Environment

Solar-powered harvester sucks drinkable water out of thin air

Researchers at UC Berkeley test a device that can pluck drinkable water from the air
Researchers at UC Berkeley test a device that can pluck drinkable water from the air
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The UC Berkeley researchers test the water-harvesting device prototype in Arizona
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The UC Berkeley researchers test the water-harvesting device prototype in Arizona
The key ingredient is metal-organic frameworks, which have such a high surface area that they can adsorb large quantities of water molecules from the air and release them easily
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The key ingredient is metal-organic frameworks, which have such a high surface area that they can adsorb large quantities of water molecules from the air and release them easily
Researchers at UC Berkeley test a device that can pluck drinkable water from the air
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Researchers at UC Berkeley test a device that can pluck drinkable water from the air

Although there are trillions of liters of water floating around in the air, it's not easily accessible for those who need it. Now engineers at UC Berkeley have developed a device powered only by the Sun that can pluck practical quantities of drinkable water out of thin air, and they've successfully field-tested it in the Arizona desert.

Although it's not the first device to try to wring water out of the atmosphere, UC Berkeley's harvester looks far more practical than systems like the Warka Water, and it seems to be further along in its development than others, such as those on the current shortlist for the Water Abundance XPrize.

The key ingredients in the UC Berkeley water harvester are materials known as metal-organic frameworks (MOF). These synthetic compounds are notable for their extremely high surface areas – a MOF the size of a sugar cube, for example, could theoretically be packing the surface area of six football fields. This makes them great for trapping and storing molecules from the air.

In this case, that molecule is – you guessed it – water, and to trap it the team used the zirconium-based MOF-801. The harvester sees a 2-sq ft (0.19-sq m) bed of this stuff placed inside a box, which is itself placed inside a clear plastic cube. Using the simple process of condensation, over the course of 24 hours the device can adsorb water from the air and then expel it for harvesting.

First, the lid of the box is left open to the air overnight, when the higher humidity lets the MOF grains suck in water molecules from the air. In the morning, the lid is replaced and the Sun heats the box up like a greenhouse, triggering the MOFs to release the trapped water vapor. This condenses on the walls of the outer box and runs down to the bottom, where it can be collected.

The field tests build on lab experiments from early last year, where the team tested a much smaller prototype using just 2 g of MOF with promising results.

The UC Berkeley researchers test the water-harvesting device prototype in Arizona
The UC Berkeley researchers test the water-harvesting device prototype in Arizona

For the new test run, the UC Berkeley team trialed the larger prototype in the Arizona desert, where humidity ranges from 40 percent at night down to just eight percent during the day. Using up to 1.2 kg (2.6 lb) of MOF-801, they found that the device was able to produce 100 ml of water per kg (1.5 oz per lb) of MOF, but the team says this harvest could be doubled using the same materials.

Using other materials, however, might be better in the long run. The researchers are also experimenting with using an aluminum-based MOF, which is not only 150 times cheaper than zirconium but can capture twice as much water. Future versions of the device could potentially generate over 400 ml (1.5 cups) of water per day per kg of MOF.

The end goal is to allow remote communities to essentially harvest their own clean water from thin air, without requiring any power sources besides the Sun.

"There is nothing like this," says Omar Yaghi, lead researcher on the study. "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."

The research was published in the journal Science Advances, and the team demonstrates the device in the video below.

Source: UC Berkeley

This water harvester can turn desert air into drinkable water

7 comments
Astolfus
I remember that some time ago explorers in the forest got water fixing a plastic or large vegetable leafs holded by 4 tree or bamboo branches at night time and in the morning some condensation water have been got.
tob
How can something be 150 times cheaper? I would think that 1 times cheaper is zero cost. I think you mean that it can be produced for less than 1% of the cast...
Daishi
I've seen other attempts at this but I don't think everyone realizes air conditioners already do this which is useful because many regions where this would be needed are also very hot. I found once source that said household central air units produce between 5-20 gallons of water/day. You could run the AC unit on solar power and collect the water. On the island of Bermuda they also have an interesting approach. Because being on a small island in the ocean limits fresh water supply all the houses have white roofs painted with lime that are designed to capture rain water.
Douglas Bennett Rogers
This would work well in the coastal valleys of Yemen, which have the world's highest wet bulb but little rain.
EZ
To Daishi: Unfortunately, there's no money it that. The only problem is using cheap aluminum is the aluminum part. It's toxic. I has been linked to a number of serious maladies, including Alzheimer's and Autism.
KenHudson
Are you familiar with Aqua Sciences company in Miami? They are world reknowned at emergency mobile pure water from the atmosphere, and have been involved for years at tragic catastrophic disasters such as earthquakes, etc. Saved hundreds of lives in Haiti.
ljaques
With all these new forms of water condensers around, has anyone stopped to figure out how much the humidity of an area would drop and how that would affect the the biosphere, both in terms of human comfort and plant lifespans?