Experimental research on transforming different functional thresholds to improve double slope solar still productivity

Abstract The scarcity of fresh water in developing regions necessitates low‐cost and sustainable purification technologies. Conventional solar stills, though economical and maintenance‐free, suffer from inherently low productivity due to limited thermal storage and inefficient utilization of solar energy. This study investigates the modified double‐slope solar still (DSSS) employing three design modifications with an iron wick, a binary eutectic phase change material (PCM) mixture of palmitic and stearic acid, and sandstone. The experimental analysis, conducted in Bhopal, India, under hot and dry summer conditions, compared these designs against a conventional DSSS. Results demonstrated that the PCM‐based still achieved the highest productivity of 2.841 L/m 2 /day, outperforming sandstone (2.505 L/m 2 /day) and iron wick (2.497 L/m 2 /day) configurations, and nearly doubling the yield of the traditional still (1.524 L/m 2 /day). Moreover, the incorporation of PCM enabled sustained evaporation during evening hours due to delayed heat release, while sandstone improved peak‐hour efficiency (20.43%) owing to sensible heat discharge. The use of an iron wick, although less productive than PCM and sandstone, provided improved evaporation kinetics at minimal cost. Overall, these findings confirm that integrating low‐cost materials such as binary eutectic PCMs, sandstones, and wick structures can significantly enhance freshwater output and thermal efficiency of solar stills. The proposed modifications not only deliver up to 86% higher distillate yield than conventional designs but also maintain economic feasibility, with fabrication costs ranging from USD 61.9–70.1. The developed configurations provide a scalable, energy‐independent solution for decentralized potable water production, specifically in remote, arid, and semi‐urban areas that have no centralized infrastructure.