Assessment of the green roof integrated solar PV system

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Vanisha A/P Arenandan
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Green roof and solar photovoltaic (PV) systems are two technologies that could contribute to sustainable building development and reduction of greenhouse gas emissions. Many studies have been conducted in different countries to evaluate the energy and thermal performances of green roof and PV systems separately. However, there are very limited studies on the performance of integrated green roof- solar PV system for tropical climate country. It is hypothesized that cooling effect from evapotranspiration process of green roof plants will enable higher power generation efficiency of PV panels. Thus, this study is aimed to (i) determine the cooling effects of green roof on the ambient air temperatures and PV surface temperatures; (ii) determine the suitable height of green roof as well as life cycle cost and cost effectiveness of green roof. In this study, two (2) units solar PV panels of 1 kW each were setup at the rooftop level of administration building in UNITEN campus. Modular green roof test beds with same components and plant species (sedum) were setup at three different heights which are 0.3 m, 0.6 m and 0.9 m, respectively. The effects of each green roof height on the solar PV panels’ surface temperature, ambient temperature and daily total yield (kWh) were monitored for 6 months’ period. Life cycle assessment (LCA) was carried out to assess the environmental impacts of solar PV panel and green roof. OpenLCA software was used to conduct the LCA study on both solar PV systems. The cost-benefit analysis of green roofs was conducted by using Net Present Value (NPV) calculation. The results showed that integration of green roof with solar PV system will have lower ambient and PV surface temperatures of 3.36% and 17% differences if compared to bare roof-PV system. Besides, green roof enhances the PV power generation efficiency averagely by 1.6% compared to bare roof in this study. It is found that green roof installed at 0.3 m height has increased the PV power generation performance by 11% compared to that of 0.6 m and 0.9 m heights. The LCA results have proved that green roof is able to mitigate the environmental impacts compared to typical roof. The cost-benefit analysis conducted in this study indicated that integrated green roof- solar PV system is not that cost effective due to high installation and maintenance cost. In conclusion, integrated green roof-solar PV system provides better performance especially with green roof installed at 0.3 m height if compared with bare roof-solar PV system.