Flywheel based energy storage system

Abstract

An energy storage system according to at least one implementation comprises a motor, a first rotatable shaft segment, a second rotatable shaft segment, a flywheel, and a vacuum chamber containing the motor, the first and second shaft segments, and the flywheel. The first rotatable shaft segment can have a first end rotatably coupled to the motor. A first end of the second rotatable shaft segment can be coupled to a second end of the first rotatable shaft segment. The flywheel rotatably can be coupled to a second end of the second rotatable shaft segment. The motor may be a reluctance motor. The flywheel can be made of a composite material.

Description

Attorney Docket No.000551-0001-WO1 Flywheel Based Energy Storage System

[0001] This application claims the benefit of U.S. provisional patent application no.63 / 691,122, filed on September 5, 2024, which is incorporated by reference herein in its entirety. FIELD

[0002] At least one implementation of the present disclosure pertains to energy storage systems, and more particularly, to a flywheel based energy storage system. BACKGROUND

[0003] The transition to a carbon-free, sustainable energy future depends heavily on cost-effective energy storage solutions. These systems are crucial as they enable the storage of energy generated from low-cost, renewable sources like wind and solar, making that energy available when demand arises. However, current energy storage technologies, including lithium-ion batteries, flow batteries, and flywheel systems, have proven to be prohibitively expensive. When these storage methods are combined with clean energy sources, the resultant energy costs often exceed those associated with fossil fuel power plants. Utility-scale battery energy storage systems provide energy when the price of electricity is high, but they are not economical for storage of much of the excess renewable energy generation around the world. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] One or more implementations of the present disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.

[0005] FIG.1 illustrates a side view of a flywheel.

[0006] FIG.2 illustrates an example of a reluctance motor.

[0007] FIG.3 shows an example implementation of a portion of the energy storage system.Attorney Docket No.000551-0001-WO1

[0008] FIG.4 is a block diagram of an example implementation of the energy storage system.

[0009] FIG.5 shows an example of an electromagnetic coil.

[0010] FIG.6 shows an example of a coolant system for the flywheel.

[0011] FIG.7A shows a cutaway perspective view of a shipping container that contains two flywheel based energy storage systems such as described herein.

[0012] FIG.7B shows a cutaway front elevation view of the shipping container shown in FIG.7A. DETAILED DESCRIPTION

[0013] In this description, references to “an implementation”, “one implementation” or the like, mean that the particular feature, function, structure or characteristic being described is included in at least one implementation of the technique introduced here. Occurrences of such phrases in this specification do not necessarily all refer to the same implementation. On the other hand, the implementations referred to also are not necessarily mutually exclusive. Overview

[0014] Introduced here is an energy storage system that, in at least some implementations, is based on a reluctance motor and a composite flywheel, both housed within a vacuum chamber. When used in conjunction with renewable energy sources, the system can lower overall energy costs to a point where they are more competitive than those of fossil fuel-based power generation, driving affordable clean energy adoption and supporting electrification and clean transportation. This flywheel based energy storage system is particularly beneficial for remote and underserved geographic regions, offering reliable and affordable energy for homes, industries, communities, and electric transportation. It can be a significant step forward in enabling clean energy to economically replace fossil fuels, thereby supporting the broader goal of achieving a sustainable energy future.

[0015] Some conventional flywheel based energy storage systems combine the motor and flywheel as a single component. When the flywheel and motor are combined in this manner, either the gap between the motor's stator and its rotor needs to become larger, or the flywheel size needs to be reduced due to systemAttorney Docket No.000551-0001-WO1 dynamics and potential failure modes. The gap may need to be larger because the flywheel naturally expands when it is rotating at high speed, and the gap needs to accommodate this expansion. However, increasing the size of the gap to accommodate expansion of the flywheel significantly reduces the motor’s efficiency. On the other hand, reducing the size of the flywheel also reduces the overall energy storage capacity of the system.

[0016] A potential alternative to using a motor and flywheel combined as a single component is to have the motor and flywheel be separate components on a common drive shaft. However, this generally requires that either the gap be the same size at both the motor and at the flywheel, or that a complicated design be used to accommodate gaps of different sizes at the motor and flywheel, which tends to be expensive, bulky / heavy and / or less fault tolerant.

