Thermos‐hydraulic behavior under varying salinity conditions of a cascade solar still

Abstract The scarcity of freshwater is a major issue in arid regions of Algeria, where desalination represents a promising solution based on solar energy; this study focuses on experimental and theoretical investigation of a cascade distiller by focusing on the brackish water's salinity and the impact of its thermo‐physical properties on the production of distillate. Several experiments were conducted under real climatic conditions using different salinity levels (0.8, 21.6, 39.9, and 78.8 g/L). The theoretical approach was applied to analyze the influence of thermo‐physical properties of brackish water particularly the specific thermal capacity and latent heat of vaporization. These properties unlike pure water due to the presence of dissolved ions, which implies an estimated daily flow rate, increase of 3.2 to 3.7 kg/ day when the salinity exceeds 0.8 to 78.8 g/L. However in the experimental phase, productivity decreases from 1.75 to 1.25 kg/ day with the same variation in salinity. This decrease is mainly due to the formation of salt deposits on the absorbent surface, which reduces the absorption of solar radiation and the efficiency of heat exchanges. A good agreement between the experimental and numerical data was given with RMSE between 2.5°C and 6°C for all temperature components. The calculated of net present value 270 dollars confirms that the system is profitable investment. The study also based on the role of some key parameters such as the distiller's inclination, wind speed, brackish water thickness, allowing to optimize the design parameters to improve the productivity.