy Proc. 8th International Symposium on Physical DISSERTATIONS Measurements and Signatures in Remote Sensing, Aussois, France, 285-290 (2001). H. Armbruster * RSL, University of Zürich Treibstoffumwandlung im Fahrzeug: Dimethylether ** German Aerospace Center, German Remote aus Methanol für Dieselmotoren Sensing Data Center, Wessling, Germany Ph.D. Thesis, No.14388, ETH Zürich, October 30, 2001. 165 L. Barreto DIPLOMA THESES Technological Learning in Energy Optimisation Models and Deployment of Emerging Technologies M. Beerli Ph.D. Thesis, No. 14151, ETH Zürich, May 25, 2001. Wirkungsgradberechnung eines chemischen Solarreaktors für die Zinkproduktion durch thermische O. Epelly Dissoziation von Zinkoxid An Interior Point Method for Smooth Convex Institute of Energy Technology, ETH Zürich and PSI Optimization -Application to Large-Scale Economic Villigen, February 2001. Models Ph.D. Thesis, Faculté des Sciences Economiques et V. Chevillât Sociales, Section HEC, University of Geneva, 2001. Stable Carbon Abundance in Canopy-Tree Foliage of a Temparate Deciduous European Forest Under K. Geissler Elevated C02. Wasserstoffgewinnung aus Methanol für PEM- Institute of Botany, University of Basel and PSI Brennstoffzellen-Anwendungen Villigen, August 2001. Ph.D. Thesis, EPF Lausanne, August 27, 2001. Ch. Cortina M.Jäggi Production of Solar Hydrogen by Water-Splitting with Effects of Altered Nutrient Regimes on the Stable Zinc 13 18 15 Isotopes C, O and N in Needles of Mature Institute of Energy Technology, ETH Zürich and PSI Spruce Trees (Picea abies) Villigen, July 2001. Ph.D. Thesis, University of Bern, 2001. N. De Silva M. Kraus Catalyst Characterisation, Catalyst Screening and Catalytic C02-Reforming of Methane in a Dielectric Hydrogen Adsorption for Catalytic Systems to Barrier Discharge Produce Hydrogen Ph.D. Thesis, No. 14205, ETH Zürich, May 30, 2001. University of Kingston, UK, July 2000 - June 2001. S. Möller C.-F. Draschil Entwicklung eines Reaktors zur solarthermischen Herstellung von Zink aus Zinkoxid zur Charakterisierung von H2-02-Polymerelektrolyt- Energiespeicherung mit Hilfe konzentrierter Brennstoffzellen mit Schwerpunkt auf der Variation Sonnenstrahlung des Kathodenkatalysators Hochschule für Technik, Wirtschaft und Kultur Leipzig Ph.D. Thesis, No. 14277, ETH Zürich, July 6, 2001. (FH), Germany, April-Juli 2001. R. Eckl L.C. Reichenbach de Sousa Ortsaufgelöste Strommessung in Polymer-Elektrolyt- Gasification of Wood, Urban Wastewood (Altholz) and Brennstoffzellen other Wastes in a Fluidised Bed Reactor Lehrstuhl für Energiewirtschaft und Anwendungs• Ph.D. Thesis, No. 14207, ETH Zürich, June 13, 2001. technik, TU München, Germany, November 2000 - R. Richner April 2001. Entwicklung neuartig gebundener Kohlenstoff• materialien für elektrische Doppelschicht• P. Grysiak kondensatorelektroden Modelling of Biomass Gasification with ASPEN Plus Ph.D. Thesis, No. 14413, ETH Zürich, October 30, Cracow University of Technology, PL, 2001. December 2000 - February 2001. A. Röder Integration of Life-Cycle Assessment and Energy TALKS Planning Models for the Evaluation of Car Powertrains Invited Talks and Fuels Ph.D. Thesis, No. 14291, ETH Zürich, July 11, 2001. S. Andreani-Aksoyoglu Modelling of Air Quality with CAMx: A Case Study in T.J. Schildhauer Switzerland Untersuchungen zur Verbesserung des Wärme• Second International Symposium on Air Quality and übergangs in katalytischen Festbettreaktoren für Management at Urban, Regional and Global Scales Istanbul, Turkey, September 25-28, 2001. Energiespeicheranwendungen Ph.D. Thesis, No. 14301, ETH Zürich, July 25, 2001. H. Armbruster On-Board Generation of DME from Methanol "Towards Zero Emission Diesel Engines" Conference PSI Villigen, June 15, 2001. 166 U. Baltensperger S. Biollaz Aerosols: Sources and Sinks - and What Happens in Thermische und mechanische Schwermetall• Between abtrennung Forschung im Abfallbereich - ISWA CH Tagung UC Berkeley, Berkeley CA, USA, October 24, 2001. Hochschule Rapperswil, March 28, 2001. U. Baltensperger S. Biollaz Progress and Outstanding Problems in the Methan aus Biomasse Characterization of the Physical and Chemical Erdgas als Treibstoff für Verbrennungsmotoren, ZAP Properties of Atmospheric Aerosols Tagung, EMPA Dübendorf, November 16, 2001. PNNL, Richland WA, USA, October 22, 2001. U. Baltensperger B. Bougie Atmospheric Aerosols and Their Impact on Climate Soor Characterisation in a Diesel Engine IVC-15, San Francisco, USA, October 28 - November University of Eindhoven, The Netherlands, 2, 2001. November 2, 2001. U. Baltensperger F.N. Büchi Aerosols: Formation, Transformation and Elimination Technik und Anwendungen von Brennstoffzellen UC Davis, Davis CA, USA, October 26, 2001. Seminar im Rahmen der Veranstaltungsreihe Interface der Fachhochschule Aargau, Windisch, May U. Baltensperger 28, 2001. The Atmospheric Aerosol: Challenges and Recent Findings within the EUROTRAC Subproject F. Gassmann AEROSOL Influence of Noise and Spikes on Chaos-Order 5th GLOREAM Workshop, Wengen, Switzerland, Transitions September 24-26, 2001. Kolloquium für Neuroinformatik, ETH Zurich/University of Zürich, January 12, 2001. U. Baltensperger Wettbewerb und Gleichgewicht: Das atmosphärische F. Gassmann Aerosol zwischen Kinetik und Thermodynamik Von der Kreativität der Fehler - Einführung in die Sicherheit und Umweltschutz in der Chemie, Chaostheorie Seminarreihe Sommersemester 2001, ETH Zürich, MIGROS, Business Event, Zürich, January 22, 2001. May 21, 2001. F. Gassmann U. Baltensperger Umweltethik The Organic Component of the Atmospheric Aerosol: Facts and Fiction ETH-Emeritenstamm, Winterthur, March 26, 2001. European Aerosol Conference 2001, Leipzig, Germany, September 3-7, 2001. F. Gassmann Noise-Induced Chaos-Order Transitions U. Baltensperger MABiC-Workshop 2001, Lavin, March 27, 2001. Aerosol Research at the Jungfraujoch F. Gassmann Board Meeting of the Foundation High Altitude Does Complexity Science offer an Escape from the Research Stations Jungfraujoch and Gornergrat, Reductionist Trap? Zermatt, Switzerland, October 5-6, 2001. IDSIA-Seminar, Manno, April 27, 2001. U. Baltensperger Verhalten von Partikeln in der realen Atmosphäre F. Gassmann HdT-Tagung Strategien zur Minimierung der Greenhouse-Effect — IPCC and Beyond Partikelemission von Verbrennungsmotoren, Munich, West University of Timisoara, Romania, Germany, June 28-29, 2001. May 22, 2001. F. Gassmann U. Baltensperger Complex Systems — Old Stuff in New Bottles? Activities of the SAG Aerosol West University of Timisoara, Romania, GAW 2001, Geneva, April 2-4, 2001. May 23, 2001. U. Baltensperger F. Gassmann Physicochemical Properties of Atmospheric Aerosols Climate and Energy — Overview of Risks and 12th Annual Meeting of the Aerosol Society, Bath, UK, Potential Solutions June 18-19, 2001. AGS Summer Seminar, Braunwald, August 27, 2001. 