Enhanced vapor condensation by thermal redistribution on the evaporation surface in heat-localized solar desalination

Abstract

• The thermal redistribution method is proposed for improving vapor condensation. • The fabricated 3-dimensional evaporation could achieve high evaporation rate. • The condensation rate could be enhanced 30% by thermal redistribution. • The good performance in seawater enables long-term operation of the system. Due to the abundance and cleanliness, Solar energy has been used for desalination and demonstrated great potential to tackle the grand challenges of freshwater shortage. For more efficient solar evaporation, heat-localized solar evaporation was proposed in 2014, in which heat could be localized at the air–water interface. With the high energy efficiency and simple operation, heat-localized solar evaporation systems have drawn great interest recently, and much progress has been made in exploring new materials and structures for better evaporation performance. Especially, many three-dimensional evaporation structures have been proposed, which enhances the evaporation rate of such systems to be higher than 1.5 kg m -2 h −1 . However, most works focused on improving the evaporation part of such 3-dimensional evaporation systems, while the research on the condensation part are rarely seen, which could be more important for freshwater production. Here, we propose a method of thermal redistribution to improve vapor condensation by increasing the average temperature of generated vapor. We firstly prepared the 3-dimensional triangle-shaped evaporation structures with thermal redistribution, which could be bent at different inclination angles to promote evaporation. The vapor condensation performances were compared between structures with and without thermal redistribution, and results show that thermal redistribution could increase the condensation rate by about 30%. This attributes to the increased average temperature of the generated vapor, while low-temperature vapor could hardly condense in practice. This work presents the method of thermal redistribution, which could be further used to increase freshwater production in heat-localized solar desalination systems.