MARINE POWER GENERATION SYSTEM

Abstract

A turbine assembly (200) for location in river or sea locations having unidirectional or bidirectional flow. The as- sembly (200) has: a support structure (226) and a first turbine system, supported by the support structure (226). The first turbine system has a centre of mass and being pivotally connected to the support structure (226) so that the first turbine system is rotatable, relative to the support structure, about a centre of rotation. The first turbine system includes a first flowing-water driveable turbine (216) for generating power from water flow. The first turbine (216) has an operational axis (322), and is designed for optimum power output when local water flow is aligned with the operational axis (322). The wherein the centre of rotation is spaced away from the centre of mass of the first turbine system in a direction parallel to the operational axis of the turbine. The turbine assembly is arranged to rotate due to local currents, thereby bringing the operational axis towards alignment with local water flow.

Claims

1. A turbine assembly having: a support structure; and a first turbine system, supported by the support structure, the first turbine system having a centre of mass and being pivotally connected to the support structure so that the first turbine system is rotatable, relative to the support structure, about a centre of rotation; wherein the first turbine system includes a first flowing-water driveable turbine for generating power from water flow, the first turbine having an operational axis, and being designed for optimum power output when local water flow is aligned with the operational axis; and wherein the centre of rotation is spaced away from the centre of mass of the first turbine system in a direction parallel to the operational axis of the turbine.

2. A turbine assembly having: a support structure; and a first turbine system, supported by the support structure, the first turbine system being rotatable relative to the support structure; wherein the first turbine system includes a first flowing-water driveable turbine for generating power from water flow, the first turbine having an operational axis, and being designed for optimum power output when local water flow is aligned with the operational axis; and wherein the first turbine system is mounted so as to rotate about a horizontal axis relative to the support structure in response to local water flow so that it brings the operational axis of the first turbine towards alignment with the direction of local water flow.

3. The turbine assembly according to claim 2, wherein: the first turbine system has a centre of mass and is pivotally connected to the support structure so that the first turbine system is rotatable about a centre of rotation; and wherein the centre of rotation is spaced away from the centre of mass of the first turbine system in a direction parallel to the operational axis of the turbine.

4. The turbine assembly of claim 1, wherein the turbine assembly is submersible.

5. The turbine assembly of claim 1, wherein the turbine assembly is configured for operation at the surface of a body of water.

6. The turbine assembly of claim 1, wherein the first turbine system is rotatable independently of the parts of the support structure to which the first turbine system is directly connected.

7. The turbine assembly according claim 1, wherein the first turbine system includes a second flowing-water driveable turbine for generating power from water flow, the second turbine having an operational axis, and being designed for optimum power output when local water flow is aligned with the operational axis; and wherein the operational axes of the first and second turbines are parallel with one another.

8. The turbine assembly according to claim 7, wherein the first turbine system includes a beam connecting the first turbine and the second turbine.

9. The turbine assembly according to claim 8, wherein the first turbine is mounted on one surface of the beam, and the second turbine is mounted on a second, opposing surface of the beam.

10. The turbine assembly according to claim 8, wherein the beam comprises a hydrodynamic foil having a drag coefficient which varies with orientation, and wherein the turbines are mounted on the hydrodynamic foil so that their operational axes are aligned with the orientation in which the drag coefficient of the hydrodynamic foil is at a minimum.

11. The turbine assembly according to claim 1, wherein each turbine has a fairing to reduce hydrodynamic drag.

12. The turbine assembly according to claim 1, wherein each turbine has a fairing having a drag coefficient which varies with orientation, and is lowest in the orientation which is aligned with the operational axis of the turbine.

13. The turbine assembly according to claim 1, wherein the support structure comprises a platform, and the first turbine system is spaced away from the platform by supports around which the first turbine system can rotate about an axis generally parallel to the plane of the platform.

14. The turbine assembly according to claim 13, wherein the first turbine system is supported above the platform.

15. The turbine assembly according to claim 13, wherein the first turbine system is arranged to rotate in response to changes of local water flow so that the turbine blades rotate away from the platform.

16. The turbine assembly according to claim 1, further comprising an actuator to rotate the first turbine system.

17. The turbine assembly according to claim 1, further comprising a brake to resist the rotation of the first turbine system.

18. The turbine assembly according to claim 1, further comprising a second turbine system, supported by the support structure, the second turbine system having a centre of mass and being pivotally connected to the support structure so that the second turbine system is rotatable, relative to the support structure, about a centre of rotation; wherein the second turbine system is of the same design, and is connected to the support structure in the same way, as the first turbine system.

19. The turbine assembly according to claim 1, wherein the assembly is positively buoyant in water, and is anchored to a water bed, so that the assembly is held in a state of floating equilibrium.

