This new solar-powered device can harvest water from dry air
In a first, scientists have developed a new device that can harvest water from air everyday by using ambient sunlight, even in dry or desert climates.
Constructed at the Massachusetts Institute of Technology (MIT) in the US, the solar-powered device can work in conditions as low as 20 per cent humidity.
Omar Yaghi, from the University of California, Berkeley said, "This is a major breakthrough in the long-standing challenge of harvesting water from the air at low humidity".
Yaghi, also a faculty scientist at Lawrence Berkeley National Laboratory in the US said, "There is no other way to do that right now, except by using extra energy. Your electric dehumidifier at home 'produces' very expensive water".
The prototype, under conditions of 20-30 per cent humidity, was able to pull 2.8 litres of water from the air over a 12-hour period, using one kilogramme of a metal-organic framework (MOF) - a special material produced at UC Berkeley.
Rooftop tests at MIT confirmed that the device works in real-world conditions, researchers said.
Yaghi said, "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".
He said, "To me, that will be made possible because of this experiment. I call it personalised water."
The new system consisted of dust-sized MOF crystals compressed between a solar absorber and a condenser plate, placed inside a chamber open to the air.
As ambient air diffuses through the porous MOF, water molecules preferentially attach to the interior surfaces.
Sunlight entering through a window heats up the MOF and drives the bound water toward the condenser, which is at the temperature of the outside air. The vapour condenses as liquid water and drips into a collector.
Evelyn Wang, a mechanical engineer at MIT said, "This work offers a new way to harvest water from air that does not require high relative humidity conditions and is much more energy efficient than other existing technologies."