GB2504516A

GB2504516A - A sub aquatic coupling for electrical connection hub

Info

Publication number: GB2504516A
Application number: GB1213659.4A
Authority: GB
Inventors: Paul Vigars; Matthew Hawthorne; James Sheppard
Original assignee: Tidal Generation Ltd
Current assignee: Tidal Generation Ltd
Priority date: 2012-08-01
Filing date: 2012-08-01
Publication date: 2014-02-05
Also published as: GB201213659D0; WO2014020346A3; WO2014020346A2

Abstract

An underwater structural coupling mechanism comprises first 312 and second 314 components which can be matably engaged. An alignment mechanism relatively rotates the first and second components when they are engaged, so that they connect only in predetermined circumferential orientations. The first component 312 may have a shaft 346 with three guide channels 358, and the second component 314 may have complementary guide rails 396. The coupling may include electrical connectors 320, 322 radially outwards of the shaft 346. The second component may be lowered by a removable winch 370, and may be retained by a clamp (362: figure 3b) from above the second component 314, which axially urges the two components together. The coupling may support an electrical connection unit 318 for connecting an array of turbines to an electrical grid (figure 2).

Description

A Sub-Aquatic Structure

Technical Field of Invention

This invention relates to a sub-aquatic structure having two components which are required to be mated underwater. In particular, the invention relates to a sub-aquatic structure which provides a connection module or hub for an electrical network.

Background of Invention

Sub-aquatic power generating apparatuses are generally well known and currently the subject of much research and development. One type of sub-aquatic power generating apparatus is the tidal turbine generators 10 shown as part of an array 1 in Figure 1. These generators 10 include a turbine 12 mounted on a support structure 14 which is fixed, either by gravity or some other suitable fixing means, to the sea bed 16. The turbine 12 includes a rotor 18 having a plurality of turbine blades 20 which are arranged to provide rotative force about a principal axis 22 when placed in an appropriate flow of water 24. The rotor 18 is used to drive an electrical machine in the form of an electromagnetic generator (not shown) which is housed within the so-called nacelle or casing of the turbine 12. The electromagnetic generators currently used in tidal turbines are typically conventional and simply converts the rotational mechanical movement provided by the rotor into electrical energy.

To fully exploit a particular tidal resource, arrays of turbines 10 are co-located. Each unit is typically connected to a common connection point on land by a suitable arrangement cable 26. However, this arrangement is inefficient in that numerous cables are required to export the electricity and each may stretch over several kilometres in length.

The present invention seeks to provide an improved arrangement for providing a more efficient exportation of electricity to an onshore location from an array of sub-aquatic power generators.

Statements of Invention

The present invention provides a sub-aquatic structure comprising: a first component; a second component, wherein the first component and second component are mateably engaged along a mating axis when in use; and, an alignment mechanism which is arranged to relatively rotate the first and second components when the first and second components mateably engage one another along a mating axis.

The arrangement of the invention provides a device which can be readily and passively aligned to provide electrical connections between a base and a connecting unit.

The alignment mechanism may comprise a guide and channel arrangement. The channels may include a rotation portion and an axially extending portion. The axially extending portion may be straight. The depth of the channel may be increase along its length. The change in depth of the channel may provide axial alignment of the first and second components. The rotation portion may include a funnelled portion which reacts with the guide acting under gravity to rotate the second component. Alternatively, the rotation may be forceably induced. For example, the first and second components may be forced towards one another by an actuator. The actuator may be a winch system. As a further alternative, the rotation may occur due to the buoyancy of one or other of the first and second components in some configurations. There may be three channels or a multiple thereof.

The first component may be anchored to bed of water and includes one part of two part electrical connector. The second component may include the other part of the two part connector. The two part connector may be a male and female arrangement such as a plug and a socket. The two part connector may be a wet mate connector. The wet mate connector may be any connector suitable for transferring electrical power or data from the first component to the second component. The connectors may include fibre optic connectors. The data may be transferred by fibre optic or some other suitable medium.

