Environmental Assessment of the CIESOL Solar Building After Two

Environ. Sci. Technol. 2010, 44, 3587–3593

increase comfort (6, 7). Up to date, many theoretical and Environmental Assessment of the pilot-scale studies have been published dealing with HVAC CIESOL Solar Building after Two systems powered with solar energy (8, 9), but few examples of full-scale operative installations exist (7). In this context, Years Operation the Solar Energy Research Centre (CIESOL), located at the Campus of the University of Almerı´a (Spain), constitutes an

† outstanding example of energy efficiency, since a solar- FRANCISCO J. BATLLES, assisted HVAC was installed in the building with the purpose SABINA ROSIEK,† IVAN MUN˜ OZ,*,‡ AND of covering its heating and cooling demand. Furthermore, AMADEO R. FERNANDEZ-ALBA´ ‡,§ photovoltaic electricity is used to power the HVAC system’s Department of Applied Physics, University of Almerıá, ctra. de equipment. Sacramento s/n, 04120, Almerıá, Spain, Department of One of the main motivations for installing a solar HVAC Hydrogeology and Analytical Chemistry, University of Almerıá, system lies in its environmental friendliness, based on a low ctra. de Sacramento s/n, 04120, Almerıá, Spain, and Instituto fossil-fuel demand and the avoidance of refrigerants causing Madrilenõ de Estudios Avanzados - IMDEA Agua, Edificio ZYE, Parque Cientı´fico Tecnolo´gico de la U. de Alcala´, Alcala´ ozone layer depletion and greenhouse effect. Nevertheless, de Henares, 28805 Madrid, Spain the environmental performance of processes can not be taken for granted and must be objectively assessed, especially when dealing with technologies in an early stage of development. Received September 7, 2009. Revised manuscript received In addition, environmental assessments should not focus February 28, 2010. Accepted March 8, 2010. on a single dimension or aspect, for example, CO2 emissions or energy consumption, since many other aspects can be important from an environmental point of view. In the case Life cycle assessment is applied to assess the environmental of Spain, for example, freshwater resources are scarce and should be taken into account in any technology design. benefits and trade-offs of a solar-assisted heating, ventilating, Life cycle assessment (LCA) (10) represents a compre- and air-conditioning (HVAC) system installed in the CIESOL hensive approach to examining the environmental impacts building in Almerıá (southeastern Spain). The environmental of products and processes, including buildings. LCA is a performance of this system is compared to that of a conventional method characterized by a “cradle-to-grave” approach HVAC system using a heat pump. The study evaluates these whereby the material and energy flows of a system are systems from cradle to grave, and the impact assessment includes, quantified and evaluated, including upstream, use and in addition to the CML2001 method, an impact category downstream flows. Besides, different environmental impacts dealing with impacts on freshwater resources. The results can be assessed, like greenhouse effect, ozone depletion, show that the solar-assisted HVAC involves lower impacts in and acid rain, among others. Recently, some approaches for many impact categories, achieving, as an example, a reduction LCA to assess impacts on freshwater resources have been developed (11, 12). Therefore LCA can be considered a of 80% in greenhouse-gas emissions. On the other hand, key powerful tool to assess the overall environmental benefits of weak points of this system are the production of capital goods, a solar-powered building, as well as to identify potential but specially water use for cooling, due to its high impact on environmental trade-offs and weaknesses to take into account freshwater resources. Minimization of water requirements should in further development of this technology. We assessed the be a priority for further development of this promising solar-assisted HVAC installed in the CIESOL building by technology. means of LCA, as compared to a conventional HVAC using a heat pump. 1. Introduction 2. Building and HVAC Description The building sector represents a lions share in terms of energy CIESOL is situated at the Campus of University of Almerıá, consumption and CO emissions in industrialized countries. 2 a region in southern Spain with Mediterranean climate. In Europe and the U.S., it is recognized that they account for Almerıá presents an average annual global, diffuse, and direct around 40% of energy consumption and CO emissions (1, 2), 2 normal radiation levels of 1805, 527, and 1977 kWh per m2, and they have been found to be responsible of 20-35% of and an average annual temperature of 19 °C. the environmental impacts associated with consumption in This building (Figure 1a) has been constructed with the European Union (3). For this reason, many national and bioclimatic standards, aiming at using energy efficiently. It international energy policies aiming at the reduction of CO 2 is oriented along southeast axis with internal access corridors emissions are addressed to decreasing building energy and a big internal nave. It comprises an area of 1100 m2 with consumption, especially for heating, ventilation, and air 10 laboratories, five offices and one conference room. The conditioning (HVAC), since it has been shown that energy air-conditioning is in operation during office hours from consumed for these purposes is responsible of the largest 9 a.m. to 8 p.m., from Monday to Friday, providing a stable share of a building’s environmental impact (4, 5). temperature around 22 and 25 °C during the cooling and Passive and active solar architecture of buildings is heating seasons, respectively. The building operates during increasing in popularity as a means of designing and the day, resulting in a good matching in peak cooling loads constructing more energy-efficient buildings, as well as to with solar radiation availability. The solar-assisted HVAC system consists of a flat-plate * Corresponding author phone: +34-950-014139; fax: +34-950- collector’s array facing due south and tilted at an angle of 015483; e-mail: [email protected]. 30° to the horizontal line, with a total surface of 160 m2 (Figure † Department of Applied Physics, University of Almerıá. ‡ Department of Hydrogeology and Analytical Chemistry, Uni- 1a and c) a hot-water driven single-effect LiBr-H2O absorption versity of Almerıá. chiller (Yazaki), a cooling tower (Figure 1d), two hot water § Instituto Madrilenõ de Estudios Avanzados - IMDEA Agua. storage tanks with a capacity of 5000 L each, an auxiliary gas

