Regenerative braking is commonly used in hybrids and electric cars to recover energy normally lost as heat during braking.

But that isn't the only potential source of energy in cars that may be going to waste.

Audi has developed a prototype suspension system that uses the motion of shock absorbers to generate electricity as well.

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Called eROT, the system has not been confirmed for production, but offers some interesting possibilities for improving the efficiency of future cars.

The system relies on electromechanical rotary dampers, in place of the hydraulic dampers found in most conventional suspension setups.

It's the job of any suspension system to regulate the vertical up and down motions of a wheel, known as compression and rebound, respectively.

2017 Audi S5 First Drive

2017 Audi S5 First Drive

In the Audi eROT system, those motions are transferred through an arm connected to the wheel to a gear unit.

This converts those movements into a spinning motion, which in turn is used to generate electricity.

Audi claims the system generates as much as 613 watts on very bumpy roads.

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Uneven road surfaces might not be the most pleasant for vehicle occupants, but because they trigger increases suspension movement, they are optimal for generating electricity.

Electricity harvested by eROT could potentially be fed into the battery packs of hybrid or electric cars.

Alternatively, the energy could be used to power accessories and reduce the load on an internal-combustion engine, as in the i-ELOOP regenerative-braking system currently offered by Mazda.

2016 Audi A3 e-tron - First Drive

2016 Audi A3 e-tron - First Drive

In its press release detailing the system, Audi noted that eROT is used in concert with a 48-volt electrical system, which includes a 0.5-kilowatt-hour lithium-ion battery pack.

Several suppliers are promoting 48-volt systems for so-called "mild hybrids," which provide some supplementary electrical power, but are not capable of propelling a car on electricity alone.

MORE: 48-volt mild hybrid systems: what they do, how they change the car

In addition to generating electricity, Audi claims eROT can also adapt more readily to different road surfaces than conventional suspension systems.

That's because the electromechanical rotary dampers' rebound and compression rates can be set independent of each other, according to Audi.

2016 Audi A3 e-tron - First Drive

2016 Audi A3 e-tron - First Drive

The carmaker also says eROT is more compact than conventional suspension systems, freeing up additional space for other uses.

While Audi has released no concrete plans to use eROT on a production model, it does plan to launch a model with a 48-volt electrical system in 2017.

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That model will use a "high-performance mild hybrid drive," Audi says.

The following year, Audi will launch an all-electric SUV based on the e-tron quattro concept from the 2015 Frankfurt Motor Show, and will continue to launch one new hybrid or electric car every year after that.


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