Simple Motion can Charge Devices

Tuesday, March 18, 2014 @ 10:03 AM gHale


It may soon be possible to power mobile devices simply by walking around or rubbing them with the palm of your hand.

It is all about tapping into the energy potential of human motion where people themselves can be the chief power source for the mobile devices that currently rely on the grid to keep up and running.

“Today, coal, natural gas and nuclear power plants all use turbine-engine driven, electromagnetic-induction generators,” said Professor Zhong Lin Wang of Georgia Institute of Technology. “For a hundred years, this has been the only way to convert mechanical energy into electricity.”

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But a couple of years ago, Wang’s team at Georgia Tech was working on a miniature generator based on an energy phenomenon called the piezoelectric effect, which is electricity resulting from pressure. But to their surprise, it produced more power than expected. They investigated what caused the spike and discovered that two polymer surfaces in the device rubbed together, producing a triboelectric effect — essentially static electricity.

By pairing together two sheets made of different materials, researchers were able to create a triboelectric nanogenerator (TENG), Wang said. Of these sheets, one is in charge of donating electrons, where the other accepts them.

The scientists said when these sheets come into contact with one another, electrons flow from one to the other. When they part, a voltage develops between them.

Since they first started working on this project until now, Wang and his team increased the power density output of their generator by a factor of 100,000. The power density output that they currently boost is one of 300 watts per square meter.

This increase in the generator’s output is chiefly due to the use of nanomaterials.

“The amount of charge transferred depends on surface properties,” Wang said. “Making patterns of nanomaterials on the polymer films’ surfaces increases the contact area between the sheets and can make a 1,000-fold difference in the power generated.”

If incorporated into shoe insoles, whistles, foot pedals, floor mats, and even backpacks, this technology can help harvest the energy potential of human motion, and use it to roll out clean and sustainable power.

On another front, if these generators ended up placed onto ocean buoys, the natural movement of waves would become a valuable power source.

The researchers are now working on figuring out how to make this technology commercially available, and hope that it will not be long until human society begins harvesting motion energy in this innovative manner.



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