KERS - The secret success story of 2011

Amid the attention attracted this year by both DRS and the performance characteristics of the Pirelli tyres, the return of KERS has been somewhat swamped in the public eye. Yet there’s a firm case to suggest that it, too, has played its own crucial role in enabling the significant increase in overtaking for 2011, with the system being variously used to boost drivers into the ‘DRS zone’ (i.e. less than one second behind the car in front), during the overtaking manoeuvre itself, or even to defend against a car behind with DRS in operation. While no hard data exists on this point, anecdotal evidence suggests KERS plays a role in nearly every overtaking manoeuvre for cars equipped with the system - as well as providing a valuable area of cutting-edge research into electronics and battery technology; in fact, exactly what the philosophy of Formula One has always been about.

How does the Mercedes-Benz KERS work?

The Mercedes-Benz KERS (Kinetic Energy Recovery System) has been developed by Mercedes-Benz HighPerformanceEngines in Brixworth, UK with the support of Mercedes-Benz R&D in Sindelfingen, Germany - a process that also resulted in significant knowledge transfer to series production of hybrid technology. The KERS is made up of the Motor Generator Unit (MGU), the Power Electronics (PE) and a number of batteries that make up the Energy Storage System (ESS). When harvesting power that would otherwise be dissipated as heat through the braking system, the MGU works as a generator, providing three-phase electricity to the PE. This converts the electricity to DC voltage, and stores the energy in the battery. The process works in reverse when the driver requests boost, with the generator unit becoming a motor to supplement the engine power. The processes of harvesting and boosting are both approximately 80% efficient.

How large is the Mercedes-Benz KERS?

The motor in the MGU is approximately ten times smaller than commercial automotive units, while the battery is around eight times smaller than those commercially available. Overall, there are approximately 3,500 parts in a single KERS! It is a true example of cutting-edge engineering.

What is the lap time benefit of KERS at Monza?

The lap time gain from full use of KERS is over 0.4s at Monza. This compares to a lowest value so far this season of approximately 0.3s per lap in Hungary.

Why is Monza such a potent circuit for KERS usage?

The best-case scenario for KERS boosting is relatively slow corners followed by very long straights - exactly what Monza features plenty of. There are four times in the lap (out of Turns 2, 7, 10 and 11) when the car accelerates from relatively low speed to near terminal velocity, and this means that there is a relatively large lap-time benefit from boosting out of any of these four corners. Typical KERS deployment in Monza would see four boosts per lap, which are delivered to the wheels 20ms after the button is pressed.

As well as high speeds, Monza features heavy braking. Does that make it a good circuit for harvesting energy?

The cars spend over 12% of the lap (more than 10 seconds) on the brakes in Monza, with the braking event for Turn 1 seeing them shed around 265kph. However, Monza is actually the most marginal circuit of the year for KERS harvesting, owing to the low number of braking events during the lap: just six in total (Turns 1, 4, 6, 7, 8 and 11).