Flywheel systems and flywheel bearing modules

1. A flywheel system comprising:

a fixture providing a base and a stator;

a rotor having a cavity for receiving the stator;

a generator/motor module comprising a plurality of permanent magnets mechanically coupled to the rotor and magnetically coupled to windings of the stator, wherein the generator/motor module is configured to convert between rotational energy of rotor and electrical energy in windings of the stator;

an active magnetic bearing module for actively stabilizing the rotor relative to the fixture and positioned at height along the rotation axis approximately the same as the generator/motor module, the active magnetic bearing module comprising:

a plurality of magnetizable elements mechanically coupled with the rotor, and

a plurality of electromagnets mechanically coupled to a shaft and configured to magnetically couple with the plurality of magnetizable elements to actively stabilize the rotor relative to the shaft;

wherein the plurality of electromagnets and the plurality of magnetizable elements of the active magnetic bearing are positioned at greater radii than the plurality of permanent magnets and the windings of the generator/motor module.

2. The flywheel system according to claim 1 , further comprising a levitation module configured to magnetically levitate the rotor above the base.

3. The flywheel system according to claim 2 ,

wherein the levitation module comprises:

a first set of permanent magnets mechanically coupled to the stator, and

a second set of permanent magnets mechanically coupled to the rotor;

wherein the first and the second set of permanent magnets are configured to magnetically couple with each other to bear the load of the rotor to magnetically levitate the rotor above the base.

4. The flywheel system according to claim 3 , wherein the stator is provided as a shaft for the rotor; the first and the second set of permanent magnets are configured to magnetically couple with each other in an axial direction of the shaft.

5. The flywheel system according to claim 1 , wherein the rotor has a vertical rotation axis, wherein the base of the fixture is formed as a horizontal endplate for the rotor.

6. The flywheel system according to claim 1 , wherein the generator/motor module is configured to operate in a generator mode and in a motor mode;

wherein in the generator mode, the generator stator is used to decelerate the rotation of rotor to generate electrical energy, in the form of electrical energy in the windings;

wherein in the motor mode, the generator stator uses electrical energy, supplied from an external source to the windings to accelerate the rotation of rotor and thereby increase the rotational energy of rotor.

7. The flywheel system according to claim 6 , wherein the generator stator is configured for cooling the windings during operation.

8. The flywheel system according to claim 1 , wherein the plurality of magnetizable elements exceed an axial extent of the plurality of electromagnets of the active magnetic bearing module, such that the magnetic coupling between the plurality of magnetizable elements and the plurality of electromagnets remains stable in the presence of axial movement of rotor relative to fixture.

9. The flywheel system according to claim 8 , wherein the axial extent of magnetizable elements exceed the axial extent of electromagnets by 10% in both axial directions.

10. The flywheel system according to claim 1 , wherein the plurality of magnetizable elements of the active magnetic bearing module and mechanically coupled with the rotor are arranged at a first diameter and the plurality of electromagnets of the active magnetic bearing module and mechanically coupled to the shaft are arranged at a second diameter, the first diameter being smaller than the second diameter.