Here’s an interesting potential source of electricity — people power. Think about it. People move around a lot during the day, whether it’s walking, fidgeting, gesticulating, or doing something more active like bicycling. Even small movements, hooked up to devices that use tiny generators to covert motion into electrical current, can generate considerable amounts of electricity. I’m reminded of this every day on my bike commute, as a generator built into the front hub of my Breezer Uptown 8 bicycle ( powers surprisingly bright front and rear LED lights. I no longer have to worry about batteries dying before I get home, and the slight extra drag created by the generator is imperceptible.

But a bicycle generator hub could be just the beginning. A recent paper in Science magazine describes a small device that turns walking into electricity. It looks like a lightweight leg brace with a gizmo attached near the knee. Bend and straighten the knee, and the device generates up to 5 watts of electricity. Just one minute of walking produces enough electricity to power a cell phone for 10 minutes. The device is the product of nearly a decade of research at British Columbia’s Simon Fraser University and is being developed by a company called Bionic Power ( It has obvious applications in the military, where soldiers would be thrilled with a better alternative to the heavy battery packs needed power all their electronic gear. But think also about the possible uses for keeping Blackberrys or GPS units humming.

And there may be even more exotic devices in the future. In the February 14 issue of Nature, researchers at Georgia Tech report on a nanotechnology system that could turn a shirt into a power source. The idea is to create what looks like a microscopic version of a brush that looks like it might be used to clean a tube. Each brush is made from a strand of Kevlar, with millions of nano wires sticking out from the fiber, like the pins into a pincushion. Put two such bristling fiber strands next to each other and move them around so that the fibers rub together, and presto! The piezoelectric effect, a phenomenon where stress on a material generates electricity, makes power. Practical products are a long way off, of course. But it’s possible to imagine a future where these fibers are used to make cloth for electricity-generating shirts or pants.

Clearly, each of these devices will be able to make only small amounts of power. But if enough people harnessed their everyday movements to produce electricity, they could power their own cell phones, PDAs, GPS units, and other electronic devices instead of plugging them in. The electricity savings for the economy as a whole could add up to a big number.

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