The first component and second component may be mateably attached via a two part coupling which includes a shaft extending from one of the first or second components and a corresponding mating aperture which is part of the other of the first or second component.

The shaft may include one or more of a receiving portion, a rotational alignment portion, a clamping portion and a radial correction portion.

The first component may be anchored to the sub-aquatic bed and the second component may be winched on to the first component with a winch cable. The winch may be part of a winch assembly which is detachably mounted to the second component. Alternatively, the winch assembly may be fixed to the first or second component.

The winch cable may be arranged so as to be substantially coaxial with the mating axis when in use in slack water.

The second component may include at least one guide member through which the winch cable passes. The guide member may provide the alignment with the mating axis.

The guides may be guide rails attached to the inside of the mating aperture. In other embodiments, the guides may be pins or some other suitable feature.

The guide members may be movable between a first configuration and a second configuration. The first configuration may involve a first end of the guide members cooperating to provide an aperture for guiding the winch cable. When in the second configuration the guide members may provide guide rails which engage with the channels to provide the alignment mechanism. The guide members may be pivotably attached to the second component. The guide members may provide gated access to the mating aperture when in the first configuration. The guide members may be hingedly connected to the inside of the mating aperture.

The second component may be buoyant.

The electrical connectors may be located radially outwards of the alignment mechanism.

This is particularly advantageous as it allows for a greater number of electrical connections to be made per structure whilst keeping the alignment and clamping means to the minimum size required to provide the necessary support.

The structure may further comprise a clamp which is operable to retain the first component in a fixed relation to the second component. The clamp may be arranged to clamp around the shaft. The clamp may include a plurality of arcuate segments. The arcuate segments may be hingedly connected together and actuable to constrict about the shaft. The acutator may be one of hydraulic, pneumatic or electrical. The actuator may be a mechanically biased device. The mechanical bias may be a spring. The mechanical bias may be releasably attached. The release may be achieved with a remote operated vehicle.

The clamp may be located above the first component so as to be accessible from above the second component. The clamp may be located on an upper surface of the second component. The clamp may be attached to the first or second component.

The clamp may be configured to urge the first and second components together in an axial direction when constricting around the shaft. The clamp may include a radially extending tapered flange. The taper may be received by a corresponding recess in the shaft. The tapered flange and recess may be arranged to translate the constricting force into an axial force.

The base of the shaft may include a frustum which engages with a corresponding aperture in the mating aperture so as to concentrically align the first and second components upon axial displacement. The frustum provides the radial correction. Alternatively, the radial correction portion may be provided by altering the depths of the channels such that the contact with the guides provides the concentric alignment.

The first component may include an anchor to which electrical cables are attached and the second component is a connection unit which provides a common connection point between a plurality of incoming and outgoing cables. The electrical generators may be tidal turbines. The second component may include one or more of electrical isolation and protection devices, transformers and electrical conditioning equipment such as filters of convertors. Data processing or communication modules which are used to issue commands to and process data from each of the turbines in the array.

Description of Drawings

Embodiments of the invention will now be described with the aid of the following drawings of which: Figure 1 shows the previously described array of tidal turbines.

Figure 2 shows a tidal turbine array having a sub-aquatic structure of the present invention.

Figures 3a and 3b show a sub-aquatic structure according to the present invention in uncoupled and coupled configurations respectively.

Figures 4a and 4b shows guide members which cooperate to provide a guide for a winch cable.

Figures 5a and 5b show a clamp arrangement.

Detailed Description of Invention

Figure 2 shows a tidal turbine array 21 having a plurality of turbines 210 similar to those described in Figure 1. However, in Figure 2, the tidal array 21 includes a further sub-aquatic structure in the form of a hub 230 which provides a local common connection point for each of the turbines 210.

