# Patent

## Title
Electromechanical flywheel with evacuation system

## Abstract

An electromechanical flywheel machine includes a flywheel mass enclosed in an evacuable housing.

## Background
PRIORITY CLAIM AND INCORPORATION BY REFERENCE
This application is a continuation-in-part of U.S. patent application Ser. No. 13/849,484 filed Mar. 23, 2013 which claims the benefit of U.S. Prov. Pat. App. No. 61/615,860 filed Mar. 26, 2012.
This application incorporates by reference, in their entireties and for all purposes: 1) U.S. patent application Ser. No. 13/849,484 filed Mar. 13, 2013, 2) U.S. Prov. Pat. App. No. 61/615,860 filed Mar. 26, 2012; 3) U.S. Pat. No. 6,884,039 to Woodard et al. filed Dec. 30, 2002; and 4) U.S. Pat. No. 6,175,172 to Bakholdin et al. filed Aug. 4, 1997.


BACKGROUND OF THE INVENTION
Known flywheels store kinetic energy, that is, the energy of motion. When called upon to release this energy, the flywheel slows as kinetic energy is depleted. Flywheels driving and driven by electric machines are also know. For decades, such electromechanical machines have been built and have achieved varying degrees of operational success. Widespread application has, however, eluded flywheel manufacturers as even the most advanced commercial machines suffer from significant operational limitations while exceeding the cost of better performing alternatives. Despite persistent efforts by a small flywheel manufacturing industry, modern electromechanical flywheels have found only narrow applications in a few niche markets and presently make no significant contribution to the developed world's energy supply.
Field of Invention
This invention relates to the electromechanical arts. In particular, an electromechanical flywheel includes an evacuation system for evacuating a flywheel mass enclosure.
Discussion of the Related Art
Electromechanical flywheels include machines operating under atmospheric conditions and machines operating under evacuated conditions. However, prior art vacuum systems have generally failed to establish and maintain desired vacuum conditions.
SUMMARY OF THE INVENTION
The present invention provides an electromechanical flywheel with an evacuation system.
In an embodiment, an electromechanical flywheel method of configuring rotating parts that is enabled by a variable geometry drag pump, the method comprising the steps of providing a flywheel mass made from a carbon composite; providing a rotor made from a metal; encircling the rotor with the mass; engaging the rotor and the mass via an interference fit therebetween; providing a variable geometry planar drag pump with a drag pump gap between a labyrinth ring and an end of the flywheel mass; and, during variable speed operation of the flywheel mass in an evacuated space, controlling the drag pump gap to limit the temperature rise of the flywheel mass.
And, in an embodiment, an electromechanical flywheel with a molecular drag pump comprises: a cylindrical motor-generator rotor surrounding a motor-generator stator; the motor-generator rotor encircled by and fixed to a cylindrical flywheel mass; a central axis about which the motor-generator rotor and flywheel mass rotate; a planar drag pump including a labyrinth ring with an annular working surface; the working surface in a plane about perpendicular to the central axis and centered on the central axis and; the working surface spaced apart from an end surface of the flywheel mass by a drag pump gap; and, an elevator that moves the working surface toward the flywheel mass end surface when the gap is larger than a first selected dimension and that moves the working surface away from the flywheel mass end surface when the gap is smaller than a second selected dimension.
In various embodiments, one or more of i) the labyrinth ring is located between the flywheel mass end surface and an elevator support located above the flywheel mass end surface; ii) three elevators are equally spaced around a circumference of the labyrinth ring; iii) the elevator includes an electromagnetic actuator, the actuator comprising an electrical coil surrounding a back iron arranged to magnetically attract a platen coupled via a link to the labyrinth ring for adjusting the gap; iv) the link passes through a hole centrally located in the back iron; v) the elevator includes a spring that encircles the link and urges the platen away from the back iron for increasing the gap; and vi) an evacuable housing encloses the flywheel mass.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is described with reference to the accompanying figures. These figures, incorporated herein and forming part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art to make and use the invention.
FIG. 1 shows a block diagram of an electromechanical flywheel machine in accordance with the present invention.
FIG. 2 shows selected functions and equipment of the electromechanical flywheel machine of FIG. 1.
FIG. 3 shows a first embodiment of the electromechanical flywheel machine of FIG. 1.
FIG. 4A shows a second embodiment of the electromechanical flywheel machine of FIG. 1.
FIG. 4B shows a third embodiment of the electromechancial flywheel machine of FIG. 1.
FIGS. 4C-J show drag pump embodiments for use with the electromechanical flywheel of FIG. 1.
FIG. 5A shows rotor poles of an electromechanical flywheel machine of FIG. 1.
FIG. 5B shows rotor poles and a stator of an electromechanical flywheel machine of FIG. 1.
FIG. 6 shows a lower bearing assembly and parts of an electromechanical flywheel machine of FIG. 1.
FIG. 7 shows an upper bearing assembly and parts of an electromechanical flywheel machine of FIG. 1.
FIG. 8 shows a fourth embodiment of the electromechanical flywheel machine of FIG. 1.
FIGS. 9A and 9B show a first external pumping system of the electromechanical flywheel machine of FIG. 1.
FIGS. 9C and 9D show a second external pumping system of the electromechanical flywheel machine of FIG. 1.
FIG. 9E shows a third external pumping system of the electromechanical flywheel machine of FIG. 1.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The disclosure provided in the following pages describes examples of some embodiments of the invention. The designs, figures, and descriptions are non-limiting examples of certain embodiments of the invention. For example, other embodiments of the disclosed device may or may not include the features described herein. Moreover, disclosed advantages and benefits may apply to only certain embodiments of the invention and should not be used to limit the disclosed inventions.
FIG. 1 shows an electromechanical flywheel machine 100. Electrical interconnections 104 electrically couple an energy exchange block 102, power electronics and controls 106, and an electric power network 108.
As used herein, unless otherwise stated, the term coupled refers to a direct or indirect connection such as 1) A connected directly to B and 2) C connected indirectly to E via D.
The energy exchange block 102 includes a spinning assembly 110 and a core assembly 112. The spinning assembly includes a motor-generator rotor 114, a flywheel mass 116, and a hub 118. The core assembly includes a motor-generator stator 120 and a motor-generator stator support 122. In various embodiments, the rotor is shaft-less. And, in various embodiments, the spinning assembly is shaft-less.
Electrical interconnections 104 include any of electrical conductor connections, electrical interface devices, electrical transducers, and the like. Power electronics and controls 106 include any of silicon and/or semiconductor devices, analog and digital processors, and related interfaces including human interfaces. The electric power network 108 is 1) a source of electric power to the energy exchange block 102 in some embodiments, 2) a user of electric power from the energy exchange block in some embodiments, and 3) both a source and a user of electric power to and from the energy exchange block in some embodiments.
FIG. 2 shows selected electromechanical flywheel machine functions and equipment 200. Energy storage 202 is central to flywheel operation. In electromechanical flywheels, energy storage and energy conversion 204 provide a means for converting kinetic energy to electrical power and/or converting electrical power to kinetic energy. Energy transfer 206 provides for electric power transfers between energy conversion equipment 220, 216 and an electric power network 108. In various embodiments, an electrical switch such a circuit breaker 230 provides for connecting and disconnecting conductors enabling power transfer. In various embodiments, other electromechanical flywheel machine functions include any of several auxiliary support functions 208 described below.
Energy storage 202 utilizes the spinning assembly 110. In various embodiments, a suspension system 210 supports the spinning assembly. Suspension equipment includes bearings or their equivalents 212 and in some embodiments a passive shutdown system 215 supports the spinning assembly in selected operating regimes such as shutdown.
