Ricardo Tests “Leakproof “Flywheel System

Researchers at Ricardo plc are developing a touchless magnetic coupling to tap energy stored in high-speed flywheels.

The technology addresses an obvious challenge with conventional flywheel designs: Extracting their energy requires a rotating axle that passes through the wheel's vacuum-sealed enclosure, thus creating friction and possible leakage from the axle bearings.

The Ricardo system uses magnetism to transfer energy to and from a completely sealed carbon-fiber flywheel. The company notes that the concept is about 60 years old and is being use now in heat pumps and magnetic-geared oil drilling devices.

Ricardo's design uses an external continuously variable transmission with 5.75:1 epicyclical gear to connect the flywheel and vehicle powertrain. The system, which operates at speeds between 9,000 rpm and 60,000 rpm, can store as much as 1 mega-Joule energy collected during braking and downhill coasting. The flywheel has a half-life the time it takes to spin down to half speed and thus half energy of about six minutes.

The system offers 80% of the efficiency and one-third the cost of a fully integrated electric hybrid powertrain, according to the company. It says the unit's compact design makes it relatively easy to incorporate the flywheel into existing vehicles.