GB2491675A - A pseudo-levitation permanent magnet bearing and drive system for large flywheel energy storage - Google Patents

Abstract

A pseudo-levitation permanent magnet repulsive bearing and drive system arrangement 1, 2, 3, 15 & 16 for a large diameter, hollow centre composite flywheel 18 for multi megawatt hours energy storage. The magnets are positioned in a frustrated cone to assist in centralising the running axis. The levitation system functions utilising multiple concentric rings 13 of prime numbers of repulsive permanent magnets. Diaphragms 19, which deflect vertically and radially in concert with the flywheel 18 as it speeds up, transmit torque between flywheel 18 and the drive system via a central drive shaft 55 which rotates within active magnetic bearings or other bearing types. The lower fixed magnet arrays 26 are elongated such that the cylindrical rotating magnets do not overhang at either end of the fixed magnet as the flywheel 18 expands due to centrifugal force.

Description

Large flywheel pseudo levitation bearing and drive system Wackgrgund To date the most commonly used technology for large electrical energy storage is pumped storage and historically it has been a dependable source of storage.

However they are: * Very capital intensive * Geographically limited to suitable mountainous areas or sea cliffs * Generally far from major centres of population and need o Long planning cycle o Long construction lead time * Environmental Opposition (Areas of Outstanding Natural Beauty. (AONB)) * Generally minimum parasitic storage losses except in hot dry climates due to evaporation, Other competing Technologies CAES (Compressed Air Energy Storage.) Multiple types of Batteries Ultra Capacitors How is this flywheel storage technology applied Today there is much focus on renewable energy, most common of which is wind energy and large GW of capacity have been and are being installed, with even more in planning. This power source of course varies from zero to a maximum according to the cubic factor of wind velocity and averages only about 30% of the rated capacity.

This is one major area where energy storage can play a part.

The second area where energy storage can and does play a part is in the management of the National Grid and Distribution systems. This can involve peak demand sustenance and load levelling for examples.

A third area for storage is to raise the night time generating levels to sustain the recharging of the energy, which has the effect of possibly reducing the total generating capacity needed and removing the thermal cycling modes of plants especially those taken off-line during the night and extending their life cycles as a result.

History of Large Flywheels for electrical storage Steel has been used for various flywheels for electrical storage for some time.

Notable examples are: The flywheels at Culharn Laboratory: very large diameter segmented steel construction, low speed, and large power output for seconds to support the local grid on start-up of the collider.

Fuji Electric in Japan in the SO's constructed a 6.6m diameter flywheel from thick steel machined plates, stacked in layers, giving a total weight of 650 tons and capable of 160MW for 30 seconds.

Current flywheel technology is focussed on very high speed carbon fibre epoxy composite cylinders, running with active and passive magnetic bearings in a vacuum / containment chamber. However their storage capacity is relatively small and their current applications are around fine tuning grid frequency control. Beacon is perhaps the best known as a manufacturer of such devices. These are all manufactured in a factory environment.

$.Ptement of Invention A large flywheel is suspended in air, vacuum or suitable gas by a prime number of concentric rows of opposing large prime numbers of permanent magnets in repulsive mode, arranged in a frustrated cone beneath the flywheel, giving pseudo-levitation and centralising properties all the while keeping any frictional losses, vertical bounce and wobble to a minimum, driving a central shaft by the means of flexible diaphragms attached to internal flanges or other means on the flywheel winding spool and also attached to the central drive shaft by suitable means, and said shaft is mounted in active magnetic or mechanical bearings, both thrust and journal, driving a magnetic coupling / gearbox to provide a hermetical seal against vacuum leakage, to external shaft on exterior of containment / vacuum vessel.

There is a limit to size that can be transported in terms of weight, height arid diameter.

In the UK practical limits of size would be 6m diameter and Sm high on a special low trailer as a permitted load on a motorway / dual carriageway.

1. In energy storage angular velocity is more important than mass, which drives the carbon fibre I epoxy solution or other high strength fibre / resin combination.