20. The turbine assembly according to claim 1, wherein the assembly is variably buoyant in water.

21-68. (canceled)

Description

[0076] Embodiments will now be described with reference to the drawings, in which:

[0077] FIG. 1 is a perspective view of an embodiment of an assembly of the present invention;

[0078] FIG. 2 is a perspective view of another embodiment of an assembly of the present invention;

[0079] FIG. 3 is a detailed perspective view of a portion of the assembly of FIG. 2, showing a turbine;

[0080] FIG. 4 is a side view of an embodiment of an assembly of the present invention.

[0081] FIG. 5 is a perspective view of an onboard control module according to an embodiment of the present invention;

[0082] FIG. 6 is a sectional view of the onboard control module of FIG. 5 shown mounted on an embodiment of a submersible assembly according to the present invention;

[0083] FIG. 7A is a perspective view of an embodiment of the module of the present invention;

[0084] FIG. 7B is a perspective view of the module of FIG. 7A viewed from another angle;

[0085] FIG. 7C is a side view of the module of FIGS. 7A and 7B;

[0086] FIG. 8 is a detailed view of a portion of the module of FIGS. 7A-7C;

[0087] FIG. 9 is a perspective view of the arrangement of some of the components of the module shown in FIGS. 1A-1C, with the outer casing removed;

[0088] FIG. 10A is a perspective view of the docking point of a submersible assembly according to an embodiment of the present invention in which a protective door is closed;

[0089] FIG. 10B is a perspective view of the docking point of the submersible assembly of FIG. 4A in which a protective door is open;

[0090] FIG. 11A is a sectional view of the beginning of an exemplary docking procedure in which the module docks with the submersible assembly, according to the present invention;

[0091] FIG. 11B is a sectional view of an intermediate phase of an exemplary docking procedure in which the module docks with the submersible assembly, according to the present invention; and

[0092] FIG. 11C is a sectional view of a later part of a docking procedure according to the present invention.

[0093] FIG. 1 shows a perspective view of an assembly 100 according to an embodiment. A series of anchoring points 102 are provided on the water bed to which primary anchoring lines 106 are attached. The anchoring lines bifurcate into upper 108 and lower 110 anchoring lines, each of which attaches to the assembly 100 at a different location. It is not necessary for the anchoring system of the present invention to bifurcate in this way, and a single anchoring line is possible.

[0094] The assembly 100 is buoyant in water, with the buoyancy being provided by buoyancy devices 126. These may simply be fixed buoyancy devices such as air-filled tanks, or foam based buoyancy devices. Or they may be variable buoyancy devices which can be selectively flooded with water to reduce their buoyancy or filled with air and sealed to increase their buoyancy. The assembly 100 is held in a state of floating equilibrium by the combination of the upward buoyant force from the buoyancy devices 126 and the downward component of tension in the anchoring lines 106, 108, 110. It is not necessary for the present invention to be anchored in this way. It is possible, for example, for the whole assembly to be a rigid structure permanently affixed to the water bed.

[0095] In some cases, the floating equilibrium holds the assembly on, at or near the water surface, while in other cases the assembly is substantially or entirely submerged in the body of water. In particular, the assembly may be held in a position of floating equilibrium in a fully submerged position.

[0096] The assembly 100 has a support structure 112 in the form of a series of beams linking the buoyancy devices together. These beams provide support to a turbine system 114, which comprises a turbine 116 rotatably mounted to the support structure 112. The turbines 116 are arranged to rotate in response to external forces from a local water flow. This is discussed in more detail below.

[0097] Turning now to FIG. 2, another assembly 200 according to an embodiment of the present invention is shown. The anchoring system is omitted from this Figure, but the anchoring systems discussed above in relation to FIG. 1 could be used in this embodiment too. The assemblies shown in FIGS. 1 and 2 are each suitable for situating at the surface of a body of water or submerging in the body of water.

[0098] The assembly 200 has a set of four buoyancy devices 226, two at each end. Each of these may be fixed or variable, as described above. Each pair of buoyancy devices is spaced apart from one another by a pair of vertical support members 230. The support structure further includes a plurality of horizontal trusses 228 spanning the width of the assembly and connecting the lower buoyancy device 226 at one end of the assembly 200 to the lower buoyancy device 226 at the other end. These trusses 228 may be simple trusses, or they may be hollow and selectively floodable to alter the buoyancy of the assembly. Rising from the trusses 228 are a pair of intermediate vertical supports 232. Between the vertical supports 232, and also rising from the trusses 228, is a central pontoon 234. The central pontoon 234 may be hollow, and may further be air-filled, water filled, or selectively floodable to achieve variable buoyancy, depending on the buoyancy requirements of the system.

[0099] A beam 224 spans between the upper buoyancy device 226 at one end of the assembly 200 to central pontoon 234, and a second beam spans between the upper buoyancy device 226 at the other end of the assembly and the central pontoon 234. Each of these beams is supported approximately at its midpoint by one of the intermediate vertical supports 232.

