Impact of photovoltaic solar panels deployment on urban heat island and radiative forcing from airborne hyperspectral observations

Urban areas dominated by low-reflective materials increase solar radiation absorption, altering Earth's energy balance and rising local temperatures, known as Urban Heat Island (UHI). European policies are promoting large-scale deployment of photovoltaic solar panels (PVSPs) for mitigating GHG emissions, however their impacts on UHI and Earth's radiative forcing remain insufficiently quantified. This study evaluates these impacts across different land covers using high-resolution hyperspectral and thermal airborne imagery collected in the urban and rural area of Lucca, Italy. The effect of UHI produced by the land cover change was calculated as the difference in Land Surface Temperature (LST) between PVSPs and each land cover. The global warming potential (GWP) driven by the albedo changes when installing the PVSPs required by Italy to accomplish the European climate target was expressed as CO₂-equivalent (CO₂eq) emissions. Results demonstrated that PVSP installation impacts differently on UHI depending on the land cover replaced, with changes in LST of ± 17°C. Placing PVSPs on water (average of +16.9 °C), green vegetation (+12.7 °C) or white-painted roofs (+3.8 °C) produces the highest increase in LST, while dark (-10.2 °C) or red (-7.6 °C) metal roofs would mitigate UHI. The CO₂eq analysis showed that water (4.9 × 10⁸ kg CO₂ year⁻¹) and dark metal roofs (-0.9 kg CO₂ year⁻¹) would reduce GWP. Consequently, placing PVSPs on dark metal roofs may benefit GWP and UHI. These findings highlight the importance of prioritizing land cover-specific PVSP placement and demonstrate the value of high-resolution airborne data for climate-sensitive urban and rural planning.