Electricity generation and / or storage equipment

Abstract

1. An electrical power generation and / or power storage apparatus comprising a floating flywheel, the flywheel being adapted, in use, to contact a body of liquid for rotation about a substantially vertical axis, the underside of the flywheel including circumferentially extending openings, gas being trapped in the openings by the surface of the liquid, in use, to define a gas cushion for supporting said flywheel.

Description

[Technical field]

[0001] The present invention relates to electrical power generation and / or storage systems, and in particular to such systems using floating flywheels. [Background technology]

[0002] There is a widespread and well-publicized long-term vision worldwide to move away from fossil fuels towards greener alternatives for electricity generation. Renewable energy sources such as wind and solar have clear potential to reduce reliance on fossil fuels. Climate change issues, among other factors, are driving the increased deployment of both technologies. Both solar photovoltaics and wind energy are intermittent in output. The variability of these sources raises natural questions regarding the reliability of power grids that derive a large proportion of their energy from these sources. It is widely understood that energy storage will be a backbone of the evolving energy system, especially as reliance on renewable energy sources increases.

[0003] Several methods of electrical energy storage exist, including pumped hydroelectric energy storage, batteries, compressed air energy storage and flywheels. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has arisen as a result of research into providing improved energy generation and / or energy storage devices. [Means for solving the problem]

[0005] In one aspect the invention provides a power generation and / or power storage apparatus comprising a floating flywheel, the flywheel being adapted, in use, to contact a body of liquid for rotation about a substantially vertical axis, the underside of the flywheel including a substantially circumferentially extending opening, gas being trapped in the opening by the surface of the liquid, in use, to define a gas cushion for supporting the flywheel.

[0006] With such an arrangement, the flywheel is adapted to float on the surface of the cushion of gas in use. Contact of the flywheel with the liquid body provides a fluid seal for the gas cushion. The liquid body may be an open body of water such as an ocean or lake, or may comprise a suitable trough or otherwise. The opening may face the liquid body such that the gas cushion is supported by the surface of the liquid body, or may face a supporting surface other than the liquid body such that the gas cushion is supported by the supporting surface. In a further arrangement, the opening may face both the body of water and a supporting surface other than the body of water. Regardless of the arrangement, the flywheel is stabilized in pitch and roll by contact with the liquid body. Contact with the liquid body is preferably via one or more circumferential depending walls, in which case stabilization occurs by displacement of the one or more circumferential depending walls into the liquid body.

[0007] The gas is most preferably air. The liquid is most preferably water. The opening extends substantially continuously around the entire circumference of the flywheel.

[0008] According to this arrangement, the flywheel is supported on one or more gas cushions, most preferably air cushions. The gas cushions serve to reduce frictional forces and, in open water installations, wave induced movements are substantially reduced. The amount of gas cushion and therefore the draft of the flywheel can be maintained or restored by injecting more gas. This may be done using an air compressor.

[0009] As previously mentioned, the gas is not limited to air, but for simplicity the following description will focus on providing an air cushion, however it should be understood that any of the described configurations can be suitably modified to use gases other than air, as would be readily apparent to one skilled in the art.

[0010] The embodiment provides a large floating horizontal flywheel that stores mechanical energy by rotating about a vertical axis. The flywheel can function to store naturally occurring wind energy and / or converted electrical energy captured from elsewhere as rotational mechanical energy. Such mechanical energy can be subsequently converted back into electrical energy as required and distributed by cable to end users. Alternatively, the electricity can be used for other purposes. For example, the energy can be used on or adjacent to the device to produce hydrogen by electrolysis, which can then be delivered by pipeline to end users, along with by-product oxygen in a separate pipeline if required.

[0011] In the case of natural wind energy, the flywheel may have multiple sails attached to it.

[0012] Embodiments including very large flywheels have the potential to store, generate and deliver gigawatts of energy.

[0013] According to one or more embodiments, the device may be located offshore in an open body of water and moored to the ocean floor, hi other embodiments, the device may float in a circular trough or otherwise onshore in a body of water.

[0014] In a preferred configuration, for open water installations, the overall dimensions of the flywheel may be large enough to keep the pitch and roll motions of the flywheel substantially decoupled from the incident waves to a minimum compared to the incident wave length. The inherent minimum overall dimensions to achieve this decoupling may be, for example, about 1500 meters in open water where a typical wave spectrum prevails.

[0015] Substantial gyroscopic stabilization is a feature of various embodiments that is also beneficial for performance.

[0016] The flywheel may be substantially circular. The flywheel may include a cover that is airtight and closes the center of the ring. The cover may include a disk that may be cellular, or may include a frame closed by a shell that may be steel, concrete, glass-reinforced plastic, or airtight fiber. The cover may close the opening.

[0017] The flywheel, whatever its form, may include a pair of spaced circumferential walls that depend from the flywheel in use, in which case the opening is provided between the walls. One of the circumferential walls may be an outer circumferential wall, or both walls may be spaced radially inwardly of the periphery of the flywheel. Alternatively, the flywheel may include a single circumferential wall that depends from the flywheel in use, in which case the opening is provided by the circumferential wall. The circumferential wall may be at the periphery of the flywheel, or may be spaced radially inwardly of the periphery of the flywheel. The circumferential wall preferably depends substantially vertically in use. The circumferential wall preferably penetrates the surface of the liquid in use. Such penetration provides a submerged surface that supports the flywheel above the surface of the liquid. As previously mentioned, displacement of the circumferential wall into the liquid region provides stabilization in pitch and roll.

[0018] Surface friction between the rotating submerged surface and the surrounding water in such offshore embodiments will create gyres, which can further provide additional energy storage capacity that can be utilized and serve to reduce surface friction as a result of the reduction in the relative velocity between the rotating submerged surface and the water.

[0019] The devices according to various embodiments are semi-transparent to waves since most of the energy of the incident wave will propagate under the wall, through the lowered water surface that defines the underside of the air cushion, and then back under the subsequent wall into the open water, thereby reducing the force of the incident wave. In this way, as a wave passes under the flywheel, the air displaced by the wave crest on the air cushion simply moves into the wave trough with essentially zero change in air pressure on the structure. This can be characterized by the observation that the flywheel behaves hydrostatically and hydrodynamically as if it were a semi-submersible mechanism supported by an air cushion but stabilized by a surface penetrating element / wall, thereby decoupling buoyancy and stability.

[0020] The presence of the air cushion and the minimal bending moments caused by the buoyancy of the surface-piercing elements acting as supports allows a relatively lightweight construction to be employed.

[0021] The flywheel may be formed from any suitable material, such as steel or concrete, but does not exclude other materials, with the preferred embodiment being formed from post-tensioned concrete.

[0022] The flywheel can feature a compartmentalized / cellular structure whereby the compartments / cells can be ballasted with water. By ballasting the cells, the polar second moment of inertia of the flywheel can be increased, thereby increasing the energy storage capacity for any angular velocity.

[0023] The water in the ballasted cells may be subjected to significant centrifugal pressures, in which case the water may be drained tangentially to regenerate electrical energy. In some embodiments, improved damage stability is obtained by leaving a suitable number of cells unsubmerged and / or by providing circumferential compartmentalization of the air cushion.

[0024] The fluid seal may include a segmented labyrinth that may be formed by a number of interlocking cells, each cell formed by a depending wall depending from the flywheel 1 and an opposing wall projecting in an opposite direction relative to the depending wall.

[0025] In accordance with one or more embodiments, electrical energy captured from elsewhere can be reversibly converted by the fixed equipment to rotational mechanical energy for storage by the flywheel at an interface between the fixed equipment and the flywheel, and the flywheel is rotated by the rotational mechanical energy.

[0026] In accordance with one or more embodiments, electrical energy captured from elsewhere can be conducted to the flywheel where it can be reversibly converted by equipment on the flywheel into rotational mechanical energy for storage by the flywheel, which causes the flywheel to rotate.

