Recent developments in natural energy storage, porous, and wick materials used with solar stills for enhanced production, economic performance, and sustainability: A comprehensive review

Energy, fresh water, and the environment are among the most critical global challenges today and are essential for industrial and economic development. Although solar stills typically exhibit low efficiency, they remain one of the most viable technologies for addressing water scarcity in remote and arid regions due to their simplicity, affordability, and low maintenance requirements compared to conventional systems. Recent research has focused on enhancing the performance and reducing the production cost of solar stills by incorporating natural materials into the water basins. Natural materials have earned significant attention due to their sustainable, practical characteristics, they are widely available, cost-effective, often biodegradable, and environmentally benign. Several studies have explored the use of natural materials for various purposes: as thermal energy storage media to retain heat during peak solar hours and minimize losses, as porous materials to expand the evaporation surface area, and as wick materials to enhance evaporation rates. These materials offer a promising, eco-friendly approach to improving the sustainability and efficiency of solar distillation technologies. However, to date, no comprehensive review has been conducted focusing specifically on the use of natural materials for performance enhancement in solar stills. Accordingly, this paper presents a new and comprehensive review of natural materials employed in solar stills, with a focus on thermal storage materials, porous structures, and wick materials. The study includes a comparative assessment of past research, alongside economic and environmental evaluations, to derive valuable conclusions. The findings indicate that natural materials significantly improve the productivity of solar stills compared to conventional designs. The use of natural thermal storage materials showed the greatest improvement in productivity and still efficiency, followed by porous materials, and then wick materials. For instance, the use of natural thermal storage, porous, and wick materials enhanced daily yields of solar stills in the range of 10.1–159.1 %, 2.6–145.1 %, and 9.4–62.1 %, respectively. Similarly, the production cost was reduced by about 13.2–83.1 %, 7.2–45.8 %, and 8.1–32.7 % for systems incorporating thermal storage, porous, and wick materials, respectively. Natural thermal storage materials demonstrated superior cost-efficiency. Furthermore, the thermal efficiency of solar disrillers increased by 12.1–60.9 %, 15.6–51.1 %, and 14.2–70.8 %, respectively, using natural thermal storage, porous, and wick materials. This review serves as a valuable resource for researchers and practitioners aiming to optimize solar still performance and highlights the need for continued development and innovation in natural material applications to further advance their effectiveness and commercial viability.