September 11, 2005


Power walking: Scientists in the US have invented a back-pack that converts the up and down motion of walking into electricity. The device can generate 7.4 watts and could be used by field scientists, aid workers and soldiers to power mobile phones, GPS instruments and other devices without having to carry heavy replacement batteries (Belle Dumé, 9/09/05, PhysicsWeb)

"We have for the first time generated significant levels of electricity from normal human movement," says Lawrence Rome of the University of Pennsylvania and the Marine Biological Laboratory in Massachusetts. Previous attempts to generate electricity from walking relied on devices built into shoes but this only produced about 20 milliwatts of power. Although high forces are exerted when the shoe touches the ground, little or no mechanical work - which is given by the product of force and distance - is done because of the short distances involved.

To overcome this problem, Rome and colleagues exploit the up and down movement of the hips that occurs during walking, which can be as high as 5--7 centimetres. "If you are carrying a load in the back-pack, it has to go up and down the same vertical distance on each step as your hip," explains Rome. The team calculated that it takes considerable mechanical work - about 18 Joules per step - to lift a backpack weighing 36 kilograms through a distance of 5 centimetres. This mechanical work can then be converted into electricity.

The new back-pack is based on a rigid-frame pack similar to those used by hikers.

Posted by Orrin Judd at September 11, 2005 8:54 PM

Uh oh, haven't these guys seen The Matrix?

Posted by: Buttercup at September 11, 2005 11:57 PM

And pimps can get 10 watts.

Looks like this will revolutionize the way "normal" people walk.

Posted by: Barry Meislin at September 12, 2005 2:17 AM

Australia could round up all of the kangaroos, fit them with these backpacks, and make a killing off of this invention.

Posted by: AllenS at September 12, 2005 6:23 AM
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