Something really remarkable has been accomplished by a group of engineers. A device that continually extracts energy from moist air may be crafted out of almost any substance, since there is no one optimal choice.
It is a development that is not yet ready for practical implementation, but its developers claim that it transcends some of the constraints that other harvesters have. All that is required of the material is to be pocked with nanopores with a diameter of less than 100 nanometers.
That’s about one-thousandth the breadth of a human hair, so it’s easier to say than it is to accomplish, but it’s really far simpler than anybody anticipated.
A group of researchers at the University of Massachusetts Amherst, headed by engineer Xiaomeng Liu, found that this kind of material has the ability to capture the energy created by small water droplets in humid air.
They have coined the phrase “generic Air-gen effect” to refer to their finding.
Artist’s impression of an Air-gen device. (Derek Lovley/Ella Maru Studio)
“The air contains an enormous amount of electricity,” says engineer Jun Yao of UMass Amherst. “Think of a cloud, which is nothing more than a mass of water droplets. Each of those droplets contains a charge, and when conditions are right, the cloud can produce a lightning bolt – but we don’t know how to reliably capture electricity from lightning. 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.”
If the name “Air-gen” rings a bell, it is because the team has worked on the creation of an air energy harvester in the past. However, an earlier version of their technology was dependent on protein nanowires that were produced by a bacteria known as Geobacter sulfurreducens.
It has come to light that the bacteria in question used in the past is not essential to the process.
“What we realized after making the Geobacter discovery 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,” Yao explains.
Nanopores are responsible for this trait, and the free mean route that water molecules take in humid air is used to determine the size of the nanopores. This is the maximum distance a molecule of water can travel through the air before it comes into contact with another molecule of water.
A very thin layer of material, such as cellulose, silk protein, or graphene oxide, is used to construct the Air-gen device that is used generally. Airborne water molecules may readily pass through the nanopores and make their way from the top of the film to the bottom; however, as they make their way through the pores, they collide with the pores’ sidewalls.
Because more water molecules pour into the top of the film, there is a charge imbalance between the two sides of the film. This is caused by the fact that they transmit charge to the substance, which results in a buildup.
Rising air causes more collisions between water droplets at the top of a cloud, which results in an excess of positive charge in higher clouds and an excess of negative charge in lower clouds. This generates an effect that is comparable to what we observe in clouds that produce lightning.
In this scenario, the charge has the possibility of being rerouted to provide power to smaller devices or stored in a battery of some form.
At this point, we are still in the first phases of the process. In the natural environment, the cellulose film that was tested had a spontaneous voltage output of 260 millivolts, while a mobile phone needs a voltage output of around 5 volts. However, since the films are so thin, it is possible to stack them to increase the size of the Air-gen devices, which will make them more realistically usable.
According to the researchers, the fact that the devices may be constructed using a variety of materials indicates that they are capable of being tailored to the environment in which they are going to be utilized.
“The idea is simple, but it’s never been discovered before, and it opens all kinds of possibilities,” Yao says. “You could imagine harvesters made of one kind of material for rainforest environments, and another for more arid regions.”
The next phase would be to put the devices through their paces in a variety of settings while also working to improve their scalability. However, generic air-gen impact as a whole is a reality, and the opportunities it brings are cause for optimism.
“This is very exciting,” Liu says. “We are opening up a wide door for harvesting clean electricity from thin air.”
You can read the research, which has been published in Advanced Materials.
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