To make this viable in terms of size and cost, a large diameter thick wall cylinder has to be manufactured.

2. The practical way to achieve this is to manufacture the flywheel on site in a controlled environment, where curing and winding are continuous processes.

(Application GIll 109721.9) 3. Practically the axis of rotation would have to be vertical. This enables the use of permanent magnets in repulsive mode to elevate the flywheel from beneath, which has a large surface area to contain all the necessary magnets and enable an almost frictionless bearing solution which is maintenance free.

4. There is the issue that magnets in such a mode cause the rotating mass to be unstable, according to Earnshaw and others. This can be ameliorated by mechanical means and the use of prime numbers and is known as pseudo-levitation. Final stabilising is performed by active magnetic bearings on the final drive shaft.

5. The magnets are arranged in a frustrated cone, which assists in stabilising the flywheel at rest and in motion.

6. Magnets in repulsive mode can be demonstrated in graphical form, showing a high force at zero air gap, dissipating to a steady level as the air gap increases.

For best properties and practicality the intent will be to have an air gap of approximately 5mm.

7. The complete flywheel assembly must ran in a near perfect vacuum to minimise parasitic losses. For example the proposed rim speed is Mach 3. The vacuum chamber / containment system proposed is steel with a steel lid. For the extremely large units segmented steel can be bolted and/or welded together on site. Alternately a concrete design could be used. Any concrete porosity issues and vacuum loss can be solved by detecting leaks with foam on the exterior and sealing with liquid epoxy at locations under vacuum where foam quickly disappears, indicating a leak. The two part epoxy will migrate into the concrete, cure and seal the ingress leakage path. Concrete construction would also utilize dumbbell waterbars of rubber, used vertically between each separate pour for additional ingress sealing.

8. The containment chamber does not have to be as robust as if steel for example were used in the flywheel construction. Carbon fibre / epoxy and other composite mixes have the beneficial property that on failing they will delaminate and break into small pieces.

9. The design uses a completely hermetically sealed chamber by means of a magnetic drive system through the lid of the containment I vacuum vessel. So sealing is not an issue.

10. The effect of Precession torque from the earth's rotation on bearing design is important.

11. Critical speeds especially in the normal running range of 30 -100% angular velocity should be designed out.

12, In emergencies, for this proposal SOLAS (Safety of lives at sea.) technology is deemed best spraying a water based fog into the containnent vessel and venting it through automatic or spring closed doors in the lid of the containment vessel.

13. A limited torque coupling is fined between generator and drive system to prevent damage to drive train from grid disturbances.

Proposed technical specification

(But NOT limited to.) * Weight 300 ton * Outer diameter circa 10 metres * Inner diameter circa 6 metres * Height 5 metres * Speed <3042 RPM * 60 MWhr total storage. Useable storage 48 MWhr, e.g. 6 MW output for 8 hours.

* 4 pole 6 MW synchronous machine, running at synchronous speed, generating at 11kV typically or according to site specification and 50 or 60 Hz.

* Hydraulic, magnetic variable speed or hydrodynamic gearbox drive with output of constant synchronous speed.

* Low Voltage Ride Through technology by above drive systems.

Advantages 1) Can be located next to major usage centres 2) Can lower the peak power being dispatched from whatever source to give lower transmission / distribution losses 3) Could be used to eliminate increasing ratings on transmission I distribution systems 4) Very low parasitic losses -estimated at <1% per hour 5) Synchronous generator running at synchronous speed 6) Flywheel over speed almost impossible, with dual back-up controls.

7) Almost perfect wave form (No power electronics) 8) Will meet all Grid Codes for synchronous machines 9) Can be used as synchronous condenser, when not in use (Discharging or recharging) 10) Simplistic design, each component has its own function e.g. stator winding cooling in a vacuum is not an issue! 11) Does not require major geographical features for operation. No need for sites with suitable storage areas and large elevation between for pumped storage (Mountains or sea cliffs) 12) No need for salt cavern storage CAES system. Strategically in UK, better used to store natural gas 13) Lowers the thermal cycling of aging power plants which is costly 14) Enhances the value of renewable energy 15) Raises productivity of existing distribution / transmission systems 16) Improves security of infrastructure 17) Short lead times for equipment.

