D. Khare, N. Nijegorodov, and T.A. Thomas (Botswana)
Daily, Mean Monthly SolarRadiation Comp onents.
African continent is especially rich in solar energy. For example, Botswana has excellent solar condition where, there are over 320 clear, sunny days per year, with an average of 21 MJ/m2 global insolation per day. But up to now, there are very little experimental data about solar radiation components recorded in southern Africa. In this paper, simulated and experimental data of instantaneous, hourly and daily direct normal, Ibn, global, Ig, solar radiation on horizontal and tilted (β = -30°, North) surfaces, recorded at the University of Botswana, Botswana Technology Centre and at some synoptic stations in Botswana, are analyzed. It is found that the instantaneous direct normal radiation at Solar Noon can be as high as 1150 W/m2 ; 30 minutes before sunset it can be above 60W/m2 and up to 100 W/m2 at sunset or at sunrise moments (half of the solar disc is under horizon). Daily direct normal solar radiation can exceed 45 MJ/m2 . Mean daily global radiation varies from 31 MJ/m2 in December to 16 MJ/m2 in June. Such big values of daily direct normal and global radiation are explained by low humidity and low turbidity
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