[0100] Four turbines 216 are mounted on the beam 224 in pairs (each pair being referred to in this embodiment as a turbine system) with one turbine 216 from each pair being located between an intermediate support 232 and a buoyancy device 226, and the other turbine of the pair being located between the intermediate support 232 and the central pontoon 234. Both turbines 216 have their blades facing in the same direction, as explained in more detail below. In this case, the turbine systems are each arranged to rotate independently of the parts of the support structure 226, 232, 234 to which they are directly connected. That is, the turbine system is able to rotate, but the parts of the support structure which it connects to do not rotate.

[0101] One turbine 216 of the pair is mounted on top of the beam 224, and the other turbine 216 is mounted below the beam. When the direction of water flow changes, the turbines 216 and the beam 224 rotate together. Once the direction of water flow has completely reversed, for example when the tide is no longer ebbing, but is flowing instead, the turbines will have rotated so that their turbine blades will be facing in the opposite direction. Moreover, the turbine 216 which was previously situated on top of the beam 224 will then be located below the beam 224, while the turbine 216 which was previously underneath the beam 224 will now be located on top of the beam 224.

[0102] The beam 224 is shaped to act as a hydrodynamic foil, and has a coefficient of drag which changes depending on its orientation relative to local water flow. In particular, it has an orientation of minimum coefficient of drag, and it will rotate to align this with local water flow. This example of a beam has a plane of symmetry, which is beneficial in the present system as it means that it will work equally well when the turbines 216 (and thus the beam 224 as well) are oriented in a first direction as when they are oriented in a second direction opposite to the first direction. It is not necessary that the beam 224 have these hydrodynamic properties, and instead it may simply have the function of connecting the turbines 216 together so that they rotate as a single unit. In fact, in some embodiments the beam 224 may not even be arranged to connect the turbines 216 in this way. It may simply serve as an axis around which the turbines 216 rotate, while remaining static relative to the rest of the support structure.

[0103] A turbine 316, mounted on a beam 324 (once more shaped to act as a hydrodynamic foil) is shown in more detail in FIG. 3. This Figure shows a turbine 316 mounted as described in relation to the embodiment shown in FIG. 2. It will, however, be clear to the skilled person that the detailed description of the turbine 316 may be applied to other embodiments, in particular those with a larger or smaller number of turbines than the four shown in FIG. 2.

[0104] The turbine 316 has a generally elongate body, contained in nacelle 320 located at the front (upstream) end of the turbine 316. The nacelle 320 provides a streamlined enclosure within which generators are housed, as well as optionally other equipment, for example AC/DC converters, transformers, sensing equipment, or actuators and/or brakes for controlling the rotation of the turbine 216. The streamlined shape helps to reduce drag on the structure as a whole. Although the nacelle 320 is shown as smooth in this embodiment, fins, foils or other hydrodynamic shapes can be included to assist the turbines 316 in interacting with local water flows to cause them to rotate.

[0105] Any suitable generator for the anticipated water current and turbine characteristics can be provided. However, in one particular embodiment, the generator is arranged to receive rotational motive power and convert it into a more useful form of energy, typically electrical energy. The machinery of the generator is often relatively heavy compared with the rest of the turbine 316, and tends to result in the centre of mass of the turbine 316 being located towards the middle, or even towards the front (upstream end) of the nacelle 320.

[0106] Mounted at the rear (downstream end) of the nacelle 320 are turbine blades 318. Typically these are mounted on a driveshaft which feeds into the generator. The blades 318 are shaped and mounted so that water flow from the nacelle 320 to the blades 318 will cause them to rotate. A dashed line 322 represents the operational axis of the turbine 316. The turbine 316 is designed so that when the operational axis 322 is aligned parallel to the direction of local water flow, the turbine 316 achieves optimum power generation for a given local water flow rate. Primarily this is achieved by altering the shape and mounting angle of the turbine blades 318.

[0107] As shown, the turbine is mounted on the beam 324 towards the rear (downstream end) of the nacelle 320. Since in this embodiment the turbine 316 rotates along with the beam 324 and the centre of mass of the turbine 316 is inside the nacelle 320, this means that the point of rotation and the centre of mass of the turbine are not at the same place. In other words, they are spaced apart from one another.

[0108] This arrangement causes a torque due to gravity on the turbine 316, tending to rotate the turbine 316 (and the beam 324 in this embodiment) so that its rear end points downwards (i.e. its operational axis 322 tends towards the vertical). When there is a water current, this torque can be counteracted, at least in part, and a position of stable equilibrium can be attained, in which the front end of the nacelle 318 receives the water current first, which flows over the nacelle 320 and the beam 324, before reaching the turbine blades 318.

[0109] When the water flow hits the turbine blades 318, they rotate, and cause the driveshaft to rotate too, thereby feeding rotational power to the generator and causing useful power, e.g. electrical power, to be generated. This process results in the turbine blades 318 generating a large drag force which provides a counter-torque to the torque due to gravity acting on the centre of mass of the turbine 316, thus stabilising the turbine 316 in the water flow, with its operational axis 322 dragged away from the vertical, and closer to alignment with the water flow.

