Indoor, Outdoor, and Power Implications of Rooftop Photovoltaic Panels Deployment

A swift transition to renewable energy is essential for meeting global demand and mitigating climate change, yet land scarcity presents a challenge. Installing photovoltaic panels on urban surfaces, such as roofs and walls, offers a promising solution but may alter energy flows and urban microclimates. Before deploying building-integrated photovoltaics, it is crucial to consider:

• How do different layouts affect energy transfer from roofs?
• What are the implications for the magnitude and timing of building energy demand and sensible heat emissions to the urban boundary layer?
• How sensitive are roof responses and heat transfer to variations in meteorological drivers such as shortwave radiation, air temperature, and wind speed?

To address these questions, we developed a multi-element energy budget model to simulate solar roof configurations. Our results show that, in cold climates, solar roofs reduce conduction into the building almost as much as cool roofs, while also generating energy to offset heating demand. In hot climates, inclined panels are preferable in reducing indoor heat gains, outperforming cool roofs while producing clean energy for cooling.

These benefits are not free. Solar roofs increase sensible heating of the UBL relative to a cool roof, exacerbating the urban heat island effect during peak insolation. However, the peaks in sensible heat occur before the peaks in air temperature (moderating the impact on daytime thermal comfort), and notably, solar roofs mitigate nighttime UHI which is critical for reducing heat-related health risks.

An elasticity analysis of heat fluxes reveals that, under intense solar radiation, solar roofs shift more of the excess heat to sensible heat. In warmer climates with higher air temperatures that reduce sensible heat losses, the conduction of heat into the indoor building increases. Although wind generally has a moderate impact on fluxes, its variability modulates heat partitioning, favoring greater sensible heat flux and reduced conduction into the building.