10.1021/es9027088  2010 American Chemical Society VOL. 44, NO. 9, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3587 Published on Web 03/22/2010 FIGURE 1. (a) General view of the CIESOL building, (b) the nave with the main system’s equipment, (c) 160 m2 ﬂat-plate collector array and 69 m2 photovoltaic array, (d) heat pump (foreground), and cooling tower (background).

FIGURE 2. Schematic diagram of the solar-assisted and conventional HVAC systems. boiler, a plate heat exchanger, and the necessary peripheral order to ensure good thermal comfort inside the building in equipment, such as valves and pumps. This system also the event of failure of the solar-assisted HVAC, a conventional consists of a photovoltaic system installed on the building’s HVAC system, consisting of a Ciatesa Hidropack WE 360 heat roof with a capacity of 9.324 kWp. It has three rows, with 14 pump was installed (Figure 1d). It must be highlighted that modules each, with the same orientation as the collector’s the heat pump does not constitute a back-up but an array (Figure 1c, on top). Figure 2 shows a diagram of this alternative, independent system, which has been used only system, which has been operating since October 2006. In sporadically, since the solar-assisted system has been able

3588 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 9, 2010 FIGURE 3. Life-cycle phases and system boundaries for both alternatives.

FIGURE 4. Total weight of HVAC equipment installed in the CIESOL building. to cover the heating and cooling demand of the building kcal h-1) in the heating season, from November to March. during the year. The mean temperature of water leaving the Further details on the solar-assisted HVAC can be found solar collectors has always been above 75 °C during the in ref 13. cooling season, and above 60 °C during the heating season, in the range of similar systems (14). The monthly collectors’ 3. Application of LCA efficiency is around 30% in the cooling season and 50% in 3.1. Goal and Scope. The goal of this LCA study is to compare the heating season, fairly close to values reported by Sparber the environmental performance of two alternatives for et al. (15). Average values for the coefficient of performance covering the air heating and cooling requirements of the (COP) and the cooling capacity were calculated for summer Solar Energy Research Centre (CIESOL) building, located at months, obtaining values of 0.6 and 40 kW, respectively, which the campus of the University of Almerıá (Spain). These are in accordance with data from the absorption chiller alternatives are as follows: (a) Solar-assisted HVAC: cooling manufacturer (Yazaki) and similar to those reported by is achieved by means of the absorption chiller driven by the Thuer and Bukits (14). The overall heat demand of this solar collectors, whereas heating is achieved by exchanging system is 4.45 × 107 kcal (51 600 kcal h-1) in the cooling the heat absorbed by water in the solar collectors. Cooling season, from May to September, and 2.84 × 107 kcal (45 000 and heating eventually use the auxiliary gas boiler and (b)

