On the prediction of the daily global solar radiation intensity on south-facing plane surfaces inclined at varying angles

Over the years, some authors have used different models to estimate the solar radiation intensity over inclined surfaces, but none of them has tested and evaluated the accuracy of these models for various inclinations. In this study, by using the acquired data from Meteonorm, five best models studied previously by the authors have been used in order to predict the daily global solar radiation intensity DGSRI received on an inclined surface to the south and to evaluate the day by day performance of these models using a statistical analysis performed by several statistical indicators. The analysis of results revealed that the selected models haven't the same accuracy, and it is concluded that there are models that can be preferred for the prediction of the DGSRI received on a tilted surface with different angle of inclination at the considered site, Tetuan city in northern Morocco. Empirical correlations between solar radiation intensity fallen on south-facing plane surfaces with various inclination and that receive on horizontal surfaces have been developed. As mean of results of the statistical indicator errors and excluding 20°, 60° and 70° inclinations and the coefficient of determination R2 values, El Mghouchi model is performing comparatively better than the others for all inclinations ranging from 0° (horizontal plane) to 90° (vertical plane) in steps of 10°.