In an electric vehicle the recuperation of energy plays an important role in extending your driving distance by adding energy traditionally lost, back into the batteries.
Currently the recovery of energy is performed under braking and when slowing down. This process is known as regen.
The German powerhouse Audi is working on a prototype suspension system named “eROT,” in which electromechanical rotary dampers replace the hydraulic dampers used today which delivers a new source of energy recuperation.
The principle behind eROT is explained by Dr.-Ing. Stefan Knirsch, Board Member for Technical Development at AUDI AG:
“Every pothole, every bump, every curve induces kinetic energy in the car. Today’s dampers absorb this energy, which is lost in the form of heat.
With the new electromechanical damper system in the 48-volt electrical system, we put this energy to use. It also presents us and our customers with entirely new possibilities for adjusting the suspension.”
The eROT system can convert the kinetic energy during compression and rebound into electricity. To do this, a lever arm absorbs the motion of the wheel carrier. The lever arm transmits this force via a series of gears to an electric motor, which converts it into electricity.
The recuperation output is 100 to 150 watts on average during testing on German roads – from 3 watts on a freshly paved freeway to 613 watts on a rough secondary road. Under customer driving conditions, this corresponds to a CO2 savings of up to three grams per kilometer (4.8 g/mi).
The new eROT technology is based on a high-output 48-volt electrical system. As currently configured, its lithium-ion battery offers an energy capacity of 0.5 kilowatt hours and peak output of 13 kilowatts. A DC converter connects the 48-volt electrical subsystem to the 12-volt primary electrical system, which includes a high-efficiency, enhanced output generator.
Initial test results for the eROT technology are promising, thus its use in future Audi production models is certainly plausible. A prerequisite for this is the 48-volt electrical system, which is a central component of Audi’s electrification strategy.
In the next version planned for 2017, the 48-volt system will serve as the primary electrical system in an upcoming new Audi model and feed a high-performance mild hybrid drive.
Scaled up, this technology could work in parallel with the regenerative braking EV owners know and love.
An additional benefit are the horizontally arranged electric motors in the rear axle area that replace the upright telescopic shock absorbers, this will allow for additional space in the luggage compartment.