Monte-Carlo-based simulations of radiative transfer in photovoltaic solar farms: Towards fast and accurate parameterizations in weather and climate models

Abstract

Photovoltaic (PV) solar farms, composed of arrays of photovoltaic panels, play a vital role in our effort to reduce the reliance on fossil fuels and mitigate global warming. Meanwhile, these panels alter surface radiative properties and can affect the local surface energy budget. To assess the influence of PV solar farms on the climate, previous modeling studies simply assumed flat solar panels lying on the ground and modified surface albedo to mimic the radiative effect of large-scale solar farm deployments. Here, we developed a Monte-Carlo-based radiative transfer model that can more accurately capture the role of the complex geometry of a real-world PV solar farm in 3-D radiative transfer. Specifically, solar panels are separated from the ground, tilted and elevated, with their own surface reflectance and emissivity. In this way, the scheme inherently accounts for the radiative transfer between panel and ground and between panel arrays. The model can be tailored to specific PV solar farm configurations through six adjustable input parameters, including panel tilt angle and spacing. A sensitivity analysis of both shortwave and longwave radiative processes within the farm reveals that front panel albedo (emissivity), ground albedo (emissivity), and panel area fraction determine the overall reflectivity (emissivity) of the entire solar farm site. Based on such Monte-Carlo calculations, a set of lookup tables was then constructed for fast parameterizations in the numerical weather models or climate models with desired computational efficiency.