Harvester Developed That Pulls Clean Water From Thin Air

by Edgar Hayes April 16, 2017, 0:47
Harvester Developed That Pulls Clean Water From Thin Air

The new device, detailed in Science, can produce nearly three liters of water over a 12-hour period, even if the humidity level hits 20 percent, which is typical of arid regions.

Omar Yaghi, a professor of chemistry at UC Berkeley said, "My aim is to have water off-grid where you have a device at your home running on ambient sunlight for delivering water that satisfies household needs".

Researchers at the University of California, Berkeley, have managed to separate water from atmospheric air using little to no additional energy.

'Your electric dehumidifier at home "produces" very expensive water'.

Crystalline materials similar to these can now harvest water vapor from the air. The new system is composed of dust-sized MOF particles which are compressed between a solar absorber and a condenser plate, which is placed inside a chamber which is left open to the air.

The MOF used is a combination of zirconium and adipic acid, which binds water vapour. As the water molecules heat up, they begin to vaporize again, slipping away from the porous material and eventually condensing again into reservoirs created to collect the water.

There are now more than 20,000 different types of MOF in use or in development around the world, but Yaghi's latest, developed with Evelyn Wang, a mechanical engineer at MIT, is the only one to target water.

Now the MOF can only absorb 20 percent of its weight in water but Yaghi and his team hope to double its efficiency in the future. However, other MOF materials could be altered, making it capable of absorbing 40 percent of its weight in water. He then resorted to Evelyn Wang, a mechanical engineer from MIT in Cambridge, who had worked with him on a previous project involving MOFs. Billions of people across the globe have limited access to clean water. Better yet, the new invention does not require electricity and the researchers are attempting to make the device as affordable as possible. Since then, he and others have developed several types of applications for them, including membranes that absorb and later release methane, acting as a carbon tank for cars.

Early testing showed the device can harvest 2.8 liters of water per kilogram of MOF each day.

The key to this new prototype, published today in the journal Science, are metal-organic frameworks, or MOFs.

But it's conceivable that someday if you're visiting Death Valley, one of the driest places in the United States, you'll be able to wet your whistle with a device based on Wang and Yaghi's concept. Titled "Water harvesting from air with metal-organic frameworks powered by natural sunlight", the paper describes the design of the device and its working.

But, as well as saving people stranded in a desert, the harvester could become a major part of everyday life, enabling people to have water without a connection to the public supply or a well. Many firms are using these MOF to produce water. The vapor condenses as liquid water and drips into a collector.

Obviously scaling up to eventual commercialization comes next."We did some estimates, and anticipate if you had a 30 liter unit, say the size of a carry-on suitcase, that's equivalent to 5 kg of MOF or so", said Wang.

Though that may not sound like much, its designers say the current device is just a prototype.

The entire device operates off ambient sunlight, Yaghi noted - no solar cells or external power sources are needed to make it work.


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