Recent advances in water collection based on solar evaporation

Solar evaporation attracted lots of attention due to its environment-friendly and high efficiency, which is a potential approach to collecting fresh water. Many efforts have been made to improve the evaporation rate in the open space. While the actual water collection rate is far less than the evaporation rate, especially in passive water collection, limiting its practical and scalable applications. In this review, we focus on freshwater collection based on solar evaporation. Firstly, heat and mass transfer behaviors on the evaporation side were summarized to improve evaporation performance, including heat transfer processes in thermal radiation, convection, and conduction; mass transfer processes in water supply, evaporation enthalpy, and salt rejection. Sequentially, subcooling, wettability, and geometry of the condensation side were discussed to improve water collection performance, which should be designed collaboratively with the evaporation side in a confined space. Finally, thermal recovery and electricity generation beyond water collection were also introduced, and some challenges still need to improve in the further for scalable and practical applications, including passive water collection rate, integrated system, and long-term issues.