Desalination can help relieve water scarcity issues in areas with a steady supply of electricity. For regions without such power resources, a grid-independent solution has been devised by researchers from Ulsan National Institute of Science and Technology (UNIST), Republic of Korea, to fortify freshwater stocks.

The system described in Advanced Materials is a ternary oxide-based evaporator capable of efficiently using solar energy to drive evaporation. When placed on seawater, the device heats the water, causing it to evaporate and then condense into fresh drinking water — all without needing external electricity input.

It is also claimed to be the fastest oxide-based evaporator developed to date. Tests showed that a 1 m² system can produce about 4.1 liters of clean water in one hour — a rate nearly seven times that of the natural evaporation rate of seawater.

The ternary oxide was formulated by replacing parts of manganese in corrosion-resistant manganese oxide with copper and chromium. The photothermal material’s absorbing capabilities were adjusted across the solar spectrum by means of bandgap engineering, enabling it to absorb almost 97% of sunlight from ultraviolet to near-infrared. The resulting high-spectrum absorption offers greater heat production with surface temperatures reaching 176° F (80° C).

Salt buildup is prevented by the inverted U-shaped design with the photothermal coating on the part that absorbs water. This configuration propels salt ions toward the edges of the device, where they crystallize as solid deposits. Inclusion of a water-wicking fiber material and a hydrophobic polyester fabric help draw water while rejecting salt ions.