AU2006281969B2

AU2006281969B2 - A mooring

Info

Publication number: AU2006281969B2
Application number: AU2006281969A
Authority: AU
Inventors: Timothy Donegal Finnigan
Original assignee: Biopower Systems Pty Ltd
Current assignee: Biopower Systems Pty Ltd
Priority date: 2005-08-12
Filing date: 2006-08-11
Publication date: 2011-10-06
Anticipated expiration: 2026-08-11
Also published as: AU2006281969A1

Abstract

A mooring (10) for connecting an ocean energy capturing device (51) to a seabed (16) is disclosed. The mooring (10) comprises a base (12) adapted for connection to the ocean energy capturing device (51). A plurality of anchor bolts (18) are each connected at a first end to the base (12) and have a second end adapted to be embedded in the seabed (16) for attaching the base (12) to the seabed (16). A method of securing the ocean energy capturing device (51) to the seabed (16) is also disclosed. The method involves passing a tensile transmission line (46) through a guide opening (44) in the base (12) and drawing the tensile transmission line (46) through the guide opening (44) to drag the ocean energy capturing device (51) toward the base (51).

Description

1 A Mooring Technical Field The present invention relates generally to moorings, and in particular, to a mooring for 5 anchoring an ocean energy capturing device to the seabed. The present invention has been developed primarily for use in the field of hydroelectricity generation, and will be described hereinafter with reference to this particular application. However, it will be appreciated that the invention may also be used for mooring offshore 10 wind turbines, subsea pipelines, and other structures, either offshore or on land. Background of the Invention Known moorings for ocean energy capturing devices include large fixed gravity bases, clump or drag anchors, and pile moorings. 15 A disadvantage of known moorings is that they have limited application across varied water depths, seabed materials and bathymetric conditions. Another disadvantage of known moorings is that they occupy a large area, and also do not provide adequate resistance to both lateral and rotational forces in all conditions. Many known moorings also require substantial 20 seabed preparation and levelling prior to installation. Another disadvantage of known moorings is that they are large and unwieldy, making them difficult to deploy and install. Known moorings often require special large-bore drilling rigs to create a socket in the seabed, in which a large-diameter monopole is inserted. This known 25 method of installation is very expensive. A further disadvantage of known moorings is that their large size and complexity makes them prohibitively expensive. Any discussion of documents, acts, materials, devices, articles or the like which has been 30 included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

