This paper develops a semi-empirical model to calculate direct solar shortwave irradiance on a horizontal surface for any cloudiness condition. The model is based on radiative transfer simulations combined with empirical relationships; it makes use of the global solar irradiance, experimentally...

Using experimental data collected at Uccle (Belgium) in 1980, new relations are proposed which allow the spectral density distribution of diffuse solar radiation on a horizontal surface to be estimated for clear skies, as a function of the commonly measured broadband global and diffuse solar...

Several years of measured data for 17 European locations have been used to develop models for estimating monthly mean daily values of diffuse radiation (Hd) from combinations of the following: clearness index, sunshine fraction, and solar declination. Two models giving the highest correlation...

In the present work the circumsolar and the point source version of the Perez model have been evaluated for South facing vertical surfaces at Madrid. Different data sets have been used. The coefficients Fij in the model have been determined using jointly experimental data obtained for vertical...

In the present work the circumsolar and point source versions of the Perez model have been evaluated for south facing vertical surfaces at Madrid. Different data sets have been used. The coefficients Fij in the model have been determined using joint experimental data obtained for vertical planes...

The study of monthly mean half hourly values of global radiation received at 315 (u.v.) and 545 nm (green) on a horizontal surface at Uccle (Belgium) in 1980 for clear (half hourly sunshine fraction σ = 1) and overcast (σ = 0) skies shows that for any solar altitude, global radiation received...

A new correlation is developed to predict monthly mean daily global radiation on horizontal surfaces for locations with latitudes between 60°N and 70°N. The suggested equation expresses global radiation in terms of per cent possible sunshine. The applicability of the new correlation is tested...