In May this year, a group at the University of Massachusetts confirmed they had successfully created a small, continuous electrical current from humidity in the air. Tesla’s work of the 20th century inspired their project, with his theory that the Earth could act as a super battery, with the upper atmosphere and the planet itself working together. Despite his theory never being realised, it has given rise to an interesting and little explored area of energy – hygroelectricity.
The University of Massachusetts team achieved this by accident. With their original experiment designed as a sensor to detect humidity, it was mistakenly not provided with power. This led to the accidentally discovery of a faint electrical current being generated. The device itself was developed using many microscopic tubes and nanowires, each of which less than 1/1000 of the diameter of a human hair. This meant that they were wide enough that an airborne water molecule could enter, but too narrow for it to pass through. This caused the molecules to bump around the wire and becoming charged once the frequency of the bumps increased.
Professor Jun Yao, the study’s lead author, stated, “so it’s really like a battery…You have a positive pull and a negative pull, and when you connect them, the charge is going to flow.” Yao’s team are now working with nanopores instead of nanowires, which have millions of tiny holes to allow the flow of molecules. The current device used for their experiments can generate roughly one microwatt, enough to light a single pixel on an LED screen.
“The beauty is that the air is everywhere,” says Yao. “Even though a thin sheet of the device gives out a very tiny amount of electricity or power, in principle, we can stack multiple layers in vertical space to increase the power.”
There has also been a second team working on this project. Lisbon-based team and part of the Catcher Project, Prof Svitlana Lyubchyk and her twin sons, Profs Andriy and Sergiy Lyubchyk, are trying to recreate the same results achieved by Prof Jun Yao.
Catcher and related projects are now receiving nearly €5.5m (£4.7m) in funding from the European Innovation Council. They have seen moderate success, with their current technology consisting of a thin grey disc measuring 4cm (1.5in) across. One of these devices can generate 1.5 volts and 10 milliamps. However, 20,000 of them stacked into a washing machine-sized cube, could generate 10 kilowatt hours of power a day – roughly the consumption of an average UK household.
Both teams accept that it could take a long time, years at least, to optimise a prototype and scale up production. However, if they do see success then the result will be clear. Unlike other renewable energy alternatives, such as wind and solar, hygroelectricity could work at any time of the day, inside and outside. With the key being the interaction of water molecules, the sheer amount of energy stored within said molecules could be a huge breakthrough in accessible, renewable energy alternatives.
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