Validating clear-sky irradiance models in five South African locations

Abstract

Global horizontal solar irradiance is the maximum solar radiation coming in all directions from a cloudless sky incident at a location and time. This paper eval uates and validates clear-sky models in different locations of South Africa from measured global horizontal irradiance compared to estimated values by these models. The measured data consists of a one-year period in one-minute resolution of GHI at five different stations, namely, Stellenbosch, University of Fort Hare, Vuwani, University of Free State and Pretoria. Four simple (Haurwitz, Berger-Duffe, ABCG, Kasten Czeplak) and three complex (Ineichen { Perez, Bird { Hulstrom, Simplified Solis) clear-sky irradiance models are considered for this paper. The statistical metrics Mean Absolute Error and Root Mean Square Error are used to assess the precision and accuracy of these models. We observed that there is a correlation between the number of input parameters and the performance of the models.