Energy conversion 204 utilizes a means for converting kinetic energy into electrical power such as a generator or a motor-generator. A motor-generator 220 is shown. The motor-generator includes the rotor 114 and a stator 120 and provides a means for rotatably driving the spinning assembly 110 and for being rotatably driven by the spinning assembly. In various embodiments, power electronics 216 enable manipulation of electrical waveforms emanating from the motor-generator and/or the electric power network 108. For example, in various embodiments, power electronics provide for frequency conversion in an AC to AC converter having an intermediate DC bus and power electronics provide for variable speed drive functions such as accelerating the rotational speed of the flywheel rotor.
In various embodiments, auxiliary support functions 208 are carried out by auxiliary support equipment described more fully below. Auxiliary support functions include housing 240, safety 242, vacuum 244, cooling 248, and man-machine interface 246.
A control function 205 provides for one or more of monitoring, assessment, command, and control of other electromechanical flywheel functions. In particular, the control function enables electromechanical flywheel operation via supervision and/or control of one or more of the energy storage 202, energy conversion 204, energy transfer 206, and auxiliary support 208 functions.
FIG. 3 shows a first electromechanical flywheel portion 300. An energy exchange block 302 is enclosed by an inner housing 328 which is in turn enclosed by an optional outer housing 338.
The energy exchange block 302 includes a spinning assembly 310 and a core assembly 312. Included in the spinning assembly is a motor-generator rotor 314 and a flywheel mass encircling and coupled to the rotor 316, a hub 318 coupled to the flywheel mass, and a moving suspension element 344. In some embodiments, a sleeve such as a non-magnetic sleeve (e.g., non-magnetic metal alloys and super-alloys) is interposed between the rotor and the flywheel mass for, inter alia, backing the rotor and providing support to the rotor. The rotor, flywheel mass, hub, and moving suspension element are for rotation in synchrony about an axis x-x and in various embodiments the hub is attached to one or both of the rotor 350 and the flywheel mass 352. Opposite the moving suspension element is a stationery suspension element 346 with a support such as a first wall of the inner housing 332. Included in the core assembly 312 are a stator 320 and a stator support 322. In some embodiments the stator support is coupled to a wall of the inner housing such as a second wall of the inner housing 334.
Encircling the motor-generator stator 320 is the motor-generator rotor 314. In various embodiments, the rotor 314 includes magnetic 354 and nonmagnetic 356 portions and, in some embodiments, the nonmagnetic portion is or includes blocking or matrix material supporting the magnetic portions. In an embodiment, the magnetic rotor portions are laminated structures.
In various embodiments the stator 320 includes a magnetic structure with one or more interengaged coils having electrically conductive windings capable of carrying variable currents and thereby varying the magnetic flux of the magnetic structure. In some embodiments, a first stator coil 364 encircles an imaginary y-y axis that is about perpendicular to the x-x axis. And, in some embodiments, a second stator coil 368 encircles the x-x axis. In an embodiment, a plurality of first stator coils encircle respective imaginary y-y axes and one or more second stator coils encircle the x-x axis, the first stator coils being armature coils and the second stator coils being field coils.
And, in an embodiment, the motor-generator 360 is a homopolar electric machine with the illustrated inside-out arrangement (rotor encircles stator) wherein a) a rotatable rotor similar to rotor 314 includes coil-less, laminated magnetic structures, b) wherein a stationery central stator similar to stator 320 includes laminated magnetic structures with coils for creating a magnetic flux in the magnetic structures and c) the rotor encircles the stator.
FIG. 4A shows a second electromechanical flywheel portion 400A. An energy exchange block 402 is enclosed by an inner housing 428 which is enclosed, or partially enclosed, in some embodiments, by an outer housing (not shown).
The energy exchange block 402 includes a spinning assembly 410 and a core assembly 412. Included in the spinning assembly are a motor-generator rotor 414, a flywheel mass encircling and coupled to the rotor 416, a hub coupled to the flywheel mass 418, a support pin for supporting the hub 496, and a moving suspension assembly for supporting the hub 492. Some embodiments include a sleeve such as a non-magnetic sleeve between the rotor and the flywheel mass.
In various embodiments, the flywheel mass 416 includes layers of different materials such as fiberglass in one or more types or grades and carbon fiber in one or more types or grades. U.S. Pat. No. 6,175,172 filed Aug. 4, 1997 and entitled HUB AND CYLINDER DESIGN FOR FLYWHEEL SYSTEM FOR MOBILE ENERGY STORAGE provides additional information about flywheel mass materials of construction.
U.S. Pat. No. 6,175,172 filed Aug. 4, 1997 and entitled HUB AND CYLINDER DESIGN FOR FLYWHEEL SYSTEM FOR MOBILE ENERGY STORAGE provides additional information about flywheel mass construction techniques and materials shown in FIG. 4A and the related description. This patent is incorporated in its entirety and for all purposes.
As shown, the flywheel mass includes three layers with a first layer 415 adjacent to the rotor, an intermediate layer 419, and an outer layer 421. In an embodiment, the intermediate and outer layers include carbon fiber materials and the inner layer includes fiberglass. In another embodiment, all three layers are substantially made from carbon fiber materials. In various embodiments, one or more layers are pre-stressed such as by winding fibers under tension to form substantially cylindrical shell(s) with inherent compressive stress.
The support pin, moving suspension assembly and hub are concentrically arranged and are for rotation in synchrony about an axis x-x. As seen, the support pin 496 is located in a gap 491 between upper and lower bearing carriers 490, 494. Extending from the stator support 422 is an upper bearing carrier and supported from a first wall of the housing 432 is a lower bearing carrier. In an embodiment, elongation of the upper bearing carrier along the x-x axis 493 serves to rotatably restrain the support pin between the upper and lower bearing carriers. In this sense, the upper and lower bearing carriers provide a means to “capture” the spinning assembly 410 via the support pin and are useful for functions including passive shutdown. In various embodiments, the lower bearing carrier and the moving suspension assembly incorporate a first electromagnetic bearing.
A second electromagnetic bearing 451 is spaced apart from the upper and lower bearing carriers 490, 494. The second electromagnetic bearing includes a fixed bearing stator 454 supported by the stator support 422 and electrical windings 452 for magnetizing the stator and a geometrically opposing rotor 456 coupled to the rotor. As shown, the mating faces of the electromagnet 498, 499 are parallel to the x-x axis such that electromagnetic bearing forces are perpendicular to the x-x axis. In other embodiments, angled electromagnetic bearing faces such as those described infra provide electromagnetic bearing force components along an axis parallel to the x-x axis and along an axis perpendicular to the x-x axis.
Included in the core assembly 412 is a stator 420 and a stator support 422 coupled to a second wall of the inner housing 434. Encircling the motor-generator stator is the motor-generator rotor 414. In various embodiments, the rotor includes magnetic and nonmagnetic portions (e.g., see 354, 356 of FIG. 3) and, in some embodiments, the nonmagnetic portion is or includes blocking or matrix material supporting the magnetic portions. In an embodiment, the magnetic rotor portions are laminated structures.
In various embodiments, the stator 420 includes a magnetic structure with one or more interengaged coils having electrically conductive windings capable of carrying variable currents and thereby varying the magnetic flux of the magnetic structure.
In an embodiment, a stator such as a homopolar stator includes at least two peripheral rims and one smaller intermediate rim. The rims include a magnetic material such as iron and in various embodiments the rims are laminated structures with each laminate having a substantially annular shape.
