GB2527547A

GB2527547A - Improvements in underwater connections

Info

Publication number: GB2527547A
Application number: GB1411261.9A
Authority: GB
Inventors: Michael Torr Todman; John Richard Carew Armstrong
Original assignee: TidalStream Ltd
Current assignee: TidalStream Ltd
Priority date: 2014-06-25
Filing date: 2014-06-25
Publication date: 2015-12-30
Also published as: GB201411261D0; WO2015197694A1; EP3161304A1; CA2949735C; CA2949735A1

Abstract

An underwater turbine generator is attached to an underwater anchorage 21 using a releasable actuator 25. Because the actuator is releasable it may be used with multiple turbines, and is not permanently exposed to subsea conditions. The anchorage 21 may comprise a spigot 22, and the turbine may comprise a tether 23 and coupling 24 which allows movement in yaw. The actuator 25 is attached to the coupling 24 by arms 27, and is suspended by a cable 26 e.g. from a floating winch. The coupling 24 is retained on the spigot 22 using a sliding key 29, which is inserted or withdrawn by the actuator 25. Once coupling is complete, the actuator 25 is released from the coupling 24 and recovered to the surface. The actuator may be supplied with power from the surface by a power supply 28.

Description

Improvements iii Underwater Connections

TECHNICAL FIELD

This invention relates to underwater connections, in particular connections associated with tidal turbines and the like. Such connections may be mechanical, for example to couple a tidal turbine assembly to an underwater anchorage. Such connections may also convey services, for example, to couple a turbine generator to an underwater power supply cable and the like; the service connection may be one or more of; for example, electrical hydraulic and pneumatic.

BACKGROUND TO THE INVENTION

Underwater turbine generators have been proposed to generate electricity from stream flows, for example tidal flows. In general a turbine assembly is coupled to an underwater anchorage, and is arranged to float in the stream flow below the surface of the water. In one common arrangement the turbine assembly is connected to the anchorage by a tether, and trails in the stream flow; the turbine assembly may be free to pitch roll and yaw according to prevailing stream flow conditions, for example by provision of suitable pivots at the ends of the tether. The tether may be rigid or flexible.

One characteristic of an underwater turbine is that it must be transported to the operating site and coupled to an anchorage. The latter operation is somewhat problematic since a large turbine array may displace several hundred tonnes and be difficult to manage in a strong current. Furthermore it may be necessary to uncouple the anchorage to permit the turbine assembly to be removed for repair and/or replacement.

Underwater conditions are not favourable to mechanical devices, but nevertheless it is essential to ensure that uncoupling of an anchorage can be effected on demand, even after several years' immersion in sea water, Corrosion resistant materials are relatively expensive, and may lack the material properties of toughness, resilience and fatigue resistance which are essential to an adequate mechanical life underwater. Sealing of moving mechanical devices, such as actuators, is problematic and cannot be relied upon. Furthermore power is required for such devices, and thus introduces additional difficulties, especially if far from shore in a relatively hostile environment.

What is required is an inexpensive and reliable means and method of coupling arid uncoupling an underwater device with respect to an underwater anchorage.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an underwater actuator having a latch to releasably couple the actuator to an underwater device, and a driver to engage and disengage a retaining member associated with an underwater anchorage whereby said underwater device is adapted to be coupled and uncoupled with said underwater anchorage, and whereby said underwater actuator is adapted to be removed from said underwater device on demand.

The invention essentially allows the moving parts of an engaging and disengaging device to be mounted on a removable actuator, which may thus be lowered and raised only when a connection or disconnection of the anchorage is required. Furthermore, by latching to the underwater device, the invention provides a secondary benefit of retaining the device in the stream flow before and after connection, The actuator may thus be used for raising and lowering the underwater device, or a part thereof with respect to the anchorage. In the case of an underwater turbine, the actuator may be latched to the free end of a tether prior to connection with an anchorage, arid after disconnection from an anchorage.

In one embodiment the actuator is connected by suspension cable to a floating vessel, such as a barge or boat. A power connection for the actuator may be provided from the vessel, and may be electrical, hydraulic or pneumatic.

The actuator may include a transverse arm to provide for contact between the actuator and anchorage by drifting in the stream flow, The transverse arm may act as a catcher, and engage an upstanding element of the anchorage, such as a pin, Such an arm may define a vee or fork to guide the device and anchorage into substantial alignment. The arm may be compliant or have a compliant element to ensure engagement with the anchorage without substantial shoclç the arm may be controllable, such as by moving elements, to allow engagement with the anchorage in a progressive manner or at a desired rate.

