The present invention relates to a mooring system, and particularly, but not exclusively to a mooring system for use in anchoring a floating offshore wind turbine installation.
It is known to anchor floaters such as a semi-submersible floating wind turbine installation using a plurality of mooring lines each of which extends from a connection point on the floater to an anchor. Where there are a plurality of floaters, the floaters in the array may share anchors, so that a plurality of mooring lines are attached to each anchor, each mooring line being attached to any one anchor extending to a different floater in the array.
Publications which may be useful to understand the background of the present invention are WO 2022/031175, US 2013/0276687, and WO 2022/098288.
In an embodiment, the present invention provides a mooring system which includes a floater, a first anchor, a first mooring line, and a second mooring line. The first mooring line and the second mooring line are each connected to the first anchor and extend to the floater. The first mooring line is connected to the floater at a first connection point. The second mooring line is connected to the floater at a second connection point. The first connection point is spaced apart from the second connection point.
The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:
An embodiment of the present invention provides a mooring system comprising a floater, a first anchor, and first and second mooring lines, the first and second mooring lines being secured to the first anchor and extending to the floater, the first mooring line being secured to the floater at a first connection point, and the second mooring line being secured to the floater at a second connection point, the first connection point being spaced from the second connection point.
The system may comprise a second anchor and a third mooring line which is connected to the second anchor and extends from the second anchor to the floater, the third mooring line being connected to the floater at a third connection point which is spaced from the first and second connection points.
The system may comprise a third anchor and a fourth mooring line which is connected to the third anchor and extends from the third anchor to the floater, the fourth mooring line being connected to the floater at a fourth connection point which is at or adjacent the third connection point.
The fourth mooring line may alternatively be connected to the floater at a fourth connection point which is spaced from the first, second and third connection points.
The system may alternatively comprise a fourth mooring line which is connected to the second anchor and extends from the second anchor to the floater, the fourth mooring line being connected to the floater at a fourth connection point which is at or adjacent to either the first or second connection point.
The floater may be a first floater and the mooring system further comprise one or more additional floaters, and an additional anchor for each additional floater, each additional floater having two mooring lines which are secured to one of the additional anchors and to the respective floater at a first connection point and a second connection point, the first connection point being spaced from the second connection point, the system further comprising at least one additional mooring line via which each floater is connected to the other or one of the other floaters.
The floater may be a first floater and the mooring system further comprise two or more additional floaters, and an additional anchor for each additional floater, each additional floater having two mooring lines which are secured to one of the additional anchors and to the respective floater at a first connection point and a second connection point, the first connection point being spaced from the second connection point, the system further comprising one additional mooring line for each floater via which each floater is connected to two of the other floaters. The system may, for example, further comprise a second and third floater, and a second and third anchor, the second and third floater each having two mooring lines which are secured to the second and third anchor respectively and to the respective floater at a first connection point and a second connection point, the first connection point being spaced from the second connection point, the system further comprising three additional mooring lines via which each floater is connected to each of the other floaters.
The floater may comprise a foundation structure. The foundation structure may have a plurality of corners, the first mooring point being provided at a first one of the corners, and the second mooring point being provided at a second one of the corners. Where the foundation structure is provided with more than three corners, the first and second mooring points may be provided at adjacent corners.
The foundation structure may comprise a platform formed from a plurality of buoyant elements joined by a plurality of generally rigid connectors, a buoyant element being provided at each corner of the foundation structure. The foundation structure may comprise, for example, three buoyant elements arranged in a triangular array. The base may alternatively comprise four buoyant elements arranged in a square or rectangular array. The base may further alternatively comprise more than four buoyant elements arranged in a polygon array, with a buoyant element being provided at each corner of the polygon.
The floater may further comprise a wind turbine supported on the foundation structure.
The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, “upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the present invention. The terms are used for the reader's convenience only and shall not be limiting.
In all the drawings, the mooring system 10 is illustrated schematically as if viewed from directly above when the floater is floating on a body of water.
The first and second connection points 20, 22 are advantageously arranged so that when the floater 12 is floating on a calm body of water, a line connecting the first and second connection points 20, 22 is generally horizontal. This line need not be exactly horizontal, but there should, however, be a significant horizontal separation between the first and second connection points 20, 22.