VOL. 44, NO. 9, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3589 TABLE 1. Detailed Energy and Water Requirements Per Year for Both Alternativesa

system equipment consumption heating cooling total absorption chiller (0.21 kW) 0 181 181 kWh electric from PV 0 864 864 kWh electric from PV cooling tower(1 kW) 0 750 750 m3 deionized water auxiliary gas boiler (0.19 kW) 0 9311 9311 kWh thermal pump P1 (3 kW) 1896 2592 4488 kWh electric from PV solar-assisted HVAC pump P2 (3 kW) 0 2592 2592 kWh electric from PV pump P3 (1.5 kW) 948 1296 2244 kWh electric from PV fan coils (1.47 kW) 911 1270 2182 kWh electric from PV 3756 8796 12551 kWh electric from PV total 0 9311 9311 kWh thermal 0 750 750 m3 deionized water heat pump (27 kW) 17064 23328 40392 kWh electric from grid conventional HVAC fan coils (1.47 kW) 911 1270 2182 kWh electric from grid total 17976 24598 42574 kWh electric from grid a PV: photovoltaics.

Conventional HVAC using an electric-driven heat pump for HVAC requires almost 13 tons of infrastructure materials both air heating and cooling. and equipment, whereas the heat pump system needs an The LCA study covered the whole life cycle of both HVAC order of magnitude less materials. From this perspective, systems, namely production of the installed equipment and the solar-assisted HVAC is much more resource-intensive as its transport to the building site, operation, maintenance, far as the building boundaries are concerned. On the other and disposal. Construction and disposal of the building itself hand, during its operation the heat pump has a relatively was excluded, as well as any other building function outside high power demand. The application of LCA allowed us to air heating and cooling, such as providing electricity for find out whether or not a lower energy demand at the use lighting and laboratory equipment operation, or providing phase compensates for the energy and resources consumed hot water. Common elements to both systems were also to have a 13-ton installation. excluded, since they would not affect the comparison. This During operation, the solar-assisted HVAC needs deion- applies to fan coils, used to distribute hot/cold air through ized water to supply the cooling tower with and tap water the building. The number of units installed is the same under for cleaning of solar collectors and photovoltaic modules. the two scenarios assessed, and as a consequence their Eventually, natural gas is burned in the auxiliary boiler if the manufacture and disposal is excluded from the study. This water from the solar collector array outlet does not reach the does not apply to their energy consumption during operation, required temperature. The electricity needed for pumps, since the source of energy used is different according to each absorption cooling machine, etc., is supplied by the pho- alternative: photovoltaic or from the Spanish grid. tovoltaic modules. Concerning the heat pump, electricity Figure 3 show a diagram for each HVAC system and their from the grid is the only input needed during operation. This life cycle phases. As it can be seen in the figures, recycling electricity comes from the Spanish grid, which in 2007 of dismantled materials is excluded from the study. In “open- consisted of 62% production from thermal power plants using loop” recycling, the product system under study “connects” fossil fuels, 18% production from nuclear power plants, 10% with the system of the product incorporating the recovered production from hydropower, and 10% production from materials. A decision must be made on how to allocate the other renewable sources (wind, photovoltaic, biomass, and processes affecting both systems, namely production of primary materials, the recycling processes and the final TABLE 2. Withdrawal-to-Availability (WTA) Values Used in the disposal after “n” recycling cycles. In the present study we Study have applied the cutoff approach (16), whereby production of primary materials and disposal of the latter is allocated country/region WTAa source and comments to the product directly responsible for the extraction of these primary materials, whereas recycling is allocated to the Italy 0.232 Aquastat (23) Switzerland 0.050 Aquastat (23) product incorporating recycled materials. This choice has Japan 0.206 Aquastat (23) been made for coherence with the LCA database used in the Germany 0.306 Aquastat (23) study, Ecoinvent, which applies this allocation method (17). Spain 0.320 Aquastat (23) The functional unit or basis for the comparison of the obtained as total annual use and available resources from Belgium, Bulgaria, Czech solar-assisted HVAC with the heat pump HVAC was covering Republic, Denmark, Germany, Estonia, the CIESOL building with its heating and cooling require- Ireland, Greece, Spain, France, Italy, Cyprus, Latvia, Lithuania, Luxembourg, ments during one year. This corresponds to five months of Europe 0.105 Hungary, Malta, Netherlands, Austria, cooling (from May to September) and five months of heating Poland, Portugal, Romania, Slovenia, Slovakia, Finland, Sweden, United Kingdom, (from November to March), while during October and April Croatia, the former Yugoslav Republic of no air-conditioning is required and maintenance operations Macedonia, Turkey, Iceland, Norway and are usually carried out. Switzerland; values from Eurostat (24, 25) Almerıá 1.13 Andalusian Mediterranian water district (26) 3.2. Inventory Analysis. A detailed inventory of the HVAC Weighed average according to percentage systems was carried out. All the equipment installed and natural gas of imports to Spain from Norway, Trinidad their operation needs were identified and quantified con- imports to 1.13 and Tobago, Qatar, Oman, Algeria, Nigeria, Spain Egypt, Lybia and Equatorial Guinea. sidering the information from the equipment manufacturers. Values from Aquastat (27) Figure 4 compares on a weight basis the inventory of materials a Ratio of annual freshwater use to annual freshwater and equipment installed in the building in order for both resources. HVAC systems to operate. As it can be seen, the solar-assisted

