Previously, we’ve looked at technology to generate electricity from roads embedded with piezoelectric crystals that produce electricity when squeezed. Now a group of researchers is looking to shift the technology from the road to the vehicles themselves and use piezoelectrics placed on the vehicles to convert their kinetic energy into electricity.

About a half-inch by one inch, these piezoelectric devices might be mounted on the roof or tail of a car or on an airplane fuselage where they would vibrate inside a flow, producing an output voltage. Although the power generated would not be enough to replace that supplied by the combustion engines, it could be enough to run some systems, such as batteries that would be used to charge control panels and other small electronic devices such as mobile phones.

The group of researchers from the City College of New York (CCNY) led by Prof Yiannis Andreopoulos, is currently attempting to optimize these devices by modeling the physical forces to which they are subjected in different air flows - on the roof of a car, for instance, or on the back of a truck.

When the device is placed in the wake of a cylinder - such as on the back of a truck - the flow of air will cause the devices to vibrate in resonance, says Andreopoulos. On the roof of a car, they will shake in a much more unsteady flow known as a turbulent boundary layer. Andreopoulos and his colleagues have conducted wind tunnel tests showing how the devices work in both situations.

"These devices open the possibility to continuously scavenge otherwise wasted energy from the environment," says Andreopoulos.