Flywheel Energy Storage Device

Abstract

The flywheel energy storage device illustratively includes a continuously curved fiber-resin composite ovoid shell. A hub is concentrically disposed inside and outside the shell on the shaft. A plurality of radially oriented fiber-resin composite spiral windings with uniform widths constitute the ovoid shell and connect the shell to the hub for common rotation and torque transmission. A laminated inner structure connects to the outer ovoid shell and provides compressive support to the outer ovoid shell. When rotating, the ovoid shell stretches slightly, increasing the effective moment of inertia of the flywheel at operating speeds.

Description

[Technical field]

[0001] This application claims the benefit of priority application of U.S. Provisional Patent Application No. 62 / 857,088, entitled "Catenary Flywheel Kinetic Battery," filed on June 4, 2019, to James B. Clegern, the entire contents of which are incorporated herein by reference as if fully set forth herein.

[0002] The present invention relates to a flywheel energy storage device. [Background technology]

[0003] Flywheels have a history of over 2,000 years as energy storage devices in the form of rotational kinetic energy. With larger form factors (typically 10 kWh or more), they can provide the core of energy storage systems (ESS) for renewable and conventional power grids ranging from multi-module utility systems to single unit residential / commercial systems. The combination of a vacuum-sealed flywheel and ultra-low friction magnetic bearings is particularly well suited for ESS applications that require frequent daily charge / discharge cycles because they have essentially no worn parts. Examples of these high cycle ESS applications include supporting intermittent renewable energy, powering electric vehicle charging stations, and stabilizing grid frequency regulation. In general, however, the current generation of flywheels that may be used in these applications rotate at relatively low speeds and are formed from a number of construction materials such as steel and composite fiber-resin laminates. These high-quality flywheels are typically costly for the energy they can store, whether in initial cost or installation costs, limiting their application to locations where volume and mass are not limited.

[0004] When checking the energy storage capacity of flywheels, they are largely limited by the structural design and choice of structural materials. The structural design specifies how the flywheel is connected to the rotating shaft to transmit torque and where the structural mass is placed to maximize the rotational moment of inertia. The properties of the structural materials (i.e., strength, density, elasticity, fatigue resistance, etc.) determine the operating speed and lifespan of the flywheel according to the structural design. For example, with each evolution of structural materials, from the Stone Age, Bronze Age, and Steel Age to the current composite age, the performance improvement of the flywheel structural materials leads to faster speeds for a particular structural design.

[0005] The kinetic energy storage (Ek) capacity of a flywheel is determined by the standard equation Ek=1 / 2Iω^2, where the structural design mass position of moment of inertia (I) and flywheel speed (ω) are the two energy storage factors. Among the two drivers of energy storage, increasing the structural mass and moment of inertia (I) of a particular structural material is the standard method to achieve greater energy storage. This includes adding thickness or height to conventional disk, cylindrical rim, or annular rim structured flywheel designs after a particular structural material reaches its maximum speed. The use of composite materials in conventional mass focus flywheels has been commercially proven and can store 25 kWh of energy in units of 1,250 kg. The use of steel materials in the manufacture of conventional mass focus flywheels has been commercially proven and can store 50 kWh of energy in units of 2,270 kg. Even the use of concrete materials in conventional mass focus flywheels has been commercially proven and can store 10 kWh of energy in units of 3,000 kg.

[0006] Increasing flywheel energy storage by increasing mass presents three challenges. First, the energy storage capacity of a flywheel increases linearly with the increase in flywheel mass, which leads to practical operational constraints on manufacturing, delivery, and deployment of large flywheels with high energy storage capacity. Second, as the flywheel mass increases, the overall system quality and complexity increases as each supporting flywheel system (i.e., bearings, support structures, and vacuum housing) must also "scale up" to handle the increased mass. Third, the overall quality increase and subsystem complexity make the increase in energy storage a significant cost driver, driving the price of many flywheel energy storage systems far beyond a reasonable return on investment.

