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.