Scientists have developed a simple device that can capture water from thin air, and release it when warmed by sunlight. The advance could provide a secure new source of drinking water in remote arid regions, researchers said.
Globally, Earth’s air contains almost 13 trillion tonnes of water, a vast renewable reservoir of clean drinking water.
Trials of many materials and devices developed to tap this water source have shown each to be either too inefficient, expensive or complex for practical use.
The prototype device, developed by researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, makes use of a cheap, stable, nontoxic salt, calcium chloride.
To overcome the problem, the researchers incorporated the salt into a hydrogel which can hold a large volume of water while remaining solid.
They also added a small number of carbon nanotubes, 0.42 percent by weight, to ensure the captured water vapor could be released.
Carbon nanotubes very efficiently absorb sunlight and convert the captured energy into heat.
The team incorporated 35 grams of this material into a simple prototype device. Left outside overnight, it captured 37 grams of water on a night when the relative humidity was around 60 percent.
The following day, after 2.5 hours of natural sunlight irradiation, most of the water was released and collected inside the device.