WO2024217546A1

WO2024217546A1 - A kinetic energy storage machine

Info

Publication number: WO2024217546A1
Application number: PCT/CN2024/088833
Authority: WO
Inventors: Loic BASTARD; Michael Pratt
Original assignee: Qnetic Corporation; Shanghai Qnetic Technology Co., Ltd.
Priority date: 2023-04-19
Filing date: 2024-04-19
Publication date: 2024-10-24
Also published as: WO2024216543A1

Abstract

The present disclosure relates to a kinetic energy storage machine (100) comprising: a rotor (200) having an axial extension in an axial direction (AD) and a radial extension in a radial direction (RD), a supporting structure (20a) for supporting the rotor (200), the rotor (200) being adapted to rotate around a rotor (200) axis of rotation (A), extending in the axial direction (AD), relative to the supporting structure (20a), and a bearing arrangement (10) comprising: at least one high-speed bearing (14), the kinetic energy storage machine (100) being adapted to assume a high-speed bearing suspension condition in which load transfer between the rotor (200) and the supporting structure (20a) is achieved via the high-speed bearing (14), thereby providing a high-speed bearing suspension with a first radial stiffness, and at least one low-speed bearing (12), the kinetic energy storage machine (100) being adapted to assume a low-speed bearing suspension condition in which load transfer between the rotor (200) and the supporting structure (20a) is achieved via the low-speed bearing (12), thereby providing a low-speed bearing suspension with a second radial stiffness, the second radial stiffness being higher than the first radial stiffness, the kinetic energy storage machine (100) further being adapted to assume a low-speed bearing release condition in which load transfer between the rotor (200) and the supporting structure (20a) via the low-speed bearing (12) is disabled, wherein the kinetic energy storage machine (100) is configured so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor (200) is above a low-speed bearing (12) shift rotational speed.

Description

A KINETIC ENERGY STORAGE MACHINE

Technical Field

Disclosed herein is a kinetic energy storage machine and methods of operating a kinetic energy storage machine.

Background

In mechanical applications, rotary machines consist of a rotating component, or rotor, that is supported by a stationary component, such as a stationary shaft or bearing, that supports and allows for the rotation of the rotating component about an axis or central point. Rotary machines can be used in many applications such as turbines, pumps, centrifuges, motors, and generators. Rotary machines can be used to convert energy from one form to another, such as converting mechanical energy to electrical energy, or vice versa.

Rotary machines can also be used to store energy in a form that can be used later. Energy storage is a process of capturing energy when it is abundant or inexpensive, and then releasing the energy when it is needed or when the cost of energy is high. Devices that accept energy, store energy, and release energy as needed are sometimes referred to as accumulators. In the case of rotary machines, rotational energy can be generated by accelerating a rotor up to a suitable rotational speed and then released from the rotor when desired, for instance, by converting the rotational energy into electrical energy in an electrical generator. Kinetic energy, for instance from a hydro reservoir, or electrical energy from another source can be used to accelerate the rotor thereby converting the inputted energy into rotational energy that is conserved by the rotational motion of the rotor.

Rotors used in kinetic energy storage can store large amounts of energy for long durations and can operate at very high rotational speeds. Sometimes also described as flywheels, rotors used in kinetic energy storage can also provide high power outputs for short durations and can also be used for smoothing out power output from wind turbines, providing backup power to critical facilities during power outages, and in grid stabilisation.

Summary

This summary is provided to introduce a selection of concepts that are further described below in the detailed description.

According to an aspect of this disclosure, there is provided a kinetic energy storage machine comprising: a rotor having an axial extension in an axial direction and a radial extension in a radial direction, a supporting structure for supporting the rotor, the rotor being adapted to rotate around a rotor axis of rotation, extending in the axial direction, relative to the supporting structure, and

a bearing arrangement comprising:

- at least one high-speed bearing, the kinetic energy storage machine being adapted to assume a high-speed bearing suspension condition in which load transfer between the rotor and the supporting structure is achieved via the high-speed bearing, thereby providing a high-speed bearing suspension with a first radial stiffness, and

- at least one low-speed bearing, the kinetic energy storage machine being adapted to assume a low-speed bearing suspension condition in which load transfer between the rotor and the supporting structure is achieved via the low-speed bearing, thereby providing a low-speed bearing suspension with a second radial stiffness, the second radial stiffness being higher than the first radial stiffness, the kinetic energy storage machine further being adapted to assume a low-speed bearing release condition in which load transfer between the rotor and the supporting structure via the low-speed bearing is disabled,

wherein the kinetic energy storage machine is configured so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor is above a low-speed bearing shift rotational speed.

A kinetic energy storage machine in accordance with the above implies that the rotor may be suspended with an appropriately low risk of encountering undesired dynamic phenomena, such as resonance phenomena or the like, when the rotational speed is increased above the low-speed bearing shift rotational speed. As will be elaborated on hereinbelow, the low-speed bearing shift rotational speed may for instance be a predetermined fixed speed or it may be determined on the basis of prevailing operating conditions of the kinetic energy storage machine such as the rotational speed and/or acceleration of the rotor.

Purely by way of example, the term “radial stiffness” may relate to a ratio between a force applied to the rotor in the radial direction and a resulting displacement of the rotor, relative to the supporting structure, in the radial direction.

Optionally, the kinetic energy storage machine is configured such that it can switch between the low-speed bearing suspension condition and the low-speed bearing release condition when the rotor is rotating relative to the supporting structure.

The above implies that the speed of the rotor can be increased in a straightforward manner.

Optionally, the kinetic energy storage machine comprises an actuation arrangement, the actuation arrangement being adapted to assume each one of a first condition and a second condition relative to the low-speed bearing such that when the actuation arrangement is in the first condition, the kinetic energy storage machine assumes the low-speed bearing release condition and when the actuation arrangement is in the second condition, the kinetic energy storage machine assumes the low-speed bearing suspension condition.

Optionally, a movement from the first condition to the second condition comprises a movement of at least a portion of the actuation arrangement in the axial direction.

The above implies that the actuation arrangement can be relatively compact in the radial direction which may be beneficial in various embodiments.

Optionally, a movement from the first condition to the second condition comprises a movement of at least a portion of the actuation arrangement in the radial direction.

The above implies that the actuation arrangement can be relatively compact in the axial direction which may be beneficial in various embodiments.

Optionally, the low-speed bearing comprises a first portion and a second portion, the kinetic energy storage machine being adapted to assume the low-speed bearing suspension condition by engaging the second portion of the low-speed bearing with the supporting structure and to assume the low-speed bearing release condition by disengaging the second portion of the low-speed bearing from the supporting structure, preferably the first portion of the low-speed bearing is fixed to the rotor.

The above implies that there may be sufficient space available between the low-speed bearing and the supporting structure, making it straightforward to achieve each one of the low-speed bearing suspension condition and the low-speed bearing release condition.

Optionally, the actuation arrangement comprises one or more engaging members, each one of which being movable between an engaged position and a release position, wherein in the engaged position, each one of the one or more engaging members contacts the second portion of the low-speed bearing such that the kinetic energy storage machine assumes the low-speed bearing suspension condition, and wherein in the release position, each one of the one or more engaging members separates, preferably at least in the radial direction, from the second portion of the low-speed bearing such that the at least one low-speed bearing assumes the low-speed bearing release condition.

The above implies a compact actuation engagement that nevertheless ensures that the low-speed bearing suspension condition is appropriate.

Optionally, the actuation arrangement further comprises a control element being rotatable relative to the supporting structure around a control element axis of rotation extending in the axial direction, the actuation arrangement being such that the one or more engaging members may be moved between the engaged position and the release position by rotation of the control element around the control element axis of rotation.

The above implies a space and cost efficient means for actuating the one or more engaging members.

Optionally, the control element encloses each one of the one or more engaging members such that each one of the one or more engaging members extends at least in the radial direction from the control element towards the second portion of the low-speed bearing at least partially in the radial direction, each one of the one or more engaging members being pivotable around a pivot axle being located between the control element and the second portion of the low-speed bearing in the radial direction.

The above implies a space and cost efficient means for actuating the one or more engaging members which may also be straightforward to assemble and/or supply.

Optionally, the actuation arrangement further comprises a control element actuator configured to actuate the control element to rotate around the control element axis of rotation, preferably the control element actuator and the control element are connected to each other via a worm gear.

Optionally, the kinetic energy storage machine is adapted to assume the low-speed bearing suspension condition by engaging a first portion of the low-speed bearing to the rotor, the kinetic energy storage machine further being adapted to assume the low-speed bearing release condition by disengaging the first portion of the low-speed bearing from the rotor.

As such, the low-speed bearing suspension and release conditions may be achieved by engaging or disengaging a first portion of the low-speed bearing to the rotor which implies a compact solution for changing the low-speed bearing condition.

Optionally, the rotor comprises at least one shaft, and wherein the first portion of the low-speed bearing is engageable with the at least one shaft.

Optionally, the actuation arrangement comprises a tapered sleeve, and wherein the rotor comprises a conical surface complementary to the tapered sleeve, and wherein the tapered sleeve is, in use, movable into contact with the conical surface to engage the first portion of the low-speed bearing with the rotor, and is movable out of contact with the conical surface to disengage the first portion of the low-speed bearing from the rotor.

For instance, the tapered sleeve is, in use, movable into contact with the conical surface to engage the first portion of the low-speed bearing with the rotor and is movable out of contact with the conical surface to disengage the first portion of the low-speed bearing from the rotor. The conical surface may be a truncated conical surface –for instance, formed by a shaft of the rotor tapering from a first shaft diameter to a second shaft diameter. The engagement means and complementary engagement means may be engageable with one another by way of dry or wet friction, for instance. In other low-speed bearing examples, the engagement means and the complementary engagement means may together form a dog clutch, centrifugal, or cone clutch. The engagement means may comprise a pawl or dog, for example.

Optionally, the kinetic energy storage machine comprises a tapered sleeve actuator, the tapered sleeve actuator being configured to, in use, move the tapered sleeve into and out of contact with the conical surface.

Optionally, the at least one high-speed bearing and the at least one low-speed bearing are spaced apart in the axial direction. The above implies an appropriate suspension which for instance may be adapted to accommodate bending moments or the like.

Optionally, the at least one high-speed bearing comprises an active magnetic bearing.

Optionally, the at least one high-speed bearing is configured to assume the high-speed bearing suspension condition when the rotor is in motion. This implies an appropriate operation of the kinetic energy storage machine since the machine need not be stopped in order to achieve the high-speed bearing suspension condition.

Optionally, the kinetic energy storage machine further is adapted to assume a high-speed bearing release condition in which load transfer between the rotor and the supporting structure via the high-speed bearing is disabled.

The above implies that the kinetic energy storage machine may be operated with an appropriately low risk of experiencing undesired dynamic phenomena, such as resonance phenomena.

Optionally, the kinetic energy storage machine is configured so as to assume the high-speed bearing release condition in response to detecting that a rotational speed of the rotor is equal to or below a high-speed bearing shift rotational speed.

The above implies that the kinetic energy storage machine may be operated with an appropriately low risk of experiencing undesired dynamic phenomena, such as resonance phenomena, for low speeds at which the high-speed bearing suspension with a first radial stiffness could potentially cause undesired dynamic phenomena.

Optionally, the kinetic energy storage machine further is adapted to switch between the high-speed bearing suspension condition and the high-speed bearing release condition, respectively, by respectively applying and removing a magnetic field to the rotor.

Optionally, the kinetic energy storage machine comprises a first a bearing arrangement and a second a bearing arrangement, preferably each one of the first bearing arrangement and the second bearing arrangement being a bearing arrangement in accordance with any one of the preceding claims, and wherein the first bearing arrangement and the second bearing arrangement are arranged at axially opposing ends of the rotor.

Optionally, the kinetic energy storage machine comprises a secondary bearing arrangement, wherein the bearing arrangement and the secondary bearing arrangement are arranged at axially opposing ends of the rotor.

Optionally, the secondary bearing arrangement comprises a magnetic bearing.

Optionally, the kinetic energy storage machine comprises an axial bearing adapted to take up a load from the rotor in the axial direction.

Optionally, the axial bearing comprises a permanent magnet bearing.

Optionally, the kinetic energy storage machine comprises a combination bearing adapted to take up a load from the rotor in the axial direction as well as in the radial direction.

Optionally, the rotor comprises at least one balancing disc.

Optionally, the rotor comprises a first balancing disc and a second balancing disc, and wherein the first balancing disc and the second balancing disc are arranged at axially opposing ends of the rotor.

Optionally, the kinetic energy storage machine comprises a damper to reduce vibrations in the rotor and/or kinetic energy storage machine.

Optionally, the rotor is oriented, in use, with the rotor axis of rotation arranged substantially vertically.

Optionally, the kinetic energy storage machine comprises a vacuum chamber to contain the rotor.

Optionally, the rotor is detachably coupled to an electrical machine, the electrical machine being selected from: an electrical motor, an electrical generator, or an electrical motor/generator.

Optionally, the kinetic energy storage machine comprises a coupling adapted to selectively couple the electrical machine to the rotor.

Optionally, the at least one low-speed bearing and the at least one high-speed bearing are spaced apart along an axial direction of the rotor.

Optionally, the kinetic energy storage machine is adapted such that when it assumes the low-speed bearing suspension condition, the rotor is operable without any critical speeds in a subcritical speed range below a transition speed, and wherein the transition speed is located within a supercritical speed range of the rotor when the kinetic energy storage machine assumes the high-speed bearing suspension condition and the low-speed bearing release condition.

Optionally, the kinetic energy storage machine is configured so as to assume the low-speed bearing suspension condition in response to detecting that the rotational speed of the rotor is equal to or below the low-speed bearing shift rotational speed.

Optionally, the kinetic energy storage machine is adapted to detect a current rotational speed of the rotor and to set the low-speed bearing shift rotational speed in response to the current rotational speed.

The above implies a versatility in the setting of the low-speed bearing shift rotational speed as will be exemplified below.

Optionally, the kinetic energy storage machine is adapted to:

- set the low-speed bearing shift rotational speed to a first low-speed bearing shift threshold speed in response determining that the current rotational speed is equal to or below a low-speed bearing transition speed, and

- set the low-speed bearing shift rotational speed to a second low-speed bearing shift threshold speed in response determining that the current rotational speed is above the low-speed bearing transition speed,

wherein the first low-speed bearing shift threshold speed is lower than the second low-speed bearing shift threshold speed.

For a low current rotational speed, the kinetic energy storage machine may assume the low-speed bearing suspension condition. As such, in such a condition, the low-speed bearing shift rotational speed may be used for a determining when, e.g. at which rotational speed being above the current rotational speed, the kinetic energy storage machine should assume the low-speed bearing release condition. Choosing a low-speed bearing shift rotational speed that is relatively low may result in an appropriately low risk that the kinetic energy storage machine assumes the low-speed bearing suspension condition for a rotational speed that is so high that undesired dynamic phenomena occurs.

On the other hand, for a high current rotational speed, the kinetic energy storage machine may assume the low-speed bearing release condition. As such, in such a condition, the low- speed bearing shift rotational speed may be used for determining when, e.g. at which rotational speed being below the current rotational speed, the kinetic energy storage machine should assume the low-speed bearing suspension condition. Choosing a low-speed bearing shift rotational speed that is relatively high may result in that the rotor is suspended in an appropriate manner, e.g. for a rotational speed just below a rotational speed associated with undesired dynamic phenomena.

Optionally, the kinetic energy storage machine is adapted to detect a current rotational acceleration of the rotor and to set the low-speed bearing shift rotational speed in response to the current rotational acceleration.

Optionally, the kinetic energy storage machine is adapted to:

- set the low-speed bearing shift rotational speed to a first low-speed bearing shift threshold speed in response to determining that the current rotational acceleration is positive, and

- set the low-speed bearing shift rotational speed to a second low-speed bearing shift threshold speed in response to determining that the current rotational acceleration is negative,

As such, the current rotational acceleration may be used for setting the low-speed bearing shift rotational speed. Thus, in response to determining that the rotor is accelerating, the low-speed bearing shift rotational speed may be used for determining when the kinetic energy storage machine should assume the low-speed bearing release condition and the above procedure may result in that the low-speed bearing shift rotational speed is relatively low which may result in an appropriately low risk that the kinetic energy storage machine assumes the low-speed bearing suspension condition for a rotational speed that is so high that undesired dynamic phenomena occurs.

On the other hand, in response to determining that the rotor is decelerating, the low-speed bearing shift rotational speed may be used for determining when the kinetic energy storage machine should assume the low-speed bearing suspension condition and the above procedure may result in that the low-speed bearing shift rotational speed is relatively high which may result in that the rotor is suspended in an appropriate manner, e.g. for a rotational speed just below a rotational speed associated with undesired dynamic phenomena.

Optionally, the kinetic energy storage machine is adapted to detect a current rotational speed of the rotor and to set the high-speed bearing shift rotational speed in response to the current rotational speed.

Optionally, the kinetic energy storage machine is adapted to:

- set the high-speed bearing shift rotational speed to a first high-speed bearing shift threshold speed in response to determining that the current rotational speed is equal to or below a high-speed bearing transition speed, and

- set the high-speed bearing shift rotational speed to a second high-speed bearing shift threshold speed in response to determining that the current rotational speed is above the high-speed bearing transition speed,

wherein the first high-speed bearing shift threshold speed is higher than the second high-speed bearing shift threshold speed.

