The potential for air-temperature impact from large-scale deployment of solar photovoltaic arrays in urban areas

Among the many benefits of solar photovoltaic (PV) systems, the direct effects are those of providing local power and the indirect ones include avoided generation from fossil-fuel power plants. The latter translate into reduced emissions of greenhouse gas (thus reduced radiative forcing) and other pollutants, such as ozone precursors (thus improved air quality). Because large-scale PV deployments can alter the radiative balance at the surface-atmosphere interface, they can exert certain impacts on the temperature and flow fields.In this analysis, meteorological modeling was performed for the Los Angeles region as a case study to evaluate the potential atmospheric effects of solar PV deployment. The simulations show no adverse impacts on air temperature and urban heat islands from large-scale PV deployment. For the range of solar conversion efficiencies currently available or expected to become attainable in the near future, the deployment of solar PV can cool the urban environment. The cooling can reach up to 0.2 C in the Los Angeles region. Under hypothetical future-year scenarios of cool cities (urban areas with extensive implementations of highly-reflective roofs and pavements) and high-density deployments of urban solar PV arrays, some adverse impacts (0.1 C or less in warming) might occur. However, such extreme high-density deployments of cool surfaces are not expected and thus the warming effects are unlikely to result.

► Large-scale deployment of solar PV arrays has no adverse impact on the atmosphere.
► At solar conversion efficiency of 20% or higher, PV arrays can cool the air.
► Very high-density deployment of PV can cause some warming but also larger cooling.
► Increasing roof albedo by 0.05 and PV efficiency from 10% to 20% are equivalent.