[0007] The second energy storage thrust element focuses on increasing the flywheel speed to double the energy storage capacity of the flywheel. Flywheel speed can be increased in two areas: structural design and stronger structural materials. The use of lighter and stronger composite materials instead of heavy metals and fiberglass has dominated traditional disk, cylindrical rim, or annular rim type flywheel designs with traditional structural qualities. In the 1970s, research was conducted to explore new structural flywheel designs to improve energy storage capacity, taking advantage of the flexibility of a new manufacturing technology: continuous filament winding of resin-impregnated composite fiber materials. These new structural designs are promising, but only increase the mass of the traditional annular rim flywheel designs. Summary of the Invention [Problem to be solved by the invention]

[0008] A high speed, compact flywheel system suitable for storing excess energy from renewable and conventional utility power plants and distributing the energy when needed is disclosed. The high speed elliptical egg-shaped flywheel includes a composite shell formed by a combination of a helically wound band of resin impregnated composite fiber material and an internal composite structure that provides compression support. In one example, the fiber wound composite shell is coupled to a rotating shaft via a pair of structural flange plates concentrically arranged on either side of the shaft, and a plurality of composite shell fiber bands are connected for torque transmission. A majority of the flywheel shell interior is hollow to maximize the flywheel moment of inertia mass under the maximum allowable shell radius. [Means for solving the problem]

[0009] The formation of the egg-shaped and elliptical curvature of the flywheel is to support the centripetal force which varies with the radius of each fiber wound on the outside of the spiral. This allows structural support in two planes, which allows a significant increase in the allowable tip speed compared to conventional disc or cylindrical flywheels of the same diameter and construction material. The fully composite nature of the elliptical flywheel construction increases operational safety and allows maximum and consistent use of the strength of composite materials in optimal implementation.

[0010] In one example, an elliptical egg shaped flywheel includes a plurality of sets of helical windings, each set having a uniform width. Each set of helical windings has a layer around an exterior surface of the shell and a layer located and extending into the hub on either side of the axis of rotation. In another example, each set of helical windings has a substantially continuous single-ended filamentary material wound in a unidirectional relationship and encapsulated in a resin matrix. In another example, during rotation, each set of helical windings is uniformly biased across the width of each winding. In another example, each set of helical windings has a layered composite shell oriented together radially. In another example, the helical windings are positioned in mutually overlapping relationship at a portion of the hub proximate the axis of rotation.

[0011] In one example, each layer of radially oriented helical winding initially has an angle of about 5 degrees, gradually increasing to about 35 degrees to move the mass accumulation of the wound layers away from the axis of rotation, increasing the moment of inertia of the flywheel.

[0012] In one example, the radially oriented helical windings are arranged in a thickness configuration that transfers the stresses of the tensile tip under compressive stress closer to the axis of rotation, thereby maximizing the effective strength of the laminated layers of composite material of the fiber windings.

[0013] The elliptical egg-shaped flywheel includes a laminated internal structure connected to the outer egg-shaped shell to provide compression support to the outer egg-shaped shell. In one example, the internal structure is formed from a metal or substantially continuous single-end filamentary material wound in a unidirectional relationship into multiple layers and encapsulated in a resin matrix. In another example, the internal structure is formed from a metal composite laminate layer wound in a unidirectional relationship into multiple layers and bonded to the inner layer of the outer egg-shaped shell. The minimum inside-outside ratio of the internal structure compared to the outer diameter of the egg-shaped shell is about 0.1.

[0014] In one example, the inner and outer circumferential surfaces of the oval shell are spheroidal in shape. In one example, the oval shell spiral winding layer is used twice to control the inertial mass of the flywheel.

[0015] In one example, the flywheel energy storage capacity is arranged to increase or decrease through multiple winding layers as the layers increase or decrease.

