Deserts and many other arid areas have two things in common; lots of sun and minimal water. This has led to scientists attempting to change the status quo by any means, and according to an article in the journal Science, they may just have found the answer.

Researchers led by Omar Yaghi, a chemist at the University of California, Berkeley, and his colleagues researched a family of crystalline powders called metal organic frameworks (MOFs), porous crystals that form continuous 3D networks. In 2014, they synthesised an MOF that excelled at absorbing water, even under low-humidity conditions.

Yaghi then reached out to Evelyn Wang, a mechanical engineer at the Massachusetts Institute of Technology (MIT) in Cambridge, with whom he had previously worked, in order to work on a water-harvesting device.

This led to Wang and her students designing a system consisting of MOF crystals pressed into a thin sheet of porous copper metal which is placed between a solar absorber and a condenser plate and positioned inside a chamber.

The chamber is opened at night to allow it to diffuse the ambient air through the porous MOF; water molecules then stick to the interior surfaces of the chamber in groups of eight to form tiny cubic droplets. The chamber is closed in the morning; sunlight enters it via a window on top of the device, heating up the MOF and liberating the water droplets which are then driven towards the cooler condenser in the form of vapour. The vapour is then condensed as liquid water and drips into a collector, pulling up to 2.8 litres of water per day for every kilogram of MOF it contains.

The device is powered by entirely sunlight, so can be used anywhere, and is well-suited to deserts which are extremely sunny and hot during the day and cold at night.

According to Yaghi, the device is a major breakthrough: “This is the first device capable of water capture and delivery under conditions typical of arid regions, making it possible to water those areas.”

“I’d like to see water off-grid, where you have a device at home running on ambient sunlight and delivering water that satisfies the needs of a household,” he added.

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