When I was like 12, I did an interesting experiment: I connected a piezoelectric cigarette lighter to a halogen lamp based voltmeter measuring up to 3000V. The short spark easily raised the voltage above that figure. Of course, the current is very small, but the voltage is high – to the degree of about several tens of thousands volts.
The piezoelectric cigarette lighter has two crystals in it. Hitting them with a mechanical force exerted by your finger and accumulated by a small spring creates electricity by stretching and releasing the crystals.
This principle of creating electricity has been used in devices placed under the asphalt to convert its vibrations into electricity, in Israel, by which engineers hope to harvest the energy from passing vehicles.
Their energetic figures are impressing. The developer Haim Abramovich from the Technion (Israel Institute of Technology in Haifa) says the system can produce up to 400kW from a 1 km long stretched system, on a four-lane highway.
This system is basically recovering energy from the cars’ wheels, produced by their internal combustion engines, but that’s not the point. The main idea is that we can recover these small bits of energy and, if applied on a large scale, can energize many homes in the surrounding towns or villages.