2 Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, 5 or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Summary of the Invention In a first aspect, the present invention provides a mooring for connecting an ocean 10 energy capturing device to a seabed, said mooring comprising: a base adapted for connection to the ocean energy capturing device, the base including a socket engageable by the ocean energy capturing device for connecting the ocean energy capturing device to the base, the socket being tapered and of non-circular cross-section, with a larger diameter end of the socket being at the end furthest from the 15 base; and a plurality of anchor bolts, each having a first end and a second end, to be embedded in the seabed and connected to the base for attaching the base to the seabed. The socket is preferably adapted for engagement with a complimentary spigot on the ocean 20 energy capturing device. Preferably, the socket is provided in a generally cylindrical boss located substantially centrally on the base. A plurality of circumferentially spaced buttress supports preferably extend between a radially outer periphery of the boss and the base. An annular flange 25 preferably extends radially outwardly from an open end of the socket. Preferably, the annular flange includes apertures for receiving fasteners for connecting the ocean energy capturing device to the base. The guide opening is preferably provided in the radially outer periphery of the boss. 30 Preferably, a first pulley wheel is connected to the base. More preferably, the first pulley wheel is located adjacent the end of the socket closest the base. A second pulley wheel is preferably located adjacent the guide opening. In a second aspect, the present invention provides a method of securing an ocean energy 3 capturing device to a seabed, said method comprising the steps of: providing a mooring comprising: a base adapted for stationary mounting to the seabed and for connection to the ocean energy capturing device; 5 a tapered socket on the base, the socket being of non-circular cross-section; and a guide opening in the base, the guide opening adapted to receive a tensile transmission line therethrough for guiding the ocean energy capturing device toward the base for engagement therewith; 10 securing the base relative to the seabed; connecting one end of the tensile transmission line to the ocean energy capturing device; passing the tensile transmission line through the guide opening; drawing the tensile transmission line through the guide opening to drag the ocean 15 energy capturing device toward the base; and connecting the ocean energy capturing device to the base by engaging a tapered spigot on the ocean energy capturing device with the tapered socket on the base. A larger diameter end of the socket is preferably located at its end furthest from the base. 20 Preferably, a first pulley wheel is connected to the base. More preferably, the first pulley wheel is located adjacent an end of the socket closest the base. A second pulley wheel is preferably located adjacent the guide opening. Preferably, the tensile transmission line is passed around the first and second pulleys during said drawing. 25 The present disclosure also provides a mooring for connecting an ocean energy capturing device to a seabed, said mooring comprising: a base adapted for connection to the ocean energy capturing device; a plurality of legs extending from the base for engagement with the seabed to 30 distribute loads from the base to the seabed; and a plurality of anchor bolts, each having a first end and a second end, to be embedded in the seabed and connected to the base for attaching the base to the seabed. Preferably, the base has a generally planar mounting surface. 35 4 Preferably, the anchor bolts are connected at the first end to the base by lock nuts. The second end of the anchor bolts is preferably adapted to be embedded in the seabed by one of: drilling and grouting, screwing and locking by expansion, or direct driving. A spherical joint is preferably provided between the lock nuts and the base. In some embodiments, the 5 anchor bolts extend in a direction generally perpendicular to the plane of the base, and in other embodiments, at least some of the anchor bolts are offset from said perpendicular direction. Preferably, at least one of the legs is adjustable to allow for adjustment of the orientation of 10 the base relative to the seabed. Preferably, the base includes a generally planar mounting surface which is adapted for positioning substantially parallel with the plane of the seabed. A pad is preferably connected to a seabed engaging end of each of the legs for distributing loads transferred to the seabed through the legs. More preferably, the pad is tailored to the prevailing seabed conditions. 15 The present disclosure also provides a mooring for connecting an ocean energy capturing device to a seabed, said mooring comprising: a base adapted for connection to the ocean energy capturing device, the base comprising a generally planar mounting surface which is adapted for positioning 20 substantially parallel with the plane of the seabed; an apron extending from the base for engagement with the seabed to distribute loads from the base to the seabed; a rubble rim formed around the apron; and a plurality of anchor bolts, each having a first end and a second end, to be 25 embedded in the seabed and connected to the base for attaching the base to the seabed. Preferably, the apron has a peripheral lip extending in a direction substantially normal to the plane of the base. The apron is preferably substantially circular. 30 The present disclosure also provides a mooring for connecting an ocean energy capturing device to a seabed, said mooring comprising: a base adapted for connection to the ocean energy capturing device, the base forming the top of a suction caisson to be secured to the seabed by a vacuum pressure; and 4a a plurality of anchor bolts, each having a first end and a second end, to be embedded in the seabed and connected to the base for attaching the base to the seabed. 5 Brief Description of the Drawings Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings wherein: Fig. I is a schematic elevational view of a preferred embodiment of a mooring; -5 Fig. 1 A is a schematic fragmentary elevational view of an alternate anchoring arrangement for the mooring of Fig. 1; Fig. 1 B is a schematic elevational view of an alternative embodiment of a mooring; Fig. 2 is a schematic top perspective view of the mooring of Fig. 1; 5 Figs. 3A and 3B are schematic views showing a preferred method of connecting an energy capturing device to a mooring. 10 15 20 25 30 The next page is page 9 WO 2007/019609 PCT/AU2006/001150 -9 Detailed Description of the Preferred Embodiments As best shown in Fig. 1, the mooring 10 comprises a base 12 adapted for connection to an ocean energy capturing device (such as those disclosed in the Applicant's earlier filed Australian Provisional Patent Application Nos. 2006904031 and 2006904032 and the co 5 pending international patent applications claiming Convention priority therefrom, the disclosures of which are incorporated herein by reference). The base 12 includes a generally planar mounting surface 13 which is adapted for positioning substantially parallel with the seabed 16. The base 12 also includes mounting apertures 17 through which a plurality of anchor bolts 18 are installed. A first end of the anchor bolts 18 is 10 adapted for connection to the base 12 by lock nuts 20, and a second end of the anchor bolts is adapted to be embedded in the seabed 16 for attaching the base 12 to the seabed 16. The anchor bolts 18 have a diameter substantially less than that of the mounting apertures 17 to compensate for minor misalignment of the anchor bolts 18 and mounting apertures 17. Washers 21 are provided between the base 12 and the lock nuts 20. 