The retaining member may be associated with the device, with the anchorage, or with the actuator. In one embodiment the retaining device is mounted on the actuator prior to engagement with the anchorage and after disengagement from the anchorage; such an arrangement allows the retaining device to be brought to the surface periodically for cleaning and for maintenance.

According to a second aspect of the invention there is provided a method of making an underwater connection between an underwater device and an underwater anchorage, the method comprising attaching said device to an underwater actuator; lowering said actuator to engage said device and anchorage; latching said device and anchorage by moving a retaining member thereof to an engaged condition with said actuator; detaching said actuator from said device; and raising said actuator to the surface.

The method of the invention allows for a minimum of moving underwater components associated with the engagement of the anchorage and underwater device, typically just a sliding key, pin, clip or friction element.

The invention also comprises a method of unmaking an underwater connection between an underwater device and an underwater anchorage, the method comprising lowering an actuator to said anchorage; attaching said actuator to said underwater device at said anchorage; unlatching said underwater device by moving a retaining member to a disengaged condition with said actuator; and raising said actuator to disengage said device and anchorage.

The method of the invention may include making a service connection, for example an electrical connection between a cable associated with the anchorage and a connector mounted on the underwater device. The service connection may be made and unmade automatically upon attachment or detachment of the device, for example by raising or lowering said actuator with respect to the anchorage.

BRIEF DESCRIPTION OF DRAWINGS

Other features of the invention will be apparent from the following description of a preferred embodiment illustrated by way of example only in the accompanying drawings, in which: Fig. 1 is a schematic illustration of an exemplar underwater turbine assembly and underwater anchorage.

Fig. 2 illustrates the invention with actuator and tether in a connected condition.

Fig. 3 illustrates the invention with tether and anchorage in coupled condition, with actuator connected.

Fig. 4 corresponds to Fig. 3 and shows actuator disconnected.

Fig. S illustrates a catcher for the actuator of Figs. 2-4.

Fig. 6 illustrates a connection device for the actuator of Figs. 2-4.

DESCRIPTION OF AN EMBODIMENT

Fig. 1 illustrates an exemplar and somewhat schematic underwater turbine assembly to comprising a tether 11 mounted to an underwater anchorage 12 projecting from the underwater surface H, The tether mounting has capability for one or more of pitch, yaw and roll.

The turbine assembly lies in use below the water surface 14, and in this example comprises a twin booms 15 having the fore portions 16 joined in a Y' shape, and aft portions L/ adapted to contain variable ballast, Arms 18 extend from the booms transversely, and turbine generators 19 are mounted thereon. A suitable electrical connection, not shown, connects the turbines to a power cable on the underwater surface 13. The booms 15 contain hollow chambers to which water may be admitted as ballast 20, so as to adjust the operating height of the turbine assembly. The turbine assembly may be for example ballasted to float between a surface maintenance condition, where the turbine generators are exposed for maintenance, and an underwater contact condition, where the assembly sits on the underwater surface; the latter condition may be appropriate to give stability in strong tidal flows (arow A') or in stormy conditions, and the turbine generators may be inactive in the contact condition.

The turbine assembly of Fig. 1 comprises the essential elements of an underwater stream flow generator, namely a turbine generator 19, a framework 18 to mount the turbine generator and a tether 15, 16, 17 for attachment to an anchorage U, Many kinds of such an assembly have been proposed, and in particular the tether may comprise a single arm, and may be flexible or rigid. The present invention is not tS directed to a particular kind of turbine assembly.

In order to position such an assembly for generation, it must first be attached to the anchorage 12.

Fig. 2 illustrates schematically the present invention, A conventional anchorage 21 is fixed to the underwater surface, and comprises an upstanding spigot 22. A tether 23 of a turbine generator (not shown) terminates at a coupling 24 for engagement with the spigot, For simplicity a coupling which allows movement in yaw (about a vertical axis) is illustrated, but additional degrees of freedom in pitch and roll may be incorporated by provision of suitable pivot axes, for example on the coupling 24. The spigot and coupling may be of any suitable shape; for example the spigot may have a tapering free end, or the coupling may have a narrowing mouth, so as to ease mutual engagement and centralize the components before latching. The anchorage may comprise other kinds of relatively fixed attachment, and need not comprise an upstanding spigot, An actuator 25 is suspended by cable 26 from a floating winch, for example on a boat or barge, and is attached to the coupling by opposed arms 27 (one shown) which grip

S

or otherwise engage the coupling from the side. The arms 27 may be of any suitable kind so long as the engagement is secure, and in this example are moved about a respective vertical axis by a suitable motor (not shown) which may be hydraulic, pneumatic or electric. A single arm or other attachment device may be provided. The motor may be a telescopic strut or the like, acting directly to draw the anis together, or move them apart. A power supply 28 is provided for the motor from the surface, for example from the winch boat or barge. Progressive engagement between the actuator and the device is preferred; for example a pointed shape may be stabbed into a recess, and the actuator rotated to permit insertion of a locking pin to complete the latching operation.

