Improving the Performance of Simple Solar Still Using Sand: The Effect of Water Relative Height Inside the Sand

Today, due to the increasing demand for water and the non-renewability and pollution of fossil fuels, solar desalination is a sustainable altervative for water supply. The low performance of simple solar stills has made them one of the most research fields in the world. One of the methods used in this field is the use of energy storage materials such as sand inside the water-desalination basin. In this study, the effect of relative height of water in sand on the performance of a simple solar desalination plant has been studied. For this purpose, four solar stills were built in Esfarayen, Iran (latitude 36.20 and longitude 57.67) and the effect of relative height of water to sand and the capillary effect of water in sand were studied. The height of sand in the solar stills was 10 cm and the relative water to sand heights were considered 1, 0.75, 0.5 and 0.25. The experiments were performed for 4 days in late July 2020 for 16 hours every day. The results indicated that the sand containing solar still, in the state of full contact of water and sand (relative height=1), had the best productivity and thermal efficiency in comparison with the other cases that the water level was lower than sand surface. Therefore, it seems that placing sand in a solar desalination pond in full contact with water can be a good option to increase its efficiency.