Simon Fraser redefines power walking

February 11, 2008

Max Donelan, assistant professor of kinesiology and associate member of engineering science at SFU, helped develop the Biomechanical Energy Harvester, a wearable generative breaking device that can produce up to five watts of electricity.

A group of Simon Fraser University researchers has developed a new wearable technology that generates electricity from the natural motion of walking and promises to change the way portable battery-powered devices are re-charged.

The Biomechanical Energy Harvester, which resembles a lightweight orthopedic knee brace, harvests energy from the end of a walker’s step, when the muscles are working to slow the movement of the leg, in much the same way that hybrid-electric cars recycle power from braking.

Wearing a device on each leg, an individual can generate up to five watts of electricity with little additional physical effort. Walking more quickly generates as much as 13 watts of electricity; at that rate, one minute of walking provides enough electricity to sustain 30 minutes of talk time on a mobile phone.

“This technology promises to have significant medical, military and consumer applications,” says lead author Max Donelan, an assistant professor of kinesiology and associate member of engineering science at SFU.

“A fully charged battery pack represents more than just a mere convenience. It allows a soldier to get back home safely. It benefits stroke victims, amputees and others who rely on power-assisted medical devices for mobility. It means a better quality of life for the developing world, where a half-billion children live without easy access to electricity. And of course it is a necessity to anyone in the developed world who has come to rely on portable electronics for work or play.”

Donelan plans to have a working prototype available within 18 months through his spin-off company, Bionic Power Inc.

How it works

The harvester is rigged with a generator, clutch, gears and a real-time control system to selectively engage and disengage power generation. It works in much the same way that regenerative brakes charge batteries in hybrid vehicles. Regenerative brakes collect the kinetic energy that would otherwise be dissipated as heat when the car slows down. Similarly, the Harvester collects the energy typically lost when the muscles of the body slow the knee after swinging the leg forward to take a step.

It also includes a number of built-in mechanical and electrical innovations that condition the raw power generated by walking, and adjust each stride to extract the maximum amount of power with the minimum amount of effort.
www.bionic-power.com