18) Life expectancy almost independent of frequency or depth of discharge recharge cycle.

19) Commodity Storage: Storing energy generated off peak or from surplus "Green energy" for use during peak demand periods during the day, permitting arbitraging the production price of the periods and a more uniform system load factor for transmission, distribution and generation.

20) Rapid grid connection / disconnection in a fraction of a second, possible.

21) With small standby generator or UPS for controls, "Black Start" is also possible.

22) Fits well with National Grid uncertainty forecast 4 -6 hours out.

23) Could fulfil short term operating reserves, where UK has a big shortfall for 2020.

24) CCS: Facilitate optimal practices for Carbon Capture and Storage.

25) End of life disposal: No major environmental impact. (Especially compared to battery disposal.) Efficiency This is a key measurement and can also define the market best suited to the overall efficiency and especially parasitic losses during storage periods.

Generator 4 pole, 98% efficiency at >0.95pf Hydraulic or hydrodynamic or magnetic variable speed drive system, 95-97%

S

Magnetic gearbox used as hermetic seal, 98.5% efficient Step-up / down transformer 98.5% efficiency (11kV! 66kV) Power in 10% losses Power out 10% losses 1. Overall 20% losses * Compared to pumped storage 20-25% losses * No parasitic losses on pumped storage during non-operation. (Exception -evaporation) 2. Parasitic losses are due to: * Minor losses in standard bearings on centre shaft and / or magnetic bearings * Some windage and friction as vacuum is not absolute zero * Magnet iron losses when gearbox acts as clutch * Mechanical damping losses * Losses estimated at <1% per hour

Introduction to drawing

The following drawings describe the aspects of the invention: Figure 1 shows a cross-section of flywheel with levitating bearings.

Figure 2 shows the frustrated cone angle and the relative force diagram.

Figure 3 shows a plan of the magnet layout.

Figure 4 shows the drive train arrangement, flywheel to exterior.

Figure 5 shows a plan and an elevation of fixed magnet segment.

Figure 6 shows a section through flywheel, magnet segments and spool.

Figure 7 shows a typical repulsive force versus air gap graph.

Figures 8-11 show different methods of fixing diaphragm to spool.

Figure 12 shows a method of improving stability at starting.

Figure 13 shows how the design can be extended radially inwards.

Figure 14 shows the magnet pocket and flux shielding.

Description:

It is well documented that passive permanent magnetic bearings are unstable. This application demonstrates a flywheel bearing system with active magnetic stabilising drive shaft bearings in the preferred embodiment, capable of working in harmony between repulsive bearing design for elevating permanent magnet bearing system, (pseudo-levitation,) and other bearing systems, for very large hollow cylindrical flywheels. The drive means from flywheel to centre drive shaft is accomplished by means of a diaphragm, which expands in harmony with the flywheel.

Figure 1.

The elevating permanent magnets forming the main portion of the arrangement are arranged in concentric rings on a hollow frustrated cone #1. The lower set #2 is stationary and upper set #3 is integral with the flywheel, #14. The magnets are orientated to the surfaces of the frustrated cone, such that a percentage of the total repulsive force available is directed to stabilising action in the horizontal plane.

Figure 2.

The purpose is two fold: 1. The elevating force included angle #4 of the cone, acts as a centralising device and an elevating device combined.

2. It also acts as an additional force #5 to the centrifugal force of the upper rotating magnet array, #3. The repulsive force is shown by #6, elevating force by #7 and addition to centrifugal force #5.

Reviewing the stability of the basic arrangement: Figure 3.

