Isolating solar harvesting and water evaporation of salt-free Janus steam generator for concentration-independent seawater desalination

Abstract

Salt accumulation is one of the major obstacles to continuous and efficient solar seawater desalination (SSD). Despite the development of many salt-rejection strategies, the three key components (solar absorber, water transport, and vapor generation) of SSD coexisting in the same space and inevitably affect each other, resulting in performance damage or sacrifice. To address the issues, we separate the solar harvesting and water evaporation to eliminate their inherent and mutually destructive functional interference and allow them to be adjusted separately. Specifically, a low emissivity absorber coated on the aluminum sheet was used for light-to-heat conversion, the backside was bonded with non-woven fabric for water transport and evaporation, thus directly preventing salt deposition on the solar absorber. The rationally designed Janus evaporator exhibited a high evaporation rate of 1.707 kg m−2 h−1 under 1 sun irradiation. And no salt accumulation occurred during desalination of 15 wt% simulated seawater for 7 h. The Janus evaporator achieved continuous desalination of 3.5 wt% simulated seawater for 15 cycles (7 h each cycle) non-stop operation. All evaporator components are commercial, indicating its great potential for practical solar desalination of high salinity seawater.