POTENTIALS OF WIND AND SOLAR ENERGY GENERATION OVER WEST AFRICA IN A CHANGING CLIMATE

Abstract

Many West African countries are suffering from a poor electricity supply. However, an abundance of solar irradiance and sufficient wind speed over the region makes solar and wind energy attractive solutions to the problem, but there is a dearth of information on how ongoing global warming may alter the photovoltaic power generation potential (PVP) and wind power density (WPD) over the region in the future. Moreover, there is a lack of information on the capability of numerical weather prediction models simulates the shortwave radiation flux over the region. This study thus investigates the impact of climate change on PVP and on WPD over West Africa under various global warming levels (1.5°C; 2.0°C; 2.5°C and 3.0°C) under the RCP8.5 climate change scenario and also assesses the solar irradiation (Rs) over West Africa. For the PVP study, fourteen regional climate model simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX) were analysed. Eleven multi-model multi-ensemble simulation datasets, also from the CORDEX project, were analysed for the WPD study. In addition, this study also investigated how the Weather Research and Forecasting (WRF) model shortwave radiation schemes simulate the Rs over West Africa. The modification of the Dudhia shortwave radiation physics has been made by making the water vapour absorption varies with temperature and pressure according to levels. The results show that the CORDEX simulation ensemble correctly captures the spatial distribution of climate variables and PVP over West Africa, albeit with a few biases. The simulations and observations agree that PVP over West Africa varies from 8% along the Guinean zone to 25% over the Sahel zone and that the annual cycle of PVP is influenced by the seasonal variation of the monsoon system. The simulation ensemble projects a decrease (up to 3.8%) in PVP over West Africa in the future and indicates that the viii magnitude of the decrease grows with warming levels. Additionally, the results show that the model ensemble’s mean gives a good simulation pattern of wind speed and WPD with high correlation values (r = 0.9 and r = 0.95 respectively) over West Africa, although with notable biases. The simulations project an increase in monsoon wind speed and wind power potential over West African cities, and the magnitude of this increase grows with increasing global warming levels. The study also found that most of the different WRF shortwave radiation schemes simulate well the observed Rs over West Africa and its three different zones. Nonetheless, the modified Dudhia (DudhiaM) improves the simulation of the Rs over the region. The DudhiaM captures well the diurnal, annual and the inter-annual variation of the observed Rs. The results of the study suggest that climate change will increase the WPD while it will decrease the PVP over West Africa. Also, the DudhiaM scheme outperforms the different WRF schemes in simulating Rs over the region. This may guide policymakers on how to harness wind and solar energy in order to meet the electricity demands in the future.