A mean hourly global radiation prediction in Moroccan sites

Morocco gives recently increasing importance to develop renewable energy. In fact, a lot of investment opportunities in the sector of solar thermal energy are offered. To establish this kind of technology, predicting hourly radiation received during an average day of the month is very important. This paper proposes a statistical comparison between measured data of mean hourly global radiation at two different climate regions located in Morocco and three predicting models. Statistical indicators which are root mean square error (RMSE), mean bias error (MBE) and correlation coefficient (R) are used. We noticed that the Collares-Preira and Rabl correlation as modified by Gueymard (CPRG) fits more closely the measured data in these two regions at the West (Casablanca) and the East (Ouarzazate) sides of Atlas Mountains. Collares-Preira and Rabl model (CPR) gives almost the same result as CPRG but the Whillier Liu and Joradan (WLJ) under-estimates the measured values at solar noon.