The KERS seen and explained by Renault
KERS is the new buzzword in Formula 1. This system is supposed to facilitate overtaking and lead the sport towards a more ecological future. But how does KERS work? Is this new technology truly effective? The Renault team explains...
What is KERS?
« Let’s start with a definition. The KERS (more commonly referred to as the KERS – in English) – Kinetic Energy Recovery System, was authorized by the FIA to encourage the Formula 1 engineering community to develop more environmentally friendly technological solutions in the future. Kinetic energy is related to motion, and its intensity can be seen as the force required to stop this movement. For example, stopping a bicycle, a car, or a train requires the removal of kinetic energy. »
« Generally, kinetic energy is dissipated through brake friction, converting kinetic energy into heat, which slightly contributes to global warming. With KERS, this energy is not lost but stored to be used to propel the car. This storage can be done in a battery (chemical energy), in a high-speed rotating flywheel (mechanical), in an accumulator (hydraulic), and in many other ways. »
« The energy thus stored can be reused to provide additional power to the internal combustion engine. The regulations stipulate that the KERS must not exceed 60kW each time it is activated (approximately 80 horsepower) and must not release more than 400kJ of energy per lap. This equates to a power boost of about 6 seconds per lap. »
Why did Renault choose the battery solution?
« At the beginning of the KERS project, all energy storage solutions were studied. It was difficult to choose between the battery and the mechanical solution using the flywheel rotating in a vacuum. It eventually became clear that the solution offered by the battery system would be more efficient and offer more potential for development in terms of technology transfer for Renault road cars over the next ten years. »
« Renault’s KERS system thus uses lithium-ion batteries from the company SAFT for energy storage. This French company is renowned for its innovations in the field of next-generation batteries. »
What happens next?
« To complete the system, the KERS not only requires energy storage. It also needs technical elements capable of converting different types of energy: kinetic, electrical, and chemical. This conversion is done with the help of an electric motor (MGU: Motor Generator Unit) whose role is to transform the kinetic energy of the car released during braking into electrical energy and vice versa. »
« This type of system weighs about 50kg and takes up a lot of space: two factors that Formula 1 engineers try to avoid. It is therefore absolutely necessary for the MGU to be as lightweight as possible. This is where Magneti Marelli comes in. By working in partnership with Renault, a compact and lightweight system meeting the very specific criteria has been developed. »
« The result is as follows: the MGU is very small and is only active during braking and during the six seconds of acceleration. The rest of the time it is at rest and dissipates the heat generated during its use. The system developed by Renault thus allows for 70% efficiency in the overall process of recovering the heat generated by the car’s rear axle, converting this energy into electricity, storing it in batteries, and then releasing the energy via the powertrain. »
What does KERS mean for the fans?
« The additional 60kW (equivalent to 80 horsepower), with a total release limited to 400kJ per lap, reduce lap time by between 0.2 and 0.3 seconds, as demonstrated by Fernando Alonso and Nelson Piquet at the start of the Malaysian Grand Prix (gaining six and four places respectively). The benefits of using the system at the start are obvious. However, to get the best out of KERS, the system needs to be as compact and lightweight as possible. Otherwise, this advantage can quickly disappear. The exact weight of the device is a well-kept secret, but considering that every additional 10kg, if unnecessary, can cost 0.35 seconds per lap, it’s no surprise that so many chassis have been put on a diet this winter. »
« In reality, a variety of solutions must be considered to achieve the theoretical reduction of 0.2 – 0.3 seconds per lap, such as mass distribution, not only longitudinal but also vertical. It would be easy to lose the efficiency of the KERS if this area was not taken into account. If the optimal configuration of KERS has been found and if the gearbox is properly staged, the additional 60kW can promote overtaking, at least between the cars with the KERS and those not equipped with this system. »
« Of course, the development of the system is still in its early stages. The teams are currently learning to optimize the KERS as a racing tool. The benefits will surely become even more apparent throughout the year. »
According to a statement from the Renault F1 Team
