The arid air of Death Valley may actually be a valuable water source

A small panel managed to extract a glassful of clean water from the bone-dry air of Death Valley in California, which suggests that the device could provide the vital resource to arid regions.

The atmosphere over extremely dry land can hold large volumes of water, but extracting this in significant quantities without power is difficult. In the past, researchers have come up with innovative ways to tap into this reservoir, such as fog-catching nets made from simple mesh fabrics or spider silk-like artificial fibres, but they have struggled to make them work effectively in real-world conditions.

Now, Xuanhe Zhao at the Massachusetts Institute of Technology and his colleagues have developed a power-free water-collecting device that is about 0.5 metres tall and 0.1 m across. It is comprised of a glass panel that contains an absorbent hydrogel, a jelly-like substance made from long-chain polymers, and lithium salts that can store water molecules.

The hydrogel, which was folded into an origami-like structure to increase its surface area, absorbs water at night. This then evaporates when the sun shines on the glass panel in the day. The device’s interior is coated in a special cooling material, where the evaporated water collects and drips into storage below.

Zhao and his team tested their device for one week in Death Valley, where humidity can reach as low as 5 per cent. For comparison, London’s year-round average is around 70 per cent. The researchers found that the device extracted up to 160 millilitres of water per day, enough to fill a small glass.

They estimate that eight of these panels could supply an average adult’s daily drinking water needs, which may be particularly useful in arid areas. “Because the design of this device is quite a compact structure, we believe that an even larger area of the device can supply the drinking water for a household for daily consumption,” says Zhao.

It is good that Zhao and his team have shown that the device works in the real world, says Daryl Williams at Imperial College London, but there could be problems if it was tested for longer than one week. “The outdoor environment is relatively hostile. We would want to see how the device behaves under those stress conditions, after three, six, nine months.”