[0016] The elliptical egg flywheel further includes a double boss plate connected to both sides of the innermost and outermost egg shell layers, connecting the egg shells to the shaft to realize common rotation and torque transmission. In order not to exceed the structural strength of the boss plate, the radius of the boss plate is kept below 15% of the elliptical egg radius, thus eliminating the shortcomings of the traditional flywheel structure. Effect of the Invention

[0017] The systems and methods described herein have several advantages related to energy storage, including, but not limited to, providing a flywheel that more effectively utilizes structural qualities, providing a way to increase flywheel speed without structural failure, providing a flexible flywheel structure that can accommodate load distribution, customizing an economical flywheel structure to accommodate your energy storage needs, and combining the advantages of a small, high energy density flywheel with a small, compact subsystem to form a low cost energy storage system. Further advantages will become apparent from a review of the following description and drawings. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view of an example of a flywheel energy storage device. [Diagram 2] FIG. 1 is a side view of an example of an elliptical egg shaped flywheel. [Diagram 3] FIG. 1 is a cross-sectional view of an example elliptical egg-shaped flywheel including a bearing subsystem and a transmission subsystem. [Figure 4] FIG. 13 is a detailed cross-sectional view of the right bearing subsystem and gearbox subsystem. [Diagram 5] FIG. 2 is a detailed cross-sectional view of the left bearing subsystem. [Figure 6] FIG. 13 is a cross-sectional view of another example of an elliptical egg-shaped flywheel. [Figure 7] FIG. 13 is a cross-sectional view of another example of an elliptical egg-shaped flywheel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Before proceeding, the terms "includes" and "including" as used herein include, but are not limited to, "includes" or "including", "includes at least" or "including at least". "Based on" refers to "based on" and "based at least in part on".

[0020] FIG. 1 is a perspective view of an example flywheel energy storage device 10. The system 10 includes a sealed flywheel component 12 on a mounting structure 14. A vacuum port 16 is provided by the sealed flywheel component 12. The flywheel component 12 may be operably associated with a motor or generator 18 mounted to a platform 20. For example, the flywheel component 12 may be operably associated with the generator 18 via a gearbox link rod 22. In one example, the generator 18 includes cooling pipes 24 that may be operably associated with a cooling subsystem 26.

[0021] In one example, the generator 18 may be operably associated with a power control subsystem 28 having a power connection 30 and a control and monitoring connection 32. For example, the power control subsystem 28 may be operably associated with the generator 18 via a mating controller 34.

[0022] At least a portion of the control of the subsystems and / or gearbox is based on operating conditions in the flywheel component 12. For example, at least a portion of the control is based on one or more sensors via connection 36.

[0023] In one example, the flywheel component 12 includes a high speed three-dimensional (3D) elliptical egg flywheel 50 mounted on a shaft 52 that may be associated with the gearbox 22. FIG. 2 shows a side view of the elliptical egg flywheel 50. The elliptical egg flywheel 50 provides a large inertial mass and improved work rate compared to a two-dimensional disk, ring, or cylinder (even a disk, ring, or cylinder of the same or similar diameter made from the same construction material). Table 1 shows a comparison of example flywheel performance under the same geometric and material constraints.

[0024] [Table 1]

[0025] In the above example, the elliptical egg shaped flywheel 50 includes layers of spirally wound resin impregnated composite fiber material that form an egg shaped shell shape. This configuration provides a method of transferring significant inertial mass to the maximum flywheel diameter.

[0026] The flywheel inertial mass is adjusted by adjusting the number of helical winding layers in the elliptical egg-shaped flywheel 50. Each layer of the helically wound composite fiber material is in a nearly purely elongated state, maximizing the structural material performance, and the curvature of the egg-shaped composite shell minimizes stress concentrations that would impair structural integrity. The 3D nature of the egg-shaped composite shell causes the composite fiber structural material at the maximum diameter of the flywheel to share stresses in two planes, similar to the membrane stresses in a spherical pressure vessel, resulting in hoop stresses in the flywheel that are significantly greater than the typical hoop stress limits of a hoop-wound circular disk, circular ring, or cylinder.

[0027] During operation, the vacuum sealed flywheel 50 is connected to the flywheel shaft 52 and connected to the two-part magnetic transmission device of the external motor / generator 18, transmitting torque and energy through the sealed vacuum shell 12, and matching the flywheel rotation speed with the operating speed of the external motor / generator 18 through gear transmission.