Optionally, the kinetic energy storage machine is adapted to detect a current rotational acceleration of the rotor and to set the high-speed bearing shift rotational speed in response to the current rotational acceleration of the rotor.

Optionally, the kinetic energy storage machine is adapted to:

- set the high-speed bearing shift rotational speed to a first high-speed bearing shift threshold speed in response to determining that the current rotational acceleration is positive, and

- set the high-speed bearing shift rotational speed to a second high-speed bearing shift threshold speed in response to determining that the current rotational acceleration is negative,

Optionally, the kinetic energy storage machine comprises a controller adapted to control the kinetic energy storage machine to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor is above the rotational low-speed bearing shift rotational speed.

Purely by way of example, the controller may be adapted to receive information indicative of the current rotational speed and/or acceleration and to set the low-speed bearing shift rotational speed and/or the high-speed bearing shift rotational speed in response to the current rotational speed and/or acceleration, for instance in accordance with any one of the examples presented above.

Optionally, the second radial stiffness is at least 5 times higher than the first radial stiffness, preferably 10 times higher.

Optionally, the supporting structure forms part of, or constitutes, a housing at least partially enclosing the rotor.

A second aspect of the present disclosure relates to a method for operating a kinetic energy storage machine. The machine comprises:

a rotor having an axial extension in an axial direction and a radial extension in a radial direction,

a supporting structure for supporting the rotor, the rotor being adapted to rotate around a rotor axis of rotation, extending in the axial direction, relative to the supporting structure, and a bearing arrangement comprising:

the method comprising controlling the kinetic energy storage machine so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor is above a low-speed bearing shift rotational speed.

Optionally, the method comprises:

- accelerating, while the kinetic energy storage machine assumes the low-speed bearing suspension condition, the rotor to the low-speed bearing shift rotational speed; and

- controlling the kinetic energy storage machine so as to assume the low-speed bearing release condition once the rotor reaches or exceeds the low-speed bearing shift rotational speed.

Optionally, the kinetic energy storage machine further is adapted to assume a high-speed bearing release condition in which load transfer between the rotor and the supporting structure via the high-speed bearing is disabled, the method further comprising:

- controlling the kinetic energy storage machine so as to assume the high-speed bearing release condition in response to detecting that a rotational speed of the rotor is equal to or below a high-speed bearing shift rotational speed, and

- controlling the kinetic energy storage machine so as to assume the high-speed bearing suspension condition in response to detecting that a rotational speed of the rotor is above the high-speed bearing shift rotational speed.

Brief Description of the Drawings

Further features of the disclosure are described hereinafter, by way of non-limiting examples of the invention, with reference to and as illustrated in the accompanying drawings, in which:

Fig. 1 schematically illustrates an example of a kinetic energy storage machine, as described herein.

Figs. 2a and 2b are graphs that plot vibrational amplitude (radial displacement) of a rotor of a kinetic energy storage machine over a range of rotational speeds;

Fig. 3 schematically illustrates another example of a kinetic energy storage machine, as described herein;

Fig. 4 is a flow diagram of an example method of operating a kinetic energy storage machine;

Fig. 5 is a flow diagram of another example method of operating a kinetic energy storage machine;

Fig. 6 is a schematic diagram of an example controller of a kinetic energy storage machine, as described herein;

Fig. 7 is a perspective view of another example of a kinetic energy storage machine, as described herein;

Fig. 8 is an illustration of an energy storage facility that incorporates a plurality of the kinetic energy storage machines of Fig. 7;

Fig. 9 is another perspective view of the kinetic energy storage machine of Fig. 7;

Fig. 10 is a cross-sectional view of the kinetic energy storage machine of Fig. 7;

Fig. 11 is a cross-sectional perspective view of an upper portion of the kinetic energy storage machine of Fig. 7;

Fig. 12 is a cross-sectional perspective view of a lower portion of the kinetic energy storage machine of Fig. 7;

Fig. 13 is a cross-sectional perspective view of an upper bearing system of the kinetic energy storage machine of Fig. 7;

Fig. 14 is a is a perspective view of a lower bearing system of the kinetic energy storage machine of Fig. 7;

Fig. 15 is a cross-sectional perspective view of a low-speed bearing from the lower bearing system of Fig. 14;

Fig. 16 is a cross-sectional projection of a low-speed bearing from the upper bearing system of Fig. 13;

Fig. 17 is an exploded view of the low-speed bearing of Fig. 16;

Fig. 18 schematically illustrates an example of a contact sleeve from the low-speed bearing of Fig. 16; and

Fig. 19 schematically illustrates another example of a contact sleeve.

Fig. 20 schematically illustrates a portion of an embodiment of a kinetic energy storage machine.

Fig. 21 schematically illustrates a portion of the Fig. 20 embodiment in a first condition.

Fig. 22 schematically illustrates a portion of the Fig. 20 embodiment in a second condition.

Fig. 23 schematically illustrates the Fig. 20 embodiment in a second condition.

Fig. 24 illustrates a schematic perspective view of a portion an embodiment of a kinetic energy storage machine.

Fig. 25 illustrates a schematic perspective view of a portion an embodiment of a kinetic energy storage machine.

Detailed Description

The Applicant conceives that the bearing systems, rotors, and methods described herein may be implemented in any suitable rotational energy storage machine. Accordingly, in this description, operations, processes, methods, and apparatuses described with reference to the arrangement, restraint, and control of “rotors” are considered by the Applicant to be described with reference to, for example: rotary components, flywheels, drive shafts, and/or rotating armatures.

In this description, the term “rotor” shall be interpreted to mean any rotating part of a mechanical device, that is, comprising all the components that are fixed together to form a body that rotates around an axis of rotation at the same angular velocity. In this description, the terms “constrain” , or “constraint” , shall be interpreted to mean to hold or holding a rotor in substantial alignment with the desired rotational axis of the rotor including accommodating any vibrational deviations experienced by the rotor during operations yet remaining free to rotate about the rotational axis of the rotor.

In this description, the term “critical speed” shall be interpreted to mean the angular velocity that excites a natural frequency of a rotor assembly. That is, the combination of the rotor and the rotor’s constraints, for instance rotor mass and stiffness and constraints mass and stiffness, have a certain natural frequency that is excited by the critical speed and, as the rotor assembly accelerates or decelerates towards the critical speed, the rotor begins to resonate. Rotors may, depending on the combination of parameters, have more than one natural frequency. In this description, the term “subcritical” in the context of a rotor shall be interpreted as a rotor that is operating below a first critical speed. That is, the maximum speed of operation of the rotor is lower than the first critical speed with an appropriate separation margin of speed below the first critical speed. In this description, the term “supercritical” in the context of a rotor shall be interpreted as a rotor that is operating above a first critical speed. That is, the minimum speed of operation of the rotor is higher than the first critical speed with an appropriate separation margin of speed above the first critical speed.

In this description, the term “kinetic energy storage machine” shall be interpreted to include flywheel energy storage machines.

In certain applications, the arrangement of rotary machines can present design and control challenges so that the rotary machine can perform as desired. Such challenges can be magnified for large scale rotary machines such as those found in energy storage, electrical generation, or energy output applications. For instance, in certain kinetic energy storage applications, rotors can be operating at very high rotational speeds, with very large masses, and/or operate under heavy load, so the structures that support and permit the rotational motion of the rotors should be designed and constructed with care. In particular, the bearing components of the kinetic energy storage machines must accommodate the vibrations and resonance modes resulting from the motion of the rotor.

In the application considered by the Applicant –that of storing rotational energy or angular kinetic energy –the operational (i.e., storage) rotor speed and the amount of rotor mass are both usually set very high for a kinetic energy storage system to meet the desired efficiency levels. However, such parameters can present an operational challenge because accelerating a large mass to the desired rotational speed is difficult due to the vibrations and resonance modes experienced in the rotational machine as the rotor is accelerated to the desired rotational speed. The trade-offs involving in controlling the vibrations and resonance modes during operation of such a rotational machine can mean that the kinetic energy storage machine does not store energy very efficiently since significant energy can be lost within the structure of the kinetic energy storage machine. On the other hand, failing to control the vibrations and resonance modes is not viable either because the kinetic energy storage machine is then not robust enough to withstand the operational rigors for any worthwhile length of time.

Since rotational energy storage machines can be deployed anywhere and be effectively independent from the electricity grid because kinetic energy is stored in the machine instead of electrical energy, the use of rotary machines for energy storage is still desirable. However, due to the issues involved in controlling the vibrations and resonance modes of these types of machines means that they have not been deployed on any large scale.

The Applicant considers that the bearing systems, rotors, kinetic energy storage machines, and methods described herein will address these issues and, in particular, allow kinetic energy storage machines to be operated in an energy efficient manner whilst at the same time reducing the impact of vibrations and resonance modes on the operation those kinetic energy storage machines. Furthermore, the bearing systems, rotors, kinetic energy storage machines, and methods described herein will permit those machines to be used in kinetic energy storage on a large scale and in an economic manner.

Fig. 1 illustrates one example of a kinetic energy storage machine 100, as conceived by the Applicants. The Fig. 1 kinetic energy storage machine 100 comprises: a rotor 200 having an axial extension in an axial direction AD and a radial extension in a radial direction RD, a supporting structure 20a for supporting the rotor 200, the rotor being adapted to rotate R around a rotor axis of rotation A, extending in the axial direction AD, relative to the supporting structure 20a.

The supporting structure 20a can be any structure adapted to support the rotor 200. Purely by way of example and as exemplified in Fig. 1 and elaborated on further hereinbelow, the supporting structure 20a may form part of, or even be constituted by, a case 20a, see e.g. Fig. 11, at least partially enclosing at least a portion of the rotor 200.

The kinetic energy storage machine 100 also comprises a bearing arrangement 10. The bearing arrangement 10 comprises:

- at least one high-speed bearing 14, the kinetic energy storage machine 100 being adapted to assume a high-speed bearing suspension condition in which load transfer between the rotor 200 and the supporting structure 20a is achieved via the high-speed bearing 14, thereby providing a high-speed bearing suspension with a first radial stiffness, and

- at least one low-speed bearing 12, the kinetic energy storage machine 100 being adapted to assume a low-speed bearing suspension condition in which load transfer between the rotor 200 and the supporting structure 20a is achieved via the low-speed bearing 12, thereby providing a low-speed bearing suspension with a second radial stiffness, the second radial stiffness being higher than the first radial stiffness, the kinetic energy storage machine further being adapted to assume a low-speed bearing release condition in which load transfer between the rotor 200 and the supporting structure 20a via the low-speed bearing 12 is disabled.

It should be noted that the terms “high-speed bearing” and “low-speed bearing” only are used in an attempt to simplify the understanding of the present disclosure. However, it should be noted that throughout the present disclosure, the “high-speed bearing” may be referred to as a “first bearing” and the “low-speed bearing” may be referred to as a “second bearing” .

Moreover, the kinetic energy storage machine 100 is configured so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor 200 is above a low-speed bearing shift rotational speed.

Purely by way of example, the kinetic energy storage machine 100 may be configured such that it can switch between the low-speed bearing suspension condition and the low-speed bearing release condition when the rotor 200 is rotating relative to the supporting structure 20a.

Moreover, as schematically illustrated in Fig. 1 by way of a non-limiting example, the kinetic energy storage machine 100 may comprise an actuation arrangement 120. The actuation arrangement 120 may be adapted to assume each one of a first condition and a second condition relative to the low-speed bearing 14 such that when the actuation arrangement 120 is in the first condition, the kinetic energy storage machine 100 assumes the low-speed bearing release condition and when the actuation arrangement 120 is in the second condition, the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition.

Moreover, as indicated in Fig. 1, the kinetic energy storage machine 100 may comprise a controller 500 to control certain operations of the kinetic energy storage machine 100. For instance, the controller 500 may be adapted to control the kinetic energy storage machine 100 to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor 200 is above the low-speed bearing shift rotational speed.

Purely by way of example, the actuation arrangement 120 may be adapted to assume each one of the first condition and the second condition by a movement, wherein the movement from the first condition to the second condition comprises a movement of at least a portion of the actuation arrangement 120 in the axial direction AD. As another non-limiting example, the movement from the first condition to the second condition may comprise a movement of at least a portion of the actuation arrangement 120 in the radial direction. Non-limiting examples of each one of the above implementations of the actuation arrangement 120 will be presented hereinbelow.

In the Fig. 1 example, the kinetic energy storage machine 100 also comprises a secondary bearing arrangement 102, wherein the bearing arrangement 10 and the secondary bearing arrangement 102 are arranged at axially opposing ends of the rotor 200. The secondary bearing arrangement 102 may comprise a journal or rolling bearing, for example. In other examples, the kinetic energy storage machine 100 may comprise first and second bearing arrangements located at opposing ends of the rotor 10. In still other examples, for example where the rotor 200 is supported on a cantilever shaft (not shown) , the kinetic energy storage machine 100 may comprise only one bearing arrangement 10 or may comprise a bearing arrangement 10 and secondary bearing arrangement 102 both of which are located at the same end of the rotor 200. As a non-limiting example, the secondary bearing arrangement 102 may comprise a magnetic bearing. As another non-limiting example, the kinetic energy storage machine 102 may comprise a combination bearing (not shown) adapted to take up a load from the rotor 200 in the axial direction AD as well as in the radial direction RD.

As a non-limiting example, and as indicated in Fig. 1, the kinetic energy storage machine 100 may comprise an axial bearing 300 adapted to take up a load from the rotor 200 in the axial direction AD. Purely by way of example, the axial bearing 300 may comprise a permanent magnet bearing.

As intimated above, the bearing arrangement 10 comprises a low-speed bearing 12 and a high-speed bearing 14. Moreover, as have been indicated above, the kinetic energy storage machine 100 is adapted to assume each one of a low-speed bearing suspension condition and low-speed bearing release condition.

Purely by way of example, the kinetic energy storage machine 100 may be adapted to assume the low-speed bearing suspension condition by engaging a first portion 12’ of the low-speed bearing 12 to the rotor 200. As a non-limiting example, the first portion 12’ of the low-speed bearing 12 may comprise or even be constituted by an inner ring (not shown) of the low-speed bearing 12.

The kinetic energy storage machine 100 may further be adapted to assume the low-speed bearing release condition by disengaging the first portion 12’ of the low-speed bearing 12 from the rotor 200. Optionally, the rotor comprises at least one shaft 202a (see Fig. 3 for example) , and the first portion 12’ of the low-speed bearing 12 may be engageable with the at least one shaft 202a.

It should be noted that the kinetic energy storage machine 100 may be adapted to assume each one of a low-speed bearing suspension condition and low-speed bearing release condition in other ways than engaging/disengaging the first portion 12’ of the low-speed bearing 12 to the rotor 200. This will be elaborated on further hereinbelow.

As indicated above, in the Fig. 1 example, the first portion 12’ of the low-speed bearing 12 can be engaged and disengaged from the rotor 200 during operation of the kinetic energy storage machine 100. That is, the first portion 12’ of the low-speed bearing 12 can be engaged and disengaged from the rotor 10 at any suitable time, such as when the rotor 200 is not rotating, but particularly when the rotor 200 is in use and rotating about the axis A.

When the first portion 12’ of the low-speed bearing 12 is engaged with the rotor 200, the kinetic energy storage machine 100 exemplified in Fig. 1 assumes a low-speed bearing suspension condition in which load transfer between the rotor 200 and the supporting structure 20a is achieved via the low-speed bearing 12. To this end, the low-speed bearing 12 may comprise a second portion 12” engaged with the supporting structure 20a . The second portion 12” may be constantly or selectively engaged with the supporting structure 20a as will be elaborated on further below.

By way of example only, the kinetic energy storage machine 100 exemplified in Fig. 1 assumes the low-speed bearing suspension condition, enabling the rotor 200 to be operable, i.e. rotatable, without any critical speeds in a subcritical speed range that is below a low-speed bearing transition speed. The low-speed bearing transition speed may be lower than a first critical speed of the rotor when the low-speed bearing 12 is engaged with the rotor. As a non-limiting example, the low-speed bearing transition speed may be located within a supercritical speed range of the rotor 200 when the kinetic energy storage machine 100 exemplified in Fig. 1 assumes the low-speed bearing release condition and the kinetic energy storage machine 100 assumes the high-speed bearing suspension condition.

In some examples, the kinetic energy storage machine 100 may further be adapted to assume a high-speed bearing release condition in which load transfer between the rotor 200 and the supporting structure 20a via the high-speed bearing 14 is disabled. Purely by way of example, the kinetic energy storage machine 100 may be adapted to switch between the high-speed bearing release condition and the high-speed bearing suspension condition at any suitable time, such as when the rotor 200 is not rotating, or when the rotor 200 is in use and rotating about the axis A. In certain examples, the kinetic energy storage machine 100 may be adapted to assume the high-speed bearing release condition at all times during operational conditions, that is when the kinetic energy storage machine 100 is in situ and operating normally as opposed to periods of transport, installation or maintenance.

A kinetic energy storage machine according to the present disclosure is considered by the Applicant to enable that the kinetic energy storage machine may be operated without necessarily experiencing the resonance modes and vibrations that would be experienced by kinetic energy storage machines that do not form part of the present disclosure. For instance, a kinetic energy storage machine according to the present disclosure may be accelerated to a suitable operating rotational speed at which angular kinetic energy can be stored without experiencing the resonance modes and vibrations during acceleration or subsequent deceleration, or at least the resonance modes and vibrations may be reduced.

