Innovative tubular solar still with triple evaporation stages and compound parabolic concentrator

Tubular solar stills represent a promising approach for advancing solar-driven desalination. A major limitation of conventional tubular solar still designs is the restricted evaporation surface compared to the condensation area. This study addresses that limitation by incorporating three troughs lined with black wick materials to expand the evaporation surface. A compound parabolic concentrator was employed to redirect solar irradiance toward the middle and lower evaporator surfaces, thereby reducing shading caused by the upper trough. Experimental evaluation was carried out for two configurations: the developed three-trough design and the conventional single-trough design. The developed design achieved freshwater yield of 3.45 L/m2day and efficiency of 38 %, with a production cost of $0.00774/L. In contrast, the conventional single-trough system yielded 2.552 L/m2day at 28.1 % efficiency and production cost of $0.00971/L. Employing three evaporators with the compound parabolic concentrator improved yield and efficiency by 34.19 % and 35.71 %, respectively, while reducing cost by 20.29 %. The system operates entirely off grid, making it suitable for rural deployment and scalable for commercial desalination applications.