Tire-integrated triboelectric generator harvests electricity from rolling tire friction; est. up to +10% fuel econ
A group of University of Wisconsin-Madison engineers and a collaborator from China have developed a triboelectric nanogenerator (TENG) that harvests energy from a car’s rolling tire friction. An innovative method of reusing energy, the nanogenerator ultimately could provide automobile manufacturers a new way to squeeze greater efficiency out of their vehicles.
The TENG is a novel energy harvesting device to convert mechanical energy into electricity based on the universally known triboelectric principle—i.e., the generation of an electric charge resulting from the contact or rubbing together of two dissimilar objects. Specifically, the nanogenerator relies on the triboelectric effect to harness energy from the changing electric potential between the pavement and a vehicle’s wheels.
The researchers reported their development in a paper in the journal Nano Energy.
The friction between the tire and the ground consumes about 10 percent of a vehicle’s fuel. That energy is wasted. So if we can convert that energy, it could give us very good improvement in fuel efficiency.—Xudong Wang, corresponding author
The nanogenerator relies on an electrode integrated into a segment of the tire—a single-electrode TENG (S-TENG). When this part of the tire surface comes into contact with the ground, the friction between those two surfaces ultimately produces an electrical charge.
During initial trials, Wang and his colleagues used a toy car with LED lights to demonstrate the concept. They attached an electrode to the wheels of the car, and as it rolled across the ground, the LED lights flashed on and off. The movement of electrons caused by friction was able to generate enough energy to power the lights, supporting the idea that energy lost to friction can actually be collected and reused.
The electric output of the S-TENG-on-wheel monotonically increased with the increase of the moving speed and weight load of the wheel. The maximum instantaneous power was obtained to be 1.79 mW at a load resistance of 10 MΩ, corresponding to the highest energy conversion efficiency of 10.4%. Multiple S-TENGs were implemented to the tires of a toy vehicle and instantaneously powered 6 commercial green light emitting diodes (LEDs) while the vehicle was moving on the ground. This successful demonstration provides a promising solution to scavenge the wasted friction energy from rolling tires, which may improve the fuel efficiency or the cruising ability of electric vehicles.—Mao et al.
Wang estimates about a 10% increase in the average vehicle’s gas mileage given 50% friction energy conversion efficiency.
Yanchao Mao, Dalong Geng, Erjun Liang, Xudong Wang (2015) “Single-electrode triboelectric nanogenerator for scavenging friction energy from rolling tires,” Nano Energy, Volume 15, Pages 227-234, doi: 10.1016/j.nanoen.2015.04.026