Drought buster: Solar tech extracts 3 liters of water from thin air daily

A team of researchers has developed a system that can reliably draw liters of water from thin air every day without requiring frequent manual maintenance.

The passive system is an advanced version of the solar-driven atmospheric water extraction (SAWE) method, which can continuously produce freshwater when sunlight is presented.

By improving the design to allow better movement of materials and efficient use of energy, the system can consistently produce 0.65 liters of freshwater per square meter per hour under standard sunlight and 90 percent humidity.

According to researchers at King Abdullah University of Science and Technology in Saudi Arabia, it also works in dry areas with humidity as low as 40 percent. The system is intended for off-grid freshwater generation and irrigation initiatives.

Self-switching solar harvester

Although the concept and technology for air-to-water water harvesting are not new, the current solar-powered systems are cumbersome.

Harvesters that run on solar electricity follow a two-stage cycle. Water is first drawn from the air via an absorbent substance, and once it is saturated, the system is sealed and heated by sunlight to draw out the water.

According to the team, both physical work and a switching system are needed to alternate between the two processes, which increases complexity and expense.

The new harvester created at KAUST doesn’t need either; instead, it can cycle constantly without assistance by passively switching between the two stages.

“Our initial inspiration came from observing natural processes: specifically how plants efficiently transport water from their roots to their leaves through specialized structures,” said Kaijie Yang, a post-doctoral fellow at KAUST and the lead on the study, in a statement .

Low-cost water solution

The team developed a new system inspired by a key idea: using mass transport bridges as a vital link between capturing atmospheric water and generating fresh water .

These bridges consist of vertical microchannels filled with a salt solution that absorbs water . The water-rich solution is drawn up the channels through capillary action, similar to how water moves up plant stems.

As the solution becomes concentrated, it diffuses back down, allowing the process to repeat and collect more water. According to researchers, the innovative design efficiently connects the open section for water capture with the closed section for freshwater production.

“By optimizing the transport of mass and heat within the system, we enhanced its efficiency and effectiveness,” said Tingting Pan, another post-doctoral fellow at KAUST who worked on the project.

Experiments conducted by the team revealed that each square meter produced two to three liters of water per day in the summer and one to three liters per day in the fall while the system was being tested in Saudi Arabia .

During the testing, the crew operated the system without maintenance for several weeks. Additionally, they demonstrated how it may be utilized as a direct point source for the irrigation of desert plants and Chinese cabbage.

“The materials we used were a water-wicking fabric, a low-cost hygroscopic salt and a plastic-based frame. We chose the materials for their affordability and availability, so we anticipate the cost is affordable for large-scale application in low-income areas,” said Qiaoqiang Gan, one of the study’s senior authors.

The details of the team’s research were published in the journal Nature Communications .