Impact of surface coating on freshwater generation from solar stills: a comprehensive review

Water is essential to sustain human life, yet despite its global abundance, access to potable water remains a significant challenge. The vast majority of accessible water is saline or brackish, making it unsuitable for human consumption. To address this issue, solar stills have recently received significant attention and research due to their simple design and low cost. However, their low productivity remains a critical limitation. Currently, findings suggest that coating solar still’s absorber plate and cover with nanoparticles can effectively enhance their performance. This review primarily focuses on studies from the last decade that explore the influence of metal oxide, metal, silicon-based, carbon-based, and composite nanoparticles on solar still performance. It is the first review to systematically analyze the influence of nanocoatings on water yield enhancement while also offering in-depth insights into the cost, durability, scalability, and environmental impacts of nanocoating applications in solar stills. While prior studies have primarily employed nanofluids to raise the water temperature, recent findings indicate that coating the absorber plate with nanoparticles can significantly enhance evaporation rates, leading to a substantial improvement in performance without the stability concerns associated with nanofluids. Furthermore, coating the cover has been shown to improve the wettability of the condensation surface and change the condensation mechanism from filmwise to dropwise, thereby further enhancing the productivity of the solar still. The nanoparticle’s properties and concentration were found to play a crucial role in improving solar still yield. This review also highlights key trends, challenges, and future areas for research that could provide valuable insights for researchers in the field of sustainable water resources to further optimize the use of nanoparticles as a coating material in solar stills.