[0027] In accordance with one or more embodiments, equipment mounted on a flywheel can convert wind energy directly into rotational mechanical energy for storage by the flywheel, which is rotated by the rotational mechanical energy.

[0028] According to one or more embodiments, equipment attached to the flywheel directly and reversibly converts rotational hydrodynamic energy from the surrounding water into rotational mechanical energy for storage by the flywheel, which is then rotated.

[0029] Preferred features are also set out in the dependent claims.

[0030] Embodiments of the invention will now be described, by way of non-limiting example only, with reference to the drawings in which: [Brief description of the drawings]

[0031] [Figure 1] 1A and 1B are plan and sectional elevation views showing an energy power storage device according to a first configuration; [Diagram 2] 2 is an enlarged partial cross-sectional view of the flywheel of the device of FIG. 1 taken along line AA of FIG. 1; [Diagram 3] FIG. 3 is a detailed view of view planes A and B in FIG. 2. [Figure 4] FIG. 1 shows an energy capture / delivery configuration along with an enlarged partial cross-sectional view of the flywheel. [Diagram 5] FIG. 5 shows a further energy capture / delivery configuration. [Figure 6] FIG. 6 shows a further energy capture / delivery configuration. [Figure 7] FIG. 7 discloses different ballasting and mooring configurations. [Figure 8] FIG. 8 discloses different ballasting and mooring configurations. [Figure 9] FIG. 9 discloses different ballasting and mooring configurations. [Figure 10] 10A, 10B and 10C are cross-sectional views of three different flywheel configurations. [Figure 11] 11A and 11B are diagrams illustrating different onshore configurations. [Figure 12] 12A and 12B are diagrams illustrating different sail configurations. [Figure 13] FIG. 13 discloses a different configuration of the sail configuration of FIGS. 12A and 12B. [Figure 14] FIG. 14 discloses a different configuration of the sail configuration of FIGS. 12A and 12B. [Figure 15] 15A and 15B disclose different configurations of the sail configuration of FIGS. 12A and 12B. [Figure 16] FIG. 16 discloses a different configuration of the sail configuration of FIGS. 12A and 12B. [Figure 17] FIG. 17 discloses a different configuration of the sail configuration of FIGS. 12A and 12B. [Figure 18] 18A, 18B and 18C disclose different configurations of the sail configuration of FIGS. 12A and 12B. [Figure 19] FIG. 19 discloses an exemplary damage stability enhancement configuration. [Figure 20] FIG. 20 discloses an exemplary damage stability enhancement configuration. [Figure 21] FIG. 1 is a cross-sectional elevation view of a preferred optimized flywheel configuration. [Figure 22] FIG. 22 is a plan view showing the flywheel of FIG. 21. [Figure 23] FIG. 12C illustrates the preferred optimized configuration C of FIGS. 12A and 12B. [Figure 24] FIG. 13 is a partial cross-sectional view showing a preferred sealing arrangement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Generally, embodiments of the present invention provide an apparatus for power generation and / or storage that includes a novel floating flywheel.

[0033] It should be noted that although clockwise rotation of the flywheel is assumed throughout this specification, counterclockwise rotation is also acceptable, as would be readily apparent to one skilled in the art.

[0034] A power generating and / or power storage device according to a first embodiment is shown in Figure 1. The device comprises a toroidal flywheel 1.

[0035] The flywheel 1 is buoyant and is adapted, in use, to be in contact with the surface of the body of liquid with the underside of the flywheel facing the surface of the liquid. The flywheel is adapted to rotate about a substantially vertical axis. The underside includes circumferentially extending openings 2. In use, gas is trapped within the openings by the surface of the liquid. This provides a gas cushion which serves to provide support to the flywheel 1 and, as previously described, greatly reduces rotational friction. In this arrangement, the circumferential openings preferably extend substantially continuously around the entire circumference of the flywheel 1. Alternatively, it may comprise a number of separate sections, as will be described in more detail below.

[0036] In this arrangement, the flywheel includes a pair of spaced circumferential walls 3, 4 which in use depend from the flywheel 1, and an aperture is provided between the walls, as can be seen clearly in cross-section AA. In this arrangement, a deck 5 extends between the walls and closes the upper side of the aperture 2. The deck is closed to trap gas within the aperture.

[0037] As shown, the walls preferably hang vertically in use. The walls 3,4 penetrate the surface of the liquid in use, the walls 3,4 thereby defining a support surface for the flywheel 1.

[0038] With such an arrangement the flywheel is caused in use to float on the surface of a cushion of gas trapped within the opening 2. Contact of the flywheel with the liquid body provides a seal to the gas cushion through the walls 3, 4. The flywheel 1 is stabilized in pitch and roll by contact with the liquid body due to displacement of the walls 3, 4 into the liquid body. The opening 2 faces the liquid body. In onshore arrangements such as those described below with respect to Figures 11 and 24, the opening 2 may instead face a solid supporting surface such as the ground or a platform.

[0039] A flywheel 1 in this configuration has a depth Z, a deck width X, and an inside diameter Y. As will be appreciated by those skilled in the art, increasing any of these dimensions increases the polar moment of inertia of the flywheel 1, thereby increasing its energy storage capacity at any angular velocity.

[0040] Referring to Figure 1, there is shown one exemplary, non-limiting external electrical energy capture and delivery facility 6. It should be noted that the embodiment of Figure 1 is not limited to the presence or form of these facilities, as described in the following paragraphs, and various alternative configurations can be implemented, as will be appreciated by those skilled in the art.

[0041] A typical energy generation module remains stationary in global coordinates as the flywheel rotates. Relative motion between the energy generation module and the flywheel is used to generate electricity or to augment rotational mechanical energy by any suitable conventional means, such as, but not limited to, a wheeled bogie supported on the inner surface of the energy generation module and coupled to a generator / motor leaning against the outer surface of the flywheel. Alternatively, an excitation coil or array of permanent magnets on the flywheel periphery opposed to a generating or power coil on the inner surface of the energy generation module can form a generator or motor as the context requires. A further preferred alternative is a toroidal magnetic levitation track that serves the dual purpose of converting captured electrical energy stored as rotational mechanical energy and vice versa, in addition to taking on some or all of the total weight supported on the air cushion resulting in reduced air cushion depth, reduced hanging wall dimensions, and reduced friction losses. Many suitable configurations will be readily apparent to those skilled in the art, and the invention is not intended to be limited in this respect.

[0042] The energy generation modules may be supported, for example, by rails or ledges around the periphery of the flywheel on suitable wheeled bogies or bearings to allow free relative circumferential movement and freedom for the flywheel to move vertically while carrying the energy generation modules.

[0043] Alternatively, if electrical power is generated on the flywheel for distribution or captured on the flywheel for conversion to rotational mechanical energy thereon, then as desired, the energy generation module may simply retain slip rings, pantographs, or other conventional devices for transmitting electricity to and from the flywheel, as would be readily apparent to one skilled in the art.

[0044] The selected energy generation module, in some example configurations, also holds the upper ends of mooring legs of cables and / or chains in the conventional manner of offshore floating structures. In such cases, there may be three or more pairs of circumferentially arranged mooring legs to hold the flywheel in place and maintain the associated energy generation module in a global position while allowing free vertical movement of the flywheel over a desired vertical range.

[0045] In alternative configurations, the energy generating module or the embedded module may not carry the tethered leg pair, and the module may be maintained in a global position, for example, by a suitable module connector, as will be appreciated by those skilled in the art.

[0046] An embedded module such as that shown in Figure 1 is preferably a multi-processing module that also includes an energy generation module and power management equipment. The embedded module may include additional equipment including, but not limited to, electrolysis equipment for generating hydrogen and oxygen. The embedded module may further provide, for example, accommodation.