167 T. Gerber T. Lippert Application of Spectroscopic Techniques in the VUV Tailor Made Polymers for Laser Applications to Combustion Relevant Molecules Symposium on Laser Interaction in Soft Materials with LURE/SOLEIL, SU5 User Meeting, Orsay, France, Application to Nano-Engineering, Osaka, Japan, September 24, 2001. February 2001. O. Haas T. Lippert Elektrochemische Energiespeicherung und Polymers for UV and Near-IR Irradiation Energiewandlung 4th International Symposioum PCPM 2001 GUTOR Fachtagung, Hotel Du Parc, Baden, (International Symposium on Photoreaction Control March 30, 2001. and Photofunctional Materials), Tsukuba, Japan, March 2001. O. Haas Membrane Fuel Cells and Electrochemical Double- T. Lippert Layer Capacitors for Electric Vehicle Applications Novel Applications of Polymers Designed for Laser Symposium of the China International Battery Fair Ablation Peking, China, June 8-11, 2001. E-MRS Spring Conference, Symposium "Photon- induced processing of surfaces", Strasbourg, France, O. Haas June 2001. Performance and Rate Capability Measurements on T. Lippert UMn204 for Lithium-ion Batteries 4th International Symposium New Materials for Polymers Designed for Laser Ablation-Influence of Electrochemical Systems, Montreal, Canada, Photochemical Properties August 9-13, 2001. 5th International Conference on Laser Ablation (COLA), Tsukuba, Japan, October 2001. O. Haas Fuel Cell Research at Paul Scherrer Institute T. Lippert Beijing Fuyuan Pioneer New Energy Material Limited Polymers Designed for Laser Applications- Corporation, Peking, China, June 12, 2001. Fundamentals and Applications University of Linz, Austria, Department of Applied O. Haas Physics, December 2001. Synchrotron X-ray Absorption and Diffraction Studies Chr. Ludwig of La0,6Ca0ACoO3 Perovskite Lawrence Berkeley Laboratory, Berkeley, USA, Evaporation of Heavy Metals in Thermal Processes September 18, 2001. Seminar in Process Engineering, ETH Zürich, April 10, 2001. F. Holzer More Specific Energy in Rechargeable Zn/Air Cells S. Müller 200th Meeting of the Electrochemical Society, San Chemically Bonded Carbonaceous Material for Francisco, CA, USA, September 2-6, 2001. Double-Layer Capacitor Applications 4th International Symposium on New Materials for M.Jäggi Electrochemical Systems, Montreal Canada, July 9-13, 2001. ô13C Variations in Different Compartments of Spruce (Picea abies) M. Neracher Champenoux, France, September 4-5, 2001. Laser-induzierte Gitter Institut für Luft- und Raumfahrt (DLR) in Lampolds• R. Kötz hausen, Germany, November 9, 2001. Materialforschung für Supercaps am PSI Fachgespräch „Superkondensatoren - Perspektiven E. Newson der Weiterentwicklung" Universitäts- und Low Temperature Reforming (POX) and Preferential Landesbibliothek, Heinrich-Heine-Universität Oxidation Catalysts (PROX) for Liquid Energy Carriers Düsseldorf, Germany, May 2, 2001. Robert Bosch GMBH, Schwieberdingen, Germany, R. Kötz February 2, 2001. Electrochemical Double-Layer Capacitors: Fundamental Principles and State of the Art P. Novák Giornate delPEIettrochimica Italiana 2001, Lecce, Italy, Solid State Electrochemistry of Graphite for Lithium- September 20-22, 2001. Ion Batteries 8th Euroconference on Science and Technology of A. Kouzov Ionics, Carvoeiro, Portugal, September 19, 2001. Rotational Relaxation and Collision-Induced Transitions in the Resonance 4-Wave Mixing Spectra Université de Franche-Comte, Besançon, France, October 25, 2001. 168 P. Novák G.G. Scherer Layered Mixed Metal Oxide with Superior Cycleability, Nanostructured Materials in Polymer Electrolyte Fuel Lithium Battery Discussion - Electrode Materials, Cells Arcachon, France, May 31, 2001. "Nanotechnology Perspectives for Supercaps, Batteries, and Polymer Electrolyte Fuel Cells", TOP R. Palumbo NANO 21 Nanotechnology Workshop, Board of the High Temperature Solar Chemistry Research: A path Swiss Federal Institutes of Technology, Bern, July 13, toward sustainable energy technology 2001. ASME Sectional Meeting at Valparaiso University, USA, November 6, 2001. G.G. Scherer H2 Fuel Cell Technology A.S.H. Prévôt ETSF 2, Energy Technologies for a Sustainable Chemie im Alpenraum Future, "Transitions to Solar Hydrogen", Paul Scherrer Institute for Atmospheric Science, ETH Zürich, Institut, Switzerland, November 23, 2001. April 9, 2001. G.G. Scherer A.S.H. Prévôt Brennstoffzellen - Chancen und Herausforderungen YOGAM (Year of Gas Phase and Aerosol ABB Industrie, Turgi, November 25, 2001. Measurements) Concept and First Results GLOREAM Workshop, Wengen, September 24-26, G.G. Scherer 2001. Proton-Conducting Polymer Membranes - A Key Component for Polymer Electrolyte Fuel Cells T. Rager 3rd International Conference on the Application of Piles à Combustible - Une Vue d'Ensemble Conducting Polymers, Mishima, Shizuoka, Japan, Ecole d'ingénieurs, Fribourg, January 11, 2001. November 26-28, 2001. T. Rager G.G. Scherer Low-Defect Radiation-Grafted Membranes Fuel Cells for Automotive Applications. R&D at Paul Workshop "Elektrolyte und Gasphasenreaktionen in Scherrer Institut Brennstoffzellensystemen", DFG- Schwerpunkt• Nissan Technology Center, Japan, November 29, programm "Neue Schichtstrukturen für Brennstoff• 2001. zellen", Pommersfelden, Germany, October 21-23, 2001. G.G. Scherer Development Trends in Materials Research for G.G. Scherer Polymer Electrolyte