Experimental study of a hemispherical solar distillation system with and without rock salt balls as low-cost sensible storage: Performance optimization and comparative analysis

The significant heat losses from the solar distillers are the essential bottlenecks for their deprived performance. Minimization of the heat losses of the solar distillers by utilizing sensible storage materials has been proposed as a promising strategy. In this study, the potential of using rock salt balls as a low-cost sensible storage medium for augmenting the freshwater product of hemispheric solar still (HSS) is investigated. The influences of rock salt balls with a size diameter of 20 mm at different gap spacing of (3, 4, 5, and 6 cm) are investigated and compared to the conventional hemispheric solar still (CHSS) to determine the optimal arrangement of the rock salt balls that maximizes the freshwater production. The experimental results showed the utilization of rock salt balls with a spacing gap of 4.0 cm represents the optimal arrangement that maximizes the energic-economic performance of distillers. The accumulative freshwater reached 6.50, 7.0, 6.0, and 5.35 kg/day.m² for rock salt balls with gap spacing of 3.0, 4.0, 5.0, and 6.0 cm, respectively, compared to 4.70 kg/day.m² yielded by the CHSS. The improvement in freshwater for the utilization of rock salt balls reached 38.3 %, 49.0, 27.65 %, and 13.84, respectively. Furthermore, under these conditions, the enhancement in daily energy efficiency for using the rock salt balls is obtained as 55.92 %, 60.10, 51.46 %, and 45.98 %, respectively, compared to CHSS. The proposed hemispheric distillers using the rock salt balls show a 25.23 %, 31.0 %, 19.84 %, and 10.77 %, reduction in the cost per 1.0 L of freshwater than CHSS, respectively.