Global solar radiation over Turkey: comparison of predicted and measured data

In this study, various regression analyses were applied to estimate monthly mean solar radiation in Turkey, by using n/N and n/Nnh parameters. Also, equations which represent two periods of the year, winter and summer, were developed by using these parameters. The equations developed by using n/Nnh ratio showed good results for the whole country, but, those which included n/N ratio at different cities showed better results. Even better results were obtained when the equations were applied to the summer and winter. In addition to RMSE and MBE statistics, the t-test method and the harmonic analysis were employed to prove that the results are reliable.