[0047] It should be noted that in some configurations, the embedded modules may be located on a fixed structure adjacent to the flywheel, in which case the energy generation modules would be separately mounted on the flywheel and the electrical energy generated thereby would be sent to the embedded modules. For example, the electrical energy may be sent by one or more suspension cables or otherwise, which may first be suspended from the module connectors before reaching the intended embedded module at a nearby circumferential location.

[0048] An exemplary, but preferred, configuration of the flywheel is shown in Figure 2. The deck width X is shown in an enlarged partial cross-sectional view taken at line AA in Figure 1.

[0049] As mentioned above, the opening 2 is provided to allow for the provision of an air cushion which serves to support the flywheel. When used in open water, the air cushion will further reduce the force of incident waves by decoupling the pitch and roll response of the flywheel from incident waves which propagate past and pass under the flywheel with little attenuation.

[0050] As mentioned above, the flywheel preferably has a cellular structure. Providing a cellular structure allows for a reduction in the amount (and cost) of material, and allows for the mass to be varied by ballasting. It is noted that either the walls or the deck can be ballasted in any combination that maintains a uniform mass distribution around the circumference of the flywheel.

[0051] The energy storage capacity of the flywheel 1 can be enhanced by increasing its mass and therefore its polar second moment of inertia. The cellular structure allows the mass to be increased by ballasting the cells 7 with water. This gives an economical solution to vary the mass of the flywheel and thereby manage its energy storage capacity and angular speed of rotation as required.

[0052] As in this configuration, each cell is preferably (but not necessarily) bounded by both radial and circumferential walls to minimize the free surface effects of unfilled cells on the hydrostatic stability of the entire flywheel. In preferred operating practices, the majority of the ballasted cells are fully loaded to minimize free surface effects.

[0053] Notably, the uniform air pressure under the entire flywheel structure, when achieved, serves to reduce the bending moment created in the cross section shown in FIG. 2, thereby allowing for a very economical thin-walled design to be employed in the deck structure.

[0054] If desired, a ballast system may be provided to allow selective ballasting of the cells. The ballast system includes a number of valves 8 and preferably further includes a pump 9. The ballast system allows for the controlled filling and draining of water in the cells 7.

[0055] FIG. 2 shows, for illustrative purposes, a configuration having both ballasted cells (shaded) and anhydrous cells.

[0056] In this exemplary configuration, the cells 7 are fed by a water inlet manifold 10 and drained by a drain manifold 11, preferably controlled by a remotely actuated valve 8. The invention need not be limited to such an exemplary configuration. For example, alternative configurations may omit the manifolds. In this configuration including manifolds 10, 11, a water inlet 12 and a drain 13 are provided, connected to the water inlet manifold 10 and the drain manifold 11, respectively. The water inlet 12 and the drain 13 are preferably oriented such that both ballasting and de-ballasting are assisted by the rotation of the flywheel. The ballast system can also be implemented in this manner without the use of a pump 9. However, one or more pumps are preferably provided as shown.

[0057] The pump will be a useful aid in ballasting, especially when the water inlet manifold is at a level above the water inlet during use, or when the flywheel is not rotating fast enough to automatically prime the system.

[0058] The introduction of one or more pumps allows for further utility in certain exemplary configurations, especially when a pump is configured to function as both a pump and a turbine.

[0059] In the preferred configuration where the captured electrical energy is converted to mechanical energy in the energy generation module by the motorized bogie using the above-exemplified applications, or where the flywheel's periphery serves as the rotor of an electric motor / generator with the energy generation module forming the stator, the rotational mechanical energy thus converted is directly applied to the flywheel at this interface, thereby increasing its angular velocity. Alternatively, if it is desired to maintain a constant angular velocity, for example additional ballast may be mounted to increase the angular moment of inertia of the flywheel by a corresponding amount, typically to maintain the target tangential velocity at its set point. The reverse applies when regenerating electrical energy from stored rotational mechanical energy.

[0060] If in the flywheel electrical energy is converted from the rotational kinetic energy stored by the flywheel, another preferred option is to allow flow from the ballasted cells 7 under centrifugal pressure through valve 8 into the drain manifold 11 and then through a pump 9 acting as a turbine or through one or more separate turbines to generate electrical energy.

[0061] Conversely, if electrical energy from an external source, e.g. a wind farm or otherwise, is captured by the flywheel 1 such that it is converted there from electrical energy to rotational kinetic energy stored by the flywheel 1, one preferred option for this conversion is for the captured electrical energy to power a pump 9 acting as a jet pump to drain high energy water through an outlet, creating a tangential force on the flywheel 1 that increases the angular velocity of the flywheel 1 and thereby increases the amount of rotational kinetic energy stored. The water thus drained through the outlet may be drawn from the ballasted cells 7 through valve 8 to the outlet manifold 11, thereby further reducing the polar second moment of inertia and helping to accelerate the rate at which the tangential velocity rises towards the target value.

[0062] Alternatively, the water draining from the drain outlet 13 may pass under centrifugal pressure through the drain manifold 11 directly from the water inlet 12 through a cross-connected portion of the manifold to a drain manifold (not shown) and then through a pump 9 which acts as a pump-driving turbine with captured electrical energy to increase the tangential velocity and be stored as rotational mechanical energy.

[0063] It should be noted that each of the above configurations may be realized using separate pump / turbines which can be mounted on appropriate manifolds so that one or the other can function.

[0064] While flywheels according to the principles described herein exhibit a relatively flat performance curve, indicating that "reciprocating" energy storage and recovery efficiency is somewhat tolerant to actual angular rotational speed, it is expected that for any particular design there will be a target tangential speed and corresponding angular rotational speed. By providing a ballast configuration according to the exemplary configurations described above or otherwise, the flywheel will provide the ability, first, to take in ballast when accepting electrical energy for conversion and storage as rotational kinetic energy, and second, to expel ballast in the reverse context of generating electrical energy from the rotational kinetic energy of the flywheel. This allows the total mass of the flywheel to be varied such that the polar second moment of inertia of the flywheel is varied to compensate for the change in stored energy, and a constant tangential speed can be maintained, thereby maintaining peak operating efficiency and usefully flattening the performance curve.

[0065] The flywheel 1 may optionally be equipped with a drag member 14, as shown by way of example in FIG. 2. The form of the drag member 14 need not be particularly limited. The drag member 14 may comprise a plate. The use of drag members is of particular interest when the flywheel is placed in open water. Such drag members 14 may be located at regular points on the circumference of the flywheel 1. The drag members 14 may preferably be mounted in a retractable manner, in which case they can be opened when required and stored flush with the circumference of the flywheel 1 when not in use. The drag members 14 may be pivotally mounted for such purposes. Many suitable mounting configurations will be readily apparent to those skilled in the art. View plane A of FIG. 3 shows a side elevational view of an exemplary drag plate 14 fully deployed, also showing a recess 15 in which the drag plate 14 can be stored.

[0066] As mentioned above, one function of the air cushion is to limit the surface friction between the flywheel 1 and the water by minimizing the wetted area. Some friction remains which acts to circulate the nearby water by reducing the tangential velocity and dragging the water somewhat with the wetted surface. The provision of the drag member 14 allows some of the kinetic energy of this circulating water to be recovered. Although the velocity profile of the circulating water decreases with increasing radius away from the flywheel, its effective size in plan view will continue to increase radially outward over time as the energy increases, forming a gyre around the flywheel. Such a gyre is a highly efficient store of rotational kinetic energy which naturally decays fairly slowly.

[0067] It should also be noted that as this reflux absorbs energy from the flywheel 1 and as it increases in size, the tangential velocity of the reflux also increases near its interface with the outer wetted surface of the flywheel 1, reducing the relative velocity between the reflux and the flywheel 1, reducing the shear forces between the two, thereby self-limiting the energy loss to the reflux.