Each turbine 210 is electrically connected to the hub 230 via a suitable electrically insulated cable 232. Inside the hub 230, the cables 232 are electrically connected together and to a main export cable 234. The export cable 234 is connected to an electrical network or grid on shore (not shown). The hub 230 may also contain electrical isolation and protection devices, transformers to increase the generated voltage to a more favourable voltage for exportation and electrical conditioning equipment such as filters or convertors. Data processing or communication modules which are used to issue commands to and process data from each of the turbines 210 in the array 21 may also be included in the hub 230.

Figures 3a and 3b show a schematic cross-section of a sub-aquatic structure 310 having a first component 312 and a second component 314 in non-mated and mated configurations, respectively. In the presently described embodiment, the sub-aquatic structure 310 provides the hub 230 referred to above in relation to Figure 2, but it will be appreciated that other uses of the invention may be envisaged.

The first component 312 of the sub-aquatic structure 310 is in the form of a base which is anchored to the seabed 316 so as to provide a stationary platform to which the second component 314 can be mateably secured in use. Thus, the second component 314 is in the form of an electrical connection unit 318 which provides a common coupling point in which electricity from the tidal turbines 210 is exported to a mainland grid or the like. By anchored, it will be appreciated that the second component is retained in a given location when in use. Thus, the method of anchorage is not specific and any suitable known way will suffice. For example, the base may be anchored using gravity, grouted pins or shear keys.

To provide a more convenient arrangement from a maintenance point of view, the connection unit 318 includes all of the electrical equipment, such as circuit breakers and the like, desirable to provide the suitable interconnection of the turbines 310 and export cable 334 and is designed to be repeatedly deployable and retrievable from the base 312 to the surface. To help enable this functionality, the electrical cables 332 which extend from each turbine 210 and the export cable 334 are attached and terminated on the base 312 with the electrical connection between the base 312 and connection unit 314 being achieved via a plurality of electrical connectors in the form of so-called wet mate 319 connectors.

The wet mate connectors 319 are two part electrical connectors having corresponding respective nominal plug 320 and sockets 322 which can be coupled underwater. Thus, in use, a plurality of cables, each from a tidal turbine 210, are attached to the base 312 and terminated in one end of the two part electrical connector 319. The corresponding part of the wet mate connector 319 is mounted on the connection unit 318 such that the two are mated when the connection unit 318 is mateably coupled to the base 312. In this way, each cable 332, 334 is connected in the appropriate way to the required switch gear etc housed within the connection unit 318. The size and rating of the wet mate connectors will be application specific, however, an engagement length of between 250mm and 350mm is to be expected in some applications. Further, it will be appreciated that the straight portion of the alignment channels described below will need to be long enough to allow for the engagement length of the wet mate connectors.

Although there would typically be an amount of local adjustment and location features such as pins and channels in the mountings of the connectors, it will be appreciated that the connection between the plug 320 and sockets 322 of the wet mate connectors 319 on the base 312 and connection unit 318 need to be generally aligned with a reasonable amount of accuracy when they are initially brought together. To provide the alignment the first 312 and second 314 components include respective and corresponding parts of an alignment mechanism 324 which is arranged to relatively rotate the first 312 and second 314 components when they mateably engage along a mating axis 326.

The first component 312 includes an anchor 328 and a platform 330. A shaft 336 which extends upwards towards the surface of the water in a perpendicular and substantially vertical direction is mounted towards a central portion of the platform 330. The shaft 336 is arranged to be matedly received within the connection unit and provide structural support sufficient to securely anchor the connection unit 318 to the sea bed 316 via the base 312.

The shaft 336 is generally cylindrical having a longitudinal axis 338, a proximal end 340 which adjoins the platform 330 and a distal end 342 which receives the connection unit 318.

The longitudinal axis is coaxial with and defines the aforementioned vertically extending mating axis 326 along which the connection unit 318 is received. The shaft 336 includes an optional radial correction portion 344 at the proximal end 340, a rotational alignment portion 346 along a mid section, a clamp portion 348 towards the distal end and a receiving portion 350 at the distal end 342.