As opposing magnets pass each other, the repulsive force varies as the upper and lower magnets rotate past each other. If not corrected this would lead to a vertical vibration being set-up. To minimise this effect, a prime number of concentric rings, #13, (Only 2 rings illustrated for simplicity.) each comprising of a large and different prime number of magnets in each opposing ring is constructed. For example a top ring of magnets could have a number such as 283 magnets and lower stationary opposing ring could have same 283 magnets. To further this effect the lower ring could have a different prime number such as 293. This also minimises any cogging effect due to the selection of prime numbers and their attributes.

Thus it is preferable to have a prime number of concentric rings of magnets, such as ii, with the "start" position, #8 & #9, or location of exact matching of a pair of magnets on each ring, displaced by 360 Degrees divided by the prime number of rings, such as 11 already suggested, shown by angle #12.

Note: For simplicity only 2 concentric rings of magnets are shown on Figure 3. More concentric magnet rings of differing prime numbers assist with stability and minimises notching or cogging.

#s 8, 9, 10 & 11 represent fixed or lower magnets, #30, in 4 locations only. #13 shows the illustrated two concentric rings of rotating magnets, #46, on the top array.

Dotted lines, #54, represent the ID & OD of the rotating magnetic array at hill speed.

#20 represents a radial version of the hermetically sealed magnetic coupling / gearbox.

Horizontal plane: In this plane the frustrated cone magnet mounts act as a correction agent. If the vertical axis shifts, Figure 1, #18, as shown by arrows, then the air gap, #15 on one side will decrease and on the opposite side, #16 will increase. This immediately generates correcting repulsive forces as these forces are an exponential function of the air gap. Hence the magnets arranged in a cone will be part self correcting in this aspect. Full correction is achieved by the active magnetic shaft bearings, #21 & 24.

Wobble movement: Since there is only constraint magnetically at the base of the flywheel, the ratio of height of the hollow cylinder and the maximum diameter will have an effect. For example if a ratio of 1:1 was used then this effect will be much more pronounced and difficult to control as the centre of gravity is elevated. A ratio of < 0.5 would be desirable. However the change of air gap, #1 5& 16, in a "wobble" situation due to the large diameters of the elevating magnet rings and their placement across the width of the flywheel section, means that even in a wobble situation due to magnets in a frustum conical layout a "wobble" will produce a change in air gap across the elevating magnets on both sides, leading to partial corrective forces being applied.

Full correction is achieved by the active magnetic shaft bearings, #21 & 24.

Flywheel expansion due to centrifugal forces: As the flywheel speeds up it expands and if the same size / surface area of magnets were used in top and bottom magnet ring arrays, then a change in repulsive forces would result as only partial overlap would occur at hill speed. (Assuming alignment at no speed.). This is overcome by using a rectangular magnet, #30, on fixed bottom array and a square or cylindrical one, #46, of the same or similar circumferential width on the rotating top array, such that the top magnet is always in full repulsive mode when passing over bottom fixed magnets. See Figure 3, #8, 9, 10 & 11.

it would also improve any "cogging" effect if the upper magnet, #46, were round I cylindrical; so that as magnets passed each other, the elevating forces are smoothed and not abruptly engaged in a notching format.

Stability in general: In repulsive mode the primary instability emanates from two primary directions, due to design.

Radial -My top magnet, #46, must remain radially within the confines of the surface area of the fixed bottom magnet, #30. This constrains the repulsive forces to being primarily between the magnet faces with no radial force segment. To achieve this, the fixed or lower magnets, #30, should always radially overhang the rotating magnets, #46, to maintain radial equilibrium in the event of excessive radial movement. To best stabilise flywheel at rest to assist active magnetic bearings on start-up, one rotating concentric row of magnets, #13 may partially, radially inwards, overhang the stationary opposing concentric ring of rectangular magnets, #11, and the radial repulsive forces thus generated will concentrically stabilize the position of the flywheel, #14.

Circumferential -Instability is taking place as magnets pass each other, ameliorated by the multiple offset prime numbers of other magnet concentric arrays. The more concentric arrays of magnets will better smooth rotational motion and reduce starting torque and cogging.

