REVUE INTERNATIONALE D'HÉLIOTECHNIQUE N° 40 (2009) 12-17
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Statistical validation of daylength deFInitions for global solar radiation estimation
M. Chegaar1, Y. Sahnoune1, F. Guechi2
1L.O.C, Ferhat Abbas University, 19000, Setif, Algeria
2LAMA, Ferhat Abbas University, 19000, Setif, Algeria
The different daylength calculation procedures that can be employed to estimate solar radiation using an Angstrom–Prescott regression have not been sufficiently evaluated. In this study, monthly mean daily global solar radiation of four stations located in different geographical and climatic zones in Algeria were used to test three daylength estimation models using diffferent definitions of sunrise/sunset. Models were compared using the root mean square error (RMSE), the mean bias error (MBE) and the t-statistic.
According to our results, the most accurate model for the estimation of global solar radiation for the Mediterranean region sites (Algiers and Oran) with an RMSE=1.725 MJm-2day-1, MBE=0.029 MJm-2day-1 and the t-statistic=0.056 and for the Sahara part (Beni Abbas) is when the top of the sun is even with the horizon with an RMSE=0.922 MJm-2day-1, MBE=0.066 MJm-2day-1 and the t-statistic=0.239. For Tamanrasset, the best results are obtained when the centre of the sun is even with the horizon with an RMSE=1.268 MJm-2day-1, MBE=0.105MJm-2day-1and the t-statistic=0.277.
Keywords: daylength, solar radiation, statistical analysis