Transparent Insulation
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TRANSPARENT INSULATION IN SOLAR ENERGY CONVERSION FOR BUILDINGS AND OTHER APPLICATIONS Proceedings of the 2nd International Workshop held in Freiburg, F.R.G. on 24 - 25 March 1988 Edited by L. F. Jesch Published in 1988 by The Franklin Company Consultants Ltd. for the DEUTSCHE SEKTION DER INTERNATIONALEN GESELLSCHAFT FOR SONNENENERGIE ( ISES) e. V. German Section of the International Solar Energy Society- ISES TABLE OF CONTENTS WORKSHOP SERIES INFORMATION 0 INTRODUCTION A. Goetzberger l.S.E., Freiburg MATERIALS Transparent insulation materials V. Wittwer l. S.E., Freiburg 2 Optimization of transparently covered fibrous insulations R. Caps University of Wu rzburg 5 Hollow glass spheres in making fluorpolymer bonded transparent insulation H. Fitz Hoechst AG 8 P-Layer insulation (P-Folienplatte) a new transparent thermal insulation material R.W. Peter Peter-Consulting, Zurich 9 Calculation of thermal conductivities from spectral data A. Pfluger l. S. E., Freiburg 12 Optimization problems of transparently insulated systems W. Platzer l.S.E., Freiburg 14 SYSTEMS AND COMPONENTS Aerogel window panes - energy savings in houses N. B. Andersen Tech. Institute, Denmark 17 HITH Energy saving double window with co ntrol of solar transmission using special blinds H. J. GUiser lnterpane, Lauenforde 20 Highly insulated window systems with controllable performance H. F. 0. MO iier Fachhochschule Ka in 24 Integrated solar element (ISE) - collector, storage, radiator- for heating and hot water systems W. Balk Gesamthochschule Ka ssel 27 Test results and optimisation of integrated collector storage with a transparent insulation cover Ch. Schmidt l.S.E., Freiburg 29 Energy saving coatings on flexible substrates W. MOiier Renker GmbH, Freiburg 32 A new thermo-optical regulation system - suited for transparent insulation ? E. Boy Fraunhofer Inst., Stuttgart 35 Transparent insulation for high temperature flat plate collectors B. Karlsson Alvkarleby Lab., Sweden 39 INVITED KEYNOTE ADDRESS Designing honeycombs for minimum material and maximum transmission K. T. Hollands Uni. Wa terloo, Canada 40 SIMULATION Heat loss through honeycomb transparent insulation J. Chattha Uni. Birmingham 43 Comparison of measurements on transparent thermal insulation systems with numerical simulations of building envelopes E. Boy Fraunhofer Inst., Stuttgart 46 A simple method for the estimation of energy savings through application of transparent insulation materials B. Alexa Buro energiegerechtes Bauen 50 Analysis of over-heating of wall structures in transparent insulation applications L. Jankovic Energy Engineering, B'ham 53 ARCHITECTURAL ASPECTS Constructional and architectural aspects of facades using transparent insulation materials B. Alexa Buro Energiegerechtes Bauen 56 Application of transparent thermal insulation to existing houses K. Brandstetter Universitat Stuttgart 59 Case studies on the practical applicablitiy of transparent thermal insulation to different types of residential estates in Stuttgart K. Bertsch Fraunhofer Inst. Stuttgart 62 PLANNED PROJ ECTS Market potential for transparent insulation materials for housing in the UK P. Hurd Energy Engineering, B'ham 65 A low-energy air-heated solar house with transparent insulation L. F. Jesch Energy Engineering, B'ham 68 Retrofit of an old 8 family house by transparent wall insulation E. Bollin l.S. E., Freiburg 71 Self-sufficient Solar House 2000 A. Goetzberger l.S. E., Freiburg 74 CONCLUSION L.F. Jesch Energy Engineering, B'ham 77 AUTHOR INDEX 79 INTERNATIONAL WORKSHOPS ON TRANSPARENT INSULATION 1. Transparent insulation materials for passive solar energy utilization Freiburg, FRG, 27 -28 November 1986 2. Transparent Insulation in solar energy conversion for buildings and other applications Frelburg, FRG, 24 -25 March 1988 3. Transparent insulation technology for solar energy conversion Freiburg, FRG, 18-19 September 1989 4. Transparent insulation technology Birmingham, UK 1991 For further information contact: Professor A. Goetzberger OR Dr. L. F. Jesch Fraunhofer lnstitut Energy Engineering (Birmingham) Ltd. fOr Solare Energiesysteme 192 Franklin Rd. Oltmannsstr. 