Photo : - Flybrid Systems 2010

Among the techniques for recovering energy accepted by the ACO, the flywheel is preferred. Porsche has tested this season on some ILMC events (outside classification) and the Hope PoleVision will use it in LM P1 next year.

Similar in appearance, the systems used by Porsche (developed by Williams F1) and Hope PoleVision differ widely in their operation. In both cases, the energy recovered during braking of the car is stored by a carbon disc launched at 60 000 rpm, then returned to the acceleration. This technology is not new, it is already used in the field of transport. But if weight is not an insurmountable problem for a tram or bus, it is for a race car. This handicap is now solved by the use of lightweight materials like carbon fiber.

The Porsche 997 GT3 R Hybrid, two electric motors are placed on the front wheels, a third is connected to the flywheel. These engines operate alternately with receivers and power generators (see article here).

In principle, the solution chosen by Hope PoleVision is much simpler (see article here). The flywheel is directly coupled to the transmission, as an extension of the engine. Developed by Flybrid, this concentration of technology weighs only 25 pounds. It presents an excellent performance, only limited by the capabilities of the continuously variable transmission that provides an interface between the flywheel and the gearbox.

Faced with this compact and lightweight, the solution used by Porsche may seem less attractive. This overlooks the fact that the use of electric motors - coupled to the front - will receive a temporary drive. Advantage in weight or motor function? The 24 Hours of Le Mans offer a unique opportunity to compare these different ideas.

For completeness, it should be noted that the method used by Porsche is not admissible in the state. Regulation 2011 states that the use of an energy recovery system should not aim to seek increased power but reduced fuel consumption. Moreover, the device must be controlled through the accelerator pedal and not through a button as it does on the 997 GT3 R Hybrid. Finally, only the LM P1 prototypes can benefit from such technologies, not the GT.

Julien Hergault

Illustration: The Flywheel of Flybrid system will equip the LM P1 prototype Oreca Team Hope PoleVision next year: the flywheel (foreground) and the continuously variable transmission.