As shown, the stator 420 includes three large diameter rims 464, 466, 470 and two smaller diameter rims 484, 488 such that substantially annular or somewhat doughnut shaped pockets 481 are formed between the large diameter and the small diameter rims. It is in these pockets that coils encircling the rotational axis x-x are placed to form field windings 482, 486. In addition to the field coil(s), the stator also includes armature coils.
Armature coils 450 are interengaged with slots 483 in the periphery of the large rims 464, 466, 470 such that each armature coil will encircle an imaginary axis y-y that is substantially perpendicular to the axis of rotation x-x (see FIG. 3).
For each stator rim, there is a plurality of mating rotor poles. As can be seen, the peripheral stator rims 464, 470 have axially spaced (x-x) mating rotor pole 462, 468 (shown in solid lines) and the central stator rim 466 has axially adjacent mating rotor poles 463, 469 (shown in broken lines). Rotor poles for adjacent rims (e.g., 462, 463) are not only axially spaced (x-x), but they are also radially spaced such that a rotor pole for one rim is radially spaced by 90 electrical degrees from the closest rotor pole mating with an adjacent rim.
In various embodiments, internal vacuum pumps such as molecular drag pumps provide for moving molecules such as gas molecules away from the flywheel mass 416 and especially away from the flywheel mass periphery where the highest speeds are achieved. U.S. Pat. No. 5,462,402 FLYWHEEL WITH MOLECULAR PUMP is incorporated by reference herein in its entirety and for all purposes including its discussion of molecular drag pumps and their use in flywheel systems.
In an embodiment, a first or radial drag pump 4011 is formed by a first stationery labyrinth like ring 458 supported from the housing wall 434 which is closely spaced with respect to a vacuum pump surface of the flywheel mass 459. In various embodiments grooves in the labyrinth ring provide for a pumping action 1453 in concert with the moving flywheel surface. In some embodiments, the groove is a spiral and in some embodiments the groove has a cross-sectional area that generally decreases along a forward flow path.
And, in some embodiments, a second or outer axial drag pump 4012 is formed by a labyrinth ring and a moving surface at a periphery of the flywheel mass 413; for example, a labyrinth located on or integral with the housing 428 and a periphery of the flywheel mass operating in close proximity to the labyrinth and establishing an evacuating flow 1455 in a direction about perpendicular to the direction of flow established by the first drag pump (peripheral labyrinth not shown). In various embodiments, such an alternative second drag pump is operable with the first drag pump to provide a two-stage drag pump.
In an embodiment, a supply region 467 and an exhaust region 487 are included within the vacuum barrier housing 428. The supply region has a boundary defined at least in part by portions of a vacuum barrier housing, a hub exterior surface 417, and a flywheel mass periphery 413. The exhaust region has a boundary defined at least in part by portions of the vacuum barrier housing and the core assembly 412.
In various embodiments, drag pump(s) include one or both of a) a 4011 first drag pump interposed between a first drag pump surface of the flywheel mass 459 and the second vacuum barrier housing wall 434 and b) a second drag pump 4012 interposed between a second drag pump surface of the flywheel mass 413 and a third vacuum housing wall 473 that is about perpendicular to the second vacuum housing wall. This first drag pump can be referred to as a radial drag pump and the second drag pump can be referred to as an outer axial drag pump.
FIG. 4B shows a second drag pump utilizing a flywheel mass periphery 400B. Here, the second vacuum pump is formed by a second stationery labyrinth ring 475 and a rotatable flywheel peripheral surface 477. The labyrinth ring is coupled to a third housing wall 473. Grooves in the labyrinth ring 476 are similar to those described above. In operation, the flywheel mass peripheral surface moves relative to the labyrinth ring and urges flow in a direction about perpendicular to the direction of flow of the first drag pump.
Multiple drag pumps can operate in parallel between a common supply and exhaust region. They can also be operated in series with one pump's exhaust in fluid communication with another pump's inlet. In the case of a multi-stage drag pump arrangement, flow travels from the second drag pump to the first drag pump. Here, gas in the supply region 467 enters a second pump intake 471 and travels to the second pump exhaust 478. The second pump exhaust and the first pump inlet are fluidly coupled, for example by an interpump space such as a somewhat annular space in an upper corner of the vacuum housing 479. Gas enters the first drag pump inlet 480 from the interpump space and travels to the first drag pump exit 485 where it empties into the exhaust region 487.
In some embodiments, a third or inner axial vacuum pump 4013 for pumping 1457 is formed by a labyrinth similar to the one described above and fixed to peripheral stator parts (such as the large diameter stator rings 454, 464, 466, 470, not shown for clarity) or fixed to geometrically opposed rotor poles (456, 462, 463, 469, 468). This third drag pump can be referred to as an inner axial drag pump. See for example the drag pump 822 of FIG. 8. In various embodiments, combinations of the first, second, and third drag pumps are used in serial and parallel operation.
FIGS. 4C-J show molecular drag pump embodiments 400C-J for use with the electromechanical flywheel of FIG. 1. In particular, the figures show portions of electromechanical flywheel assemblies including a drag pump with means for controlling a drag pump gap.
In electromechanical flywheels utilizing a drag pump, various operations and/or operating conditions may benefit from a means to control a drag pump gap. For example, where control of a gap between moving and stationary drag pump parts enhances electromechanical flywheel operation.
FIG. 4C shows operation of a planar drag pump 4600 with variable geometry in an electromechanical flywheel. Two different operating configurations are shown. At left, a before axial contraction operating state is shown 4602. At right, an after axial contraction operating state is shown 4604.
Main flywheel parts typically include i) an upper support 4612 such as a housing, containment, or lid, ii) a stationary core assembly 4608 which may be supported by the support, and iii) a rotatable assembly 4609 including a flywheel mass and/or a rotor such as a motor-generator rotor 4606 that is rotatable about a central axis 4610.
Drag pump parts typically include a non-rotating part and a rotating part. In the embodiment shown, the non-rotating part is a labyrinth ring or drag pump stator 4607 and the rotating part is the upper end of the flywheel mass or a structure at the upper end of the flywheel mass or drag pump rotor 4616. As seen, these drag pump parts have opposed surfaces that lie in planes that are substantially perpendicular to the centerline 4610 such that a gap g1, p1 exists between the stator and the rotor.
FIG. 4D shows a drag pump labyrinth ring or stator, labyrinth side up. FIG. 4E shows a drag pump labyrinth ring or stator, labyrinth side down. As seen, the ring 4607 has a working surface or annular working surface such as a labyrinth side 4617. The working surface may incorporate channels 4647 between sidewalls 4657 and in some embodiments the channels may follow a generally arc shaped radial path extending between a channel inlet such as a radial channel inlet 4647 and a channel outlet such as a radial channel outlet 4648. The channel cross-sectional area at the inlet may be larger than the channel's corresponding outlet cross-sectional area and transition(s) in size may be generally smooth, for example to improve pumping performance or effectiveness. Notably, channel area variation may be due to channel height changes, channel width changes, or some combination of the two.
As shown in operating configurations 4602 and 4604, the labyrinth ring 4607 has a working surface 4617 facing an upper end of the flywheel mass 4616 such that a gap g1, p1 is provided between the drag pump rotor and the drag pump stator. This gap may be controlled and/or varied through the use of elevator(s) 4700 (see e.g., FIG. 4C) that are coupled at one end to the support 4612 and at another end to a drag pump stator such as the labyrinth ring 4607.
In some embodiments, it may be desirable to maintain a constant gap g1=p1 over some operating range and/or despite changed operating condition(s). As mentioned above, FIG. 4C shows two different operating states. At left, a before axial contraction operating state is shown 4602 and at right, an after axial contraction operating state is shown 4604. These two different operating states result in different drag pump stator locations or elevations that provide a constant gap g1=p1. For an exemplary embodiment, the table below shows a comparison of dimensions for the two states.
















