Our environment is changing, and changing fast, putting pressure on our hardworking scientists to come up with ever more ingenious ways of meeting the needs of humankind – like pulling drinkable water right out of the air, in this case.
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.
The salt has high affinity for water and will absorb so much vapour from the surrounding air that eventually a pool of liquid forms, said Renyuan Li, a PhD student at KAUST. “The deliquescent salt can dissolve itself by absorbing moisture from air,” he said.
Calcium chloride has great water-harvesting potential, but the fact it turns from a solid to a salty liquid after absorbing water has been a major hurdle for its use as a water capture device, said Li.
To overcome the problem, the researchers incorporated the salt into a hydrogel which can hold a large volume of water while remaining a solid.
“The hydrogel’s most notable aspects are its high performance and low cost,” says one of the team, Renyuan Li.
With an estimated 13 trillion tons of water vapour in the atmosphere, being able to harvest some of that water to keep people hydrated would be a major breakthrough, especially for the hundreds of millions without a suitable water source. It’s something numerous research teams are busy investigating.
And while calcium chloride has been looked at before, making it practical as a material for storing water has been difficult. Here the team helped solve the problem by converting the salt into a polymer so it keeps its shape until heated; additionally, carbon nanotubes would then help release the water.
Idea Of water from Air technology:
The idea is the device could capture water from the air overnight, then release it when heated during the day.
That’s exactly how the prototype tested by the researchers operated: 35 grams (1.23 ounces) of the hydrogel was able to capture 37 grams (1.31 ounces) of water during a night with a relative humidity of around 60 percent.
The next day, 2.5 hours of sunshine was enough to release 20 grams (0.71 ounces) of the water, which was collected in the device ready to drink. The hydrogel is then ready to use again, the researchers report.
However the scientists aren’t satisfied yet – they’re hoping to tweak the design so that water is released continuously.
There’s plenty of competition out there for these potentially life-saving devices, which we think is a good thing.
Earlier this year teams from the US demonstrated a device that used a specially engineered metal to capture water – this is another invention that doesn’t need a separate energy source to work.
Another team of scientists have created a synthetic material inspired by the Namib desert beetles, which also shows promise as a way of condensing and capturing liquid water from the air where needed.
With all these initiatives, the challenge is to get them from lab prototype into commercial product, but this new hydrogel-based device is ticking a lot of the necessary boxes.
“This type of atmospheric water generator is cheap and affordable, works perfectly with a broad range of humidity, does not need any electricity, and thus is especially suitable for clean water production in remote areas,” write the researchers.