[0110] Since the position of equilibrium attained in this way depends on the water flow, the turbine 316 responds dynamically to changes in water flow. In particular, water flow in a first direction will hold the turbine aligned with the water flow in a first direction, for example in the direction shown FIG. 3. Then, as the flow rate drops, the drag force reduces causing the torque due to gravity to be opposed less and less strongly, and the turbine 316 rotates until the turbine blades are at the top. This is because, absent any external forces, the centre of mass (located at the middle or front of the nacelle 320) will tend to move to place itself directly below (as determined by the local gravitational field) the centre of rotation. As the water flow increases again, for example in a second direction opposite to the first direction as would be seen in a tidally dominated system, the drag forces on the turbine 316 increase, and oppose the gravitational torque. This time, the drag forces cause the turbine 316 and beam 324 to rotate to align with the second direction of water flow, that is to say, the turbine 316 faces in the opposite direction to that shown in FIG. 3.

[0111] The hydrodynamic shape of the beam 324 may assist the turbine 316 in rotating from the orientation in which the operational axis 322 is vertical, by presenting a large drag coefficient while the turbine operational axis 322 is vertical, and a progressively lower drag coefficient as the orientation of the operational axis approaches alignment with the local direction of water flow. In addition, water flowing over the foil 324 first, and the turbine 316 later helps to smooth the flow, and improve power generation from the turbine 316.

[0112] FIG. 3 shows a single turbine 316 mounted on a beam 324, along with a second, adjacent beam. The adjacent beam may also have a turbine mounted on it, and both turbines may be arranged to rotate in a pair, along with their respective beams. This may be achieved, for example, by forming the hydrodynamic foil as a covering on a generally cylindrical beam. The fairing may then extend up to the intermediate support 332 which separates the two portions of fairing from one another. The intermediate support 332 may further have an aperture comprising bearings to allow the cylindrical beam to pass through and rotate. The second portion of fairing and second turbine may then be provided on the other side of the intermediate support 332 in a similar manner.

[0113] The turbine 316 in FIG. 3 is shown mounted on top of the beam 324, although clearly when the turbine 316 rotates to adapt to a change in current flow direction, this may change, and the turbine 316 may later located below the beam. It is entirely possible to mount the turbine 316 in such a way that the nacelle 320 extends as equally as far above and below the beam 324. This arrangement may be preferred for systems in which turbines 316 may rotate independently of any other turbines on the assembly, including single turbine assemblies. This is because a turbine 316 can only align its operational axis 322 vertically by using gravity alone, if the centre of mass is spaced apart from the centre of rotation along a line parallel to the operational axis 322. Clearly this requires that the axis about which the turbine 316 rotates must intersect the operational axis 322, which further requires that the beam 324 supports the turbine 316 in such a way that it intersects the nacelle 320, rather than passing above or below it. Allowing the operational axis 322 to self-orient vertically in the absence of external forces means that the turbine 316 is not biased towards a particular direction of current flow.

[0114] As described above, turbine 316 may be arranged to rotate together with a second turbine, by virtue of sharing a common beam 324. In this arrangement, both turbines 316 and the beam 324 are collectively known as a turbine system. The turbine 316 shown in FIG. 3 is mounted above the beam. In order to reduce torques on the support structure, and also to allow the turbine system to orient the operational axes of the two turbines vertically, the second turbine should be mounted below the beam with its operational axis parallel to that of the first turbine, and separated from the common axis of rotation (as defined by the beam 324 with which both turbines collectively rotate) by the same distance as the first turbine 316 is separated from this axis, when the two turbines are of identical design. This is equivalent to saying that the centre of mass is the same height for rotational deflections of equal magnitude in either direction relative vertically oriented operational axes 322, so there is no inherent preferred direction for the turbines to rotate towards.

[0115] This detailed description has proposed mounting the turbines 316 with the beam 324 providing a centre of rotation for the turbines 316 located between the centre of mass and the turbine blades, so that in the absence of external forces the turbine 316 rotates to vertically orient its operational axis 322 with its blades 318 uppermost. However, it is entirely possible to arrange the mounting location of the turbine 316 on the beam 324 so that the centre of mass of the turbine 316 is located between the beam 324 and the turbine blades 318. In this case, the turbine 316 may still rotate to align its operational axis 322 vertically, but in this configuration, the blades 318 represent the lowest point of the turbine 316.

[0116] While the foregoing has described how turbines 316 may use forces generated by interacting with local water streams to bring their operational axes 322 towards alignment with local water flow, even with assistance from the beam 324 and its hydrodynamic properties, it may not be possible to exactly align the turbine operational axis 322 with the local water flow. It is therefore contemplated that an actuator may be provided to rotate the turbine 316 or the beam 324 to make small corrections, and thereby improve power generation.

[0117] Additionally, the turbine 316 or beam 324 may be supplied with a brake to resist rotation. This may allow the turbine to be locked in a particular position, for example it may be used to lock a turbine 316 with its operational axis 322 aligned with local current flow, even as the strength of the flow drops. This ensures that the turbine 316 keeps its operational axis 322 aligned with the flow, even when the flow is not strong enough to fully counteract the gravitational torque.