For a kinetic energy storage machine 100, when the rotor 200 is spooled up (or down) , the rotor 200 can pass through a critical speed at which the rotational speed (i.e., angular velocity) of the rotor 200 matches one of the rotor’s natural frequencies. A critical speed is a rotational speed of the rotor 200 that excites the natural frequency of the rotor. As the rotor approaches the critical speed, by accelerating or decelerating, the rotor 200 begins to resonate, which significantly increases the vibrations experienced by the kinetic energy storage machine 100. Operating the rotor 200 at, or near to, a rotor critical speed can be very damaging to the rotor 200 and/or the kinetic energy storage machine because the resulting vibrations can cause significant damage to the kinetic energy storage machine components.

The exact rotational speed that corresponds to a rotor critical speed can depend on several physical parameters of the kinetic energy storage machine 100. For instance, the stiffness of the rotor 200 and the rotor constraints and/or supports, the shaft stiffness of a rotor (where a shaft is present) , the mass of the rotor, the unbalance of the mass with respect to the axis of rotation of the rotor, and/or the amount of damping provided within the system can all influence the critical speed (s) of a particular system. To control the resonance modes and thus the damaging vibrations, the stiffness of the rotor suspension can be increased, which thereby increases the critical speed of the rotor. Generally speaking (i.e., up to certain limitations on increasing stiffness) , the stiffer the suspension, the higher the critical speed of the rotor.

For instance, the rotor 200 of the kinetic energy storage machine 100 may be provided with very stiff journal or roller bearings that stiffen the overall system thereby making a corresponding change to the natural frequency of the rotor 200. In this way, the rotor 200 can be spooled up to a higher velocity without necessarily having to pass through a rotational speed that matches a critical speed of the rotor; thus, periods of significant vibrations can be avoided during spooling up of the rotor. Regardless, the rotor velocity may still be practically limited since the critical speed of the rotor will eventually be reached.

In any case, stiffening the rotor suspension and increasing the critical speed of the rotor does not come cost free because of the ubiquitous energy losses experienced in all machines due to friction, deformation, magnetic and electrical losses, heat loss, and other inefficiencies. In the case of kinetic energy storage machines, increasing the stiffness of the rotor suspension can increase the energy losses incurred during operation of the rotor. Consequently, although increasing the stiffness of the rotor suspension is helpful in dealing with the rotor critical speed issues, the increased stiffness causes more energy losses to be incurred during operation of the kinetic energy storage machine. In fact, the energy losses incurred from stiffening the rotor suspension can be so significant in some applications that operating the kinetic energy storage machine becomes economically unviable. For kinetic energy storage systems, if energy losses incurred during rotation are too great then it becomes economically senseless to use a rotary machine to store kinetic energy. Reducing the stiffness of the suspension can again mitigate the energy losses incurred in the system, but then the critical speed issues again become a barrier to effective operation of the kinetic energy storage machine in that the lower rotor critical speeds can cause damage to, and reduce the operational life of, the kinetic energy storage machine.

The kinetic energy storage machines and methods described herein allow the rotor of a kinetic energy storage machine to be operated with a first critical speed that is suitable for more than one range of operational rotational speeds. That is the bearing systems, kinetic energy storage machines and methods described herein provide the rotor of a kinetic energy storage machine with a first critical speed that is appropriate for the rotational speed at which the rotor is currently rotating. For instance, the rotor has a higher first critical speed when the rotor is operating at a lower, or start up speed, and a lower first critical speed once the rotor has already accelerated past this vibrationally dangerous operational speed and where there are energy efficiencies to be gained by operating with the lower first critical speed. In this way, the rotor can be operated in a subcritical speed range at lower speed and then transition to a higher speed, using the bearing systems and methods described herein, to be operated in a supercritical speed range at the higher speed without ever having to pass through the first critical speed of the rotor that exists when the rotor has a constraint arrangement that is configured for higher operating speed.

This may be achieved by having a radially stiffer suspension to make the overall rotor system stiffer at the lower range rotational speed and a less radially stiff suspension once the dangerous critical speed (for the less stiff bearing) has already past when the rotor spools up. Transition between the differing suspensions may take place at a rotational speed that is located after the first critical speed for the less stiff bearing has been accelerated past.

For the bearings systems and kinetic energy storage machines described herein, as intimated above, the high-speed bearing suspension is associated with a first radial stiffness and the low-speed bearing suspension is associated second radial stiffness, wherein the second radial stiffness is higher than the first radial stiffness.

In this way, the rotor can operate at a preferred higher operating speed where greater energy efficiencies can be achieved due to the kinetic energy storage machine operating with a less stiff bearing that minimises energy losses at the higher speeds yet operate with a stiffer suspension that provides a higher first critical speed that is not reached as the rotor spools up to the higher operating speed, or has already been past as the rotor spools down from the higher operating speed. Thus, not only do the bearing systems, kinetic energy storage machines and methods described herein allow a kinetic energy storage machine to avoid dangerous critical speeds, but also allow for the rotor to operate in an energy efficient manner at the higher rotational speeds, which the Applicant considers to be particularly beneficial for kinetic energy storage machines.

Because the kinetic energy storage machine 100 is adapted to assume the low-speed bearing suspension condition and the low-speed bearing release condition as desired, the first critical speed of the rotor can be changed as desired so as to accommodate the change in rotational speed of the rotor. In this way, the rotor can operate at a speed where the rotor is suitably radially suspended enough by the low-speed bearing to allow acceleration of the rotor past what would be a first critical speed for the less stiff bearing without the kinetic energy storage machine being subjected to the vibrations that would otherwise occur at that speed. Since the kinetic energy storage machine 100 can assume the low-speed bearing release condition, the rotor can be accelerated up to the higher, energy efficient, speed where the high-speed bearing acts to radially suspend the rotor in an energy efficient manner. Similarly, to decelerate the rotor, the kinetic energy storage machine 100 can again assume the low-speed bearing suspension condition when the rotor decelerates to a speed where the first critical speed for the less stiff bearing would otherwise cause dangerous vibrations as the rotor is slowed or brought to a stop.

Figs. 2a and 2b are graphs that plot vibrational amplitude (radial displacement) of a rotor of a kinetic energy storage machine over a range of rotational speeds. Figs. 2a and 2b illustrate how the low-speed bearing 12 and high-speed bearing 14 of the bearing arrangement 10 (see e.g. Fig. 1 above) described herein work together to allow a suitable first critical speed to be selected for a particular operating speed range of the rotor. Fig. 2a illustrates how the low-speed bearing suspension condition and the low-speed bearing release condition of the kinetic energy storage machine 100 allow the rotor 200 to be switched between one first critical speed and another first critical speed as the rotor moves from one operational rotational speed range to another operational speed range.

Fig. 2b illustrates the resulting effective vibrational amplitude of the rotor over the whole range of rotational speeds and therefore illustrates how the rotor can be operated without the need for the rotor to operate at, or near, any rotor critical speeds. Figs. 2a and 2b schematically demonstrate the situation for a pure rigid rotor with a single suspension and are intended to assist with understanding the functionality of the disclosed bearing systems. It will be understood that there are many conceivable combinations of rotors and suspensions and that, depending on their specific parameters, there may be additional higher critical speeds for such systems beyond the first critical speeds shown in Fig. 2a.

In Fig. 2a, two speed-displacement curves 1, 2 are shown. Curve 1 shows the vibrational amplitude of the operating rotor when the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition across the whole range of rotational speeds of the rotor. Depending on the operational configuration of the bearing system, curve 1 may be representative of the vibrational amplitude when kinetic energy storage machine 100 only assumes the low-speed bearing suspension condition or may be representative of the vibrational amplitude when kinetic energy storage machine 100 assumes the low-speed bearing suspension condition as well as the high-speed bearing suspension condition.

When the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition, the rotor has a higher first critical speed C₁. Curve 2 shows the vibrational amplitude of the operating rotor when the kinetic energy storage machine 100 assumes only the high-speed bearing suspension condition (i.e. in combination with the low-speed bearing release condition) across the whole range of rotational speeds of the rotor. When the kinetic energy storage machine 100 assumes only the high-speed bearing suspension condition, the rotor has a lower first critical speed C₂. Due to the low-speed bearing suspension having a higher stiffness than the high-speed bearing, the higher first speed C₁ is higher than the lower first critical speed C₂.

Referring again to Fig. 2a, when the bearing system is put into operation and the rotor is operating in a first speed range S₁ (such as when the rotor is spooling up) , the rotor has the higher first critical speed C₁ and therefore avoids the having to operate with the vibrationally dangerous lower first critical speed C₂. Thus, as the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition the rotor is operated in the first speed range S₁, the rotor is rotatable with without any critical speeds and, operationally for the rotor, the speed range S₁ is a subcritical speed range.

In contrast, when the bearing system is put into operation and the rotor is operating in a second speed range S₂ where the kinetic energy storage machine 100 assumes the low-speed bearing release condition (such as when the rotor is accelerating up to maximum operating speed) , the rotor has the lower first critical speed C₂ and therefore is able to operate with a lower stiffness and thus minimised energy losses. As the kinetic energy storage machine 100 assumes the high-speed bearing suspension condition and the low-speed bearing release condition in the second speed range S₂, the rotor is operable in a supercritical speed range in speed range S₂. In the case of rotational energy storage machines, the second speed range S₂ may correspond to the normal working conditions or a storage rotational speed range within which the rotor is expected to stay for most of the machine’s working life.

The change in the rotor critical speed may result from allowing the kinetic energy storage machine 100 to assume the low-speed bearing suspension condition or the low-speed bearing release condition depending upon the rotational speed of the rotor.

As has been intimated above, the kinetic energy storage machine 100 of the present disclosure is configured to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor 200 is above a low-speed bearing shift rotational speed ω_LSB.

Moreover, though purely by way of example, the kinetic energy storage machine 100 may be configured so as to assume the low-speed bearing suspension condition in response to detecting that the rotational speed of the rotor is equal to or below the low-speed bearing shift rotational speed ω_LSB.

As may be realized from the above, the low-speed bearing shift rotational speed ω_LSB may be dependent on characteristics of the kinetic energy storage machine 100, such as dynamic characteristics of the rotor 200, e.g. natural frequencies or the like, possibly in combination with stiffness of the suspension (s) .

As such, in embodiments of the present disclosure, the low-speed bearing shift rotational speed ω_LSB may be a fixed value. This may apply for any embodiment of the present disclosure. As a non-limiting example, the low-speed bearing shift rotational speed ω_LSB may be set on the basis of the dynamic characteristics of the kinetic energy storage machine 100 in question.

However, it is also envisaged that the low-speed bearing shift rotational speed ω_LSB may be dependent on the current rotational speed of the rotor 200. This will be elaborated on below.

To this end, though purely by way of example, the kinetic energy storage machine 100 may be adapted to detect a current rotational speed ω of the rotor 200 and to set the low-speed bearing shift rotational speed ω_LSB in response to the current rotational speed ω.

By way of example only and with reference to Fig. 2a, the kinetic energy storage machine 100 may be adapted to:

- set the low-speed bearing shift rotational speed ω_LSB to a first low-speed bearing shift threshold speed ω_LSB, 1 in response to determining that the current rotational speed ωis equal to or below a low-speed bearing transition speed ω_LSB,_T, and

- set the low-speed bearing shift rotational speed ω_LSB to a second low-speed bearing shift threshold speed ω_LSB, 2 in response to determining that the current rotational speed ω is above the low-speed bearing transition speed ω_LSB, T,

wherein the first low-speed bearing shift threshold speed ω_LSB, 1 is lower than the second low-speed bearing shift threshold speed ω_LSB, 2.

Optionally, the kinetic energy storage machine may be adapted to detect a current rotational accelerationof the rotor and to set the low-speed bearing shift rotational speed ω_LSB in response to the current rotational acceleration.

Purely by way of example, the kinetic energy storage machine 100 may be adapted to:

- set the low-speed bearing shift rotational speed ω_LSB to a first low-speed bearing shift threshold speed ω_LSB, 1 in response to determining that the current rotational accelerationis positive, and

- set the low-speed bearing shift rotational speed ω_LSB to a second low-speed bearing shift threshold speed ω_LSB, 2 in response to determining that the current rotational accelerationis negative,

In a similar vein, the high-speed bearing shift rotational speed ω_HSB may be dependent on characteristics of the kinetic energy storage machine 100, such as dynamic characteristics of the rotor 200, possibly in combination with stiffness of the suspension (s) .

As such, in embodiments of the present disclosure, the high-speed bearing shift rotational speed ω_HSB may be a fixed value. This may apply for any embodiment of the present disclosure. As a non-limiting example, the high-speed bearing shift rotational speed ω_HSB may be set on the basis of the dynamic characteristics of the kinetic energy storage machine 100 in question.

Moreover, again purely by way of example, the low-speed bearing shift rotational speed ω_LSB and the high-speed bearing shift rotational speed ω_HSB may be equal.

In a similar vein as for the high-speed bearing shift rotational speed ω_HSB, the kinetic energy storage machine 100 may be adapted to detect a current rotational speed ω of the rotor and to set the high-speed bearing shift rotational speed ω_HSB in response to the current rotational speed ω.

As such, though purely by way of example, the kinetic energy storage machine 100 may be adapted to:

- set the high-speed bearing shift rotational speed ω_HSB to a first high-speed bearing shift threshold speed ω_HSB, 1 in response to determining that the current rotational speed ω is equal to or below a high-speed bearing transition speed ω_HSB, T, and

- set the high-speed bearing shift rotational speed ω_HSB to a second high-speed bearing shift threshold speed ω_HSB, 2 in response to determining that the current rotational speed ω is above the high-speed bearing transition speed ω_HSB, T,

wherein the first high-speed bearing shift threshold speed ω_HSB, 1 is higher than the second high-speed bearing shift threshold speed ω_HSB, 2.

As another non-limiting example, the kinetic energy storage machine 100 may be adapted to detect a current rotational accelerationof the rotor and to set the high-speed bearing shift rotational speed ω_HSB in response to the current rotational accelerationof the rotor.

- set the high-speed bearing shift rotational speed ω_HSB to a first high-speed bearing shift threshold speed ω_HSB, 1 in response to determining that the current rotational accelerationis positive, and

- set the high-speed bearing shift rotational speed ω_HSB to a second high-speed bearing shift threshold speed c in response to determining that the current rotational accelerationis negative,

wherein the first high-speed bearing shift threshold speed is higher ω_HSB, 1 than the second high-speed bearing shift threshold speed ω_HSB, 2.

By way of example only, the above setting of the low-speed bearing shift rotational speed and/or high-speed bearing shift rotational speed may be determined by the controller 500 presented above in relation to Fig. 1. As such, though purely by way of example, the controller 500 may be adapted to receive information indicative of the rotational speed and/or rotational acceleration of the rotor and to determine the low-speed bearing shift rotational speed and/or high-speed bearing shift rotational speed, for instance in accordance with any one of the above examples.

The above possible embodiments for determining the low-speed bearing shift rotational speed ω_LSB and the high-speed bearing shift rotational speed ω_HSB, respectively, will be presented by way of examples below. In the below examples, for the sake of brevity, the low-speed bearing transition speed ω_LSB, T and the high-speed bearing transition speed ω_LSB, T are equal and will be referred to as a transition speed ω_T. However, it is envisaged that in embodiments of the disclosure, the low-speed bearing transition speed ω_LSB, T and the high-speed bearing transition speed ω_LSB, T may be different.

In similar veins, in the below examples, the first high-speed bearing shift threshold speed ω_HSB, 1 and the second high-speed bearing shift threshold speed ω_HSB, 2 are equal and will be referred to as ω₁ and the second high-speed bearing shift threshold speed ω_HSB, 2 and the first high-speed bearing shift threshold speed ω_HSB, 1 are equal and will be referred to as ω₂. However, in embodiments of the disclosure, the first high-speed bearing shift threshold speed ω_HSB, 1 and the second high-speed bearing shift threshold speed ω_HSB, 2 may be different and/or the second high-speed bearing shift threshold speed ω_HSB, 2 and the first high-speed bearing shift threshold speed ω_HSB, 1 may be different.

For instance, when the rotor 200 is accelerated from a first speed range S₁ into a second speed range S₂, the kinetic energy storage machine assumes the low-speed bearing release condition at, or around, a transition point T on the two speed-displacement curves 1, 2. Thus, as the rotor 200 accelerates through the transition point T with a transition speed ω_T, the rotor 200 ceases to operate with the higher first critical speed C₁ and instead begins to operate with the lower first critical speed C₂. On the other hand, when the rotor is decelerated from speed range S₂ down to speed range S₁, the kinetic energy storage machine assumes the low-speed bearing suspension condition at, or around, the transition point T with the transition speed ω_T.

Thus, as the rotor decelerates through the transition point T, the rotor ceases to operate with the lower first critical speed C₂ and instead begins to operate with the higher first critical speed C₁. Where the kinetic energy storage machine is adapted to assume the high-speed bearing suspension condition as well as the high-speed bearing release condition during operation, and as the rotor 200 accelerates through the transition point T, the kinetic energy storage machine may assume the high-speed bearing suspension condition at a rotational speed below the transition point T, with transition speed ω_T, so that the high-speed bearing is already fully engaged with the rotor before the kinetic energy storage machine assumes the low-speed bearing release condition. This may assist with controlling the unbalances in the rotor as the kinetic energy storage machine assumes the low-speed bearing release condition because, in some examples, the constraining force applied by the high-speed bearing can be controlled to manage the rotational characteristics of the rotor as the transition is made. Similarly, as the rotor decelerates through the transition point T, with transition speed ω_T, the kinetic energy storage machine may assume the high-speed bearing suspension condition until the rotor reaches a rotational speed below the transition point T, with transition speed ω_T, so that the high-speed bearing is able to controllably assist with constraining the rotor until the kinetic energy storage machine fully assumes the high-speed bearing suspension condition.

