Harvesting Water from the Air

A new water harvesting system, designed by a team at The Ohio State University, captures water directly from the air, much like a traditional dehumidifier might. Using hardware and supplies readily available at a local shop, the system was specifically designed for open-source use to help solve critical water access issues.  

Lack of clean drinking water is responsible for more deaths in the world than war—a striking fact that many in more developed countries may take for granted—making it one of the National Academy of Engineering’s “14 Grand Challenges for Engineering in the 21st Century.” 

“The motivation for this study is to provide a solution that would help us inch toward addressing this global challenge,” said Qudsia Tahmina, associate professor in electrical and computer engineering at OSU and a co-author of the study, “Comparing Elastocaloric Cooling and Desiccant Wheel Dehumidifiers for Atmospheric Water Harvesting.” 

Depending on the source, somewhere between 2 to 4 billion people don’t have access to clean water, added John LaRocco, lead author of the study and research scientist at OSU’s Wexner Medical Center Psychiatry and Behavioral Science Department. 

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“A lot of existing conflicts are exacerbated over water supply and control of rivers, lakes, and reservoirs,” he said. “Even in developed countries, infrastructure may not be as good or well maintained, affecting those on the lower end of the socioeconomic spectrum.”  

A key component of the team’s system uses a new technology called elastocaloric cooling. Early adopters of this technology, which emerged about eight years ago, have used the technique to find alternative refrigerants and dehumidifying techniques. Studying these advancements, LaRocco theorized the technology could be applied to water capture.  

The team chose the most used elastocaloric alloy, called nickel-titanium (NiTi), for its ability to undergo a massive rate of deformation in response to temperature variation. By holding the NiTi wires under tension, it was possible to achieve thermal equilibrium with local temperature. Then, when the tension is released, the wires revert to their original form, absorbing ambient heat and cooling their surroundings. This slight temperature change, when combined with a heatsink, can condense water at a much more efficient rate than traditional water capture methods.  

Tested against a traditional desiccant wheel system found in dehumidifier systems in 30-minute intervals, the NiTi system, on average, captured more water per watt per hour than the desiccant wheel system.  

“The accuracy and efficiency of the system might vary depending on the environment and depending on the components,” said John Simonis, co-author of the study and an OSU undergraduate student in electrical and computer engineering. “But that’s why it is so critical that this was an open-source project. People need to be able to adapt the system to their needs and their environment.”  

Making this project open-source was an intentional decision, so anyone can build this small system at home with relative ease. Overall, the system should cost around $100 in parts, or even cheaper if one were to use different materials. But there was some trial and error when determining the best materials.  

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“When you’re working in environments where the air is not going to be 100 percent pure water vapor, you’re going to have components that can corrode, and learning what materials work best was a huge engineering challenge that we had to endure,” Simonis explained.  

In the beginning, the team noticed that rust would accumulate in the system, causing the motor and other components to fail. Through trial and error, they found that standard stainless-steel screws worked best. They also used safe food-grade silicone lubricants, which added some additional waterproofing for the screws. In their exploration, the researchers realized most of these issues were a result of using incredibly cost-effective components. Another challenge is air circulation, which Tahmina believes can be optimized by using a more robust system with constant airflow.  

“We wanted to explore the lower end of the cost spectrum to try to keep it as cheap as possible,” Simonis said. “There’s a balance in finding a solution that is safe and effective while also maintaining that accessibility.”  

While that continues to be a challenge, the team’s mission for this phase of the project was to offer a step forward in the global water shortage crisis. OSU has patented a full-scale version of the project for industrial and commercial use.  

“We developed a proof of concept to see if the idea could work, and it does,” Simonis said. “Now this project is freely available for anybody to access online, not just research scientists, but also makers and hobbyists, who can take what we’ve given them and further innovate it.”  

Cassandra Kelly is a technology writer in Columbus, Ohio.