Comparison of measured and predicted data of solar radiation over Tanta

Abstract

Measurements of global solar radiation on a horizontal surface in Tanta for a whole year are compared with predictions made by several independent methods. The best found method is based on Anstrom formula which correlates relative global solar radiation H / H o to corresponding relative duration of bright sunshine n / N . The regression coefficients are determined and used for prediction of global solar radiation. The agreement with measurements is better than 9%. Other methods are employed, such as that of Reddy and Barbaro which use sunshine duration and minimum air mass as inputs. Unavoided deviations of at least 15% are recorded. Estimation of diffuse solar radiation by Page's as well as Liu, Jordan and Klein's correlations is also performed and the results are examined. The beam component of the solar radiation is computed. Useful data are obtained.