Purely by way of example, the transition point T may coincide with a transition speed ω_T at which the kinetic energy storage machine switches between the low-speed bearing suspension condition and the low-speed bearing release condition. The transition speed may be located between the lower first critical speed C₂ and higher first critical speed C_1. As can be seen in Fig. 2a, the transition speed may be considered to cover a range of speeds, such as transition speed range S_T, or be a substantially single speed, such as a transition point speed ω_T. As indicated above, the transition speed ω_T may be different depending on whether the rotor 200 is accelerating or decelerating or may be the same irrespective of whether the rotor 200 is accelerating or decelerating. Referring again to Fig. 2a, it can be seen that, when the kinetic energy storage machine assumes the low-speed bearing suspension condition, the rotor 200 is operable in a subcritical speed range S₁ that is below the transition speed ω_T. Furthermore, the transition speed ω_T is located within a supercritical speed range of the rotor (i.e., above lower first critical speed C₂) when only when the kinetic energy storage machine assumes the high-speed bearing suspension condition. Accordingly, the speed range S₂ is also a supercritical speed range. The transition speed may be a lower speed than the higher first critical speed C₁ of the rotor when the low-speed bearing is engaged with the rotor 200.

Depending on the particular arrangement of the bearing system, the transition between the low-speed bearing suspension and release conditions of the kinetic energy storage machine, and therefore the transition between the rotor having different first critical speeds, may occur quickly over a small rotor speed change or may occur more slowly over a larger change in rotor speed. For example, as illustrated in Fig. 2a, the transition may occur relatively quickly at, or around, the transition point speed ω_T. In such cases, the low-speed bearing may be engaged with, or disengaged from, the rotor when the rotor reaches the transition point speed ω_T.

In other examples, the transition between the low-speed bearing suspension and release conditions of the kinetic energy storage machine may occur over the transition speed range S_T. For instance, when the rotor is accelerated from speed range S₁ into speed range S₂, the kinetic energy storage machine may begin assuming the low-speed bearing release condition when the rotor reaches, or exceeds, a disengagement rotational speed, which may be a first rotational speed ω₁, for instance. As intimated above, the first rotational speed ω₁ may also be referred to as the low-speed bearing shift threshold speed ω_LSB, 1.

In other examples, assuming the low-speed bearing release condition may coincide with the transition point speed ω_T. The kinetic energy storage machine may complete reaching the low-speed bearing release condition when the rotor reaches a suitable rotational speed, such as the transition point speed ω_T, a second rotational speed ω₂, or any other suitable rotational speed. On the other hand, when the rotor is decelerated from speed range S₂ down to speed range S₁, the kinetic energy storage machine may begin assuming the low-speed bearing suspension condition when the rotor reaches, or drops below, an engagement rotational speed, which may be the second rotational speed ω₂, for instance. In other examples, the engagement rotational speed may coincide with the transition point speed ω_T. The kinetic energy storage machine may complete assuming the low-speed bearing release condition when the rotor reduces to a suitable rotational speed, such as the transition point speed ω_T, the first rotational speed ω₁, or any other suitable rotational speed.

As can be seen from Fig. 2a, the transition speed range S_T may straddle the transition speed ω_T, for instance between the first rotational speed ω₁ and the second rotational speed ω₂. In other examples, the transition speed ω_T may form one end of the transition speed range S_T. The first rotational speed ω₁ and the second rotational speed ω₂ may be different in magnitude from one another with reference to the transition speed ω_T or may have the same magnitude as each another with reference to the transition speed ω_T.

As noted above, in the first speed range S₁, either the kinetic energy storage machine may switch between the low-speed bearing suspension and release conditions and/or between the high-speed bearing suspension and release conditions depending on the particular bearing arrangement or on the operational mode.

In some examples therefore, the kinetic energy storage machine may be adapted to switch between the high-speed bearing suspension and release conditions when the rotor is in motion. In examples where the kinetic energy storage machine only assumes the low-speed bearing suspension condition in the speed range S₁, the kinetic energy storage machine may also move through a high-speed bearing suspension/release transition that mirrors the transition of the low-speed bearing suspension and release conditions depending on whether the rotor is accelerating or decelerating through the transition point T. For instance, if the rotor is accelerated from speed range S₁ into speed range S₂ and the low-speed bearing release condition is assumed, then the high-speed bearing will need to perform the opposite action, which is to assume the high-speed bearing suspension condition at, or around, the transition point T.

In the case of rotor deceleration through the transition point T, the kinetic energy storage machine would instead assume the high-speed bearing release condition. The high-speed bearing suspension and release conditions may be changed when the rotor reaches the transition speed ω_T, for example. In other examples, the kinetic energy storage machine may begin assuming the high-speed bearing suspension condition when the rotor reaches, or exceeds, the first rotational speed ω₁ and begin assuming the high-speed bearing release condition when the rotor reaches, or drops below, the second rotational speed ω₂.

As mentioned above, in some examples, as the rotor accelerates, the kinetic energy storage machine may assume the high-speed bearing suspension condition at a rotational speed such that the high-speed bearing suspension condition is already assumed before the kinetic energy storage machine assumes the low-speed bearing release condition. Equally, as the rotor decelerates, the kinetic energy storage machine may assume the high-speed bearing suspension condition until such a rotational speed is reached where the kinetic energy storage machine fully assumes the low-speed bearing suspension condition. Accordingly, assuming the high-speed bearing suspension condition may begin to occur, or occur, below the transition speed. Similarly, assuming the high-speed bearing release condition may not begin to occur, or occur, until the rotor is below the transition speed. As also mentioned above, during acceleration, assuming the high-speed bearing suspension condition may occur after, for instance very quickly, the low-speed bearing release condition is assumed. Equally, during deceleration, the high-speed bearing release condition may occur, for instance very quickly, before the low-speed bearing suspension condition is assumed.

Fig. 2b shows a purely conceptual speed-displacement curve that results when the bearing systems described herein are put into operation on a pure rigid rotor, single suspension, rotary machine. As can be seen from Fig. 2b, there are no first critical speeds in the range of speeds where the low-speed bearing is engaged and, in the case of the pure rigid rotor, single suspension example illustrated here, there are effectively also no rotor critical speeds across the range of operational speeds of the rotor when only the high-speed bearing of the bearing system is engaged with the rotor.

In one example considered by the Applicant, for a kinetic energy storage machine, the operating speed ranges would be as follows. For a first speed range S₁, a rotor would operate between zero and approximately 1,000 RPM where the low-speed bearing is engaged and the rotor is subcritical. At a transition speed of around 1,000 RPM, the rotor passes through the transition point T and the low-speed bearing is disengaged over a suitable transition period. The high-speed bearing has been engaged before the low-speed bearing begins to disengage and any vibration amplitude may be controlled with the high-speed bearing –for instance, through the active magnetic functionality of the high-speed bearing. The transition period only for a short time as the rotor accelerates (or decelerates) through the transition point T. For a second speed range S₂, the rotor would operate between 1,000 and 8,000 RPM where the high-speed bearing is engaged and the rotor is supercritical. This speed range corresponds to the normal working conditions or a storage rotational speed range. The rotor is expected to stay at the storage rotational speed range for most of kinetic energy storage machine’s working life.

The Applicant has conceived a number of different possible arrangements for the bearing systems disclosed herein. In some examples, the high-speed bearing is an active magnetic bearing. For instance, the high-speed bearing magnetically act on a shaft of the rotor to radially retain the rotor during motion. As an active magnetic bearing, the high-speed bearing is a controllable bearing that exerts magnetic forces on the rotor. In particular, as an active magnetic bearing, the stiffness of the high-speed bearing can be controlled thereby permitting the rotor to operate in an energy efficient manner. In certain examples, the high-speed bearing is engageable and disengagable with the rotor by respectively applying and removing a magnetic field to the rotor. For instance, the high-speed bearing may comprise one or more electromagnets that can be selectively activated to generate an appropriate electromagnetic field that acts on the rotor to control the rotor’s position relative to the high-speed bearing. In some examples, the magnetic field may be applied and removed from a portion of the rotor. The application of the magnetic field may comprise varying the strength of the magnetic field applied to the rotor.

In a first set of embodiments, as will be presented hereinbelow with references to Figs. 3 –19, the kinetic energy storage machine 100 is adapted to assume the low-speed bearing suspension condition by engaging a first portion 12’ of the low-speed bearing 12 to the rotor and the kinetic energy storage machine 100 is further adapted to assume the low-speed bearing release condition by disengaging the first portion 12’ of the low-speed bearing from the rotor 12. However, as will be elaborated on below, it is envisaged that the other embodiments of the kinetic energy storage machine 100 may be adapted to assume the low-speed bearing suspension/release conditions in other ways.

Fig. 3 illustrates an example of a kinetic energy storage machine 100, as conceived by the Applicants. For the sake of brevity those features and structures that are the same or similar to those described with respect to Fig. 1 are referenced by the same numerals. The kinetic energy storage machine 100 comprises a rotor 200 that is rotatable R about an axis A. The kinetic energy storage machine 100 comprises first and second bearing arrangements 10 to constrain rotational motion of, or to suspend, the rotor 200 in a radial direction of the axis A. The first and second bearing arrangements 10 are arranged at opposing ends of the rotor 200. Each bearing arrangement 10 comprises a low-speed bearing 12 and a high-speed bearing 14. The rotor 200 comprises first 202a and second 202b shafts, each of which form one of the ends of the rotor 200. The first 202a and second 202b shafts are aligned with one another along the axis A.

A first portion 12’ of the low-speed bearing 12 of each bearing system 10 can be engaged with, and disengaged from, a respective one of the first 202a and second 202b shafts, in particular when the rotor 200 is rotating. Throughout the below description, a statement indicating that the low-speed bearing 12 can be engaged with a rotor or a shaft may be understood such that at least the first portion 12’ of the low-speed bearing 12 can be engaged with other entity. When the low-speed bearings 12 are engaged with the rotor 200, the low-speed bearings 12 constrain the rotor 200 in the radial direction and to be operable without any critical speeds in a subcritical speed range that is below a low-speed bearing transition speed. The low-speed bearing transition speed may be lower than a first critical speed of the rotor 200 when the low-speed bearings 12 are engaged with the rotor 200. The low-speed bearing transition speed is located within a supercritical speed range of the rotor 200 when the low-speed bearings 12 are disengaged and only the high-speed bearings 14 from each bearing system 10 are engaged with the rotor 200 so that the high-speed bearings 14 constrain the rotor 200 in the radial direction. It will be understood that each of the low-speed bearings 12 may, in some examples, be independently operable so that the engagement and disengagement of each low-speed bearing 12 may occur at a different rotational speed, albeit within a suitable margin of the low-speed bearing transition speed. In some cases, this may assist with controlling the rotor 200 as the rotor 200 accelerates or decelerates through the low-speed bearing transition speed.

In some examples, as with the low-speed bearings 12, the high-speed bearings 14 may be engaged and disengaged from the rotor 10 at any suitable time, such as when the rotor 200 is in motion about the axis A. In other examples, the high-speed bearings 14 may be continuously engaged with the rotor 200 during operational conditions.

To this end, as has been intimated above, the actuation arrangement 120 adapted to assume each one of a first condition and a second condition relative to the low-speed bearing such that when the actuation arrangement is in the first condition, the kinetic energy storage machine 100 assumes the low-speed bearing release condition and when the actuation arrangement is in the second condition, the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition. As also mentioned above, a movement from the first condition to the second condition comprises a movement of at least a portion of the actuation arrangement in the axial direction AD. In the Fig. 3 embodiment, the actuation arrangement 120 comprises an actuator 16 configured to move an engagement means, forming a portion of the actuation arrangement 120, of the low-speed bearing into and out of contact with the rotor 200.

The rotor 200 illustrated in Fig. 3 comprises two balancing discs –a first balancing disc 204a and a second balancing disc 204b. The first balancing disc 204a is fastened to the first 202a shaft and the second balancing disc 204b is fastened to the second shaft 202b. Thus, the first balancing disc 204a and the second balancing disc 204b are arranged at axially opposing ends of the rotor 200. Having two balancing discs arranged in this manner may make removing unbalances from the rotor easier and more accurate balancing of the rotor 200 to be performed.

The kinetic energy storage machine 100 comprises an axial bearing 300 to constrain rotational motion of the rotor 200 in an axial direction of the axis A. Put differently, the axial bearing 300 may be adapted to take up a load from the rotor 200 in the axial direction. In some examples, the kinetic energy storage machine 100 may comprise more than one axial bearing. In this example, the axial bearing 300 is arranged to constrain the first shaft 202a.

The kinetic energy storage machine 100 comprises a damper 400. The damper 400 comprises a magnetically susceptible damper disc 206 that is mounted on the first shaft 202a. The damper disc 402 may instead be mounted on the second shaft 202b. A magnetic absorber 402 is mounted on the kinetic energy storage machine 100 fixed structure and surrounds the damper disc 206. The magnetic absorber 402 acts magnetically on the damper disc 206 to dampen out vibrations of the rotor 200.

The rotor 200 is detachably couplable to an electrical machine 150 via a coupling 152. The electrical machine may be an electrical motor, an electrical generator, or an electrical motor/generator. The kinetic energy storage machine 100 may comprise a controller 500 to control certain operations of the kinetic energy storage machine 100. The controller 500 may be communicatively coupled to various components of the kinetic energy storage machine 100 to control the functionality thereof. For instance, the controller 500 may be, so as to send and receive control signals, communicatively coupled to one or more of: the bearings systems 10, the axial bearing 300, the damper 400, and/or the electrical machine 150. The controller may comprise one or more processors and/or one or more storage mediums comprising machine-readable instructions, as described herein.

Certain example methods and/or processes will now be described. The methods and/or processes may comprise methods and/or processes of operating a kinetic energy storage machine. The methods and/or processes may be performed, executed and/or implemented in any of the example kinetic energy storage machines described herein and/or illustrated in any of the figures.

A method 1000 of operating a kinetic energy storage machine, in which the kinetic energy storage machine comprises a rotor and a bearing system to provide radial constraint to the rotor, in which the bearing system comprises a low-speed bearing and a high-speed bearing, wherein the low-speed bearing is configured so that, when the low-speed bearing is engaged with the rotor, the rotor is rotatable below a disengagement rotational speed without any critical speeds in a subcritical speed range below the disengagement rotational speed, and wherein the disengagement rotational speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor, is shown in the flow diagram of Fig. 4. The method comprises: at block 1002, accelerating, while the low-speed bearing is engaged with the rotor to radially constrain the rotor, the rotor to a disengagement rotational speed; and, at block 1004, disengaging, with the high-speed bearing engaged with the rotor to radially constrain the rotor, the low-speed bearing from the rotor once the rotor reaches or exceeds the disengagement rotational speed.

As mentioned above, alternative methods may comprise engaging, for instance very quickly, the high-speed bearing with the rotor to radially constrain the rotor after the low-speed bearing is disengaged from the rotor.

In certain examples, the method may comprise accelerating, while the low-speed bearing is disengaged from the rotor, the rotor to a storage rotational speed. The storage rotational speed may be considered a desirable speed level where kinetic energy is stored for later retrieval from the rotor.

In certain examples, disengaging the low-speed bearing from the rotor comprises moving an engagement means from an engagement position, in which the engagement means is in contact with the rotor, to a disengaged position, in which the engagement means is separated from the rotor. The engagement means may be in contact with a complementary engagement means when in the engagement position. As has been intimated above, such engagement means may form part of the previously mentioned actuation arrangement 120.

In certain examples, the method may comprise engaging the high-speed bearing with the rotor before the rotor reaches the disengagement rotational speed.

In certain examples, the high-speed bearing comprises an active magnetic bearing and the method comprises activating the active magnetic bearing to apply a radially constraining magnetic field to the rotor.

In certain examples, the method comprises accelerating the rotor using an electrical motor or an electrical motor/generator coupled to the rotor.

In certain examples, the kinetic energy storage machine comprises a vacuum chamber to contain the rotor and the method comprises drawing a vacuum in the vacuum chamber before and/or during acceleration of the rotor.

A method 2000 of operating a kinetic energy storage machine, in which the kinetic energy storage machine comprises a rotor and a bearing system to provide radial constraint to the rotor, and in which the bearing system comprises a low-speed bearing and a high-speed bearing, wherein the low-speed bearing is configured so that, when the low-speed bearing is engaged with the rotor, the rotor is rotatable below an engagement rotational speed without any critical speeds in a subcritical speed range below the engagement rotational speed, and wherein the engagement rotational speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor, is shown in the flow diagram of Fig. 5. The method comprises: at block 2002, decelerating, while the high-speed bearing is engaged with the rotor to radially constrain the rotor, the rotor to an engagement rotational speed; and, at block 2004, engaging, with the high-speed bearing engaged with the rotor and once the rotor reaches or drops below the engagement rotational speed, the low-speed bearing with the rotor to radially constrain the rotor.

As mentioned above, alternative methods may comprise disengaging the high-speed bearing from the rotor before, for instance in a very short time, engaging the low-speed bearing to radially constrain the rotor.