[0118] Finally, a brake may also be useful in retaining the turbine 316 in the orientation in which its operational axis 322 is vertical, to inhibit power generation, for example if repairs are being carried out to the assembly, or if the flow rate is outside safe limits.

[0119] Turning now to FIG. 4, the mounting of turbines 416 in pairs is clearly shown. This Figure shows a side view of the embodiment of FIG. 3. In addition to the buoyancy devices 426; trusses 428; central pontoon 434; end 430, and intermediate 432, vertical supports already described in detail in reference to FIG. 2, it can clearly be seen that each pair of turbines 316, situated either side of the central pontoon 434, comprise a turbine 416 mounted above the beam 424 and a turbine 416 mounted below the beam 424. It is also clear that each turbine is spaced away from the central plane of the beam by the same distance, whether above it or below it.

[0120] The view in FIG. 4 shows the importance of carefully selecting the direction in which the turbine blades should point when there is no current flow. If the turbines 416 were arranged to rotate so that their blades are the lowest point of the turbine in the absence of external forces (i.e. the centres of mass of the turbines 416 are located between the beam 424 and the turbine blades), then there is a danger that the blades could collide with the trusses 428 or other parts of the support structure, damaging the device. Therefore, the turbines 416 are mounted with the beam 424 between their centres of mass and their blades in this embodiment.

[0121] Of course designs are contemplated where the support structure forms a platform similar to that shown in FIG. 4, but where the turbines are mounted vertically below the platform, instead of above it, as shown in FIG. 4. In this case, the arrangement in which the centres of mass of the turbines 416 are located between the beam 424 and the turbine blades would be appropriate to ensure that the blades rotate to the bottom of the turbines 416 in the absence of external forces. In general, the turbines rotate in such a way as to cause the blades to rotate away from the platform.

[0122] Arrangements where the turbines are mounted below the platform may be preferable for assemblies configured to remain on, at or near the surface of a body of water during normal operation because the main body of the assembly can float near/on the surface, while the turbines are suspended below the main body. This allows a combination of the ease of a surface-based assembly with the improved power generation obtained by positioning the turbines high in the water column, but away from floating debris.

[0123] Finally, it should be noted that the support structure could also be designed in such a way that there was sufficient clearance for the blades that the turbines can rotate in any direction, in which case the above considerations are less important.

[0124] Turning now to FIG. 5, there is shown an embodiment of a centralised onboard control module 536 according to a second aspect of the present invention. This design comprises an upper torispherical dome portion 338 and a lower generally cylindrical portion 540. These are joined together by a watertight seal 542.

[0125] The control module 536 contains electronic control systems for the turbine assembly, for example to control actuators or brakes on the turbines of the assembly to change their rotational status. In principle, this allows these water-sensitive components to be sealed on dry land, to protect them from water damage, and subsequently the module 536 can be attached to the turbine assembly and submerged. In the event of accidental damage, the centralised nature of these control systems allows them to be easily removed and repaired.

[0126] The control module 536 is provided with a mounting bracket 544 or similar means so that it can be simply mounted and/or detached as the need arises. In particular, the control module 536 may be removable in its entirety form the assembly. For example, in the event that the module develops a fault, or needs an upgrade, the assembly may be raised to the surface, the module removed, and repairs or replacement of the module can be made, as appropriate.

[0127] In addition, other systems such as hydraulic actuators, mechanical actuators, pneumatic systems, and high power electrical equipment may also be housed in the module 536. This allows easy and centralised access to these key systems, while keeping them safe in a dry space. Centralising in this way means that fewer spaces need be sealed, and monitored to ensure safe working of the apparatus.

[0128] Externally, the module is provided with cable feedthroughs 546 for outputting control signals (in the form of electronic, or other suitable, e.g. fibre optic, signals) or electrical power as required, or for receiving electrical power e.g. from the turbines, for processing with high power electrical equipment prior to transferring to an external location, e.g. for feeding into a local electricity grid.

[0129] There may further be provided mechanical, hydraulic or pneumatic feedthroughs (not shown) for transferring mechanical power from corresponding mechanical, pneumatic or hydraulic actuators located inside the module 536 to the rest of the assembly. These may be used, for example to adjust the anchoring system of the turbine assembly, or to control the variable buoyancy.

[0130] FIG. 6 shows a sectional view through the central pontoon of the embodiment of a turbine assembly 600, as shown in FIGS. 2 and 4. The buoyancy devices 628 and vertical end supports are visible 630, as is a turbine 616. The central pontoon 634 is shown with the centralised onboard control module 636 mounted in a recess. As discussed above, the mounting of the module may be permanent, or it may be removable for repair or replacement purposes. This arrangement is purely exemplary, and the control module 636 may be recessed in a different location, or even to the exterior of the assembly, depending on the desired outcome.

