This Solar-powered Device Can Extract Water From Desert-dry Air

This small machine can pull liters of water out of the air using only sunlight. MIT photo from laboratory of Evelyn Wang.

California's brutal multiyear drought is over, at last. But the state and others in the West still face the long-term crisis of meeting a demand for water that is threatening to exceed its supply. And elsewhere in the world, including India, China and many other countries, billions of people are affected by a growing freshwater scarcity.

But imagine a future where we didn't have to worry about reservoirs and underground aquifers being pumped dry to provide enough water for the masses. That may not be too far off, thanks to a new solar-powered gadget that extracts water from the air.

Scientists at the Massachusetts Institute of Technology have built a water harvester that uses a special material called a metal-organic framework, or MOF, that was produced at University of California, Berkeley. The prototype has demonstrated the ability to pull 3 quarts (2.8 liters) of water out of air with just 20 to 30 percent humidity — a common level in arid places — over a 12-hour period. Other similar devices have required higher levels of humidity to collect water.

This water-harvester works so efficiently because of the crystals inside it. The MOF — specifically, MOF-801 — is made of zirconium metal and adipic acid, and its stiff, porous structure is great for storing gases and liquids. When air passes through the device, water molecules attach themselves to the interior surfaces of the structure. As sunlight heats the MOF, the water is driven towards a condenser, which converts the vapor to liquid that drips into a collector. The MOF can hold 20 percent of its weight in water.

UC Berkeley chemistry professor Omar Yaghi, inventor of MOFs and co-author of an article on the device published last week in the journal Science, called it "a major breakthrough" in harvesting water from low-humidity air in a press release. "There is no other way to do that now, except by using extra energy," he said. "Your electric dehumidifier at home 'produces' very expensive water."