Investigation of the impacts of microclimate on PV energy efficiency and outdoor thermal comfort

Cities are increasingly incentivizing rooftop photovoltaics (PV) for the reduction of greenhouse gas emissions together with more urban forestry and high albedo surfaces for the mitigation of the urban heat island (UHI) effect. Previous interventions are proven to be effective in isolation, but their combined performance is seldom considered. Through microclimate simulations of a neighbourhood in Brampton, Ontario, this study investigates the trade-offs between large-scale deployments of rooftop PV, street trees, and cool roofs. The performance of each intervention is compared by examining the impact on the PV efficiency (and the produced electricity) and the Universal Thermal Climate Index (UTCI) values. The study shows that street trees can reduce the energy output of rooftop PV significantly depending on their height and location, and it confirms the need for solar access laws, currently missing in Ontario. Further, this study shows that a large adoption of rooftop PV instead of cool roofs can result in an outdoor environment up to 0.5 °C higher in terms of UTCI during heatwave periods.