[0017] In contrast, the system introduced here provides that the motor and the flywheel are separate components. However, rather then sharing a common drive shaft, they are coupled to separate drive shaft segments, which in turn are coupled together via one or more shaft coupling mechanisms. This separation is impactful, because it allows the flywheel system to maintain a small gap between the motor's stator and rotor during the flywheel's operation and in the event of a fault, thereby providing high efficiency, without requiring a very complicated design. This design enables the use of a large composite flywheel while preserving system stability and motor efficiency. This solution thereby offers a promising alternative to the storage solutions mentioned above, by significantly reducing storage costs.

[0018] Additionally, some conventional large-capacity flywheel based energy storage systems use flywheels made of high-strength steel. These flywheels typically have large masses and radii, making them unsuitable for transportation and operation in standard shipping containers, at least at the desired performance specifications needed for many high capacity use cases. In contrast, the system introduced here uses a flywheel made of a much lighter-than-steel composite material, enabling the system to comply with standard shipping container size and weight restrictions.

[0019] Further, the system introduced here optionally may include additional components to enable the system to have higher efficiency, operate safely (includingAttorney Docket No.000551-0001-WO1 in the event of faults), and require minimal maintenance throughout the system’s lifetime.

[0020] To provide a deployable system for many short-duration energy storage applications, it is highly desirable that the full system can be contained within a standard 20-foot shipping container. Also, to minimize shipping costs, the full system should weigh less than the maximum allowed cargo weight of 44,000 lbs. The system introduced here odes both. Indeed, at least two such systems can fit within a standard shipping container. Furthermore, the system can use standard three-phase 480 VAC input power and standardized communication protocols such as Modbus for easy installation with new and existing power systems. Consequently, the system can be shipped and installed easily for multiple clean energy applications around the world.

[0021] The system introduced here significantly reduces the cost per kilowatt hour (kwh) of an energy storage system (which can fit within a standard 20-foot shipping container), by increasing overall system kwh, increasing efficiency, and reducing component costs. When combined with renewable energy generation technologies, this system can provide a lower cost of energy than fossil fuels, and can economically support additional clean energy applications such as fast electric vehicle (EV) charging, low-cost hydrogen production, and low-cost industrial electrification.

[0022] To increase the amount of energy that can be stored in a space that fits within a standard shipping container, the system uses composite flywheel based energy storage. FIG.1 shows a side view of an example flywheel 100 that can be used in the system introduced here. The flywheel 100 can be, for example, a solid or hollow cylinder for ease of manufacturing. To charge, an electric motor spins up the flywheel to thousands of revolutions per minute (RPM) to store angular kinetic energy. Then, in a manner similar to regenerative braking, the motor slows down the flywheel to discharge energy.

[0023] Typically, flywheels comprise high strength steel or composite. High strength steel flywheels provide a large mass, which affects their angular acceleration (spin-up capability). In contrast, a lighter composite flywheel can spin up more quickly.Attorney Docket No.000551-0001-WO1

[0024] The energy stored in a flywheel is given by equation (1):where I is the moment of isolid cylinder, I is given by equation (2):1= (2 2)where m is the cylinder’s mass and r is the radius. Therefore, to increase energy stored, angular velocity and radius can be increased. Since it is desirable, for at least some implementations, to limit the radius of the flywheel according to the size of the standard shipping container and to limit its mass according to a shipping container’s maximum cargo weight, the system introduced here uses a composite material flywheel instead of a high strength steel flywheel.

[0025] To increase the conversion efficiency of electrical power to mechanical power, the system in at least some implementations uses a reluctance motor. FIG.2 illustrates an example of a reluctance motor 200 that is suitable for this purpose. Reluctance motors generate torque through magnetic reluctance. When compared to induction motors and permanent magnet motors, reluctance motors have higher efficiency when used in a vacuum. In addition, reluctance motors are easier and less expensive to manufacture than permanent magnet and induction motors, leading to an overall reduction in full system cost per kwh. Nonetheless, in other implementations, the motor could be a permanent magnet motor, induction motor, or other type of motor.

