If you are a fan of motor sports, more specifically Formula One, then the name Williams is probably familiar as is their KERS system under development. If not here's some background.
Williams is a top Formula One team. They have been working on their own KERS system to implement in Formula One vehicles. KERS stands for Kinetic Energy Recovery System. KERS was developed by Williams Hybrid Power and is considered a flywheel electric hybrid application. The system combines a flywheel use for energy storage with an electric motor. The motor the use kinetic energy from braking to spin the flywheel which turned the motor during acceleration.
First some bad news. Williams has stopped development on the KERS system for Formula One usage. They had considered using the system in cars for the 2010 season, but have now cancelled the program.
Now the good news. Williams will continue work on the KERS system for production, road vehicles. They have doubled their staff size and ramped up development. Williams believes that automakers will adopt their system for mild hybrid applications and have already drawn the attention of Jaguar / Land Rover.
The KERS system draw praise for its simple design that adds little additional weight yet claims to improve efficiency. The system utilizes no additional batteries aside from the starter battery and lacks the complexity of traditional hybrid setups.