Water securityNext-generation water harvester delivers fresh water from air

Last October, a UC Berkeley team headed down to the Arizona desert, plopped their newest prototype water harvester into the backyard of a tract home and started sucking water out of the air without any power other than sunlight.

The successful field test of their larger, next-generation harvester proved what the team had predicted earlier in 2017: that the water harvester can extract drinkable water every day/night cycle at very low humidity and at low cost, making it ideal for people living in arid, water-starved areas of the world.

“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, the James and Neeltje Tretter chair in chemistry at UC Berkeley and a faculty scientist at Lawrence Berkeley National Laboratory, and his team will report the results of the first field test of a water-collecting harvester in the June 8 issue of the journal Science Advances.

Berkeley says that the trial in Scottsdale, where the relative humidity drops from a high of 40 percent at night to as low as 8 percent during the day, demonstrated that the harvester should be easy to scale up by simply adding more of the water absorber, a highly porous material called a metal-organic framework, or MOF. The researchers anticipate that with the current MOF (MOF-801), made from the expensive metal zirconium, they will ultimately be able to harvest about 200 milliliters (about 7 ounces) of water per kilogram (2.2 pounds) of MOF, or 3 ounces of water per pound.

But Yaghi also reports that he has created a new MOF based on aluminum, called MOF-303, that is at least 150 times cheaper and captures twice as much water in lab tests. This will enable a new generation of harvesters producing more than 400 ml (3 cups) of water per day from a kilogram of MOF, the equivalent of half a 12-ounce soda can per pound per day.

“There has been tremendous interest in commercializing this, and there are several startups already engaged in developing a commercial water-harvesting device,” Yaghi said. “The aluminum MOF is making this practical for water production, because it is cheap.”