Estimation of Global Solar Radiation on Horizontal Surfaces Over Egypt

The measured data of the monthly average global solar radiation on a horizontal surface H and the number of bright sunshine hours n for five locations in Egypt are analyzed. The selected locations represent the various weather conditions of Egypt. Matruh, Rafah and Al-Arish are in the north, Tanta in the middle and Aswan in the south. The regression constants for the first, second and third order Angström type correlations for each location have been calculated using the method of regression analysis. Comparisons between measured and calculated values of H are performed for the present locations. The values obtained for the RMSE, MBE and the MPE indicated that the second and third order Angström type correlations do not improve the accuracy of estimation of global radiation. Therefore, the measured data available for the selected locations are combined and a first order correlation has been proposed for all Egypt. Moreover, all Egypt correlation is extended to other Egyptian locations which are not included in the regression analysis. Comparisons between measured and calculated global radiation indicated that all Egypt correlation is applicable for any location of Egypt and may be extended outside Egypt for places which have the same values of the maximum clearness index (a + b).