[0028] Although not shown, the shell encases the motor / generator, connecting components (e.g., connecting to the flywheel vacuum shell 12) and external magnetic transmission devices. In one example, one or more sensors 36 provide position, temperature, vibration, flywheel revolutions per minute (rpm) and pressure readings that are transmitted to a control display via wires built into the vacuum shell 12.

[0029] The external motor / generator 18 is supported by the translation platform 14 and the controller 28, allowing coupling and decoupling of the external magnetic transmission and vacuum shell. This allows the vacuum sealed elliptical egg flywheel 50 to be disconnected from the external motor / generator 18, eliminating a significant source of standby power loss. A small backup chemical battery is typically charged by the motor / generator 18 when in operation, or by another external power source when the motor / generator 18 is disconnected, to provide the necessary power for the sensor components and active axial thrust bearings. When the motor / generator 18 is disconnected, the standby time of the elliptical egg flywheel ESS to 50% power surplus can exceed 250 hours. Using an external plug-in power source or solar array as the backup chemical battery to provide charging, the standby time of the elliptical egg flywheel ESS to 50% power surplus can exceed 350 hours.

[0030] Figure 3 is a cross-sectional view of the elliptical egg-shaped flywheel 50, including bearing subsystems 54a, 54b and transmission subsystem 56. Figure 4 is a detailed cross-sectional view of the right bearing subsystem 54a (area of ​​detail 4 in Figure 3) and the gearbox subsystem 56. Figure 5 is a detailed cross-sectional view of the left bearing subsystem 54b (area of ​​detail 5 in Figure 3).

[0031] The elliptical egg flywheel 50 includes an oval composite shell 58 with its radial composite fibers wound on a laminated composite compression support structure 60. The elliptical egg flywheel 50 is mounted on the shaft 52 via an internal boss plate support 64, an external balance boss plate 66 and a boss plate attachment 62 on a shell guide plate 68 and an internal boss plate 70. The elliptical egg flywheel 50 is supported on either end of the shaft 52 via an axial ground bearing, an electromagnet axial stabilizer 72 and a radial ground bearing 74. Also visible are the rotating PM bearing 76, the fixed PM bearing 78 and the axial electromotive bearing 80, which carry most of the load and stabilize the system. Also visible are the internal PM gearbox 82, the reducer plate 84, the rear bearing box plate 86 and the bearing box 88.

[0032] The elliptical egg flywheel 50 may be constructed on an internal compression support 90. In one example, the internal compression support 90 is a hollow cylinder circumferentially wound from a resin impregnated composite fiber material of radius r1, the thickness of which provides compression support during flywheel operation. The internal compression support is bonded in place with the internal elliptical egg winding of the outer egg shell.

[0033] In one example, the composite fiber materials used in the elliptical egg-shaped flywheel construction are selected to have minimal elongation when stressed (e.g., similar to carbon / graphite fibers) so as not to damage the structural integrity of the flywheel to the vacuum shell. Some composite materials (e.g., reinforced plastics, fiberglass, ultra-high density polyethylene, basalt, and aramid fibers) continue to elongate or "creep" under load and may not be suitable for the flywheel application due to the high continuous load demands during active operation.

[0034] In one example, the shell of an elliptical egg-shaped flywheel 50 is constructed from a plurality of spirally wound resin impregnated composite fiber laminate layers, each layer having a thickness t0 such that each layer completely covers the circumference of the flywheel radius r0. An inner laminate layer follows the inner elliptical egg shape that is removed after winding is completed, forming an inner void. The inner laminate layer follows a low angle helical winding path around the flywheel shaft and shaft support, and is bonded to the outer surface of the inner boss flange plate. Each additional laminate layer gradually increases the angle of its helical winding path until the maximum angle is equal to the outer radius r1 of the inner support cylinder.

[0035] After increasing the number of laminate layers necessary to provide stress support and inertial mass, the outer laminate layers form an elliptical path with the best helix angle. At each laminate layer between the two layers, the elliptical path transitions to a vertical path through an elliptical cross section through the thickness of the inner hollow cylindrical support, allowing the compressive stresses to be concentrated in the areas of the inner structural support where they are greatest.

