MIT researchers have created a high-tech “bubble wrap” that allows even Death Valley, the driest of North America, to collect safe drinking water directly from the sky.
The new water harvester is a major step towards providing safe and accessible drinking water to people around the world, working in places where it is possible to find water vapor in the air, scientists said in a new study published in Nature Water on June 11.
The water harvester is made of hydrogel (high-absorbent material) surrounded by two layers of glass like a window. At night, the device absorbs water vapor from the atmosphere. During the day, water condenses onto the glass thanks to the chilled coating. The liquid water drips down the glass and is collected into the tube system.
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Hydrogels are formed into special shapes. This is a series of domes similar to a sheet of bubble wrap that swells when absorbing water vapor. The dome increases the surface area of the material and increases the amount of water that can be held.
Researchers tested the new devices for a week at Death Valley, a unique Desert Valley that spans parts of California and Nevada. It is the hottest place in the world and the driest place in North America.
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We produced about two-quarters to two-thirds of water every day (57-161.5ml). In humid areas, the device should produce even more water. A representative from MIT said in a statement that the design is much more effective than previous attempts to collect drinking water from the air, without the need for electricity to power everything, and without electricity to enhance it.
The researchers also solved another long-standing problem with the quality of water collected using hydrogel design. Lithium salts, which in addition to hydrogels, increase water absorption, usually leak into water with a similar design and cannot be consumed without further processing of the water. This new design includes a salt stabilizer called glycerol, which reduces leakage to less than 0.06 ppm. This is an estimate from the US Geological Survey that lithium salts may be present in groundwater before they are unsafe to drink.
One panel may not produce enough water to maintain the entire household, but they do not take up much space. This means that multiple panels can be installed in a single household. Researchers estimate that eight 3-foot x 6-foot (1 mx 2 m) panels are sufficient to supply households to areas where safe drinking water is not easily accessible. Compared to the cost of bottled water in the US, the device was able to pay itself in at least a year in less than a month.
“Imagine one day we can unfold an array of these panels. The footprints are all vertical, so they are very small,” said Xuanhe Zhao, one of the authors of MIT and professor of both the departments of mechanical and environmental engineering at MIT, in a statement. “Now, people can build bigger or parallel panels to supply people with drinking water and make a real impact.”
The team plans to test the panel in an additional resource-limited environment to learn more about device performance under a variety of conditions.
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