ИСТИНА

This paper is devoted to the development of the direct solar radiation analytical model and its application to determine the tilt of planar modules at an installation phase for maximization of the annual insolation of their surfaces. For evaluation, the Solar Photovoltaic (PV) modules have been chosen. The model is based on an improved analytical formula for air mass numbers for the sea level. The results of comparison of the ISO Standard Atmosphere with the improved air mass formula and with Kasten's approximation formula are provided. The cumulative simulation results of the tilt selections to maximize the annual insolations of the PV modules installed at the places with the different latitudes and with the different transparencies of atmosphere during the year are presented. The comparisons of our simulation results with Christensen and Barker's tilt estimations shows that their tilt estimation values are mostly located in the estimation ranges predicted by our model for the different transparencies of atmosphere. The paper also estimates the effect of the diffuse solar radiation on the tilt deviations. The estimation shows that to maximize the amount of the diffuse energy received by the planar module, its tilt also has to be deviated toward zenith.