[0036] The elliptical egg shaped flywheel 50 is supported and stabilized along its axis of rotation and axis 52 by active electromagnetic thrust bearings, axially mounted radial magnetic bearings and shell fixed radial magnetic bearings, axially powered bearings and backup ground bearings. A portion of the external boss flange plate on each side of the flywheel provides fine adjustment of the inertia shaft balance mass along the axis of rotation.

[0037] The elliptical egg-shaped flywheel structure includes an inner compression support with a radius r1 and a thickness t1, an outer boss flange plate, an inner boss flange plate, a shaft support and an inner shaft support, as shown in Figure 3. In this figure, it also includes a spiral winding guide plate connected to the end of the inner compression support.

[0038] Also shown in Figure 3 is a complete elliptical outer spiral winding layer of radius r0, with a compression support of width W, which also serves as an axial compression support. Also shown in Figure 3 is a partial elliptical outer spiral winding layer of radius r0, with multiple internal compression supports of width W. In the side view, the location of the internal compression supports is shown, e.g., the system relative to the diameter of the flywheel.

[0039] In one elliptical egg-shaped flywheel shell example, stepped composite fiber resin windings are shown, with an initial low angle extending to an elliptical path of optimal helix angle, intersecting with the outer radius of a hollow internal compression support cylinder. A winding of multiple helically wound resin impregnated composite fiber laminate layers comprises a composite shell, with each layer being egg-shaped.

[0040] Finite element analysis results for an elliptical egg shaped flywheel 50 having inner and outer elliptical spiral wound laminate layers supported in compression by an inner hollow cylinder. Predicted safety factors (SF) are included to interpret the flywheel stress analysis under an operating speed of 36000 rpm.

[0041] Before proceeding, it should be noted that the above examples are illustrative and not limiting, as other devices and / or device configurations may be used to perform the operations described herein.

[0042] In one example, the components and connections shown in the figure can be used for the following operations: The operations shown and described herein are used to realize the examples, and it is not noted that the order of the operations is limited and other operations may be performed.

[0043] In an example operation, the elliptical egg flywheel 50 rotates around a level or vertical axis on a shaft 52 within the vacuum shell 12 supported by magnetic bearings (FIGS. 3-5). The magnetic bearings provide support in the radial and axial directions. The speed of the elliptical egg flywheel 50 can be increased or decreased via a transmitted torque of the vacuum shell 12 (e.g., a magnetic transmission device connected to the flywheel shaft 52 and the external motor / generator 18), and thus its energy storage level can also be increased or decreased. The magnetic transmission acts as an intermediary between the elliptical egg flywheel 50 and the external motor / generator 18, allowing rotational energy to be transmitted through the walls of the vacuum shell 12 via magnetic coupling. Power input and output are provided by the external motor / generator 18, which is powered by a user source, accelerates the elliptical egg flywheel 50, converts the power into rotational kinetic energy, and transfers power to the user when the user decelerates the elliptical egg flywheel 50, converting the rotational kinetic energy into electrical energy.

[0044] When an elliptical egg-shaped flywheel operates, various designs increase the available energy storage. In one example, the inner and outer elliptical arches of the egg-shaped shell stretch slightly (e.g., about 1-2% stretch compared to the resting state) due to centripetal forces pulling the structure radially. This slightly stretches the outer radius of the flywheel, increasing the moment of inertia when the flywheel operates, and improving the energy storage capacity by 3-5%. Such flexibility allows the 3D structural design to adapt to its load distribution, while also providing a positive benefit to the energy storage capacity of the flywheel.

[0045] In one example, the elliptical egg-shaped flywheel 50 may utilize carbon / graphite fiber composite fibers, which have a total elongation of approximately 1-2% under load. When these fibers are spirally wound radially, the outer radius of the flywheel increases slightly under load due to the expected elongation. This increases the flywheel moment of inertia as the flywheel operates, improving the energy storage capacity by approximately 3-5%. Such flexibility allows the 3D structural design to adapt to its load distribution while providing a positive benefit to the energy storage capacity of the flywheel.

