Comparative evaluation of three solar radiation models

Abstract

A computer program written in FORTRAN code was used to calculate hourly-average solar irradiance by three different methods. The program is heavily based on SOLAR, a model developed at the University of Nottingham by Micallef and Colls. Two other solar radiation models, one by Topcu and Oney, and the other by Rangarajan et al., were included in SOLAR. The modified model is called SOLAR3. SOLAR3 was evaluated using empirical data obtained from the Institute of Marine Studies of the University of Plymouth in the United Kingdom. From the available data, the first seven days of each month from four different years, i.e., 1997-2000, were used. The empirical data consisted of basic meteorological data such as temperature, humidity, pressure, reflected and global irradiance, as well as sunshine hours. Only the relevant data was used in the analysis. When the modelled data were compared with the empirical data it was clear that SOLAR was superior to the other models. Nevertheless, the model tends to overpredict for summer months and underpredicts for cloudier winter months.