The radial correction portion 344 is located at and provides the junction between the shaft 336 and the platform 330 which includes a chamfered or frusto-conical portion 352. The sloped surface of the frusto-conical portion 352 provides the shaft 336 with an increasing thickness towards the platform 330. This sloping surface provides a guide for a corresponding portion of the connection unit 318 to engage with and sit upon and provide a final radial correction prior to the wet mate connectors 319 marrying up.

The rotational alignment portion 346 extends along the shaft 336 from the radial correction portion 344 towards the distal end 342, and forms the male part of a male and female alignment mechanism which rotationally aligns the base 312 and connection unit 318 as they axially engage one another. The rotational alignment portion 346 includes guide channels 354 which are formed by projections or ribs 356 located on the outer surface of the shaft. The guide channels 354 have a straight descending portion 357 which extends from the proximate end 340 of the shaft 336 towards a fluted or funnelled entrance 358 located towards the distal end 342. The channels 354 are configured to receive a second part of the rotational alignment portion 346 in the form of guide pins or rails 360 which are part of the connection unit 318. There are three channels placed around the shaft so as to provide the alignment mechanism 324 with three degrees of rotational symmetry. However, other degrees of rotational symmetry may be implemented.

The distal end 342 of the rotational alignment portion 346 adjoins a clamp portion 348 for receiving a clamp 362. The clamp 362 is part of the connection unit 318 and is in the form of a collar 364 which is configured to constrict around the clamping portion 348 of the shaft 336 so as to attach to it and retain the base 312 in place. To assist with the clamping, the clamping portion 348 of the shaft 336 includes an annular groove 364 around the circumference of the shaft 336 which is sized and shaped to receive a corresponding flange of the clamp 362. More detail of the clamp arrangement is provided in FigureS below.

The distal end 342 of the shaft 336 includes receiving portion 350 in the form of a chamfered circumferential edge which provides a sloped tip 336 for receiving the connection unit thereon.

The connection unit 318 provides a common point for coupling an array of turbines 210 to an electrical grid. The connection unit 318 includes a housing 366, an alignment part 368, a detachable winch assembly 370, a clamp 362, a radial correction portion 372 and a plurality of wet mate connector parts 322 as previously described.

The housing 366 is in the form of a cylindrical or torpedo shaped canister having a mating aperture 374 in the form of an opening which passes from an upper surface to a lower surface of the housing 366 into which is received the shaft 336 of the base 312. Within the housing 366 there is contained the various electrical equipment necessary to perform the required electrical connection in an acceptable manner. Thus, the housing 366 may contain electrical isolation and protection devices, transformers and electrical conditioning equipment such as filters of convertors. The housing may also include some form of data processing or communication modules which are used to issue commands to and process data from each of the turbines in the array. It will be appreciated that all of these or other items may be included as needed for a particular application.

The connection unit 318 of the described example is buoyant which aids the deployment and retrieval of the connection unit 318 and the electrical equipment housed within. The buoyancy is provided by any suitable scheme which may involve, for example, having adequate gas filled volume, such as a sealed space filled with air, within the housing 366.

Having volumes which are effectively dry to provide the buoyancy in this way is also advantageous for the electrical equipment which can be of a lower specification.

Although buoyant, the housing 366 may include some form of ballast (not shown) to help stabilise the connection unit 318 for surface towing purposes and to provide a favourable centre of buoyancy for maintaining the mating aperture 374 in a more or less vertical attitude whilst the unit is winched down to the base 312.

The detachable winch assembly 370 includes a support structure 380 in the form of a scaffold or frame which is detachably attached via a suitable mechanism to the top of the housing 366 of the connection unit 318 and supports a winch 382. The winch 382 includes a drive unit located on the upper surface 376 of the housing 366 above the mating aperture 374 such that a winch cable 384 can be controllably fed out along the mating axis of the mating aperture 374 in and out as required. The winch cable 384 passes through the mating aperture 374 and a winch guide 386 before descending to be attached to the top of the shaft 336 via an appropriate mechanism such as a metal hook or loop. The winch is configured such that when connected it can be powered to lower or raise the connection unit towards the base and on to the shaft 336.

