All Vibrations are good vibrations in the world of energy harvesting. Whether it's a road under heavy traffic or commuters pounding the sidewalk pavement, micromovements on any surface can be converted into clean energy by power-scavenging devices fitted with piezoelectric (PE) crystals. These pressure-sensitive materials — normally made of ceramics — give off a small charge when "squeezed, squashed, bent, or slapped," explains Markys Cain, a materials scientist at the British National Physical Laboratory. ("Piezo," by the way, is derived from the Greek for "press" or "squeeze.") So a PE layer slotted beneath a supermarket parking lot could, for example, use the movement of customers' cars to power checkout conveyor belts or pump that free electricity back into the grid. Here's how these sparky substances will be turning vibrations into volts.
Late last year, Haifa-based Innowattech dug up 33 feet of Israel's Highway 4 and inserted PE generators 2 inches below the blacktop. If the gizmos were placed under one lane of a busy half-mile stretch (at an estimated cost of $500,000), the company says the generators could create enough energy to meet the needs of 250 homes.
There's nothing pedestrian about Pavegen Systems' walkway slabs, which generate a steady 2.1 watt hours when positioned in heavy footfall zones. This summer, clusters of energy-absorbing pads will be installed at a major London transport hub to power lighting and signs.
Railway tracks absorb huge amounts of kinetic energy from passing locomotives. Innowattech taps that train strain with customized concrete sleepers loaded with PE generators. The firm is currently testing the kit with Israel Railways and estimates the passage of 300 cars an hour over 1 kilometer of track will provide enough juice for 150 households.
High-energy fan celebrations in the bleachers could soon be charging LED displays and other devices around ballparks. Powerleap, based in Ann Arbor, Michigan, aims to start testing PE floor tiles (a square foot will cost between $50 and $100) in stadiums around the world next year.
The U.S. military uses battery-powered wireless sensors to check chopper rotors and other parts for damage. Vermont-based MicroStrain has created sensors that suck energy from the very vibrations and strains they're designed to monitor.
The rise and fall of your lungs during breathing produces close to 1 watt a minute. Up to 80% of that energy can be captured with nano-size crystals printed onto flexible film developed by Princeton scientists. The biocompatible generators could soon be implanted to recharge pacemaker batteries.
Illustrations by MCKIBILLO