[0131] Indeed, as set out in the description below, this consolidation of control and actuation components can be further developed to allow a plurality of turbine assemblies to share some or all of these components, by allowing the module to be detachable, and in some cases autonomous or semi-autonomous. In particular, the systems only used intermittently can be grouped into a separable module.

[0132] Referring to FIG. 7A, there is shown a module 700 supported from above by cables 704. The support cables 704 attach to the module 700 at four points 702. In this arrangement, the module 700 may be supported from above, for example by a ship on the surface of a body of water using a crane, and lowered into position using the cables 704.

[0133] The module 700 may be lowered into the correct position using the cables, and either manual or automatic guidance. For example, the module 700 may be provided with automatic guidance and control systems which detect the location of an assembly with which the module is configured to dock, and control the module in order to direct it to the desired location. Additionally or alternatively, the module 700 may be manually controllable, wherein an operator makes control adjustments to the module 700 to guide it to the correct location.

[0134] Both automatic and manual guidance may be assisted by passive guidance means, in the form of cables or chains along which the module 700 can slide, to arrive at the correct destination. The cables need not be permanently attached to the intended destination of the module 700, but may themselves be removable. Indeed, passive guidance may even be used to entirely replace both automatic and manual guidance.

[0135] The module itself 700 is provided with a protective cage 706, or protective struts, on its upper surface. This cage 706 provides protection to some of the systems provided on the module 700. For example, the module 700 is shown with four hydraulic rams 708 for adjusting the positions of onboard actuators, located inside module 700. In addition, there are two hydraulic rams 712 for lowering a stab plate located on the lower surface of the module 700. In addition, there is a control module 716 on the upper surface. The control module 716 may house various electronic control systems, onboard power supplies, hydraulic machinery, or any combination of these, for example. In addition, the control module 716 may provide a convenient attachment point for an umbilical cable (not shown) to provide external power or control signals to the module 700. Each of the six hydraulic rams 708, 712 and the control module 716 are located within the protective cage 706. Of course, it is not essential that hydraulic rams be used, and instead, electronic or pneumatic means could be employed for this purpose.

[0136] The lower portion of the module 700 is covered by a protective fairing 718. The fairing 718 in this embodiment tapers so that the module 700 is narrower at its lower end that it is at its upper end. Of course, the fairing 718 could in principle be any shape, or indeed there could be no fairing at all in some embodiments.

[0137] Inside the fairing 718 may be variable buoyancy means, for example one or more floodable ballast tanks. The buoyancy can be reduced by selectively filling such tanks with water, and increased by emptying the water, e.g. forcing the water out, using compressed air. Alternatively, variable buoyancy means may be located outside the module 700, for example on top of the module 700.

[0138] Visible on the lower surface of the module 700 are a set of four toothed wheels 709 which provide a means for transferring power from actuators on the module 700 to the assembly. The toothed wheels have protrusions, or teeth, on their faces, so that when the module 700 is docked, the protrusions engage with corresponding recesses on the assembly thereby allowing rotational power to be transferred to the assembly. Each of the toothed wheels 709, together with a corresponding actuator, may be raised or lowered individually and selectively by a corresponding hydraulic ram 708 to engage or disengage with the corresponding portions of the assembly. The hydraulic rams may operate together or independently to engage or disengage each toothed wheel from its corresponding part on the assembly. As shown, the four toothed wheels 709 are in the extended (lowered) position.

[0139] Also visible on the lower surface of the module 700 are three alignment pins 713 which help to ensure that the module 700 is correctly aligned with the assembly. In addition, three hydraulic interconnects 714 are shown on the lower surface of the module 700. These allow the module 700 to provide an alternative type of motive power to the assembly when it is docked. The alignment pins 713 and the hydraulic interconnects 714 collectively form a stab plate, and may be raised and lowered together by actuating hydraulic rams 712. As shown the stab plate is in its extended, (lowered) position.

[0140] Turning now to FIG. 7B, the module 700 is shown from a slightly different view. Here, the base of the module 700 is visible, and the toothed wheels 709 and the stab plate are shown in the retracted (raised) position. Also visible is a protective base plate 720. The base plate 720 protects the alignment pins 713, the hydraulic interconnects 714 and the toothed wheels 709 from accidental damage when they are in the retracted position. The base plate has a set of holes through which the alignment pins 713, the hydraulic interconnects 714 and the toothed wheels 709 may be extended so that they can be used to supply hydraulic power and rotational motive force to the assembly when required. Of course, it is not necessary that the stab plate and toothed wheels 709 are extendable and retractable, and embodiments where these components have a fixed position are envisaged.

[0141] In addition, locking mechanisms 722 are visible on the lower surface of the module 700. Each locking mechanism comprises a hydraulic piston 723 and a locking tooth. The locking arrangement is described in more detail below, in relation to FIG. 8.