Dimension
State 4602
State 4604
Comparison









Gap (ring face to
g1
p1
g1 = p1



flywheel face)



Elevator length
g2
p2
g2 < p2



(support to ring)



Gap plus ring
g3
p3
g3 = p3



thickness



Height of flywheel
g4
p4
g4 > p4



mass










The table above illustrates one operating mode of the variable geometry drag pump 400C. This operating mode may be useful where a fixed gap g1, p1 is desired but cannot be maintained over a flywheel operating range of interest absent some ability to vary geometry such as location of a drag pump stator relative to a stator support. For example, where drag pump performance depends on maintaining a constant or nearly constant gap between a drag pump rotor and a drag pump stator, variation in flywheel machine speed or temperature may be detrimental to drag pump performance. And, for example, where gap size increases/changes with wheel speed due to centrifugal stress in the flywheel mass which reduces flywheel mass length (see e.g. Poisson's ratio). And, for example, where gap size increases/changes with temperature due to thermal expansion of flywheel machine part(s) such as a housing (see e.g., housing 807).
FIG. 41 shows estimated drag pump pressure ratio variation with drag pump gap 4001. In particular, as gap is diminished, pressure ratio increases and the effectiveness of the pump to move gas molecules is improved.
FIG. 4J shows estimated wheel temperature variation with spin speed 400J. Wheel temperature here refers to a temperature of a flywheel mass (e.g., 4606) while spin speed refers to the angular velocity of the flywheel mass.
In the upper curve without variable drag pump geometry spin speed ranges from near zero to 30 thousand revolutions per minute (krpm) while the wheel temperature ranges from about 30 degrees C. to 150 degrees C.
In the lower curve where variable drag pump geometry maintains a substantially constant drag pump gap, from near zero to 30 krpm the corresponding wheel temperature variation ranges from about 30 degrees C. to about 38 degrees C. As seen here, variable drag pump geometry provides a substantial reduction in wheel temperature rise as wheel speed increases.
Limiting wheel temperature rise has obvious advantages including maintaining the integrity of and limiting the thermal expansion of heat sensitive flywheel mass and rotor components. For example, a carbon composite flywheel mass may be speed limited by rising temperature and the integrity of rotor to flywheel mass interference fit(s) may be jeopardized by rising temperature due, for example, to differences in thermal expansion rates. In an embodiment, a variable geometry drag pump enables use of a carbon composite wheel shrunk onto a metallic rotor in a high speed electromechanical flywheel where the flywheel mass operates in a vacuum.
Because the flywheel mass and rotor operate in an evacuated space which reduces available heat transfer coefficients, a reduction in wheel temperature rise may be essential to obtain desired speeds of operation given available heat removal rates. For example, in an embodiment, a variable geometry drag pump increases allowable operating speed.
Some details of exemplary elevator(s) 4700 will now be discussed in the context of an electromechanical flywheel that maintains a constant drag pump gap despite changed operating condition(s).
As shown in the embodiment of FIG. 4E, a plurality of elevators 4700 is used. For example, where three elevators are used, they may be coupled to the non-working surface 4627 of the labyrinth ring 4607 at spaced apart or regular intervals (e.g., 120 degree intervals). In various embodiments, the elevators may be any of pneumatic, electric motor, gear, magnetic, electromagnetic, or other suitably actuated elevators.
FIGS. 4F-G show radial cross-sections 400E-G taken through a drag pump labyrinth ring 4607 and an elevator 4700 mounted thereon. The elevator is mounted at an upper labyrinth ring surface 4627 opposite the labyrinth working surface 4617. Elevator body to support attachment features 4714 may provide a means for fixing the elevator to a support 4612.
Here, the elevator shown 4700 is an electromagnetically actuated device. In various embodiments it includes one or more of a body 4702, a link 4703, a platen 4704, a base 4705, a base mandrel 4708, a base rim 4712, and an electrical coil 4710. In various embodiments, the body, link, platen, base, base mandrel, base rim, and electrical coil are arranged coaxially about a central axis x3-x3. In various embodiments, these components provide means for moving or lifting the labyrinth ring 4607. Particular embodiments are further described below.
A body mouth 4731 receives the platen 4704 such that the link 4703 passes through the base mandrel 4708 and interconnects with the labyrinth ring 4607. A spring 4733 between the platen and the base 4705 encircles the link 4703 and tends to move or lift the platen away from the base. As the platen and labyrinth ring are interconnected by the link, action of the spring that lifts the platen also lifts the labyrinth ring.
Between the base mandrel 4708 and base rim 4712 is a base grove 4707 that receives the electrical coil 4710 such that the coil 4710 surrounds the mandrel 4708. The base provides magnetic back iron and with the coil forms an electromagnet operable to attract the platen 4704, compress the spring 4733, and lower the labyrinth ring 4607.
Notably, the drag pump gap g1 may be controlled with or without feedback such as feedback from a gap or position sensor. For example, where position feedback is not used for adjusting the drag pump gap, actuator(s) such as elevator(s) 4700 may reposition the labyrinth ring 4607 with changing flywheel mass 4606 angular velocity such that the labyrinth ring moves to adjust or maintain a gap that tends to change (e.g., grow) with speed. In some embodiments, a lookup table or math formula may be used to control the actuator based on one or more of an indication of one or more of flywheel mass angular velocity, flywheel mass temperature, machine vibration, machine acoustic emission, machine electrical input, or machine electrical output.
FIG. 4H shows an enlarged portion 400H of FIG. 4G indicated by dashed lines in FIG. 4G. Among other things, the figure shows selected embodiments that may use loop controls or not, open loop controls with or without the mentioned sensor, and closed loop controls with or without the mentioned sensor. Also shown are selected embodiments utilizing optional multipart links 4703.
Operation of the electromagnet 4705, 4710 may be controlled by, inter alfa, sensing the position of the labyrinth ring 4607 with respect to the upper end of the flywheel mass 4616. Various contact and non-contact sensors may be used such as i) potentiometer, ii) strain gauge, iii) acoustic, iv) electromagnetic wave including radio frequency wave, light wave, and coherent light wave, and v) other suitable sensors known to skilled artisans.
In an embodiment, an electromagnetic wave sensor such as a reflected light sensor 4751 is used. Here, a sensor emission 4761 through an opening or lens 4697 of the labyrinth ring 4607 is reflected 4763 back to a sensor surface 4752 from the flywheel mass upper surface 4616.
In various embodiments, the sensor 4751 is interconnected 4753 via or with a terminal or circuit board 4741 that may be included with the elevator 4700. And in various embodiments, one or more of sensor signal processing, coil 4710 signal processing, and coil power supply are provided by one or more of sensor electronics, circuit board electronics, or other electronics such as flywheel power electronics and controls 106.
In an embodiment, the coil 4710 is operated by a coil controller that receives signals from the sensor 4751. The coil controller provides power to the coil to reposition the labyrinth plate 4607 when sensor signals indicates a gap such as g1 differs from a desired gap such as a predetermined gap. The coil controller may include one or more of circuit board 4741 electronics including a processor and flywheel power electronics and controls 106.
Turning now to embodiments of the link 4703 interconnecting the platen 4704 and the labyrinth ring 4607, the link may be extensible or not. Where the link is made from multiple parts, it may be configured and used to set the gap g1 to an initial value. In various embodiments, this initial gap setting is made when the flywheel mass 4606 is at a standstill.
