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Amazing World

Moisture farms – Soon a reality?

Imagine standing in a desert and declaring that you can turn the sunlight into water. The image might seem like the claims of a fantastical prophet or magician, but as ever, science is performing its dead-ringer impersonation of magic yet again. Thanks to a new solar-powered invention, it is now possible to absorb moisture from the air and turn it into usable water – even in the extreme humidity of arid deserts!

You wouldn’t think there was much moisture to be found in desert air, but this device can produce nearly three litres a day per kilogram of its sponge-like absorber – and this is just a starting point. As with all new technologies, its creators hope to up capacity and efficiency as their work develops. In other words, it looks like Star Wars’ desert-based moisture farms are an approaching reality! These devices are quite literally the vaporators of Tatooine, meaning that once again, reality is catching up with science fiction.

Aside from the ability to live like Luke Skywalker’s aunt and uncle, this is a life-changing invention that could redefine deserts. With available water, settlements and even agriculture in the unused expanses of desert become a possibility. On top of this, those living in dry conditions and traveling miles for water could one day have it created and delivered to their homes, not only bringing relief and safe drinking water, but allowing those who spend their days travelling to wells to work or attend school. The more one thinks about it, the greater the implications of this little device are – and all using clean, readily available energy from the sun.

The research behind this breakthrough was led by Omar Yaghi, a chemist at the University of California, Berkeley. He was not the first to approach this line of thinking: there are around 13 trillion litres of water in the Earth’s atmosphere at any one time, and previous attempts to utilize this resource have been made. However, nothing has come close. Fine nets have been able to wick water away from foggy banks, and previous dehumidifiers have been able to pull it from the air in a similar fashion to Yaghi’s new device, but with two key differences: they weren’t successful in levels of extremely low humidity, and they are far too electricity-hungry to be sustainable, and especially to be usable in the developing world.

So, what is the secret? Yaghi’s research focused on a type of crystalline powders called metal organic frameworks, or MOFs. Yaghi had developed the very first MOFs – porous crystals that form continuous 3D networks – more than 20 years ago: since then, chemists have synthesized more than 20,000 types of MOFs, each with their own properties. However, in 2014, it was Yaghi and his colleagues synthesized a MOF that excelled at absorbing water, even under low-humidity conditions. They took this new zirconium-based MOF, dubbed MOF-801, to Evelyn Wang, a mechanical engineer at the Massachusetts Institute of Technology (MIT) in Cambridge.

Wang, who had also worked with Yaghi on previous MOF projects, and her students designed a system that presses a kilogram of dust-sized MOF crystals into a thin sheet of porous copper metal. That sheet is placed between a solar absorber and a condenser plate and positioned inside a chamber. At night, the chamber opens, allowing air to diffuse through the porous MOF – as it does, water molecules stick to the sheet, and in the morning, sunlight heats up the droplets and sends the evaporated vapour towards a solar-powered cooler condenser, where it cools into liquid water.

There is still room for improvement, both in capacity and cost. For example, zirconium costs $150 a kilogram, which makes Wang’s system too expensive for broad use. However, Yaghi’s group are working on a substitute for the material made of far more affordable aluminium.

If this invention can become affordable and widely used, the domino effect from the possibilities it opens up could be staggering for the developing world and all nations with vast expanses of desert. Best of all, 10% of the cost per unit currently sold goes towards providing cheap units for in-need locations!