[0142] Turning now to FIG. 7C, a third view of the module 700 is provided. In this view, hydraulic rams 708 and 712 have all been activated, and consequently toothed wheels 709, alignment pins 713 and hydraulic interconnects 714 are in the extended (lowered) position.

[0143] FIG. 8 shows a close-up view of the module 700 of FIGS. 7A to 7C, and in particular, shows a detailed view of a locking mechanism, generally denoted by numeral 822, mounted on the base of module 800. The locking mechanism comprises a hydraulic ram 823, an engaging tooth 824, and a housing 825. The hydraulic ram will typically be retracted, causing the engaging tooth to be retained in the housing, at times when the module is not docking with the assembly. When the module is aligned with the docking point on the assembly, the locking mechanism 822 is activated, and the hydraulic ram extends 823, forcing the engaging tooth 824 out of the housing 825. FIG. 8 shows the engaging tooth extended even though the module is not aligned with the docking point on the assembly. However, when the module is aligned with the docking point on the assembly, the engaging tooth is arranged to extend to grip a bar to hold the module firmly against the assembly.

[0144] While only a single locking mechanism 822 is shown in FIG. 8, it is clear from FIG. 7B that two locking mechanisms 822 may be employed, or even more, depending on the specific requirements. Also, while the locking mechanism 822 in FIG. 8 makes use of a hydraulic ram 823 to move the engaging tooth 824, it will be apparent that any actuator may be used for this job, including pneumatic systems, electromechanical systems, and electromagnetic systems.

[0145] Moreover, the design of the engaging tooth 824 is clearly dependent on the design of the corresponding portions of the assembly, although it will be apparent to those skilled in the art how to design two such corresponding parts. Indeed, it is not even essential to use an engaging tooth, for example electromagnets could be used to selectively clamp the module firmly to the assembly.

[0146] FIG. 9 illustrates some of the internal parts of the module 900, by removing e.g. the fairing (718, FIGS. 7A to 7C), and supporting internal frame. Here, the four toothed wheels 909 are shown suspended from their respective actuators 910. In the Figure the actuators 910 are electric motors, but it will be apparent to the skilled person that other types of actuator could be used in the place of the electric motors without affecting the functionality of the module 900.

[0147] Additionally, each toothed wheel 909 and corresponding actuator 910 is slidably mounted on a set of guide rods 911. The guide rods 911 ensure that the actuator 910 and toothed wheel 909 extend in the desired direction when the hydraulic ram (not shown in FIG. 9) extends to push the actuator 910 and toothed wheel 909 to the extended (lowered) position. That is to say, that the guide rods 911 ensure that the toothed wheels 909 remain aligned with their counterparts on the assembly as they are lowered into position by the hydraulic ram.

[0148] Also shown in FIG. 9 is an imaging system, in this case comprising five cameras 926 each having a line of sight 927. The cameras are mounted so that their lines of sight collectively cover a wide field, to aid an operator in aligning the module with the docking point on the assembly. Optionally, the cameras may include a sonar system or other imaging means, or indeed, the imaging system may be entirely sonar-based, or based around another imaging technology. Additionally, supplementary tools for assisting an operator in executing the docking procedure correctly may be supplied as part of the imaging system. For example, lights may be provided, in the event that the local lighting conditions are insufficient for the cameras to be of use, lasers may be used to locate key features, or used as part of a ranging apparatus.

[0149] Moving on to FIG. 10A, the docking point 1050 on the assembly is shown, although the body of the assembly is omitted in this view. In FIG. 10A, a set of protective doors 1054 are shown in their closed configuration. Typically, the doors 1054 will be biased towards the closed position, so that the interface of the docking point remains covered. Of course, it is not essential that doors are provided at all. In general, it is intended that the upper surfaces of the doors 1054 are flat and flush with the outer body of the assembly when the doors at in the closed position to reduce drag on the assembly. However, it is also possible to form the docking point as a protrusion extending outwards from, or in an uncovered cavity within, the assembly.

[0150] At the lower portion of the docking point is a base plate 1056 supported by girders 1057. These provide support for the module as it is brought into contact with the assembly. In particular, it is important that these are designed to withstand heavy loads in the event that the module collides with the assembly at relatively high speeds, due for example to operator error, or rough water conditions.

[0151] The docking point may also include an electrical connection for transferring control signals, electrical power, or both to the assembly. Depending on the specific design requirements, there may be more than one electrical connection. For example, separation of power and control signals may be desirable to reduce interference. Similarly, the control signals may not be electrical in nature, but may comprise fibre optic connections, for example. This may have the advantage that control signals need not be made electrically, which can be expensive and prone to failure when implemented underwater. Indeed, even for surface-based assemblies, it is may be desirable to reduce the number of electrical connections where possible, due to problems encountered due to splashing water.

