The KERS unit designed for the BMW Sauber F1.09 is an effective, higher power density variant of brake energy regeneration technology, and is similar in the way it works to the ActiveHybrid technology developed for BMW standard production vehicles, according to Dr. Klaus Draeger, BMW’s Development Director.

...the power density of the F1 KERS technology is considerably greater than that of the systems currently used in standard production vehicles. We are standing at the threshold between a conventional package of engine and independent transmission and an integrated drive system. The development of KERS will see Formula One take on a pioneering role for series production technologies going forward.

F1 will give a baptism of fire to innovative concepts whose service life and reliability have not yet reached the level required for series production vehicles, and their development will be driven forward at full speed. At BMW we have always used the Formula One project as a technology laboratory for series production. With KERS this approach takes on a whole new dimension.

—Mario Theissen, BMW Motorsport Director

The BMW Sauber F1 team began working with engineers from BMW Forschung und Technik GmbH in mid-2007 on KERS, beginning by investigating the types of hybrid system capable of operating effectively in the extreme conditions of Formula One.

A range of different solutions were put on the table. We analysed electric, mechanical, hydraulic and even pneumatic systems. After several months of research, it was clear that only an electric system would deliver the required energy, while at the same time combining maximum safety and, above all, the lowest possible weight.

—Markus Duesmann, Head of Powertrain

The team spent the ensuing months developing the electric motor, the electric energy storage unit and the KERS control unit. The first KERS prototype was placed onto the test rig in March 2008.

In July, a mechanic received a powerful shock after touching the steering wheel and sidepod of an F1.07 fitted with the KERS prototype. After six weeks of investigation, the team determined that the shock was due to a high-frequency AC voltage between the two contact points, the cause of which was traced back to the KERS control unit and a sporadic capacitive coupling from the high-voltage network to the 12-volt network. The voltage ran through the wiring of the 12-volt network to the steering wheel and through the carbon chassis back to the control unit.

The analysis, in addition to identifying the problem and pointing to solutions, resulted in other recommendations for the development of electric KERS systems. Among the measures arrived at are changes in the design of the control unit to avoid capacitive coupling effects, extended monitoring functions for high frequencies and a conductive connection of the chassis components to avoid any electric potential. The BMW Sauber F1 Team made this safety analysis, complete with suggested measures and recommendations, available to the FIA and the other Formula One teams.

The combination of the return of slicks (treadless tires) with the possible use of KERS technology places particular importance on weight distribution in the design of the new Formula One cars. The switch to slicks means more grip, but also moves the balance of forces further forward. Consequently, said Willy Rampf, the BMW Sauber F1 Team Technical Coordinator, more weight has to be shifted toward the front of the car, and the aerodynamic balance adjusted likewise.

That task is made more challenging be KERS, as the system adds extra weight and the engineers have much less scope for juggling ballast. The KERS elements also need to be packaged in such a ways to as to minimize their negative impact on aerodynamics and at the same time ensure there is sufficient cooling for all the components.

While the energy storage units fitted compactly in the two sidepods are kept within the required temperature band by the flow of air, the KERS control unit, which is fitted in the right-hand sidepod, has an integrated cooling system.

The sidepods are high at the front and do not fall away as sharply to the rear as in previous years. As chimneys or lamellar outlet vents may no longer be used as an escape route for the exhaust air, the whole rear area of the car, including the engine cover, has to increase in volume to enable optimum airflow over this section as well.