Comparative experimental evaluation of wood charcoal and cocopeat fillers in a pyramid-shaped solar still for enhanced desalination performance

Freshwater scarcity remains a persistent challenge in arid and coastal regions, necessitating cost-effective and energy-efficient desalination solutions. This study presents an experimental performance evaluation of a pyramid-shaped solar still (PSS) enhanced with porous fillers cocopeat and wood charcoal to improve distillate productivity. The PSS, fabricated with a black-coated stainless-steel basin and insulated with thermocol and foam, was operated using both tap and saline water under coastal climatic conditions. Incorporation of fillers significantly improved the thermal regime and overall yield compared to the base model. The charcoal–saline water configuration exhibited the best performance, achieving a daily distillate yield of 950 mL and a thermal efficiency of 23.17%, representing a 34% enhancement over the base saline-water case (17.3%). Cocopeat improved heat retention but resulted in slower evaporation and lower yield. The enhanced absorptivity of charcoal promoted higher basin water temperature and better energy utilization. All configurations produced very soft distillate (10–20 mg/L as CaCO₃), meeting WHO potable water standards. The findings demonstrate that low-cost filler materials, particularly wood charcoal, can significantly augment the thermal and distillation efficiency of PSS, highlighting their suitability for decentralized desalination in resource-constrained regions.