Exploratory review of innovations in basin geometry of a hemispherical solar stills to increase productivity

Freshwater scarcity poses a serious challenge in many arid and remote regions, necessitating the development of low-cost, sustainable desalination technologies. This review focuses on enhancing the performance of hemispherical solar stills through geometric modifications of the absorber basin. While hemispherical solar stills already benefit from omnidirectional solar capture and efficient condensation due to their dome shape, productivity remains limited by basin-level thermal inefficiencies. To address this, the review categorizes recent innovations into four groups: corrugated basin liners, convex geometries, finned basins, and other unconventional basin shapes. Corrugated designs, especially when combined with reversed solar collectors and wick materials, demonstrated productivity improvements exceeding 90 % and thermal efficiencies over 75 %. Convex configurations—such as stepped convex and hemispherical liners—achieved gains up to 183 % when paired with phase change materials and wicks. Finned basins, optimized for spacing, orientation, and material (notably copper), enhanced heat transfer and evaporation, with some configurations boosting productivity by 74 %. Additional geometries, including concave and stepped-funnel basins, further improved thermal distribution and water output with minimal added complexity. These findings highlight that geometric optimization—particularly when combined with passive or thermal energy storage enhancements—can significantly increase distillate yield and economic viability. Such improvements position hemispherical solar stills as effective and scalable solutions for decentralized freshwater generation in water-stressed environments.