Estimation of Monthly Average Daily Global Solar Radiation on Horizontal Surfaces over Libya

A new set of regression coefficients for the Angstrom-type correlation for estimation of monthly average daily global solar radiation on horizontal surfaces in Libya have been presented. The regression coefficients were applied to data of bright sunshine hours obtained from 15 meteorological stations during the period between 1981 and 1987. The results were then compared with the correlations of Rietveld, Glover, and McCulloch and the measured data. Excellent agreement was found between the estimated and the measured values following the application of the new proposed regression coefficients.