RESULTS AND DISCUSSION
The on-site (Hassi R’mel, Algeria) the average day temperature during 21st of March is equal to 20°C [32] which corresponds to the design conditions and selected as the reference day in the present study. The solar field subprogram calculates the supplied solar energy to HSSG, which according to Fig. 6 illustrates the variation of DNI during the day and shows that at midday its maximum reaches a value of 770 W/m2. Fig. 7 represents the subsequent solar thermal output during the day as it varies with the solar radiation from sunrise until sunset.