Determining the appropriate conditions for the drainage process of a solar still

Premature drainage increases the amount of used saline water, increasing the transportation and purification costs of saline water. On the other hand, postmature drainage increases the salt concentration of the brine, which deteriorates the solar still performance and may cause salt perceptions. The present study aims to identify appropriate brine conditions for the drainage process and propose a layout for an automatic drainage process. Therefore, the effect of brine’s salt concentration and temperature on a pyramid solar still’s productivity is being investigated. Seven salt concentrations were investigated, and the brine and metrological conditions were measured. The results show that the higher the salt concentration, the lower the solar still productivity. The daily yield of solar still ranges 5778–4061 g/m²d for feedwater salinity 0.15–134 ppt, respectively. Therefore, the novelty or recommendation of this study is that if the brine salinity reaches 127 ppt, the brine should be drained to avoid the precipitate, regardless of the stored thermal energy in the brine. Also, if the brine salinity reaches 118 ppt and the difference between its temperature and ambient temperature is about 1℃, the brine should be drained.