If you thought alternative sources of energy are limited to solar, geothermal, and wind, then think again. In a stunning display of ingenuity, bioengineers from Columbia University have recently published a report detailing the invention of an engine powered by the evaporation of room temperature water.
Published in the journal Nature Communications, the researchers explain how their engine is capable of powering LED lights and even a miniature car. According to lead bioengineer Ozgur Sahin, the engine measures less than four inches on each side and costs less than $5 to make.
This is a very, very impressive breakthrough. The engine is essentially harvesting useful amounts of energy from the infinitely small and naturally occurring gradients [in temperature]near the surface of water. These tiny temperature gradients exist everywhere, even in some of the most remote places on Earth.Peter Fratzl, a biomaterial researcher at the Max-Planck Institute of Colloids and Interfaces in Potsdam, Germany
How exactly does evaporation power this engine?
The key material making this technology possible is something called HYDRAs (short for hygroscopy-driven artificial muscles). The thin, muscle-like plastic bands that make up HYDRAs contract and expand to changes in humidity. Not only are these HYDRAs able to expand and contract more than a million times, they can also “almost quadruple in length.”
The engine works by placing it above a small puddle of room temperature water inside an enclosure. As the water evaporates, the engine soaks up the humidity, which then causes strips of HYDRAs to expand. These expanding HYDRAs are in turn connected to a cord that’s attached to an electromagnetic generator. As the HYDRAs expand, the cord’s movements are transformed into energy. As the HYDRAs initiate, they also trigger the opening of a set of four shutters located just above the engine to release the trapped humidity. As the humid air escapes, moisture is lost and the HYDRAs contract. This process is cyclical and somewhat similar to the mechanical operation of a combustion engine.
The bioengineering team also created a second, turbine-like engine that uses flattened flakes of HYDRAs that spin a wheel when bending in response to evaporation. Producing 50 microwatts, and as can be seen in the following video, these HYDRAs are able to move a miniature car.
Although this technology remains proof-of-concept and is nowhere near close to offering practical applications, Sahin is confident that the future of HYDRAs is promising: “The power in wind on a global scale primarily comes from evaporation, so there’s more power to be had here than there is in the wind.”