Piezoelectricity is energy produced from pressure. The energy gets generated when an automobile, a truck or a train passes over a surface in which piezoelectric devices are embedded. Even a sidewalk or dance floor can be outfitted with such devices.
The cigarette lighter in an automobile is a good analogy for how piezoelectric devices work. In the case of the lighter a spring-loaded plunger is depressed producing high voltage to heat the embedded element.
Piezoelectric devices are embedded within existing infrastructure. As a result they can work day or night, in almost any climate and in any weather conditions. The energy these devices generate is in some sense serving to recover the energy expended by the vehicles that drive over them. With no footprint on the land like solar and wind, piezoelectric technology can include data collectors making roads smart to monitor and report on traffic conditions, vehicle type and weight, and vehicle velocity. And wherever piezoelectric devices are embedded they are practically impossible to damage or steal.
Innowattech Energy Harvesting Systems is an Israeli engineering firm that has developed the IPEG (TM), the Innowattech Piezo Electric Generator, a device that deforms from the weight of a person, vehicle, train or aircraft as they pass over. IPEGS can be installed in asphalt, concrete or composite material-surfaced roads. The company is working with the Italian government to install IPEGS in a highway running between Venice and Trieste to operate all road lighting.
How much energy can a device like an IPEG produce? A single kilometer (0.62 miles) of roadway with IPEGs installed can generate 400 kilowatts of energy based on average traffic conditions. The busier the road, the more energy it produces. Heavier vehicles means more energy gets generated.
On a personal level imagine owning a pair of shoes with soles that contain piezoelectric technology to power all of your mobile devices from phones to music players to flashlights with every step you take.