22, D-7800 Freiburg, FRG Birmingham B30 2HE, UK .nm�;;:;; �.,;;,,,;;,;;;,,;,;;,n;;.1 The Proceedings of this series of workshops are published by : I The Franklin Company Consultants Ltd., 192 Franklin Rd., Birmingham B30 2HE, UK �: � � · Telephone: (0)21 459 4826 Telefax: (0)21 459 8206 Telex: 338 938 s PH ti: _ , . "" '"''"J 0 INTRODUCTION Professor A. Goetzberger Fraunhofer Institute for Solar Energy Systems Oltmannstrasse 22, D-7800 Freiburg Federal Republic of Germany Sixteen month ago we had the first international workshop on transparent insulation materials for passive solar energy utilisation. That first gathering in Freiburg made us realise that there is a strong international, mainly European, interest in the subject and that a large portionof the initial research and development work was being carried out in West Germany. The Fraunhofer Institute for Solar En ergy Systems has been investigating the properties and applications of transparent insulation materials for some years and it organised the the first two workshops under the auspices of the German Sec tion of the International Solar Energy Society. The second workshop was held on 24 - 25 March 1988 and its theme was transparent insulation materials in solar energy conver sion for buildings and other applications. More and better prepared papers were presented this time as all of us working in the field of transparent insulation learned more since 1986 and were able to see the directions our research should go into more clearly. Amongst the 26 presentations Canada ( 1), Denmark ( 1), Sweden ( 1), Switzerland (1 ), Great Britain (4) and West Germany (18) were represented. We listened with great interest to the invited keynote address delivered by Professor Terry Hollands from the University of Water loo, one of the earliest pioneers of heat transfer in honeycombs and transparent insulation materials. There were five broad areas around which the presentations and discussions were focussed: materials, systems and compo nents, simulation, architectural aspects, planned projects. This struc ture in itself was a small shift from that of the first workshop repre senting the changes of emphasis in the most recent work. There were papers presented from the same research groups and even by the same people as in 1986 reporting on most recent advances, but there were also new contributors some from new areas of activity, not represented before. Every session had a discussion period built into it which was always used to the full extent. The closing session of the workshop provided an opportunity to evaluate our efforts and to get feedback from the delegates. By ma jority consensus we decided that the third transparent insulation workshop will be held in the late summer of 1989 in Freiburg and that the fourthworkshop will be held in the Spring of 1991 in Birmingham. During the technical sessions of the workshop we enjoyed the hospitality of the University of Freiburg and the City of Freiburg gave a civic reception to all participants in the historic building of the City Hall where the Deputy Mayor gave a welcoming address. The burden of the preparation of the technical sessions was on Dr. V. Wittver and of the organisation of all details was on Dr. W. Stahl. The publicity, printing and publication was the responsibility of Ms. A. Pollock. They all worked hard and brought success to the workshop. As co-chairmen: Dr. Jesch and I are grateful to them. 1 Transparent insulation materials V. Wittwer Fraunhofer-lnstitut tarSo/are Energiesysteme Oltmannsstrasse 22, 0- 7800 Freiburg, FR G Abstract Transparent insulation materials are characterized by physical properties which place them in a different class to both opaque insulation materials and conventional transparent systems. From - -- --the geometrical-point-of-view,-four different-types-can be-distinguished. -- - Introduction Transparent insulation materials are characterized by two physical properties. The first one is the solar transmittance T , which sometimes has to be extended to the total energy trans- " mittance g and the other one is the thermal heat loss coefficient u or the thermal conductivity A.. Both values are sensitive to a large number of variables which have to be defined exactly to get comparnble results. Different types of materials From the geometrical point of view, four different types of materials can be distinguished: structures parallel to the absorber (multiple glazings) structures perpendicular to the absorber (honeycomb, capillary) scattering structures (foams, bubbles, fibres) homogeneous materials (aerogel) (fig. 1). For all of these materials, specifically modified theories are necessary to describe their physical characteristics /1 /2/3/. Most of these structures can be made from different materials such as glass or plastic, and can be filled with different gases or evacuated. Solar transmittance and total energy transmission As mentioned above, the characteristic data of such a material are dependent on a large num ot vanaores. The totai soiar transmittance T can be given by the doubie integrai: oer . T (A,y?) l(A,y?) dAdy? T = ff e l(A.,y?) dA.dy? ff where A denotes the wavelength and y? the angle of incidence and l(A,y?) is the incident in tensity as a function of both of these variables. The spectral transmittance T (A,y?)is dependent on the material itself and the geometry, while the incoming radiation