Performance enhancement of a double-slope solar still using paraffin wax in winter conditions

This study examines the thermal performance and productivity of a double-slope solar still at two water depths (1 cm and 3 cm), with and without paraffin wax as a Phase Change Material (PCM), under winter conditions in Pantnagar, India. Peak solar radiation reached 489 W/m² at 1:00 PM. The 1 cm water depth of conventional setup showed rapid morning heating but declined post-noon due to the absence of thermal storage. PCM integration in the 1 cm setup enhanced thermal regulation, sustaining higher basin temperatures and extending evaporation. Similarly, the 3 cm PCM system reduced afternoon heat loss compared to its conventional counterpart. The highest distillate yield of 560 ml is recorded in the 1 cm PCM configuration, a 9.8% improvement over the non-PCM setup. For 3 cm depth, PCM improved output by 8.3%, from 480 ml to 520 ml. Temperature trends confirmed enhanced afternoon thermal stability with PCM. Overall, PCM integration notably improves the solar still efficiency.