Wall walking

A new kind of power walking

Scientists are constantly searching for new and clever ways to make electricity. Earlier this year, for example, Cosmos reported on a new device powered by a microbe that, the US creators say, can generate it from moisture in the air.

Others are working on clothes that can produce electricity, offering the enticing promise of plugging your phone into your jacket for a battery top-up.

Now researchers from China’s Beijing Institute of Nanoenergy and Nanosystems have developed a “tiny wind turbine” they say can scavenge energy while people walk and move their arms. And their vision is that rather than plugging in your phone, it could be added to the phone itself.

Luckily, it doesn’t involve strapping a windmill under your arm. Instead, two plastic strips in a tube flutter or clap together when there is airflow. As they separate, each becomes electrically charged thanks to the triboelectric effect, which can then be captured and stored.

The effect is basically similar to rubbing a balloon to your hair, or a pen on your sleeve. As the objects are separated, the electric charges either attract (like making your hair stand on end) or repel dissimilar or similarly charged objects, respectively. Those electric charges can be used as an energy source, the researchers suggest.

According to their results, which are published in the journal Cell Reports Physical Science, the effect can be created with minimal breeze: as little as 1.6 metres / second, or the same as someone’s arm swinging as they walk. It worked best with a wind speed of 4–8 metres / second, when the plastic strips would flutter in sync.

“You can collect all the breeze in your everyday life,” says Ya Yang, who oversaw the research. “We once placed our nanogenerator on a person’s arm, and a swinging arm’s airflow was enough to generate power.”

Already the device has a higher efficiency than other wind-scavenging approaches, say the researchers. They released a video (below) of the device powering 100 LED lights, albeit flickering on and off.

Credit: Chen, Ma and Ren et al./Cell Reports Physical Science

Not only does the device allow scavenging of wind energy that would otherwise not be exploited, the team says it can be made simply and cheaply using low-cost materials.

“Unlike wind turbines that use coils and magnets, where the costs are fixed, we can pick and choose low-cost materials for our device,” says Yang.

“We can place these devices where traditional wind turbines can’t reach. We can put it in the mountains or on the top of buildings for sustainable energy. Our device can also be safely applied to nature reserves or cities because it doesn’t have the rotating structures.”

Their next steps are to make the nanogenerator both smaller and larger.

They hope to shrink the device to make it compact and efficient enough that it can be added to existing devices. Yang says he sees a future where the generator can attach and provide sustainable power to mobile phones.

However, the team also want to scale it up and make it more powerful: potentially equal in output to traditional wind turbines.

“Our intention isn’t to replace existing wind-power-generation technology. Our goal is to solve the issues that the traditional wind turbines can’t solve,” Yang says.

The Royal Institution of Australia has an Education resource based on this article. You can access it here.

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