Effects of rooftop photovoltaics on building cooling demand and ambient air

Photovoltaic panels are commonly used for their versatility in on-site generation of clean electricity in urban environments, specifically on rooftops. However, their implementation on rooftops poses potential (positive and negative) impacts on the energy use of buildings, and urban climates. The negative impacts are compounded if PV is installed on top of a high-albedo rooftop. This study quantitively investigates these impacts from PV installation on top of a building with a white roof in Phoenix, AZ. We supplemented our measurements with EnergyPlus simulations to model the energy implications for archetypical residential and retail buildings and calculated the energy penalty to generation ratio as well as sensible heat flux for each combination of panel height and building type. Results indicate that the daily cooling energy penalty to due blockage of outgoing longwave radiation can be 4.9—11.2% of the PV generation. In addition, while we observed a small decrease in nighttime sensible heat flux to the ambient, PV cases increased the daytime heat flux by more than a factor of 10. This study highlights the potential unintended consequences of rooftop PV under certain conditions and provides a broader perspective for building designers and urban planners.