Electricity out of thin air: Researchers stumble on way to tap electrical charge of water vapor

By JAMES PENTLAND

Staff Writer

Published: 07-06-2023 6:00 PM

AMHERST — What if all you needed to generate electricity was thin film material, microscopic fibers and air?

Researchers at the University of Massachusetts have proved it can be done, and now they’re showing that many different kinds of materials can be used for the “Air-gen” device.

“The air contains an enormous amount of electricity,” said Jun Yao, an assistant professor of electrical and computer engineering who directed the research.

Humidity is the source of this power. For example, as Yao explained in an article on the UMass website, each water droplet in a cloud contains a charge, and when conditions are right, the cloud can produce a lightning bolt.

“What we’ve done is to create a human-built, small-scale cloud that produces electricity for us predictably and continuously so that we can harvest it,” Yao said.

Yao and co-author Derek Lovley showed back in 2020 that electricity could be continuously harvested from the air using a specialized material made of protein nanowires grown from the bacterium Geobacter sulfurreducens.

“What we realized after making the Geobacter discovery,” Yao said in the UMass article, “is that the ability to generate electricity from the air — what we then called the ‘Air-gen effect’ — turns out to be generic. Literally any kind of material can harvest electricity from air, as long as it has a certain property.”

What it needs are holes smaller than 100 nanometers, or less than a thousandth of the width of a human hair. These tiny holes are wide enough to allow water molecules to pass through, but not without bumping into the sides and so generating a charge.

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Yao noted that the researchers’ “aha!” moment was the result of an accident. Graduate student Xiaomeng Liu was working on an electric sensor using nanowires. One time he forgot to plug it in and realized it was still producing an electrical signal. Liu is still working on the Air-gen project, at least until he finishes his time at UMass in the next year.

The basic device — the size of a fingernail and one-tenth the thickness of a human hair — consists of a thin film full of tiny holes exposed to the air on top, a layer of nanowires or fibers underneath, and a bottom layer that’s sealed.

The top layer, where the water molecules are more excited, generates more of a charge than the bottom layer, creating a differential that is the basis of an electrical charge. The tiny device generates enough charge to power a small LED.

“We’re making all kinds of nanowires,” Yao said in his lab Thursday, citing cellulose and silk as materials capable of producing strands that are thin enough. “All have the same effect.”

The usefulness of a wide range of materials broadens the discovery’s commercial potential, and Yao believes the Air-gen could be scaled up to power electronic devices, appliances, even whole homes. The process would involve stacking hundreds or thousands of layers, leaving an air gap between each layer. A home might need a device the size of a minifridge.

Such a power source could be used anywhere, anytime — it doesn’t rely on electric power, the sun shining or the wind blowing. Even in the desert there is humidity, though Yao said different materials may be more suited to different environments.

Besides the logistical hurdles to scaling up production — material production, engineering strategies — Yao said the big question is whether the university can get sustainable funding to develop the technology.

Yao, 42, said he’s not concerned about his ideas being “stolen” or used by outsiders for profit (UMass owns the intellectual property rights on the discovery).

“We hope our research has an impact,” he said. “We hope others join in the study.”

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