This solar-powered box wrings water out of thin air and could help solve the problem of water shortages across the globe

Using a highly porous material, this experimental water-harvester can collect pure H20 from arid air

Thomas McMullan
11 Jun 2018
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A team of researchers at UC Berkeley has developed a potential solution to water shortages; a box that can harvest water out of desert air, without the need for any power supply other than sunlight.

The key to the device isn’t a pump or solar panel-operated tap, but rather the materials contained in the box. The chemist behind the project created a highly porous substance, dubbed a metal-organic framework, or MOF. As the name suggests, this is a crystal powder of organic and metal atoms designed to absorb water like a sponge.

Water molecules in the air get trapped into the MOF as the temperature decreases and the humidity increases overnight, and are driven out of the crystals as liquid morning as things warm up in the morning. The result is condensation that’s kept cool by a foil cover, producing a small cup of water.

“There is nothing like this,” professor Omar Yaghi, the chemist behind the harvester’s technology, said in a statement. “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.”

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At present, the MOF is made using the expensive metal zirconium, but further iterations are planned using an aluminium base. According to the researchers, this has allowed them to capture twice as much water in lab tests, at a cost that’s 150 times cheaper than the current prototype. If the aluminium MOF is a success in the field, it stands to produce more than 400ml of water per day from a kilogram of the material.

“There has been tremendous interest in commercialising 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.”

Billions across the planet struggle to find clean, drinkable water, and things are only going to get harder with the onset of global warming. Cape Town in South Africa, for example, has been teetering for the past few months around “Day Zero” – the day it runs out of water completely, whereas California has been suffering one of the worst droughts in the region since records began.

An inexpensive box for squeezing water out of arid air could be a crucial tool for fighting these hostile conditions. The results of the trial are published in Science Advances.

Image credit: UC Berkeley