Generate Electricity by Walking

What if we could generate electricity just by walking? Kohei Hayamizu, a Japanese engineer, has been working on this idea beginning with a technology system he developed in graduate school. The system makes use of piezoelectricity, “a property certain materials have to generate an electric current when they are squeezed or pressed.”

His first experiment took place in Japan’s Shibuya train crossing last month in which he converted one square meter of the ground into an electricity generator. Each time a person walks over the area, electricity is generated. Over 20 days, with 900,000 people passing through Shibuya each day, he was able to generate enough energy to power 1,422 televisions for one hour.

Hayamizu thinks that similar systems could be installed on a wide range of scales, from small systems embedded on mobile phones, to huge systems installed on highways that would harness the electricity generated by the movement of cars and big trucks.

A quick Google search on this topic brought up some other related projects. A post at Inhabitat from June 2008 describes a proposal by David Webb to do something similar on the stairs of the Spinnaker Tower viewing platform in Portsmouth, UK.


Image of Spinnaker Tower

His hope is to install miniature “heel-strike” generators underneath the stairs that would capture the power generated by a person as they walk down the tower. His ultimate goal is to install them in every rail station, shopping center and even in your shoes!

According to Webb, if these generators were to be installed at the Victoria Underground Station in central London, the power generated by the 34,000 people moving around would be able to power approximately 6,500 lightbulbs. The technology also has application beyond the small steps. Plans are afoot to look into installing these devices in the tower itself, to harness energy from the swaying movement of the building!

An article at Physics World from September 2005 describes how “scientists in the US have invented a back-pack that converts the up and down motion of walking into electricity. The device can generate 7.4 watts and could be used by field scientists, aid workers and soldiers to power mobile phones, GPS instruments and other devices without having to carry heavy replacement batteries.”

Image of Lawrence Rome’s “Suspended-load” backpack

Another natural fit for this technology would be to have your shoes generate energy as you walk (at least enough to power your own devices – mobile phone, camera, etc). As early as 2000, John Sarich developed a prototype that did just that. At the time the idea had “interest from the military, from the medical community, and from retailers…” but he still needed financing.

More recently in October 2008, Telecoms giant NTT announced it was developing shoes that generate electricity as you walk.

Image of prototype

The shoes have a small generator attached to water-filled soles. Each step puts pressure on the soles, causing the water to spin a small turbine and generate power, NTT said.

The futuristic shoes currently generate 1.2 watts of electricity, “a level sufficient to run an iPod mobile music player forever, as long as the wearer keeps walking,” said spokesman Hideomi Tenma.

“The company is trying to improve the power-generating capacity to 3 watts, which is the amount of electricity to power a mobile phone,” he said.

“The shoes do not have a power-storage function, but you would be able to charge a mobile phone automatically or talk on it forever as long as you connect the phone to your shoes and just keep walking.”

NTT hopes to put the generator into actual products as early as 2010.

I’ll be first in line to get those shoes when they hit the market. My hope is that these technologies will continue to be developed and adopted, but with more urgency and support, on both a personal/consumer level and a global urban scale. In the era of sustainable energy, harnessing electricity through piezoelectricity and kinetics seems to be one viable way to design a more energy-efficient and sustainable future.

Incidentally, I recommend browsing the OurWorld 2.0 website for more issues, news and ideas about climate, oil and food in our collective future.

[Credit: Thanks to KyNam Doan for the initial tip on Hayamizu's project at Shibuya.]