In the embodiment illustrated in A of
In an alternative embodiment illustrated in B of
The floater may equally be annular or circular, or a polygon in a plan view, with more than 4 sides. In the embodiment illustrated in C of
It will be appreciated that in the arrangements illustrated in A-D of
While
In the embodiment illustrated in
The first, second and third anchors 14, 24, 30 are generally evenly spaced around the floater 12, so if the mooring lines 16, 18, 26, 32 are all taut, a generally horizontal movement of the floater 12 in any direction is significantly restricted. It will be appreciated by a person of skill in the art that, in practice, the mooring lines 16, 18, 26, 32 will never be completely taut. In order to extend from the floater 12 at the water surface to the anchors 14, 24, 30 at the sea bed, the mooring lines 16, 18, 26, 32 can be very long and heavy, and therefore tend to follow an arcuate path from the floater 12 to the anchors 14, 24, 30, as is illustrated, for example, in FIG. 13 of US 2013/0276687. This is generally known to persons of skill in the art as a “catenary” mooring system. The weight of the mooring lines 16, 18, 26, 32 will, however, provide a force which resists the mooring lines 16, 18, 26, 32 from straightening any further, and thus horizontal movement of the floater 12 will, nonetheless, be substantially prevented or at least significantly restricted.
It should also be appreciated that while the first, second and third anchors 14, 24, may be generally evenly spaced around the floater 12, this need not be the case. Depending on the prevailing environmental loads (prevailing wind direction, tide, currents etc.), two of the anchors 14, 24, 30 may be closer to each other than they are to the other anchor.
The floater 12 may be provided in an array of floaters as illustrated in
In this embodiment, the different floaters 12 in the array share anchors. The first anchor 14 of one mooring system 10 is the second anchor 24a of another mooring system 10a and the third anchor 30b of yet another mooring system 10b. Similarly, the second anchor 24 of the mooring system 10 is the third anchor 30c of another mooring system 10c and the first anchor 14d of yet another mooring system 10d, and the third anchor 30 is the first anchor 14e of yet another mooring system 10e and the second anchor 24f of yet another mooring system 10f. As such, it will be appreciated that for all the mooring systems which are not at the edge of the array, four mooring lines are connected to each anchor 14, 24, 30.
The array is typically arranged so that the mooring systems 10, 10a, 10b, 10c, 10e and 10f are arranged so that the prevailing direction of the environmental loads (e.g., winds, waves, and/or current loads—as indicated by arrow A) is parallel to a line between the first anchor 14 and the floater 12 and directed to drive the floater 12 away from the first anchor 14.
As mentioned above, the same principle may be applied to the other types of floater illustrated in B-D of
A further alternative embodiment is illustrated in
In this embodiment, the system 10 also has a third anchor 30, and fifth and sixth mooring lines 34, 36 extend from the third anchor 30 to the floater 12. The fifth mooring line 34 is connected to the floater 12 at a fifth connection point 33 which is at or adjacent to the third connection point 28, while the sixth mooring line 36 is connected to the floater at a sixth connection point which is at or adjacent the first connection point 20.
The mooring system 10 may be provided in an array of mooring systems as illustrated in
As specified in relation to
Also as specified in relation to
A further alternative embodiment of mooring system 10′ is illustrated in
This embodiment of mooring system 10′ can include three of the mooring systems illustrated in A-D of
In the embodiment illustrated in
The mooring system 10′ further comprises one additional mooring line 37, 37′, 37″ for each floater 12, 12′, 12″, i.e., there are a total of three additional mooring lines 37, 37′, 37″. Each additional mooring line 37, 37″, 37″ is used to connect one of the floaters 12, 12′, 12″ to each one of the others. The additional mooring lines 37, 37′, 37″ are connected to a third connection point 28, 28′, 28″ on each of the floaters 12, 12′, 12″, the third connection point 28, 28′, 28″ being spaced from the first and second connection points 20, 22, 20′, 22′, 20″, 22″ on each floater 12, 12′, 12″.
In this embodiment, the additional mooring lines 37, 37′, 37″ are all substantially equal in length, and therefore the three floaters 12, 12′, 12″ are arranged at the points of an equilateral triangle. The additional mooring lines 37, 37′, 37″ could, however, have different lengths, depending on the desired relative positions of the anchors 12, 12′, 12″.
This mooring system 10′ could comprise auxiliary anchors and mooring lines, as illustrated in
Such auxiliary anchors 15a, 15b, 15c and auxiliary mooring lines 35a, 35b, 35c assist in maintaining the position of the floaters 12, 12′, 12″ in particularly harsh environments.