Multipart links may include variable length link assemblies. As shown, a threaded rod 4770 passes through the base 4705. At a platen central neck 4733, the rod threads engage mating neck threads. At a labyrinth ring 4607 socket 4772, a head 4737 of the rod is rotatably retained. In this configuration, rotation of the rod in a first direction moves the labyrinth ring hanging from the rod closer to the platen 4704 while rotation of the rod in the opposite direction moves the labyrinth ring away from the platen. In some embodiments a nut 4771 threaded onto the rod between the base and the labyrinth ring provides a means for locking the rod against unwanted rotation when the nut is rotated to tightly meet with the base.
In selected embodiments, one or more of the following applies: 1) a gap g1, p1 is maintained in a range of about 20 to 40 mil (1/1000th of an inch) or about 15 to 50 mil; 2) the elevator 4700 fits within a volume of about 2 to 6 cubic inches; 3) the platen 4704 to base 4705 magnetic gap is about 150 mil maximum and about 0 mil minimum; 4) coil power is in a range of about 0 to 15 watts; 5) spring 4733 parameters include about 0.24 OD, about 0.75 inch free length, about 0.17 inch max compression, and about 5.6 lbf/inch spring rate with spring force at minimum compression of about 2.1 lb and spring force at maximum compression of about 3.0 lb; 6) a flywheel mass 4606 height is in the range of about 1 to 6 feet or about 2 to 4 feet; 7) a flywheel 4606 outside diameter is in the range of about 1 to 3 feet; and 7) speed of flywheel mass rotation about axis 4610 is in the range of about 0 to 65,000 revolutions per minute.
FIG. 5A shows a radially staggered arrangement of rotor poles in adjacent pole planes for a 2+2 pole single stage homopolar machine 500A. Referring to rotor cross section 502 and rotor 514, a first pole 462 is located in a first pole plane Y1 and an opposed pole 463 in located in the same plane. In a similarly clocked adjacent pole plane Y2, an adjacent plane pole 465 is between the Y1 plane poles. Not shown in this cross section is the second pole in the Y2 plane 464.
The plane views 504, 506 of the pole planes Y1, Y2 show the poles in each pole plane 462, 463 and 464, 465 are separated by a 90° geometric angle. In this 4 pole embodiment, the poles are similarly separated by 90 electrical degrees.
In various embodiments, a magnetic path extends between adjacent staggered poles. For example, as shown in the pole assemblies 508, 510, magnetic path parts 466, 468 extend between pole pairs 462, 463 and 463, 464. As shown here, two continuous magnetic paths are formed in a 4 pole machine rotor by magnetic path parts 462-466-465 and 463-468-464. In some embodiments, each magnetic path part assembly 462-466-465 and 463-468-464 is “Z” shaped with the central members 466, 468 meeting adjoining members 462, 465 and 463, 464 at substantially right angles. Among other things, this structure preserves the capacity of the magnetic path.
FIG. 5B shows a rotor and a stator for a three stage machine, each stage having four poles 500B. Here, a view of rotor magnetic path part assemblies 560 is shown as if the normally cylindrical rotor structure is “unrolled” such that a planar surface is presented. The magnetic path part assemblies 520, 522, 523, 521 are arranged to create a lattice 569 with spaces between the parts 519, the spaces being filled, in various embodiments, with non-magnetic material(s).
The lattice 569 is constructed such that a plurality of stages A, B, C is formed, each stage having 4 poles. For example, stage A has a North plane with a first full pole 557 and a second pole consisting of two half-poles 553, 555. Stage A also has a South plane with two full poles 559, 561. The North and South planes of Stage A therefore have a total of 4 complete poles.
Each stage includes four magnetic path part assemblies or rotor lattice parts. For example, Stage A includes magnetic path part assemblies 520, 522, 520, and 522; Stage B includes magnetic path part assemblies 523, 521, 523, and 521; and Stage C, like Stage A, includes magnetic path part assemblies 520, 522, 520 and 522. In some embodiments, the path part assembly geometry differs primarily in part orientation when curvature is not considered. Here, for example, assembly 520 differs from assembly 522 by an 180° rotation about an axis parallel to the x-x axis, assembly 520 differs from assembly 523 by an 180° rotation about an axis perpendicular to the x-x axis, and assembly 522 differs from assembly 521 by an 180° rotation about an axis perpendicular to the x-x axis.
Also shown is a cross sectional view of a stator 562. As seen, the stator has large 534, 536, 538, 540 and small 544, 546, 548 diameter rims centered on an x-x axis. First and second large diameter intermediate rims 536, 538 are interposed between large diameter peripheral rims 534, 540. One small diameter rim is interposed between each pair of large diameter rims such that the rims are stacked in an order 534, 544, 536, 546, 538, 548, and 540. The rims are supported by a coupled stator support 532 that is supported via a wall 530.
A plurality of armature windings eg . . . 571, 572 interengage a plurality of the large diameter rim peripheries eg. . . 574 via slots or a similar feature. Field windings 535, 537, 539 encircle the stator axis of rotation x-x with one field winding encircling each of the small diameter rims such that each field winding is between a pair of large diameter rims.
As can be seen, the lattice structure of the rotor 569 is arranged such that the first rim of the stator 534 corresponds to the North poles of stage A; the third rim of the stator 536 corresponds to the South poles of stage A and the South poles of stage B; the fifth rim of the stator corresponds to the North poles of stage B and the North poles of stage C; and, the seventh rim of the stator corresponds to the South poles of stage C.
In various embodiments, bearings are used to support the spinning assembly and the included flywheel mass 116, 316, 416. Any combination of the bearings described herein that is sufficient to support the spinning assembly may be used.
FIG. 6 shows a lower bearing carrier and some related parts 600. As shown in the upper half of the drawing, there is a hub 618 for coupling to a flywheel mass, a support pin 696 for supporting the hub 618, a moving suspension assembly for supporting the hub 692, and a lower bearing carrier 694. The hub, support pin, and moving suspension assembly are fixedly coupled together (shown in FIG. 6 in exploded diagram format for clarity).
In various embodiments, the moving suspension assembly 692 includes a moving suspension assembly electromagnetic bearing rotor 602. In some embodiments, the bearing rotor is a laminated structure (as shown). In some embodiments, the bearing has a moving suspension assembly electromagnetic bearing face 603 oriented at an angle θ1=0° where the angle is defined by the face and an axis x1-x1 parallel to the x-x axis. And, in some embodiments, the bearing has a face 603 oriented at an angle 0<θ1<90° (“angled face”) (as shown) providing electromagnetic bearing force components parallel to the x-x axis and parallel to an axis perpendicular to the x-x axis.
In various embodiments, the moving suspension assembly 692 includes a moving suspension assembly permanent magnet 604 and in some embodiments the permanent magnet is in addition to the electromagnetic bearing rotor 602. And, in some embodiments, a moving suspension assembly magnet holder 606 provides a holder for either or both of the moving suspension assembly electromagnetic bearing rotor and the moving suspension assembly permanent magnet.
When the moving suspension assembly includes an electromagnetic bearing rotor 602, the lower bearing carrier 694 includes a corresponding lower bearing carrier electromagnetic bearing stator 614 and a lower bearing carrier stator electrical coil 616 for magnetizing the stator. The stator is supported by a lower bearing carrier frame 612 which is in turn supported by a housing wall 632.
In some embodiments, the bearing stator is a laminated structure (as shown). In some embodiments, the bearing has a lower bearing carrier electromagnetic bearing face 615 oriented at an angle θ2=0° where the angle is defined by the face and an axis x2-x2 parallel to the x-x axis. And, in some embodiments, the bearing has a face 615 oriented at an angle 0<θ2<90° (“angled face”) (as shown) providing electromagnetic bearing magnetic force components parallel to the x-x axis and parallel to an axis perpendicular to the x-x axis. As will be appreciated by persons of ordinary skill in the art, the bearing faces 603, 615 interoperate such that a straight rotor face is matched with a straight stator face while an angled rotor face is matched with an angled rotor face.
