1999 Volume 64 Issue 519 Pages 31-38
The models for estimation of global irradiance on tilted surfaces are evaluated. The evaluation is undertaken on the basis of the comparison between estimated and measured values. Measured values at three of the Japanese IDMP sites; Sapporo, Tokyo and Fukuoka, are employed for the comparison. At first, the values of direct irradiation are estimated from the measured horizontal global irradiation using three direct and five diffuse irradiance models. Root Mean Square Error (RMSE) obtained from the estimations of Perez, Erbs, Chandrasekaran and Reindl models are comparatively small among the eight irradiance models. Next, global irradiation on vertical surfaces is estimated from measured normal direct and horizontal diffuse irradiations using an isotropic and five anisotropic sky radiance models. RMSE from the estimations of Perez anisotropic sky irradiance model is the smallest. Finally, global irradiation on vertical surfaces are estimated from the measured horizontal global irradiation using each of the 48 combinations of the eight irradiance and six sky radiance models. The combination of the Perez direct irradiance and the Perez anisotropic sky radiance models gives the smallest RMSE value.
