DAILY GLOBAL SOLAR RADIATION ESTIMATE BASED ON SUNSHINE HOURS

Monthly average daily global solar radiation data are essential in the design and study of solar energy conversion devices. In this regard, different empirical models based on Angstrom-Prescott model were selected to estimate the monthly average daily global solar radiation, H, on a horizontal surface for Terengganu state using only the sunshine duration. The hourly solar radiation data measured at Kuala Terengganu station during the period (2004–2007) were used to calculate the monthly mean values of H using selected models. The selected models were compared on the basis of the statistical error tests as the mean bias error, the mean percentage error, the root mean square error, Nash–Sutcliffe equation, correlation coefficient and the t-test. Based on the statistical results a new linear model H/Ho= 0.2207 + 0.5249 (n/N) based on modified Angstrom model is extremely recommended to estimate monthly average daily global solar radiation for Terengganu state areas and in elsewhere with similar climatic conditions areas where the radiation data is missing or unavailable. The present work will help to advance the state of knowledge of global solar radiation to the point where it has applications in the estimation of monthly average daily global solar radiation.