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Photovoltaic-green roofs: a life cycle assessment approach with emphasis on warm months of Mediterranean climate

Lamnatou, Chr., Chemisana, D.
Journal of cleaner production 2014 v.72 pp. 57-75
Mediterranean climate, carbon dioxide, climatic factors, cost effectiveness, energy, environmental impact, gravel, green roofs, greenhouse gas emissions, life cycle assessment, manufacturing, solar energy, transportation
The combination of Photovoltaics (PVs) with green roofs is a new tendency in the building sector and provides benefits such as PV output increase because of plant/PV interaction. The present study regards the evaluation of a PV-green roof along with other roof configurations: PV-gravel, green (extensive and intensive), gravel. The evaluation of the systems is based on Life Cycle Analysis by means of Eco-Indicator 99, IMPACT 2002+ and Cumulative Energy Demand methodologies. Stages of the phases of material manufacturing, material transportation, use/maintenance and disposal are considered and the results show that material manufacturing is the most energy-demand phase for all the studied roofs. The roofing systems are separated into PV roofs, non-PV roofs and the comparisons are conducted within each group. Emphasis is given on the PV-green configuration and its comparison with the PV-gravel one, based on different scenarios regarding PV output increase. The results reveal that although the PV-green system has an additional environmental impact in comparison with the PV-gravel one (because of its additional “green” components), this additional impact on a log-term basis can be compensated. Furthermore, the two PV roofs are compared with gasoil and those results also verify the benefits of the PV-green configuration regarding gasoil/cost savings and reduction of CO2 emissions. In general, the study gives emphasis on warm months of Mediterranean climate since PV-green roofs have been proven beneficial under these climatic conditions. Finally, a discussion about critical factors in the field of PV-green systems provides a wider view of the studied issues.