Solar Water Harvester Produces Water from Air

By | Apr 14, 2017 04:32 AM EDT
Water from dry air

Water harvester built at MIT with MOFs from UC Berkeley. (Photo : MIT)

A solar-powered "water harvester" that produces water from air, including the dry air in desert climates, has been jointly developed by teams from the Massachusetts Institute of Technology (MIT) und the University of California, Berkeley (UC Berkeley).

Powered by sunlight, the harvester can pull liters of water from low-humidity air over a 12-hour period each day in conditions as low as 20 percent humidity, a level common in arid areas.

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The prototype was built at MIT using a special material -- a metal-organic framework (MOF) -- produced at UC Berkeley.

Under conditions of 20 to 30 percent humidity, the prototype was able to pull 2.8 liters of water from the air over a 12-hour period, using one kilogram of MOF. Rooftop tests at MIT confirmed the device works in real-world conditions.

"This is a major breakthrough in the long-standing challenge of harvesting water from the air at low humidity," said Omar Yaghi, one of two senior authors of the paper, who holds the James and Neeltje Tretter chair in chemistry at UC Berkeley and is a faculty scientist at Lawrence Berkeley National Laboratory.

"There is no other way to do that right now, except by using extra energy. Your electric dehumidifier at home 'produces' very expensive water."

Yaghi said one vision for the future is to have water off-grid, where you have a device at home running on ambient solar for delivering water that satisfies the needs of a household. He said this will be made possible because of this experiment.

"I call it personalized water," he said.

In 2014, Yaghi and his UC Berkeley team synthesized a MOF, which is a combination of zirconium metal and adipic acid that binds water vapor. He teamed-up with Evelyn Wang, a mechanical engineer at MIT, to turn the MOF into a water-collecting system.

Yaghi invented metal-organic frameworks over 20 years ago, combining metals like magnesium or aluminum with organic molecules to develop rigid, porous structures ideal for storing gases and liquids.

Since then, some 20,000 different MOFs have been created by researchers worldwide. Some hold chemicals such as hydrogen or methane.

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