Solar-Powered Device Can Pull Water Out of Thin Air, Even in Deserts

As a worldwide water crisis looms, engineers have invented a solar-powered harvester that can pull water out of thin air—even in dry, desert environments.
A team from the Massachusetts Institute of Technology and the University of California, Berkeley have created a device using a specially designed metal-organic framework (MOF) capable of pulling liters of water in conditions where humidity is as low as 20 percent, a level common in arid areas. Impressively, it only needs the power of the sun to operate.
This breakthrough was published in a paper Thursday in the journal Science.
There are already dehumidifiers and other products out there that can collect water from humid air. The process, however, can be energy-intensive and essentially leave you with "very expensive water," as senior author Omar Yaghi of Lawrence Berkeley National Laboratory put it in a statement.
The new device, however, "is capable of harvesting 2.8 liters of water per kilogram of MOF daily at relative humidity levels as low as 20 percent, and requires no additional input of energy," the authors state in their paper. That's about 2.8 liters of water in 12 hours.
"We wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device," Yaghi said. "A person needs about a Coke can of water per day. That is something one could collect in less than an hour with this system."
The Berkeley professor invented metal-organic frameworks more than 20 years ago. MOFs combine metals such as magnesium or aluminum with organic molecules to form rigid, porous structures that can store gases and liquids. More than 20,000 different MOFs have been created by researchers worldwide.
According to a news release, here's how this new solar-powered, water-collecting MOF works:
In 2014, Yaghi and his UC Berkeley team synthesized a MOF—a combination of zirconium metal and adipic acid—that binds water vapor, and he suggested to Evelyn Wang, a mechanical engineer at MIT, that they join forces to turn the MOF into a water-collecting system.
The system Wang and her students designed consisted of more than two pounds 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. X-ray diffraction studies have shown that the water vapor molecules often gather in groups of eight to form cubes.
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 vapor condenses as liquid water and drips into a collector.
When two-thirds of the world's population is experiencing water shortages, the water vapor and droplets in the atmosphere—estimated to be around 13,000 trillion liters—is a natural resource that could address the global water problem, the authors explained in Science.
The team noted that their harvester is proof of concept and has room for improvement. The current device can absorb only 20 percent of its weight in water. They hope to double that amount or tweak the invention so that it can be more effective at higher or lower humidity levels.
Still, as Yaghi pointed out, "this is a major breakthrough." This invention could enable people to have an off-grid water supply."
"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," Yaghi said. "To me, that will be made possible because of this experiment. I call it personalized water."
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided
<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided
<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>Trending
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Listen:
<iframe style="border: none" src="//html5-player.libsyn.com/embed/episode/id/17278520/height/45/theme/standard/thumbnail/yes/direction/backward/" height="45" width="100%" scrolling="no" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe><p><em>Reposted with permission from </em><em><a href="https://yaleclimateconnections.org/2021/01/college-course-teaches-students-how-to-be-climate-leaders/" target="_blank" rel="noopener noreferrer">Yale Climate Connections</a>.</em></p>By Daniel Raichel
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