Regenerative brakes are nothing new and capture a lot of wasted energy in hybrid and electric cars, but there’s another energy source automakers could exploit: bumps in the road.
Audi developed an active suspension called eROT that replaces hydraulic shocks with electromechanical ones. Every pothole, every bump, every curve induces kinetic energy in the car, and with the new electromechanical damper system in a 48-volt electrical system, Audi put this energy to use.
To convert kinetic to electrical energy, the shocks use a lever arm that captures the up (compression) and down (rebound) movements of the wheel into spinning motion and transmits it to a 48 volt alternator. It’s then converted into electricity, with an average recuperation output of 100 to 150 watts — as little as 3 watts on a freeway, and up to 613 watts on a rough county road. That’s not enough for your AC, but it could power other accessories and reduce fuel consumption a bit.
For example, the Q7’s supercharged 3.0-liter V6 returns a combined rating of 21 miles per gallon. Apply eROT’s savings, and the Q7’s economy would improve to 22.4 mpg, a 1.4-mpg improvement. That’s not huge, but because math is more dramatic on a more fuel efficient vehicle – taking an A3’s 27-mpg combined rating and adding eROT would drive efficiency up 2.4 mpg.
While it may not seem like much, it’s enough to bring CO2 emissions down slightly. The other advantage is that the mechanism used to support this technology uses much less space and weighs less than regular hydraulic dampers, giving engineers more room to work with for extra features. For instance, it would save space in a vehicle’s luggage area by eliminating the telescopic shock absorbers that would normally be intruding into the cargo space and could also mean lower, sleeker vehicles.
The system uses a set of ohmic resistors to increase resistance (to create a firmer ride) and can vary the amount of current generated based on level of resistance. So, if the driver wants a firmer ride and then drives over a bumpy road, the system will be generating the maximum possible power.
As with any active suspension, it’ll also smooth out the ride by adapting to road surface defects and the driver’s style. With eROT, Audi configures the compression stroke to be comfortably soft without compromising the taut damping of the rebound stroke.
Audi says that initial test results for the eROT technology are promising, thus its use in future Audi production models is certainly plausible. Before it can be commercialized, Audi says the vehicle needs a 48-volt electrical system — luckily, it’s is planning on releasing a hybrid vehicle in 2017 equipped with one, and this pairs with Audi’s vision for mild-hybridization to be enabled on all its vehicles by 2026.