Enhancing solar still operation through rounded corrugated walls and basin with wick material, reflectors, and external condensation

Abstract

This study addresses significant thermal losses in conventional solar stills caused by direct solar irradiation on vertical walls, which elevate wall temperatures and dissipate heat to the environment. A novel design is proposed, integrating a front-positioned wick material to shield walls from solar exposure, reduce heat loss, and expand evaporation surface area via cascading feedwater. Mirrors were employed to intensify solar radiation on the absorber and walls. Elevated glass temperatures from enhanced evaporation/condensation cycles were mitigated using two strategies: (1) active cooling via a fan and copper coil to extract vapor, preheat feedwater, and lower glass temperatures; and (2) passive cooling using a phase-change material (PCM) composite infused with silver nanoparticles (Ag NPs) beneath absorber/walls to absorb and release thermal energy. The CCSS demonstrated a total freshwater yield of 4700 mL/m 2 , surpassing the CSS output of 2500 mL/m 2 —representing an 88 % enhancement in productivity. Integration of dual external reflectors (CCSS-R configuration) further increased daily yield to 6650 mL/m 2 ·day, corresponding to a 146 % improvement relative to the CSS baseline (2700 mL/m 2 ·day). Augmenting the system with an external condenser (CCSS-R-EC configuration) achieved peak performance, yielding 8000 mL/m 2 ·day—a 202 % increase over the CSS reference output (2650 mL/m 2 ·day). Notably, the external condenser alone contributed a 56 % incremental gain to the CCSS-R system. The PCM incorporation (CCSS-PCM configuration) elevated daily production to 7650 mL/m 2 , exceeding the CSS baseline (2600 mL/m 2 ) by 194 %. Moreover, thermal efficiency exhibited progressive gains across configurations: 47.2 % for the CCSS, 52 % for CCSS-R, 60.1 % for CCSS-R-PCM, and 61.3 % for CCSS-R-EC.