[0152] Turning now to FIG. 10B, the docking point 1050 is presented from the same view, but this time with doors 1054 in their open configuration, in which the interface is not covered by the doors. Normally, the doors 1054 are biased towards a closed position unless the module has caused them to open. The module may cause the doors 1054 to open in a variety of ways. For example, the doors 1054 may be simply biased using a spring or other mechanical biasing means, and the module may simply push the doors out of the way as it is lowered into position. Alternatively, the doors 1054 may be controlled by an actuator, which detects the module's proximity and causes the door to open, for example. Further methods of implementing this functionality will be apparent to those skilled in the art.

[0153] Also visible in the cutaway view of the docking point in FIGS. 10A and 10B are spools 1061 and pulleys 1062 which will be discussed in more detail below, with reference to FIGS. 11A to 11C.

[0154] FIGS. 11A to 11C are sectional views showing progressive stages of a docking procedure in which a module 1100 docks with a docking point 1150 of an assembly. FIG. 11A shows a view early on in the procedure, in which the module 1100 is located above the assembly, and is being lowered into position, supported by support cables 1104 connected to the module 1100 at attachment points 1102 (visible more clearly in FIGS. 11 B and 11C).

[0155] The doors 1154 of the docking point are in their closed position, and the interface is therefore covered. In this Figure the docking point 1150 is recessed into the body of the assembly so that the outer casing 1152 of the assembly is flush with the doors 1154. The module 1100 has protective skids 1107 on its lower surface. These skids 1107 are arranged to contact the doors 1154 of the docking point 1150 as the module 1100 is lowered into position, and push the doors into their open configuration, thereby allowing the module 1100 access to the interface of the docking point 1150.

[0156] FIG. 11 B shows a view of the docking procedure just as the module 1100 has settled into position at the docking point 1150. Note that the fairing 1118 of the module 1100 is tapered towards its lower surface. This assists the alignment of the module 1100 with the docking point 1150, as the opening formed when the doors 1154 open is wider than the lowest portion of the module 1100, so it is not essential that the module 1100 be perfectly aligned with the docking point 1150 at the start of the docking procedure. In this way, the doors 1154 of the assembly form part of a particular type of passive guidance system for locating the module 1100 correctly. As the module 1100 is further lowered into position, the doors 1154 guide the module 1100 into finer alignment by contacting the tapered fairing 1118. This allows the docking point 1150 to act as a socket, into which the module 1100 can be inserted, acting as a plug.

[0157] In FIG. 11B, the locking mechanisms 1122 are engaged and the engaging teeth grip corresponding portions on the docking point 1150. In this case it grips bars 1172 to hold the module in place.

[0158] Finally, turning to FIG. 11C, the module 1100 is shown fully docked with the docking point 1150. In particular, the stab plate comprising alignment pins 1113 and hydraulic interconnects 1114 has been lowered by extending hydraulic rams 1112. This causes the alignment pins 1113 to slide into their corresponding recesses 1163 on the assembly. Similarly, the hydraulic interconnects 1114 are aligned with and connected to corresponding hydraulic interconnects 1164 on the assembly, thereby allowing the module 1100 to supply hydraulic motive power to the assembly.

[0159] In addition, the actuators 1110 and corresponding toothed wheels 1109 have been lowered into position by actuating hydraulic rams 1108. This causes the toothed wheels 1109 to engage with corresponding teeth 1160 of the docking point 1150. The teeth 1160 of the docking point are located on spools 1161, which can be driven by the module 1100 when it supplies rotational motive power to the assembly. In this way, the spools 1161 can act as a winch, drawing in or releasing cable as required. In this way adjustments to the orientation or position of the assembly can be made. For example, the cables which are drawn in or released by the spool 1161 may be anchoring cables for the assembly. By including a system of pulleys in the design of the assembly, the cables can be fed through to any part of the assembly, and form an attachment point for the anchoring system at that part of the assembly.

[0160] The module 1100 may thus centrally control the tension in each anchoring cable, and is able to change the orientation or the position of the assembly by adjusting each anchoring cable individually. Additionally or alternatively, the module 1100 may control ballast tanks or other variable buoyancy means associated with the assembly. Furthermore, the module 1100 may be used to adjust control surfaces on the assembly. For example, the assembly may have various surfaces, such as hydrofoils, or angled surfaces which can be moved. By changing the angle of these surfaces with respect to local current flow, the lift generated by them may be altered (even possibly making the lift negative). The lift is also dependent on the strength or speed of the local current flow, and therefore making these adjustments can result in dynamic adaptation of the lift of the assembly to changes in local currents.

[0161] Once the module 1100 has completed the required adjustments to the orientation and/or position of the assembly, it is detached from the docking point 1150. This process is in effect the reverse of the docking procedure, involving: retraction of the actuators 1110, toothed wheels 1109 and stab plate; disengagement of the locking mechanisms 1122; and raising the module 1100 away from the assembly. As the module 1100 moves away from the assembly, the doors 1154 close and cover the interface to protect it from damage.

[0162] The assembly to which the control module docks can be the turbine assembly shown in FIGS. 1 to 6, or indeed a marine assembly for any other purpose. The assembly may be submerged, submersible, or surface-based.