3590 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 9, 2010 waste) (18). Apart from indirect emissions from electricity of unit processes involved in the product system. WTA is in production, direct emissions due to leakage of the R-410a turn calculated with eq 2): refrigerant were taken into account. Maintenance was taken into account in the study by considering the infrastructure WU WTA ) (2) and equipment renewal at the end of its lifetime. Dismantled WR materials are either sent for recycling or disposed of by means of incineration or landfilling. All processes, materials, equip- Where WU is the total annual freshwater withdrawal from ment, energy carriers, etc., were modeled in the LCA by means a defined area (river basin or country) and WR is the annual of the ecoinvent database v.2.1 (19) implemented in the freshwater availability in that same area. The application of software Simapro v.7 (20). the FEI method required knowing the regions where water The data used in the inventory analysis are described in withdrawals related to the assessed HVAC systems take place, detail in the Supporting Information (SI), whereas a summary and second, the WTA values for those regions. Since most of the electricity, fuel, and water use in the operation phase of the geographical data available have been obtained at the is shown in Table 1 for both systems. country level, WTA values have been also used at this level, 3.3. Life Cycle Impact Assessment Methodology. Life with the exception of water use taking place in the CIESOL cycle impact assessment included the 10 standard impact building. In this case, the WTA of the river basin in which categories included in the CML2001 method (10). Contrary the building is located has been used. The WTA values used to the previous environmental indicators, impacts on fresh- in the study are displayed in Table 2. Further details on how water resources are far from being standardized in current this methodology has been applied can be found in the SI. LCIA practice. Up to date, most studies have neglected this issue, or reflected it as a simple indicator expressing the 4. Results and Discussion volume of water abstracted by the product system. In addition Figure 5 shows the results of the impact assessment, for the to the CML2001 impact categories, in the present study we two alternative systems. The solar-assisted HVAC has favor- have included the freshwater ecosystem impact (FEI) category able results in seven impact categories, namely GWP, AP, recently developed by Mila` i Canals and colleagues (11). This ODP, POCP, ADP, TETP, and MAETP, with impact scores approach focuses on consumptive (evaporative) water use, 58-90% lower, depending on the impact category. In all the and takes into account freshwater scarcity as characterization graphs it can be seen that the key to the lower impact in factor. FEI is measured as volume of “ecosystem-equivalent” these impact categories is the avoidance of grid electricity water, referring to the volume of water likely to be affecting consumption. In GWP for example, the solar-assisted HVAC freshwater ecosystems. The general formula for FEI calcula- -1 involves CO2-eq. savings of 80%, or 18 tons year , which tion is displayed in eq 1: represents the emissions of almost two Spanish person -1 -1 n equivalent years (9.6 tons CO2-eq person year )(21). ) In three impact categories, namely HTP, EP, and FAETP, FEI ∑ CWUix WTAi (1) i)1 the impact scores are not significantly different. In HTP and FAETP the contribution of infrastructure in the solar-assisted Where CWU is consumptive water use in m3, WTA is the HVAC must be highlighted. These results are in accordance withdrawal-to-availability ratio (WTA) and i to n are the set with those from Frischknecht et al. (22), who found that