[0068] In this context, the drag member 14 can serve two functions:

[0069] Firstly, if it becomes necessary to stop the flywheel 1 as quickly as possible, for example for some unscheduled maintenance or otherwise, the stored energy needs to be dissipated. If this exceeds the capacity of the generating system to convert electrical energy, or exceeds the delivery or consumption capacity of the energy delivery equipment, the drag member 14 can be adapted to undergo increased drag, thereby slowing down the rotational speed. Such drag will create turbulence in the vicinity of the drag member 14, where energy is permanently lost as heat. However, this drag will also increase the size and kinetic energy of the gyre, where part of the lost energy will be stored.

[0070] Secondly, if the stored energy becomes significantly depleted by long-term demand with little or no replenishment, a situation may arise where the surrounding gyre rotates faster than the flywheel 1. In such a situation, some of the flywheel's stored energy can be usefully recovered by employing a drag member 14 to increase the tangential drag of the gyre on the flywheel 1, i.e., by reversing the process described above.

[0071] FIG. 3 shows a side elevational view of the water inlet 12 and outlet 13 as described above with particular reference to FIG. 2. In the illustrated example configuration, the water inlet 12 comprises a bell-shaped port configured to smooth inflow. As will be readily apparent to one skilled in the art, the water inlets may be configured in other configurations. Both the water inlet 12 and outlet 13 are preferably housed in smooth nacelles as shown to minimize drag. In some configurations, these nacelles may be retractable, in which case they can be retracted when not in use, leaving a smooth circumferential surface on the flywheel to further limit drag.

[0072] The apparatus is preferably configured such that the rate of flow of wastewater from the outlet 13 can be varied. In one configuration, the outlet 13 can optionally be segmented into two or more retractable sections of gradually increasing internal diameter to form a draft tube for slowing the flow out of the outlet without excessive turbulent losses. Figure 3 shows an example having three such sections. Alternative configurations may not be like this. In particular, there may be alternative means implemented to control the rate of wastewater.

[0073] As mentioned above, a flywheel according to the principles of the present invention generally has an optimized tangential velocity V TThe flywheel 1 will be designed to operate at or near an optimum performance point including the optimum design point. In such a case, the discharge velocity of the flow from the outlet 13 relative to the flywheel 1 can be set to have a velocity near zero relative to the adjacent water into which the flow is discharged. Such a configuration will function to minimize turbulent losses. However, if the flywheel 1 is operating away from its optimum design point, it may be desirable to accelerate the angular velocity of rotation of the flywheel 1 to reduce or eliminate the velocity mismatch between the discharged flow and the water in the reflux flow with which the discharged flow must be able to mix without excessive losses.

[0074] Rate control using the example configuration of FIG. 3 is discussed in further detail below.

[0075] The flywheel has a tangential velocity V T When the full design value of φ is reached, a relatively high relative velocity between the discharge from the outlet 13 and the surrounding water may be appropriate. In such a case, only the first upstream section of the nacelle may be employed, with the outlet diameter of the outlet being the smallest diameter available.

[0076] At start-up, when the flywheel is still rotating at a slow speed, the velocity mismatch between the discharged water and the surrounding water is much smaller, and it would be preferable to allow the discharged water to slow down more in the longer draft tube before exiting into the surrounding water to minimize energy losses. Here, for example, all three sections (as shown in FIG. 3) may be employed to minimize turbulent losses by more closely matching the velocity of the discharged water with that of the surrounding water.

[0077] Furthermore, at intermediate rotational speeds it may be appropriate to employ only two segments.

[0078] As mentioned above, it should be noted that the above controls may be performed in alternative manners and alternative means of controlling the rate of water drainage may be implemented, as would be readily apparent to one skilled in the art.

[0079] Figure 2 shows the seabed 17. If the water depth is very shallow, bottom clearance will be limited and induced reflux may cause erosion, which can be avoided by proper rock dumping of the area prior to installation.

[0080] It should be noted that in any annular configuration of the flywheel 1 including the spaced apart circumferential depending walls 3, 4, the walls may be substantially the same as one another or may be different from one another. The walls may be configured to include an inner circumferential wall 4 and an outer circumferential wall 3. The inner and outer circumferential walls may include cells 7 so that both may be ballasted, or only one of the inner and outer circumferential walls may include cells, or none of the circumferential walls may include cells. The inner and outer circumferential walls may have the same thickness or may differ from one another in thickness. Different combinations of these features may be provided in the example configurations.

[0081] Figure 4 shows an example configuration in which the thickness of the outer peripheral wall 3 is greater than the thickness of the inner peripheral wall 4. Both walls have the capacity to be ballasted, although this does not necessarily have to be the case in line with the above explanation.

[0082] The outer peripheral wall 3 is made thicker because it is at the maximum overall diameter of the flywheel and therefore its displacement in the water is the primary factor in maintaining the hydrostatic pitch and roll stability of the flywheel. The inner peripheral wall 4 is a secondary factor in hydrostatic stability and the thickness of the inner peripheral wall 4 may be selected primarily to provide sufficient structural strength, where the selected thickness of the outer peripheral wall already provides sufficient hydrostatic stability more efficiently.

[0083] As a separate consideration, again applicable to all toroidal configurations of the flywheel, the thickness and configuration of the deck 5 may also vary. The thickness may be set to maximize the volume and therefore the mass of ballast water in the cells 7 to efficiently increase the energy storage capacity. Of note, an advantage of the air cushion is that the deck, and the weight of the ballast if present, are uniformly supported. This allows for a relatively light construction to be provided. The uniform support of the air cushion minimizes bending moment stresses. This allows for a reduction in the overall cost of the flywheel compared to constructions without such uniform support.

[0084] Although not solely related to the above features of the flywheel 1 shown in Figure 4, the arrangement of Figure 4 also discloses, by way of example, a delivery system 6, which will now be described in more detail. It should be noted that such an arrangement may be incorporated into other devices including differently configured flywheels, such as those described elsewhere in this application.

[0085] The transmission and distribution system 6 includes an embedded module in which a power management system is installed, which may include, for example, conventional cables for transmitting electricity, such as but not limited to, high voltage direct current cables, and may further include pipelines, such as but not limited to, steel pipelines, for transmitting hydrogen when hydrogen is optionally produced from the electrical energy in the embedded module.

[0086] These types of energy delivery systems are suitable for delivery from a fixed structure to which an electrical cable can be attached, as shown. The electrical cable can be attached, for example, by pulling it up through a J-pipe, or otherwise attached to supports or legs of the fixed structure after installation. If a pipe is provided, a pipeline riser may be installed on the fixed structure for later subsea connection to the pipeline, or (for small diameters) it may be pulled up through the J-pipe.

[0087] 5A discloses a configuration in which there are no fixed structures present, which can be implemented, for example, when the water is deep enough for the energy delivery system to be provided in the form of a flexible cable or flexible pipeline 19 with sufficient structural integrity to hang in a catenary from the flywheel to the seabed.

[0088] Figure 5B shows detail B of Figure 4. Note that in this example configuration, the embedded module 6 is provided with a helideck for access by maintenance personnel. The provision of a helideck is entirely optional.

[0089] In Fig. 6 a further alternative is disclosed in which the embedded module 6 is arranged on a semi-submersible mechanism 20 moored to the energy generation module. Such an arrangement may be useful in deep sea environments. In such an arrangement it may be preferable to provide support means for the semi-submersible mechanism. In the example arrangement of this figure an articulated mooring frame 21 is provided. This is preferably arranged to give the semi-submersible mechanism freedom to pitch, roll and swell. It may further be arranged to provide access arrangements to the flywheel 1 for maintenance personnel and equipment. It is noted that an optional horizontal arrangement for the energy generation module is also shown, which may be implemented in the various alternative arrangements described herein.

