Performance of a stepped solar still using porous materials experimentally

Shortage of available freshwater has been becoming a critical issue, recently. For this matter, different types of solar still have been used to supply freshwater in rural places; however, their low performance is the main restriction. In this research, a stepped solar still is designed and built, and the steps are covered by wick porous material. This is a novel strategy for the stepped solar still. The distilled water productivity, the temperature of the internal space, first, middle and bottom steps as well as energy and exergy efficiencies are investigated experimentally. Experiments are carried out with porous material thicknesses of 4, 6, 8, and 12 mm and without porous materials in winter. Results indicate that the stepped solar still with a thicker porous medium has higher freshwater productivity and efficiency, and the temperature of internal space is affected by the presence of porous material as compared to no porous material. In addition, results show that the efficiency of stepped solar still with porous material thickness of 4, 8, 10, and 12 mm is 2.41%, 2.7%, 6.44% and 7.02% higher than the efficiency of the unmodified solar still, respectively. As a result, the porous material with a thickness of 12 mm is the optimal porous medium with productivity of one liter and thermal and exergy efficiencies of 24.71% and 3.528%. Graphical abstract