[0026] In at least some implementations, the flywheel has a mass of at least 8,000 kg and a radius of at least 1 meter, and the energy storage system has a total energy storage capacity of at least 1,100 kWh. System Architecture

[0027] FIG.3 shows an example implementation of a portion of the energy storage system introduced here. The flywheel 100 and motor 200 are contained within a vacuum chamber 310 (FIG.3 is a cutaway view to allow visualization of the motor and flywheel). As noted, the motor 200 may be a reluctance motor and / or the flywheel 100 may be a composite flywheel. An electronics box 320 contains theAttorney Docket No.000551-0001-WO1 power and control electronics for operating the energy storage system. Cables 330 from the electronics are routed through one or more pass-throughs 340 in the shell of the vacuum chamber 310 to the relevant components inside the vacuum chamber 310, as discussed further below.

[0028] FIG.4 is a block diagram of an example implementation of the energy storage system introduced here. The energy storage system 400 includes a vacuum chamber 310 that contains the motor 200 and the flywheel 100, and other components (discussed below). As noted, the motor 200 may be a reluctance motor and / or the flywheel 100 may be made of a composite material. In at least some embodiments, as illustrated in FIG.4, the motor 200 and the flywheel 100 do not share the same driveshaft. Instead, the motor 200 is coupled to the flywheel 100 via a plurality of rotatable shaft segments. In the illustrated implementation, the motor is coupled to the flywheel via a first rotatable shaft segment 402 and a second rotatable shaft segment 404, which are coupled to each other via a shaft coupler 406. The shaft coupler 406 transfers rotary motion from one shaft segment to the other.

[0029] The system is powered and controlled by electronics in the electronics box 320. The electronics include power circuitry 410 and control circuitry 412. The power circuitry 410410 includes a bidirectional inverter 422 and a motor driver 424. The bidirectional inverter 422 can input AC power from an electrical grid and convert it to a nominal DC voltage on a bus, which is then used to drive the motor 200. For example, the input power from the grid may be 480 VAC, and the output from the inverter 422 to the motor driver 424 may be 800 VDC. The output of the inverter 422 to the motor driver 424 drives the motor 200 at a rotational speed determined according to a signal from the control circuitry 412. Power flows from the grid to the motor 200 for charging the flywheel energy storage system and flows from the motor 200 to the grid for discharging.

[0030] The control circuitry 412 receives various sensor outputs 414, 416, from the motor 200 and other components of the system that are discussed below. Based on the sensor outputs 414, 416, and preprogrammed instructions and data, the control circuitry 412 provides control outputs to the bidirectional inverter 422 and the motor driver 424 to control the speed of the motor 200.Attorney Docket No.000551-0001-WO1

[0031] In at least some implementations, the control circuitry 412 can include, for example, one or more programmable general-purpose microprocessors (e.g., functioning as one or more central processing units (CPUs)), programmable digital signal processors (DSPs), programmable microcontrollers, programmable network processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), or the like, or any combination thereof.

[0032] Additionally, the control circuitry 412 can include one or more memories coupled to the processing component(s) mentioned above, that store computer program instructions and data for carrying out some or all of the control related operations described above. Such memories may be or include one or more of read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), etc., static memory (e.g., flash memory, static random access memory (SRAM), etc.), hard disk, etc.

[0033] The control circuitry 412 may further include a communication interface or adapter capable of communicating with one or more remote computers or other processing devices and / or circuits via a communication channel. The communication channel may be or include a local area network (LAN), an intranet, an extranet, and / or the Internet, and may include one or more wired and / or wireless connections. Computer device 600 can operate as a server in a client-server network environment.

[0034] The control circuitry 412 also may include, be coupled to, or provide an interface to be coupled to, one or more input / output (I / O) devices, to allow a user to interface directly with the control circuitry, such as for purposes of configuration and testing. Such I / O devices may include, for example, one or more of a display device, keyboard, mouse, microphone, speaker, etc.

[0035] Any or all of the above-mentioned components of the control circuitry may communicate with each other via an interconnect, which can be or include one or more buses, adapters, point-to-point connections, or any combination thereof.

