Imagine a world where even the driest deserts could provide clean drinking water. Such a reality could prove transformative for arid regions such as Saudi Arabia, the Atacama Desert in Chile, the Sahel region in Africa, and the Australian Outback. Yet even the air in these dry regions contains trillions of liters of water vapor.

Recently, researchers from MIT explained in ACS Energy Letters that a compact device can harvest such moisture.

Trapping water between fins

The researchers developed a novel design using an array of thin, adsorbent-coated fins to rapidly capture water even from arid air. By optimizing the spacing between these fins and using high-density waste heat for desorption, the device can cycle through multiple water harvesting rounds per day.

Xiangyu Li, Bachir El Fil and colleagues note that the approach significantly outperforms traditional solar-powered systems, potentially producing more than 5 liters of water per kilogram of adsorbent daily in environments with low relative humidity. At 30%, they note that it achieves 5.826 liters of water per kilogram of sorbent per day. The researchers optimized the device for extreme conditions, demonstrating effective water harvesting even at 10% relative humidity after balancing air gap thickness and vapor supply.

The researchers’ prototype consists of 10 small fins placed side by side on a copper base plate, each fin made of a 0.15 mm thick copper sheet sandwiched between two 0.6 mm thick layers of copper foam coated with the adsorbent material AQSOA Z02.

Promising results in tests

In tests, the fins saturated within 30 minutes and released the trapped moisture when heated to 90°C (194°F) using high-density waste heat. The researchers calculated that over 24 collection-release cycles, a compact 1-liter device containing 230 grams of the AQSOA Z02 adsorbent could produce up to 1.3 liters of potable water per day in air with 30% relative humidity. This translates to a yield of 5,826 mL of water per kg of sorbent per day, which is 2-5 times greater than previously developed devices.

In the study, the researchers anticipate further improvements to the device would be possible using advanced sorbent materials such as metal-organic frameworks (MOFs).