This Solar-Powered Device Pulls Drinking Water From the Ocean — Without Creating Harmful Waste
More than two billion people on Earth don't have reliable access to clean drinking water. Meanwhile, oceans cover about 70 percent of the planet's surface — so the problem isn't a shortage of water, it's a shortage of water without salt in it. Removing salt from seawater, a process called desalination, has been around for decades, but existing methods are expensive, energy-hungry, and leave behind a nasty byproduct. Now, a team at the University of Rochester has developed a solar-powered system that could change the equation — producing fresh water cleanly, efficiently, and without harmful waste.
Traditional desalination plants work either by forcing seawater through ultra-fine filters under high pressure, a method called reverse osmosis, or by boiling the water and collecting the steam. Both approaches require significant amounts of energy and often use chemicals to prepare the water before treatment. Most importantly, they produce large volumes of brine — highly concentrated saltwater — that gets pumped back into the ocean. Brine raises the salt levels in surrounding water and lowers oxygen, which can damage marine ecosystems and harm the creatures living in them. Finding a cleaner alternative has been a major goal for scientists and engineers worldwide.
The Rochester team's solution starts with specially engineered metal panels. Using femtosecond lasers — devices that fire incredibly brief, precise pulses of light — researchers carved microscopic grooves into black metal surfaces. This laser texturing does two key things. First, it makes the metal absorb nearly all incoming sunlight, converting it efficiently into heat. Second, it gives the surface a property called superwicking, meaning it draws water across itself the way a sponge pulls up liquid. Together, these features allow the panel to use solar energy to evaporate seawater without any additional power source — just sunlight hitting a clever surface.
One of the biggest challenges in real-world desalination isn't just removing salt — it's stopping the equipment from getting clogged. In lab experiments that use simplified water containing only water and sodium chloride (regular table salt), crystals form in a loose and porous way that's easy to wash away. But actual ocean water contains a cocktail of minerals including magnesium and calcium, which form hard, dense crusts when they dry. Think of the white scale that builds up inside a kettle or on a showerhead — seawater produces the same effect, only much faster and more intensely. The Rochester team tackled this by designing the grooves in the metal panel to guide salts and minerals away from the evaporation zone before they have a chance to accumulate and cause blockages.
To keep the surface clean automatically, the researchers took inspiration from something many people have noticed without thinking much about it: the coffee ring effect. When a drop of coffee dries on a table, it leaves a ring at the outer edge because the water carries the coffee particles toward the edges as it evaporates. Professor Chunlei Guo and his team engineered the metal surface to replicate this effect deliberately, steering dissolved salts toward the edges of the panel — called passive regions — where the salts collect as dry solids and can be gathered later. When the team tested the panels with real seawater from the Pacific, Atlantic, and Indian Oceans, the self-cleaning mechanism worked consistently, and fresh water was produced continuously without interruption.
The solid salts collected by the system aren't just trash — they could actually be quite valuable. Conventional desalination sends brine back into the ocean as liquid waste. This new system recovers nearly all dissolved minerals as collectible solids. Among those minerals is lithium, a metal that is essential for making the rechargeable batteries found in electric vehicles and consumer electronics. Mining lithium from the ground is environmentally intensive and costly. The Rochester team showed that by embedding tiny particles called hydrogen titanate nanoparticles — particles so small they're measured in billionths of a meter — into the panel's grooves, they could selectively pull lithium away from the other salts. Testing this on water from Utah's Great Salt Lake, they recovered about 50 percent of the lithium present. That's a meaningful amount, and it points to a future where producing drinking water and harvesting battery materials could happen at the same time, from the same device.
The system is still in its early, proof-of-concept stage, meaning it has been demonstrated in small-scale devices but not yet built into large facilities. Professor Guo and his team believe the technology can be scaled up, and the research has received support from the National Science Foundation and the Bill and Melinda Gates Foundation — organizations that fund solutions with global reach. If this approach can be expanded, it could offer a path toward clean drinking water and critical mineral recovery for communities in coastal regions around the world, powered by nothing more than sunlight.
Source: ScienceDaily