Devices and methods for increasing energy and/or power density in composite flywheel energy storage systems

• US 10,050,491 B2
• Filed: 05/31/2017
• Issued: 08/14/2018
• Est. Priority Date: 12/02/2014
• Status: Active Grant

• Current Assignee: Service Management Group, Inc.
• Original Assignee: Service Management Group, Inc.
• Inventors: Groves, Scott Eric, Ault, Stanley K.
• Primary Examiner(s): Rogers, Adam D
• Application Number:
  US15/610,003
• Publication Number:
  US 20170271943A1
• Time in Patent Office: 440 Days
• CPC Class Codes: F16F 15/305 made of plastics, e.g. fibre reinforced plastics [FRP] , i.e. characterised by their special construction from such materials
• CPC Class Codes: H02J 3/30 using dynamo-electric machines coupled to flywheels
• CPC Class Codes: H02K 2213/03 Machines characterised by numerical values, ranges, mathematical expressions or similar information
• CPC Class Codes: H02K 7/025 for power storage
• CPC Class Codes: Y02E 60/16 Mechanical energy storage, e.g. flywheels or pressurised fluids

Abstract

A flywheel formed of a composite material having fibers, oriented substantially in a circumferential direction around the flywheel, embedded in a matrix material. The flywheel having an inner surface, an outer surface, and a thickness therebetween and defining an axis of rotation. A plurality of load masses are distributed circumferentially on the inner surface at a longitudinal segment along the axis. A rotation of the flywheel about the axis with a rotational velocity generating hoop stress in the fibers in the circumferential direction and through-thickness stress is generated in the matrix material in a radial direction. Each load mass produces a force on the inner surface operative to reduce the maximum through-thickness stress in the matrix material as the flywheel rotates about the axis. The rotational velocity otherwise sufficient to produce structural failure of the matrix material produces structural failure of the fibers and not the matrix material.

Claims

1. An apparatus comprising:

a hollow cylindrical flywheel for a motor/generator,

the flywheel being formed of a composite material including a matrix material and fibers oriented at least in part in a circumferential direction around the flywheel embedded in the matrix material,

the flywheel having a longitudinal axis of rotation, a radially inner surface, a radially outer surface, and a radial thickness between the inner surface and the outer surface,

rotation of the flywheel about the axis of rotation generating hoop stress in the fibers in the circumferential direction and through-thickness stress in the matrix material in the radial direction, the material properties of the fibers and the matrix material being such that rotation of the flywheel about the axis of rotation at a first rotational velocity produces failure of the matrix material in the radial direction and not failure of the fibers in the circumferential direction;

a first plurality of load masses distributed circumferentially around, and coupled to, the inner surface of the flywheel at a first longitudinal segment along the axis of rotation; and

a second plurality of load masses distributed circumferentially around, and coupled to, the inner surface of the flywheel at a second longitudinal segment along the axis of rotation, rotation of the flywheel causing each load mass from the first plurality of load masses and each load mass from the second plurality of load masses to produce a radially outwardly directed force on the inner surface of the flywheel, the radially outwardly directed force acting to reduce a maximum through-thickness stress in the matrix material in the first longitudinal segment and the second longitudinal segment of the flywheel such that a second rotational velocity greater than the first rotational velocity produces failure of the fibers in the circumferential direction and not failure of the matrix material in the radial direction.

2. The apparatus of claim 1, wherein each load mass is formed of at least one of a permanent magnetic material or an inert material.

3. The apparatus of claim 1, wherein each load mass in the first plurality of load masses is formed of a permanent magnetic material and each load mass in the second plurality of load masses is formed of a permanent magnetic material.

4. The apparatus of claim 1, wherein each load mass in the first plurality of load masses is formed of a permanent magnetic material and each load mass in the second plurality of load masses is formed of an inert material.

5. The apparatus of claim 1, wherein each load mass in each of the first plurality of load masses and the second plurality of load masses is formed of a permanent magnetic material and has a magnetic polarity, the magnetic polarities of the load masses in each of the first plurality of load masses and the second plurality of load masses alternating circumferentially around the flywheel, each load mass in the first plurality of load masses being disposed in axial alignment with, and having its magnetic polarity oriented in the same direction as, a corresponding load mass in the second plurality of load masses, the first plurality of load masses being axially spaced from the second plurality of load masses to define an axial stator gap therebetween having a longitudinal gap length, the apparatus further comprising:

a stator having a plurality of conductive windings disposed thereon and having an axial thickness less than the longitudinal gap length, the stator being disposed in operative relationship to the flywheel such that at least a portion of the windings are disposed axially between the first plurality of load masses and the second plurality of load masses in the stator gap such that rotation of the flywheel relative to the stator produces a flow of electrical current in the windings.