[0090] In FIG. 7 a further example configuration is disclosed that includes a flywheel 1 featuring a central inverted nacelle 23. Any of the energy systems described above can be implemented, and this configuration is not limited in this respect. The central nacelle 23 provides an alternative means of taking in ballast. In such a configuration, the nacelle 23 is preferably in fluid communication with the cells 7 of the flywheel structure through suitable radially extending fluid conveying members 24. In this configuration, these fluid conveying members 24 include pipes. The pipes can be spoke-like. The liquid entering the nacelle 23 will flow radially outward through the pipes under centrifugal pressure. De-ballasting may be performed through suitable outlets as described above or in other ways. As in the previous configuration, a pump may or may not be provided, which may also function as a turbine or may be provided in addition to a separate turbine.

[0091] As a general point, the pump / turbine may be omitted from either configuration to increase the exit velocity of the de-ballasting water, resulting in simplified accessory mounting and reduced surface friction.

[0092] Figure 8 shows an example arrangement with mooring / support legs 25. Such mooring / support legs 25 may be attached to a central swivel 27 as shown. Regardless, these are preferably deployed to the seabed substantially within the planned footprint of the flywheel 1 so as to achieve a compact arrangement.

[0093] 8 also discloses an on-board module 26 that can be installed in any of the configurations described above as desired, but particularly in configurations with on-board energy generation. The on-board module 26 can house various accessory attachments and utilities as desired, which may be otherwise housed in the embedded module or otherwise positioned / housed in alternative configurations.

[0094] Such conventional accessories may include, but are not limited to, any one or more of the following: · An air compressor to manage the pressure and volume of the air cushion and replace air lost under the structure during extreme weather or through absorption by seawater. Voltage regulation to allow the combination of electrical energy supply from multiple sources and economical delivery to the onshore power grid. Emergency power generation. · Main fire pump. Temporary or permanent habitation. Any such occupied space may be fitted with a floor that slopes towards the central flywheel axis. The angle of slope is determined by the target peripheral speed V T In order to allow unhindered movement of personnel in the vehicle, the lines of action of the combined forces of gravity and centripetal force can be set to mimic the standard lines of action of gravity. · Ballasting and / or de-ballasting pumps. · Communications and AI-assisted instrumentation and control systems. An electrolysis plant to produce hydrogen, compress it, condition and distribute it, and, if required, dry, compress and distribute the by-product oxygen.

[0095] In configurations including the swivel 27, the swivel 27 may be provided for energy delivery via an electrical cable and / or flexible hydrogen pipeline, consistent with the discussion above. The swivel 27 may also be configured to provide for electrical energy capture from an external source for storage as rotational kinetic energy.

[0096] In a preferred configuration, the swivel includes a buoyancy tank 30. The buoyancy tank 30 is preferably configured to be partially submersible in use.

[0097] The buoyancy tanks 30 may help support the weight of the components of the flywheel 1. The buoyancy tanks 30 may help support the weight of one or more or all of the following components, if provided: the swivel, the helideck 31, the spoke elements which may be liquid carrying as described above or purely structural as in the configuration of the figures.

[0098] Buoyancy tanks 30 may additionally or alternatively be configured so that mooring / support legs 25, if provided, have their lines of action intersecting swivel 27 at the location where swivel 27 abuts spoke element 24. Such a configuration will minimize significant bending moments on the spoke elements due to lateral forces resisted by the support / mooring legs.

[0099] As mentioned above, the flywheel 1 can optionally include a helideck 31. If included, the helideck can be located in the center of the flywheel. In configurations with spoke elements 24, the spoke elements 24 can provide support for the helideck 31 and can also provide access facilities. In closed circular configurations of the flywheel, such as the one shown in FIG. 10A, for example, the helideck can simply be marked on the deck. As expected within the scope of this disclosure, with a sufficiently large flywheel, there will be a clear enough access for a helicopter to land in the center. Also, in the center position, the rotational speed of the flywheel will be slow enough so as not to interfere with helicopter operations while the flywheel is in operation. For example, a large flywheel may take several minutes to complete one revolution.

[0100] Figure 9 shows an arrangement similar to that of Figure 8, including a swivel 27, but further including a central inverted nacelle 23 as described with respect to Figure 7. The swivel 27 and the nacelle 23 may be combined as a single unit. As with the arrangement of Figure 7, the spoke elements 24 preferably include pipes for ballasting. Mooring supports / legs 25 according to the arrangement of Figure 8 are provided.

[0101] As previously mentioned, and as would be readily apparent to one skilled in the art, different features / combinations of features of the different configurations described above may be combined / varied. In particular, the disclosure of a particular feature in combination with other features of a particular configuration does not bind those features together. These embodiments are non-limiting and are for illustrative purposes only.

[0102] 10A, 10B and 10C show three different example configurations of flywheel structures that can be implemented in configurations that include any of the features discussed above with respect to the described configurations.

[0103] Figure 10A shows a closed circular configuration, which contrasts with the toroidal form of the flywheel discussed above. The closed configuration will produce lower surface friction than the toroidal configuration because there is only one wetted surface penetration.

[0104] Figure 10B shows a ring configuration, which, while it has the same planar surface area and mass as the closed circular configuration of Figure 10A, will have a greater energy storage capacity because its mass is concentrated near its periphery.

[0105] Figure 10C shows a layered ring configuration, which if it had the same planar dimensions as the configuration in Figure 10B but twice the mass, would have twice the energy storage capacity.

[0106] However, the target tangential velocity V for any flywheel configuration T Note that the tangential velocity can also be chosen to have a similar maximum value that limits the surface friction between the outer circumferential surface and the surrounding water to a reasonable level. The upper limit on the tangential velocity may be set at, for example, 80 km / hr. For example, a closed circular configuration such as that shown in FIG. 10A and a layered annular configuration such as that shown in FIG. 10C have the same tangential velocity V T , the inherent energy storage advantage of the latter is countered by the slower rotational angular velocity as a result of its larger diameter (if such is assumed).

[0107] 10A-10C are presented to help illustrate design principles according to the present disclosure and are otherwise non-limiting.

[0108] An exemplary, non-limiting flywheel is shown in full cross section in Figure 11. The flywheel has a layered annular configuration, but is not necessarily so limited. The flywheel can be annular and formed in any of the configurations described above. Alternatively, the flywheel can be formed in a closed circular configuration.

[0109] FIG. 11A shows an onshore configuration option where the lower ends of the inner and outer periphery of the flywheel are submerged in separate troughs 33, 34 which are completely circular in plan view.

[0110] FIG. 11B shows another onshore configuration option in which the ends are submerged in a single trough 35 .

[0111] The choice between these two options is a matter of economics. For example, separate troughs may require less excavation at the site than a single trough. However, to economically maintain the required target head of the air cushion, an airtight blind may be required for the exposed ground between the two concentric troughs in a configuration that includes separate troughs. As will be readily apparent to one skilled in the art, the troughs may be constructed in any suitable conventional manner.

[0112] Unlike offshore flywheels, the water in an onshore configuration may be a separated volume, so to reduce the drag on the flywheel or to reduce the target tangential velocity V T It should be noted that it is possible and may be desirable to add friction reducing chemicals to the water, such as, but not limited to, long chain polymers, to increase friction and provide greater energy storage capacity.

[0113] It should also be noted that site economies can be improved by selecting the flywheel elevation so that excavation below the flywheel to provide ground clearance provides a sufficient amount of cut soil to build the fill supporting the outer separate trough.

[0114] A plurality of energy generating modules 6 may be provided. There may be three or more evenly spaced energy generating modules held in place circumferentially and radially by a suitable support structure. The vertical elevation of the energy generating modules can be controlled by the position of the flywheel. The support structure can also be configured to maintain the flywheel in place in plan view.

[0115] The exemplary onshore configuration is in the form of a torus, but may include closed circular configurations as well.

