Energy and Carbon-Emission Analysis of Integrated Green-Roof Photovoltaic Systems: Probabilistic Approach

Roofs are important components of buildings and can be designed and/or retrofitted with photovoltaic (PV) and green-roof (GR) systems to produce energy and to improve stormwater management. Traditionally, GRs and PVs have been viewed as direct competitors vying for the same roof space. However, with correct design, synergy effects arise when combining both technologies (GR-PV). In this paper, a probabilistic analysis is performed to examine the potential energy and carbon emissions of GR, PV, and GR-PV systems. The analysis demonstrates that a GR-PV system is a low-risk investment generating lower energy and carbon-emission payback time in comparison with separate GR and PV systems. Furthermore, the average of net energy of this technology is 7.3 and 1.3 times higher than separate GR and PV systems, respectively. In addition, the installation of GR-PV systems throughout the City of Toronto could supply 16% of the electricity by PVs and reduce 12% of energy demand (i.e., heating and cooling) by GRs. However, extensive modification of the electrical grid would be needed for efficient collection and transmission of PV-generated power. (c) 2017 American Society of Civil Engineers.