Contributions to the development of a flywheel energy storage system

The high rotational speeds of flywheel energy storage (FES) systems introduce energy losses in the form of friction and in the control of unstable magnetic bearings. The primary objective of this research is the reduction of these energy losses to an acceptable level of {dollar}<{dollar}0.1% of maximum charge per hour. Methods to minimize energy losses are the use of permanent magnetic bearings and vacuum containment.; A result of Earnshaw's theorem is that permanent magnet bearings must be externally stabilized through active control, superconducting material or through a mechanical contact. For reliability reasons and to reduce the power used for active control the bearings studied here are stabilized with a mechanical contact. A preliminary investigation of the friction in this type of bearing is presented. Systems with this type of bearing are shown to be open loop stable. Control methods to improve the response to disturbances are proposed. To assist with the control design a new formulation of the equations of motion of rotating axisymmetric bodies is developed. This formulation is developed in a sensor based coordinate frame and shows significant advantages over Euler angle based equations.; To reduce the effect of air friction the flywheel is contained in a vacuum. The need for vacuum is accepted among flywheel researchers. However the level of vacuum necessary is not agreed on in the literature. A calculation of the level of vacuum necessary to significantly reduce friction losses is presented and experimentally verified.