As shown in Figure 4, the winch guide 386 is formed from three coplanar guide members 390 or arms which extend from the inner surface of the mating aperture 374 at a location which is towards the lower surface of the connection unit 318. The free ends 392 of the guide members 390 are shaped so as to cooperate to form a guiding aperture 394 through which the winch cable 384 passes so as to be in line with the mating axis 326 when in use.

The guide members 390 are attached to the inner wall of the mating aperture 374 via a pivotable arrangement in the form of a hinged connection 396. The hinged connection 396 is arranged such that the free ends 392 of the guide members 390 are free to move unhindered in an upwards extending arc until the length of the guide members 390 are aligned with the walls of the mating aperture 374 in a vertical orientation. In this configuration the guide members form guide rails which are arranged to cooperate with the guide channels 354 on the shaft 336. There are three guide members in the described embodiment, each positioned to correspond with and engage in one of the guide channels on the shaft as shown in Figure 4b which represents a cross section through the shaft 336 towards a mid-point thereof.

Other forms of guides are also contemplated. Hence, in other embodiments, the guide members may fold out of the way completely with dedicated guides in the form of pins or the like being provided. Further, the underside of the guide members may include formations or features to provide the guiding functionality. The guide members could also be received within or combine with other features which act to strengthen the guide members and prevent any unwanted lateral deflection or distortion when the first and second components are mating.

In yet another embodiment, additional features such as pins could be included to complement the guides in the alignment of the first and second components.

In a yet further embodiment, the channels could be provided on the electrical connection unit, and the guides be provided on the second component, namely on the shaft.

In order to couple the base 312 and connection unit 318 together a circumferential clamp 362 which extends around the clamping portion 348 of the shaft 336 is provided as shown in Figures 5a and Sb in respective plan and partial cross-sectional views. The clamp 362 is attached to the upper side 376 of the connection unit housing and is made up from a plurality of arcuate sections 512 which are movable relative to each other so as to constrict (or dilate) around the shaft 336. As shown in Figure Sb, each arcuate section 512 includes an axially extending arcuate plate 514 which wraps around the shaft 336 with a tapered flange 516 extended radially inwards from the lower end thereof. The tapered flange 516 corresponds to a taper within the recessed annular groove 364 of the clamping portion 348.

The clamp 362 is tightened using an appropriate actuator 518 such as a hydraulic ram (as shown) or lead screw for example. The actuator 518 is operable to bring the ends of the clamp 362 together and constrict around the clamping portion 348. In doing so, the corresponding tapers of the groove 364 and flange 518 react with one another and drive the connection unit 318 down onto the shaft 336, thereby providing a greater force than can be achieved with the winch and helping to ensure that the wet mate connections 319 are properly made.

Both the tapered flange 516 and the taper of the groove 364 may be provided with low friction liners (not shown) which aid the insertion of the flange 516 into the groove 364 and increase the downward force created by the constriction of the clamp 362. It will be appreciated that other arrangements or an omission of the tapers can be provided.

The clamp 362 can be driven by a remote operating device which is part of the winch assembly and carried on the scaffold.

A further explanation of a general clamp arrangement and a suitable method of actuation are described in GB2448710, which is incorporated by reference. It will be appreciated that the flange arrangement in GB'710 differs from the present example in its function and the specific arrangement of the tapered surfaces, but the general constricting mechanism is similar to that required for the present purpose.

