Goodyear Wants to Power Your Car Using Heat From the Tires

Regenerative braking might have a partner in crime with Goodyear’s regenerative tires.

Photo via Goodyear

We were all taught in middle and high school science classes that friction produces heat. One common example of this is the friction and heat created by car tires moving across pavement. Most of the time, that energy goes to waste, which electric car companies try to minimize in order to keep batteries charged.

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Eliminating the Wasted Energy in Your Car

Your car only uses 15 percent of the energy from its gas, but engineers are working on sucking every last drop from your gasoline. This is the...

Your car only uses 15 percent of the energy from its gas, but engineers are working on sucking every last drop from your gasoline.

This is the second part in an eight-part series on the future of transportation. New articles published every Monday.

If you had to invent an efficient way to move a person from one place to another, you could hardly do worse than the modern automobile. After more than a century of refinement, even the most over-engineered slab of German perfection wastes 85 percent of the energy in the fuel we put into it.

Most of that energy is squandered by the car's beating heart, the internal combustion engine, which alone wastes 62 percent of the energy that enters the gas tank, according to the EPA. Where does that energy go? It's radiated away into the atmosphere as heat.

By comparison, the rest of the average car is relatively efficient. The stereo, air conditioner, and power windows combined eat up only 2.2 percent of the car's energy intake. Ditto air resistance (2.6 percent); friction between the wheels, their bearings and the road (4.2 percent); braking (5.8 percent); and the "driveline," which includes the transmission and all the other parts of the car that transmit the force of the crankshaft to the wheels. Idling uses up the remaining 17 percent of the energy in a car, which explains why hybrid vehicles turn themselves off at stoplights.

That means that of the 130 million joules of chemical energy in the average gallon of gasoline, only 19.5 million are converted into the kind of kinetic energy that matters-forward motion of the car. The rest are literally disappearing into thin air.

Only a century of cheap oil could keep all that low-hanging energy out of the hands of innovators who want to recover as much of that wastage as possible. Now that most of the developed world has finally jumped on the conservation bandwagon, their dreams are becoming a reality.

There are three basic ways to recover wasted energy in a car: regenerative shocks, regenerative braking, and recovery of waste heat from engine exhaust. Other options, like the "wind-energy-capturing device for moving vehicles" described as a tiny wind turbine attached to the top of a truck-are pipe dreams, despite having been issued patents by a U.S. Patent office that apparently doesn't care whether an invention will actually work. (If this did work, pinwheels on big rigs would be the perpetual motion machines that could end our dependence on Mideast oil immediately.)

Regenerative Shock Absorbers:

Zack Anderson, the co-founder of Levant Power, a company tackling regenerative shock absorbers. When a car rolls over a bump, its hydraulic shocks absorb kinetic energy, which is then dissipated as heat. This isn't a big deal if you're driving a Camry, but if you're the world's single largest consumer of liquid fuels and your fleet of Humvees is rolling across the unpaved badlands of Afghanistan, the savings start to add up.

"Depending on the vehicle type and terrain, we're increasing fuel efficiency in the [U.S. military's vehicles] by up to six percent," says Anderson. That's 60 percent of the energy lost through the vehicle's suspension. Theoretically, says Anderson, they could recover 100 percent of the energy wasted by shocks, which would increase fuel efficiency in heavy vehicles on bumpy roads by up to 10 percent.

Installing the same system on a passenger vehicle rolling on smooth terrain would increase its fuel efficiency by only about 2 percent, but if Levant can make its shocks cheaply enough, they could show up on a car near you soon. That's because Anderson and his team have created shocks that are exactly the same dimensions as regular automobile shocks and that function in nearly the same way. "A standard shock is a piston," says Anderson. "When the car's wheels move up and down, that piston forces a thick fluid through small hole, and that causes heat. What we're doing instead is, we're using that piston movement to turn a hydraulic motor that spins an electric generator and that produces electricity."

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