An experimental study on trapezoidal salt gradient solar pond using magnesium sulfate (MgSO4) salt and coal cinder

The salt gradient solar pond (SGSP) is used to store solar energy for low-temperature applications. This study investigates experimentally the density and temperature profile of Magnesium sulfate (MgSO4) in a trapezoidal-shaped SGSP. Four identical trapezoidal solar ponds were constructed by using plywood. The sides of the pond were completely covered with polythene sheets and given a black coating. The experiments were conducted using four identical solar ponds for seven days with different concentrations of magnesium sulfate and identified that the 16% concentration of MgSO4 (SGSP-M16) is the optimum concentration. Further, the experiment is extended to a 16% concentration of MgSO4 with coal cinder (SGSP-C). The temperature difference between the lower convective zone (LCZ) and upper convective zone (UCZ) is of about 13.7 degrees C and 17.6 degrees C for SGSP-M16 and SGSP-C, respectively. It is also observed that maximum temperatures of 54 degrees C and 59.1 degrees C in the heat storage zone for SGSP-M and SGSP-C, respectively. This higher temperature in SGSP-C is owing to the low volume heat capacity and low thermal diffusivity of the coal cinder.