Photos: Power-generating leg brace goes for a walk

Researchers from Simon Fraser University in British Columbia have developed a device worn much like a knee brace that generates electricity from the natural motion of walking.

Here, Max Donelan, assistant professor of kinesiology, watches a demonstration of the Biomechanical Energy Harvester he developed with a team of researchers. The device 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", according to a release from the university.

Wearing a device on each leg, an individual can generate up to five watts of electricity with little additional physical effort, according to the release. Walking quickly, however, generates as much as 13 watts. At that rate, when the energy is stored in a battery, one minute of walking time could provide enough electricity to sustain 30 minutes of talk-time on a mobile phone.

Donelan said: "People are an excellent source of portable power - an average-sized person stores as much energy in fat as a 1,000kg battery. People recharge their 'body batteries' with food and, lucky for us, there is about as much useful energy in a 35g granola bar as in a 3.5kg lithium-ion battery."

Photo credit: Greg Ehlers/Simon Fraser University