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People Power

March 25, 2008

A knee-mounted device harnesses electrical energy from everyday walking.


Getting a charge out of your walk. I’m Bob Hirshon and this is Science Update.

In the near future, walking may be more than just good exercise: it may also be a useful source of electricity. A team led by kinesiologist Max Donelan of Simon Fraser University in Canada has rigged an orthopedic knee brace with sensors, gears, and a generator. The result is a prototype device that harvests energy from the constant stop-and-go muscular work of an ordinary stride.

MAX DONELAN (Simon Fraser University, Canada):
It has a couple modes, and the first mode, where there’s no additional increase in effort, you can get about five watts of electrical power.

That’s per minute of walking, and it’s enough to give you ten minutes of talk time on a cell phone. Another mode, which adds more effort, generates thirteen watts per minute of walking. Donelan’s team is currently refining the device to charge batteries for military gear, as well as medical devices like robotic limbs. I’m Bob Hirshon for AAAS, the science society.