MIT tech to draw water from dry air
MIT has unveiled a new technology that can draw water directly from moisture in the air in the driest of locations.
The new method could be useful in virtually any location, regardless of humidity levels, using a passive system based on a foam-like material that pull moisture into its pores powered entirely by solar heat.
“There are desert areas around the world with around 20 percent humidity,” where potable water is a pressing need, “but there really hasn’t been a technology available that could fill” that need, says MIT associate professor of mechanical engineering Evelyn Wang.
The new system is based on a porous material from family of compounds known as metal-organic frameworks (MOFs).
These compounds form a kind of sponge-like configuration with large internal surface areas and can be made hydrophilic, or water-attracting, by tuning the exact chemical composition of the MOF these surfaces.
The material is placed between a top surface that is painted black to absorb solar heat, and a lower surface that is kept at the same temperature as the outside air.
Water is released from the pores as vapour, driven by the temperature and concentration difference to drip down as liquid and collect on the cooler lower surface.
Tests have shown that just one kilogram of the material can collect almost three litres of fresh water per day from very dry air with a humidity of just 20 per cent.
Such systems would only require attention a few times a day to collect the water, open the device to let in fresh air, and begin the next cycle, the researchers say.
“By carefully designing this material, we can have surface properties that can absorb water very efficiently at 50 percent humidity, but with a different design, it can work at 30 percent,” says researcher Hyunho Kim.
“By selecting the right materials, we can make it suitable for different conditions. Eventually we can harvest water from the entire spectrum” of water concentrations, he says.
“One vision for the future is to have water off-grid, where you have a device at home running on ambient solar for delivering water that satisfies the needs of a household. … To me, that will be made possible because of this experiment. I call it personalised water,” said MIT professor of chemistry Omar Yaghi.
The MIT team’s latest paper is accessible here, while more information is available in the video below.