Magnetically coupled flywheel

Abstract

A stabilization system for a rotating load, such as a flywheel, includes a mechanical bearing to continuously support a shaft of the rotating load so as to hold the shaft at a substantially fixed axis of rotation. A magnetic stabilization assembly includes a plurality of electromagnets arranged around the shaft. Control circuitry for controls a resultant magnetic field generated by the electromagnets such that the magnetic field acts on a ferromagnetic element of the shaft to reduce imbalance forces acting on the shaft.

1 . A flywheel energy storage system for storing electrical energy, the system comprising:
 a flywheel including a rotatable mass and a shaft, the mass configured to rotate together with the shaft, the flywheel being enclosed within an evacuable enclosure, the shaft supported by bearings on opposite sides of the rotatable mass; and   an open-frame electric motor/generator unit having an annular stator located outside of the enclosure and a rotor, the rotor being fixed to the shaft in a cantilevered manner within the enclosure so as to rotate within the stator and magnetically couple to the stator.   
     
     
         2 . The system of  claim 1 , wherein the flywheel comprises lead enveloped in a shell that comprises carbon fiber. 
     
     
         3 . The system of  claim 1 , wherein the flywheel comprises a plurality of glass fibers, each fiber being at least partially wrapped around a column of a plurality of columns that are arranged in a circular pattern that is centered on an axis of rotation of the flywheel, such that each fiber extends substantially radially outward from the axis when the flywheel rotates. 
     
     
         4 . The system of  claim 1 , wherein the flywheel includes a structure with an eccentric mass distribution that is rotatable to adjust a balance of the flywheel. 
     
     
         5 . The system of  claim 1 , wherein a section of the enclosure between the rotor and the stator comprises glass. 
     
     
         6 . The system of  claim 1 , wherein the bearings comprise a mechanical bearing to continuously support a shaft of the rotating load so as to hold the shaft at a substantially fixed axis of rotation and a magnetic stabilization assembly including a plurality of electromagnets arranged around the shaft, the system further comprising a control circuitry for controlling a resultant magnetic field generated by the electromagnets such that the magnetic field acts on a ferromagnetic element of the shaft to reduce imbalance forces acting on the shaft. 
     
     
         7 . The system of  claim 6 , comprising a sensor to sense a vibration of the shaft, the control circuitry being configured to control the resultant magnetic field so as to minimize the sensed vibration. 
     
     
         8 . The system of  claim 1 , further comprising:
 a plurality of the flywheels;   a direct current (DC) bus;   a plurality of the motor/generator units, each motor/generator unit of said plurality of the motor/generator units being magnetically coupled to a flywheel of said plurality of the flywheels;   a plurality of controller/inverters, each controller/inverter being electrically coupled to a motor/generator unit of said plurality of the motor/generator units and to the DC bus; and   a central controller to control each controller/inverter so as to set a discharge rate for each of the flywheels when its motor/generator unit is operating in a discharge mode, and to increase a voltage level of a voltage signal generated by the motor/generator unit in the discharge mode.   
     
     
         9 . The system of  claim 1 , wherein a cap of the enclosure between the stator and the rotor comprises a magnetically susceptible material. 
     
     
         10 . The system of  claim 9 , wherein the magnetically susceptible material comprises fiberglass. 
     
     
         11 . The system of  claim 9 , wherein the magnetically susceptible material comprises a glass composite material. 
     
     
         12 . The system of  claim 1 , wherein the motor/generator unit comprises a DC motor.