Photovoltaic-green roofs: A review of benefits, limitations, and trends

Photovoltaic (PV)-green roofs, a new development integrating the PV system with a green roof, provide additional benefits for renewable electricity production as compared to the green roof. This study provides a systematic review of the published literature in Scopus and Web of Science regarding PV-green roof technologies, to identify the benefits and challenges associated with PV-green roofs in practice, and its future directions. A total of 145 published documents were reviewed, revealing that the PV-green roof is an effective strategy for producing clean energy on the building scale. However, there are still various challenges that hinder the large-scale implementation of PV-green roofs, including high initial costs, limited experimental data, and lack of awareness about the long-term benefits. These challenges can be overcome through the new cost-effective design of PV-green roofs and the adoption of the most appropriate materials, which can perform more effectively over a longer period. In addition, more real large-scale experimental studies are needed to evaluate the long-term performance of PV-green roofs in urban areas. Suggestions for further improvements include: providing the optimal design of PV-green roofs for each climatic region; improving laws and regulations; evaluating life-cycle assessment including social, environmental, and economic benefits over a longer period; and establishing interagency collaboration and cooperation tools for the wider adoption of PV-green roof projects. This review draws an overall picture of the benefits and limitations of the PV-green roof around the world. Findings provide a useful reference for the enhancement of the PV-green roof design for their broader application in the building industry.