Factors governing flywheel size Maximum mass of flywheel to be supported is determined by: * Grade of permanent magnets employed * Air gap between opposing magnets * Number of circumferential rings and radial clearance between rings on radial width of flywheel * Magnet pitch on circumferential rings * Selected frustrated cone angle * Capability of flywheel winding to constrain magnet centrifugal force * Ability to extend radially inwards under the winding spool * Optimal sizing of magnets to fit best with above Drive arrangement: The drive arrangement as well as stabilising has also to accomplish the following: The diaphragms, Figure 4, #19 from the flywheel to the centre shaft, #55, have to expand radially and axially down as the flywheel, #18, runs up to its running speed, due to the elevating magnets being designed in a frustrated cone. This is represented by Figure 4, #15 and the relative horizontal and vertical portions by #16 & #36 respectively. This vertical movement will be a direct function of the frustrated cone included angle, Figure 2, #4 and the expansion due to centrifugal force.

The OD of diaphragms #19 are firmly fixed to IL) of flywheel flanges #23 by a combination of special lightweight bolts through flange holes, #23 and or adhesive, See also Figures 8 -11. For increased stability there are two diaphragms, one near top, #56 and one near bottom, #57, of flywheel winding spool #44. The ID of the diaphragm, #19, is fastened to shaft flanges, #17, by means of fasteners and back-up ring.

The diaphragms, #19, when system is at rest will experience some stress loading due to the active magnetic shaft bearings, #21 & #24, being deflected radially against bearing movement stops or auxiliary bearing radial limit. In practice the maximum radial movement is also constrained by the cone angle, #4, and air gap, ft's 15 & 16.

For example if air gap is 5mm and included cone angle is 130 Degrees, maximum deflection could be = 5/Sin(( 180-130)/2) = 11.8mm. Thus the net horizontal forces due to cone angle, #4, will retain flywheel, #14, at rest, close to centre of rotation.

Since the vertical deflection, which is proportional to the radial expansion and thus subject to an exponential law with regards to rotational speed, then there may be an advantage in preloading the diaphragms, #19, axially at lower speeds and having least load (Thrust bearing load,) at higher speeds. This will assist in thrust bearing, #24, life or in size reduction.

It is also possible that suitably designed diaphragms, #19, could support drive shaft assembly, #55, axially without the need for a thrust bearing in the bottom magnetic bearing assembly #24.

The rotating drive shaft, #55, is mounted, by means of active magnetic bearings, #21 & #24, affixed to the containment / vacuum vessel lid underside at the top location, #37, and to the tank base or foundation for the lower bearing, ft 28. The key factor in the design of the active magnetic bearings, ft's 21 & 24, is the centralising effect of the frustrated cone layout both at rest and in rotation.

The final drive shaft I magnetic gearbox I coupling I hermetical seal is shown as #20 for illustration. This device can be fitted with a clutch to lower parasitic losses during storage by reducing gearbox losses.

Manufacturing of magnet arrays: Figure 5 shows the fixed elevating magnet bearing array segment, #29, in plan and section. #29 is precision aligned, centralised, levelled / shimmed and grouted to foundation or machined base, #28 and bolted, #25, via 3 or more extensions, #27, part of #29 into the foundation. #25 should be Rotabolt or similar, so that initial bolt stretching is easily achieved and easily checked at maintenance intervals.

The magnet arrays, #26 & #39 are made up of segments. Due to the large prime numbers of magnets used, #30 & #46, there is no need for these to be a prime number of segments. These magnet location sockets being a prime number means that each segment has to be uniquely identified, machined and located. Segments should abut so that magnets can abridge, #32, between the segments and maintaining uniform spacing to match the prime numbers of magnets chosen. (This will necessitate careful machine tool programming and tracking.) The pockets follow a curved path, #33, based on centre of rotation.

