Estimating solar radiation for IRAN by using an optimum Model

Sunshine hours are the only long term, reliable and available measured information that can be used to reach highly accurate estimates of solar radiation values on the Earth surface. In this paper the sunshine duration is used to estimate monthly average daily solar radiation on a horizontal surface, it can be used to predict solar radiation in different climatic region of Iran. According to the Kopen classification of climate and considering the sunshine hours five climatic regions are identified for Iran. One of the best models that used sunshine duration to estimate monthly average daily solar radiation on a horizontal surface is the Angstrom model. Angstrom coefficients depend on geographical and meteorological parameters, The correlation equations developed are employed to calculate the monthly average daily global solar radiation for various location of Iran, By using the pyranometric stations solar radiation data(H) and the daily sunshine hours (n) will be measured sunshine recorders which were achieved by IRIMO and by calculating N,H0 from Angstrom equations and utilizing spss software,a regression relation for this five region of Iran has been obtained.