The air contains water. We call it humidity. Even in the desert, there is water in the air. Scientists have been working on ways to squeeze water out of the air to produce clean drinking water. They have developed a number of sorbent materials that harvest water from the air. The process is called atmospheric water harvesting, or AWH.
The challenge for AWH is that the new materials that are very good at capturing water are very reluctant to give it up. As a result, it takes heat and lots of time to collect water using AWH systems. Typically, it takes hours or even days to get the water.
Engineers at MIT have now come up with a way to quickly recover water from AWH materials. Instead of waiting for sunlight or applied heat to evaporate water out of the material, they use ultrasonic waves to shake the water out.
The ultrasonic device can be powered with a solar cell and when a sorbent material is placed on it, it emits ultrasonic waves that are tuned to shake water molecules out of the sorbent. With this technique, the device can recover water in minutes instead of hours. The solar-powered system could include a sensor that detects when the sorbent material is full and would automatically turn on whenever there is enough water to extract.
The researchers estimate that their ultrasonic design is 45 times more efficient at extracting water from a given sorbent material than previous thermal methods. The system is complementary with and can be an add-on to pretty much any sorbent material.
