Rooftop photovoltaic solar panels warm up and cool down cities

The proliferation of rooftop photovoltaic solar panels (RPVSPs) may heighten the risk of urban heating due to thermal convection between the panels and the roof surface. Therefore, it is crucial to comprehend the implications of widespread RPVSPs adoption in urban settings. This study examines the impact of RPVSPs on the urban environment in Kolkata, utilizing regional climate modeling. It integrates a new RPVSP parameterization into an urban canopy model (UCM) within the weather research and forecasting (WRF) model, assuming parallel RPVSP arrays detachable at 0.3 m height with a 6.55 mm thin layer. Results show that while RPVSP adoption can increase daytime urban temperatures by up to 1.5 °C during heatwaves, it can cool the urban environment by up to 0.6 °C at night. Furthermore, it increases sensible and latent heat flux by 241.6 Wm-² and 35.3 Wm-², respectively, impacting wind speeds and sea breeze onset. Elevated urban temperatures due to RPVSPs installation enhance lower atmospheric mixing and raise the planetary boundary layer (PBL) height by up to 615.6 m, reducing ground-level pollution. The study's assessment of four worldwide case studies - Sydney, Austin, Athens, and Brussels along with Kolkata to compare their RPVSP surface temperatures and urban state variables corroborates these insights, providing essential guidance for policymakers managing large-scale RPVSPs deployment.