Fuel Cells Polymerelektrolyt Brennstoffzellen, Materialien - Musashi Institute of Technology, Tokyo, Japan, Zellen - Systeme November 29, 2001. Physics Department, Technical University of Munich, Germany, February 7, 2001. G.G. Scherer Fuel Cell Development at Paul Scherrer Institute G.G. Scherer Asahi Glass Research Center, Kanagawa, Japan, Von der Materialforschung zur Entwicklung von November 30, 2001. Polymerelektrolyt Brennstoffzellen. Forschungs- und Entwicklungsarbeiten am Paul G.G. Scherer Scherrer Institut Brennstoffzellen - Eine Einführung in die Abschlusssymposium Forschungsverbund verschiedenen Technologien "Methanolbrennstoffzellen", Zentrum für Wissenschaftsapéro, EMPA-Akademie, Dübendorf, Sonnenenergie und Wasserstoff-Forschung, Ulm, December 10, 2001. Germany, March 8, 2001. G.G. Scherer G.G. Scherer Was kann die Brennstoffzellentechnologie zur Membranen für Polymerelektrolyt Brennstoffzellen - nachhaltigen Entwicklung beitragen? Entwicklungstrends Vortragsreihe "Wissenschaft, Technik und Ethik", dmc2, Degussa Metals Catalysts Cerdee AG, Evangelische Studentengemeinde der Technischen Geschäftsbereich Brennstoffzellen, Hanau, Germany, Universität Clausthal-Zellerfeld, Germany, March 9, 2001. December 12, 2001. G.G. Scherer G.G. Scherer Trends in der Materialentwicklung für Polymer• Anforderungen an den Elektrolyten in der elektrolyt Brennstoffzellen. Polymerelektrolyt Brennstoffzelle Materials Day, Department für Werkstoffe, ETH Fa. Sartorius, Göttingen, Germany, December 12, Zürich, May 18, 2001. 2001. 169 T.J. Schmidt A. Steinfeld Oxygen Reduction in Alkaline Solution - Implications Hydrogen Production with Concentrated Solar Energy for Fuel Cell Cathodes ETSF2 - Transitions to Solar Hydrogen, PSI, Gordon Research Conference on Fuel Cells, Bristol, November 23, 2001. Rl, USA. July 29 - August 3, 2001. S. Stucki R. Siegwolf Bioenergie ô13C and ô160 Dual Isotope Approach for the Analysis Journée de Reflexion, SATW, Chexbres, France, of Plant Physiological Responses on Environmental June 19, 2001. Changes J. Wambach Jülich, Germany, January 22-24, 2001. Oxidation of Stainless Steel under Dry and Aqueous Conditions: Oxidation Behaviour and Composition R. Siegwolf Department Seminar, Department of Chemical The Use of Stable Oxygen Isotopes in Plant Physics; Fritz-Haber-lnstitute of the Max-Planck Physiological Research Society, Berlin, Germany, March 16, 2001. Nancy, France, September 3-4, 2001. R. Siegwolf E. Weingartner Stable Isotopes in Tree Rings and18O Analysis In Aerosol Research at the Paul Scherrer Institute Organic Matter Lund University, Division of Nuclear Physics, Lund, NETCARB first Summer School, Orvieto, Italy, Sweden, April 19, 2001. September 26-29, 2001. E. Weingartner R. Siegwolf Hygroscopic Behavior of Fresh Soot Particles and If13C Fails as a Tracer for the Carbon Distribution, is After Aging 14C a Possible Solution? Experiences with Natural 13th International Congress on Aerosols in Medicine C02 Sources in Italy. Tracing Carbon in Elevated C02 (ISAM), Interlaken, Switzerland, August 17, 2001. Experiments: A Workshop on where the Carbon is Going. A. Wokaun Duke University, Durham NC, USA, October 18-21, Nachhaltige Technik - Strategie zu neuen 2001. Fahrzeugtypen aus der Sicht technischer Neuentwicklungen A. Steinfeld Berner Verkehrstage, Informations-Plattform 5, Bern, Brennstoffe aus Sonnenlicht February 2, 2001. Generalversammlung des SSES - Schweizerische A. Wokaun Vereinigung für Sonnenenergie, PSI, March 16, 2001. Pilotregion Basel, Mobilität - Visionen für die Zukunft Strategie Nachhaltigkeit, 2000 Watt-Gesellschaft, A. Steinfeld Basel, September 2, 2001. High-Temperature Solar Thermochemical Processing for Greenhouse Gas Mitigation A. Wokaun University of Pennsylvania, USA, April 19, 2001. Future Mobility Fuels and Power Sources AGS-Workshop, Chalmers University, Göteborg, A. Steinfeld Sweden, October 18, 2001. Solar Fuels Tutorial Session by FORUM 2001 - ASME Solar A. Wokaun Engineering Conference, Washington D.C., USA, April Die Brennstoffzelle - Teil eines nachhaltigen 25,2001. Antriebssystems? Seminarreihe Sicherheit und Wmweltschutz in der A. Steinfeld Chemie, ETH Zürich, November 9, 2001. Solar Fuels and Chemicals A. Wokaun MIT-Energy Laboratory, Boston, USA, April 26, 2001. Systemaspekte der Brennstoffzelle - von der Elektrochemie bis zur Treibstoffversorgung A. Steinfeld GDCh-Seminar, TU München, Germany, November 13, 2001. Solar Fuels for C02 Mitigation st Latsis Symposium 2001 - Science for the 21 century, A. Wokaun ETH Zürich, September 27-28, 2001. Fahrzeuge mit alternativen Treibstoffen: Überblick, A. Steinfeld Problemstellung, mögliche Lösungsansätze Chemical Storage and Transport of Solar Energy EcoCar-Workshop, Bellinzona, November 19, 2001. Chalmers University of Technology, Göteborg, Sweden, October 8, 2001. A. Wokaun Perspectives of Fuel Cell Development in Transportation and in Portable Devices Laboratory of Process Engineering ETH Zürich, November 20, 2001. 170 Other Talks J. Dommen Analysis of Airborne Formaldehyde Measurements in S. Andreani-Aksoyoglu the Milan Area Applicability of Indicator-Based Approach to Assess Oxygenated Organics in the Atmosphere - Sources, Ozone Sensitivities: A Model Study in Switzerland Sinks and Atmospheric Impact, Como, Italy, Second International Conference on Air Pollution October 5-7, 2001. Modelling and Simulation Champ-sur-Marne, April 9-12, 2001. W. Durisch Performance and Spectral Efficiency of a Copper C. Appel Indium Gallium Diselenide Module Catalytic Combustion of Hydrogen-Air Mixtures over Sharjah Solar Energy Conference, University of Platinum: Validation of Hetero/Homogeneous Sharjah, United Arab Emirates, February 19-22, 2001. Chemical Recation Schemes Sixth International Conference on Technologies and W. Durisch Combustion for a Clean Environment, Porto, Portugal, Effect of Climatic Parameters on the Performance of July 9-12, 2001. Silicon Thin-Film Multijunction Solar Cells Sharjah Solar Energy Conference, University of U. Baltensperger Sharjah, United Arab Emirates, February 19-22, 2001. The Global