[0116] It is worth noting that the measures of comparative economy for closed-circular, annular, and layered annular configurations differ in the onshore case from the measures that control the choice of offshore configuration, for reasons including the following: The need to isolate the flywheel from incident spectral wave energy by having a minimum overall diameter of about 1500m no longer applies. Smaller diameters may be sufficient to meet the site requirements for onshore flywheels. Only the outermost separate trough is required. The air cushion extends over the entire planar area of ​​the flywheel, so the blinding area can be substantially larger.

[0117] It should be noted that other systems and considerations remain for offshore installations, and various aspects of the offshore configurations of this disclosure may be implemented in onshore configurations, as would be readily apparent to one of ordinary skill in the art.

[0118] Although mentioned briefly, the device has thus far been described primarily with respect to storing externally generated energy. With reference to Figures 12 to 20, the use of the device to generate electricity will now be considered. The device can be configured to generate electricity from the wind, which provides rotational kinetic energy to the flywheel for storage without any conversion.

[0119] To this end, a flywheel 1 according to any of the configurations described herein may have a number of sails 37 attached to it. The sails may be mounted on the deck 5 of the flywheel, essentially forming a large cross-flow wind turbine. The sails may be mounted in other ways as well. As will be appreciated by those skilled in the art, any such sail may take many configurations. Some non-limiting example sail configurations are described below.

[0120] An example sail-equipped configuration is shown in Figure 12A, which preferably includes a continuously variable sail configuration, in which a single flexible sail is provided that can be twisted to the optimum angle of attack for the prevailing wind direction at any elevation in the increment above the water.

[0121] This configuration accurately takes into account the continuously variable wind speed and direction at different altitudes. Such variations occur naturally, but are also a characteristic of the flow through a crossflow turbine. In this example configuration there is a vertical mast 38, which is preferably rigid. Taking into account the wind loads from the sails that are accommodated by this mast, the mast can be segmented into several segments. The number of segments can be determined based on the maximum allowable bending moment and the axial Euler buckling load of each mast segment.

[0122] 12A shows a configuration including two such segments, and as will be appreciated from the above description, there may be more or fewer segments in any configuration provided by the present principles. The vertical length of each such segment is preferably augmented by providing universal joints where the segment connects to the flywheel or another segment, thereby substantially eliminating bending moments at these intersections. Each segment may be constrained circumferentially and radially inwardly in plan view by rigging 39, which may preferably be diagonal, and radially outwardly by rigging 40, which may be substantially horizontal.

[0123] Suitable instruments / sensing devices may be provided to determine the continuously varying optimum angle of attack and / or airfoil shape of the continuously variable sail configuration at each increment of altitude and / or stress level at each length increment of the mast segment. As will be readily apparent to one skilled in the art, AI systems comparable to those used in advanced aviation operations may be implemented.

[0124] FIG. 12B shows a sail configuration similar to that of FIG. 12A. The configuration of FIG. 12B also includes multiple sail sections. However, in this configuration, multiple rigid sail sections are employed. Each section can be configured, for example, in the manner of a conventional aircraft wing configuration. By providing rigid sail sections, a separate rigid vertical mast is not required, although configurations with such masts are possible. Each individual sail section can be independently rotated to the average wind speed and direction over its length to obtain the best available direction and magnitude of lift over that section. The more sections there are, the more accurately the sail section can track the prevailing wind speed and direction at each altitude step. FIG. 12B shows four such sections as an example, but is not limited thereto. More or fewer sections can be provided. As in FIG. 12A, rigging 39, 40 is provided to support the sail structure. When considering the number of sections to be implemented, increasing the number of sail sections will require more rigging. More rigging will increase drag. An efficient balance would be desirable.

[0125] Similar to the configuration of Figure 12A, suitable instruments / sensing devices may be provided for input to the sail's control system, and again an AI system may be implemented.

[0126] FIG. 13 shows the configuration of FIG. 12A in plan view. It should be noted that FIG. 13 partially shows two possible rigging options, labeled A and B, respectively. It should be understood that these are alternatives that only one of these rigging configurations can be implemented per mast equipped at a time. According to configuration A, each strand of the rigging 39 extends to the center of the flywheel. In configuration B, each strand 39 extends from the center of the flywheel so as to be supported radially outward. Suitable support structures may be provided for such purposes. Of course, in configurations where the flywheel is not a torus, a top deck would be available for mounting the ends of the rigging strands. Comparative economies of cost and drag during operation would likely determine the preferred configuration of the rigging of any design. Also, alternative configurations to A and B would be readily apparent to one skilled in the art. As stated above, these configurations are merely exemplary and can be changed or modified in many ways, as would be apparent to one skilled in the art.

[0127] It should be noted that provision may be made to allow the lengths of the rigging cables to be adjusted so that the entire sail and rigging can be safely laid flat radially or circumferentially, as appropriate, on the flywheel deck for maintenance and thereafter to return to the operating configuration as shown.

[0128] FIG. 14 is shown to illustrate how the airfoil shapes of both the continuously variable sail configuration as described with respect to FIG. 12A and the rigid sail section as described with respect to FIG. 12B are inverted and also adopt symmetric shapes with respect to the mean wind direction indicated by the arrow.

[0129] When viewed from this wind direction, the sail sections, regardless of their particular configuration, can be configured to adopt an airfoil configuration as shown, whereby the sail sections in the distal and proximal half regions of the flywheel shape contribute to a clockwise rotation. The sail sections at the junction of the proximal and distal half regions are preferably of a symmetric transition shape as shown. The leftmost sail section is preferably perpendicular to the wind direction to contribute to a clockwise rotation. The rightmost sail section preferably has a symmetric transition shape when viewed from the wind direction, facing the wind direction to minimize drag.

[0130] It should be noted that the orientation and shape of each airfoil section is preferably not simply maximized by the control system to provide maximum lateral lift, but rather the parameter controlling the tangential velocity may be the moment of that lateral lift about the central vertical axis of rotation. Thus, the control system preferably continuously calculates and maximizes the product of the lift and the moment arm about the central axis, and adjusts the airfoil configuration and orientation accordingly. Thus, the control system can be configured to set an angle of attack that produces less than maximum lift, but in the direction of the larger moment arm.

[0131] 15-18, exemplary non-limiting configurations of mechanical components of a control system for properly shaping and orienting a sail are shown. The disclosed system can be implemented with either a continuously variable sail configuration or a rigid sail section. Although described in the context of a rigid vertical mast, it can be suitably adapted for use in configurations that omit a mast, such as, but not limited to, configurations including a rigid sail section as described above. Many alternative mechanical configurations are possible, as will be readily apparent to one skilled in the art.

[0132] FIG. 15A discloses a short airfoil shape control cylinder 41 that surrounds a rigid vertical mast 38. The airfoil shape control cylinder 41 can be rotated in either direction relative to the rigid vertical mast 38 as shown by an actuator 43 that holds a spherical bearing 42 and is mounted in a bush in the rigid vertical mast 38 to drive a gear 44 that engages an opposing rack. The airfoil shape control cylinder 41 is maintained concentric with and supported by two or more idler wheels 45. Hydraulic supply and return lines 46 power all elements of the entire system under control of signals received from cables. Status feedback signals are also sent back by cables. Computerized management of all control system elements, preferably utilizing AI, is one of the mechanisms that can be housed in the embedded or on-board module 26, as appropriate.

[0133] Figure 15B discloses the provision of a shorter sail directing cylinder 47 concentrically around the airfoil shape control cylinder. The sail directing cylinder is rotated in both directions by a concentrically held actuator mounted on a rigid vertical mast and supported by multiple, preferably at least three, idler wheels.

[0134] 16 discloses an example arrangement in which a sail orientation cylinder 47 holds a sail profile stretcher 48. An airfoil tip shape profiler 49 is attached to a support arm 50 that includes a telescopic portion 50a. The support arm is mounted on a trunnion held on the sail orientation cylinder and slides through a bushing held in a spherical bearing 42.

