Modeling of monthly global solar radiation in M'sila region (Algeria)

The knowledge of solar radiation is important for many applications, especially for solar energy systems. In this study monthly variations of solar radiation of M'sila (a province of Algeria) were examined based on data measured during twenty years (1984-2003). In this paper, a determination of the number of years sufficient to estimate monthly global solar radiation among twenty years was done. Likewise, Weibull, Gamma, Normal, logistic, lognormal and loglogistic functions were used to estimate M'sila monthly solar radiation. In addition these functions were compared with the measured data. The performance of the cited functions were studied using statistical parameters such as correlation coefficient R2, root mean square error (RMSE), mean bias error (MBE) and mean absolute bias error (MABE). According to the results found, we can limit our study concerning the treatment of global solar radiation data, in M'sila region, to fifteen (15) years (from 1984 to 1998) instead of twenty (20) years (from 1984 to 2003). Lognormal distribution is the least favorable one to estimate monthly solar radiation on horizontal surface in M'sila region. In contrast, Weibull distribution is the best one.