Atmosphere Watch Program of WMO Symposium on Global Aerosol Climatology Database, W. Durisch Portland, Oregon, USA, October 13-14, 2001. Application of a Generalized Model for Solar Cells to Outdoor Measurements on a Commercial Module U. Baltensperger, S. Henning, E. Weingartner, Sharjah Solar Energy Conference, University of S. Schmidt Sharjah, United Arab Emirates, February 19-22, 2001. Cloud and Aerosol Characterization at the High Alpine Site Jungfraujoch (3580 m asi) W. Durisch lAMAS 2001, Innsbruck, Austria, July 10-18, 2001. Recent Developments of Thermophotovoltaics at PSI Politécnico di Torino, Italy, June 27, 2001. L. Barreto, S. Kypreos Learning and Carbon Trade Interactions in a Multi- A.B. Geiger Regional Global MARKAL Model In-Situ Investigation of Carbon Dioxide Patterns in Joint Seminar of the Unidustria Venezia and the Kyoto Anode Flow Fields of Direct Methanol Fuel Cells by Club, Venice Italy, May 15-17, 2001. Neutron Radiography Anwender-Workshop zur Neutronenradiographie, PSI S. Biollaz Villigen, May 14, 2001. Biomass Fuel Options Transition to Solar Hydrogen, ETSF 2 Conference, T. Gerber PSI Villigen, November 23, 2001. Soor Formation in a Ethylene/Acetal Diffusion Flame XXIII lEATask Leader Meeting, Kauai, Hawaii, S. Bojinski, D. Schläpfer*, M. Schaepman*, J. Keller September 9-12, 2001. Calculating the Atmospheric Effect in Airborne Imaging Spectrometry Using Modtran M. Gysel AFB Hanscom, Boston MA, USA, June 6-8, 2001. * University of Zurich Theoretical and Experimental Hygroscopic Properties of Laboratory Generated Aerosols S. Bojinski, D. Schläpfer*, M. Schaepman*, J. Keller Institute for Atmospheric and Climate Science, ETH Sensitivity Analysis for the Retrieval of Aerosol Optical Zürich, August 23, 2001. Parameters from Imaging Spectrometer Data Innsbruck, Austria, July 10-18, 2001. M. Gysel, S. Nyeki, E. Weingartner, U. Baltensperger * University of Zurich Hygroscopic Properties of det Engine Combustor Particles F.N. Büchi, M. Ruge Innsbruck, Austria, July 16, 2001. PE Fuel Cells: Evaluation of Concepts for a Bipolar Plate Design and Construction O. Haas 200th Meeting of The Electrochemical Society, and the 52nd Meeting of the International Society of Synchrotron X-ray Absorption and Diffraction Studies Electrochemistry, San Francisco, CA, USA, of La0.6CaoACo03 Perovskite Catalyst in Bifunctional September 2-7, 2001. Oxygen Electrodes Joint International Meeting of the International Society J. Dommen of Electrochemistry and The Electrochemical Society, Airborne Formaldehyde Measurements in the Milan San Francisco, California, September 2-7, 2001. Area International Conference on the Analysis of Carbonyl Compounds, Münster, Germany, June 6-8, 2001. 171 P. Häberling M. Keunecke, S. Moeller*, A. Meier, J. Lédé**, Der Solarofen des PSI M. Ferrer**, R. Palumbo Weiterbildung in der Praxis für Heizwerkführer Forum, The Solar Thermal Decomposition of ZnO: Schweizerischer Verein für Druckbehälterüber• An Exploratory Study of Separating the Gaseous wachung (SVDB), PSI, November 29, 2001. Products with a Quench Process ISES 2001 Solar World Congress, Adelaide, Australia, M. Hahn, M. Baertsch, B. Schnyder, R. Kötz, O. Haas November 25-30, 2001. Influence of Self-Discharge on the Life Time of * DLR Stuttgart, Germany Double-Layer Capacitors Based on Glassy Carbon ** LSGC-CNRS-ENSIC Nancy, France and Sulfuric Acid. 4th International Symposium on New Materials for M. Koebel Electrochemical Systems; Montreal, Canada, Verminderung der Stickoxide mittels Harnstoff-SCR. July 9-13, 2001. ENET-Seminar "Auf dem Weg zum Nullemissions- Dieselmotor". PSI Villigen, Juni 15, 2001. F. Hajbolouri Pt and PtRu Model Electrodes for Electrochemical M. Koebel, G. Madia, M. Elsener Oxidation of Methanol Selective Catalytic Reduction of NO and N02 at Low 1st European PEFC Forum, Luzern, Switzerland, Temperatures July 2-6, 2001. Europacat V, Limerick, September 2-7, 2001. B. Hemmerling Gas Phase Diagnostics by Laser-Induced Gratings A.P. Kouzov Paris, February 2, 2001. Studies of Tensor Gratings in TC-RCWM Spectra of Diatomics: Collisional Perturbations and Symmetry of B. Hemmerling Electronic States Geschwindigkeitsmessungen in der Höhen• XX European CARS Workshop, Lund, Sweden, simulationskammer P6 des DLR April 1-3, 2001. Lampoldshausen, Germany, November 9, 2001. S. Kräupl, A. Steinfeld Pulsed Gas Feeding for Stoichiometric Operation of a F. Holzer Gas-Solid Vortex Flow Solar Chemical Reactor ELZA-Development of Electrically Rechargeable Zinc- FORUM 2001 Solar Energy: The Power to Choose, Air Batteries Washington, DC, USA, April 21-25, 2001. Final Meeting of EU-Project, Oberderdingen, Germany, October 11, 2001. S. Kräupl, A. Steinfeld Experimental Investigation of a Vortex Flow Solar W. Hubschmid Chemical Reactor for the Combined ZnO-Reduction Recent Activities of the Combustion Diagnostics and CH4 Reforming Group at PSI FORUM 2001 Solar Energy: The Power to Choose, ERCOFTAC Annual Meeting, ETH Zürich, June 11, Washington, DC, USA, April 21-25, 2001. 2001. M.Jäggi S. Kunte S13C Variationen in verschiedenen Komponenten von Optical Measuring Techniques Towards the Fichten (Picea abies) - Stärke, Nadelmaterial, Früh- Characterisation of Soot Formation and Oxidation und Spätholz within a Laminar Diffusion Flame Institute of Botany, University of Basel, October 22, ERCOFTAC, Zürich, June 6, 2001. 2001. S. Kunte F. Joho Influence of Oxygenated Fuels on the Sooting Safety Investigations on the Negative Electrode of a Behaviour of Laminar Diffusion Flames Li-Ion Battery by Differential Scanning Calorimetry Nanoparticle Conference, Zürich, August 6-7, 2001. 200th Electrochem. Soc. Meeting and 52nd ISE Meeting, San Francisco, USA, September 2001. S. Kypreos The Energy Markets of China and Emission Control; J. Keller, S. Andreani-Aksoyoglu, A.S.H. Prévôt Some Insights from MARKAL. Applicability of Indicator-Based Approach to Assess Joint Seminar of the Unidustria Venezia and the Kyoto Ozone Sensitivities: A Model Study in Switzerland Club, Venice Italy, May, 15-17, 2001. Wengen, September 24-26, 2001. S. Kypreos, O. Bahn J. Keller Endogenous Technological Learning: Insights from Retrieval of Aerosol Properties Using MISR Data the MERGE-ETL Model Los Alamos National Laboratory, NM, USA, May 1, Joint EMF/IEA/IEW Meeting, Vienna, Austria, June 2001. 