[0135] FIG. 17 shows section "AA" of FIG. 16, illustrating in elevation the same components disclosed in plan view in FIG.

[0136] It should be noted that the complete assemblies disclosed in Figures 15-17 can be installed at fine increments in altitude where the continuously variable sail configuration is deployed, whereas where rigid sail sections are deployed, one complete assembly can be attached, for example, to the base of each rigid sail section.

[0137] 18A, 18B and 18C disclose exemplary details of three possible main shapes of the airfoil portion in accordance with the description of FIG. 14 above.

[0138] In one preferred configuration, the leading edge of the airfoil section may be made of strong fabric attached to a sail profile stretcher, itself made of a thin flexible material such as, but not limited to, steel plate, aluminum, plastic or composite material, on both the upper and lower surfaces of the airfoil section. The airfoil section may further include a sail profile stretcher returning to the trailing edge and continuing vertically across the entire surface of the continuously variable sail configuration or rigid sail section as shown in Figure 18. Alternatively, the aft part of the airfoil section may also be made of strong fabric, in which case a similar mechanism for modifying the forward body of the airfoil section may be additionally provided, as shown in Figures 16 and 17, for modifying the shape of the aft body of the airfoil section.

[0139] One example of an alternative preferred solution includes a sail profile stretcher that continues back to the trailing edge of the segment and is attached to an actuated hinge at the very end in a manner similar to a flap on an aircraft wing, as shown in dotted lines.

[0140] To rotate either sail in plan view as shown in Figure 14 without changing the shape of the airfoil at any altitude, the actuators can be operated as a unit with no relative rotation between them. To change the shape of the airfoil section, actuator 43 or actuator 53 is operated to cause relative rotation between the airfoil shape control cylinder and the sail directing cylinder. This relative rotation is shown in Figure 16 moving the airfoil tip shape profiler in both directions. To prevent wear on the flexible fabric that forms the leading edge of the airfoil section, the airfoil tip shape profiler can be arranged to rotate clockwise or counterclockwise. The flexible fabric can be accommodated by a telescopic section attached to the support arm.

[0141] If the control system so requires, the actuated hinge section may be simultaneously employed to further modify the shape of the airfoil section.

[0142] Figure 19 discloses some non-limiting examples of measures that can be taken to enhance the damage stability of a flywheel with any of the above configurations. Note that Figure 19 shows two different component parts of a toroidal flywheel in elevation.

[0143] FIG. 19 first discloses the fundamentally superior inherent damage stability of any flywheel given by the cellular structure forming a "double hull." To allow air escape, gaps are required on two separate faces. Further reinforcement can be obtained by extending selected radial cell walls 53 and circumferential cell walls 54 below deck level but above the lower boundary of the air cushion forming the open cell circumferential and radial walls. If the air cushion is released to the atmosphere, for whatever reason, the freeboard of the flywheel will be reduced because the open cell circumferential and radial walls, other than the cell or cells open to the atmosphere, will enter the water surface and be lower in the water to the point where the air trapped therein compresses to the point where buoyant equilibrium is restored. The many air cushions in the many unaffected cells are designed to provide adequate means to comply with wave action sufficient to maintain a reduced but sufficient freeboard and to reduce damaging bending moments for a long enough period of time to allow the damaged flywheel to recover to shallow water depth and make necessary repairs.

[0144] Further integrity during damage can be provided by extending one or more of the circumferential cell 55 walls down through the air cushion into the water below. This will isolate the loss of air cushion to one or more annular rings that are inadvertently opened to the atmosphere and limit the resulting freeboard reduction in a damage condition, at the expense of increased skin friction during operation.

[0145] Figure 19 also shows that the inverted triangle symbol indicates the water level in all the diagrams and that the head difference between the free water surface and the surface of the air cushion is the head h.

[0146] Two notional flywheels, a closed circular configuration and an annular configuration, are shown in plan view in Figure 20. Exemplary, non-limiting open-cell circumferential and radial walls are shown, as described with reference to Figure 19.

[0147] Many further configurations are possible within the context of the above description. Two preferred but non-limiting examples are described with reference to Figs. 21 to 23. It should be noted that aspects of these configurations can be combined with aspects of any of the configurations described above. The examples shown in the figures are not limiting. For example, the flywheel configurations of Figs. 21 and 22 can be implemented in place of one of the alternative flywheel structures in any of the configurations described above, and / or features of any of those flywheels can be incorporated into a flywheel according to the configurations described herein. Also, any of the power generation configurations described with reference to Figs. 12 to 20 can be implemented with a flywheel configured according to the following description.

[0148] A closed flywheel configuration is shown in elevation and plan views, respectively, in Figures 21 and 22. The flywheel 1 has a circular ring structure. However, the open center of the ring is closed by a cover 60. The form of the cover is not particularly limited. In the illustrated example configuration, the cover takes the form of a lightweight airtight disk. With the center of the ring closed, a single circumferential wall 3 can be provided. This contrasts with the circular ring structure described above. However, it should be noted that a cover such as the one described here can be used with any of the circular ring flywheels described above, or with any other form of circular ring flywheel that includes a pair of circumferential walls 3, 4. The use of a single depending circumferential wall 3 is preferred as it helps reduce surface friction drag from the water.

[0149] The cover 60 may be in a cellular form. This allows for a rigid lightweight flywheel construction. The cellular cover may also be ballasted in accordance with the ballasting description above. A ballasted cover increases the energy storage capacity and possibly increases the weight of the disk to more closely balance the air pressure in the air cushion, leaving the cover in a relatively lightly stressed state during operation. Alternative constructions for the cover include, but are not limited to, a lightweight frame of steel or other enclosed with an airtight shell of steel, concrete, glass reinforced plastic, airtight fiber or other suitable material.

[0150] By using this closed disc configuration for the torus flywheel, the thickness of the air cushion can be significantly reduced, minimizing the hanging wall depth and its wetted surface area.

[0151] The depending circumferential wall may be recessed a significant distance from the circumference of the annulus, i.e., the circumferential wall may be shifted radially inward from the circumference of the flywheel. This is advantageous as it serves to shorten its circumferential length, as shown in Figure 22, thereby reducing skin friction drag while maintaining sufficient hydrostatic stability. However, in alternative configurations, the circumferential wall may be provided at the periphery. The annulus and central disc are preferably arranged to remain above the water level a sufficient distance to reduce wave impact.

[0152] FIG. 23 shows a third preferred example C of the rigging configuration of FIG. 12. This configuration responds to the observation that in practice the spacing between the masts can be much narrower than that shown in FIG. 13, so that the diagonal rigging for each mast may overlap with the diagonal rigging of several adjacent masts to form cable flocks that may potentially cast wake shadows on the sail, thereby limiting the aerodynamic performance of the sail to some extent. The number of diagonal rigging legs can be dramatically reduced as shown in FIG. 23 by arranging the masts in several rows at different radii and supporting them circumferentially and laterally by horizontal rigging. The corresponding increase in total horizontal rigging is much less than the savings in diagonal rigging, thereby realizing both drag and cost reductions. As will be readily apparent to those skilled in the art, many alternative mast and / or rigging configurations are also possible.

[0153] Also, in the configuration of Figure 23, the horizontal rigging casts a wake shadow that forms a horizontal disk at the level of the joint between vertically adjacent sails, which causes less disruption to the airflow profile across the sails, thereby improving performance. The cables at each horizontal rigging level also produce less drag per unit length than diagonal rigging, because the degree to which one complete horizontal pattern of rigging resides within a common turbulent wake is greater than with diagonal rigging.

[0154] The masts are shown recessed from the circumference of the torus by a distance W. The distance W is chosen to be large enough to provide a practical geometry for the diagonal rigging. Increasing W further would reduce the number of masts that can be installed and would reduce the lever arm of the sail lift about the longitudinal axis of the flywheel. As will be appreciated by those skilled in the art, an appropriate balance will be struck based on the particular implementation.

