Engineers have accomplished a miraculous feat. Continuous energy harvesting from humid air is possible with almost any material.
It’s not at the point where it can be used in the real world, but its designers claim that it overcomes problems with other harvesters. Nanopores, or pores having a diameter of less than 100 nm, are all that are required of the material. That’s around one-thousandth the width of a human hair, so it’s not easy but it’s also not impossible.
Researchers at the University of Massachusetts Amherst, led by engineer Xiaomeng Liu, found that this type of material might be used to harness the energy released by tiny water droplets in the humid air.
They have coined the term “generic Air-gen effect” to describe their finding.
According to UMass Amherst engineer Jun Yao, “the air contains an enormous amount of electricity.”
Consider a cloud, which is really just a collection of tiny water droplets floating in the air. We don’t know how to properly capture electricity from lightning, despite the fact that each of those droplets holds a charge and the cloud can produce a lightning bolt under the right conditions. We have developed a miniature artificial cloud that generates consistent and reliable electrical power for us to gather.
You may be remembering Air-gen from when the group worked on an air energy harvester. However, their previous apparatus utilized protein nanowires produced by Geobacter sulfurreducens.
It seems the bacterium wasn’t needed after all.
“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 the air, so long as it has a certain property,” Yao says.
Nanopores are responsible for this quality, and their size is determined by the free mean route of water molecules in moist air. That’s how far a water molecule can travel through air without bumping against another one.
Thin films of materials like cellulose, silk protein, or graphene oxide are used to create the standard Air-gen gadget. Nanopores allow air molecules to enter and pass through the film, but the molecules of water constantly collide with the film’s sides.
These add a charge to the substance, leading to a buildup, and because more water molecules enter the top of the film than the bottom, a charge imbalance develops.
This results in an effect similar to that seen in clouds that generate lightning, wherein higher clouds have an excess of positive charge and lower clouds have an excess of negative charge due to increased collisions between water droplets at the cloud top.
It’s possible that the charge may then be used to power miniature gadgets or saved in a battery.
It’s still in its preliminary phases at the moment. A mobile phone needs a voltage output of about 5 volts, however, the cellulose film the researchers examined had a spontaneous voltage production of 260 millivolts in the ambient environment. However, because the films are so thin, they may be stacked to increase the size of Air-gen devices, expanding their usefulness.
The researchers also note that the gadgets’ versatility in construction materials makes it possible to tailor them to their intended setting.
Yao explains that despite the idea’s seeming simplicity, it has never been discovered previously and thus presents a wealth of new opportunities. It’s possible to picture harvesters constructed from different materials for use in, say, a tropical rainforest and a desert.
Testing the devices in various settings and working to increase their capacity will follow. However, the potential represented by the generic Air-gen effect is exciting.
“This is very exciting,” Liu enthuses. By doing this, we are making it much easier to generate renewable energy from ambient air.
