New Metal Panel Turns Seawater Into Drinking Water Using Sunlight

Scientists Turn Seawater Into Drinking Water Without Dumping Brine

Two-thirds of the world’s population faces severe water shortages, according to the authors, yet the planet’s biggest water supply, the ocean, is undrinkable. Plants that strip out the salt exist, but widely used ones discharge 58 to 78 percent of the water they take in as brine, a harmful mix of concentrated salt and chemicals. A metal panel built at the University of Rochester produced fresh water from real seawater while locking away nearly all of the salt as a solid, with no liquid brine going back into the tank it drew from.

Described in the journal Light: Science & Applications, the device uses the sun’s heat to evaporate water, then collects the vapor as fresh water. A laser-etched surface pushes salt crystals toward the panel’s edges, so the working area stays clear without chemical additives. It held steady through a week of indoor testing on Atlantic Ocean water.

Still a lab prototype, the device was tested outdoors on a panel only about 1.2 inches on each side, far smaller than anything a community could use.

Real Seawater Clogs Solar Desalination Panels With Salt Crust

Earlier solar desalination designs often worked well in the lab because they were tested on artificial saltwater, which contains little besides table salt. Table salt dries into crystals with tiny open gaps, like a loosely stacked pile of sugar cubes, so water keeps flowing through. Real seawater also carries magnesium and calcium compounds that fill those gaps and harden into a crust. In the team’s comparison, a common absorbent material stayed clean on simulated seawater but caked over on the real thing. Past fixes, such as chemical additives, scraping, or overnight dissolving, either added steps or recreated the brine problem.

Deeper Laser-Etched Grooves Keep the Panel Clean

Using ultrafast laser pulses, the team etched parallel grooves and ridges into aluminum foil. The best-performing version absorbs about 92 percent of the sunlight hitting it, and the grooves pull water uphill in a thin film, the way a paper towel soaks up a spill. The fastest version sent water climbing about 3 inches per second at first.

Four versions had grooves roughly one to two human hairs deep. In a two-hour test on Atlantic Ocean water, the shallowest version clogged, its top half covered in salt and its evaporation rate down more than 45 percent. The two deepest versions stayed clean, because their wider channels carry more water, which stays less salty and can dissolve crystals trying to take hold.

Two natural effects push the salt aside. First is the coffee-ring effect, the same process that leaves a dark ring around a dried coffee spill: evaporating liquid flows toward the edge, carrying dissolved material with it, so salt builds up at the outer boundary of the wet area. Second, newly formed salt crystals soak up water, dissolve slightly at their edges, and regrow just beyond the old boundary, nudging the salt outward.

Solar Desalination Panel Captured Nearly All Salt Over Seven Days

Testing ran indoors on Atlantic water collected near Fire Island, New York. A solar simulator shone for eight hours and switched off for sixteen, repeating for seven straight days. In the lit hours, the panel turned about 74 percent of the incoming light energy into water vapor, and it kept evaporating water through the dark hours at roughly 40 percent of its daytime pace. Nearly all of the salt in that water stayed on the panel, and over a full day-night cycle the seawater feeding it never grew saltier, which is how the team concluded that no brine was released.

Scraped from the panel’s edges, the harvested salt held magnesium, potassium, and calcium, plus traces of gold, cesium, bromine, and uranium. Without further separation and purification, the authors wrote, it “may find limited use.” They note that harvesting useful minerals from seawater could also lower the cost of making fresh water. In a preliminary demonstration, a titanium-based coating let the panel pull out lithium, a metal used in rechargeable batteries.

On March 4, 2024, a small panel on a University of Rochester rooftop, tilted toward the sun hourly from 8:30 a.m. to 5:30 p.m., collected 9.3 grams of fresh water, less than a single tablespoon, plus a pinch of salt. The desalinated water’s salt levels fell well below World Health Organization and U.S. Environmental Protection Agency drinking-water standards. Samples from the Pacific near Los Angeles and from the Atlantic and Indian Oceans off South Africa’s Cape L’Agulhas gave nearly the same evaporation and salt-collection rates as Fire Island water, and the team says water from all of them can be used for drinking.

Cutting liquid brine out of desalination is the standout result here, and it held up through a week of continuous lab operation. Cost, longer-term durability, and output at community scale have not been tested, so the technology is a working prototype, not a ready supply. Even so, a design that returns no brine to the sea deserves a larger trial.

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Disclaimer: This article summarizes a published scientific study for general readers and is for informational purposes only. It is not professional, engineering, or medical advice. The findings come from a laboratory prototype and may not reflect results in real-world conditions. Readers should consult the original paper and qualified experts before drawing conclusions.

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