Persistent site-scale warming associated with solar photovoltaic installations

Large-scale solar photovoltaic (PV) farms are widely promoted in semi-arid regions as a key strategy to meet the growing energy demand while reducing carbon emissions. However, it is hypothesized that this extensive land-cover transformation disrupt local energy balance, thereby modifying near-surface thermal conditions. To verify this hypothesis, we conducted a comprehensive field experiment in a semi-arid desert region in Inner Mongolia, China. Our observations reveal a persistent warming signal: (1) The PV farm exhibited a two-year mean air temperature increase of 0.8 °C relative to the reference site, with warming evident across all seasons. Notably, the increase in the daily minimum air temperature was greater than the increase in daily maximum temperature, resulting in a 1.9 °C reduction in the daily temperature range compared to non-PV areas. (2) UAV-based thermal mapping further corroborated these findings, detecting consistent land surface temperature increase of by 0.3-4.1 °C relative to adjacent non-PV areas, indicating enhanced surface warming and altered spatial thermal patterns. (3) The daily net radiation was increased by 8.3 W m^-2 in the PV farm area, particularly during the daytime (18.5 W m^-2). This increase in net radiation was primarily due to a decrease in albedo, which resulted in 24.6 W m^-2 more net shortwave radiation. (4) The PV farm increased the outgoing longwave radiation by 6.1 W m^-2 during the daytime and 4.6 W m^-2 at night, which was considerably lower than the increased net shortwave radiation. In sum, this study demonstrates persistent site-scale warming associated with photovoltaic installations under the observed environmental conditions observed in a semi-arid desert, which may have implications for microclimatic regulation in similar dryland PV systems. These findings underscore the need to consider potential environmental trade-offs in future PV deployment strategies.