Enhancement of single slope solar still using sand: the effect of sand grain size distribution

One of the ways to improve the performance of simple solar stills is to use energy storage materials to store energy during the day and use it at night. Several energy storage materials have been studied by researchers, one of which is the use of sand. In this research, the improvement of a simple solar still performance has been studied using sand with different grain size distribution inside its basin. For this purpose, four solar still were made in Esfarayen (latitude 36.20 and longitude 57.67), Iran, and the effect of sand grain size distribution on its performance was studied in four treatments. The height of sand and water was 10 cm and the average grain size of treatments was considered 6.9, 2.8, 1.1 and 0.7 mm. The experiments were performed for 4 days in mid-August 2020. The results showed that the sand-containing treatment with an average grain size of 2.8 mm had better productivity and thermal efficiency than other cases where the average grain size of the used sand was larger or smaller. Therefore, grain size distribution of the sand seems to affect the performance of simple solar stills and there is an optimal amount for grain size.