[0036] To increase electrical power conversion efficiency, the bidirectional inverter 422 and the motor driver 424 each can use wide-bandgap semiconductors. In this context, “wide-bandgap” refers to semiconductors with bandgaps above 2 eV.Attorney Docket No.000551-0001-WO1 Traditional battery systems typically use insulated gate bipolar transistors (IGBTs) for AC / DC / AC conversion, due to their cost-effectiveness, requiring only two conversions (AC to DC, DC to AC). However, flywheel energy storage systems employ four conversions (AC to DC, DC to motor, motor to DC, and DC to AC), making it desirable to use more efficient semiconductors. Wide-bandgap semiconductors, such as silicon carbide (SiC) or gallium nitride (GaN), offer higher efficiency and support higher switching frequencies, allowing for smaller inductors and capacitors. Although they are more expensive than IGBTs, wide-bandgap semiconductors may enable a less expensive and more efficient power electronics system overall.

[0037] To maximize energy storage within the size and weight limits of a standard shipping container, the flywheel 100 can be made from a composite material, as mentioned above. The composite material can be, for example, carbon fiber or glass fiber. The composite material preferably has a high tensile strength, such as Intermediate Modulus carbon fiber. The composite material can be layered, with each layer bonded using an adhesive such as epoxy or glue. The composite material makes up the majority of the flywheel’s mass, and typically will be at least 65% of the flywheel’s total mass, depending on the specific composite and adhesive used. The flywheel can be a solid or hollow cylinder for ease of manufacturing. Theangular velocity limits are given by equation (3):= (3)where is tensile stress, is density, is radius,is angular velocity. Composite material typically has a tensile stress of 4.0 x 109 pascals and a density of 1800 kg / m3.

[0038] The flywheel’s radius may be limited (i.e., in at least some implementations and / or for at least some use cases) by the size of the vacuum chamber walls and the gaps between the shipping container, the vacuum chamber, and the flywheel. The flywheel 100 should be given room to expand as it stretches radially while being spun and increases in temperature. The flywheel’s height also may be limited by the shipping container’s height and weight limits. In at least some implementations, in addition to the flywheel, the shipping container contains the motor 200, the vacuum chamber 310, one or more electromagnets (discussedAttorney Docket No.000551-0001-WO1 below), electronics box 320, and peripherals. The flywheel’s height can be selected to ensure that it fits within the vacuum chamber and that the entire system complies with the shipping container’s weight limits. Reluctance Motor

[0039] In at least some implementations, the motor 200 is a switched reluctance motor. Reluctance motors are higher in efficiency, less expensive to manufacture, and use no rare earth metals, in comparison to induction motors and permanent magnet motors. Since the motor 200 is placed in a vacuum in the technique introduced here, windage losses are not an issue. A switched reluctance motor, as opposed to a synchronous reluctance motor, can be used, since it is easier to manufacture both the stator and the rotor for a switched reluctance motor.

[0040] A switched reluctance motor’s voltage for each phase is as set forth inequation (4):where is the voltage, is the stator resistance, is the current, is the flux linkage, and is the angle between the rotor and stator. To reduce losses, the stator’s resistance can be reduced and / or the gap between the rotor and stator can be reduced. The stator’s resistance is a function of the size of the wires, so a large- diameter wire can be used when winding each phase. For the gap size, precision machining and a precision bearing system can be used. Losses are proportionate to the square of the gap size. Power Electronics

[0041] The motor 200 can be driven by power circuitry 410 (FIG.4), which may perform electrical power conversion using wide-bandgap semiconductors, such as SiC or GaN, to maximize efficiency and reduce overall electronic component costs. IGBTs may additionally or alternatively be used for power conversion, depending on the implementation and component availability. For example, SiC MOSFETs (transistors) can be controlled by using an FPGA with a pulse width modulation (PWM) algorithm. The switching frequency can be chosen to be high enough to reduce losses through the transistors. For example, the switchingAttorney Docket No.000551-0001-WO1 frequency may be higher than 100 kHz. The exact optimal switching frequency is implementation specific. Additionally, a high switching frequency allows for smaller inductor and capacitor filters, helping to make the entire power electronics system suitable for both efficiency and cost. Heat pipes can be used to move heat from the transistors to a cooling system, which is discussed below. Vacuum Chamber