To prevent the possibility of eddy currents, the segmented arrays should be made of non-conducting material, at least in the area around the magnets, The magnets could be mounted on a machined fibre / epoxy composite, #26, or other material blends of a similar nature. For machining purposes, a fibre such as Kelvar is preferable. This could form the complete mounting or perhaps only the top of the mounting, #26, to insulate the conductive part magnetically. The purpose is to eliminate eddy currents and maximise system efficiency. #29 could even be a non magnetic east iron or other non magnetic metal casting or fabrication since it is stationary.

Magnetic shielding can be achieved by the use of magnetic screening material such as Mu Metal or iron or other material / method, known to those skilled in the art.

My combination of materials, #26 & 29, would have to be carefully joined for a permanent and robust solution.

Figure 6 shows how the rotating, #39, and fixed, #26, magnet arrays abut each other in vertical plane. #26 is shown in dotted outline only. They are separated by air gap, #15. #39 would preferably be a Glass Reinforced Plastic casting to match closely the mechanical properties and density of the flywheel material to minimise the centrifugal forces to be constrained by the flywheel composite winding caused by the rotating magnets, #46. This too may have a magnetic insulating surface section, #41, to eliminate eddy currents. The magnets, #46, being either square or cylindrical are positioned relative to the rectangular stationary magnets, #30 in Figure 5 to permit centrifugal radial expansion, keeping top rotating magnets, #46, always radially inside the length of the stationary rectangular magnets, #30. Magnets #30 and #46 by repulsive magnetic forces assist in the retention of the magnets in their pockets.

The flywheel, #14, is wound on site to inner spool, #44. Magnet array #39 is fixed to spool, #44, via a flange #42 on extension of #39 for example by a bolted assembly, #43. Further enhancements against centrifugal force can be added in the form of reinforcements, #49.

The drive diaphragms, #19, are bolted / fastened / glued at location #23. Refer also to Figures 8 -11.

Figure 7 is a replication of a graph of a pair of magnets in repulsive mode, where the horizontal axis, #60, represents the air gap in mm. The repulsive force in kg is the vertical axis as shown by #61. The angle #59 is approximately 45 degrees and helps define the optimal design span, #58.

Figure 8 shows an attachment method of the diaphragm #19 to the inner flange #56, which is a feature of the winding spool #44. The end of the diaphragm, #19, is a right angled Y in the illustration and is glued, #70, to the ID and top flange face.

Figure 9 demonstrates an alternate to Figure 8, by the addition of a mass, #71, to the diaphragm, such that the expansion at the interface of the diaphragm, #19 to the winding spool, #44, is always greater than the flywheel, #14, expansion, maintaining good torque transmission contact.

Figure 10 illustrates another design, where the diaphragm, #19, has a reverse angle protrusion, #77, on its underside, which under axial pressure, #75, deflects radially outwards at its extremity and slides into semi-dovetail slot, #72, complete with pre-positioned adhesive, #70.

Figure 11 shows a further type of snap and glue fastening method, where the 11) of the flange #56 is tapered, #73, and when diaphragm, #19, is pressed axially, #75, this action permits the slotted diaphragm, #74, to deflect radially inwards,until the end of the ID is reached when it will snap outwards and retain the diaphragm, #19 axially.

An axial protrusion, #76, can also be fitted into a parallel, trepanned like slot in the top face of the winding spool flange.

Combinations and variations of attachment of diaphragms, #19, and drive flanges, #s 56 & 57, on flywheel assembly Figures 8 -11, are of course possible as well as other means known to those skilled in the art, including fastening by flange holes #23 in Figure 6.

Figure 12 shows how to maintain a more stable concentricity when flywheel, #14, is at rest to facilitate start-up on the drive shaft active magnetic bearings, #s 21 & 24.

One of the rotating concentric rows of elevating bearings, #81, will have an effective smaller radius, #78, as compared to usual radius, #79, such that it will not be radially covered completely by the bottom fixed magnets, #11, when stationary. This will create an additional centring force. As flywheel, #14, comes up to running speed, the rotating magnet ring, #81, should be again running within the confines of the stationary magnet, as shown by radius #80 and full elevating force is then available, from this changed magnet circular array, #81.

