Publications
Technologies for energy storage flywheels and super conducting magnetic energy storage
A flywheel is an electromechanical storage system in which energy is stored in the kinetic energy of a rotating mass. Flywheel systems under development include those with steel flywheel rotors and resin/glass or resin/carbon-fiber composite rotors. The mechanics of energy storage in a flywheel system are common to both steel- and composite-rotor flywheels. In both systems, the momentum of the rotating rotor stores energy. The rotor contains a motor/generator that converts energy between electrical and mechanical forms. In both types of systems, the rotor operates in a vacuum and spins on bearings to reduce friction and increase efficiency. Steel-rotor systems rely mostly on the mass of the rotor to store energy while composite flywheels rely mostly on speed. During charging, an electric current flows through the motor increasing the speed of the flywheel. During discharge, the generator produces current flow out of the system slowing the wheel down. The basic characteristics of a Flywheel system are shown. Steel flywheel systems are currently being marketed in the US and Germany and can be connected in parallel to provide greater power if required. Sizes range from 40kW to 1.6MW for times of 5--120 seconds. At this time sales are limited but growing. The suppliers of the composite type flywheel systems are currently in the prototype stages of development. Flywheel systems offer several potential advantages. FES systems, as their developers envision them will have exceptionally long service lives and low life-cycle costs as a result of minimal O and M requirements. FES systems are compact and self-contained allowing them to be placed in tight quarters, and they contain no hazardous chemicals nor do they produce flammable gases.