The latest prototype was just tested successfully in the Arizona desert.
Water harvesting involves technology with the miraculous ability to net water from the air and transform it into the drinkable stuff. It's a concept that has always been practical in humid regions, where the air is moist. But water harvesting models rarely make sense in arid desert regions. That is, until now.
A team at the University of California at Berkeley have developed a new water harvester prototype that can pluck useful amounts of water from desert air using nothing but sunlight (something abundant in the desert) to power it, reports Phys.org.
The prototype was recently tested in the Arizona desert, where the relative humidity drops from a high of 40 percent at night to as low as 8 percent during the day. It was a preliminary model that utilized a highly porous material called a metal-organic framework, or MOF, that was made from the metal zirconium. The experiment produced about 200 milliliters of water per kilogram of MOF, or 3 ounces of water per pound.
It's an impressive initial result, but it's also one that the team expects to improve upon in a number of ways. For one, the zirconium used in the prototype is for testing purposes only; it's not cost effective. Researchers are already working on an aluminum-based MOF that is 150 times cheaper and captures twice as much water.
"There is nothing like this," said Omar Yaghi, who invented the technology underlying the harvester. "It operates at ambient temperature with ambient sunlight, and with no additional energy input you can collect water in the desert. This laboratory-to-desert journey allowed us to really turn water harvesting from an interesting phenomenon into a science."
Yaghi went on: "There has been tremendous interest in commercializing this, and there are several startups already engaged in developing a commercial water-harvesting device. The aluminum MOF is making this practical for water production, because it is cheap."
Putting the porousness of these MOFs in perspective, they can contain so many internal channels and holes that one the size of a sugar cube might have an internal surface area the size of six football fields. That's how they're able to squeeze water from even the driest of air. They are, in a manner of speaking, super-sponges. The harvester prototypes are so spongy that they can collect water even at sub-zero dew points.
The next test will involve the cheap aluminum MOF and will travel to Death Valley in late summer this year.
The study was published in the journal Science Advances.
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