19-21, 2001. 172 S. Kypreos, O. Bahn C. Padeste, B. Steiger, L. Tiefenauer Towards Endogenous Technological Learning in Avidin-Biotin Based Molecular Architectures for Integrated Assessment Models Electrochemical Biosensors Annual Conference SAEE, Zürich, October 17, 2001. Schweiz. Arbeitsgemeinschaft Oberflächen und Grenzflächen, 17 Meeting, January 25, 2001. M. Lanz Charakterisierung von Lithium-Ionenbatterien und C. Padeste, B. Steiger, L. Tiefenauer ihren Komponenten Electrode Reaction Mechanisms and Interfacial University of Bern, April 5, 2001. Structure (ERMIS) 6thMeeting, Bad Kosen, Germany, April 5-8, 2001. Chr. Ludwig Studying the Evaporation Behavior of Heavy Metals U.A. Paulus, E. Deiss, A. Wokaun, G.G. Scherer by Thermo-Desorption Spectrometry Fundamental Studies of the Catalyst Utilization at the Colloquium Analytische Atomspektroskopie, Electrode/Electrolyte Interface Using Model CANAS'01, TU Freiberg, Germany, March 13, 2001. Electrodes 1st European PEFC Forum, Luzern, Switzerland, July I. Mantzaras 2-6, 2001. Effects of Finite Rate Heterogeneous Kinetics on Homogeneous Ignition in Catalytically Stabilized A.S.H. Prévôt, R.O. Weber Channel Flow Combustion Ozone Trends in Southern Switzerland, TOR II 2001 Joint Annual Meeting of the Leonhard Euler Meeting, Ankara, Turkey, September 9-12, 2001. Competence Centers, ETH Zürich, June 11, 2001. A.S.H. Prévôt, R.O. Weber I. Mantzaras Climatology of Ozone Transport from the Free Catalytically Stabilized Combustion for Power Troposphere into the Boundary Layer During North Generation Applications Foehn in the Southern Alps Auf dem Weg zum Nullemissions-Dieselmotor, PSI, European Geophysical Society 26th General June 15, 2001. Assembly, Nice, France, March 25-30, 2001. I. Mantzaras F. Raimondi, K. Geissler, J. Wambach, A. Wokaun Design Issues in Catalytic Combustion Applications Methanol Partial Oxidation and Steam Reforming: A for Gas Turbines "Quasi-in-situ" Investigation By XPS and TPD Workshop on Catalytic Combustion, Aistom, Dättwil, 13th Interdisciplinary Surface Science Conference, September 26, 2001. University College, London, UK, April 2-5, 2001. M.J. Montenegro. T. Lippert, S. Müller, M. Reinke A. Weidenkaff*, P. Willmott An Experimental and Numerical Investigation of High- Pulsed Laser Deposition of La0,6CaoACo03 (LCCO) Pressure Catalytically Stabilized Combustion of Films. A Promising Metal-Oxide Catalyst for Air Based Methane/Air Mixtures over Platinum Batteries 2001 Joint Annual Meeting of the Leonhard Euler LANMAT 2001, Venice Italy, October 2001. Competence Centers, ETH Zürich, June 11, 2001. * University of Augsburg, Germany N. Ritter, J. Dommen, J. Keller, S. Andreani- M. Musella Aksoyoglu, A.S.H. Prévôt Development of a Reflectometer for the Determination How to Tune Emissions for Air Quality Simulations to of Spectral Reflectivity at High Temperatures Approach Reality: A Study for the Milan Area 6th International Workshop on Subsecond 5 GLOREAM Workshop, Wengen, Switzerland, Thermophysics, Leoben, Austria, September 26-28, September 24-26, 2001. 2001. A. Röder E. Newson, P. Hottinger, F. von Roth, T.B. Truong Energy-Planning Models as a Tool for the Catalyst Development for a No-NOx Natural Gas- Assessment of Car Powertrains and Fuels Hydrogen-Air Burner with Ignition at Room Annual Conference SAEE, Zürich, October 17, 2001. Temperature 3rd European Workshop on Environmental Catalysis, M. Saurer Maiori, Italy, May 2-5, 2001. 14C and 13C Measurements In Tree Rings of Quercus Ilex at a Natural C02 Spring E. Newson Ecologie et Ecophysiologie Forestières, INRA Centre Low Temperature Reforming (POX) and Preferential de Nancy, France, September 5, 2001. Oxidation Catalysts (PROX) for Liquid Energy Carriers DaimlerChrysler AG, Ulm/Donau, Germany, June 25, 2001. 173 M. Saurer P. Beaud, H.M. Frey*, T. Lang**, M. Motzkus** Tracing the Uptake of Carbon from a Natural C02 RET Scaling Analysis for Inelastic N2-N2 Collisions by Source fs CARS Institute of Botany, University of Basel, November 12, XX European CARS Workshop, Lund, Sweden, 2001. April 1-3, 2001. * now University of Berne B. Schnyder, R, Kötz, D, Alliata, P. Facci* ** Max Planck Institute, Garching, Germany Comparison of Azurin on Gold and on Native Silicon Oxide N. Bukowiecki, I. Polo, A.S.H. Prévôt, E. Weingartner, th ECASIA 01 (9 European Conference on Application U. Baltensperger of Surface and Interface Analysis), Avignon, France, Seasonal and Spatial Distribution of Atmospheric September 30 - Oktober 5, 2001. Aerosols and Gaseous Compounds in the Zurich Area * IN FM, Viterbo, Italy Measured by a Mobile Laboratory 8th European Symposium on the Physico-Chemical M. Steinbacher, J. Dommen, A.S.H. Prévôt, Behaviour of Air Pollutants, Torino, Italy, September C. Ammann*, A. Neftel* 17-20, 2001. Measurements of Oxygenated Hydrocarbons in Ambient Air with Proton-Transfer-Reaction Mass W. Durisch, M. Leutwyler* Spectrometry (PTR-MS) Efficiency and Spectral Sensitivity of a Copper Indium Como, Italy, October 5-7, 2001. Gallium Diselenide Solar Module * IUL Bern Sharjah Solar Energy Conference, Sharjah, UAE, February 19-22, 2001. E. Weingartner, M. Gysel, S. Henning, * ETH Zurich U. Baltensperger Measurement of Hygroscopicity of Aerosol Particles at W. Durisch, B. Bitnar, J.