Water-Level-Regulated Ridge-Structured Evaporator for Salt-Resistant Solar Desalination with Radiative Heat Recovery

Abstract

Solar-driven interfacial evaporation offers a promising route for decentralized freshwater production, yet salt accumulation, inefficient heat utilization, and limited vapor transport continue to restrict long-term operation and scale-up. Here, a ridge-structured evaporator (RSE) was developed by integrating carbon nanotube-loaded carbon felt with a simple 3D-printed double-ridge framework. The opposing inclined surfaces enabled surface-to-surface radiative heat recovery, while the ridge channels promoted water transport, airflow exchange, and vapor removal. More importantly, the salt crystallization pathway could be actively regulated by adjusting the contact height between the evaporator and the water body. Under low-water-level conditions, salt preferentially crystallized at the bottom of the central valley, thereby avoiding extensive coverage of the primary evaporation surfaces. Increasing the water level subsequently shortened the water-supply pathway and enabled complete salt dissolution within 2.5 h. Under one-sun irradiation, the RSE achieved evaporation rates of 1.74 kg m−2 h−1 in pure water and 1.27 kg m−2 h−1 in a 20 wt% NaCl solution. Outdoor 9- and 15-unit arrays maintained stable operation for 28 days, with maximum hourly water production rates of 0.196 and 0.341 kg h−1 in pure water and 0.189 and 0.316 kg h−1 in seawater, respectively. These results demonstrate a scalable and low-cost structural strategy for efficient solar desalination.