Kinetic Energy Recovery Systems (KERS) are automotive systems whereby the kinetic energy of a moving vehicle is recovered under braking and stored in a reservoir (for example a flywheel or a battery) for later use under acceleration.
Kinetic Energy Recovery Systems (KERS) were used for the motor sport Formula One's 2009 season, and are under development for road vehicles. KERS was abandoned for the 2010 Formula One season, but re-introduced for the 2011 season. As of the 2011 season, 9 teams are using KERS, with 3 teams having not used it so far in a race.[1] One of the main reasons that not all cars use KERS is because it adds an extra 25 kilograms of weight. While not adding to the total car weight, it does incur a penalty particularly seen in the qualifying rounds, as it raises the car's center of gravity, and reduces the amount of ballast that is available to balance the car so that it is more predictable when turning.[2] FIA rules also limit the exploitation of the system. The concept of transferring the vehicle’s kinetic energy using flywheel energy storage was postulated by physicist Richard Feynman in the 1950s.[3] It is exemplified in complex high end systems such as the Zytek, Flybrid,[4] Torotrak[5][6] and Xtrac used in F1 and simple, easily manufactured and integrated differential based systems such as the Cambridge Passenger/Commercial Vehicle Kinetic Energy Recovery System (CPC-KERS).[7]
Xtrac and Flybrid are both licensees of Torotrak's technologies, which employ a small and sophisticated ancillary gearbox incorporating a continuously variable transmission (CVT). The CPC-KERS is similar as it also forms part of the driveline assembly. However, the whole mechanism including the flywheel sits entirely in the vehicle’s hub (looking like a drum brake). In the CPC-KERS, a differential replaces the CVT and transfers torque between the flywheel, drive wheel and road wheel.
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The first of these systems to be revealed was the Flybrid.[8] This system weighs 24 kg and has an energy capacity of 400 kJ after allowing for internal losses. A maximum power boost of 60 kW (81.6 PS, 80.4 HP) for 6.67 seconds is available. The 240 mm diameter flywheel weighs 5.0 kg and revolves at up to 64,500 rpm. Maximum torque is 18 Nm (13.3 ftlbs). The system occupies a volume of 13 litres.[8]
Two minor incidents have been reported during testing of KERS systems in 2008. The first occurred when the Red Bull Racing team tested their KERS battery for the first time in July: it malfunctioned and caused a fire scare that led to the team's factory being evacuated.[9] The second was less than a week later when a BMW Sauber mechanic was given an electric shock when he touched Christian Klien's KERS-equipped car during a test at the Jerez circuit.[10]
Formula One have stated that they support responsible solutions to the world's environmental challenges,[11] and the FIA allowed the use of 81 hp (60 kW; 82 PS) KERS in the regulations for the 2009 Formula One season.[12] Teams began testing systems in 2008: energy can either be stored as mechanical energy (as in a flywheel) or as electrical energy (as in a battery or supercapacitor).[13]
With the introduction of KERS in the 2009 season, only four teams used it at some point in the season: Ferrari, Renault, BMW, and McLaren. Eventually, during the season, Renault and BMW stopped using the system. Vodafone McLaren Mercedes became the first team to win a F1 GP using a KERS equipped car when Lewis Hamilton won the Hungarian Grand Prix on July 26, 2009. Their second KERS equipped car finished fifth. At the following race, Lewis Hamilton became the first driver to take pole position with a KERS car, his team mate, Heikki Kovalainen qualifying second. This was also the first instance of an all KERS front row. On August 30, 2009, Kimi Räikkönen won the Belgian Grand Prix with his KERS equipped Ferrari. It was the first time that KERS contributed directly to a race victory, with second placed Giancarlo Fisichella claiming "Actually, I was quicker than Kimi. He only took me because of KERS at the beginning".[14]
Although KERS was still legal in F1 in the 2010 season, all the teams had agreed not to use it.[15] New rules for the 2011 F1 season which raised the minimum weight limit of the car and driver by 20 kg to 640 kg,[16] along with the FOTA teams agreeing to the use of KERS devices once more, meant that KERS returned for the 2011 season.[17] This is still optional as it was in the 2009 season; as of the 2011 season 3 teams have elected not to use it.[1]
As of 2014, the power capacity of the KERS units will increase from 60 kW to 120 kW. This will be to balance the sport's move from 2.4 litre V8 engines to 1.6 litre V6 engines.[18]
Bosch Motorsport Service is developing a KERS for use in motor racing. These electricity storage systems for hybrid and engine functions include a lithium-ion battery with scalable capacity or a flywheel, a four to eight kilogram electric motor [with a maximum power level of 60 kW (81 hp)], as well as the KERS controller for power and battery management. Bosch also offers a range of electric hybrid systems for commercial and light-duty applications.[19]
Automakers including Honda have been testing KERS systems.[20] At the 2008 1000 km of Silverstone, Peugeot Sport unveiled the Peugeot 908 HY, a hybrid electric variant of the diesel 908, with KERS. Peugeot plans to campaign the car in the 2009 Le Mans Series season, although it will not be capable of scoring championship points.[21]
Vodafone McLaren Mercedes began testing of their KERS in September 2008 at the Jerez test track in preparation for the 2009 F1 season, although at that time it was not yet known if they would be operating an electrical or mechanical system.[22] In November 2008 it was announced that Freescale Semiconductor would collaborate with McLaren Electronic Systems to further develop its KERS for McLaren's Formula One car from 2010 onwards. Both parties believed this collaboration would improve McLaren's KERS system and help the system filter down to road car technology.[23]
Toyota has used a supercapacitor for regeneration on Supra HV-R hybrid race car that won the 24 Hours of Tokachi race in July 2007.[24]
At the NAIAS 2011, Porsche unveiled a RSR variant of their Porsche 918 concept car which uses a flywheel-based KERS that sits beside the driver in the passenger compartment and boosts the dual electric motors driving the front wheels and the 565 BHP V8 gasoline engine driving the rear to a combined power output of 767 BHP.[25]
In 2011, Mazda has announced i-ELOOP, a system which uses a variable-voltage alternator to convert kinetic energy to electric power during deceleration. The energy stored in a double-layer capacitor, is used to supply power needed by vehicle electrical systems. When used in conjunction with Mazda’s start-stop system system, i-Stop, the company claims fuel savings of up to 10%.[26]
KTM racing boss Harald Bartol revealed that the factory raced with a secret Kinetic Energy Recovery System (KERS) fitted to Tommy Koyama's motorcycle during the 2008 season-ending 125cc Valencian Grand Prix. This was illegal, so they were later banned from doing it afterwards.[27]
Automobile Club de l'Ouest, the organizer behind the annual 24 Hours of Le Mans event and the Le Mans Series is currently "studying specific rules for LMP1 that will be equipped with a kinetic energy recovery system. "[28] Peugeot was the first manufacturer to unveil a fully functioning LMP1 car in the form of the 908 HY at the 2008 Autosport 1000 km race at Silverstone.[29] Porsche announced that it will return to Le Mans Prototype LMP 1 in 2014. All indication are that this will be based on the KERS system that is currently being used in the GT3 Hybrid and now the 918 RSR Hybrid that has a 563 BHP conventional gasoline motor boosted to 767 BHP by the KERS system turning at 36,000 RPM.[30][31][32]