FIGURE 5. Life cycle impact assessment results for both alternatives. (Note: 1,4-DCB is 1,4-dichlorobenzene.)

VOL. 44, NO. 9, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3591 Future efforts should be addressed to mitigate this impact TABLE 3. Results of the Sensitivity Analysis on Infrastructure by means of alternative heat dissipation methods, such as Useful Life borehole heat exchangers. impact solar-assisted conventional a/b category units HVAC (a) HVAC (b) (%) Acknowledgments This research has been carried out with the help of the project ADP kg Sb-eq 57 169 33% PSE-ARFRISOL (The Singular Strategic Project called Bio- AP kg SO2-eq 35 197 18% 3s climatic Architecture and Solar Cooling), PS-120000-2005-1 EP kg PO4 eq 11 10 107% GWP 100 tons CO2-eq 7.1 23.7 30% financed by the Spanish Ministry of Education and Science ODP g CFC-11-eq 0,3 1,2 25% (MEC). We thank all companies and institutions included in HTP tons 1,4-DCB eq 20 9 228% PSE-ARFRISOL project. FAETP kg 1,4-DCB eq 3057 1747 175% MAETP tons 1,4-DCB eq 3037 3832 79% TETP kg 1,4-DCB eq 84 434 19% Supporting Information Available POCP kg C2H4-eq 2 7 29% Detailed data on inventory analysis and impact assessment. FEI m3 ecosytem-eq 112 53 209 This material is available free of charge via the Internet at http://pubs.acs.org. toxicity impact categories, particularly these two, are very sensitive to the inclusion of capital goods in LCA studies. SI Literature Cited Figure S2 shows that the main infrastructure contributors (1) European Commission. Energy-Efficient Homes and Buildings, from the solar-assisted HVAC to all impact categories are the Project Report; Executive Agency for Competitiveness and photovoltaic installation, the solar collector array, and also Innovation: Brussels, 2008. (2) Buildings Energy Data Book; U.S. Department of Energy: tanks, pumps, and pipes. Concerning EP, most of the impact Washington, DC, November, 2008. of the solar-assisted HVAC is related to deionized water (3) Tukker, A.; Huppes, G.; Guineé, J.; Heijungs, R.,; de Koning, A.; production, which releases phosphates and nitrates initially van Oers, L.; Suh, S.; Geerken, T.; Van Holderbeke, M.; Jansen, present in raw water. B.; Nielsen, P.; Eder, P.; Delgado, L., Environmental Impact of Finally, Figure 5k shows the impact on freshwater Products (EIPRO). Analysis of the Life Cycle Environmental resources by the two alternatives. This environmental Impacts Related to the Final Consumption of the EU-25; IPTS/ ESTO project; Technical Report EUR 22284 EN: Seville, Spain, indicator includes only consumptive water uses (process 2006. water and evaporative uses), weighed according to the relative (4) Keolian, G.; Blanchard, S.; Reppe, P. Life cycle energy, costs, scarcity of freshwater in the country or region where it is and strategies for improving a single family house. J. Ind. Ecol. used. It can be seen that the heat pump HVAC has a 50% 2000, 4 (2), 135–156. lower impact when compared to the solar-assisted HVAC. (5) Ochoa, L.; Hendrickson, C.; Matthews, H. S.; Ries, R. Life cycle The latter is mainly due to the consumption of deionized assessment of residential buildings. In Proceedings of the ASCE Construction Research Congress; San Diego, CA, April 5-7, 2005. water for heat dissipation in the cooling tower, combined (6) Flores Larsen, S.; Filippıń, C.; Beascochea, A.; Lesino, G. An with the fact that freshwater in the Almerıá region is very experience on integrating monitoring and simulation tools in - scarce (average rainfall is 200 mm year 1, among the lowest the design of energy-saving buildings. Energy Build. 