In certain examples, the method may comprise decelerating, while the low-speed bearing is engaged with the rotor, the rotor to a stop.

In certain examples, engaging the low-speed bearing with the rotor may comprise moving an engagement means from a disengaged position, in which the engagement means is separated from the rotor, to an engagement position, in which the engagement means is in contact with the rotor. Again, such engagement means may form part of the previously mentioned actuation arrangement 120.

In certain examples, the method may comprise disengaging the high-speed bearing from the rotor once the rotor drops below the engagement rotational speed.

In certain examples, the high-speed bearing comprises an active magnetic bearing and the method comprises deactivating the active magnetic bearing to disapply a radially constraining magnetic field from the rotor.

In certain examples, the method comprises decelerating the rotor using an electrical motor, electrical generator, or an electrical motor/generator coupled to the rotor. For instance, the method may comprise powering an electrical motor/generator or electrical generator using the kinetic energy released from the rotor as the rotor decelerates.

In some examples, the methods described above and shown in Figs. 4 and 5 may be carried out using processing circuitry provided in a controller of any of the kinetic energy storage machines described herein. For instance, the methods described above and shown in Figs. 4 and 5 may be carried out using processing circuitry 502 provided in the controller 500 of the kinetic energy storage machine 100 described above. The processing circuitry of the controller can cause the blocks described above to be carried out by the kinetic energy storage machine.

As shown in Fig. 6, the controller 500 may comprise a bearing system module 510 to control the at least one bearing system 10. For instance, the bearing system module 510 may control both bearing systems 10 shown in Fig. 3. The controller 500 may also comprise: a axial bearing module 512 to control the axial bearing 310; a damper module 514 to control the damper 400; and an electrical machine module 516 to control the electrical machine 150. The controller 500 may comprise other modules. Any of the modules may be communicatively coupled to one or more sensors on the kinetic energy storage machine to monitor the status of the kinetic energy storage machine components.

The controller may comprise a storage module 504, for instance to store machine readable instructions that are executable by the processing circuitry and/or store data usable by the controller. For example, data relating to operational parameters such as low-speed bearing and/or high-speed bearing transition, engagement, and/or disengagement rotational speeds may be stored on the storage module 504. The controller 500 may comprise a communications interface 506 to communicatively couple the controller 500 to the rest of the kinetic energy storage machine.

Turning now to Fig. 7, which shows another example of a kinetic energy storage machine 100. Again, for the sake of brevity, those features and structures that are the same or similar to those described with respect to the previous figures are referenced by the same numerals. The rotor 200 of the kinetic energy storage machine 100 comprises an energy storage component 250, which allows the kinetic energy storage machine 100 to store kinetic energy due to the conservation of angular momentum when the rotor 200 is rotating. As with the kinetic energy storage machine 100 of Fig. 3, the kinetic energy storage machine 100 comprises first and second bearing systems 10 to constrain rotational motion of the rotor 200 in a radial direction of the axis A. The first and second bearing systems 10 are arranged at opposing ends of the rotor 200. Although hidden in Fig. 7, each bearing system 10 comprises a low-speed bearing 12 and a high-speed bearing 14.

The kinetic energy storage machine 100 of Fig. 7, when operational, is arranged with the rotor’s axis A of rotation oriented in a substantially vertical direction, which is aligned with the Z-axis of the X-Y-Z-axes co-ordinate system shown in Fig. 7. In the case of a rotational energy storage machine, this arrangement allows the mass, or static loads, of the device to be carried, in the axial direction, through the rotor. Although a rotational energy storage machine would function as well in another orientation, say with the axis A arranged horizontally, this would require the kinetic energy storage machine 100 to be constructed to deal with beam bending due to gravity loads. Since the rotor’s axis A is oriented in a substantially vertical direction, the first and second bearing systems 10 can be said to be upper 10a and lower 10b bearing systems.

The kinetic energy storage machine 100 of Fig. 7 comprises a single balancing disc 204 that is fastened to the rotor 200. The balancing disc is located at the bottom of the rotor 200, or underneath the energy storage component 250. The kinetic energy storage machine 100 comprises an axial bearing 300 to constrain rotational motion of the rotor 200 in an axial direction of the axis A. The axial bearing 300 is located at the top of the rotor 200, or above the energy storage component 250 in this example. Since the rotor’s axis A is oriented in a substantially vertical direction, the axial bearing 300 can be described as a suspension bearing that counters gravity in addition to constraining the rotor 200 against other axial displacement forces. The kinetic energy storage machine 100 comprises an electrical motor/generator 150. The electrical motor/generator 150 can be used to accelerate the rotor 200 –i.e., add kinetic energy to the rotor 200 –or decelerate the rotor 200 –i.e., draw kinetic energy out of the rotor 200.

Fig. 8 illustrates an application for the rotational energy storage machine of Fig. 7 as envisioned by the Applicants. A plurality of the kinetic energy storage machines 100 may be deployed in an energy management system 800 to store and manage the supply of electrical energy. The kinetic energy storage machines 100 may be deployed in an array 101of kinetic energy storage machines 100 that are each at least partially submerged beneath the ground in silos 180. A hood 182 or covering may be provided for each silo 180 to protect the kinetic energy storage machines 100 from environmental effects that may otherwise shorten the lifespan of the kinetic energy storage machines 100. The operational vertical orientation of the kinetic energy storage machines 100 may be beneficial as this allows the kinetic energy storage machines 100 to be easily installed in, maintained in, and removed from the silos 180. Furthermore, since the rotor 200 can have a significant mass in the energy storage component 250 that is spinning at very high speeds, submerging the kinetic energy storage machines 100 at least partially below ground level can help prevent damage or injury in the event of a malfunction. Furthermore, submerging the kinetic energy storage machines 100 at least partially below ground level can limit the visual impact of installing the array 101 in the natural environment. Other applications are also envisioned by the Applicant, such as the installation of a smaller number of kinetic energy storage machines 100 for specific energy storage applications. For instance, a building may have a single kinetic energy storage machine 100 to store and release energy depending on the electrical energy load on the building at any one time.

The energy management system 800 may comprise a number of energy generating systems, such as wind farms 810 or solar panels 820. Electrical energy generated by the energy generating systems can be fed into the array 101 of kinetic energy storage machines 100 through the electrical motor/generators 150 and turned into kinetic energy. This can be done when there are periods of excess electricity generation in comparison to the electricity demand. When needed, such as when there is excess electricity demand and not enough electricity generation capacity available, the kinetic energy stored in the array 101 can be drawn off through the electrical motor/generators 150 and turned into electrical energy, which can then be fed into the electricity grid. In this way, energy savings can be made since the energy generation process and energy demand are decoupled from one another since energy does not need to be generated at the same time as the energy is demanded. Furthermore, high-carbon output energy generation methods may not be required at times of higher electrical energy demand or when green electricity systems, such as wind farms, are not operational. Thus, the emission of polluting greenhouse gases can be reduced.

Fig. 9 illustrates one example of how the kinetic energy storage machine 100 of Fig. 7 may be installed on site in an energy storage facility, such as the energy management system 800. The kinetic energy storage machine 100 may be mounted in a housing 160 that supports the structures, such as the bearing systems 10 and axial bearing 300, that constrain the rotor 200. In the example shown in Fig. 9, the housing 160 comprises an elongate cylindrical mid-case 164 that sits atop a lower case 168 and that is capped by an upper case 166. The lower case 168 supports and retains the lower bearing system 10. The upper case 166 supports and retains the upper bearing system 10 and the suspension bearing 300. The upper case 166 also supports an electrical machine mount 154 that supports and retains the electrical motor/generator 150. The housing may be constructed from steel or other suitable materials.

As shown by Fig. 9, the housing 160 is installable in a silo 180, which, as described above, can allow the machine to be installed in a particularly operationally safe manner. The silo hood 182 is not shown in Fig. 9. The housing 160 holding the rotor 200 can conveniently be craned into and out of the silo 180, for example, in a fully assembled state. The housing 160 may be positionally retained in the silo 180 using mounts 170, for example. The mounts 170 may comprise dampers, such as rubber bushings for example, that can absorb vibrations transmitted from the housing 160. The silo 180 may be constructed from concrete or another suitable materials.

Fig. 10 is a cross-section through the axis A of rotation of the kinetic energy storage machine 100 of Fig. 7 but including the housing 160 and silo 180 as described above. The silo hood 182 is not shown in Fig. 10. The vertical direction in Fig. 10 is indicated by the Z-axis. Fig. 10 illustrates how the silo 180 defines a cavity 184 within which the housing 160 may be accommodated. The silo 180 may comprise a mounting pad 186, such as a concrete pad on which the lower case 168 may be mounted.

The housing 160 may define a vacuum chamber 162 within which the rotor 200 is operable. A housing seal 165 may therefore be provided between the mid-case 164 and the upper case 166 to seal the vacuum chamber 162 once the rotor 200 and any supporting structures, such as the lower bearing system 10 have been installed within housing 160. The mid-case 164 and the lower case 168 may be joined together, such as by welding, or may also be provided with another seal, to seal therebetween. A vacuum pump (not shown) may be provided to draw a vacuum in the vacuum chamber 162 when the rotor 200 is in use. It will be understood that other suitable housing structures may be provided.

The upper case 166 comprises an upper mount 167 that retains and supports the suspension bearing 300 and the upper bearing system 10a via mounting to the suspension bearing 300. The upper mount 167 also supports the electrical machine mount 154. The lower case 168 also comprises a lower bearing mount 169 that retains and supports the lower bearing system 10b. The housing 160 cases, upper mount 167, lower bearing mount 169, and the electrical machine mount 154 all work together to provide the necessary rigidity to support and retain the bearing systems and suspension bearing, and therefore the rotor 200, in place.

Fig. 10 also illustrates the rotor 200 structure of the kinetic energy storage machine 100. The rotor 200 comprises a first 202a and second 202b shafts, each of which form one of the ends of the rotor 200. The first 202a and second 202b are aligned with one another along the axis A. Since the rotor’s axis A is oriented in a substantially vertical direction, the first 202a and second 202b shafts can be said to be upper and lower shafts. The balancing disc 204 is fastened to the lower shaft 202b.

Figs. 11 and 12 are cross-sectional perspective views of portions of the kinetic energy storage machine 100 shown in Figs. 7, 9 and 10. Fig. 11 is a view of the upper sub-assemblies and shows a cross-section through the suspension bearing 300, the upper bearing system 10a, and the upper shaft 202a. The coupling 152 for attachment to the electrical motor/generator 150 is shown attached to the end of the upper shaft 202a. Fig. 12 is a view of the lower sub-assemblies and shows a cross-section through the lower bearing system 10b and the lower shaft 202b. The rotor energy storage component 250, the housing 160, and the electrical machine mount 154 are not shown in Figs. 11 and 12.

With reference to Fig. 11, the upper shaft 202a is formed of two parts: a support shaft 202a-1 and a guidance shaft 202a-2. The support shaft 202a-1 comprises a flange 210a through which the energy storage component 250 is mountable to the upper shaft 202a. For instance, the energy storage component 250 may be bolted to the support shaft 202a-1 through the flange 210a. The guidance shaft 202a-2 extends along the axis A of rotation and is constrained in the radial direction by the upper bearing system 10a, which is fixed to the stationary housing 160 support structure of the kinetic energy storage machine 100. The support shaft 202a-1 and the guidance shaft 202a-2 are both connected to, and together sandwich (in the axial direction) , a rotatable bearing platen 220 of the rotor 200 so that the support shaft 202a-1 and the guidance shaft 202a-2 are attached to one another and are aligned with one another. The rotatable bearing platen 220, which forms a part of the suspension bearing 300, is therefore attached to the rotor 200 and rotates with the operating rotor 200.

The suspension bearing 300 also comprises a fixed bearing platen 302 that, in this example, is attached to the to the housing 160. The fixed bearing platen 302 could instead be attached to a separate casing before being attached to the housing 160 or other supporting structure of the kinetic energy storage machine 100. The suspension bearing 300 comprises a case 310 that covers the rotatable bearing platen 220 and the fixed bearing platen 302, and that supports the upper bearing system 10a. The case 310 may be configured to seal against the housing 160 so that a vacuum can be maintained in the vacuum chamber 162. In this example, the case 310 comprises a number of apertures 312 through which the rotatable bearing platen 220 is accessible when the rotor 200 is installed. In this example, there are three, equally spaced, apertures 312 arranged in the radially upper edge of the case 310. In one example, the rotatable bearing platen 220 can be used to correct any unbalances in the rotor 200 by altering the mass and/or mass distribution of the rotatable bearing platen 220 through one or more of the apertures 312. For instance, the balancing masses may be added at certain locations on the rotatable bearing platen 220 to correct any unbalances in the rotor 200. In this way, an upper balancing disc located above the energy storage component 250 can be, such as in the example illustrated in Figs. 7, 9 and 10, excluded from the rotor 200 construction.

The rotatable bearing platen 220 and the fixed bearing platen 302 both comprise magnetic elements 222, 304. The magnetic elements 222, 304 are configured so that rotatable bearing platen 220 and the fixed bearing platen 302 magnetically repel one another thereby maintaining a vertical separation between the two platens 220, 302 of the suspension bearing 300. The magnetic elements 222, 304 may be electromagnets or permanent magnets depending on the configuration. In the example shown in Fig. 11, the magnetic elements 222, 304 are arranged in concentric rings on their respective platens 220, 302. The upper bearing system 10a comprises a case 20a that retains and supports the low-speed 12 and high-speed 14 bearings. The case 20a is fixed to the case 310 of the suspension bearing 300.

With reference to Fig. 12, the lower shaft 202b is a rotationally symmetrical single part but has two portions: a support portion 202b-1 and a guidance portion 202b-2. The support portion 202b-1 comprises a flange 210b through which the energy storage mass 250 is mountable to the lower shaft 202b. Again, the energy storage component 250 may be bolted to the support portion 202b-1 through the flange 210b.

The shaft 202b extends along the axis A of rotation to reach the guidance portion 202b-2 at which the shaft 202b is constrained or suspended in the radial direction by the lower bearing system 10b, which is fixed to the stationary housing 160 support structure of the kinetic energy storage machine 100. The lower bearing system 10b comprises a case 20b that retains and supports the low-speed 12 and high-speed 14 bearings. The case 20a is fixed to the housing 160.

Fig. 13 is a cross-sectional perspective view of the upper bearing system 10a and shows a cross-section through the low-speed bearing 12 and the high-speed bearing 14 of the upper bearing system 10a. The guidance shaft 202a-2 is not shown in Fig. 13. Case 20a comprises two sub-cases 22a, 24a. Low-speed bearing case 22a encases and supports the low-speed bearing 12. The low-speed bearing case 22a is attached to the high-speed bearing case 24a, which encases and supports the high-speed bearing 14. The high-speed bearing case 24a is mounted on top of the case 310 of the suspension bearing 300.

The high-speed bearing 14 in this example is an active magnetic bearing (AMB) . The active magnetic bearing comprises one or more magnetic field generators 30 that generate a magnetic field that is applied to the guidance shaft 202a-2. The generated magnetic field is actively adjusted to keep the guidance shaft 202a-2 in the correct position, i.e., aligned with the rotational axis A. The guidance shaft 202a-2 may have at least a portion thereof that is ferrous in nature and located adjacent to the active magnetic bearing, in use.

The high-speed bearing case 24a also supports and retains a damper 400. As noted above with respect to Fig. 3, a damper may be located elsewhere along the rotor 200 axial direction according to the desired construction of the kinetic energy storage machine 100. In this example, the damper has been encased with the high-speed bearing 14 in the high-speed bearing case 24a. The damper 400 comprises a damper disc 206 (shown in Fig. 13) that is fastened to the guidance shaft 202a-2. A magnetic absorber 402 is mounted on the high-speed bearing case 24a and surrounds the damper disc 206 to act magnetically on the damper disc 206 to dampen out vibrations.

Although not illustrated in Fig. 13, the high-speed bearing case 24a also supports and retains various electrical connections that connect the active magnetic bearing and magnetic absorber 402 to the controller and provide the necessary power to operate them and thereby control the rotor 200. The high-speed bearing case 24a may also support and retain one or more sensors that provide feedback signals, via electrical connections, to the controller concerning the status of the active magnetic bearing and magnetic absorber 402, and positional data in respect of the axial and/or radial position of the rotor 200.

In this example, the low-speed bearing 12 comprises an actuation arrangement 120 comprising a contact sleeve that is movable in the axial direction of the rotor 200 to engage with the guidance shaft 202a-2. The contact sleeve is mounted to a driven drive sleeve by way of a radial stiffness control element.

In the example illustrated in Fig. 13, the contact sleeve of the actuation arrangement 120 is a tapered sleeve 50 the taper of which defines a conical surface 52 that, on engagement with the rotor 200, makes contact with a complementary conical surface on the guidance shaft 202a-2 to provide radial constraint to the guidance shaft 202a-2. In the example shown, the conical surface 52 is on the radially inward surface of the tapered sleeve 50. In this example, the conical surface 52 tapers towards the rotational axis A in a direction towards the end of the guidance shaft 202a-2, and therefore the shaft 202a. That is, the tapered sleeve 50 narrows along the axis in a direction away from the centre of the rotor 200. The complementary conical surface is defined by the guidance shaft 202a-2 tapering from a first shaft diameter to a second shaft diameter. The complementary conical surfaces may be described as truncated conical surfaces. The tapered sleeve 50 may taper in the opposite direction in other examples.