Where a moving suspension assembly permanent magnet is used 604, the lower bearing carrier includes a geometrically opposed permanent magnet 620. In some embodiments a lower bearing carrier permanent magnet holder 619 supported from the lower bearing carrier frame 612 and supporting the permanent magnet.
In various embodiments, the lower bearing carrier 694 includes a lower bearing carrier landing bearing such as an antifriction bearing 622. As shown, the landing bearing is supported from the lower bearing carrier frame 612. In some embodiments, a damping material 624 provides a seating material for the landing bearing.
FIG. 7 shows an upper bearing carrier and some related parts 700. As shown, the upper bearing carrier 790 includes a stationery plate 702 and a moving plate 704.
The stationery plate 702 includes a coil space 706 in the form of a groove is on a side of the stationery plate facing the moving plate 730. An electrical coil 722 for magnetizing a magnetic material surrounded by the coil 707 is included.
The moving plate 704 includes a spring space 708 and a mechanical bearing space 710. The spring space 708 is formed where a reduced diameter section of the moving plate extends to the side of the plate facing the stationery plate 732 and a spring such as a coil spring 720 occupies this space. The bearing space 710 is a central cavity in a moving plate surface 734 opposite the moving plate surface facing the stationery plate 732. As seen, operation of this electromagnet compresses the spring and tends to draw the plates together.
In various embodiments, the upper bearing carrier 790 includes an upper bearing carrier landing bearing such as an antifriction bearing 716. As shown, the landing bearing is positioned in the moving plate cavity 710. In some embodiments, a damping material 718 provides a seating material for the landing bearing.
As seen in FIGS. 6 and 7, the support pin 696 extends between the upper bearing carrier 790 and the lower bearing carrier 694. Further, each of the upper bearing carrier landing bearing 716, support pin 696, moving suspension assembly 692, lower electromagnetic bearing stator 614, lower bearing carrier permanent magnet 620, and lower bearing carrier landing bearing 622 is centered on the x-x axis such that when the moving plate 704 moves toward the lower bearing carrier 793, the support pin upper and lower ends 728, 628 are engaged with respective upper and lower landing bearings 716, 622 and a central aperture of each landing bearing 726, 626.
FIG. 8 shows another embodiment of an electromechanical flywheel 800. A flywheel mass 831 surrounds and is coupled to a homopolar motor-generator rotor including a metallic liner 830. As shown, the rotor includes rotor North rotor poles 824, 832. Not shown are the South rotor poles; see stages A and B of FIG. 5B for a similar arrangement that locates the South rotor poles.
A stator support 811 is coupled to a motor-generator stator 828 and each of field windings 826 and armature windings 820 are interengaged with the stator in a manner similar to that described above.
Supporting the rotor 830 and flywheel mass 831 is a hub 846 that is in turn supported by a support pin 864 engaging and/or located between upper and lower bearing carriers 860, 862. See FIGS. 6 and 7 for details of similar bearing carriers. A first electromagnetic bearing 866 is located in the lower bearing carrier. A second electromagnetic bearing 870 is spaced apart from the first and second bearing carriers and includes a bearing stator 818, a bearing rotor 818 and stator coils 814 for magnetizing the stator.
An electromechanical flywheel housing includes an inner vacuum barrier 812. In some embodiments, an outer housing 807 supports the vacuum barrier. Suitable vacuum barrier materials include stainless steel and other materials known by skilled artisans to be suited to this purpose.
In various embodiments, the stator support 811 has a tubular structure and a coaxial tube 801 is located therein. As shown, the coaxial tube envelops a liquid coolant flow entering the stator support 802 and an annulus between the support structure inside diameter and the coaxial tube outside diameter 815 provides a flow path for coolant leaving the stator support 803. Coolant traveling through the annulus absorbs heat from the stator 828 and is in various embodiments cooled in a cooler (not shown) before it is pumped (not shown) back into the flow entry 802.
Heat pipes 808 provide stator cooling in some embodiments. As shown, each of a plurality of heat pipes has a heat absorbing first end in close proximity to the stator, such as in the stator armature winding slots (as shown) 872. The heat rejecting end of the heat pipe is in close proximity to the vacuum barrier, such as in contact with vacuum barrier (as shown) 874 or in other embodiments cooled by the above mentioned liquid coolant flow.
As discussed in connection with FIG. 4A and FIG. 4B, a drag pump utilizes stationery and moving surfaces operating in close proximity. As shown in FIG. 8, an inner axial drag pump is formed by a labyrinth similar to those described above and coupled to peripheral stator parts such as the large diameter stator rings 824, 828, 832 or fixed to geometrically opposed rotor poles 824, 828, 832. For example, where the labyrinth is coupled to the stator, an adjacent moving surface is provided by the opposed rotor poles that move with the flywheel mass 831.
Embodiments of the evacuation system described above, including embodiments discussed in connection with FIG. 4 and FIG. 8, are augmented with gas removal trains with pumps. The gas removal trains are external to the vacuum barrier housing 428. For example one or more pumps can be arranged in series or in parallel to take suction from a vacuum barrier housing exhaust port 489 in fluid communication with the vacuum barrier housing exhaust region 487.
FIG. 9A shows a first external pumping system with a branch gas removal device 900A. A manifold 902 and a branch 911 fluidly couple the exhaust port 489 with a gas removal device 906. A pumping system valve 908 is fluidly coupled to a mechanical vacuum pump 910 by a passageway 909. The pumping system valve provides manifold isolation from a downstream connection or vent 912. In various embodiments, a mechanical vacuum pump 910 is located downstream of the isolation valve. And, in some embodiments, a pressure sensor 904 is provided for manual viewing and/or automated operation. For example, a pressure feedback signal and/or controller 920 are used in some embodiments to operate the vacuum pump 910 when the sensed pressure is higher than a threshold vacuum level.
FIG. 9B shows a first gas removal device 900B. Embodiments of the gas removal device 906 include a housing or casing 913 with multiple chambers 912, 914 holding a plurality of pumps. In various embodiments, a gas removal device inlet 911 provides access to a getter type pump 925 in a first chamber that is separated from a sieve type pump 923 in a second chamber, the chambers being separated by a gas permeable structure 915 such as a perforated wall.
As is further discussed below, heating getter and sieve materials provides for enhanced activity and/or regeneration. An optional getter heater 916 and/or an optional sieve heater 918 with a corresponding control(s) and/or power supply(s) 917 provides this functionality. In some embodiments, the control 917 receives feedback from the pressure sensor 904 such that heater operation is a function of and/or influenced by pressure sensor measurements.
Flywheel machines with composite flywheel masses often evolve gasses including primarily water vapor and to a lesser extent hydrocarbons and other active gasses. Molecular sieves typically provide a majority of water vapor removal while getters typically provide a majority of active gas removal.
As persons of ordinary skill in the art will understand, getters provide for removal of gasses and in particular for removal of many active and inactive gasses other than water vapor. A getter is a deposit of reactive material placed inside a vacuum system, for completing and maintaining the vacuum. Gas molecules that strike the getter material combine with it chemically or by adsorption.
In flywheel systems designed to be exposed to air during maintenance, nonevaporative getters provide a getter pump solution. These getters work at high temperature and often consist of or include a special alloy such as zirconium. A desirable feature is that the alloy material(s) form a passivation layer at room temperature which disappears when heated. Common alloys have names of the form St (Stabil) followed by a number: St 707 is 70% zirconium, 4.6% vanadium and the balance iron, St 787 is 80.8% zirconium, 14.2% cobalt and balance mischmetal, St 101 is 84% zirconium and 16% aluminum. Heating these getter materials typically enhances their activity so they should not be heated if the system is not already in a good vacuum.