6. The apparatus of claim 5 wherein:

each load mass in the first plurality of load masses and the second plurality of load masses has a radial dimension, the radial dimensions of all of the load masses in the first plurality of load masses and the second plurality of load masses is substantially equal to a first radial dimension,

each load mass in the first plurality of load masses and the second plurality of load masses has a density, the densities of all of the load masses in the first plurality of load masses and the second plurality of load masses is substantially equal to a first density,

each of the first plurality of load masses and the second plurality of load masses producing a pressure on the inner surface of the flywheel upon rotation of the flywheel at the first velocity substantially equal to a first pressure, the apparatus further comprising;

a third plurality of load masses distributed circumferentially around, and coupled to, the inner surface of the flywheel within in the axial stator gap,

each load mass in the third plurality of load masses having a radial dimension, the radial dimensions of all of the load masses in the third plurality of load masses being substantially equal to a second radial dimension less than the first radial dimension, the difference between the first radial dimension and the second radial dimension defining a radial extent of the stator gap within which at least the portion of the windings is disposed,

each load mass in the third plurality of load masses having a density, the densities of the third plurality of load masses being substantially equal to a second density greater than the first density,

the third plurality of load masses producing a pressure on the inner surface of the flywheel upon rotation of the flywheel at the first velocity substantially equal to the first pressure.

7. An apparatus comprising:

a rotor configured to be disposed within a flywheel energy storage device, the rotor being formed of a composite material including a matrix material and fibers oriented at least in part in a circumferential direction around the rotor embedded in the matrix material, the rotor having a longitudinal axis of rotation and a radially inner surface, the rotor configured to rotate about the longitudinal axis relative to a stator;

a first plurality of load masses coupled to the inner surface of the rotor, each load mass from the first plurality of load masses having a first density and a first radial thickness, a first portion of the first plurality of load masses being distributed along the inner surface in the circumferential direction at a first longitudinal segment along the axis of rotation, a second portion of the first plurality of load masses being distributed along the inner surface in the circumferential direction at a second longitudinal segment along the axis of rotation; and

a second plurality of load masses coupled to the inner surface of the rotor, each load mass from the second plurality of load masses having a second density greater than the first density and a second radial thickness less than the first radial thickness, the second plurality of load masses being distributed along the inner surface in a circumferential direction at a third longitudinal segment along the axis of rotation, the third longitudinal segment being between the first longitudinal segment and the second longitudinal segment,

the first plurality of load masses and the second plurality of load masses covering the inner surface such that a substantially uniform pressure is exerted on the inner surface of the rotor when the rotor is rotated about the longitudinal axis relative to the stator.

8. The apparatus of claim 7, wherein each load mass from the first plurality of load masses is formed of a permanent magnetic material and each load mass from the second plurality of load masses is formed of a nonmagnetic material.

9. The apparatus of claim 7, wherein each load mass from the first plurality of load masses and each load mass from the second plurality of load masses is formed of a permanent magnet material.

10. The apparatus of claim 7, wherein a pressure exerted by each load mass from the first plurality of load masses on the inner surface of the rotor when the rotor is rotated about the longitudinal axis is equal to a pressure exerted by each load mass from the second plurality of load masses on the inner surface of the rotor when the rotor is rotated about the longitudinal axis.

11. The apparatus of claim 7, wherein each load mass from the first plurality of load masses is formed of a permanent magnet material and each load mass from the second plurality of load masses is formed of a nonmagnetic material, the rotor is rotatably disposed about the stator such that a portion of the stator is disposed between the first portion of the first plurality of load masses and the second portion of the first plurality of load masses, the second plurality of load masses being disposed between a circumferential surface of the stator and the inner surface of the rotor,

the portion of the stator disposed within the space defined between the first portion of the first plurality of load masses and the second portion of the first plurality of load masses having a plurality of conductive windings disposed thereon, the rotor configured to (1) rotate the first plurality of load masses relative to the stator to induce a flow of electrical current in the conductive windings or (2) rotate relative to the stator in response to a flow of electrical current in the conductive windings.

12. The apparatus of claim 7, wherein the rotor has a radially outer surface, the rotor having a thickness between the radially inner surface and the radially outer surface,

the rotation of the rotor about the axis of rotation generates hoop stress in the fibers in the circumferential direction and through-thickness stress in the matrix material in the radial direction, the material properties of the fibers and the matrix material being such that a first rotational velocity produces failure of the matrix material in the radial direction and not failure of the fibers in the circumferential direction,

the substantially uniform pressure exerted on the inner surface of the rotor when the rotor is rotated about the longitudinal axis relative to the stator being such that a second rotational velocity greater than the first rotational velocity produces failure of the fibers in the circumferential direction and not failure of the matrix material in the radial direction.

