Evaluation of some global solar radiation models in selected locations in Northwest, Nigeria

This study assesses the performance of four global solar radiation models in three selected locations (Gusua, Yelwa and Katsina) in North-western, Nigeria. A new model for estimating global solar radiation which is developed by Olomiyesan and Oyedum is also presented. This model alongside three existing models has been tested and validated for the selected locations using twenty-two years ' (1984-2005) meteorological data collected from the Nigerian Meteorological Agency (NIMET). Global solar radiation estimated from the newly developed model was compared with the values obtained from Garcia, Hargreaves-Samani and Angstrom-Prescott models. The accuracy of the models was determined by using mean bias error (MBE), mean percentage error (MPE), root mean square error (RMSE) and coefficient of determination (R 2 ). Based on the statistical error indices obtained, Olomiyesan and Oyedum model was found to perform best in terms of accuracy, with the least RMSE values in the three locations, and highest coefficient of determination, R 2 values in two of the three locations. Thus, the newly developed model is suitable for estimating global solar radiation in the North-Western region of Nigeria and other locations with similar meteorological and climatic conditions.