The arrangement of the channels 354, guide rails 390 and wet mate connectors 319 are rotationally symmetric about the mating axis 326. In the present embodiment, each channel is separated by 120 degrees so as to provide three degrees of rotational symmetry. The rotational symmetry advantageously allows the connection unit 318 to be mounted in any of the angular positions which in turn reduces the amount of rotational alignment which will be required during the mating process. In the described example, where there are three channels the most the connection unit 318 will have to rotate is 60 degrees.

Further, having three degrees of symmetry lends itself more readily to three phases systems in which each degree of rotational symmetry includes one or more connections for each phase of a three phase system. That is, each phase for a given turbine may have an individual wet mate connector and each of these may be separated by 120 degrees around the mating axis. Hence, the connection unit can be mated in any one of the three degrees of rotation and still connect to three phases of each turbine. It will also be appreciated that there may be more than three degrees of rotational symmetry. For example, there may be multiples of three degrees of rotational symmetry e.g. 3, 6 or 9, or other multiples of rotational symmetry which do not correspond to a three phase distribution.

It will be apparent that providing rotational symmetry in the described way will result in arbitrary connections between the wet mate parts of the connector unit 318 and base 312.

Hence, the connection unit 318 may include some form of registration means which allows turbines to be matched to equipment within the connection unit 318. In this way, a particular circuit breaker or isolator can be assigned to a given turbine, regardless of the orientation of the connection unit 318. Further, it may be necessary to provide some form of cross over switching to allow the phases to be interconnected as required.

The lower extremity of the mating aperture includes a frusto-conical portion which corresponds to that of the radial correction portion on the shaft 336.

In use, the cables 332 from each of the turbines 210 are laid across the sea bed 316 and attached to the base 314 via a suitable clamp or restraint. The conductors of the cables 332 are terminated in the respective wet mate connector 319 ready for coupling to the connection unit 318. It will be appreciated that prior to these connections being made, the base 318 will have been appropriately anchored to the seabed 316.

The connection unit 318 is deployed from a vessel which is located above the base 312. A remote operated vehicle is used to connect a free end of the winch cable to the base attachment. Once connected the winch is operated so as to pull the hub down through the water to the base. The arrangement of the hub and its centre of buoyancy, the guide rope and winch guide are such that the hub is located directly above the base and is drawn down in a line from vertically above, allowing of course for any ambient currents or the like which may move the turbine off line.

The first contact between the connection unit and base occurs between the receiving portion 350 and the guide members 386, the latter of which are urged upwards by the downwards motion of the connection unit 318. Once folded back, the guide members 386 become guide rails which enter the funnelled entrance 358 of guide channels 354 and descend therein as the winch 382 continues to wind in. Depending on the angular alignment of the connection unit 318 and base 312, the guide rail will contact a shoulder of the funnel 358 and rotate the connection unit 318 as it descends until the guide rail enters the distal end of the straight segment 357 of the channel 354. At this point the connection unit 318 and base 312 are substantially aligned as required for the mating of the wet mate connectors 319.

The last stage in the alignment is achieved using the radial correcting portion 344. This occurs when the corresponding frusta of the connection unit 318 and base 312 contact. A final portion of axial translation then mates the wet mate connectors and electrical connection is made.

The clamp 362 is then operated to constrict around the clamping portion 348 with the tapered flange 516 and groove 364 engaging to firmly urge the connection unit downwards and into position.

The winch cable 384 can then be released from the top of the shaft 336 and returned and attached to the vessel on the surface of the water. Releasing the winch assembly 370 from the top of the housing and operating the winch returns the winch assembly to the vessel.

It will be appreciated that the scope of the invention is defined by the claims below and the above description of the embodiments is illustrative. In some embodiments, the winch assembly may not be detachable and may not be a band clamp. For example, the clamp may be a so-called over centre clamp or other suitable arrangement. Further, clamp actuator may be retained on one of the components or removed with the winch or separately. 11.

