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Scientists are trying to reproduce what happens in storm clouds
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- Author: Chris Baraniuk
- Rolle, BBC Future
7 hours ago
Nobody in the lab could believe what they saw. An experimental device, a humidity sensor, began generating electrical signals.
But that shouldn’t be possible.
“For some reason, the student working on the device forgot to turn on the power,” recalls Jun Yao of the University of Massachusetts Amherst.
“This is the beginning of the story.”
Since that moment five years ago, Yao and his colleagues have been developing a technology that can generate electricity from moist air, called hygroelectricity.
It’s an idea that’s been around for many years. The famous inventor Nikola Tesla (18561943) and others have investigated this possibility in the past, but never achieved promising results. But that could finally change.
Several research groups around the world are discovering new ways to harvest electricity from water molecules that are naturally suspended in the air.
This is possible because these molecules can transfer small electrical charges between themselves a process that researchers want to master.
The challenge is getting enough power so that the technology provides minimal benefit. But scientists now think they can get enough of it to power small computers and sensors.
Hygroelectricity holds the tantalizing prospect of a new form of renewable energy, the source of which may be floating all around us.
In 2020, Yao and his colleagues published a scientific paper describing how tiny protein nanowires produced by a bacterium were able to collect electricity from the air.
The exact mechanism is still up for debate, but the tiny pores in the material appear to be able to trap water molecules. As they rub against the material, the molecules appear to provide a charge.
Yao explains that in such a system, most molecules stay near the surface and generate a lot of electrical charge, while others penetrate deeper. This creates a charge difference between the outside and the inside of the material.
“Over time, you realize that charge separation is occurring,” says Yao. “It happens in a cloud.”
On a much larger and more dramatic scale, storm clouds also contain an accumulation of opposing electrical charges that eventually discharge in the form of lightning.
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Water molecules carry tiny electrical charges
Thus, by controlling the movement of water molecules and creating the right conditions for charge separation, it would be possible to generate electricity.
“The device can work literally anywhere on earth,” says Yao.
Yao and his colleagues published a new study in May 2023 in which they created the same type of structure, filled with nanopores, but using a variety of different materials from graphene oxide flakes and polymers to woodderived cellulose nanofibers.
They all worked, albeit with a few minor differences. This suggests that it is the structure that matters and not the material itself.
So far, devices thinner than a human hair have only produced very small amounts of electricity, equivalent to a fraction of a volt, in experiments.
Yao says that with bulkier material, it’s possible to get multivolt payloads.
He suggests that even a liquid sprayed onto surfaces could provide an instantaneous source of energy.
“I think it’s really exciting,” says Reshma Rao, a materials engineer at Imperial College London in the UK who was not involved in the study.
“There’s tremendous flexibility in the types of materials you can use.”
However, it may be unrealistic to imagine such technology powering entire buildings or energyhungry machines like cars, Rao warns.
Humidity may be just enough to power “Internet of Things” devices such as sensors or small electronics.
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Initially, it is believed that using humid air as an energy source would serve to power small devices such as sensors and smartwatches.
Yao’s team is far from the only one studying humid air as a potential energy source. In 2020, a group from Israel published that they managed to generate electricity by passing moist air between two pieces of metal.
Such a phenomenon was first recorded in 1840 when a train driver at a coal mine north of Newcastle, England, felt a strange tingling in his hand while operating the train.
He then noticed a small spark between his finger and one of the vehicle’s levers. Scientists investigating the incident concluded that the friction of the steam against the metal in the engine’s boiler led to the buildup of the charge.
Colin Price, an atmospheric sciences researcher at Tel Aviv University in Israel who coauthored the 2020 paper, says the charges generated in laboratory experiments using small pieces of metal were very small.
However, he claims that he and his colleagues are working to improve the system. However, one limitation could be that the group works with a minimum humidity of 60% in the experiments, while the devices of Yao’s group start generating electricity at a relative humidity of about 20%.
Meanwhile, a team in Portugal is working on an EUfunded project called CATCHER, which also aims to use humid air as an energy source.
Svitlana Lyubchyk, a materials scientist at Lusófona University in Lisbon in Portugal, is coordinating the project and cofounding a company called CascataChuva.
“I think the prototype will be ready by around the end of this year,” says Lyubchyk, while his son Andriy Lyubchyk, who is also a cofounder of the company, shows a video of a small LED light being turned on and off.
Holding up a gray disk of zirconia about four centimeters in diameter, he explains that this material can trap water molecules from moist air and allow them to flow through tiny channels.
He says a single disk generates enough electrical charge to provide about 1.5 volts. Just two discs are enough to power the LED light, he says, adding that many more pieces of material could be chained together to produce even more.
While some information about the work is available online, full details on the team’s recent experiments have yet to be published or peer reviewed.
The group also declined to share footage showing how the discs connect to the LED to power it.
Many questions remain about the mechanisms behind all of these hydropower inventions, says Rao.
“There’s a lot more to explore in terms of the fundamentals of why this works.”
There is also the issue of marketing. Anyone wanting to sell such technology must demonstrate that this form of energy production is competitive, selfsufficient and economically advantageous compared to other renewable sources, says Sarah Jordaan, a civil engineer at McGill University in Canada.
Jordaan examines the environmental and economic aspects of energy sources.
More established renewable energy technologies such as wind and solar clearly have the upper hand. They are likely to become even more important over the next decade, as the shift away from fossil fuels will be particularly urgent.
Despite these challenges, Rao says there is still a “glimmer of hope” that new technologies will emerge from hygroelectricity research.