The previous article on the subject of KERS was a retrospective look at the hybrid system in the Panoz Q9. In seeking to bring the emerging technology of regenerative braking to racing, Don Panoz was years ahead of the game.
There are now very few large car-makers who don't have a serious hybrid development programme, and a growing number of them feel the technology is mature enough to release series production models - notably Honda with the Insight and the Civic Hybrid, and Toyota with its popular Prius model. The seriousness with which hybrid systems are seen in motorsport is evident through the involvement not only of Formula One, whose rules are very much based around a more efficient powertrain from 2013, but also in sportscar racing where Porsche has had recent success with a hybrid.
Zytek's engineering manager Ian Lovett has been involved in the development of its hybrid systems since the time of the Panoz Q9 project, and I asked him what the main developments have been over the past decade in sportscar racing hybrid systems.
In terms of analysis, Lovett explained, "An awful lot of electromagnetic FEA work goes into the lamination, winding and magnet design, and this is where the gains and thermal performance come from." In terms of providing a low-mass system, he said, "It's down to attention to detail to create the most efficient structural and thermal paths to support the loads and cooling requirements."
Lovett provided some figures for the performance of Zytek's three sportscar KERS systems spanning the Q9 era to the present day:
Q9 is the system raced by Panoz in 1998
Q10 is the system raced by Corsa in the American Le Mans Series in 2009
ZPH is Zytek's current system, now being tested.
A measure of Zytek's progress, in terms not only of performance but also removing mass from the system over the past 12 years, is to measure the power density of the motor. In 1998, the Q9 motor had a 'power density' (output divided by mass) of 3.57 kW/kg, and in 2010 the ZPH system has a corresponding figure of 6.47 kW/kg.
Looking at the Q10, this appears to be a step backwards at 1.74kW/kg, but company owner Bill Gibson said in 2008, "The whole idea of the Q10 is to increase our rate of development of hybrid drivetrains for roadcar use", and indeed this system was closer to the level of technology found in a road-going system than something developed especially for racing.
A comparison of the battery technology is also illuminating. The Q9 battery is almost 100 kg heavier than the ZPH item, while providing only an extra 20 kW of power. The energy density of the Q9 battery is 0.09 MJ/kg, and this rose with the Q10 to 0.118, an increase of 31%. For ZPH, the figure is 0.129, representing a 43% improvement.
The power density figures are more impressive, with the Q10 having a 33% improvement compared with the Q9 (0.816 kW/kg versus 0.615 kW/kg). The ZPH battery, however, has a power density 272% greater than the Q9.
The combination of improved power and energy density means the effectiveness of the batteries is much greater. At any given time, the state of battery technology seems to be such that power density must be traded off against energy density, but as the technology gets better, both can be improved simultaneously.
Fig. 1 - The Ginetta Zytek car seen here carried the Zytek Q10 KERS system. It was the first hybrid LMP car to take a podium position. Eleven years earlier, the Q9 was the first hybrid LM GT1 car to take a podium
Witten by Wayne Ward