Optimizing a Single-Slope Solar Still for Fresh-Water Production in the Deserts of Arid Regions: An Experimental and Numerical Approach

Solar desalination is a promising sustainable solution to overcome the scarcity of fresh water in the deserts of arid regions. The productivity of a solar still depends mainly on its design parameters and the meteorological conditions of its location (longitude and latitude angles). Therefore, this study aimed to optimize the main design parameters of a single-slope solar still for freshwater production in the arid climate of the central region of Saudi Arabia (24°4′ N, 32.89° E). Experiments were conducted on four identical solar stills, with the same basin surface area and air gap distances (d) of 14, 16, 18, and 20 cm, respectively. The stills operated using three basin water depths (h) of 0.5, 1, and 1.5 cm on clear sunny days. The performance and productivity of the four stills were evaluated. The results showed that reducing the air gap distance (d) and water depth (h) significantly enhanced the distillate freshwater yield, and the optimum ratio of the length/width is 2 and of the back/front wall height is 3.65. Specifically, at a low water depth (h) of 0.5 cm, the daily distillate yield of the solar still increased by about 11% when the air gap distance (d) decreased from 20 to 14 cm. For the lowest air gap distance (d) of 14 cm, the distillate yield increased by about 23% when h decreased from 1.5 to 0.5 cm. Using the measured parameters, several numerical correlations have been developed to estimate the desalination rate (mc) as a function of the solar irradiance (Is) and ambient temperature (Tam). The developed correlations can be used successfully to estimate the values of mc instead of the prohibitive experimental measurements. The stills showed excellent performance in the arid climate and reduced water salinity from 31,250 to 495 ppm. This should encourage decision-makers to expand investment in solar desalination to sustainably develop the deserts of arid regions.