The integration of green roofs with photovoltaic (PV) panels has the potential for synergistic effects; cooling the panels by the green roof may increase electrical production, while PV panels may positively affect diversity of plants and arthropods on the green roof. Shading by solar panels in arid climates may reduce drought stress for plants, allowing more plant species to survive. In turn, the high plant diversity may have a positive effect on arthropod diversity. Also, partial shading by the PV creates heterogeneity in temperature and humidity on the roof, producing different microhabitats for different species, potentially increasing biodiversity on the roof. There are very few studies with sufficient replication on the integration of green roofs and PV panels and the effect of PV integration on biodiversity. Our study tested the benefits of integrating green roofs and PV systems for PV efficiency and plant and arthropod diversity on the roof. We examined the effects of PV and green roof integration with the following treatments: PV alone on a bituminous sheet, a stand-alone sedum-annual green roof, and green roof plus PV system. Electricity production, abiotic conditions, plant cover and phenology, and arthropod communities were compared among treatments.
Results from the first year indicated that electricity production was not affected by the presence of the green roof. However, the presence of the panels on the green roofs contributed to heterogeneity in soil moisture, and provided some benefits to the plant community. The presence of PV panels resulted in longer flowering time, and in higher biomass in the area near the front of the panels. Additional results from the second year of the study, including effects on the arthropod community, will be presented. Future studies should examine the effects of irrigation and of other plant communities on the cooling effect of green roofs, and the resultant effect on PV panel efficiency. With an appropriate plant community, we may find that in addition to the benefits for the plant community, the integration of PV and a green roof also improves electricity production.