One of our sibling blogs, Carectomy.com, just went into some detail discussing a new walker-powered backpack. The straps of the pack are made of a special material that can harness static electricity generated from the energy of walking.
My first thought is that the energy from this action would be negligable in all situations, but Josh at Carectomy points out
A soldier carrying a 100-pound load and walking at 2-3 miles per hour would generate 45.6 milliwatts of power. To put this into context, an LED headlamp consumes about 38mW, an iPod nano 46mW, and a Motorola Razr cell phone 9mW in standby mode and 360mW while talking.
That's pretty impressive, actually. The only material necessary to generate the power are the backpack's straps, which are made from polyvinylidene fluoride (PVDF), and possibly an onboard battery. Of course, the technology is a while away, but maybe someday we'll have whole wardrobes made of PVDF and we'll shuffle our feet on the carpet to keep our cell phones juiced up.