[0042] The vacuum chamber 310 is the flywheel’s and motor’s housing and is designed to hold the weight of the flywheel 100 and contain a high vacuum. The vacuum chamber’s shell can be made of aluminum (e.g., heat-treated), steel, or stainless steel, for example. One or more vacuum-rated electrical feedthroughs in the vacuum chamber’s shell can be used to route cables to power the motor 200 and the electromagnet bearing system, discussed below. The specific vacuum level required for operation can be determined from testing. However, the vacuum chamber and associated vacuum pump should be able to achieve and maintain a low pressure level of no more than 3 kPa in the vacuum chamber during normal operation. In this regard, note that it is not feasible to achieve a perfect vacuum, so references to “vacuum” in this document are intended to mean near-vacuum pressure levels, or pressure levels that are closer to perfect vacuum than to normal atmospheric pressure. Bearing System

[0043] To reduce friction losses and component replacement costs, the energy storage system 400 can employ an electromagnetic bearing system to maintain the stability of the flywheel and motor during operation. Referring again to FIG.4, an example of the bearing system is shown to include (illustrated in cross- section) electromagnetic bearings 440. Each bearing 440 may be shaped as a ring that surrounds a draft shaft segment. Depending on the forces required for each bearing 440 and the temperature conditions, the bearing system can include one or more permanent magnets, one or more electromagnets, or a combination thereof. While other flywheel systems use ball bearings to cut costs, those systems typicallyAttorney Docket No.000551-0001-WO1 require a cooling system or regular replacement due to failure or wear over time. Additionally, ball bearings introduce friction to the spinning flywheel, reducing overall system efficiency. Additionally, ball bearings often require extra components, such as a vacuum lip seal, which further increases costs and losses. Control Algorithm

[0044] As the center of mass of the flywheel 100 shifts during spin-up and spin-down, the control circuitry 412 (FIG.4) can implement a control algorithm, such as a proportional-integral-derivative (PID) control loop, to control the electromagnetic bearings 440 to ensure stability. The control algorithm can dynamically adjust the forces on each side of each bearing 440 by adjusting the current on each side of the bearing, to maintain constant rotational dynamic forces. This approach prevents resonance effects that could cause the radial force on the upper or lower drive shaft to overpower a bearing 440, potentially leading to a fault. Flywheel Levitation

[0045] To reduce the load on the bearings 440, the flywheel’s weight can be offloaded by using one or more electromagnetic coils 450, placed above and / or below the flywheel 100. An example of an electromagnetic coils 450 is shown in FIG.5. The control circuitry 412 can control the electromagnetic coils 450, used in conjunction with a metallic lifting plate 460, to levitate the flywheel 100 during operation. Permanent magnets may also be used to partially offset the load on the electromagnetic coils 450. The current through the electromagnetic coils 450 can be adjusted by the control circuitry 412 to maintain a gap between each coil 450 and the motor 200, flywheel 100, or the lifting plate 460. Unlike some systems that use a mechanical stop above or below the flywheel (which increases friction and system losses), this approach reduces the reliance on physical bearings, enhancing efficiency and performance.

[0046] In other flywheel systems, the shaft or the ferrous flywheel itself are employed to lift either the entire flywheel load or a portion of it, thereby reducing the weight on the bearing system. In the system introduced here, since the upper portion of the flywheel’s drive shaft is connected to the motor 200, the ring- or disk-shapedAttorney Docket No.000551-0001-WO1 metallic lifting plate 460 placed below the flywheel 100 helps to maintain structural support from below, rather than placing it above the flywheel 100 (which would shift the support structure to the top). The lifting plate 460 can be attached to, or be an integral part of, the lower shaft segment 470, i.e., the shaft segment below the flywheel 100.

[0047] To levitate the flywheel 100, an electric current is passed through the electromagnetic coils 450 positioned immediately above and below the lifting plate 460 (see FIG.4). During operation, the electromagnetic coil above the lifting plate 460 carries a stronger current than the one below, generating a lifting force that raises the lifting plate 460. The control circuitry 412 continuously adjusts the currents in both coils 450 to maintain levitation, ensuring that the lifting plate 460 stays suspended between them without contacting either coil. Brake System