15 As shown in Figs. 1 and 1A, depending on seabed conditions, the anchor bolts 18 can either be installed in a direction generally perpendicular to the plane of the base 12 (i.e. vertically), or can be offset from the perpendicular direction (i.e. inclined relative to vertical). A spherical joint 22 is provided between the lock nuts 20 and the base 12 to 20 ensure that tension in the anchor bolts 18 is transferred vertically downwardly through the base 12 even if the anchor bolts 18 are inclined. The other end of the anchor bolts 18 is connected to the seabed 16 by drilling and grouting, screwing and locking by expansion, or direct driving. 25 In the embodiment shown in Figs. 1, lB and 2, three legs 24 extend from the base 12 for engagement with the seabed 16 to distribute loads from the base 12 to the seabed 16. The legs 24 are adjustable to allow for adjustment of the orientation of the base 12 relative to the seabed 16. A pad 26 is connected to a seabed engaging end of each of the legs 24 for distributing loads transferred to the seabed 16 through the legs 24. The characteristics of 30 the pads 26 are tailored to the prevailing seabed conditions. In the embodiment shown in Fig. IB, the legs 24 are replaced by a substantially circular apron 28, which extends from the base 12 for engagement with the seabed 16 to distribute loads from the base 12 to the seabed 16. The apron 28 has a peripheral lip 30 extending WO 2007/019609 PCT/AU2006/001150 -10 in a direction substantially normal to the plane of the mounting surface 15 (i.e. vertically). A rubble rim 32 is formed around the apron 28 to protect the apron 28 against scour and erosion. 5 As best shown in Fig. 2, a generally cylindrical boss 33 extends substantially perpendicularly from the base 12. The boss 33 includes a socket 34 engageable by the ocean energy capturing device for connecting the ocean energy capturing device to the base 12. The socket 34 is tapered, with a larger diameter end of the socket being at the end furthest from the base 12. The socket 34 is also of non-circular cross section. The 10 cylindrical boss 33 located substantially centrally on the base 12. A plurality of circumferentially spaced buttress supports 38 extend between a radially outer periphery of the boss 33 and the base 12 to strengthen the connection between the base 12 and the boss 33 against lateral forces exerted by the wave energy capturing device due to wave forces. An annular flange 40 extends radially outwardly from the open end of the socket 34 and is includes apertures 42 for receiving fasteners (not shown) for connecting the ocean energy capturing device to the base 12. A guide opening 44 is provided in the radially outer periphery of the boss 33. The guide opening 44 is adapted to receive a tensile transmission line, in the form of a cable 46, 20 therethrough for guiding the ocean energy capturing device toward the base 12 for engagement with the socket 34. A first pulley wheel 48 is connected to the base 12 adjacent an opening 49 in the lower end of the socket 34. A second pulley wheel 50 is located adjacent the guide opening 44. 25 The process of connecting the ocean energy capturing device 51, which is buoyant, to the seabed 16 is shown schematically in Figs. 3A and 3B. Firstly, the desired location on the seabed 16 is selected. The base 12 is then transported to this location and lowered into position, where it will rest under its own weight, even in moderate wave/current 30 conditions. If required, the lengths of the legs 24 are adjusted to compensate for any unevenness in the seabed 16. The anchor bolts 18 are then connected to the seabed 16, through the mounting apertures 17 in the base 12, by drilling and grouting, screwing and locking by expansion, or direct driving. Lock nuts 20 are next screwed onto the upper WO 2007/019609 PCT/AU2006/001150 - 11 ends of the anchor bolts 18 and tightened against the base 12 to apply a tension to the anchor bolts 18 to secure the base 12 to the seabed 16. With the base 12 now securely connected to the seabed 16, the cable 46 is passed down 5 through the centre of the socket 34, around the first 48 and second 50 pulley wheels, and through the guide opening 44. One end of the cable 46 is then connected to the ocean energy capturing device 51 and the other end to a tug boat 52. The boat 52 is then driven away from the base 12 to draw the cable through the guide opening 44 and drag the ocean energy capturing device 51 down onto the base 12 for connection thereto. The ocean 10 energy capturing device 51 includes a tapered spigot 54, of non-circular cross section complimentary with that of the socket 34, for engagement with the conical socket 34. The non-circular cross sections of the socket and spigot facilitate the automatic alignment of the apertures 42 around the socket 34 with corresponding apertures (not shown) around the spigot 54. When the spigot 54 and socket 34 are engaged, a retaining mechanism (not 15 shown) automatically engages to temporarily connect the ocean energy capturing device to the base until fasteners (not shown) are installed through the apertures 42 to fixedly connect the ocean energy capturing device 51 to the base 12. Once the fasteners (not shown) are installed, the cable is disconnected from the ocean energy capturing device. 20 It will be appreciated that the illustrated mooring advantageously has a relatively low environmental impact on the seabed due to the provision of the plurality of anchor bolts, which distribute loads applied to the seabed through the base. The configuration of the mooring also advantageously allows the base to have a relatively small footprint, which also reduces negative impacts on the seabed environment. The provision of the adjustable 25 legs 24 also advantageously allows the mooring to be used in uneven seabed conditions. Also, the alternative configuration utilising the apron advantageously allows the mooring to be used in relatively soft or unstable seabed conditions. The provision of the conical socket also advantageously facilitates alignment and connection of an ocean energy capturing device with the base. The method for connecting the ocean energy capturing 30 device to the seabed, as described above, is also relatively simple compared to conventional techniques. While the invention has been described with reference to specific embodiments, it will be appreciated that it may also be embodied in many other forms. For example: WO 2007/019609 PCT/AU2006/001150 -12 " The base 12 can form the top of a suction caisson and be secured to the seabed 16 by a vacuum pressure; * The cable 46 can be drawn by a winch or crane instead of by a tug boat; and/or " The mooring 10 can be used to moor offshore wind turbines, subsea pipelines, or 5 other structures, either offshore or on land.

