Posted by tourdemars to Technology at July 25, 2008 07:34 AM

Engineers who design wearable devices that harvest human energy for power face a daunting dilemma: how do you collect a significant amount of power without making the user expend a lot of extra effort? Gadgets like hand-crank generators and windup radios require manual work from a user, and existing shoe-mounted generators produce less than one watt of power. A team of engineers has developed a modified knee brace that captures energy that would otherwise have been lost while the wearer walks. The generator produces about five watts--enough to power 10 cell phones simultaneously.