Boots Made for Power Walking

ByPaul Eng

Oct. 12, 2001 -- There are boots for wading, walking, hiking and skiing. But how about boots for power?

SRI International, a research firm in Menlo Park, Calif., is working with the Defense Department to create a shoe that will convert the mechanical energy of walking into electric power to charge up gadgets, batteries and other devices.

At the heart, or rather sole, of the experimental foot-ware is a heel made of a special elastic polymer. A tiny battery positively charges one side of the flexible material and the other negatively. As the material is compressed and released — such as by the foot pressure generated during walking — the distance between the positive and negative sides change, which in turn creates electricity.

According to Ron Pelrine, the director for SRI International's Advanced Transducers Program, the prototype boot generates about half a watt of power — more than enough energy to recharge the boot's built-in battery and a cell phone. But Pelrine hopes that by the end of January the boot's output could be raised to nearly two watts which is enough juice to power several small electronic devices — a cell phone, a handheld computer, and a radio — simultaneously.

And that kind of potential could be reached since the Defense Advanced Research Projects Agency, or DARPA, has funded about $2.6 million to SRI International's research under a project called Energy Harvesting.

The goal DARPA's project is to develop unconventional energy sources to power a future soldier's equipment such as radios and electronic gun sights. By harvesting power generated by walking, soliders of the future won't have carry as many batteries and have more room for other supplies such as ammunition and food.

Smarter Combat Boots, Quieter Generators

Pelrine says that SRI's boots would also provide for even "smarter" foot-ware for the common ground-pounder. "The power can be used for devices on the boot such as navigation aides, electronic functions that will tell you how far you've walked and monitor your health," he said.

What's more, Pelrine says the power-generating polymers could be used in other places outside of the shoe.

For example, a portable gas-powered motor could flex a lightweight polymer instead of cranking a conventional magnet- and metal-based generator. That would make a portable electric generator not only lighter, but quite possibly quieter since there are fewer moving parts.

"These polymers can be used anywhere you need to generate power," says Pelrine.

Pelrine is quick to warn that it will still take quite some time before we see people plugging into their shoes for juice, however. Specific design issues, such as how to pack the polymers and electronics into an easy to manufacture material, still need to be worked out.

Pelrine estimates that the earliest we may see power-generating foot-ware hit the streets would be in two years. And that depends if SRI can receive full funding to move the boots beyond the prototype stage. "This isn't something that we'd have in the next few months," he says.