Solar panels that make seawater into drinking water ^{CEFR B2}

Desalination is widely used from California to the Middle East, but common methods such as reverse osmosis and thermal distillation are energy intensive, require chemical pre- and post-treatment, and produce concentrated brine. That brine can raise local salt levels and lower oxygen in coastal waters, damaging marine ecosystems. Researchers at the University of Rochester offer an alternative that aims to avoid those problems.

Their system uses black metal panels etched with femtosecond lasers to create a surface that is both highly light-absorbing and superwicking. A laser-treated active region draws a thin film of seawater across the panel, where sunlight drives evaporation and leaves salts behind. The design channels those salts toward an untreated passive region, preventing salt buildup in the active area and allowing continuous operation without chemical additives. Tiny grooves were shaped so minerals slough off rather than form a crust, and the team exploited the coffee-ring effect to carry salts to the passive zone.

Laboratory tests with samples from the Pacific, Atlantic and Indian Oceans produced fresh water while directing leftover salts into the passive region for later collection. Instead of discharging harmful brine, the method deposits nearly 100% of salts as solids that could supply table salt and other minerals. In related work, hydrogen titanate nanoparticles embedded in the grooves helped isolate lithium from mixed salts, and tests with Great Salt Lake samples recovered about 50% of the lithium.

Lead researcher Chunlei Guo and colleagues published their findings in Light: Science & Applications and Journal of Materials Chemistry A. The research was supported by the National Science Foundation, the Bill & Melinda Gates Foundation and Worldwide Universities Network. Guo notes the technology has been demonstrated in small proof-of-concept devices and is inherently scalable, and the approach could reduce energy use, avoid chemical additives, reduce brine waste and help create more sustainable mineral supply chains.