The actuation arrangement 120 also comprises drive sleeve 54 that is rotationally fixed relative to the low-speed bearing case 22a and other supporting structures of the kinetic energy storage machine 100 but can move in the axial direction of the rotor 200 with the other components of the actuation arrangement 120. The tapered sleeve 50 is mounted to the drive sleeve 54, by radial stiffness control element 64, as described further below with respect to Figs. 15 to 17. The tapered sleeve 50 is substantially axially and substantially rotationally fixed relative to the drive sleeve 54 so as to move, with the drive sleeve 54, in the axial direction of the rotor 200 when the drive sleeve 54 is driven along the axial direction. The drive sleeve 54 is arranged radially outward of the tapered sleeve 50. As explained in more detail below, the drive sleeve 54 is driven by the actuator 16 to engage the actuation arrangement 120 with the rotor 200.

In this example, the low-speed bearing 12 comprises an engagement support to brace the actuation arrangement 120 when the actuation arrangement 120 engages the rotor. The engagement support helps ensure the actuation arrangement 120 properly engages with the rotor and helps ensure that the forces involved in radially constraining the rotor are directed through the appropriate structures of the kinetic energy storage machine 100.

In this example, the engagement support comprises a fixed sleeve 56. The fixed sleeve 56 is substantially rotationally fixed and substantially axially fixed relative to the low-speed bearing case 22a and other supporting structures of the kinetic energy storage machine 100. As explained further below, the fixed sleeve 56 does have some limited flexibility in certain directions. The fixed sleeve 56 defines a fixed conical surface 58 that can make contact with a complementary conical surface on the drive sleeve 54. In one example, as the actuation arrangement 120 is moved into contact with the rotor 200, the fixed conical surface 58 is arranged to contact the complementary conical surface on the drive sleeve 54 before the conical surface 52 of the tapered sleeve 50 makes contact with the guidance shaft 202a-2. This ensures that the radially constraining forces can be directed through the low-speed bearing case 22a as the tapered sleeve 50 makes contact with the guidance shaft 202a-2 rather than passing damaging radially constraining forces through the actuator 16 components. In other examples, the fixed conical surface 58 may be arranged to contact the complementary conical surface on the drive sleeve 54 at substantially the same time as the actuation arrangement 120 makes contact with the rotor 200. The fixed conical surface 58 is arranged radially outward of the drive sleeve 54. As can be seen from Fig. 13, the fixed conical surface 58 tapers in the opposite direction to the conical surface 52 of the tapered sleeve 50. The fixed sleeve 56 is attached to the low-speed bearing case 22a by a cage 60 that is an axial stiffness control element. The cage 60 is an annulus that surrounds, and is fixed to, the fixed sleeve 56 and is attached to the low-speed bearing case 22a. The fixed sleeve 56 is otherwise not connected to the low-speed bearing case 22a. In other examples, the fixed sleeve 56 may have additional connections with the low-speed bearing case 22a.

When the actuation arrangement 120 assumes a condition making contact with the rotor 200 via the conical surface 52 of the tapered sleeve 50, the fixed conical surface 58 also makes contact with the complementary conical surface on the drive sleeve 54. This action wedges the tapered sleeve 50 and drive sleeve 54 between the guidance shaft 202a-2 and the fixed sleeve 56 thereby radially constraining the rotor 200 to rotate about the rotational axis A. The necessary constraint forces are transmitted through the cage 60 and sleeves 50, 54, 56 to the guidance shaft 202a-2. In this way, the reactive constraint forces are directed to the low-speed bearing case 22a and other supporting structures of the kinetic energy storage machine 100 and the forces exerted on the actuator 16 mechanism, to which the drive sleeve 54 is connected, are minimised.

Although not illustrated in Fig. 13, the low-speed bearing case 22a also supports and retains various electrical connections that connect the low-speed bearing 12 components to the controller and provide the necessary power to operate them and thereby control the rotor 200. For instance, the actuator motor 17 of Fig. 14 below may be powered and controlled via such electrical connections. The low-speed bearing case 22a may also support and retain one or more sensors that provide feedback signals, via electrical connections, to the controller concerning the status of the low-speed bearing components and positional data in respect of the axial and/or radial position of the rotor 200.

Fig. 14 is a is a perspective view of the lower bearing system 10b. As with Fig. 14, the shaft 202b is not shown in Fig. 13. Case 20b comprises two sub-cases 22b, 24b. Low-speed bearing case 22b encases and supports the low-speed bearing 12. The high-speed bearing case 24b, which encases and supports the high-speed bearing 14, is attached to the low-speed bearing case 22b. The low-speed bearing case 22b is mounted to the lower case 168 of the housing 160. The low-speed bearing case 22b and the high-speed bearing case 24b are substantially the same as the low-speed bearing case 24a and high-speed bearing case 24a excepting that the axial positions are reversed. In the case of the lower bearing system 10b, the low-speed bearing 12 is located below the high-speed bearing 14 instead of above the low-speed bearing in the upper bearing system 10a. The high-speed bearing case 24b of the lower bearing system 10b also does not accommodate a damper.

For the lower bearing system 10b, the high-speed bearing 14 is also an active magnetic bearing that comprises one or more magnetic field generators 30. The magnetic field generators 30 generate a magnetic field that is applied to the guidance portion 202b-2 of lower shaft 202b. In this example of the kinetic energy storage machine 100, the low-speed bearing 10 also functions in the same manner as described above with respect to the upper bearing system 10a. As with the upper bearing system 10a, the first 22b and second 24b bearing cases also support and retain various electrical connections that connect the low-speed 12 and high-speed 14 bearing components to the controller and provide the necessary power to operate them and thereby control the rotor 200. The low-speed 22b and high-speed 24b bearing cases may also support and retain one or more sensors that provide feedback signals, via electrical connections, to the controller concerning the status of the low-speed 12 and/or high-speed 14 bearing components and positional data in respect of the axial and/or radial position of the rotor 200.

As Fig. 14 also shows bearing systems 10a, 10b each one of which being associated with an actuation arrangement 120 which in turn comprises an actuator 16 to activate engagement means. The actuator 16 is mounted on the low-speed bearing case 22b. The actuator 16 comprises an actuator motor 17 to provide motive power to the actuator 16.

The lower bearing system 10b also comprises a mounting plate 26. The mounting plate 26 is fixed between the first 22b and second 24b bearing cases, though may be located elsewhere. Through the mounting plate 26, the lower bearing system 10b can be mounted to the lower case 168 of the housing 160.

Fig. 15 is a cross-sectional perspective view of the low-speed bearing 12 from the lower bearing system 10b. Fig. 16 is a cross-sectional projection of the low-speed bearing 12 from the upper bearing system 10a. Figs. 15 and 16 illustrate how the engagement means and the actuator 16 function together to move the engagement means into and out of contact with the rotor 200, i.e., into an engagement position and out to a disengaged position.

With reference to Fig. 15, the actuator comprises a worm 70, or worm screw, that is rotatable W by the motor 17 of the actuator. The worm 70 is meshed with a worm gear of a drive nut 72 that, in this example, is rotatable about the axis A of rotation. Activating the worm 70 turns S the drive nut 72 about the axis A. The drive nut 72 is substantially fixed in the axial direction relative to the low-speed bearing case 22. That is, the drive nut 72 is guided and supported to only be able to rotate about an axis. With additional reference to Fig. 16, the drive nut 72 is threaded 73 to the drive sleeve 54. The drive nut 72 and the drive sleeve 54 together form a translation screw. Turning S the drive nut 72 causes the drive sleeve 54, which is rotationally (relative to axis A) fixed relative to the low-speed bearing case 22, to travel and thereby move in the axial direction. Since they are threaded together in this example, the drive nut 72 and the drive sleeve 54 are concentrically arranged about axis A.

To engage the engagement means with the rotor 200, the worm is rotated W in one direction which also causes the drive nut 72 to turn S about the axis A. As the drive nut 72 spins, the drive sleeve 54 is driven in one direction along the axis A thereby causing the tapered sleeve 50 to also move D along the axis A in the same direction until the conical surface 52 makes contact with the rotor 200. The drive sleeve 54 also makes contact, in this example prior to the tapered sleeve 50 contacts the rotor, with the fixed conical surface 58 of the fixed sleeve 56 thereby securely constraining the rotor 200 through the shaft 202a, 202b.

Fig. 17 is an exploded view of the low-speed bearing of Fig. 16 that shows the engagement means and the support means. As can be seen in Fig. 17, the tapered sleeve 50 and the drive sleeve 54 concentrically sandwich a radial stiffness control element 64. The radial stiffness control element 64 is fastened, for instance by any suitable fasteners, such as the machine screws shown in Fig. 13 through mounting holes 65, to each of the tapered sleeve 50 and the drive sleeve 54 thereby fastening them to one another.

The radial stiffness control element 64 is arranged to control the stiffness of the engagement means. In one example that the Applicant has conceived, the radial stiffness control element 64 is configured to substantially rigidly connect the tapered sleeve 50 and the drive sleeve 54 together in the axial direction. That is, the engagement means is axially rigid. At the same time, the radial stiffness control element 64 is arranged to control the radial stiffness of the engagement means at the desired level. The radial stiffness of the engagement means could be different depending on the particular application or size of the kinetic energy storage machine, for example. A circumferentially extending array of slots 66 are defined in the tubular body of the radial stiffness control element 62. The array of slots 66 allows the stiffness of the engagement means to be controlled to a very high degree of precision. The radial stiffness control element 64 may be constructed from any suitable material, for example, metals, metal alloys, composite materials, and/or plastics materials.

The axial stiffness control element, or cage 60, is fastened, for instance by any suitable fasteners such as through mounting holes 65, to each of the fixed sleeve 56 and to the low-speed bearing case 22a. The axial stiffness control element is arranged to control the stiffness of the engagement support. In one example that the Applicant has conceived, the axial stiffness control element is configured to substantially have a high radial stiffness. In this way, the axial stiffness control element allows the radial forces generated by bringing the low-speed bearing 12 into engagement with the rotor 200 to be directly transmitted to the low-speed bearing case 22a and the housing 160 in general. Directing the radial loads through the radially high-stiffness cage 60 ensures that the actuator 16 components are not subject to the radial forces. At the same time, the axial stiffness control element is arranged to control the axial stiffness of the engagement support at the desired level. Again, the axial stiffness desired of the engagement support could be different depending on the particular application or size of the kinetic energy storage machine, for example. Furthermore, controlling the axial stiffness of the engagement support can help absorb the forces generated and accommodate any misalignment that can occur when the engagement means makes initial contact with the rotor 200.

A circumferentially extending array of slots 62 are defined in the annulus body of the axial stiffness control element. The array of slots 62 allows the stiffness of the engagement support to be controlled to a very high degree of precision. The axial stiffness control element may be constructed from any suitable material, for example, metals, metal alloys, composite materials, and/or plastics materials.

Fig. 18 schematically illustrates an example of a contact sleeve 50, such as from the low-speed bearing of Fig. 16, and how the contact sleeve 50 acts as a bearing for the rotor shaft 202. In this case, the contact sleeve is a journal or plain bearing. For example, the contact sleeve may be made from synthesized bronze, which can, in some examples, be effectively self-lubricating. A plain bearing will require little maintenance and is of low cost; however, a plain bearing will involve higher energy losses due to the higher levels of friction at the contact surfaces.

Fig. 19 schematically illustrates another example of a contact sleeve 50. In this example, the contact sleeve 50 comprises a dry roller bearing 80. In this example, the inner race of the dry roller bearing 80 is driven into contact with the shaft 202 when the engagement means is moved so as to make contact with the rotor 200. A dry roller bearing will reduce the friction and not require lubrication; however, higher levels of maintenance may be required and costs will be higher.

Instead of, or in addition to the above example embodiments in which the kinetic energy storage machine 100 is adapted to assume the low-speed bearing suspension/release conditions by engaging/disengaging a first portion 12’ of the low-speed bearing 12 to the rotor 200, the kinetic energy storage machine 100 may be adapted to assume the low-speed bearing suspension condition and the low-speed bearing release condition, respectively, in other ways. This will be elaborated on hereinbelow. For the sake of completeness, it should be noted that the below presentation of embodiments puts emphasis on features for assuming the low-speed bearing suspension condition and the low-speed bearing release condition, respectively. Thus, the features as presented below are combinable with features of any one of the embodiment presented above.

To this end, refence is made to Fig. 20, illustrating a cross-sectional view of a portion of an embodiment of the kinetic energy storage machine 100. The Fig. 20 embodiment comprises an actuation arrangement 120 as has been presented above.

Purely by way of example, a portion of a kinetic energy storage machine 100 illustrated in Fig. 20 may correspond to the case 20a presented hereinabove with relation to e.g. Fig. 11. Purely by way of example, it may be envisaged that the Fig. 20 portion may replace a portion of any one of the embodiments presented above. For instance, the Fig. 20 portion may replace the Fig. 11 case 20a.

Fig. 20 illustrates a low-speed bearing 12 comprising a first portion 12’ and a second portion 12”. As a non-limiting example, and as indicated in Fig. 20, the first portion 12’ of the low-speed bearing 12 may comprise or even be constituted by an inner ring of the low-speed bearing 12. In a similar vein, and also indicated in Fig. 20 by way of example, the second portion 12” of the low-speed bearing 12 may comprise or even be constituted by an outer ring of the low-speed bearing 12.

Fig. 20 also illustrates the cross-section of a portion of the rotor 200. Purley by way of example, as indicated above, the rotor 200 may comprise at least one shaft 202a. By way of example only, the first portion of the low-speed bearing 12’ may be fixed to the rotor 200, e.g. fixed to a shaft 202a forming part of the rotor 200. Moreover, Fig. 20 illustrates a portion of a supporting structure 20a. In the Fig. 20 example, the supporting structure 20a forms part of a case enclosing the low-speed bearing 12 and possibly also the high-speed bearing (not shown) discussed in detail hereinabove. The rotor 200 is adapted to rotate around a rotor axis of rotation A, extending in the axial direction (see Fig. 1) , relative to the supporting structure 20a.

The Fig. 20 kinetic energy storage machine 100 is adapted to assume the low-speed bearing suspension condition by engaging the second portion 12” of the low-speed bearing 12 with the supporting structure 20a and to assume the low-speed bearing release condition by disengaging the second portion 12” of the low-speed bearing 12 from the supporting structure 20a.

The above engagement and disengagement between the second portion of the low-speed bearing 12” and the supporting structure 20a may be achieved in a plurality of different ways. Purely by way of example, it is envisaged that the kinetic energy storage machine 100 may comprise a tapered sleeve (not shown in Fig. 20) such as the one discussed above and the supporting structure 20a may comprise a conical surface (not shown in Fig. 20) complementary to the tapered sleeve, and wherein the tapered sleeve is, in use, movable into contact with the conical surface to engage the second portion 12” of the low-speed bearing 12 and the supporting structure 20a, and is movable out of contact with the conical surface to disengage the second portion 12” of the low-speed bearing 12 from the supporting structure 20a. Such a tapered sleeve and conical surface may form part of an actuation arrangement 120 of the kinetic energy storage machine 100.

As another non-limiting example, the actuation arrangement 120 of the kinetic energy storage machine 100 may comprise one or more actuators (not shown in Fig. 20) such as one or more linear actuators adapted to assume a retracted condition and an extracted condition, respectively. Purely by way of example, when such an actuator assumes the extracted condition, the actuator connects each one of the second portion 12” of the low-speed bearing 12 and the supporting structure 20a and when such an actuator assumes the retracted condition, the actuator disconnects the second portion 12” of the low-speed bearing 12 from the supporting structure 20a via the actuator. Again, such one or more actuators may form part of an actuation arrangement 120 of the kinetic energy storage machine 100.

Fig. 20 illustrates an embodiment in which the actuation arrangement 120 comprises one or more engaging members 230. Each one the engaging members 230 is movable between an engaged position and a release position. In the engaged position (illustrated in Fig. 20) , each one of the one or more engaging members 230 contacts the second portion 12” of the low-speed bearing 12 such that the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition. In the release position, each one of the one or more engaging members 230 separates, preferably at least in the radial direction RD, from the second portion 12”of the low-speed bearing 12 such that the at least one low-speed bearing 12 assumes the low-speed bearing release condition.

The Fig. 20 example comprises four engaging members 230 but it is of course envisaged that embodiments of the kinetic energy storage machine 100 may comprise fewer or more engaging members 230.

It is envisaged that each one the engaging members 230 may be movable between an engaged position and a release position in a plurality of different ways. Purely by way of example, each one of the engaging members 230 may be moved between an engaged position and a release position along the radial direction RD.

Fig. 20 illustrates an example embodiment in which the actuation arrangement further comprises a control element 232 being rotatable relative to the supporting structure 20a around a control element axis of rotation CE extending in the axial direction AD. The actuation arrangement is such that the one or more engaging members 230 may be moved between the engaged position and the release position by rotation of the control element 232 around the control element axis of rotation CE. To this end, though purely by way of example, the control element 232 may comprise a set of teeth 246 adapted to engage with the control element 232. As a non-limiting example, as illustrated in the Fig. 20 example, the control element 232 may comprise one tooth 246 for each engaging member 230. However, as may be realized from the below description, one tooth 246 of the control element 232 may be adapted to interact with two engaging members 230. Moreover, one engaging member 230 may be adapted to interact with two teeth 246 of the control element 232. Furthermore, as exemplified in Fig. 20, the control element 232 may have the shape of a ring.

