Thermal performance enhancement of basin-type solar still coupled with mini solar pond and shallow solar pond in closed-cycle mode

Abstract

ABSTRACT Solar desalination is an appropriate and cost-effective technology for water distillation which requires solar energy as a heat source. Based on the previous studies, the effect of basin water depth of solar still coupled with shallow solar pond has not been performed yet. The optimum frequency of external heat supply to solar still during off-sunshine hours has been found missing in literature. The objective of present study is to enhance the nocturnal distillate productivity of solar still and is accomplished by increasing the basin water temperature during off-sunshine hours. The variation in basin water depth of modified solar still on the distiller output is studied. The individual and combined effects of shallow solar pond and mini solar pond integrated to solar still on the performance of still are studied. To achieve this, the solar still coupled with shallow solar pond in closed cycle mode (heat transfer through heat exchanger) and continuous flow mode (8 a.m. to 8 p.m.) are tested at various basin water depth of 4–7 cm. Further, the solar still with optimum basin water depth is integrated with shallow pond in continuous flow mode (8 a.m. to 8 p.m.) and mini pond in two-batch frequency mode (12 a.m. to 2 a.m. and 4 a.m. to 6 a.m.). A total cumulative distillate output of 3.5 kg/m2, 3.08 kg/m2, 3.18 kg/m2 and 2.96 kg/m2 with an enhancement of 2.94%, 14.5%, 20.85% and 16% was obtained for modified solar still (still integrated with shallow pond) with basin water depth of 4 cm, 5 cm, 6 cm and 7 cm respectively as compared to reference solar still. The cumulative productivity of 4.6 kg/m2 was obtained for modified still (still integrated with shallow pond and mini pond) with an enhancement of 43.75% over reference solar still.