Comparative Assessment of Angstrom Sunshine-Base Models for Estimation of Global Solar Radiation in Owerri, Nigeria

Abstract

Comparative assessment of the average monthly global solar radiation on horizontal surface for Owerri has been carried out with the use of five Angstrom sunshine base models. Thirty years (1992 - 2022) of average monthly global solar radiation and sunshine hours are sourced from NASA and NIMET, respectively. The sunshine-base models are evaluated with the use of geographical and metrological data of Owerri and comparison is made based on estimated statistical error indices of Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Coefficient of Determination (R2) and percentage error to assess the applicability accuracy of the models. Results obtained shows that regression equations of Fagbenle and Page models satisfied viability criterion of MBE, RMSE, and MPE being close to zero, the R2 values are reasonably close to unity and the percentage error agreed to within ± 10% of the measured average monthly global solar radiation on a horizontal surface in Owerri. Rietveld model closely followed with less prediction accuracy to those of Fagbenle and Page models, while, Glower and McCulloh and Turton models yield poor estimation of the average monthly global solar radiation on horizontal surface.