Wildly popular outside the United States, Formula One racing is a form of motorsport known for its yearly hot-topics and innovations. Its governing body, the Federation Internationale de l’Automobile (FIA), imposes ever more stringent technical regulations on each car, including its engine, aerodynamic package, dimensions, and specifications for nearly every component used by the constructors for each year. It is no small wonder, then, that given the intensely competitive nature of Formula One racing and the enormous budgets allotted to Formula One constructors, the sport is responsible for some of the most advanced and high-pressure research and development in the world outside of the military sector. In 2009, this development stemmed in a new direction – regenerative braking.
For the 2009 season, the FIA allowed constructors to use a technology called the Kinetic Energy Recovery System (KERS) as one of several measures to increase the frequency of overtakes and thus enhance the intensity of the sport. The development of this technology also placed the sport in a stance of greater environmental responsibility, as the hybrid technology pioneered in Formula 1 would facilitate the development of more efficient regenerative braking systems in the automotive industry . The maximum performance of KERS systems was strictly restricted by the FIA to a boost of 60kW, with no more than 300kJ on board at any time . Aware of the potential of this technology, teams in the 2009 season contributed impressive development in the technology of regenerative brake systems. The KERS systems developed for 2009 were able to provide up to seven seconds of boost per lap – a significant on-track advantage and a promising leap forward for the hybrid technology.
The idea of harnessing kinetic energy released through braking has been around for over a century. The principle is easy to understand – the kinetic energy of a moving vehicle is converted to heat energy by friction. This heat energy is usually dissipated from the brake rotors and pads and essentially wasted. KERS technology stores this kinetic energy mechanically, using a flywheel, or chemically, using a battery or supercapacitor. However alien this technology may seem, it is already being used in Toyota’s Hybrid Synergy Drive, which stores energy in the batteries of its hybrid cars upon deceleration . KERS in Formula 1 goes a step further, increasing the efficiency of such a system by using a battery optimized for fast storage and retrieval or a lightweight flywheel.
The first implementation of this technology was developed by an engineer named Jon Hilton, who heard the president of the FIA, Max Mosley, announce that Formula One would pursue regenerative brake systems at the British Grand Prix in 2006. Hilton and his design partner, Doug Cross, formed Flybrid Systems LLC in 2007. With funding directly from the partners’ pockets, Hilton and Cross were able to fully manufacture a mechanical KERS system in just 12 months .
The Flybrid system consists of a flywheel connected to the transmission of the car via a continuously variable transmission (CVT) supplied by Torotrak. When braking, the gear ratio is changed so as to speed up the flywheel as the car decelerates. In order to release this energy, the gear ratio is then changed to slow the flywheel and transfer that additional power to the transmission. On paper, this process is extremely simple; however, when spinning a 5 kilogram flywheel at 65,000 rpm, friction and heat become major obstacles. The since-patented F1 Flybrid system had the chamber housing the flywheel in a near-perfect vacuum at a pressure of 1 x 10-7 bar and used ceramic bearings to minimize friction .
Even in a hermetically-sealed vacuum environment, it is difficult to imagine that a flywheel could spin indefinitely and have any meaningful kinetic energy left over after a few turns. In the Flybrid system, however, friction was minimized to the degree that over the course of a full minute, the losses in the rotational speed of the flywheel equate to roughly 2%. Given that the 95th percentile stop time for an average car is 55 seconds, the losses in power are minimal. The simplicity of the Flybrid system, in addition to its efficiency in conserving energy in a mechanical state, allows the Flybrid KERS to have its extraordinary performance at the cost of only 25 kilograms .Like Flybrid, competitor companies Torotrak and Xtrac are also developing mechanical CVT/Flywheel-based KERS devices for use in Formula One and beyond.
Electro-chemical means of kinetic energy storage were meanwhile explored by Zytec – the company which developed the McLaren F1 KERS device . McLaren F1’s KERS device was rumored to be most advanced in the 2009 Formula One season, and though Zytec’s contract with McLaren was revealed, the details of the system are largely unknown . Another team, Renault F1, also used a similar KERS system made jointly by automotive giant Magneti Morelli and SAFT, a cutting-edge French battery solution company. It features an electric motor-generator unit (MGU) coupled with a lithium-ion battery and boasts round-trip efficiency of up to 70%, which is very impressive considering the inherent conversion from mechanical to electrical to chemical energy and back . While creating its KERS device, the Williams Formula 1 team actually purchased a company called Automotive Hybrid Power Limited, now known as Williams Hybrid Power, which is also investigating means of electrical energy storage for consumer automobiles, city transportation, and rapid transit systems [10, 11].
Currently, Flybrid is collaborating with Magneti Morelli and it has already produced a 27-kilogram electric KERS device for the automotive industry, though its original mechanical KERS device is more developed and is expected to be sold in volume in 2013. The original Flybrid KERS device promises fuel savings and CO2 reductions of up to 30% while maintaining a design-life of 250000 miles . The benefits of such systems for consumer automobiles would be enormous, yielding increases in fuel economy of ten miles per gallon or more, and could be easily implemented.
For the trucking industry, the benefits of regenerative braking are even more pronounced, and especially impactful in the United States, where trucking accounts for roughly 70% of total freight tonnage per year. In 2008, the trucking industry generated nearly 750 billion dollars in revenue while wasting as much as 170 billion dollars consuming 55.1 billion gallons of fuel . KERS technology has the potential to reduce that number by 30%, leading to a dramatic decrease in the cost of living for average Americans and an increase in revenue for the United States economy.
Aware of the global potential of regenerative braking, FIA has determined to take advantage of the competition in Formula One to pursue even more functional solutions for the consumer automotive market. Former president of the FIA, Max Mosley, states:
“Formula One would benefit from systems with more capacity than the present, (for example maxima of: 2MJ stored, 150KW in, 100KW out) but still very small and very light, as is essential in Formula One,” explained Mosley. “These figures are theoretically possible with mechanical devices, but not feasible in the foreseeable future using batteries and/or capacitors .
Expanding on these small and light systems will depend on an initiative by the automotive industry to implement KERS technology, but given the stance of the FIA, the technology is sure to raise some eyebrows in the upcoming years. As competition amongst the F1 constructors returns to KERS in 2011, we may expect to see even greater development in regenerative brake technology in the near future.
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Andrey Kossev is a student at Georgia Tech.