A new solar-powered water harvester developed by KAUST uses a self-sustaining cycle inspired by natural plant processes to efficiently extract water from the air, requires no manual maintenance, and promises affordable water solutions for arid regions.

Even in arid regions of the world, the air is often humid. This moisture has the potential to provide water for drinking and irrigation. But extracting water from the air is difficult. KAUST researchers have developed a new technology that can continuously extract liters of water from the air every day without requiring regular manual maintenance.

Harvesting water from the air is not a new idea or new technology, but current solar energy systems are cumbersome.

Solar-powered combines operate in a two-stage cycle. The absorbent material first captures water from the air, and when saturated, the system is shut down and heated by sunlight to remove the captured water. Switching between the two stages requires either manual labor or a switching system, which increases complexity and cost. The new combine developed at KAUST does not need this; it passively switches between the two stages, allowing it to operate continuously without external intervention.

Innovative design inspired by nature

“Our initial inspiration came from observing natural processes: specifically, how plants efficiently transport water from roots to leaves using specialized structures,” says Kaiji Yang, a postdoctoral researcher who led the study.

This gave the team a key idea for their new system. “In our system, the public transport bridges play a crucial role as the link between the ‘open side’ for atmospheric water capture and the ‘closed side’ for freshwater production,” Yang explains.

Mass transport bridges are a series of vertical microchannels filled with a salt solution that absorbs water. The water-rich salt solution is drawn up through the channel by the same capillary action that draws water up through plant stems, and then the concentrated salt solution is spread back out to collect more water. “We increased the efficiency of the system by optimizing the mass and heat transfer within it,” says Tingting Pan, another postdoctoral researcher working on the project.

When testing the system in Saudi Arabia, each square meter produced 2-3 liters of water per day in the summer and approximately 1-3 liters per day in the fall. During the test, the team used the system for several weeks without requiring any maintenance. They also demonstrated that it can be used as a direct point source for irrigating Chinese cabbage and desert trees.

“The materials we used were drainage cloth, inexpensive hygroscopic salt, and a plastic frame. We selected the materials based on their availability and affordability, so we expect the price to be affordable for large-scale applications in low-income areas,” said Qiaoqiang Gang, one of the study’s senior authors.