-C. Mayor, F. von Roth, Low Temperatures H. Sigg, H.R. Tschudi, G. Palfinger th 20 Annual AAAR Conference, Portland, Oregon, Progress in the Development of Small USA, October 15-19, 2001. Thermophotovoltaic Systems 17th European Photovoltaic Solar Energy Conference C. Wieckert and Exhibition, Munich, Germany, October 22-26, Solar ZnO Reduction and the ZnO-Zn Cycle for Solar 2001. Electricity Production Weizmann Institute of Science, Rehovot, Israel, H.M. Frey*, P. Beaud, T. Lang**, M. Motzkus** March 27, 2001. High Resolution Femtosecond CARS Spectroscopy Vth Femtochemistry Conference, Toledo, Spain, POSTERS September 2-6, 2001. * now University of Berne B. Andreaus, G.G. Scherer, A.J. McEvoy* ** Max Planck Institute, Garching, Germany Analysis of Performance Losses in Polymer Electrolyte Fuel Cells at High Current Densities by A.B. Geiger, T. Rager, L. Matejcek*, G.G. Scherer, Impedance Spectroscopy A. Wokaun 5th Int. Symposium on Electrochemical Impedance Radiation-Grafted Membranes for Application in Direct Spectroscopy, Marilleva, Italy, June 17-22, 2001. Methanol Fuel Cells * EPF Lausanne 1st European PEFC Forum, Conference, Luzern, July 2-6, 2001. B. Andreaus, A.J. McEvoy*, G.G. Scherer * Adam Opel AG, Rüsselsheim, Germany Impedance Response of Polymer Electrolyte Fuel Cells at High Current Densities A.B. Geiger, E. Lehmann, P. Vontobel, G.G. Scherer, 1st European PEFC Forum, Luzern, Switzerland, July A. Wokaun 2-6, 2001. In-Situ Investigation of Carbon Dioxide Patterns in * EPF Lausanne Anode Flow Fields of Direct Methanol Fuel Cells by Neutron Radiography U. Baltensperger, N. Bukowiecki, M. Gysel, 1st European PEFC Forum, Conference, Luzern, S. Henning, S. Nyeki, N. Streit, E. Weingartner July 2-6, 2001. Aerosol Measurements Within the WMO Global Atmosphere Watch Program: A Tool for the V.M. Graubner*, M. Hauer, R. Jordan*, T. Lippert, Quantification of Aerosol Forcing on Climate O. Nuyken*, B. Schnyder, A. Wokaun Lausanne, Switzerland, AGS 2001 Annual Meeting, Incubation and Ablation Behaviour of January 14-17, 2001. Polydimethylsiloxane for 266 Nm Irradiation COLA'01, Tsukuba, Japan, October 2001. * TU München, Germany 174 P. Griebel, R. Bombach, W. Kreutner, A. Inauen, M. Keunecke, M. Brack, A. Frey, P. Häberling, R. Schären, M. Witt, K. Herrmann* A. Meier, R. Palumbo, D. Wuillemin, A. Steinfeld Untersuchung zur Stabilität und Struktur von turbu• Solar Thermal Dissociation of ZnO - lenten Methan/Luft- Vormischflammen Solar Furnace and Laboratory Experimentation VDI-Tagung Verbrennung und Feuerungen - ETSF2 - Transitions to Solar Hydrogen, PSI, 20. Deutscher Flammentag, April 4-5, 2001. November 23, 2001. * ETH Zürich H. Kiess, W. Durisch C. Guesdon, T. Frey, M. Sturzenegger Orientation of Photovoltaic Panels to the Elevation of Kinetic Investigations on the Solar Thermal the Sun: Are Fewer Cells Required? Reductions of Cobalt Iron Oxides 17th European Photovoltaic Solar Energy Conference GDCh Jahrestagung Chemie, Symposium der and Exhibition, Munich, Germany, October 22-26, Fachgruppe Festkörperchemie und Materialforschung, 2001. Würzburg, Germany, September 23-29, 2001. G. Knopp, P. Beaud, P.P. Radi, M. Tulej, T. Gerber M. Halmann*, A. Frei. A. Steinfeld Femtosecond Photoionization of the Ethyl Radical Avoidance of Carbon Dioxide Release by Combining C2H5 Metal Oxide Reduction with Methane Partial Oxidation Vth Femtochemistry Conference, Toledo, Spain, in a Thermo-neutral Process September 2-6, 2001. ICCDU 6th International Conference on Carbon Dioxide Utilization, Breckenridge, USA, September D.N. Kozlov, B. Hemmerling 9-14, 2001. Application of Laser-Induced Grating Technique * Weizmann Institute of Science, Rehovot, Israel for Studies of Energy Relaxation in Electronically Excited 02 M. Hauer, J.T. Dickinson*, S.C. Langford*, T. Lippert, 20th European CARS Workshop, Lund, Sweden, A. Wokaun April 1-3, 2001. Influence of the Irradiation Wavelength on the Ablation Process of Designed Polymers D.N. Kozlov, B. Hemmerling COLA'01, Tsukuba, Japan, October 2001. Simultaneous Measurements of Flow Velocity and * Washington State University, USA Temperature Using Laser-Induced Electrostrictive Gratings B. Hemmerling, A. Stampanoni, H.K. Kammler*, 20th European CARS Workshop, Lund, Sweden, S.E. Pratsinis* April 1-3, 2001. CARS Temperature Measurements in Flames used for Electrically Assisted Particle Synthesis D.N. Kozlov, B. Hemmerling 20th European CARS Workshop, Lund, Sweden, Aspects of Gas Diagnostics Using Laser Induced April 1-3, 2001. Gratings: Role of Energy Relaxation Processes * ETH Zürich Gordon Research Conference: Laser Diagnostics in Combustion, Holyoke, MA, USA, July 2-6, 2001. B. Hemmerling, D.N. Kozlov, M. Neracher Flow Velocity Measurements by Laser-Induced S. Kräupl, M. Brack, P. Häberling, C. Wieckert, Electrostrictive Gratings D. Wuillemin, A. Steinfeld Gordon Research Conference: Laser Diagnostics in SynMet: a Solar Chemical Reactor for the Co- Combustion, July 2-6, 2001. Production of Zinc and Syngas ETSF2 - Transitions to Solar Hydrogen, PSI, D. Hirsch*, A. Steinfeld November 23, 2001. Hydrogen Production by Solar Thermal Decomposition of Natural Gas S. Kypreos, R.A. Krakowski ETSF2 - Transitions to Solar Hydrogen, PSI, Mapping Energy-Economy-Environment Paths to November 23, 2001. Sustainable Futures in China * ETH Zürich AGS Annual Meeting at EPF Lausanne, "Shaping the Future - Tools for Sustainable Development", January A. Inauen, T.B. Gradinger, R. Bombach, B. Käppeli, 14-17, 2001. K. Boulouchos, W. Hubschmid Fuel-Oil Concentration in a Gas Turbine Burner S. Kypreos, O. Bahn Measured with Laser-Induced Fluorescence The MERGE Model with Endogenous Technological Gordon Research Conference: Laser Diagnostics in Change Combustion, July 2-6, 2001. AGS Annual Meeting at EPF Lausanne, "Shaping the Future - Tools for Sustainable Development", January J. Keller, C. Borel* 14-17, 2001. Preliminary Comparison of the MISR Aerosol Product and Sunphotometer Data for a Region in Central Europe Pasadena, CA, USA, MISR Science Team Meeting, June 4-6, 2001. * Los Alamos National Laboratory, NM, USA 175 A. Meier, E. Bonaldi*, G.M. Celia*, W. Lipinski, P.P. Radi, A.P. Kouzov R. Palumbo, A. Steinfeld, C. Wieckert, D. Wuillemin Measurements of Rotational Energy Transfer Rates in Solar Thermal Production of Lime Combustion Processes Using Two-Color Resonant ETSF2 - Transitions to Solar Hydrogen, PSI, Four-Wave Mixing November 23, 2001. Gordon Research Conference: Laser Diagnostics in * QualiCal, Bergamo, Italy Combustion, South Hadley, MA, USA, July 1-6, 2001. M.J. Montenegro, T. Lippert, S. Mueller, T. Rager, J. Huslage, C. Noirtin, P. Muff, G.G. Scherer A. Weidenkaff*, P. Willmott, A. Wokaun