[0155] Referring to FIG. 24, there is shown a partial cross-sectional view of an arrangement of the apparatus including an alternative fluid seal, particularly suitable for use in an onshore arrangement. The fluid seal includes a segmented labyrinth. In this arrangement, the labyrinth is formed by a plurality of interlocking cells, each cell being formed by a depending wall 70 depending from the flywheel 1 and an opposing wall 71 projecting on the opposite side of the depending wall 70. In the arrangement shown, there are four interlocking cells. It should be understood that in alternative arrangements, more or less interlocking cells may be provided. As can be seen in FIG. 24, each interlocking cell results in a head difference K in the water or other fluid F trapped between the walls 70, 71. Cumulatively, a head difference is formed that is equal to the pressure head in the air cushion. In FIG. 24, where there are four cells, the air cushion head is equal to 4K. The walls 70, 71 extend in a circumferential direction. As will be readily apparent to one skilled in the art, the walls 70, 71 are not particularly limited as to material or configuration. Although the depending wall 70 is shown depending from the circumferential wall 3 of the flywheel 1, in an alternative arrangement the circumferential wall 3 may be omitted and the depending wall 70 may be attached directly to the underside 82 of the deck 5. The wall 71 may be attached to a suitable foundation 72 which may be concrete or other. The fluid F in the labyrinth seal traps the gas within the opening 2 to define an air cushion. The flywheel 1 may incorporate any of the flywheel features described above in any combination. In a preferred example, the flywheel may be a ring having a cover, in the form of the flywheel 1 described with reference to FIG. 21, or the like. Of course, it may be formed in other ways.

[0156] FIG. 24 further illustrates optional fluid injection ports, indicated by arrows 80, which may be optionally positioned for fluid injection into all or selected cells of the sealed maze at suitable points around the periphery of the maze to provide desired operational functions, including but not limited to: Maintaining the optimal head difference K in each selected maze cell by pumping water in or out of the cell. Maintaining an optimal head difference K in each cell by pumping or releasing compressed air into selected maze cells. Draining excess hot water, caused by fluid friction, from selected labyrinth cells and replacing it with cold water. Injecting fluid friction reducing chemicals into the water within selected labyrinth cells. In an alternative configuration, the fluid injection port 80 may be omitted.

[0157] FIG. 24 also illustrates an optional magnetic levitation ("MAGLEV") unit 81, which, as will be appreciated by those skilled in the art, can provide desirable operational functions including, but not limited to, the following: · To convert electrical energy input into stored mechanical energy by induced tangential torque. · Conversely, converting stored rotating mechanical energy into electrical energy output by induced tangential torque. · To provide additional vertical support assistance provided by the air cushion. · The vertical and horizontal positions of the entire flywheel assembly must be maintained within sufficiently tight limits to facilitate construction within practical tolerances. · Limiting the tendency of the entire flywheel assembly to exhibit sympathetic vibrations.

[0158] It is understood that the illustrated configuration of the MAGLEV unit 81 is schematic only and should not be construed as limiting. The MAGLEV unit 81 can take any suitable form, as would be readily apparent to one skilled in the art. The illustrated inverted "V" shape of the interface between the rotating upper portion and the stationary lower portion is only one of many optional configurations that provide both vertical and horizontal support and alignment. Other such optional configurations include, but are not limited to, separate vertical and horizontal MAGLEV units, or configurations where one such separate unit is a MAGLEV unit and the other is a conventional mechanical structure, a diagonal interface forming a large cone or an inverted cone frustum around the entire circumference of the MAGLEV unit 81, an upright "V", a "W" or an "M" shape.

[0159] It should be understood that the MAGLEV unit 81 may be omitted or may further be incorporated into an alternative configuration that omits the labyrinth seal, as will be appreciated by those skilled in the art.

[0160] As used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. These terms are not to be interpreted as excluding the presence of other features, steps or components.

[0161] The features disclosed in the above description or the following claims or the accompanying drawings, where appropriate presented in a specific form, or by means for performing a disclosed function, or in a method or process for achieving a disclosed result, can be used separately or in any such feature combination to realise the invention in diverse forms thereof.

[0162] Although specific exemplary embodiments of the present invention have been described, the appended claims are not intended to be limited to these embodiments only, and the claims should be construed literally, literally, and / or to encompass equivalents.

Claims

1. 1. An electrical power generation and / or power storage apparatus comprising a floating flywheel adapted, in use, to contact a body of liquid for rotation about a substantially vertical axis, an underside of the flywheel including a circumferentially extending opening, gas being trapped within the opening by a surface of the liquid so as to define a gas cushion for supporting the flywheel, in use.

2. The apparatus of claim 1 , wherein the circumferential opening extends substantially continuously around the entire circumference of the flywheel.

3. 3. The apparatus of claim 1 or 2, wherein the flywheel is substantially annular.

4. 4. The apparatus of claim 3, further comprising a cover that is airtight and closes the center of the annulus.

5. 5. The apparatus of claim 4, wherein the cover comprises a frame closed by a shell which may comprise a disk, which may be cellular, or steel, concrete, glass-reinforced plastic, or airtight fabric.

6. The apparatus of claim 4 , wherein the cover closes the opening.

7. 3. Apparatus as claimed in claim 1 or 2, wherein the flywheel includes a pair of spaced circumferential walls which in use depend from the flywheel, and the opening is provided between said walls.

8. The apparatus of claim 7 , wherein one of the circumferential walls is an outer perimeter wall.

9. 3. Apparatus as claimed in claim 1 or 2, wherein the flywheel includes a single circumferential wall which, in use, depends from the flywheel, and wherein the opening is provided by the circumferential wall.

10. 10. The apparatus of claim 9, wherein the circumferential wall is provided at or spaced radially inwardly of the outer periphery of the flywheel.

11. The apparatus of claim 4, wherein a single circumferential wall depending from the flywheel when in use penetrates the surface of the liquid when in use.

12. The apparatus of claim 4, wherein the single circumferential wall depending from the flywheel in use depends substantially vertically in use.

13. 8. Apparatus according to claim 7, wherein the opening is wholly or partly closed by the wall and a deck from which the wall depends, the deck being, in use, substantially parallel to the surface of the liquid.

14. 3. The apparatus of claim 1 or 2, wherein the flywheel has a cellular structure.

15. The opening is wholly or partially enclosed by the wall and a deck from which the wall depends; the flywheel is substantially annular; (1) the deck; (2) a single circumferential wall depending from the flywheel in use; and (3) an airtight cover enclosing the center of the annulus.

15. The device of claim 14, wherein one or more or all of have a cellular structure.

16. 15. The apparatus of claim 14, further comprising a ballast system including one or more valves, said ballast system adapted to control the filling and emptying of said cell with liquid.

17. 17. The apparatus of claim 16, wherein the ballast system further comprises a pump for pumping the liquid into the cells and / or for pumping water out of the cells.

18. 3. Apparatus according to claim 1 or 2, comprising one or more compressors for supplying air to the openings.

19. 3. The apparatus of claim 1 or 2, including one or more sails attached to the flywheel.

20. 20. The apparatus of claim 19, wherein the sail extends substantially around the entire circumference of the flywheel.

21. 20. The apparatus of claim 19, wherein the sail is rigid or flexible.

22. 20. The apparatus of claim 19, wherein a control system is provided to redirect the sail relative to wind direction as the flywheel rotates.

23. 20. Apparatus as described in claim 19, wherein the sail is attached to masts, which may be free-standing or supported by supports extending between the masts, which may include rigging, and which may be adapted so that the sail and rigging can be laid flat.

24. 20. The apparatus of claim 19, wherein there are two or more radially spaced, circumferentially extending arrays of said sails.

25. 3. The apparatus of claim 1 or 2, wherein the flywheel has a diameter of 1500 meters or more.

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