An integrated flywheel/machine energy store for road vehicles

This paper describes the design and construction of a flywheel energy storage system for application in a road vehicle. Power transfer to and from the storage device is achieved by an integral solid rotor, axial-field brushless DC machine with twin stators carrying a three-phase, six-pole, toroidal airgap winding on a core wound using amorphous steel ribbon. An analysis of the loss mechanisms in the flywheel is presented and compared with experimental results, which show the benefits of operation in partial vacuum or a helium atmosphere. Experimental data on rotor temperature rise highlights the difficulty of removing heat from the rotor.