Lösungsmitteleinfluss bei der Herstellung strahlen• Pulsed Laser Deposition of Electrochemical Active gepfropfter Polymerfilme Perovskite Films Makromolekulares Kolloquium, Freiburg, Germany COLA'01, Tsukuba, Japan, October 2001. February 22-24, 2001. * University of Augsburg, Germany R. Raimondi, K. Geissler, J. Wambach, A. Wokaun E. Newson, T.B. Truong, R. Vangheluwe, N. De Silva Hydrogen Production by Methanol Reforming: Post- Preferential Oxidation (PROX) Catalysts for Reaction Characterisation of a Cu/Zno/AI203 Catalyst Reformates from Methanol and Hydrocarbons byXPSandTPD EuropaCat V, Symposium 8, Env. Catalysis 2, Fall Meeting of the Swiss Chemical Society, University 8-P-07, Limerick, Ireland, September 2-7, 2001. of Zürich, October 12, 2001. E. Newson, T.B. Truong, T.J. Schildhauer, A. Fleury M. Saurer, F. Schweingruber*, E.A. Vaganov**, Low Temperature Catalytic Partial Oxidation and S.G. Shiyatov***, R.T.W. Siegwolf Reforming of Hydrocarbons (C-¡ to C10) for Hydrogen Oxygen and Carbon Isotope Trends Along the Production Northern Tree-Line in Eurasia Energy Technologies for a Sustainable Future International Conference on the Future of (ETSF 2), PSI, November 23, 2001. Dendrochronology, Davos, September 22-26, 2001. * WSL Birmensdorf S. Nyeki, G. Coulson*, I. Colbeck*, K. Eleftheriadis**, ** Institute of Forest, Siberian Branch of the U. Baltensperger, R. Hillamo***, K. Teinila***, Russian Academy of Science, Krasnoyarsk, F. Stordal****, J.H. Wesseng****, B.A. Karstad****, Russia H.J. Beine*****, I. Allegrini*****, L. Ammiraglia*****, *** Institute of Plant and Animal Ecology, Ural A. lanniello*****, F. DiBari*****, R. Sparapani***** Branch of the Russian Academy of Science, Aerosol Volatility Measurements in the Arctic: Ekaterinburg, Russia Preliminary Measurements from the NICE (Nitrogen Cycle and Effects) Campaign T. Schildhauer, E. Newson, A. Wokaun American Association for Aerosol Research, Portland, Improvement of the Heat Transfer in Catalytic Fixed USA, October 15-19, 2001. Bed Reactors by Means of Structured Packings * University of Essex, England ICOSCAR-1, Delft, The Netherlands, October 21-24, ** NCSR Demokritos, Greece 2001. *** FMI, Finland **** NILU, Norway R.T.W. Siegwolf, M. Saurer, Y. Scheidegger *****CNR-IIA, Italy Linking Stable Oxygen and Carbon Isotopes with Stomatal Conductance and Photosynthetic Capacity G. Palfinger, B. Bitnar, W. Durisch, J.-C. Mayor, New Phytologist - Stomata 2001 Conference, D. Grützmacher, J. Gobrecht Birmingham, UK, July 26-28, 2001. Cosf Estimates of Electricity from a TPV Residential Heating System R.T.W. Siegwolf, M. Saurer, Y. Scheidegger 17th European Photovoltaic Solar Energy Conference Characterizing Long-Term Gas Exchange Responses and Exhibition, Munich, Germany, October 22-26, with the Stable C and O Isotopes 2001. Jahrestagung der Gesellschaft für Ökologie, Basel, August 27- 30, 2001. U.A. Paulus, T.J. Schmidt*, V.R. Stamenkovic*, N.M. Markovic*, P.N. Ross* M. Steinbacher, J. Dommen, A.S.H. Prévôt, Oxygen Reduction Activity of Pt and Pt-Alloys in Acid C. Ammann*, A. Neftel* Electrolyte Aldehydes Measurements in Ambient Air with Proton- 1st European PEFC Forum, Luzern, Switzerland, July Transfer-Reaction Mass Spectrometry (PTR-MS) 2-6 2001. ALDEHYDES 2001 Conference, Münster, Germany, June 6-8, 2001. * Lawrence Berkeley National Laboratory, CA, USA * IUL Liebefeld, Bern A.S.H. Prévôt, R. Weber Trends of Ozone in Southern Switzerland in the 1990s 8th European Symposium on the Physico-Chemical Behaviour of Air Pollutants, Torino Italy, September 17-20, 2001. 176 S. Szidat*, H.W. Gaeggeler, H.-A. Synal**, G. Bonani, M. Coluccia, R. Nesper*, P. Novák U. Baltensperger Electrode Material for Positive Electrodes of Radicarbon (1 C) Measurements on Particulate Rechargeable Lithium Batteries Organic Carbon in the Lower Troposhere Patent application No. WO 01/41238 A1, 2001. Cologne, Germany, EUROTRAC-AEROSOL * ETH Zürich Workshop 2001, March 21-22, 2001. * University of Bern W. Hoffelner*, A. Steinfeld, D. Wuillemin, A. Meier, ** ETH Zürich B. Schaffner Reaktor zur Nutzung von solarer Strahlungswärme K. Tomita*, T. Tada*, H. Masuhara*, T. Lippert Schweizerische Patentanmeldung Nr. 1240/01, July 5, Laser-Induced Decomposition and Ablation Dynamics 2001. of Triazene and its Crosslinking Polymer Films * RWH Consult GmbH, Oberrohrdorf AG Studied by Nanosecond Interferometry COLA'01, Tsukuba, Japan, October 2001. R. Petricevic*, R. Sauger*, H. Pröbstle*, P. Novák, * Osaka University, Japan J. Fricke* Verfahren zur Herstellung einer offenporigen mono• M. Tulej, M.V. Pachkov*, T. Pino*, J.P. Maier* lithischen Elektrode aus Kohlenstoff für den Einsatz Structure and Spectroscopy of C3H~ Revealed by in einer reversiblen Lithium-Ionen-Batterie Photodetachment Studies in the Vicinity of the Lowest Patent application No. DE 199 38 822 A1, 2001. Photodetachment Threshold * University of Würzburg, Gemany 26th International Symposium on Free Radicals, Assisi, Italy, September 1-7, 2001. A. Steinfeld, M. Halmann* * University of Basel Verfahren zur thermoneutralen Reduktion von Metalloxiden zu Metallen durch gleichzeitige partielle E. Weingartner, M. Gysel, S. Henning, Oxidation von Kohlenwasserstoffen U. Baltensperger Schweizerische Patentanmeldung Nr. 1213/01, July 5, A New H-TDMA for the Investigation of the 2001. Hygroscopicity of Aerosol Particels at Low * Weizmann Institute of Science, Rehovot, Israel Temperatures Cologne, Germany, EUROTRAC-AEROSOL CONFERENCES, WORKSHOPS & EXHIBITIONS Workshop 2001, March 21-22, 2001. F.N. Büchi, G.G. Scherer, A. Wokaun (Organizers) P. von Zedtwitz*, A. Steinfeld Ist European Polymer Electrolyte Fuel Cell Forum Hydrogen Production by Solar Thermal Gasification of Luzern, Switzerland, July 2-6, 2001. Coal ETSF2 - Transitions to Solar Hydrogen, PSI, O. Haas , R. Kötz November 23, 2001. Elektrochemie und Synchrotronstrahlung * ETH Zürich 16. Tagessymposium Elektrochemische Energiespeicherung, PSI Villigen, October 23, 2001. C. Wieckert, A. Meier, R. Palumbo, A. Steinfeld Solar Fuels Based on ZnO/Zn Reactions P. Häberling ETSF2 - Transitions