Sieves and in particular molecular sieves incorporate a material containing tiny pores of a precise and uniform size that is used as an adsorbent for gases and liquids. Molecules small enough to pass through the pores are adsorbed while larger molecules are not. It is different from a common filter in that it operates on a molecular level and traps the adsorbed substance. For instance, a water molecule may be small enough to pass through the pores while larger molecules are not, so water is forced into the pores which act as a trap for the penetrating water molecules, which are retained within the pores. Because of this, they often function as a desiccant. Often they consist of aluminosilicate minerals, clays, porous glasses, microporous charcoals, zeolites, active carbons, or synthetic compounds that have open structures through which small molecules, such as nitrogen and water can diffuse. Calcium oxide is a frequently used dessicant material.
Methods for regeneration of molecular sieves include heating under high vacuum. Temperatures typically used to regenerate water-adsorbed molecular sieves range from 130 ° C. to 250 ° C. Additional information on pumps including mechanical vacuum pumps, getter pumps, and sieve pumps can be found in U.S. Pat. No. 6,884,039 to Woodard et al.
FIG. 9C shows a second external pumping system with an in-line gas removal system 900C. A manifold 932 fluidly couples the exhaust port 489 with a first isolation valve 933 and a first passageway 935 couples the valve and a gas removal device 936. In the first passageway and downstream of the isolation valve is a pressure sensor 934. A mechanical vacuum pump 940 provides suction to the gas removal device via a second isolation valve 938 that is coupled therebetween via second and third passageways 937, 939. A mechanical vacuum pump exhaust is coupled to a connection or vented 942. In various embodiments, the pressure sensor 934 is provided for manual viewing and/or automated operation via a pressure feedback signal and/or controller 922 for operating the vacuum pump. For example, a pressure feedback signal and/or controller 922 are used in some embodiments to operate the vacuum pump 940 when the sensed pressure is higher than a vacuum pressure threshold level.
FIG. 9D shows a second gas removal device 900D. Embodiments of the gas removal device 936 include a housing 950 with multiple chambers 954, 956 holding a plurality of pumps. In various embodiments, a gas removal device inlet 955 provides access to a getter type pump 947 in a first chamber. The first chamber is separated from a sieve type pump 945 in a second chamber, the chambers being separated by a permeable structure 953 such as a perforated wall. Gas therefore enters through the getter chamber 954 and exits, via a gas removal device outlet 957, after crossing the permeable structure and sieve chamber.
An optional getter heater 916 and/or an optional sieve heater 918 with a corresponding control(s) and/or power supply(s) 917 provides this functionality. In some embodiments, the control 917 receives feedback from the pressure sensor 934.
FIG. 9E shows a third external pumping system with an in-line gas removal system 900E. A manifold 972 fluidly couples the exhaust port 489 with a first isolation valve 973 and a first passageway 975 couples the valve and a gas removal device 976. A mechanical vacuum pump 980 provides suction to the gas removal device via a second isolation valve 978 that is coupled therebetween via second and third passageways 977, 979. A second pressure sensor 971 is fluidly coupled to the second passageway and a mechanical vacuum pump exhaust is coupled to a connection or vented 982.
A first signal line 984 couples the first pressure sensor 974 and a controller 917. A second signal line 986 couples the second pressure sensor 971 and the controller. A third signal line 924 couples the controller and the mechanical vacuum pump. In various embodiments, a pressure sensor signal, such as a signal from the first pressure sensor 984, is provided to the controller 917 and a controller control signal 924 is provided in turn for operating the mechanical vacuum pump when the sensed pressure exceeds a threshold vacuum pressure.
Embodiments of the gas removal device 976 include a housing 990 with multiple chambers 994, 996 holding a plurality of pumps. In various embodiments, a gas removal device inlet 995 provides access to a getter type pump 985 in a first chamber. The first chamber is separated from a sieve type pump 987 in a second chamber, the chambers being separated by a permeable structure 993 such as a perforated wall. Gas therefore enters through the getter chamber 994 and exits, via a gas removal device outlet 997, after crossing the permeable structure and sieve chamber.
A sieve heater 918 with a corresponding control and power supply 917 provides this functionality in accordance with feedback from each of the pressure sensors 974 and 971. Notably, either of the pressure sensors might be used to sense a pressure at the exhaust port 489 while isolation valve 973 is open. In some embodiments, reversal of the position in the passageway 975 of the first pressure sensor 973 and isolation valve 973 provides for exhaust port pressure sensing irrespective of the isolation valve being open or closed. In addition to redundancy, an added benefit of having pressure sensors to either side of the gas removal device 976 is measuring pressure drop across this device. Pressure drop information can be used to influence sieve heater control operation, rising differential pressures indicating an increasing need to operate the heater.
While the above gas removal device heaters for sieves and getters are schematically depicted as heaters within a respective pump chamber, skilled artisans will appreciate that embodiments having external heaters such as coils wrapping around a chamber could also be used.
In various embodiments, initial evacuation of the vacuum barrier housing is followed by operation of a gas removal device 906, 936, 976 as described above. Rising pressure at the exhaust port 489 indicates leaks and/or outgassing of parts exposed to the vacuum. When the pressure rises to a vacuum threshold level determined by flywheel design parameters such as flywheel mass temperature limits, the mechanical vacuum pump is operated and the passageway coupling the pump and the exhaust port 489 is opened to evacuate the vacuum barrier housing 428.
In various embodiments, the sieve heater 918 is operated when one or more of rising exhaust port 489 pressure, sieve age, time since the last sieve regeneration, and operating time since the last sieve regeneration are used to signal sieve regeneration by operation of the sieve heater. Sieve regeneration typically requires blocking the exhaust port 489 with an isolation valve between the port and the gas removal device 906, 936, 976. When this is done, sieve regeneration is accomplished by heating the sieve and by operation of the mechanical vacuum pump while isolation valves interposed between the mechanical pump and the gas removal device are open.
In various embodiments, the getter heater 916 is operated to regenerate the getter in a manner similar to that described for the sieve heater above. And in various embodiments, the getter heater 916 is operated while the exhaust port 489 is in fluid communication with the getter because getter heating improves getter performance.
In operation, a flywheel mass of the electromechanical flywheel is accelerated by the motor-generator during flywheel charging. During charging, energy is transferred to the motor-generator. During discharge, the motor-generator converts the kinetic energy of the flywheel into electrical energy as the flywheel mass is decelerated. Power electronics provide for conversion of network electric power in order to motor the motor-generator and the mechanically coupled flywheel mass. Power electronics also provide for conversion of motor-generator generated electric power into a waveform suited for use by the electrical network to which the electric power is transferred.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to those skilled in the art that various changes in the form and details can be made without departing from the spirit and scope of the invention. As such, the breadth and scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and equivalents thereof.

