Hourly Global Solar Radiation Estimates on a Horizontal Plane

The hourly global solar radiation (It) model strongly depends on the climatic characteristics of a considered site. In this paper, six empirical models were used to estimate the It from daily radiation on the eastern coast of Malaysia. The measured It data were obtained from the Malaysian Meteorology Department for the period of 2004–2008. In order to determine the performance of the models, the statistical parameters, normalised mean bias error (NMBE), normalised root mean square error (NRMSE), correlation coefficient (r), and a t-test were used. The It values were calculated by using the selected models. The results were compared with the measured data. This study finds that the Collares-Pereira and Rabl model performed better than the other models.