In motorsport, the Flybrid system, weighing 24 kg, has an energy capacity of 400 kJ and can provide a power boost of 60 kW for 6.67 seconds. This system uses a flywheel revolving at up to 64,500 rpm. In 2006, a KERS system based on supercapacitors was studied at EPFL as part of the development of the “Formula S2000”, resulting in a 180 kJ system.
Formula One regulations permitted the use of 60 kW KERS units in the 2009 season. Nick Heidfeld achieved the first podium finish with a KERS-equipped car at the Malaysian Grand Prix. McLaren Mercedes secured the first Formula One Grand Prix win with KERS when Lewis Hamilton won the Hungarian Grand Prix on July 26, 2009, with his teammate finishing fifth. Hamilton then took the first pole position with a KERS car at the following race. Kimi Räikkönen won the Belgian Grand Prix on August 30, 2009, with KERS, with Giancarlo Fisichella stating Räikkönen “only took me because of KERS at the beginning”. Although legal in 2010, all teams agreed not to use KERS that season. The system returned in 2011 with a raised minimum weight limit, though three teams initially chose not to implement it. WilliamsF1 developed their own flywheel-based KERS but opted for an electrical system due to packaging issues, later establishing Williams Hybrid Power to sell their developments, which were adopted by Audi’s Le Mans R18 hybrid cars in 2012. Since 2014, KERS power capacity has increased to 120 kilowatts, coinciding with the shift to 1.6 litre V6 turbo engines.
Several automakers have tested KERS systems. Peugeot Sport unveiled the Peugeot 908 HY, a hybrid electric variant with KERS, at the 2008 1000 km of Silverstone). McLaren began testing their KERS system in September 2008, collaborating with Freescale Semiconductor from 2010 to improve the system and transfer technology to road cars. Toyota’s Supra HV-R, which used a supercapacitor, won the Tokachi 24-Hour endurance race in July 2007, becoming the first hybrid car to win such a race. Porsche unveiled a RSR variant of their 918 concept car in 2011, featuring a flywheel-based KERS, though it suffered from imbalance issues. Mazda announced i-ELOOP in 2011, a system using a variable-voltage alternator to save fuel. Bosch and PSA Peugeot Citroën developed a hydraulic hybrid system claiming up to 45% fuel reduction, but abandoned the project in 2015. In 2020, FIAT launched a series of Panda mild-hybrid vehicles with KERS technology.
KERS has also been applied to motorcycles, with KTM racing using a secret system during the 2008 Valencian Community motorcycle Grand Prix, though it was later deemed illegal. The Lit C-1 electric motorcycle also uses KERS as a regenerative braking system. KERS is even possible on bicycles, demonstrated with hydraulic systems and flywheel-based designs.
The Automobile Club de l'Ouest has promoted KERS in the LMP1 class of the 24 Hours of Le Mans since the late 2000s. Peugeot’s 908 HY was the first functioning LMP1 car to utilize the technology. Hope Racing entered the 2011 24 Hours of Le Mans with a Flybrid Systems mechanical KERS, the first car to compete in the event with a hybrid system. Audi and Toyota both developed LMP1 cars with KERS for the 2012 and 2013 races, using flywheel and supercapacitor systems respectively. Porsche’s return to Le Mans in 2014 included a KERS-equipped LMP1 car, the 919 Hybrid, using a battery system.
Beyond motorsport, a KERS using a carbon fibre flywheel, originally developed for Williams Formula One, was retrofitted to London double-decker buses from 2014 to 2016, aiming for a 20% fuel efficiency improvement. The development team received the Dewar Trophy in 2015. The Parry People Mover railcars also use a KERS system with a flywheel and regenerative braking.