Max Donelan viewing device

Brace yourself for the latest in battery-charging technology for gadgets. 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 5 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.

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