Energy harvesting from road bumps could save 0.7l/100km, claims Audi

August 16, 2016 // By Nick Flaherty
Car maker Audi's (Ingolstadt, Germany) move to a 48V power system is allowing an innovative way of capturing energy from a vehicle's suspension

Audi's eROT prototype uses electromechanical rotary dampers instead of the current hydraulic dampers to recharge a battery.

The eROT actively controlled suspension adapts to irregularities in the road surface and the driver’s driving style and feeds a high-output 48V electrical system with a 0.5kWh lithium-ion battery that produces a 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. 

A lever absorbs the motion of the wheel carrier and transmits this force via a series of gears to an electric motor, which converts it into electricity. This generates 100 to 150 watts on average during testing on German roads – from 3 W on a freshly paved motorway to 613 W on a rough secondary road. The technology needs a 48V power system which is the primary electrical system in a new high-performance mild hybrid drive in an Audi model in 2017. This will offer potential fuel savings of up to 0.7 litres per 100 kilometers.

The damper can also be software controlled to configure the compression stroke to be comfortably soft without compromising the taut damping of the rebound stroke. Another advantage of the new damper system is its geometry. The horizontally arranged electric motors in the rear axle area replace the upright telescopic shock absorbers, which allows for additional space in the luggage compartment.

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