KERS (Kinetic Energy Recovery System) is a system for the recovery of kinetic energy under breaking whose use was allowed by FIA regulations for Formula 1 from 2009 championship.
The energy stored under braking is made available to the pilot, who can decide to reuse it in specific situations – straight stretches, while overtaking other cars or at strategic points of the track – providing a power boost during each lap through a pushbutton or throttle.
According to FIA regulations, KERS has to be an “add-on” system, capable of storing 400 kilojoules at the most and making available a power of 60 kW (about 80 HP) per lap, for a maximum of 6.6 seconds.
Magneti Marelli has developed an electrical solution for KERS.
The device is connected directly to the drive shaft through a motor-generator that, under braking, driven by the same shaft, converts kinetic energy into electrical energy (thanks to the interaction between the fixed components of the stators and the movable components of the rotors). Through the control unit and through shielded wirings, this current recharges lithium ion batteries. Under acceleration, on the other hand, kinetic energy is taken from the batteries when the pilot operates the power boost and, again through the electronic control unit, it is sent to the motor-generator, which rotates in the opposite direction and applies an accelerating force on the drive shaft. The motor-generator can reach up to 40,000 revolutions per minute.
MAGNETI MARELLI TECHNOLOGY
Magneti Marelli has designed, developed and manufactured the following components for the KERS system:
TECHNOLOGICAL CHALLENGE AND SYSTEM PERFORMANCES
When developing KERS, the main technological challenge faced by Magneti Marelli was to concentrate in a small space and low weight a system with extremely high power in proportion, making it suited for an extreme environment in terms of temperatures and vibrations, and combining conflicting technical requirements and features.
Design and construction technologies with extremely high power density (around 20 kW/kg) and compactness with equally high values (the total weight is 4 kg per volume litre) had to be developed. The result is an engine capable of delivering 60 kW and reaching efficiency levels of 95-97%. In terms of cooling, it was possible to make the motor-generator and electronics work up to engine temperature (cooled by the vehicle water circuit, at about 100°).
Another challenge was to be able to fit in a small electronic control unit (less than 2 litre and lighter than 3 kg) both high-power components and a complex multi-processor digital logic, for a system capable of working with high voltages and currents: up to 500 volt and 1000 ampere.
To achieve these results and such a difficult technological compromise, the “system” approach that Magneti Marelli has in its DNA proved to be crucial: it allowed the overall optimisation of the device and a complete integration job between system-vehicle, motor-generator, electronics and batteries.