Solar Device Makes 4 Liters of Drinking Water Per Hour

A floating device no bigger than a small table can now produce enough drinking water for a family in just one hour, using nothing but sunshine and seawater.

Researchers at South Korea's UNIST developed a solar-powered evaporator that transforms saltwater into clean drinking water without needing any electricity. The team, led by Professor Ji-Hyun Jang, designed the system specifically for communities in developing countries and remote islands where power grids don't reach.

The device works like nature's water cycle, only much faster. When placed on seawater, a special coating absorbs sunlight and heats the water to 80°C. The water evaporates, leaving salt and contaminants behind, then condenses into pure drinking water.

The numbers tell an impressive story. A one-square-meter setup produces 4.1 liters of clean water every hour. That's nearly seven times faster than seawater would evaporate naturally, making it the fastest oxide-based evaporator ever reported.

The secret lies in a new material the team engineered by mixing copper and chromium with manganese oxide. By carefully adjusting the chemical composition, they created a coating that captures 97.2% of the sun's energy, from ultraviolet to near-infrared light. Previous manganese oxide materials could only heat water to about 63°C, but this new version reaches 80°C, dramatically speeding up evaporation.

The design tackles a problem that has plagued solar desalination systems for years: salt buildup. The researchers shaped the device like an upside-down U, with special water-wicking fibers and a water-repellent fabric that help salt flow away instead of caking on the surface.

The Ripple Effect

Over 2 billion people worldwide lack access to safe drinking water, many living in coastal areas surrounded by seawater they can't drink. This technology doesn't just offer them fresh water. It offers independence from expensive desalination plants and unreliable power supplies.

The device's simple design means communities could potentially build and maintain these systems locally. No fuel costs, no electricity bills, no complex machinery. Just sunlight, seawater, and the same evaporation process that has powered Earth's water cycle for billions of years.

Professor Jang emphasized the breakthrough's practical potential: "Its scalability and stability mean it could be a practical solution to real-world water shortages." The team published their findings in Advanced Materials in December 2025, and the technology is now ready for real-world testing.

With water scarcity affecting more regions each year due to climate change and population growth, solutions that work off-grid are becoming essential lifelines for vulnerable communities around the world.