Enhancing the Productivity of a Single-Slope Solar Still Using a Preheating System

Considering the dearth and limited supply of potable water for daily consumption globally, developing a desalination technique to produce water sufficient for the need has become imperative. This study examines the improvement of freshwater productivity in a single-slope solar still by incorporating a solar preheating system. The proposed design utilizes solar still distillation to preheat the feed water before it enters the distillation basin. This approach aims to increase the temperature gradient between the water surface and the glass cover, thereby accelerating the evaporation and condensation process. Experimental evaluations were conducted under varying climatic conditions and flow rates, with and without the preheater. We note that the productivity has improved at each flow rate as follows: at a flow rate of 1 L/min, the improvement percentage reached 96% (CLISS:130 g/hr and CLIPSS:170 g/hr), at a flow rate of 2 L/min, the improvement percentage reached 73% (CLISS:180 g/hr and CLIPSS: 220 g/hr), while the improvement percentage at 3 L/min became 61% (CLISS:240 g/hr and CLIPSS:290 g/hr.), and at a flow rate of 4 L/min, it reached 64% (CLISS:280 g/hr. and CLIPSS: 320 g/hr.), and up to a flow rate of 8 liters/minute, the productivity improvement percentage between the two systems reached 31% (CLISS:310 g/hr. and CLIPSS:340 g/hr.). The results showed that the preheated system significantly improved solar thermal performance and daily production, especially during the early morning and late afternoon hours. Compared to a conventional design, the preheated system achieved an overall productivity increase of 25% to 35%.