New Device Uses Solar Energy To Extract Drinking Water From Even The Driest Air

The water-harvesting device. Credit: Massachusettes Institute of Technology 

Free clean water is a dream longed for by many people living in dry climates, but as climate change worsens and droughts increase, access to drinkable water will become increasingly difficult. So where will they turn to for drinking water?

Part of the answer could lie in thin air, according to researchers from MIT. Alina LaPotin and colleagues have developed a device powered by the Sun that they claim grabs and condenses clean water from dry air. A description of the prototype is published in the journal Joule.

“In areas where water scarcity is a problem, it’s important to consider different technologies which provide water, particularly as climate change will exacerbate many water scarcity issues,” Alina LaPotin, from the Massachusetts Institute of Technology, told New Scientist.

The device uses a difference in temperature to move water from the air into adsorbent materials in the device, before condensing the water back out and into a container. Overnight, when there is no Sun to heat the device, water from the surrounding air gets drawn onto the surface of the adsorbent layer, from which the water can be harvested. As the Sun rises and heats the thermal plate on top, the difference in temperature from the exposed plate and the shaded underside draws water out of the adsorbent material (desorption), condensing it into a container.

Watch the device in action below. 

A timelapse of the device in action. Credit: Massachusettes Institute of Technology 

While this method has been proposed before, its water-capture abilities were too limited to warrant widespread use. This time the researchers improved on the technology by making it a dual-stage device, adding a second stage of adsorption-desorption. Furthermore, the researchers have tried to move away from specialist materials and employ more widely available options.

Still, the system requires further adjustments to boost production and lower costs before it can be deployed on a large scale. Currently, the device produces 0.8 liters of water a day – a marked improvement over previous iterations, but still under the 2.5 liters needed per day for a human to survive. Furthernore, depending on the availability of solar energy, humidity, and temperature, water production can be lowered below the 0.8 liters.

Fog harvesting requires 100 percent humidity to draw water out of the air and is currently employed in a few coastal deserts, but the conditions necessary for performance are limiting. The dual-stage improvements can work in humidities as low as 20 percent, which means it could be used in far drier climates.

Producing enough water to sustain a population is becoming ever more difficult for many nations across the globe. With areas such as California experiencing some of its driest years in recorded history, even wealthy areas may be impacted by a lack of freshwater in the coming years. 

“This is an interesting and technologically significant work indeed,” said Guihua Yu, a professor of materials science and mechanical engineering at the University of Texas at Austin, said in a statement. “It represents a powerful engineering approach for designing a dual-stage AWH device to achieve higher water production yield, marking a step closer toward practical solar-driven water production."


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