Estimation of monthly global solar radiation over twelve major cities of Libya

•7 empirical models are compared for estimation of solar radiation over Libya.•The models are established using measured data of global solar radiation.•Statistical indicators are calculated to evaluate the performance of the models.•The best model performance for each site is determined.•The results show that there is no unique model valid for all considered sites. This study aims to estimate monthly averaged daily horizontal global solar radiation. Measured climatological data collected at twelve major cities located across Libya's map were used to establish 7 different empirical models. The empirical coefficients of the models were calculated using the least square method. The accuracy of the models was evaluated using different statistical criteria such as Taylor diagram, mean absolute percentage error, MAPE, and root mean square error, RMSE. The results indicated that the sunshine duration-based models are more accurate than air temperature-based models, and the best performance was obtained by the quadratic regression model for all twelve Libyan cities. Moreover, this regression model can be used for the prediction of monthly mean horizontal global solar radiation at a specific site across Libya's regions with minimum error. Furthermore, the results of the global solar irradiance produced by this method can be used for designing solar systems applications. [Display omitted]