Scientists discover how to get electricity from humidity using almost any material
As humanity searches for new forms of power generation, it turns out an endless, clean source has literally been all around us the entire time. It’s humidity, and engineers at the University of Massachusetts Amherst have figured out a way to harvest electricity from it using nearly any material.
“This is very exciting,” Xiaomeng Liu, lead author of the study in Advanced Materials that details their findings. “We are opening up a wide door for harvesting clean electricity from thin air.”
Right now, the “Air-gen” device is the size of a fingernail and generates only a fraction of a volt. Scaling it might be a monumental task, but it could revolutionize the way we power the world.
Human-Made Cloud
The same team of engineers previously discovered they could use protein nanowires synthesized by the Geobacter type of bacteria to continuously harvest electricity from air. What the new study shows is that any type of material will work as long as it has holes smaller than 100 nanometers (1/1,000th the width of a human hair). The “mean free path” of a water molecule, the distance it can go without running into another water molecule, is 100 nanometers. By making the nanopores smaller than that, the engineers caused water molecules in the upper part of the material to crash into the edges of the pores, creating a charge imbalance as they pass through to the lower part of the material.
“The air contains an enormous amount of electricity,” Jun Yao, the paper’s senior author, said. “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.”
Yao and UMass Amherst microbiology Prof. Derek Lovley realized that the “air-gen effect” is generic after testing a variety of materials, including wood and silicon. As long as the material has those nanopores, it can generate electricity from humid air.
24/7 Generation
Previous attempts at generating electricity from the air have lasted no more than a couple days. Air-gen produced continuous electricity for a week during the study period. And while other devices have required expensive synthesis of unique materials, the UMass team’s nanopore discovery can drastically change the cost equation.
“The idea is simple, but it’s never been discovered before, and it opens all kinds of possibilities.” Yao said, adding that different materials could work better in different natural environments such as deserts and rain forests.
No matter where an Air-gen is located, the surrounding air has some amount of humidity, meaning that unlike wind or solar power, the technique can harvest energy from the air nonstop no matter the conditions. The wetter the air, the better, but it can work anywhere.
“Imagine a future world in which clean electricity is available anywhere you go,” Yao said. “The generic air-gen effect means that this future world can become a reality.”
Scaling Up
In order to make it a reality, though, scientists would have to massively scale-up air gen. Yao told the Washington Post that it would take about a billion Air-gens at the current size to produce a kilowatt of energy, only enough to partially power a home.
“Hard to know what to make of this,” MIT materials chemist Donald Sadoway told the Boston Globe. “It’s not apparent what kind of practical numbers can emerge. Investors would ask what we can expect in terms of power output in watts and the cost.”
Yao said that given the lack of material limitations and the huge amount of electricity in the air, there’s a basis for broad-scale power. All it takes is making Air-gen bigger, and the device can generate enough electricity to power daily life.
“A general understanding is that the energy density is low (which can be intuitively understood that the air is very thin), so a single-layer of Air-gen has no way to compete with other power sources (e.g., solar, wind) for matched power volume,” Yao told Vice. “However, the beauty is that air is diffusive and filled in the entire vertical space, which means that we can stack many layers of air-gen devices in the vertical space to improve power (without taking up additional space footprint).
“So in principle, Air-gen can be more space efficient. Moreover, they can be engineered into varied form factors and neatly blend into the environment (even without one’s notice).”
Since they’ve now made the crucial discovery about materials, Yao and the team are now working to scale Air-gen.
“The entire Earth is covered with a thick layer of humidity,” Yao told the Washington Post. “It’s an enormous source of clean energy. This is just the beginning in making use of that.”
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