Saving the World with 3 Liters a Day

Solar-Powered Device Pulls Water Straight from Desert Air

It sounds incredible and more like something you would find in science fiction instead of science journals.

Nevertheless, a team from the Massachusetts Institute of Technology (MIT) and the University of California, Berkeley, has invented a device that can pull water out of the air in any environment—even the desert! And, it only requires sunlight to do it.

A new twist on an existing idea

Dehumidifiers and other products already exist that can collect water from humid air. However, this process requires so much energy, it is like engineering very expensive drinking water.

The new device uses a specially designed metal-organic framework, or MOF, capable of drawing water out of the air. MOFs combine metals with organic molecules to form rigid, porous crystal structures that can store gases and liquids, including water.

According to Science, this device is capable of harvesting almost three liters of water in 12 hours in atmospheres with humidity levels as low as 20 percent. That means people living in the driest parts of the world could have a solar-powered appliance capable of providing all the water they need.

What the MOF?

MOFs themselves are not a recent invention. Omar Yaghi, a chemistry professor at UC Berkeley, developed the first MOFs over 20 years ago and now researchers have created more than 20,000 different versions worldwide.

A prototype MOF-based water-collection device is set up for testing on the roof of a building on the MIT campus. Courtesy Evelyn Yang, MIT

Each one has unique molecule-grabbing properties. By choosing different metals and organics, scientists can dictate the properties of each MOF, therefore controlling what gases bind to them, and how strongly they hold on and contain them.

For instance, a recently designed MOF that absorbs methane can be used as a high-capacity gas tank for natural gas-powered vehicles.

Teaming up from across the country

In 2014, Yaghi and his team synthesized a MOF that excelled at absorbing water. So Yaghi reach out to a colleague, Evelyn Wang, an associate professor of mechanical engineer at MIT. Having collaborated on other MOF projects, Yaghi and Wang agreed to work together to come up with a water-harvesting device.

“We wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device,” stated Yaghi. “A person needs about a Coke can of water per day. That is something one could collect in less than an hour with this system.”

A promising future

Solar Power

Although this solar-powered device shows promise, there is still room for improvement. The team hopes to tweak the invention so that one day it can be more efficient and affordable enough for broader use.

That could make future water harvesters not only cheap enough to supply water to people around the world, but even create farms in the driest deserts.

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