[0046] In one example, the inner structural composite cylinder is allowed to radially bow (from the compressive stress of the ovoid shell) and also radially expand the hoop composite fiber. The resulting slight increase in radius of the composite cylinder bows into the upper void space, avoiding extra stress on the outer ovoid shell as with a conventional ring edge.

[0047] In one example, by moving the helical turn angle of each subsequent winding layer of an oval shell upwards, the fibers (which would otherwise be concentrated about the axis) are moved to a larger radius, increasing the effective moment of inertia of the flywheel, while at the same time increasing the tensile stress in the fiber layers due to the cross-sectional thickness of the shell still radiating outward in the axial direction.

[0048] In one example, the overlapping layers of helical external windings arranged in an elliptical arch form the 3D characteristics of an egg-shaped composite shell. This allows the structural composite in the flywheel egg-shaped shell to carry stresses in two planes similar to the membrane stresses in a spherical pressure vessel. This allows the elliptical egg-shaped flywheel to exceed the typical hoop stress limit of a hoop-wound circular disk, circular ring or cylinder under the same radius by approximately 40%, greatly increasing the operating rotational speed of the elliptical egg-shaped flywheel and improving its energy storage level. As the aspect ratio of the elliptical egg-shaped flywheel approaches 1.0 and the flywheel becomes spherical (rather than egg-shaped), the stresses in two planes can be improved by approximately 100% over the typical hoop stresses. The increase in compressive stress due to the increased aspect ratio must be addressed by adding an internal flywheel structure.

[0049] Combining these five sides into an elliptical, egg-shaped flywheel structure increased the energy storage capacity by five times compared to a conventional flywheel with the same construction material, mass and diameter.

[0050] As an example, an example elliptical egg-shaped flywheel shown in FIG. 1 was designed and evaluated using finite element analysis (FEA). The flywheel design example has an egg-shaped shell and internal support windings with a medium strength 3000 mPa carbon composite fiber laminate layer impregnated with epoxy resin. The boss flange was simulated using stainless steel AISI A514. The simulated flywheel was modeled in a sealed vacuum environment and operates nearly frictionless using magnetic bearings, as shown in FIG. 3. The maximum diameter of the simulated flywheel is about 1.0 meter, and the width at the part where it connects to the shaft is about 0.45 meter.

[0051] The analysis showed that the energy storage in the simulated flywheel was approximately 50.9 kWh, and the flywheel inertia was approximately 24.1 kg-m 2 and the operating speed is approximately 36,000 turns / min.

[0052] System stresses maintained a safety factor of approximately 1.4 to 2.2. Not only was the simulated flywheel operation within the commercially expected safety factors, but the gravimetric energy density based on the total flywheel mass was approximately 205 w-h / kg and the gravimetric energy density based on the flywheel volume was approximately 490 w-h-liter. In comparison, a conventional 2D cylindrical flywheel had a gravimetric energy density of approximately 20 w-h / kg and approximately 45 w-h-liter. Fatigue analysis showed that the elliptical egg flywheel would provide a useful life of over 200,000 charge-discharge cycles.

[0053] Using high-strength carbon composite fiber laminate layers with a strength of 4100mPa, the same simulated flywheel geometry achieved an operating speed of over 49000rpm and an energy storage capacity of approximately 97kWh under the same safety factor.

[0054] Figures 6-7 show cross-sectional views of other example elliptical egg flywheels. Elliptical egg flywheel 150 in Figure 6 is more conical than elliptical egg flywheel 50. Elliptical egg flywheel 150 has the same width (width W1 and width W of flywheel 50 are approximately the same) and has an internal support structure 153 near axis 152. Elliptical egg flywheel 250 in Figure 7 is wider (width W2) and has a central internal support structure 253 and another support structure 254 closer to axis 252.

