Just a week ago, I wrote about the dire need for safe water around the world and the role of universities in this fight. I’m happy to report that two universities have come up with yet another invention that will help alleviate the water crisis.
The device, which extracts water from dry air, is the brainchild of Omar Yaghi, professor of chemistry at the University of California at Berkeley, and Evelyn Wang, associate professor of mechanical engineering at MIT. All you need to power the device is sunlight, so it will be particularly useful in poor and remote areas that lack access to safe water. The device would come in handy in places with hot arid climate, such as Arizona and Texas. The Middle East, which is struggling with its current water resources, would also certainly benefit from it.
How does the device work?
The device uses metal-organic frameworks (MOF) invented by Yaghi two decades ago. MOFs connect metals, such as magnesium or aluminum, and organic molecules in rigid, porous structures that can hold storing gases and liquids.
Different metals can be combined with different organic compounds to create MOFs that would serve different needs. Since Yaghi’s invention, researchers around the world have created different MOFs to store chemicals, such as hydrogen and methane, and petrochemicals in processing plants.
In 2014, Yaghi and his lab team developed a MOF using zirconium metal and adipic acid, which binds water vapor. Yaghi then approached Wang with a proposal that they work together to create a water-collecting system using the MOF.
Wang and her lab team designed a prototype system that compressed about two pounds of dust-sized MOF crystals between a solar absorber and a condenser plate, which was then placed inside an open chamber. The MOF absorbs water molecules from the air, which turns into vapor during the day when sunlight heats it. The vapor escapes the MOF, and is channelled into an adjacent acrylic vessel where a condenser collects the water droplets and directs them into a collector.
The first of its kind
The system is the first technology with a practical solution for extracting water from dry air, according to Wang. The new technology is not limited by the constraints of fog harvesting, which requires a relative humidity of 100 percent, or dew harvesting, which is “extremely energy intensive.” Until now, “there really hasn’t been a technology available that could fill” the desperate need for potable water in “desert areas around the world with around 20 percent humidity,” Wang said in a statement.
MIT tests show that 1 kilogram (2.2 pounds) of MOF could collect about 2.8 liters (three quarts) of fresh water per day from very dry air with a humidity of just 20 percent. That is more than enough drinking water for one person in a day.
Improvements to come
MIT’s rooftop experiments have proved that the system can work in the real world, but the team is still working to improve the design and functionality. “To have water running all the time, you could design a system that absorbs the humidity during the night and evolves it during the day,” Yaghi said in a statement. “Or design the solar collector to allow for this at a much faster rate, where more air is pushed in. We wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device. 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.”
But TUN was assured that a viable product would come soon. “We could realize this device in the next 2-3 years,” Wang said in an email.
Wang also told TUN how she feels about the potential of the technology.
I am excited that with this device, we can help provide clean drinking water for people in remote areas with very limited infrastructure.