[0048] A brake 480 configured to engage in the event of a fault can be added to the system 400 to prevent damage in the event of a fault. As shown by example in FIG.4, the brake 480 can be placed below the flywheel 100 to reduce forces placed on the motor 200 and the shaft coupling 406. The brake 480 can be or include a steel disk or cylinder connected to or integral with the lower shaft segment 470, which therefore spins with the drive shaft. The brake container 490 can be a steel container, which may be attached to the inside of the vacuum chamber 310. In the event of a major system failure (e.g., electromagnetic bearing failure, vacuum seal rupture, or flywheel overstress), the brake 480 can be engaged by reducing or shutting off the force provided by the magnetic levitation system. This action allows the flywheel 100 and its lower shaft segment 470 to be lowered, thereby causing the brake 480 to fall into the brake container 490 and contact at least the bottom inner surface of the brake container 490 (and possibly also the sides). When so engaged, the spinning brake 480 grinds against the inside of the brake container 490, gradually slowing the flywheel 100 to a complete stop. This action causes the brake 480 and the brake container 490 to heat up considerably, due to friction. However, once the brake 480 and brake container 490 cool down to a safe temperature and the fault is resolved, the flywheel system can resume normal operation. The brakeAttorney Docket No.000551-0001-WO1 container 490 can be surrounded by a passive vibration dampening material or system (not shown) to reduce noise and vibration during braking. While some flywheel systems incorporate a brake directly into the flywheel, that approach increases wear and tear on the flywheel and requires costly noise dampening systems. Cooling System

[0049] Although the flywheel 100 operates in “a vacuum,” it still experiences air drag losses, because a perfect vacuum cannot be achieved. These losses cause the flywheel 100 to heat up, which can weaken the composite and potentially lead to failure due to overstress. To prevent this from occurring, a cooling system 600, an example of which is shown in FIG.6, can be used to remove heat from the flywheel. A vacuum-rated coolant can be applied to the flywheel or its shaft to transfer heat to a stationary component outside the flywheel. As shown in FIG.6, the coolant may be provided through a conduit 610 and dripped or sprayed from a nozzle onto the flywheel or lower shaft segment 470, where it then drips into a pan or basin 620 beneath the flywheel 100 or is projected by centripetal forces onto a side component. The coolant can be collected in the pan or basin 620 and transferred to a heat exchanger or reservoir (not shown) to dissipate the heat. Once cooled to a specified temperature, the coolant can be recirculated to continue cooling the flywheel 100. The specific flow rates, types of coolant, and temperatures are implementation- specific and can be determined through testing.

[0050] Additionally, the energy storage system 400 can have a small ball bearing or coolant bearing (not shown) placed on top of or below the motor 200 or the flywheel 100, to remove heat from the flywheel 100 passively. This bearing system can physically and thermally couple the rotating flywheel shaft or the motor 200 to the vacuum chamber’s shell to allow heat from the flywheel 100 to transfer to the vacuum chamber’s shell. The bearing system can be small to limit friction losses. Shipping and Use ConfigurationAttorney Docket No.000551-0001-WO1

[0051] In at least some implementations, two full flywheel units can be placed next to each other inside a standard 20-foot long shipping container, as mentioned above, an example of which is illustrated in FIGS.7A and 7B (which are cutaway views). The total weight (including shipping container) can be just under 44,000 lbs., which is the current maximum legal cargo weight in the U.S. for a 20-foot shipping container. In a standard double-door configuration, the shipping container 700 has an opening on each of its two smallest sides, each of which is fitted with a set of double doors 710. The electronics box, electrical feedthroughs and peripherals can be accessed from one those openings. The electronics box (see FIG.3) can be mounted on the exterior of the vacuum chamber’s shell. The power grid connections and switches may be moved to the door or the side of the shipping container based on project specifications. Peripherals such as the vacuum pump and electromagnetic power supply (not shown) can be placed so as to be readily accessible and easy to replace from the double doors. Installation and Safety

[0052] To reduce installation costs, the energy storage system introduced here is designed to be suitable for above-grade installation on a base platform. Conventional steel flywheels or other systems that typically require below-grade placement within reinforced safety structures, due to the risk of fragmentation during an overstress event. In contrast, the system introduced here incorporates built-in safety mechanisms. For example, in the event of an overstress, the system engages the brake system by deactivating the electromagnetic bearings. This capability eliminates the need for specialized safety infrastructure beyond standard industrial electrical protection. While an emergency spin-down may produce significant noise, that can be mitigated as described above, and the vacuum chamber ensures full containment, preventing any breach and maintaining operational safety. Examples

[0053] The following are summarizing examples of what is described above:

[0054] 1. An energy storage system may include: a motor; a first rotatable shaft segment having a first end rotatably coupled to the motor; a second rotatableAttorney Docket No.000551-0001-WO1 shaft segment, wherein a first end of the second rotatable shaft segment is coupled to a second end of the first rotatable shaft segment; a flywheel rotatably coupled to a second end of the second rotatable shaft segment; and a vacuum chamber containing the motor, the first and second rotatable shaft segments, and the flywheel.

