The study focuses on the evaluation of global solar radiation on a horizontal level. The estimate of the solar layer was
made on the basis of mathematical model obtained from the relations of Angstrom–Prescott, Allen and Sabbagh.
The different proposed models have been implemented by using MATLAB and Excel. The models were evaluated
using MPE, NSE, RMSE and MBE. The outcome of this shows that the Angstrom–Prescott model is the most suitable
for the calculation of global solar radiation in the sites of Mongo with values of 5.887 kWh/m 2 . For the site of Bokoro, the Allen model is the most adapted for the calculation of global solar radiation which is 5.872 kWh/m 2 . On the other hand, the Sabbagh model is appropriate for the sites of Abeche, N’Djamena, Ati and Moussoro with respective values of 6.354, 5.742, 5.523 and 6.126 kWh/m2 . The obtained results show that the Sahelian zone of Chad has a good solar potential and consequently suitable for the exploitation of solar energy systems.

Global solar radiation, Meteorological parameters, Climatic zones