Recent article about KERS, F1 and Torotrak http://www.greencar.com/features/flywheel-batteries-to-power-f1/
Regenerative braking is an integral part of every hybrid electric vehicle. Here, deceleration and braking energy is converted to electrical energy to keep batteries charged. Hydraulic hybrid trucks and buses recoup energy by pressurizing a hydraulic fluid that’s stored in an accumulator, and then use this energy when extra power is needed. There is third type of regenerative braking where recouped energy is stored in a flywheel revved up at high rpms.
This third type of storage, called a Kinetic Energy Recovery System (KERS), will be used starting in the 2009 Formula 1 racing season. The FIA (Fédération Internationale de l'Automobile) will phase in KERS over the next four years to allow, with other changes, reducing engine size and output to make F1 competition more environmentally friendly.
While KERS can only store a limited amount of energy, the system is compact and quite lightweight. KERS is especially effective in applications with lots of acceleration and deceleration, which is the case with F1 racers as they go from corner to corner. The energy stored in a lightweight steel and composite flywheel spinning at over 60,000 rpm can be used to accelerate the vehicle. The FIA defined the amount of energy recovery for the 2009 season as 400 kiloJoules per lap, providing an extra 80 horsepower over a period of 6.67 seconds. Its low weight, about 55 pounds, is also very important in motorsports.
Flybrid Systems in Britain supplies the KERS that uses continuously variable transmission (CVT) technology obtained through its partnership with Torotrak Plc and Xtrac Ltd. Xtrac uses Torotrak’s full-toroidal traction drive technology developed for KERS use in motorsports. Drivers use a power boost button on the steering wheel when they want to use the stored energy for a quick power boost.
A flywheel system offers up to twice the efficiency of a battery storage system. The overall in-out efficiency of 65 to 70 percent compares to 35 to 45 percent for a hybrid battery-electric system. That is because it’s an entirely mechanical system. In a battery system, kinetic energy has to be converted back and forth to electrical and chemical energy, thus the efficiency losses.
While introduced in F1 racing, KERS could be used in other motorsports venues and ultimately in road cars. For example, the British government is funding the Flywheel Hybrid System for Premium Vehicles project as one of 16 innovative low carbon vehicle development projects. Jaguar Cars will lead a consortium made up of Flybrid Systems, Ford Motor Co. Ltd, Prodrive, Ricardo UK Ltd, Torotrak Plc, and Xtrac Ltd. The project will demonstrate the technology in an existing vehicle platform to prove its effectiveness and viability for production use in a premium passenger vehicle as an alternative to other hybrid systems.
Not all F1 teams are using a flywheel based KERS. The BMW Sauber F1 Team is developing an electric KERS brake energy regeneration and storage system that uses a combination electric motor/generator, power electronics, and lithium-ion batteries for energy storage. Unlike the regenerative braking used in most hybrid electric vehicles including several BMW hybrids, the BMW KERS has a much greater power density to meet the needs of racing. Weighing less than 88 pounds, it can provide 60 kilowatts (80-horsepower) of output over about 6.5 seconds of acceleration. BMW says this technology will flow into production car development in the future.