Claims

1. A mooring for connecting an ocean energy capturing device to a seabed, said mooring comprising: a base adapted for connection to the ocean energy capturing device, the base including a socket engageable by the ocean energy capturing device for connecting the ocean energy capturing device to the base, the socket being tapered and of non-circular cross-section, with a larger diameter end of the socket being at the end furthest from the base; and a plurality of anchor bolts, each having a first end and a second end, to be embedded in the seabed and connected to the base for attaching the base to the seabed.

2. A mooring according to claim 1, wherein the socket is adapted for engagement with a complimentary spigot on the ocean energy capturing device.

3 A mooring according to claim I or claim 2, wherein the socket is provided in a generally cylindrical boss located substantially centrally on the base.

4. A mooring according to claim 3, further comprising a plurality of circumferentially spaced buttress supports extending between a radially outer periphery of the boss and the base.

5. A mooring according to claim 3, further comprising a guide opening in a radially outer periphery of the boss.

6. A mooring according to any one of claims 1 to 5, further comprising an annular flange extending radially outwardly from an open end of the socket.

7. A mooring according to claim 6, wherein the annular flange includes apertures for receiving fasteners for connecting the ocean energy capturing device to the base.

8. A mooring according to any one of claims I to 7, further comprising a first pulley wheel connected to the base.

9. A mooring according to claim 8, wherein the first pulley wheel is located adjacent an end of the socket closest the base.

10. A mooring according to claim 5, further comprising a second pulley wheel located adjacent the guide opening,

11. A method of securing an ocean energy capturing device to a seabed, said method comprising the steps of: 14 providing a mooring comprising: a base adapted for stationary mounting to the seabed and for connection to the ocean energy capturing device; a tapered socket on the base, the socket being of non-circular cross-section; and a guide opening in the base, the guide opening adapted to receive a tensile transmission line therethrough for guiding the ocean energy capturing device toward the base for engagement therewith; securing the base relative to the seabed; connecting one end of the tensile transmission line to the ocean energy capturing device; passing the tensile transmission line through the guide opening; drawing the tensile transmission line through the guide opening to drag the ocean energy capturing device toward the base; and connecting the ocean energy capturing device to the base by engaging a tapered spigot on the ocean energy capturing device with the tapered socket on the base.

12. A method according to claim 11, wherein a larger diameter end of the socket is located at an end of the socket furthest from the base.

13. A method according to claim I 1 or claim 12, including the additional step of providing a first pulley wheel connected to the base.

14. A method according to claim 13, wherein the first pulley wheel is located adjacent an end of the socket closest the base.

15. A method according to claim 14, including the additional step of providing a second pulley wheel located adjacent the guide opening.

16. A method according to claim 15, including the additional step of passing the tensile transmission line around the first and second pulleys during said drawing.

17. A mooring for connecting an ocean energy capturing device to a seabed, said mooring substantially as hereinbefore described with reference to any one embodiment, as that embodiment is shown in the accompanying drawings.

18. A method of securing an ocean energy capturing device to a seabed, said method substantially as hereinbefore described with reference to any one embodiment, as that embodiment is shown in the accompanying drawings.