In use the cable 26 supports the weight of the tether 23 and coupling 24; it is assumed that the turbine assembly is floating. The actuator 25 is manoeuvred until the coupling 24 is over the spigot 22, at which point it is lowered so as to be engaged thereon (as illustrated in Fig. 3).

In order to retain the coupling 24 on the spigot 22, a key 29 is advanced by another motor of the actuator 25. The kind of key is not important so long as retention is assured whilst permitting the desired axes of movement of the coupling on the spigot.

As illustrated a flat member with a concave leading edge is advanced as key to engage a pocket or groove of the spigot 22. Alternatively a pin may be pushed through a hole of the spigot.

Once the coupling 24 and spigot 22 are engaged, the actuator 25 is removed by releasing the arms 27. The actuator is then brought to the surface by winching in the cable 26 (Fig. 4), Should it be desired to uncouple the coupling 24 and spigot 22, the actuator 25 is lowered to the coupling and re-latched thereto by operation of the gripping arms 27. Subsequently a motor of the actuator withdraws the key 29, thus allowing winching of the cable 26 to draw the coupling 24 off the spigot 22 (Fig. 1).

The key may be part of the coupling 24 or part of the spigot 22, or may be installed from the actuator 24, and withdrawn therewith.

The arrangement of the invention has many advantages.

Firstly, no mechanism associated with coupling and uncoupling remains with the anchorage, and thus not able to be brought to the surface for repair or replacement: all that is left underwater is the spigot with its groove or engagement recess which is typically made from corrosion resistant material. The key and associated linkages and mechanisms that remain with the device can be made from corrosion resistant material and can be brought to the surface for repair or replacement.

Secondly, the actuator is removed to the surface after each engagement or disengagement and can be maintained, cleaned and serviced as often as necessary.

Thirdly, only one such actuator is required for attachment of each of a plurality of turbine assemblies to respective anchorages; this advantage is particularly usefUl where an array of turbines is installed on the underwater surface.

Fourthly, a permanent power supply to the underwater coupling is not required, thus obviating cost and maintenance thereof Fifthly, when the coupling is released, the tether arm 23 is retained by the cable 26 and may be winched up for attachment to a barge or other floating structure; a separate retaining apparatus is accordingly obviated, along with any risk that the turbine assembly will float away.

Fig. 5 illustrates an alternative embodiment including a catcher 3 1 attached to the actuator 25. The catcher 31 comprises a transverse arm which may be flexible, and which provides a means of engaging the spigot 22 whilst the assembly is moved in the direction thereof prior to attachment. This arrangement avoids the need for precise vertical alignment of the actuator and spigot whilst the actuator is winched down to the required depth, which may be problematic in a stream flow, The catcher 31 permits the assembly to be lowered to the appropriate depth, and then allowed to drift towards the spigot in the stream flow until arrested by contact of the catcher 3 1 with the spigot 22. This stabilizes the assembly for positioning and frirther lowering thereof.

In one embodiment the catcher is mounted at an acute angle so as to present a fork to the spigot, this arrangement allows the spigot 22 to slide to the apex of the fork, whereupon the actuator and spigot will be substantially aligned. A catcher may be provided on one or both sides of the actuator.

Fig. 6 illustrates yet another alternative in which one end of a power cable 33 is carried releasably by an arm 32 of the actuator. Upon connection of the coupling 24 with the spigot 22, the arm permits attachment of the cable 33 to a junction box 34 associated with the coupling. Typically a second power cable runs from the junction box 34 to the or each turbine generator, for example within a hollow tether 23. The arm 32 may be mechanized or movable to attach the cable 33, thereby providing a power connection from the turbine generator to a power grid or other electrical consumer, After connection of the cable 33, the actuator 25 and ann 32 can be disconnected and winched to the surface as previously described. The cable may comprise a signalling or control connection for the turbine assembly, for example to control the pitch of the blades thereot and/or may comprise other services means for instance pipes or lines carrying hydraulic or pneumatic or fibre optics for power or signal transmission.