13. An apparatus comprising:

a rotor configured to be disposed within a flywheel energy storage device, the rotor being formed of a composite material including a matrix material and fibers oriented at least in part in a circumferential direction around the rotor embedded in the matrix material, the rotor having a longitudinal axis of rotation and an inner surface,

the rotor including a first plurality of magnets distributed along the inner surface in the circumferential direction at a first longitudinal segment along the axis of rotation and a second plurality of magnets distributed along the inner surface in the circumferential direction at a second longitudinal segment along the axis of rotation, the first plurality of magnets and the second plurality of magnets defining a space therebetween;

a stator disposed within the flywheel energy storage device, a portion of the stator being disposed within the space defined between the first plurality of magnets and the second plurality of magnets; and

a plurality of load masses distributed along the inner surface in the circumferential direction, the plurality of load masses being formed of a nonmagnetic material, the plurality of load masses disposed within the space defined between the first plurality of magnets and the second plurality of magnets such that the plurality of load masses is between the inner surface of the rotor and a circumferential surface of the portion of the stator,

the first plurality of magnets, the second plurality of magnets, and the plurality of load masses collectively exerting a substantially uniform pressure on the inner surface of the rotor operative in reducing a radial stress within the rotor when the rotor is rotated about the longitudinal axis.

14. The apparatus of claim 13, wherein each magnet from the first plurality of magnets has a magnetic polarity, the magnetic polarities of the first plurality of magnets alternating circumferentially around the inner surface of the rotor,

each magnet from the second plurality of magnets has a magnetic polarity, the magnetic polarities of the second plurality of magnets alternating circumferentially around the inner surface of the rotor.

15. The apparatus of claim 14, wherein the portion of the stator disposed within the space defined between the first plurality of magnets and the second plurality of magnets having a plurality of conductive windings disposed thereon, the rotor configured to (1) rotate relative to the stator to induce a flow of electrical current in the conductive windings or (2) rotate relative to the stator in response to a flow of electrical current in the conductive windings.

16. The apparatus of claim 13, wherein each magnet from the first plurality of magnets and each magnet from the second plurality of magnets has a first density and a first radial thickness,

each load mass from the plurality of load masses has a second density and a second radial thickness, the second density being greater than the first density, the second radial thickness being less than the first radial thickness,

a pressure exerted by each magnet from the first plurality of magnets on the inner surface of the rotor when the rotor is rotated about the longitudinal axis is equal to a pressure exerted by each magnet from the second plurality of magnets on the inner surface of the rotor when the rotor is rotated about the longitudinal axis.

17. The apparatus of claim 13, wherein the portion of the stator is disposed within the spaced defined between the first plurality of magnets and the second plurality of magnets such that a first surface of the portion of the stator is spaced a distance from a surface of each magnet from the first plurality of magnets and a second surface of the portion of the stator is spaced the distance from a surface of each magnet from the second plurality of magnets,

the circumferential surface of the portion of the stator being spaced the distance from a surface of each load mass from the plurality of load masses.

18. The apparatus of claim 13, wherein the plurality of load masses is a first plurality of load masses, the first plurality of magnets, the second plurality of magnets, the portion of the stator, and the first plurality of load masses collectively forming a motor/generator portion, the portion of the stator is a first portion of the stator, the motor/generator portion is a first motor/generator portion,

the rotor including a third plurality of magnets distributed along the inner surface in the circumferential direction at a third longitudinal segment along the axis of rotation and a fourth plurality of magnets distributed along the inner surface in the circumferential direction at a fourth longitudinal segment along the axis of rotation, the first plurality of magnets and the second plurality of magnets defining a space therebetween, the stator having a second portion disposed within the space defined between the third plurality of magnets and the fourth plurality of magnets, the apparatus further comprising:

a second plurality of load masses distributed along the inner surface in the circumferential direction, the second plurality of load masses being formed of a nonmagnetic material and being disposed within the space defined between the third plurality of magnets and the fourth plurality of magnets such that the second plurality of load masses is between the inner surface of the rotor and a circumferential surface of the second portion of the stator,

the third plurality of magnets, the fourth plurality of magnets, the second portion of the stator, and the second plurality of load masses collectively forming a second motor/generator portion; and

a third plurality of load masses distributed along the inner surface in the circumferential direction, the third plurality of load masses being formed of a nonmagnetic material and being disposed at a fifth longitudinal segment along the axis of rotation, the fifth longitudinal segment along the axis of rotation being disposed between the first motor/generator portion and the second motor/generator portion.

19. The apparatus of claim 18, wherein the first plurality of magnets, the second plurality of magnets, the third plurality of magnets, the fourth plurality of magnets, the first plurality of load masses, the second plurality of load masses, and the third plurality of load masses cover the entire inner surface of the rotor and collectively exert a substantially uniform pressure on the inner surface of the rotor operative in reducing a radial stress within the rotor when the rotor is rotated about the longitudinal axis.