[0055] 2. The energy storage system as example 1 describes, wherein the motor is a reluctance motor.

[0056] 3. The energy storage system as either of examples 1 or 2 describe, further may include a lifting plate, coupled to or integral with the flywheel, by which to cause electromagnetic levitation of the flywheel during operation of the system.

[0057] 4. The energy storage system as any of examples 1-3 describe, wherein the lifting plate is disposed below the flywheel during operation of the system.

[0058] 5. The energy storage system as any of examples 1-4 describe, wherein the lifting plate is configured for use as a brake to slow rotation of the flywheel.

[0059] 6. The energy storage system as any of examples 1-5 describe, further may include a brake to slow rotation of the flywheel.

[0060] 7. The energy storage system as any of examples 1-6 describe, further may include: a lifting plate, coupled to or integral with the flywheel, by which to cause electromagnetic levitation of the flywheel during operation of the system; and a brake to slow rotation of the flywheel.

[0061] 8. The energy storage system as any of examples 1-7 describe, wherein the vacuum chamber further contains the lifting plate and the brake.

[0062] 9. The energy storage system as any of examples 1-8 describe, further may include an electromagnetic bearing system coupled to the flywheel.

[0063] 10. The energy storage system as any of examples 1-9 describe, further may include a cooling system configured to apply a vacuum-rated coolant to the flywheel or to a shaft segment coupled to the flywheel.

[0064] 11. An energy storage system may include: a reluctance motor; a first rotatable shaft segment having a first end rotatably coupled to the reluctance motor; a second rotatable shaft segment, wherein a first end of the second rotatable shaftAttorney Docket No.000551-0001-WO1 segment is coupled to a second end of the first rotatable shaft segment; a flywheel, made of a composite material, rotatably coupled to a second end of the second rotatable shaft segment; a lifting plate, coupled to or integral with the flywheel, by which to cause electromagnetic levitation of the flywheel during operation of the system; a brake, coupled to or integral with the flywheel, to slow rotation of the flywheel; and a vacuum chamber containing the reluctance motor, the first and second rotatable shaft segments, the flywheel, the lifting plate, and the brake.

[0065] 12. The energy storage system as example 11 describes, wherein the lifting plate is disposed below the flywheel during operation of the system.

[0066] 13. The energy storage system as either of examples 11 or 12 describe, wherein the lifting plate is the brake.

[0067] 14. The energy storage system as any of examples 11-13 describe, further may include an electromagnetic bearing system coupled to the flywheel.

[0068] 15. The energy storage system as any of examples 11-14 describe, further may include a cooling system configured to apply a vacuum-rated coolant to the flywheel or to a shaft segment coupled to the flywheel.

[0069] 16. An energy storage system may include: a reluctance motor; a flywheel composed substantially of a composite material; shaft means for transmitting a rotational motion from the reluctance motor to the flywheel; lifting means for providing levitation of the flywheel during operation of the system; and a vacuum chamber containing the reluctance motor, the flywheel, the shaft means and the lifting means. The shaft means may be implemented in the form of, for example, a drive shaft or multiple drive shaft segments first coupled to each other, as described above. The lifting means may be implemented in the form of, for example, a ring- or disk-shaped metallic plate and one or more electromagnetic coils, which may be attached to or integral with the shaft means, as described above.

[0070] 17. The energy storage system as example 16 describes, wherein at least a portion of the lifting means may include brake means for slowing rotation of the flywheel. The brake means may be implemented in the form of, for example, a ring- or disk-shaped metallic plate, which may be attached to or integral with the shaft means, with a metallic container or housing to provide contact friction against the metallic plate when the brake means is engaged, as described above.Attorney Docket No.000551-0001-WO1

[0071] 18. The energy storage system as either of examples 16 or 17 describe, further may include brake means for slowing rotation of the flywheel.