Figure 13 shows how the rotating magnets, #39, joined to spool, #44 and flywheel winding, #18, together with stationary magnets, #29, can be extended radially inwards to enlarge the area for levitation magnets as required for the rotating assembly mass.

Figure 14 shows an example of a cylindrical magnet, #46, mounted by gluing it inside a pocket, #83. The pocket sides can be manufactured from any strong moulded, extruded or machined from solid bar of a suitable composite. The base #84 can be of the same material as #83 and produced as one part or may be formed separately from a composite with magnetic properties such that it captures the stray flux and directs it to give best repulsive properties. Finally it is also possible to shield flux by means of a metal sheet such as Mu metal, #85, attached to a non-magnetic base, #84. This pocket, #83 can mechanically assist in bridging between segments, such as #39.

Claims (38)

1. Large flywheel pseudo levitation bearing and drive system Claims: 1. A method to levitate and enable rotation of a large flywheel in air, vacuum or suitable gas by a prime number of concentric rows of Opposing large prime numbers of permanent magnets in repulsive mode, arranged in a frustrated cone beneath the flywheel, giving pseudo-levij and centralising properties all the while keeping any frictional losses, vertical bounce and wobble to a minimum, driving a central shaft by a flexible torsionally stiff means attached to internal features on the flywheel winding spool and also attached to the central drive shaft by suitable means, and said shaft is mounted in active magnetic or mechanical bearings driving though a special coupling to seal against vacuum leakage. to external shaft on exterior of containment / vacuum vessel.
2. 2. As in Claim 1, the angle of the frustrated cone is determined by the centralising forces needed, the elevating forces to maintain a practical vertical air gap, the capability of the flywheel winding to withstand against centrifugal forces acting upon the rotating magnet array and the available area on the base of the flywheel to fit elevating magnets.
3. 3. As in Claim 1, the frustrated cones, rotating and stationary for practical reasons are composed of segments, which abut together.
4. 4. As in Claim I, the magnets may bridge between the segments of the frustrated cone.
5. 5. As in Claim 1, the frustrated cone angle is optimised to establish the best ratio of centring magnetic forces generated by the frustrated cone design versus the elevating magnetic forces.
6. 6. As in Claim 1, the upper rotating magnets can be cylindrical, axially magnetised, so that engagement of repulsive forces is smoother and less cogging.
7. 7. As in Claim 1, when the flywheel expands under centrifugal forces, the lower fixed magnets must be rectangular or elongated with semi circle ends, such that the upper rotational cylindrical or square magnets are always in full radial contact with the fixed magnets.
8. 8. As in Claim 7, the upper rotating magnets must always be radially within the lower fixed magnets, inner and outer diameters to remain stable.
9. 9. The magnets, as in Claim 1, are arranged in a prime number of concentric rings.
10. 10. As in Claim 9, the greater the prime number of concentric rings, the more stable the flywheel becomes.
11. 11. The start positions of each pair of opposing magnet concentric rings in Claim 9 are offset from each other by 360 Degrees divided by the prime number of magnet concentric rings in total, to minimise any notching effect, lower "cogging" torque to almost zero and smooth the vertical bounce.
12. 12. As in Claim 9, further improvements in smooth running can be made by having differing large prime numbers of permanent magnets opposing each other in an opposing pair of top rotating and bottom stationary, rings.
13. 13. As in Claim 9, the physical sizes and attributes of the magnets in any of the Opposing concentric rings may be substantially different from any of the other opposing rings to reduce cogging even further.
14. 14. As in Claim 9, to best stabilise flywheel at rest to assist active magnetic bearings on start-up, one rotating concentric row of magnets, may slightly radially inwards overhang the stationary opposing ring of magnets and the radial repulsive forces thus generated will stabilize centrally the position of the flywheel.
