Researchers say they have solved the tricky problem of making a totally passive, 24/7 water generating system.
Excerpt from this story from Earther/Gizmodo:
As we look towards a Waterworld-esque future where our access to H20 is increasingly rare, it’s even more important to figure out how to squeeze every last drop we can, including out of thin air. In a study published Wednesday in Science Advances, a team of researchers from ETH Zurich demonstrated a new way to create drinking water from humid air.
There are lots of powerful atmospheric water generators on the market. But they still rely on technologies like fans that need external power. Passive water collection systems, meanwhile, are time-limited: They generally only work at night, when humidity is higher, and the water is in danger of evaporating back into the atmosphere when the sun comes up. There’s been a recent surge in techniques that use trays of materials, like gels, metals, salts, and other compounds to collect water when humidity is higher at night; the material is then naturally heated by the sun and releases the water it has collected. The downside of this technique, however, is that it’s not 24/7, and it’s not automatic. The team of researchers wanted to bypass all these systems’ various issues.
“We said, let’s try something that really doesn’t require any energy, so it’s really energy neutral and only limited by physical principles,” said Iwan Hächler, a PhD student at ETH Zurich and the lead author of the study. “We thought, ‘what if we show we can evaporate water? What if we try to condense it using radiative heat or radiative energy?’”
The resulting design is deceptively simple–it looks basically like a wide cone placed on top of a box, with a glass pane at the narrow end of the cone on top of the box. Each component here plays a key role.
Condensation happens when water in the air comes in contact with a surface that is below the ambient temperature. To ensure this process happens, researchers coated the glass pane with polymer and silver, allowing it to reflect the sunlight back and keep itself cooler than the ambient temperature. On the underside of the pane is a special coating where moisture from the air can collect and drop without requiring human or mechanical help. The cone acts like a radiation shield, which keeps the device from overheating and deflects the heat energy created from the condensation process.