to Solar Hydrogen, PSI, Zink speichert Sonnenenergie November 23, 2001. Zürcher Festival des Wissens, Zürich, May 4-7, 2001. J. Wambach, A. Wokaun P. Häberling In Situ Catalysis Research Using an Extended Solarofen und Solarreaktoren Application of DRIFT Spectroscopy Solarofen-Workshop für Erfinder- und 75* International Bunsen Discussion Meeting; Patentinhaberverband der Schweiz EVS, PSI, Analysis and Modelling of Heterogeneous Catalytic September 28, 2001. Processes; Fritz-Haber-lnstitute of the Max-Planck Society, Berlin, Germany, March 12-14, 2001. J. Keller 5th GLOREAM Workshop J. Wambach, A. Wokaun, A. Hiltpold Wengen, September 24-26, 2001. Oxidation of Stainless Steel under Dry and Aqueous Conditions: Oxidation Behaviour and Composition H. Lutz, Chr. Ludwig, A. Schuler, T. Figilister, 9th European Conference on Applications of Surface J. Wochele, S. Stucki, S. Biollaz and Interface Analysis, ECASIA'01, Avignon, France, Recycling of Heavy Metals September 30 - October 5, 2001. Zürcher Festival des Wissens, Zürich, May 4-7, 2001. PATENT APPLICATIONS S. Stucki, A. Steinfeld B. Bitnar, W. Durisch, G. Palfinger ETSF2: Energy Technologies for a Sustainable Future Thermophotovoltik-System Transitions to Solar Hydrogen Schweizerische Patentanmeldung Nr. 01 512/01, PSI Villigen, November 23, 2001. August 16, 2001. 177 MEMBERSHIPS IN EXTERNAL COMMITTEES F. Gassmann Naturama, Aarau S. Andreani-Aksoyoglu Air Pollution 2001 Vice President of Geschäftsleitung Scientific Advisory Committee Member F. Gassmann Naturforschende Gesellschaft in Zürich S. Andreani-Aksoyoglu President of editing committee of Vierteljahrsschrift, Air Quality Management Symposium Neujahrsblatt and treasurer Scientific Advisory Committee F. Gassmann Member Maturakommission für die Kantonsschulen Baden und Wohlen U. Baltensperger Center of Excellence in Analytical Chemistry, Experte für Mathematik und Physik ETH Zürich Board of Directors T. Gerber Towards Clean Diesel Engines U. Baltensperger Steering Committee BMBF Förderschwerpunkt Aerosolforschung, T. Gerber Germany IEA Implementing Agreement on Energy Conservation Expert and Emissions Reduction in Combustion Task Leader U. Baltensperger Gesellschaft für Aerosolforschung W.K. Graber Secretary General Kommission für Klima und Atmosphärenforschung (CCA) der Schweizerischen Akademie der U. Baltensperger Wissenschaften (SANW) Journal of Aerosol Science Vice president Editorial Board O. Haas U. Baltensperger Electochimica Acta Scientific Advisory Group for Aerosol Within Global Advisory Board Atmosphere Watch Chairman O. Haas Journal of New Materials for Electrochemical Systems U. Baltensperger and International Symposium on New Materials for Swiss Committee of Global Atmosphere Watch Electrochemical Systems Member Advisory Board U. Baltensperger O. Haas 13th Int. Congress of the International Society for Symposium China International Battery Fair Aerosolos in Medicine, Interlaken Advisory Board Organizing Committee Chr. Ludwig U. Baltensperger Scientific Panel of the R'2002 Congresse Atmospheric Chemistry and Physics Member of the Scientific Panel Editorial Board P.P. Radi W. Durisch European Conference on Nonlinear Optical Prüfungskommission für die Lehrlinge des Laborantenberufes des Kantons Zürich Spectroscopy Fachexperte Steering Committee W. Durisch G.G. Scherer International Energy Foundation, IEF Neuartige Schichtstrukturen für Brennstoffzellen Advisory Committee Member and Under Secretary Deutsche Forschungsgemeinschaft, Mitglied der Science and Technology Prüfungsgruppe für das Schwerpunktprogramm W. Durisch G.G. Scherer UNESCO, World Renewable Energy Congress European Fuel Cell Forum Member Advisory Board Steering Committee Member G.G. Scherer M. Furger Fuel Cell Handbook Meteorologische Zeitschrift Member Advisory Board Editor 178 G.G. Scherer A. Wokaun Beirat Forschungsallianz Brennstoffzellen Wissenschaftlicher Beirat des Hahn-Meitner-Instituts, Baden Württemberg Berlin, Germany Deputy Speaker Mitglied G.G. Scherer A. Wokaun MISTRA, The Swedish Foundation for Strategie European Climate Forum Environmental Research Member of Council Member International Advisory Board (Audit on Fuel Cells, Batteries) A. Wokaun Strategie Nachhaltigkeit des ETH-Rates A. Steinfeld Mitglied des Leitungsausschusses Energy—The International Journal Associate Editor A. Wokaun Forum für Wissenschaft und Energie A. Steinfeld Vorstandsmitglied ASME - Journal of Solar Energy Engineering Associate Editor AWARDS A. Steinfeld S. Andreani-Aksoyoglu Thomas Kuhn Award by the International Union of Air International Journal of Photoenergy Pollution Prevention & Environmental Protection Associate Editor Associations and the International Academy of Science A. Steinfeld International Energy Agency SolarPACES W. Durisch, B. Bitnar, J.-C. Mayor, F. von Roth, Operating Agent H. Sigg, H.R. Tschudi, G. Palfinger Poster Award A. Steinfeld Progress in the Development of small ASME's Solar Chemistry Committee Thermophotovoltaic Systems Chair 17th European Photovoltaic Solar Energy Conference and Exhibition, Munich, Germany, October 22-26, S. Stucki 2001. SNF Priority Programme Environment Coordinator of Integrated Project Waste A.B. Geiger Christian Friedrich Schönbein Bronze Medal S. Stucki Poster award Expertengruppe KVA Ticino In Situ Investigation of Carbon Dioxide Patterns in Member Anode Flow Fields of Direct Methanol Fuel Cells by Neutron Radiography. S. Stucki 1st European Polymer Electrolyte Fuel Cell Forum R'2002 (Recovery, Recycling, Re-integration) Luzern, Switzerland, July 2-6, 2001. Congress Member of the Scientific Panel A. Wokaun Schweiz. Akademie der Technischen Wissenschaften (SATW) Einzelmitglied feeding of CH4; 3) Runs VII and VIII used same feed• it ing conditions as Runs ll-VI, with an additional CH4 « flow via the same pipe as in run I. £ 18% 1_ The zinc yield, defined as the amount of Zn produced divided by the maximum amount of Zn that would have been recovered if the reaction had gone to com• pletion, was 100 % for every experiment. The conver• T/K sion of CH4 increased with temperature and reached