[0072] 19. The energy storage system as any of examples 16-18 describe, wherein the vacuum chamber further contains the brake means.

[0073] 20. The energy storage system as any of examples 16-19 describe, further may include an electromagnetic bearing system coupled to the flywheel.

[0074] 21. The energy storage system as any of examples 16-20 describe, further may include cooling means for applying a vacuum-rated coolant to the flywheel or to a shaft segment coupled to the flywheel.

[0075] Any or all of the features and functions described above can be combined with each other, except to the extent it may be otherwise stated above or to the extent that any such implementations may be incompatible by virtue of their function or structure, as will be apparent to persons of ordinary skill in the art.

[0076] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

Claims

Attorney Docket No.000551-0001-WO1 CLAIMS What is claimed is:

1. An energy storage system comprising: a motor; a first rotatable shaft segment having a first end rotatably coupled to the motor; a second rotatable shaft segment, wherein a first end of the second rotatable shaft segment is coupled to a second end of the first rotatable shaft segment; a flywheel rotatably coupled to a second end of the second rotatable shaft segment; and a vacuum chamber containing the motor, the first and second rotatable shaft segments, and the flywheel.

2. The energy storage system of claim 1, wherein the motor is a reluctance motor.

3. The energy storage system of claim 1, further comprising a lifting plate, coupled to or integral with the flywheel, by which to cause electromagnetic levitation of the flywheel during operation of the system.

4. The energy storage system of claim 3, wherein the lifting plate is disposed below the flywheel during operation of the system.

5. The energy storage system of claim 3, wherein the lifting plate is configured for use as a brake to slow rotation of the flywheel.

6. The energy storage system of claim 1, further comprising a brake to slow rotation of the flywheel.

7. The energy storage system of claim 1, further comprising: a lifting plate, coupled to or integral with the flywheel, by which to cause electromagnetic levitation of the flywheel during operation of the system; anda brake to slow rotation of the flywheel.

8. The energy storage system of claim 7, wherein the vacuum chamber further contains the lifting plate and the brake.

9. The energy storage system of claim 1, further comprising an electromagnetic bearing system coupled to the flywheel.

10. The energy storage system of claim 1, further comprising a cooling system configured to apply a vacuum-rated coolant to the flywheel or to a shaft segment coupled to the flywheel.

11. An energy storage system comprising: a reluctance motor; a first rotatable shaft segment having a first end rotatably coupled to the reluctance motor; a second rotatable shaft segment, wherein a first end of the second rotatable shaft segment is coupled to a second end of the first rotatable shaft segment; a flywheel, made of a composite material, rotatably coupled to a second end of the second rotatable shaft segment; a lifting plate, coupled to or integral with the flywheel, by which to cause electromagnetic levitation of the flywheel during operation of the system; a brake, coupled to or integral with the flywheel, to slow rotation of the flywheel; and a vacuum chamber containing the reluctance motor, the first and second rotatable shaft segments, the flywheel, the lifting plate, and the brake.

12. The energy storage system of claim 11, wherein the lifting plate is disposed below the flywheel during operation of the system.

13. The energy storage system of claim 11, wherein the lifting plate is the brake.

14. The energy storage system of claim 11, further comprising an electromagnetic bearing system coupled to the flywheel.

15. The energy storage system of claim 11, further comprising a cooling system configured to apply a vacuum-rated coolant to the flywheel or to a shaft segment coupled to the flywheel.

16. An energy storage system comprising: a reluctance motor; a flywheel composed substantially of a composite material; shaft means for transmitting a rotational motion from the reluctance motor to the flywheel; lifting means for providing levitation of the flywheel during operation of the system; and a vacuum chamber containing the reluctance motor, the flywheel, the shaft means and the lifting means.

17. The energy storage system of claim 16, wherein at least a portion of the lifting means comprises brake means for slowing rotation of the flywheel.

18. The energy storage system of claim 16, further comprising brake means for slowing rotation of the flywheel.

19. The energy storage system of claim 18, wherein the vacuum chamber further contains the brake means.

20. The energy storage system of claim 16, further comprising an electromagnetic bearing system coupled to the flywheel.

21. The energy storage system of claim 16, further comprising cooling means for applying a vacuum-rated coolant to the flywheel or to a shaft segment coupled to the flywheel.

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