Green Wombat

  Sydney Harbour Bridge 
  Originally uploaded by theFijian.

Here’s a potential source of electricity to help Wal-Mart (WMT) achieve its goal of using 100 percent renewable energy in its stores: its customers. Each step a person takes produces 64 watts of dissipated energy and scientists at Australia’s Commonwealth Scientific and Industrial Research Organisation are developing technology to “harvest” vibrational energy and feed it to the power grid or store it in batteries. For instance, CSIRO scientist Sam Behrens estimates that car and train traffic over the Sydney Harbour Bridge generates 6.6 megawatts of vibrational energy. “We could get enough power for 200 homes if we could capture just 10 percent of that energy,” Behrens told me during a visit this week to CSIRO’s Energy Centre in Newcastle. Transducers could be built into the bridge or attached to the exterior of skyscrapers to capture energy. Behrens has made a working model of how the technology works in a hallway at the Energy Centre. A strip of piezoelectric ceramic material has been laid under the floor. When I walk over that patch of floor, the energy from my feet is captured by the piezo, causing a needle to jump on a meter attached to the wall. Behrens also has coated a metal strip with piezoelectric material and when you move the strip the vibrational energy produced powers a small light. This is all early stage research and the key will be reducing the cost of materials like piezoelectric materials and developing the technology to connect vibrational energy to the power grid or store it. Behrens sees potential uses of vibration harvesting in everything from powering heavily trafficked places like airports and train stations to replacing batteries in mobile phones and laptops.