And while a lot of research has focussed on desalination, a team of scientists have now come up with another possible solution – a device that pulls fresh water out of thin air, even in places with humidity as low as 20 percent.
Called the ‘solar-powered harvester’, the device was created by teams from MIT and the University of California, Berkeley, using a special type of material known as a metal-organic framework (MOF).
So far the prototype device has been tested under conditions of 20 to 30 percent humidity, and was able to pull 2.8 litres (3 quarts) of water from the air over a 12- hour period, using 1 kilogram (2.2 pounds) of MOF.
"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," said Yaghi.
Unlike regular sheets of metals, MOFs are structures where metals such as magnesium or aluminium are combined with organic molecules in an arrangement that creates rigid, porous structures ideal for storing gases or liquids.
The MIT team then took dust-sized crystals of this MOF and compressed them between a solar absorber and a condenser plate, and placed the whole thing inside a chamber that was exposed to the outside air.
Sunlight then heats the MOF up and pushes the bound water towards the condenser, which is the same temperature as the outside air.
This vapour condenses as liquid water, and drips into a collector to provide clean drinking water.
"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," said MIT team leader, Evelyn Wang.
"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," he added.