A team of engineers from the University of Massachusetts Amherst (USA) has been able to generate continuous electricity from nothing. Rather, from the air. Not only that: they show that any material can become a good ‘harvester’ of this energy. It only has to have one feature: holes finer than the width of a hair. The conclusions have just been published in the journal ‘Advanced Materials‘.
“Air contains an enormous amount of electricity,” explains Jun Yao, an assistant professor of electrical and computer engineering in the UMass Amherst College of Engineering, and lead author of the paper. “Think of a cloud, which is nothing more than a mass of water droplets. Each of those drops contains a charge, and when the conditions are right, the cloud can produce lightning; however, we don’t know how to reliably capture the electricity from lightning.” But what can be controlled is a small-scale artificial cloud, which produces electricity in a predictable way »and whose energy we can harvest«, says Yao.
control artificial clouds
This is not a new concept: the same researcher together with Derek Lovley, professor of Microbiology at UMass Amherst, already raised in a study published in the journal ‘Nature‘ in 2020 that such energy could be harvested using a special material made of protein nanowires grown from bacteria Geobacter sulfurreducens. In other words, they turned this bacterium into a nanowire factory that was connected to electrodes in such a way that electric current was generated from the water vapor naturally present in the atmosphere. The device, dubbed Air-gen.
“What we realized after making this discovery is that the ability to generate electricity from air, what we later called the ‘Air-gen effect,’ turns out to be generic: literally any type of material can harvest electricity from air. , as long as it has a certain property,” says Yao. And that key property is the holes of less than 100 nanometers, or what is the same: pores of less than a thousandth part of the width of a human hair.
This is due to a parameter known as “mean free path”: the distance a single molecule of a substance travels, in this case water in air, before colliding with another molecule of the same substance. When water molecules are suspended in air, their mean free path is about 100 nm.
Harvesting energy from the air
Yao and his colleagues realized that they could design an electricity collector based on this number. This ‘harvester’ would be made of a thin layer of material filled with nanopores smaller than 100 nm that would allow water molecules to pass from the top to the bottom of the material. But, because each pore is so small, water molecules would easily hit the edge of the pore as they passed through the thin layer.
This means that the top of the layer would be bombarded with many more charge-carrying water molecules than the bottom, creating a charge imbalance, like a cloud, as the top increases its charge relative to the bottom. lower. This would effectively create a battery, one that works as long as there is moisture in the air. “The idea is simple, but it’s never been discovered before,” says Yao. It opens up all kinds of possibilities.”
A material for every need
This device could be designed from literally any type of material, offering vast options for cost-effective and environmentally adaptable fabrications. “There could be harvesters made of one type of material for rainforest environments and another for more arid regions, for example,” Yao says.
And since humidity is always present, this device would work 24/7, rain or shine, night and wind blowing or not, solving one of the main problems of technologies such as wind or solar, which only work under certain conditions.
Finally, because moisture in the air diffuses into three-dimensional space and the thickness of the Air-gen device is only a fraction of the width of a human hair, many thousands of them can be stacked on top of each other, efficiently increasing the amount of power without increasing the footprint of the device. Its creators claim that it would be capable of delivering energy at the kilowatt level for general use by electrical public services.
“Imagine a future world where clean electricity is available wherever you go,” Yao concludes. The Air-gen effect means that this future world can become a reality.”
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