The guide rails may not be provided by the guide mem bers but may simply be pins or the like located within or adjacent to the mating aperture. The connection unit may not be buoyant and as such may not be needed to be winched down. Rather the connection unit may be a so-called heavy hub with negative buoyancy which may simply be lowered into place. The shape of the connection unit housing may be any suitable for accommodating the equipment. The connections may include or be limited to fibre optic cables for data communication between the first and second components. Further, the connections may not have rotational symmetry about the mating axis. In other embodiments, the guide channels may have a profiled depth so as to provide axial alignment as the mating of the first and second components progresses.

Claims

CLAIMS: 1. A sub-aquatic structure comprising: a first component; a second component, wherein the first component and second component are niateably engaged along a mating axis to provide an interconnected structure; and, an alignment mechanism which is arranged to rotate the first and second components relative to one another when the first and second components mateably engage one another along the mating axis.
2. A sub-aquatic structure as claimed in claim 1 wherein the alignment mechanism comprises a guide and channel arrangement.
3. A sub-aquatic structure as claimed in claim 2 wherein channels include a rotation portion and an axially extending portion
4. A sub-aquatic structure as claimed in claims 2 or 3 wherein there are three channels or a multiple thereof.
5. A sub-aquatic structure as claimed in any preceding claim wherein the first component is anchored to bed of water and includes one part of a two part electrical connector, and wherein the second component includes the other part of the two part connector.
6. A sub-aquatic structure as claimed in any preceding claim wherein the first component and second component are mateably attached via a two part coupling which includes a shaft extending from one of the first or second components and a corresponding mating aperture which is part of the other of the first or second component.
7. A sub-aquatic structure as claimed in claim 6 wherein the shaft includes one or more of a receiving portion, a rotational alignment portion, a clamping portion and a radial correction portion.
8. A sub-aquatic structure as claimed in any preceding claim wherein the first component is anchored to the sub-aquatic bed and the second component is winched on to the first component with a winch cable.
9. A sub-aquatic structure as claimed in claim 8 wherein the winch is part of a winch assembly which is detachably mounted to the first or second component.
10. A sub-aquatic structure as claimed in claims 8 or 9 wherein the winch cable is arranged so as to be substantially coaxial with the mating axis when in use in slack water.
11. A sub-aquatic structure as claimed in any of claim 8 to 10 wherein the second component includes at least one guide member through which the winch cable passes, the winch guide providing the alignment with the mating axis.
12. A sub-aquatic structure as claimed in any of claims 2 to 11 wherein the guides are guide rails attached to the inside of the mating aperture.
13. A sub-aquatic structure as claimed in claim 11 or 12 wherein the guide members are movable between a first configuration and a second configuration, wherein when in the first configuration a first end of the guide members cooperate to provide an aperture for guiding the winch cable, and when in the second configuration the guide members provide guide features which engage with the channels to provide the alignment mechanism.
14. A sub-aquatic structure as claimed in any preceding claim wherein the second component is buoyant
15. A sub-aquatic structure as claimed in any of claims 5 to 14 wherein the electrical connectors are located radially outwards of the alignment mechanism.
16. A sub-aquatic structure as claimed in any preceding claim further comprising a clamp which is operable to retain the first component in a fixed relation to the second component when the first and second components are mateably engaged.
17. A sub-aquatic structure as claimed in claim 16 wherein the clamp is located above the first component so as to be accessible from above the second component. The clamp may be located on an upper surface of the second component. The clamp may be attached to the second component.
18. A sub-aquatic structure as claimed in claims 16 or 17 wherein the clamp is configured to urge the first and second components together in an axial direction when constricting around the shaft.
19. A sub-aquatic structure as claimed in claim 6 to 18 wherein the base of the shaft includes a frustum to provide the radial correction portion, the frustum engaging with a corresponding aperture in the mating aperture so as to concentrically align the first and second components upon axial displacement.
20. A sub-aquatic structure as claimed in any preceding claim wherein the first component is an anchor to which electrical cables are attached and the second component is a connection unit which provides a common connection point between a plurality of incoming and outgoing cables.