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.
Phil
Now, where you can extract energy is where one would normally be trying to slow a vehicle down anyway (deceleration ramps, drive up windows, speed bumps, toll booths, etc.). The idea to generate electricity with the shock absorbers is also a case where you want to dampen (or slow) the car\'s vertical motion... same principle and would work, but don\'t know to what amount of absolute power it would generate on regular roads...
Cheers,
Doc
Therefore, the small devices described here, or an array of such devices could generate power without significantly adding to drag.
I have had someone ask me if he could install a ducted fan on his car or a series of them installed on a trailer towed by his car, could be used to generate electricity which would provide some of the power required to move the car. The problem is that these fans generate drag when the air flows over their blades, which is what causes the blades to rotate, but it also causes the engine to have to work harder to move the vehicle. They\'re trying to create a sort of perpetual motion machine, but that won\'t work, because the drag added is more than the power produced, and this doesn\'t take into account the mechanical losses at each change of state of mechanisms; mostly from friction and transmission losses.