This paper deals with a daily solar storage system conceived and built in Laboratoire de Maîtrise des Technologies de l’Energie (LMTE, Borj Cedria). This system consists mainly of (i) a heat storage unit which consists of a wooden case with dimension of 5 m3 (5 m x 1 m x 1 m) filed with fin sand, (ii) a heat collection unit which consists of 5 m2 of south-facing solar collector mounted at a 37° tilt angle and (iii) a network of a polypropylene capillary heat exchanger with an aperture area equal to 5 m² buried inside the heat storage unit and connected to the heat collection unit. The circulation of the heated water between the heat collection unit and the polypropylene capillary heat exchanger allows heating the sand inside the heat storage unit. In order to evaluate the system efficiency during the charging period (during the day) and discharging period (during the night) an energy and exergy investigation were applied. Results showed that during the charging period, the average daily rates of thermal energy and exergy stored in the heat storage unit were 400 and 2.8 kW, respectively. It was found that the net energy and exergy efficiencies in the charging period were 32 % and 22 %, respectively. During the discharging period, the average daily rates of the thermal energy and exergy recovered from the heat storage unit were 2 kW and 2.5 kW, respectively. The recovered heat was compared to the total heat requirements of a tested room (4 m x 3 m x 3 m). The results showed that 30 % of the total heating requirement of the tested room can be achieved from the heat storage system during the whole night until in cold seasons.