Purely by way of example, and as exemplified in Fig. 20, the control element 232 may enclose each one of the one or more engaging members 230 such that each one of the one or more engaging members 230 extends from the control element 232 towards the second portion 12” of the low-speed bearing 12 at least partially in the radial direction RD.

Moreover, each one of the one or more engaging members 230 may be pivotable around a pivot axle 234 being located between the control element 232 and the second portion 12” of the low-speed bearing 12 in the radial direction RD. Purely by way of example, each engaging members 230 may be pivotally connectable to an individual pivot axle 234. Furthermore, by way of example only, each pivot axle 234 may be connected to the supporting structure 20a.

Fig. 21 illustrates an exemplary implementation of an engaging member 230 and a pivot axle 234. In the Fig. 21 example, the engaging member 230 comprises a load receiving portion 236, adapted to receive a load from the control element 232, e.g. from one or more teeth 246 of the control element 232. Moreover, the engaging member 230 may comprise a pivot connection portion 238 adapted to be connected to the pivot axle 234. Purely by way of example, and as illustrated in Fig. 21, the pivot connection portion 238 may comprise a pivot connection opening 240 adapted to receive the pivot axle 234. Additionally, the engaging member 230 exemplified in Fig. 21 comprises an engagement portion 242. As a non-limiting example, and as illustrated in Fig. 21, the engagement portion 242 may comprise an engagement surface 244 that is adapted to be brought in or out of contact with the second portion of the low-speed bearing (not shown in Fig. 21) . Moreover, though purely by way of example, the pivot connection portion 238 and the engagement portion 242 may be located on separate arms of the engaging member 230.

As exemplified in Fig. 21, when a tooth 246 of the control element 232 abuts the load receiving portion 236 such that the load receiving portion 236 will be imparted a load to the left in Fig. 21, the engaging member 230 will pivot in a clock-wise direction around the pivot axle 234 in the Fig. 21 example. Thus, the engagement portion 242 with the engagement surface 244 will be moved towards the second portion of the low-speed bearing (not shown in Fig. 21) such that the engagement surface 244 may contact the second portion of the low-speed bearing, thereby achieving the low-speed bearing suspension condition.

Fig. 22 illustrates the Fig. 21 implementation of an engaging member 230 in a condition in which a tooth 246 of the control element 232 abuts the load receiving portion 236 such that the load receiving portion 236 will be imparted a load to the right in Fig. 22. As such, in the Fig. 22 condition, the engaging member 230 will pivot in a counter clock-wise direction around the pivot axle 234. Thus, the engagement portion 242 with the engagement surface 244 will be moved away from the second portion of the low-speed bearing (not shown in Fig. 22) such that the engagement surface 244 may not contact the second portion of the low-speed bearing, thereby achieving the low-speed bearing release condition.

Fig. 23 illustrates the Fig. 20 embodiment in the low-speed bearing release condition. As may be realized when comparing Fig. 20 and Fig. 23, as compared to the condition in Fig. 20, the control element 232 has been rotated counter clock-wise in Fig. 23, thereby ensuring that each one of the engaging members 230 is in the condition presented above with reference to Fig. 22 such that the low-speed bearing release condition is obtained.

As may be realized from the above, it may be desired to control the rotational movement of the control element 232. To this end, and as illustrated in Fig. 24 as a non-limiting example, the actuation arrangement may comprise a control element actuator 252, which for instance may be implemented as an electric motor, configured to actuate the control element 232 to rotate around the control element axis of rotation. As a non-limiting example and as illustrated in Fig. 24, the control element actuator 252 and the control element 232 may be connected to each other via a worm gear 248. In the Fig. 24 embodiment, the control element actuator 252 is connected to the worm gear 248 via a belt drive 254. However, it is also envisaged that the control element actuator 252 may be connected to the worm gear 248 in other ways. Purely by way of example, the control element actuator 252 may be rotationally fixed to the worm gear 248.

With reference to Fig. 25, it should be noted that the actuation arrangement presented hereinabove with reference to Figs. 20 –25 may be connected to another portion of the kinetic energy storage machine 100 via a connection arrangement that comprises one or more pillars 256. By choosing structural features of the pillars 256, it may be possible to control the above-mentioned second radial stiffness of the low-speed bearing suspension.

It should be noted that the above description of the kinetic energy storage machine 100 also is a description of a method for operating a kinetic energy storage machine 100. However, for the sake of completeness, embodiments of the method according to the present disclosure are presented below.

As such, the present disclosure relates to a method for operating a kinetic energy storage machine 100, the kinetic energy storage machine 100 comprising (see e.g. Fig. 1) :

a rotor 200 having an axial extension in an axial direction AD and a radial extension in a radial direction RD,

a supporting structure 20a for supporting the rotor 200, the rotor 200 being adapted to rotate around a rotor axis of rotation A, extending in the axial direction AD, relative to the supporting structure 20a, and

a bearing arrangement comprising:

at least one high-speed bearing 14, the kinetic energy storage machine being adapted to assume a high-speed bearing suspension condition in which load transfer between the rotor and the supporting structure is achieved via the high-speed bearing, thereby providing a high-speed bearing suspension with a first radial stiffness, and

at least one low-speed bearing 12, the kinetic energy storage machine being adapted to assume a low-speed bearing suspension condition in which load transfer between the rotor and the supporting structure is achieved via the low-speed bearing, thereby providing a low-speed bearing suspension with a second radial stiffness, the second radial stiffness being higher than the first radial stiffness, the kinetic energy storage machine further being adapted to assume a low-speed bearing release condition in which load transfer between the rotor and the supporting structure via the low-speed bearing is disabled, the method comprising controlling the kinetic energy storage machine 100 so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor is above a low-speed bearing shift rotational speed.

By way of example, the method may further comprise:

- accelerating, while the kinetic energy storage machine 100 assumes the low-speed bearing suspension condition, the rotor 200 to the low-speed bearing shift rotational speed; and

- controlling the kinetic energy storage machine 100 so as to assume the low-speed bearing release condition once the rotor reaches or exceeds the low-speed bearing shift rotational speed.

As a non-limiting example, the kinetic energy storage machine 100 may further be adapted to assume a high-speed bearing release condition in which load transfer between the rotor 200 and the supporting structure via the high-speed bearing is disabled, the method further comprises:

It should be noted that embodiments of the present disclosure may be present in accordance with any one of the below examples.

Example 1. A bearing system for radially constraining rotational motion of a rotor in a kinetic energy storage machine, the bearing system comprising:

at least one high-speed bearing engageable, in use, with the rotor to provide radial constraint, wherein the high-speed bearing has a first radial stiffness, and

at least one low-speed bearing engageable, in use, with the rotor to provide radial constraint, wherein the low-speed bearing has a second radial stiffness that is higher than the first radial stiffness, wherein the low-speed bearing is configured to be engageable and disengageable from the rotor when the rotor is rotating, and wherein, when the low-speed bearing is engaged with the rotor, the rotor is operable without any critical speeds in a subcritical speed range below a transition speed, and wherein the transition speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor.

Example 2. The bearing system of example 1, wherein the high-speed bearing is configured to be engageable and disengageable from the rotor when the rotor is in motion.

Example 3. The bearing system of example 1 or example 2, wherein the high-speed bearing is an active magnetic bearing.

Example 4. The bearing system of example 3, wherein the high-speed bearing is engageable and disengagable with the rotor by respectively applying and removing a magnetic field to the rotor.

Example 5. The bearing system of any one of examples 1 to 4, wherein the low-speed bearing and the high-speed bearing are spaced apart along an axial direction of the rotor.

Example 6. The bearing system of any one of examples 1 to 5, wherein the transition speed is lower than a first critical speed of the rotor when the low-speed bearing is engaged with the rotor.

Example 7. The bearing system of any one of examples 1 to 6, wherein the low-speed bearing is configured to engage the rotor by contacting the rotor and to disengage from the rotor by separating from the rotor.

Example 8. The bearing system of example 7, wherein the low-speed bearing comprises an engagement means, wherein the engagement means is movable from a first position to a second position where the engagement means makes contact with the rotor, and wherein the engagement means is movable from the second position to the first position to separate the engagement means from the rotor.

Example 9. The bearing system of example 8, wherein the bearing system comprises an actuator, the actuator configured to, in use, move the engagement means from the first position to the second position and/or from the second position to the first position.

Example 10. The bearing system of example 8 or example 9, wherein the engagement means comprises a tapered sleeve configured to engage a complementary conical surface of the rotor.

Example 11. The bearing system of any one of examples 8 to 10, wherein the engagement means is movable in the axial direction.

Example 12. A kinetic energy storage machine comprising:

a rotor; and

at least one bearing system to, in use, constrain rotational motion of the rotor in a radial direction of the rotor, the bearing system comprising:

a high-speed bearing, the high-speed bearing engageable with the rotor to radially constrain the rotor above a transition speed, wherein the transition speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor; and a low-speed bearing, the low-speed bearing engageable with the rotor to radially constrain the rotor, wherein the low-speed bearing is configured so that when the low-speed bearing is engaged with the rotor, the rotor is rotatable without any critical speeds in a subcritical speed range below the transition speed.

Example 13. The kinetic energy storage machine of example 12, wherein the rotor comprises at least one shaft, and wherein the high-speed bearing and/or the low-speed bearing are engageable with the at least one shaft.

Example 14. The kinetic energy storage machine of example 12 or example 13, wherein the high-speed bearing and the low-speed bearing are spaced apart in an axial direction of the rotor.

Example 15. The kinetic energy storage machine of any one of examples 12 to 14, wherein the high-speed bearing comprises an active magnetic bearing.

Example 16. The kinetic energy storage machine of any one of examples 12 to 15, wherein the low-speed bearing comprises a tapered sleeve, and wherein the rotor comprises a conical surface complementary to the tapered sleeve, and wherein the tapered sleeve is, in use, movable into contact with the conical surface to engage the low-speed bearing with the rotor, and is movable out of contact with the conical surface to disengage the low-speed bearing from the rotor.

Example 17. The kinetic energy storage machine of example 16, wherein the low-speed bearing comprises an actuator, the actuator configured to, in use, move the tapered sleeve into and out of contact with the conical surface.

Example 18. The kinetic energy storage machine of any one of examples 12 to 17, wherein the kinetic energy storage machine comprises a first bearing system and a second bearing system, and wherein the first bearing system and the second bearing system are arranged at axially opposing ends of the rotor.

Example 19. The kinetic energy storage machine of any one of examples 12 to 17, wherein the kinetic energy storage machine comprises a radial constraint bearing, and wherein the at least one bearing system and the radial constraint bearing are arranged at axially opposing ends of the rotor.

Example 20. The kinetic energy storage machine of example 19, wherein the radial constraint bearing comprises an active magnetic bearing.

Example 21. The kinetic energy storage machine of any one of examples 12 to 20, wherein the kinetic energy storage machine comprises an axial bearing to constrain rotational motion of the rotor in an axial direction of the rotor.

Example 22. The kinetic energy storage machine of example 21, wherein the axial bearing comprises a permanent magnet bearing.

Example 23. The kinetic energy storage machine of any one of examples 12 to 16, wherein the kinetic energy storage machine comprises combination bearing, and wherein the combination bearing comprises an axial bearing and a radial constraint bearing.

Example 24. The kinetic energy storage machine of any one of examples 12 to 112, wherein the rotor comprises at least one balancing disc.

Example 25. The kinetic energy storage machine of example 24, wherein the rotor comprises a first balancing disc and a second balancing disc, and wherein the first balancing disc and the second balancing disc are arranged at axially opposing ends of the rotor.

Example 26. The kinetic energy storage machine of any one of examples 12 to 25, wherein the kinetic energy storage machine comprises a damper to reduce vibrations in the rotor and/or kinetic energy storage machine.

Example 27. The kinetic energy storage machine of any one of examples 12 to 26, wherein the rotor is oriented, in use, with an axis of rotation arranged substantially vertically.

Example 28. The kinetic energy storage machine of any one of examples 12 to 27, wherein the rotor comprises an energy storage component with high inertia.

Example 29. The kinetic energy storage machine of any one of examples 12 to 28, wherein the kinetic energy storage machine comprises a vacuum chamber to contain the rotor.

Example 30. The kinetic energy storage machine of any one of examples 12 to 29, wherein the rotor is detachably coupled to an electrical machine, the electrical machine selected from: an electrical motor, an electrical generator, or an electrical motor/generator.

Example 31. The kinetic energy storage machine of example 30, wherein the kinetic energy storage machine comprises a flexible coupling to couple the electrical machine to the rotor.

Example 32. The kinetic energy storage machine of any one of examples 12 to 31, wherein the kinetic energy storage machine comprises a controller.

Example 33. The kinetic energy storage machine of any one of examples 12 to 32, wherein the kinetic energy storage machine comprises:

a processor; and

a non-transitory machine-readable storage medium, the machine-readable storage medium comprising instructions that, when executed by the processor, control the processor to: accelerate the rotor, while the low-speed bearing is engaged with the rotor, the rotor to the transition speed; and

disengage, with the high-speed bearing engaged with the rotor, the low-speed bearing from the rotor once the rotor exceeds the transition speed.

Example 34. A method of operating a kinetic energy storage machine, in which the kinetic energy storage machine comprises a rotor and a bearing system to provide radial constraint to the rotor, and wherein the bearing system comprises a high-speed bearing and a low-speed bearing, wherein the low-speed bearing is radially stiffer than the high-speed bearing and is configured so that, when the low-speed bearing is engaged with the rotor, the rotor is rotatable below a disengagement rotational speed without any critical speeds in a subcritical speed range below the disengagement rotational speed, and wherein the disengagement rotational speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor, the method comprising:

accelerating, while the low-speed bearing is engaged with the rotor to radially constrain the rotor, the rotor to the disengagement rotational speed; and

disengaging, with the high-speed bearing engaged with the rotor to radially constrain the rotor, the low-speed bearing from the rotor once the rotor reaches or exceeds the disengagement rotational speed.

Example 35. The method of example 34, wherein the method comprises accelerating, while the low-speed bearing is disengaged from the rotor, the rotor to a storage rotational speed.

Example 36. The method of example 34 or example 35, wherein disengaging the low-speed bearing from the rotor comprises moving an engagement means from an engagement position, in which the engagement means is in contact with the rotor, to a disengaged position, in which the engagement means is separated from the rotor.

Example 37. The method of any one of examples 34 to 36, wherein the method comprises engaging the high-speed bearing with the rotor before the rotor reaches the disengagement rotational speed.

Example 38. The method of example 37, wherein the high-speed bearing comprises an active magnetic bearing, and wherein the method comprises activating the active magnetic bearing to apply a radially constraining magnetic field to the rotor.

Example 39. The method of any one of examples 34 to 38, wherein the method comprises accelerating the rotor using an electrical motor or electrical motor/generator coupled to the rotor.

Example 40. The method of any one of examples 34 to 39, wherein the kinetic energy storage machine comprises a vacuum chamber to contain the rotor, and wherein the method comprises drawing a vacuum in the vacuum chamber before and/or during acceleration of the rotor.

Example 41. A method of operating a kinetic energy storage machine, in which the kinetic energy storage machine comprises a rotor and a bearing system to provide radial constraint to the rotor, and wherein the bearing system comprises a high-speed bearing and a low-speed bearing, wherein the low-speed bearing is radially stiffer than the high-speed bearing and is configured so that, when the low-speed bearing is engaged with the rotor, the rotor is rotatable below an engagement rotational speed without any critical speeds in a subcritical speed range below the engagement rotational speed, and wherein the engagement rotational speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor, the method comprising:

decelerating, while the high-speed bearing is engaged with the rotor to radially constrain the rotor, the rotor to the engagement rotational speed; and

engaging, with the high-speed bearing engaged with the rotor and once the rotor reaches or drops below the engagement rotational speed, the low-speed bearing with the rotor to radially constrain the rotor.

Example 42. The method of example 41, wherein the method comprises decelerating, while the low-speed bearing is engaged with the rotor, the rotor to a stop.

Example 43. The method of example 41 or example 42, wherein the method comprises disengaging the high-speed bearing from the rotor once the rotor drops below the engagement rotational speed.

Example 44. A non-transitory machine-readable storage medium, the machine-readable storage medium comprising instructions that, when executed by a processor, control the processor to:

accelerate a rotor of a kinetic energy storage machine to a disengagement rotational speed, while a low-speed bearing of a bearing system is engaged with the rotor to radially constrain the rotor such that the rotor is rotatable below the disengagement rotational speed without any critical speeds in a subcritical speed range below the disengagement rotational speed; and disengage, with a high-speed bearing of the bearing system, which is of lower radial stiffness than the low-speed bearing, engaged with the rotor to radially constrain the rotor, the low-speed bearing from the rotor once the rotor reaches or exceeds the disengagement rotational speed, and wherein the disengagement rotational speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor.

Example 45. A non-transitory machine-readable storage medium, the machine-readable storage medium comprising instructions that, when executed by a processor, control the processor to:

decelerate a rotor of a kinetic energy storage machine to an engagement rotational speed, while a high-speed bearing of a bearing system is engaged with the rotor to radially constrain the rotor, and wherein the engagement rotational speed is located within a supercritical speed range of the rotor when only the high-speed bearing is engaged with the rotor; and engage, with the high-speed bearing engaged with the rotor and once the rotor reaches or drops below the engagement rotational speed, a low-speed bearing of the bearing system, which is of higher radial stiffness than the high-speed bearing, with the rotor to radially constrain the rotor such that the rotor is rotatable below the engagement rotational speed without any critical speeds in a subcritical speed range below the engagement rotational speed.