Any kind of suitable connection arrangement for the cable 33 may be used, for example a plug and socket, the essential feature being that the actuator transports and couples the free end of the cable before being withdrawn to the surface, The arrangement may also be used to disconnect the cable 33 on demand, whilst allowing the actuator to retain the cable end for, for example, lifting to the surface. The cable 33 may be automatically attached upon lowering of the coupling on the spigot, or the arm 32 may be movable between connecting and disconnecting conditions, It will be understood that the illustrated embodiment is schematic, and that materials, sizes and dimensions of components will be selected according to the required duty.

Modifications and alternatives are envisaged within the scope of the appended claims,

Claims

Claims I. An underwater actuator having a latch to releasably couple the actuator to an underwater device, and a driver to engage and disengage a retaining member S associated with an underwater anchorage whereby said underwater device is adapted to be coupled and uncoupled with said underwater anchorage, and whereby said underwater actuator is adapted to be removed from said underwater device on demand.
2. An actuator according to claim 1 and further induding a suspension cable for attachment to a floating winch.
3. An actuator according to claim 1 or claim 2 and further including a power lead for attachment to a floating power source, said power lead providing power for said driver and said latch.
4. An actuator according to claim 3 wherein said power lead is adapted to one or more of electrical, pneumatic and hydraulic power.
5. An actuator according to any preceding claim and further including a transverse arm for engagement with an upstanding underwater anchorage, said arm guiding said actuator for alignment with said anchorage in use.
6. An actuator according to daim 5 wherein said transverse arm is adapted to compliant and/or resilient engagement with said anchorage.
7. An actuator according to claim 5 or claim 6 wherein said transverse arm is movable to cushion engagement with said anchorage.
8. An actuator according to any preceding claim and further including a retention device for attachment to one end of an electrical cable associated with said underwater device.
9. An actuator according to any preceding claim wherein said retaining member is movable between said actuator and said underwater device.
10. An actuator according to any of claims 1-8 and an underwater device, wherein S said retaining member is provided on said underwater device.
11. An actuator according to any of claims 1-8 and an anchorage wherein said retaining member is provided on said anchorage.
12. An actuator according to any of claims 9-11 wherein said retaining member is slidable between a disengaged condition and an engaged condition.
13. An actuator according to claim 12 wherein said retaining member is free of moving parts.
14. An actuator according to claim 12 wherein said retaining member comprises one or more of a pin engageable in a hole of an anchorage, a clip engageable in a groove of an anchorage, and a friction grip element.
15. An underwater actuator according to any preceding claim and including an underwater device comprising a turbine generator and a tether for attaching said turbine generator in an underwater anchorage, said latch being engageable at the free end of said tether.
16. Marine equipment comprising a floating vessel having a winch, a power source, and an actuator according to any of claims I -1 5.
17. A method of making an underwater connection between an underwater device and an underwater anchorage, the method comprising: attaching said device to an underwater actuator; lowering said actuator to engage said device and anchorage; latching said device and anchorage by moving a retaining member thereof to an engaged condition by means of said actuator; detaching said actuator from said device; and raising said actuator to the surface.
18. A method according to claim 17 and further comprising connecting a service supply to said actuator prior to said lowering step, and causing said actuator to connect said service supply to said device prior to said raising step.
19. A method according to claims 17 or 18, and further comprising providing a transverse arm on said actuator, and prior to said engaging step, contacting said arm with said anchorage to guide said actuator to said anchorage.
20. A method according to claim 19 wherein said arm defines a fork, and said method includes drifting said actuator in a stream flow towards said anchorage for contact of said arm with said anchorage.
21. A method according to claim 21, said method including compliant or controllable contact of said arm and anchorage to cushion abutment thereof
22. A method of unmaking an underwater connection between an underwater device and an underwater anchorage, the method comprising: lowering an actuator to said anchorage; attaching said actuator to said underwater device at said anchorage; unlatching said underwater device by moving a retaining member to a disengaged condition with said actuator; and raising said actuator to disengage said device and anchorage.
23. A method according to claim 22 and comprising raising said actuator to the surface,
24. An underwater actuator substantially as described herein with reference to Figs. 2-6 of the accompanying drawings.
25. A method of making and/or unmaking an underwater connection substantially as described herein with reference to Figs. 2-6 of the accompanying drawings.