Method for producing a kinetic energy storage system
A flywheel energy storage system incorporates various embodiments in design and processing to achieve a very high ratio of energy stored per unit cost. The system uses a high-strength steel rotor rotating in a vacuum envelope. The rotor has a geometry that ensures high yield strength throughout its cross-section using various low-cost quenched and tempered alloy steels. Low-cost is also achieved by forging the rotor in a single piece with integral shafts. A high energy density is achieved with adequate safety margins through a pre-conditioning treatment. The bearing and suspension system utilizes an electromagnet that off-loads the rotor allowing for the use of low-cost, conventional rolling contact bearings over an operating lifetime of several years.
1. A flywheel device comprising:
a sealed housing section;
a rotor disposed within the housing section;
a first bearing housing comprising lower contact bearings and a second bearing housing comprising upper contact bearings disposed between the rotor and a plate; and
an off-loading electromagnet configured to provide a vertical off-loading force that lifts the rotor against the upper contact bearings in a vertical direction and off of the lower contact bearings.
2. The flywheel device of claim 1 , further comprising:
a load sensor configured to measure a load applied to at least one of the upper contact bearings or the lower contact bearings; and
a control system configured to adjust a field of the off-loading electromagnet based on the measured load.
3. The flywheel device of claim 2 , wherein the controller is configured to compare the measured load to predetermined load limits.
4. The flywheel device of claim 2 , wherein the load applied to at least one of the upper contact bearings or the lower contact bearings comprises a vertical force that is applied against the at least one of the upper contact bearings or the lower contact bearings.
5. The flywheel device of claim 1 , further comprising a plurality of stiffening ribs welded to a top plate of the housing section.
6. The flywheel device of claim 1 , further comprising a spring configured to exert a minimum required force in the vertical direction on at least one of the lower contact bearings or the upper contact bearings via the rotor.
7. The flywheel device of claim 1 , wherein the housing section is hermetically sealed and provides a vacuum envelope within which the rotor is disposed.
8. The flywheel device of claim 7 , wherein a shaft of the rotor extends through the vacuum envelope via a low-friction lip seal.
9. The flywheel device of claim 8 , wherein the low-friction lip seal comprises a fluoropolymer lip seal.
10. The flywheel device of claim 8 , wherein a motor and at least one of the first bearing housing or the second bearing housing are located outside the vacuum envelope.
11. The flywheel device of claim 7 , wherein the housing section is configured to support the rotor, provide an alignment fixture for the first bearing housing, the second bearing housing, and a shaft of the rotor, and provide a suspension system for the rotor.
12. The flywheel device of claim 1 , wherein the housing section comprises a top plate that provides a suspension element for the rotor.
13. The flywheel device of claim 1 , wherein the off-loading electromagnet is structurally integrated into a top plate of a vacuum chamber formed by the housing section.
14. The flywheel device of claim 1 , wherein the off-loading electromagnet comprises a single coil of insulated copper wire.
15. The flywheel device of claim 1 , wherein the housing section comprises a top plate, a bottom plate, and a cylindrical section.
16. The flywheel device of claim 1 , further comprising an actuator configured to remotely adjust an axial position of the rotor within the housing section.
17. The flywheel device of claim 16 , wherein the actuator comprises a motor-driven worm gear.
18. The flywheel device of claim 1 , wherein the rotor comprises a disc-shaped rotor coupled to a separate non-magnetic shaft.
19. The flywheel device of claim 1 , wherein the rotor comprises a plurality of laminated plates that are adhesively bonded together.
20. The flywheel device of claim 1 , wherein the off-loading force that lifts the rotor against the upper contact bearings in the vertical direction causes the rotor to apply a vertical force to the upper contact bearings.