Example 46. A low-speed bearing for a bearing system that, in use, radially constrains the rotational motion of a rotor in a kinetic energy storage machine, wherein the bearing system comprises the low-speed bearing and a high-speed bearing, the low-speed bearing comprising:

an engagement means, which is engageable with a complementary engagement means of the rotor, and which is movable from a first position to a second position where the engagement means contacts the complementary engagement means of the rotor to radially constrain the rotor; and

an actuator, wherein the actuator is configured to, in use, move the engagement means from the first position to the second position and/or from the second position to the first position.

Example 47. The low-speed bearing of example 46, wherein the engagement means is movable along an axial direction of the rotor to engage with the complementary engagement means.

Example 48. The low-speed bearing of example 47, wherein the engagement means comprises a contact sleeve mounted to a drive sleeve by way of a radial stiffness control element.

Example 49. The low-speed bearing of example 48, wherein the actuator comprises a nut and the drive sleeve comprises a screw threaded onto the nut so that the drive sleeve is movable along the axial direction when the nut is rotated.

Example 50. The low-speed bearing of example 49, wherein the actuator comprises a worm screw and the nut comprises a worm gear meshed with the worm screw, and wherein the actuator comprises a motor to, in use, rotate the worm screw and thereby rotate the nut to move the drive sleeve.

Example 51. The low-speed bearing of any one of examples 46 to 50, wherein the low-speed bearing comprises an engagement support to brace the engagement means when the engagement means engages the rotor.

Example 52. The low-speed bearing of examples 51, wherein the engagement support comprises an axial stiffness control element through which the engagement support is fixable to a low-speed bearing case.

It will be understood that the above embodiment descriptions are given by way of example only and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. It is to be understood that any feature described in relation to one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other examples.

Claims

A kinetic energy storage machine (100) comprising:

a rotor (200) having an axial extension in an axial direction (AD) and a radial extension in a radial direction (RD) ,

a supporting structure (20a) for supporting the rotor (200) , the rotor (200) being adapted to rotate around a rotor (200) axis of rotation (A) , extending in the axial direction (AD) , relative to the supporting structure (20a) , and

a bearing arrangement (10) comprising:

at least one high-speed bearing (14) , the kinetic energy storage machine (100) being adapted to assume a high-speed bearing suspension condition in which load transfer between the rotor (200) and the supporting structure (20a) is achieved via the high-speed bearing (14) , thereby providing a high-speed bearing suspension with a first radial stiffness, and

at least one low-speed bearing (12) , the kinetic energy storage machine (100) being adapted to assume a low-speed bearing suspension condition in which load transfer between the rotor (200) and the supporting structure (20a) is achieved via the low-speed bearing (12) , thereby providing a low-speed bearing suspension with a second radial stiffness, the second radial stiffness being higher than the first radial stiffness, the kinetic energy storage machine (100) further being adapted to assume a low-speed bearing release condition in which load transfer between the rotor (200) and the supporting structure (20a) via the low-speed bearing (12) is disabled,

wherein the kinetic energy storage machine (100) is configured so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor (200) is above a low-speed bearing (12) shift rotational speed.
The kinetic energy storage machine (100) of claim 1, wherein the kinetic energy storage machine (100) is configured such that it can switch between the low-speed bearing suspension condition and the low-speed bearing release condition when the rotor (200) is rotating relative to the supporting structure (20a) .
The kinetic energy storage machine (100) of claim 1 or claim 2, wherein the kinetic energy storage machine (100) comprises an actuation arrangement (120) , the actuation arrangement (120) being adapted to assume each one of a first condition and a second condition relative to the low-speed bearing (12) such that when the actuation arrangement (120) is in the first condition, the kinetic energy storage machine (100) assumes the low-speed bearing release condition and when the actuation arrangement (120) is in the second condition, the kinetic energy storage machine (100) assumes the low-speed bearing suspension condition.
The kinetic energy storage machine (100) of claim 3, wherein a movement from the first condition to the second condition comprises a movement of at least a portion of the actuation arrangement (120) in the axial direction (AD) .
The kinetic energy storage machine (100) of claim 3, wherein a movement from the first condition to the second condition comprises a movement of at least a portion of the actuation arrangement (120) in the radial direction (RD) .
The kinetic energy storage machine (100) of any one of claims 1 -4, wherein the low-speed bearing (12) comprises a first portion (12’) and a second portion (12”) , the kinetic energy storage machine (100) being adapted to assume the low-speed bearing suspension condition by engaging a second portion (12”) of the low-speed bearing (12) with the supporting structure (20a) and to assume the low-speed bearing release condition by disengaging the second portion (12”) of the low-speed bearing (12) from the supporting structure (20a) , preferably the first portion (12’) of the low-speed bearing (12) is fixed to the rotor (200) .
The kinetic energy storage machine (100) of claim 6, when dependent on claim 3, wherein the actuation arrangement (120) comprises one or more engaging members (230) , each one of which being movable between an engaged position and a release position, wherein in the engaged position, each one of the one or more engaging members (230) contacts the second portion (12”) of the low-speed bearing (12) such that the kinetic energy storage machine (100) assumes the low-speed bearing suspension condition, and wherein in the release position, each one of the one or more engaging members (230) separates, preferably at least in the radial direction (RD) , from the second portion (12”) of the low-speed bearing (12) such that the at least one low-speed bearing (12) assumes the low-speed bearing release condition.
The kinetic energy storage machine (100) of claim 7, wherein the actuation arrangement (120) further comprises a control element (232) being rotatable relative to the supporting structure (20a) around a control element (232) axis of rotation (A) extending in the axial direction (AD) , the actuation arrangement (120) being such that the one or more engaging members (230) may be moved between the engaged position and the release position by rotation of the control element (232) around the control element (232) axis of rotation (A) .
The kinetic energy storage machine (100) of claim 8, wherein the control element (232) encloses each one of the one or more engaging members (230) such that each one of the one or more engaging members (230) extends at least in the radial direction (RD) from the control element (232) towards the second portion (12”) of the low-speed bearing (12) at least partially in the radial direction (RD) , each one of the one or more engaging members (230) being pivotable around a pivot axle (234) being located between the control element (232) and the second portion (12”) of the low-speed bearing (12) in the radial direction (RD) .
The kinetic energy storage machine (100) of claim 8 or 9, wherein the actuation arrangement (120) further comprises a control element actuator (252) configured to actuate the control element (232) to rotate around the control element (232) axis of rotation (A) , preferably the control element actuator (252) and the control element (232) are connected to each other via a worm gear.
The kinetic energy storage machine (100) according any one of the preceding claims, wherein the kinetic energy storage machine (100) is adapted to assume the low-speed bearing suspension condition by engaging a first portion (12’) of the low-speed bearing (12) to the rotor (200) , the kinetic energy storage machine (100) further being adapted to assume the low-speed bearing release condition by disengaging the first portion (12’) of the low-speed bearing (12) from the rotor (200) .
The kinetic energy storage machine (100) of claim 11, wherein the rotor (200) comprises at least one shaft (202a) , and wherein the first portion (12’) of the low-speed bearing (12) is engageable with the at least one shaft (202a) .
The kinetic energy storage machine (100) of any one of claims 11 to 12, when dependent on claim 3, wherein the actuation arrangement (120) comprises a tapered sleeve (50) , and wherein the rotor (200) comprises a conical surface (52) complementary to the tapered sleeve (50) , and wherein the tapered sleeve (50) is, in use, movable into contact with the conical surface (52) to engage the low-speed bearing (12) with the rotor (200) , and is movable out of contact with the conical surface (52) to disengage the low-speed bearing (12) from the rotor (200) .
The kinetic energy storage machine (100) of claim 13, wherein the kinetic energy storage machine (100) comprises a tapered sleeve (50) actuator, the tapered sleeve (50) actuator being configured to, in use, move the tapered sleeve (50) into and out of contact with the conical surface (52) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the at least one high-speed bearing (14) and the at least one low-speed bearing (12) are spaced apart in the axial direction (AD) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the at least one high-speed bearing (14) comprises an active magnetic bearing.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the at least one high-speed bearing (14) is configured to assume the high-speed bearing suspension condition when the rotor (200) is in motion.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) further is adapted to assume a high-speed bearing release condition in which load transfer between the rotor (200) and the supporting structure (20a) via the high-speed bearing (14) is disabled.
The kinetic energy storage machine (100) of claim 18, wherein the kinetic energy storage machine (100) is configured so as to assume the high-speed bearing release condition in response to detecting that a rotational speed of the rotor (200) is equal to or below a high-speed bearing (14) shift rotational speed.
The kinetic energy storage machine (100) of claim 18 or claim 19, when dependent on claim 16, wherein the kinetic energy storage machine (100) further is adapted to switch between the high-speed bearing suspension condition and the high-speed bearing release condition, respectively, by respectively applying and removing a magnetic field to the rotor (200) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) comprises a first a bearing arrangement (10) and a second a bearing arrangement (10) , preferably each one of the first a bearing arrangement (10) and the second bearing arrangement (10) being a bearing arrangement (10) in accordance with any one of the preceding claims, and wherein the first bearing arrangement (10) and the second bearing arrangement (10) are arranged at axially opposing ends of the rotor (200) .
The kinetic energy storage machine (100) of any one of claims 1 to 20, wherein the kinetic energy storage machine (100) comprises a secondary bearing arrangement (102) , wherein the bearing arrangement (10) and the secondary bearing arrangement (102) are arranged at axially opposing ends of the rotor (200) .
The kinetic energy storage machine (100) of claim 22, wherein the secondary bearing arrangement (102) comprises a magnetic bearing.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) comprises an axial bearing to adapted to take up a load from the rotor (200) in the axial direction (AD) .
The kinetic energy storage machine (100) of claim 24, wherein the axial bearing comprises a permanent magnet bearing.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) comprises a combination bearing adapted to take up a load from the rotor (200) in the axial direction (AD) as well as in the radial direction (RD) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the rotor (200) comprises at least one balancing disc.
The kinetic energy storage machine (100) of claim 27, wherein the rotor (200) comprises a first balancing disc (204a) and a second balancing disc (204b) , and wherein the first balancing disc (204a) and the second balancing disc (204b) are arranged at axially opposing ends of the rotor (200) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) comprises a damper (400) to reduce vibrations in the rotor (200) and/or kinetic energy storage machine (100) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the rotor (200) is oriented, in use, with the rotor (200) axis of rotation (A) arranged substantially vertically.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) comprises a vacuum chamber to contain the rotor (200) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the rotor (200) is detachably coupled to an electrical machine (150) , the electrical machine (150) being selected from: an electrical motor, an electrical generator, or an electrical motor/generator.
The kinetic energy storage machine (100) of claim 32, wherein the kinetic energy storage machine (100) comprises a coupling (152) adapted to selectively couple the electrical machine (150) to the rotor (200) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the at least one low-speed bearing (12) and the at least one high-speed bearing (14) are spaced apart along an axial direction (AD) of the rotor (200) .
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) is adapted such that when it assumes the low-speed bearing suspension condition, the rotor (200) is operable without any critical speeds in a subcritical speed range below a transition speed, and wherein the transition speed is located within a supercritical speed range of the rotor (200) when the kinetic energy storage machine (100) assumes the high-speed bearing suspension condition and the low-speed bearing release condition.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) is configured so as to assume the low-speed bearing suspension condition in response to detecting that the rotational speed of the rotor (200) is equal to or below the low-speed bearing (12) shift rotational speed.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) is adapted to detect a current rotational speed of the rotor (200) and to set the low-speed bearing (12) shift rotational speed in response to the current rotational speed.
The kinetic energy storage machine (100) of claim 37, wherein the kinetic energy storage machine (100) is adapted to:

- set the low-speed bearing (12) shift rotational speed to a first low-speed bearing (12) shift threshold speed in response to determining that the current rotational speed is equal to or below a low-speed bearing (12) transition speed, and

- set the low-speed bearing (12) shift rotational speed to a second low-speed bearing (12) shift threshold speed in response to determining that the current rotational speed is above the low-speed bearing (12) transition speed,

wherein the first low-speed bearing (12) shift threshold speed is lower than the second low-speed bearing (12) shift threshold speed.
The kinetic energy storage machine (100) of any of claims 1 -36, wherein the kinetic energy storage machine (100) is adapted to detect a current rotational acceleration of the rotor (200) and to set the low-speed bearing (12) shift rotational speed in response to the current rotational acceleration.
The kinetic energy storage machine (100) of claim 39, wherein the kinetic energy storage machine (100) is adapted to:

- set the low-speed bearing (12) shift rotational speed to a first low-speed bearing (12) shift threshold speed in response to determining that the current rotational acceleration is positive, and

- set the low-speed bearing (12) shift rotational speed to a second low-speed bearing (12) shift threshold speed in response to determining that the current rotational acceleration is negative,

wherein the first low-speed bearing (12) shift threshold speed is lower than the second low-speed bearing (12) shift threshold speed.
The kinetic energy storage machine (100) of any one of the preceding claims, when dependent on claim 19, wherein the kinetic energy storage machine (100) is adapted to detect a current rotational speed of the rotor (200) and to set the high-speed bearing (14) shift rotational speed in response to the current rotational speed.
The kinetic energy storage machine (100) of claim 41, wherein the kinetic energy storage machine (100) is adapted to:

- set the high-speed bearing (14) shift rotational speed to a first high-speed bearing (14) shift threshold speed in response to determining that the current rotational speed is equal to or below a high-speed bearing (14) transition speed, and

- set the high-speed bearing (14) shift rotational speed to a second high-speed bearing (14) shift threshold speed in response to determining that the current rotational speed is above the high-speed bearing (14) transition speed,

wherein the first high-speed bearing (14) shift threshold speed is higher than the second high-speed bearing (14) shift threshold speed.
The kinetic energy storage machine (100) of any of claims 1 -40, wherein the kinetic energy storage machine (100) is adapted to detect a current rotational acceleration of the rotor (200) and to set the high-speed bearing (14) shift rotational speed in response to the current rotational acceleration of the rotor (200) .
The kinetic energy storage machine (100) of claim 43, wherein the kinetic energy storage machine (100) is adapted to:

- set the high-speed bearing (14) shift rotational speed to a first high-speed bearing (14) shift threshold speed in response to determining that the current rotational acceleration is positive, and

- set the high-speed bearing (14) shift rotational speed to a second high-speed bearing (14) shift threshold speed in response to determining that the current rotational acceleration is negative,

wherein the first high-speed bearing (14) shift threshold speed is higher than the second high-speed bearing (14) shift threshold speed.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the kinetic energy storage machine (100) comprises a controller (500) adapted to control the kinetic energy storage machine (100) to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor (200) is above the rotational low-speed bearing (12) shift rotational speed.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the second radial stiffness is at least 5 times higher than the first radial stiffness, preferably 10 higher.
The kinetic energy storage machine (100) of any one of the preceding claims, wherein the supporting structure (20a) forms part of, or constitutes, a housing (160) at least partially enclosing the rotor (200) .
A method for operating a kinetic energy storage machine (100) , the machine comprising:

a rotor (200) having an axial extension in an axial direction (AD) and a radial extension in a radial direction (RD) ,

a supporting structure (20a) for supporting the rotor (200) , the rotor (200) being adapted to rotate around a rotor (200) axis of rotation (A) , extending in the axial direction (AD) , relative to the supporting structure (20a) , and

a bearing arrangement (10) comprising:

at least one high-speed bearing (14) , the kinetic energy storage machine (100) being adapted to assume a high-speed bearing suspension condition in which load transfer between the rotor (200) and the supporting structure (20a) is achieved via the high-speed bearing (14) , thereby providing a high-speed bearing suspension with a first radial stiffness, and

at least one low-speed bearing (12) , the kinetic energy storage machine (100) being adapted to assume a low-speed bearing suspension condition in which load transfer between the rotor (200) and the supporting structure (20a) is achieved via the low-speed bearing (12) , thereby providing a low-speed bearing suspension with a second radial stiffness, the second radial stiffness being higher than the first radial stiffness, the kinetic energy storage machine (100) further being adapted to assume a low-speed bearing release condition in which load transfer between the rotor (200) and the supporting structure (20a) via the low-speed bearing (12) is disabled,

the method comprising controlling the kinetic energy storage machine (100) so as to assume the low-speed bearing release condition in response to detecting that a rotational speed of the rotor (200) is above a low-speed bearing (12) shift rotational speed.
The method according to claim 50, wherein the method comprises:

- accelerating, while the kinetic energy storage machine (100) assumes the low-speed bearing suspension condition, the rotor (200) to the low-speed bearing (12) shift rotational speed; and

- controlling the kinetic energy storage machine (100) so as to assume the low-speed bearing release condition once the rotor (200) reaches or exceeds the low-speed bearing (12) shift rotational speed.
The method according to claim 50 or claim 51, wherein the kinetic energy storage machine (100) further is adapted to assume a high-speed bearing release condition in which load transfer between the rotor (200) and the supporting structure (20a) via the high-speed bearing (14) is disabled, the method further comprising:

- controlling the kinetic energy storage machine (100) so as to assume the high-speed bearing release condition in response to detecting that a rotational speed of the rotor (200) is equal to or below a high-speed bearing (14) shift rotational speed, and

- controlling the kinetic energy storage machine (100) so as to assume the high-speed bearing suspension condition in response to detecting that a rotational speed of the rotor (200) is above the high-speed bearing (14) shift rotational speed.