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Power harnessed one step at a time

Engineers call it 'crowd farming.' If it works, you could help power city lights just by taking a stroll.

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In the push to harvest alternative energy, scientists have tapped a number of novel sources: the sun, corn, old cooking oil. But how about the simple act of walking?

For two architecture students at the Massachusetts Institute of Technology in Cambridge, Mass., the sound of footsteps is an echo of energy gone to waste. They figure that the stomp of every footfall gives off enough power to light two 60-watt bulbs for one second.

"Now imagine how many people walk through a train station each morning, or walk down the street in Hong Kong," says James Graham, who, with fellow MIT graduate student Thaddeus Jusczyk, is helping to develop the growing field of "crowd farming."

They devised a special floor of sliding blocks that can turn motion energy (such as from a footstep) into electrical energy. As commuters march across the floor, it would collect tiny flickers of power from each stride and channel that energy.

According to their design – which this summer won a prestigious award from the Holcim Foundation for Sustainable Construction in Zurich, Switzerland – 28,527 footsteps could power a train for one second – 84,162,203 paces could launch a space shuttle.

The problem with their plan: Right now, it only exists on paper. But others have developed real-world examples of plugging into people power. Over the past few years there's been a boom in technology that harnesses piezoelectricity – the science of drawing power from mechanical stress, including motion. While the crowd-farming push has its critics, the discipline is growing, and businesses are signing on. [Editor's note: The original version's definition of piezoelectricity needed clarification.]

"This is a really exciting time because there's been a lot of growth all of a sudden," says Steve Anton, whose review article on recent piezoelectric advances ran in the June issue of the journal Smart Materials and Structures. "For a long time the research was confined to the lab, but a number of real applications have started coming out."


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