[0055] The systems and methods disclosed herein provide an elliptical oval flywheel that has greater energy storage capacity per unit mass than that of known rotational energy storage devices. It is understood that the elliptical oval flywheel described herein is particularly suited to provide energy storage with a small operating footprint and mass for use in deployed utility and renewable energy locations, residential and commercial locations, and potential transportation, e.g., powering electric vehicle charging stations.

[0056] It should be noted that the examples shown and described are provided for illustrative purposes and are not intended to be limiting. Other examples may be contemplated, including, but not limited to, a vertically oriented elliptical flywheel.

Claims

1. a fiber-resin composite elliptical oval shell having an axial axis and a wall extending perpendicular to the axial axis; a hub boss plate on each side of the egg-shaped shell, the hub boss plates being concentrically disposed on the inside and outside of the shell and connected to the shaft; A plurality of fiber-resin composite spiral windings spirally wound in the radial direction of the egg-shaped shell are connected to a hub boss plate to realize common rotation and torque transmission to the shaft in the axial direction; an axially oriented internal structure between walls extending perpendicular to the axial direction of the ovoid shell provides compression support; When rotating, the elliptical egg shell stretches slightly, increasing the moment of inertia around the elliptical egg shell, A flywheel energy storage device in which the helical winding angle of each layer of radially oriented helical winding is initially at an angle of about 5 degrees and gradually increases to about 35 degrees to move the mass accumulation of the wound layers away from the axis of rotation and increase the moment of inertia of the flywheel.

2. 10. The flywheel energy storage device of claim 1, further comprising a plurality of sets of helical windings, each set of helical windings having a uniform width.

3. 3. The flywheel energy storage device of claim 2, wherein each set of helical windings has layers, said layers extending around an outer surface of the shell and the hub on either side of the axis of rotation.

4. 3. The flywheel energy storage device of claim 2, wherein each set of helical windings comprises a substantially continuous single-ended thread of material wound in a unidirectional relationship and encapsulated in a resin matrix.

5. 3. The flywheel energy storage device of claim 2, wherein each set of helical windings is energized uniformly across the width of each winding during rotation.

6. 3. The flywheel energy storage device of claim 2, wherein each set of helical windings forms a radially oriented layered composite shell.

7. 3. The flywheel energy storage device of claim 2, wherein the helical windings have portions disposed proximate the axis of rotation of the hub in overlapping relationship with one another.

8. 10. The flywheel energy storage device of claim 1 further comprising a laminated internal structure connected to the elliptical egg shell to provide compression support.

9. 9. The flywheel energy storage device of claim 8, wherein the laminated internal structure is formed from metal or a substantially continuous single-ended filamentary material wound in a plurality of layers in a unidirectional relationship and encapsulated in a resin matrix.

10. 10. The flywheel energy storage device of claim 9, wherein a minimum ratio of a radius of the laminated internal structure compared to an outer diameter of the oval shell is about 0.

1.

11. 2. The flywheel energy storage device of claim 1, wherein the inner structure is formed from metal, composite laminate layers wound in a plurality of layers in a unidirectional relationship and bonded to an inner layer of the elliptical egg-shaped shell.

12. 12. The flywheel energy storage device of claim 11, wherein a minimum ratio of a radius of the internal structure compared to an outer diameter of the oval shell is about 0.

1.

13. 10. The flywheel energy storage device of claim 1, wherein the elliptical egg-shaped shell has an available aspect ratio of about 0.1 to 1.

0.

14. 2. The flywheel energy storage device of claim 1, wherein the inner and outer circumferential surfaces of the oval shell are spheroidal in shape.

15. 10. The flywheel energy storage device of claim 1, wherein the oval shell spiral winding layer is used to control the inertial mass of the flywheel.

16. 16. The flywheel energy storage device of claim 15, arranged such that the flywheel energy storage capacity increases or decreases through the multiple winding layers as the layers are increased or decreased.

17. 2. The flywheel energy storage device of claim 1, further comprising a double boss plate connected to both sides of the innermost and outermost oval shell layers to connect the oval shells to the shaft for common rotation and torque transmission.

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