15. 15. As in Claim 1, the ratio of flywheel outer diameter to height has an important influence on stability.
16. 16. As per Claim I, the flexible, torsionally stiff drive between flywheel and drive shaft is preferably a diaphragm, which can expand radially and axially in concert with the flywheel as it speeds up and slows down.
17. 17. As in Claim 1, the number of sets of diaphragms can be one, two or more, similarly attached to flywheel winding spool and drive shaft.
18. 18. As in Claim 1, the diaphragms are manufactured preferably, but not exclusively, in carbon fibre / epoxy, being capable of stretching vertically and radially to adjust to expansion of flywheel due to rotational forces as it drops down the frustrated cone ramp.
19. 19. As in Claim 16, the diaphragms may have circular, elliptical or other holes in the diaphragm to maximise properties.
20. 20. As in Claim 16, the diaphragms may have an axial preload imposed on them whilst stationary, so that as flywheel speeds up and drops down the frustrated cone ramp, the realised axial thrust load on the shaft thrust bearing is reduced at frill speed, increasing bearing life or reducing the size of the thrust bearing.
21. 21. As per Claim 20, the diaphragms are able to support the axial loading on the drive shaft without any thrust bearing.
22. 22. As in Claim 1 the diaphragms transmitting the torque to the drive shaft may be affixed to an internal flange or alternate device on the winding spool by a combination of bolting, pinning, clamping and or adhesives.
23. 23. As in Claim 22 the diaphragms may be affixed to an internal flange on the winding spool by a combination of adhesives and axially and or radially snap together mechanisms using axial pressure.
24. 24. As in Claim 22 the diaphragms may be affixed to an internal flange on the winding spool by a combination of adhesive and added mass to the diaphragm, such that the diaphragm will always stretch more than flywheel and compressive force maintains the contact and torque transmission.
25. 25. As in Claim 1 the diaphragm is fitted by its 11) to a flange mounted on the drive shaft by means, which can be readily assembled and disassembled.
26. 26. As in Claim 1, the magnets can be placed in a separate pocket as an assembly which can be wholly or partially manufactured from a non conducting material around the magnet sides to eliminate eddy currents and the base of said pocket is composed of material to prevent stray flux and minimise eddy currents.
27. 27. As in Claim 26, stray flux can also be prevented by the use of special shielding materials such as Mu metal.
28. 28. As in Claim 26, the magnets may have incorporated a magnetic focussing arrangement to improve the flux path and enhance magnetic properties, especially repulsion.
29. 29. As in Claim I, preferably the final drive takes pLace by a magnetic coupling I gearbox incorporated into the lid of the flywheel containment I vacuum housing providing a hermetic seal and a fixed ratio change can be designed if desirable.
30. 30. As in Claim 29, the final drive arrangement may be magnetically axial or radial in layout.
31. 31. As per Claim 30, radial is the preferred embodiment to best resist vacuum induced stresses and maximum torque transmission.
32. 32. As per Claim 29, the magnetic coupling / gearbox hermetical seal can be fitted with a magnetic clutch disengagement mechanism to lower the parasitic losses, when flywheel is in storage mode.
33. 33. As per Claim 1, a shaft bearing design which does not need lubrication and can run in a vacuum.
34. 34. As per Claim 1, the preferred embodiment of shaft bearing is an active magnetic bearing, using propriety software to stabilise flywheel through the diaphragms.
35. 35. As in Claim I, the bearings may be lubricated white metal bearing, both plain and tilting pad, air bearings or ceramic rolling element design of sufficient radial and axial load capacity to control stability on flywheel.
36. 36. As in Claim 1, the bearing designs, magnetic and or mechanical, must take into account the effect of precession torque from the earth's rotation.
37. 37. As in Claim 36, it can be advantageous to design centre shaft and bearing arrangement to auto correct the effects of precession torque and keep magnetic air gaps constant.
38. 38. As in Claim 1, the repulsive magnet rings can extend radially inwards under lower diaphragm to provide more surface area to increase repulsive forces.