## Claims

1. An electromechanical flywheel with a molecular drag pump comprising:
a cylindrical motor-generator rotor surrounding a motor-generator stator;
the motor-generator rotor encircled by and fixed to a cylindrical flywheel mass;
a central axis about which the motor-generator rotor and flywheel mass rotate;
a planar drag pump including a labyrinth ring with an annular working surface;
the working surface in a plane about perpendicular to the central axis and centered on the central axis;
the working surface spaced apart from an end surface of the flywheel mass by a drag pump gap; and,
an elevator that moves the working surface toward the flywheel mass end surface when the gap is larger than a first selected dimension and that moves the working surface away from the flywheel mass end surface when the gap is smaller than a second selected dimension.

2. The electromechanical flywheel of claim 1 wherein the labyrinth ring is located between the flywheel mass end surface and an elevator support located above the flywheel mass end surface.

3. The electromechanical flywheel of claim 2 wherein three elevators are equally spaced around a circumference of the labyrinth ring.

4. The electromechanical flywheel of claim 1 wherein the elevator includes an electromagnetic actuator, the actuator comprising an electrical coil surrounding a back iron arranged to magnetically attract a platen coupled via a link to the labyrinth ring for adjusting the gap.

5. The electromechanical flywheel of claim 4 wherein the link passes through a hole centrally located in the back iron.

6. The electromechanical flywheel of claim 5 wherein the elevator includes a spring that encircles the link and urges the platen away from the back iron for increasing the gap.

7. In an electromechanical flywheel with a molecular drag pump, a method of moving a gas from a flywheel mass periphery toward a flywheel mass axis of rotation, the method comprising the steps of:
providing a cylindrical flywheel mass for rotation about a central flywheel axis;
forming a planar drag pump including an annular labyrinth ring that spaced apart from an end of the flywheel mass by a drag pump gap;
during operation of the drag pump, moving the gas along a gas path including a first path portion with a first path direction followed by a second path portion with a second path direction;
wherein the first path portion is a space encircling the flywheel mass and the first path direction is parallel to the axis; and,
wherein the second path portion is a space that does not encircle the flywheel mass and the second path direction is perpendicular to the axis.

8. The method of claim 7 further comprising the steps of:
providing a labyrinth ring elevator;
for increasing flywheel mass angular speeds, compensating for flywheel mass contraction by moving the labyrinth ring toward the flywheel mass end to maintain a substantially constant drag pump gap; and,
for decreasing flywheel mass angular speeds, compensating for flywheel mass expansion by moving the labyrinth ring away from the flywheel mass to maintain a substantially constant drag pump gap.

9. In an electromechanical flywheel, a method of configuring rotating parts that is enabled by a variable geometry drag pump, the method comprising the steps of:
providing a flywheel mass made from a carbon composite;
providing a rotor made from a metal;
encircling the rotor with the mass;
engaging the rotor and the mass via an interference fit therebetween;
providing a variable geometry planar drag pump with a drag pump gap between a labyrinth ring and an end of the flywheel mass; and,
during variable speed operation of the flywheel mass in an evacuated space, controlling the drag pump gap to limit the temperature rise of the flywheel mass.

10. The method of claim 9 wherein the labyrinth ring lies in a plane perpendicular to a flywheel mass axis of rotation and three electromagnetic elevators provide for moving the ring along the axis.

11. The method of claim 9 wherein the labyrinth ring moves to adjust the drag pump gap in response to angular velocity of the flywheel mass.

12. The method of claim 9 wherein the labyrinth ring moves to adjust the drag pump gap in response to a sensor measurement that indicates the gap.