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Atmospheric aerosols affect the power production of solar energy systems. Their impact depends on both the atmospheric conditions and the solar technology employed. By being a region with a lack in power production and prone to high solar insolation, West Africa shows high potential for the application of solar power systems. However, dust outbreaks, containing high aerosol loads, occur especially in the Sahel, located between the Saharan desert in the north and the Sudanian Savanna in the south. They might affect the whole region for several days with significant effects on power generation. This study investigates the impact of atmospheric aerosols on solar energy production for the example year 2006 making use of six well instrumented sites in West Africa. Two different solar power technologies, a photovoltaic (PV) and a parabolic through (PT) power plant, are considered. The daily reduction of solar power due to aerosols is determined over mostly clear-sky days in 2006 with a model chain combining radiative transfer and technology specific power generation. For mostly clear days the local daily reduction of PV power (at alternating current) (PVAC) and PT power (PTP) due to the presence of aerosols lies between 13 % and 22 % and between 22 % and 37 %, respectively. In March 2006 a major dust outbreak occurred, which serves as an example to investigate the impact of an aerosol extreme event on solar power. During the dust outbreak, daily reduction of PVAC and PTP of up to 79 % and 100 % occur with a mean reduction of 20 % to 40 % for PVAC and of 32 % to 71 % for PTP during the 12 days of the event.
For a sustainable development the electricity sector needs to be decarbonized. In 2017 only 54% of the West African households had access to the electrical grid. Thus, renewable sources should play a major role for the development of the power sector in West Africa. Above all, solar power shows highest potential of renewable energy sources. However, it is highly variable, depending on the atmospheric conditions. This study addresses the challenges for a solar based power system in West Africa by analyzing the atmospheric variability of solar power. For this purpose, two aspects are investigated. In the first part, the daily power reduction due to atmospheric aerosols is quantified for different solar power technologies. Meteorological data at six ground-based stations is used to model photovoltaic and parabolic trough power during all mostly clear-sky days in 2006. A radiative transfer model is combined with solar power model. The results show, that the reduction due to aerosols can be up to 79% for photovoltaic and up to 100% for parabolic trough power plants during a major dust outbreak. Frequent dust outbreaks occurring in West Africa would cause frequent blackouts if sufficient storage capacities are not available. On average, aerosols reduce the daily power yields by 13% to 22% for photovoltaic and by 22% to 37% for parabolic troughs. For the second part, long-term atmospheric variability and trends of solar irradiance are analyzed and their impact on photovoltaic yields is examined for West Africa. Based on a 35-year satellite data record (1983 - 2017) the temporal and spatial variability and general trend are depicted for global and direct horizontal irradiances. Furthermore, photovoltaic yields are calculated on a daily basis. They show a strong meridional gradient with highest values of 5 kWh/kWp in the Sahara and Sahel zone and lowest values in southern West Africa (around 4 kWh/kWp). Thereby, the temporal variability is highest in southern West Africa (up to around 18%) and lowest in the Sahara (around 4.5%). This implies the need of a North-South grid development, to feed the increasing demand on the highly populated coast by solar power from the northern parts of West Africa. Additionally, global irradiances show a long-term positive trend (up to +5 W/m²/decade) in the Sahara and a negative trend (up to -5 W/m²/decade) in southern West Africa. If this trend is continuing, the spatial differences in solar power potential will increase in the future. This thesis provides a better understanding of the impact of atmospheric variability on solar power in a challenging environment like West Africa, characterized by the strong influence of the African monsoon. Thereby, the importance of aerosols is pointed out. Furthermore, long-term changes of irradiance are characterized concerning their implications for photovoltaic power.