Water Vapor: Researchers Capture Earth’s Most Abundant Greenhouse Gas With Zero Energy
Researchers in Zurich have developed a new zero-energy technology to capture condensation to boost potable water supplies as climate change wreaks havoc on the planet’s hydrosphere.
Its contribution to climate change is up for debate, however, water vapor is a powerful and abundant greenhouse gas. As global average temperatures continue to rise, evaporation of Earth’s liquid waters intensifies, morphing into vapor and fueling a heat-trapping feedback loop. One of climate change’s many dire impacts, the loss of freshwater sources for billions of people and wildlife, is a top concern. Because procuring freshwater supplies with desalination plants is highly energy-intensive, a search for viable alternatives has been underway.
A team of researchers at ETH Zurich have developed a condenser technology to help secure freshwater supplies for an estimated half billion people globally who experience continuous water scarcity. The condenser is reportedly the first one that requires no energy and can function 24 hours per day. Other zero-energy condensers exist but are limited to only nighttime water collection when dew forms, producing low yields.
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The ETH Zurich’s technology can work even in hot, full-sun conditions and requires no energy due to a specially coated glass plane, reflecting incoming solar radiation and radiating internal heat away from the device. The coating enables the device to cool to 15 degrees Celsius below the ambient temperature. Meanwhile, water vapor condenses into liquid water, and an extremely water-repellent coating releases the droplets into a collection container.
The reflective coating consists of specially designed polymer and silver layers, which cause infrared radiation to be emitted while the device self-cools passively. The researchers initially tested the device when the relative humidity was 90% and found that the system was practically capable of harvesting dew at a relative humidity as low as 65%. They found that the technology can produce at least twice as much water as current passive technologies based on dew-collecting foils.
Although the test run was performed at a small scale, the research team concluded that the technology could harvest up to 0.53 decilitres of water per square meter of pane surface per hour under ideal conditions.
“This is close to the theoretical maximum value of 0.6 decilitres per hour, which is physically impossible to exceed,” said Iwan Hächler, a doctoral student in the group of Dimos Poulikakos, Professor of Thermodynamics at ETH Zurich.
A key reason why the ETH Zurich team’s system doesn’t require energy is that they used an extremely water-repellent coating to the underside of the pane in the water condenser, which allowed for passive collection. Conversely, other technologies require the input of energy to wipe the condensation from the surface.
“In contrast to other technologies, ours can really function without any additional energy, which is a key advantage,” Hächler said.
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