Harvesting energy from vehicle air flow using piezoelectrics

http://www.gizmag.com/harnessing-vehicle-air-flow-energy/13414/

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.

[...] 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.