Journal Article

The Observed Effects of Utility-Scale Photovoltaics on Near-Surface Air Temperature and Energy Balance

Georgescu, Matei, Broadbent, Ashley M., Krayenhoff, E. Scott, Sailor, David J.

2019

Overview

Utility-scale solar power plants are a rapidly growing component of the renewable energy sector. While most agree that solar power can decrease greenhouse gas emissions, the effects of photovoltaic (PV) systems on surface energy exchanges and near-surface meteorology are not well understood. This study presents data from two eddy covariance observational towers, placed within and adjacent to a utility-scale PV array in southern Arizona. The observational period (October 2017–July 2018) includes the full range of annual temperature variation. Average daily maximum 1.5-m air temperature at the PV array was 1.3°C warmer than the reference (i.e., non-PV) site, whereas no significant difference in 1.5-m nocturnal air temperature was observed. PV modules captured the majority of solar radiation and were the primary energetically active surface during the day. Despite the removal of energy by electricity production, the modules increased daytime net radiation Q* available for partitioning by reducing surface albedo. The PV modules shift surface energy balance partitioning away from upward longwave radiation and heat storage and toward sensible heat flux QH because of their low emissivity, low heat capacity, and increased surface area and roughness, which facilitates more efficient QH from the surface. The PV modules significantly reduce ground heat flux QG storage and nocturnal release, as the soil beneath the modules is well shaded. Our work demonstrates the importance of targeted observational campaigns to inform process-based understanding associated with PV systems. It further establishes a basis for observationally based PV energy balance models that may be used to examine climatic effects due to large-scale deployment.

• Publisher: American Meteorological Society
• Subject: Air temperature / Albedo / Albedo (solar) / Alternative energy sources / Annual temperature range / Annual temperatures / Arrays / Biogeochemistry / Climate effects / Cooling / Covariance / Deployment / Eddy covariance / Electric power generation / Electricity / Emissions / Emissivity / Energy balance / Energy balance models / Energy industry / Energy resources / Energy storage / Energy transfer / Enthalpy / Environmental management / Fossil fuels / Greenhouse effect / Greenhouse gases / Heat / Heat exchange / Heat flux / Heat storage / Heat transfer / Hydrology / Industrial plant emissions / Long wave radiation / Meteorology / Modules / Net radiation / Partitioning / Photovoltaic cells / Photovoltaics / Power plants / Radiation balance / Renewable energy / Renewable resources / Resource management / Roughness / Sensible heat / Sensible heat flux / Sensible heat transfer / Soil / Solar energy / Solar power plants / Solar radiation / Specific heat / Surface energy / Surface energy balance / Surface properties / Surface temperature / Surface-air temperature relationships / Temperature variations / Vegetation