Tire-integrated triboelectric generator harvests electricity from rolling tire friction; est. up to +10% fuel econ
30 June 2015
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.
Resources
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
Sorry, basic thermodynamics says this can only reduce the overall vehicle efficiency, and the tires additional energy to power the system will be more than they harvest.
So this article is misleading. TPMS only needs a tiny battery. However it could be useful to power a pump in a tire.
Posted by: GdB | 30 June 2015 at 07:21 AM
GdB, I always wonder how "scientist" can ignore the basic laws of thermodynamics and essentially chase perpetual motion???
If they want to increase fuel efficiency with respect to tires, the only way to do it is use low rolling resistance tire which reduce the friction loss in the first place. We go through this same discussion EVERY TIME someone comes up with this theme. Sigh.
Posted by: DaveD | 30 June 2015 at 08:34 AM
Goodyear has its own idea for energy generating tires; http://www.alternative-energy-news.info/goodyear-electric-tire-concept/
The Goodyear idea would convert heat to electricity: Tires, and the pavement they roll on, are dark in colour and are sitting in the sun all day, this generates heat even when the car's not moving, but the real heat generation kicks in when the car is moving, from road/tire friction and sidewall flex.
Posted by: ai_vin | 30 June 2015 at 11:22 PM
@Ai-Vin
Funny- when I read this article, my thought went immediately to "why aren't they just capturing the tire heat?" Not only would that recoup the losses generated by friction, but one would also capture the heat energy imparted to the black roads by the sun.
As for capturing electricity from the friction- I would suggest that unlike some other cockamamie ideas: "put a windmill on the top of your car to capture high speed wind as you drive!" This one may have some (slight) promise-
Unless I'm missing something, no thermodynamics laws appear to have been broken here- As long as this process doesn't increase friction, then it's simply capturing what would otherwise be lost (similar to regenerative braking)
Posted by: Christopher Miles | 05 July 2015 at 01:30 PM
Capturing both heat and electricity from friction could be possible?
Posted by: HarveyD | 06 July 2015 at 08:16 AM
Actually Chris putting a windmill on top of a car maybe a cockamamie idea, but it does work.
http://www.wired.com/2012/07/wind-powered-car-upwind/
https://en.wikipedia.org/wiki/Blackbird_(land_yacht)
Going against the wind with a windmill even works in the water where you'd think the greater friction would do the idea in; http://www.treehugger.com/renewable-energy/windmill-sailboat-sailing-against-the-wind.html
Posted by: ai_vin | 07 July 2015 at 01:58 PM
In the not too distant future, enough wasted energy and solar energy will be captured to run an ultra light e-car at the legal speed limit during 8 hrs/day in sunny places.
A few years later, similar vehicles with 50+% solar cells will capture enough solar energy to run the car an average of 40 some miles per day and supply part of the energy needed by the owner's home (in very sunny places). Of course, the home roof solar units (2.5 to 5.0 kWh) together will home storage units (10 to 30 kWh)will help to supply the rest.
Posted by: HarveyD | 30 July 2015 at 06:25 PM