Influence of aerosol input data on WRF-Solar global horizontal irradiance forecasts for solar energy in West Africa

West Africa has significant solar energy resources, and the growing number of photovoltaic power plants is increasing solar production. The establishment of a day-ahead market should make it possible to increase the share of this intermittent energy in the energy mix. However, this type of market requires estimating the production a day in advance, and thus addressing the challenges of weather and solar forecasting.

Dust advection and clouds are the two meteorological phenomena that most influence photovoltaic production in West Africa. They are still poorly represented by numerical weather models in this region, as no operational high-resolution regional forecasting systems exist. Moreover, the available global operational forecasting systems generally use a low-resolution aerosol climatology that does not account for high-frequency spatiotemporal variability of atmospheric dust content.

This study aims to evaluate the potential improvements achieved through a regional model that incorporates aerosol information and offers high resolution (3 km, 15 min) over Burkina Faso. The Weather Research & Forecasting Model (WRF), an atmospheric simulation system from NCAR, is supplemented by an extension for solar application: WRF-Solar. It can be used with different types of aerosol data, calculating the influence of Aerosol Optical Depth (AOD) on Global Horizontal Irradiance (GHI). In this study, WRF-Solar is used with three different configurations: without AOD data, with the monthly aerosol climatology built into WRF, and with the hourly 2D AOD forecast from CAMS (an atmospheric chemistry model produced by ECMWF). The WRF-Solar simulations are forced by ECMWF IFS forecasts. The simulations have a duration of 36 hours to meet the requirements of the day-ahead market. Two study periods were chosen: during the monsoon season, from July 2023 to September 2023 and during the dry season, from January 2024 to march 2024. The forecasts are evaluated against in-situ GHI measurements from a pyranometer located at Zagtouli photovoltaic power plant.

The results show that simulations using the CAMS 2D AOD forecast and those using the built-in monthly aerosol climatology give similar overall results, with their own specific characteristics. Both configurations simulate an overestimated GHI. They both have a clear advantage over the WRF-Solar configuration without AOD data. Slight differences between the configurations are observed in the calculated GHI on cloudy days during the monsoon, which are related to differences in cloud representation.