Abstract
Solar radiation data computerly measured at Amman, Jordan was used to verify the performance accuracy of two models for estimation of global radiation on tilted surfaces. The measurements used in this study were the daily totals of global radiation on a horizontal surface, diffuse radiation on a horizontal surface and global radiation on a 45° tilted surface. The measured radiation using microprocessor based weather station was compared with the computerized results obtained from two widely used models for estimating total radiation on tilted surfaces. These are the isotropic model and Hay’s anisotropic model. The study showed that the models are in good agreement with the isotropic model producing slightly better results during the summer months. Hay’s model resulted in better results for the rest of the year.