2008, 40, in Europe). Thus, although the overall volume of water 987–997. abstracted is lower in the solar-assisted HVAC (see SI Figure (7) Henning, H. M. Solar-Assisted Air Conditioning in Buildings. 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Koning, A.; Van Oers, L.; Wegener Sleeswijk, A.; Suh, S.; Udo de In this analysis, the data for the operational phase remained Haes, H. A.; Bruijn, J. A.; Van Duin, R.; Huijbregts, M. A. J. constant. Table 3 summarizes the LCIA results in this new Handbook on Life Cycle Assessment: Operational Guide to the scenario. The environmental performance of the solar- ISO Standards. Series: Eco-Efficiency in Industry and Science; Springer: Dordrecht, 2002. assisted HVAC would clearly get worse in such a scenario: (11) Mila` i Canals, L.; Chenoweth, J.; Chapagain, A.; Orr, S.; Antoń, the greenhouse gas emissions, for instance, increase by 50%, A.; Clift, R. Assessing freshwater use impacts in LCA Part I: but are still 70% lower than those from the conventional Inventory modelling and characterisation factors for the main system. However, the solar-assisted HVAC would have a impact pathways. Int. J. Life Cycle Assess. 2009, 14 (1), 28–42. significantly higher impact than its conventional counterpart (12) Pfister, S.; Koehler, A.; Hellweg, S. Assessing the environmental impacts of freshwater consumption in LCA. Environ. Sci. not only in FEI, but also in HTP and FAETP. Technol. 2009, 43 (11), 4098–4104. This study has shown that it is possible to achieve (13) Rosiek, S.; Batlles, F. J. Integration of the solar thermal energy comfortable indoor conditions (temperatures between 22 in the construction: Analysis of the solar-assisted air-condition- °C in winter and 25 °C in summer) with a technology allowing ing system installed in CIESOL building. Renewable Energy 2009, us to substantially reduce fossil energy demand and green- 34, 1423–1431. (14) Thuer, A.; Vukits, M. Solar heating and cooling for the solar city house gas emissions, and yet this is accomplished using Gleisdorf. Proceedings of the 3rd International Conference Solar equipment which are commercially available today. Nev- Air-Conditioning; Palermo, October, 2009. ertheless, solar-assisted air-conditioning is still in an early (15) Sparber, W.; Napolitano, A.; Besana, F.; Thur, A.; Nocke, B.; stage of development, and efforts must be made to improve Finocchiaro, P.; Bujedo Nieto, L. A.; Rodriguez, J.; Nun˜ez, T. its performance, not only in terms of economic competitive- Comparative results of monitored solar assisted heating and ness, but also in environmental terms. As we have seen, in cooling installations. Proceedings of the 3rd International Conference Solar Air-Conditioning, Palermo, October, 2009. regions like Almerıá with abundant solar resources but little (16) Ekvall, T.; Tillman, A. M. Open loop recycling: criteria for freshwater availability, a solar-assisted HVAC using a cooling allocation procedures. Int. J. Life Cycle Assess. 1997, 2 (3), 155– tower involves an important impact on freshwater resources. 162.

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