Nanopores are the secret to making electricity from thin air. Credit: Derek Lovley/Ella Maru Studio
Key points:
- Researchers have discovered a “magic number” needed to generate electricity from humidity in the air.
- The air-gen effect is when nearly any material can be engineered with nanopores to harvest cost-effective, scalable, interruption-free electricity.
- The technology relies on nanopores less than 100 nanometers in diameter.
A team of engineers at the University of Massachusetts Amherst has shown that nearly any material can be turned into a device that continuously harvests electricity from humidity in the air. The secret lies in nanopores less than 100 nanometers in diameter.
In work completed in 2020, the research team showed 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,” said Jun Yao, assistant professor of electrical and computer engineering at UMass Amherst, “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.”
That property is holes smaller than 100 nanometers, or less than a thousandth of the width of a human hair.
Yao and his colleagues theorized they could design an electricity harvester based around this number. The harvester would be made from a thin layer of material filled with nanopores smaller than 100 nm that would let water molecules pass from the upper to the lower part of the material. But because each pore is so small, the water molecules would easily bump into the pore’s edge as they pass through the thin layer. This means that the upper part of the layer would be bombarded with many more charge-carrying water molecules than the lower part, creating a charge imbalance as the upper part increased its charge relative to the lower part. This would effectually create a battery—one that runs as long as there is any humidity in the air.
“The idea is simple but it’s never been discovered before, and it opens all kinds of possibilities,” said Yao. “The harvester could be designed from literally all kinds of material, offering broad choices for cost-effective and environment-adaptable fabrications. You could image harvesters made of one kind of material for rainforest environments, and another for more arid regions.”
Additionally, since humidity is ever-present, the harvester could run 24/7 without the environmental considerations of solar and wind technologies.
“Imagine a future world in which clean electricity is available anywhere you go,” said Yao. “The generic Air-gen effect means that this future world can become a reality.”