The auxiliary mooring lines 35a, 35b, 35c could equally be secured to a connection point at or adjacent to the third connection points 28, 28′, 28″ to which the additional mooring lines 37, 37′, 37″ are connected, as illustrated in
A further alternative embodiment of mooring system 10′″ is illustrated in
It will be appreciated that such mooring systems 10′, 10″, 10′″ could include more than three of the systems illustrated in A-D of
In the embodiment illustrated in
In the embodiment illustrated in
In this embodiment, two additional mooring lines are provided for each floater 12, 12′, 12″, 12′″, so that each floater 12, 12′, 12″, 12′″ is connected to one adjacent floater 12, 12′, 12″, 12′″ by one pair of additional mooring lines, and to another adjacent floater 12, 12′, 12″, 12′″ by another pair of additional mooring lines, one additional mooring line 37, 37′, 37″, 37′″ of each pair being secured to a connection point at a corner of the floater 12, 12′, 12″, 12′″ to which one of the anchor connected mooring lines 16, 18, 16′, 18′, 16″, 18″, 16′″, 18′″ is secured, and the other of the pair 39, 39′, 39″, 39′″ being secured to a connection point at a fourth corner of the floater 12, 12′, 12″, 12′″.
A plurality of the mooring systems 10′, 10″, 10′″, 10″″ illustrated in any of
In the embodiment illustrated in
By virtue of these arrangements, the number of anchors per floater, and therefore damage to the seabed, may be reduced. The use of suspended mooring lines between floaters may moreover facilitate a reduction in the total footprint of (i.e., area occupied by) the system.
In any of the embodiments described above, the floater 12 may comprise a foundation structure which has a plurality of corners, each of the connection points being provided at one of the corners.
The foundation structure may comprise a platform formed from a plurality of buoyant elements 12a joined by a plurality of generally rigid connecting elements 12b. The connecting elements 12b may, for example, comprise trusses, pontoons or other means for bracing. A buoyant element 12a is advantageously provided at each corner of the array, the first and second connection points 20, 22 being provided on different buoyant elements 12a.
Various possible arrangements of such foundation structures are illustrated in A-C of
The floater 12 may be a semi-submersible platform of the sort described in US 2013/0276687, which comprises a plurality of generally vertical buoyancy columns coupled together with a tubular truss system that includes horizontal and vertical bracing beams with a horizontal water-entrapment plate attached to the lowermost portion of some or all of the columns. While all of the columns may be substantially hollow buoyancy columns, this need not be the case. Some of the columns may, for example, be substantially hollow buoyancy columns, while the others are stabilizing columns. Where the foundation structure is provided with a mixture of buoyancy columns and stabilizing columns, the connection points 20, 22, 28 could be provided on buoyancy columns only, stabilizing columns only, or as a mixture of buoyancy columns and stabilized columns. It should be appreciated that the floater 12 could equally comprise a single, continuous buoyant element,
The floater 12 may further comprise a wind turbine 50 supported on the foundation structure 48, as illustrated in
More than one wind turbine could be mounted on the foundation structure. Another energy generating apparatus, such as a solar panel, could also be mounted on the foundation structure in addition to a wind turbine.
The floater 12 could equally be a fish farm, or an array of floating solar panels.
The or each anchor 14, 24, 30 may be a dead weight anchor, a driven pile, a drag anchor, a suction pile, a torpedo pile, a vertical load anchor, or any other suitable form of anchor device.
The mooring lines 16, 18, 26, 32, 34, 36 may be chains, ropes or cables, and may be made from metal or polymers such as polyester, nylon, or high modulus polyethylene. The mooring lines 16, 18, 26, 32, 34, 36 need not be all be made from the same material or be of the same construction; some may be chains, others ropes etc.
In the embodiments of mooring system 10′ illustrated in
Each mooring line may be connected to the floater 12 using a connector such as a fairlead or bi-axial joint, as illustrated in
Where a mooring line is connected to the floater 12 at a connection point which is at or adjacent to the connection point associated with a different mooring line, while both mooring lines could be connected to the same connector, typically this will not be the case, and each mooring line will be provided with its own connector. The connectors may in this case be mounted side-by-side on the floater 12 as illustrated in
By virtue of connecting two separate mooring lines (each of which extend from two different and horizontally spaced connection points on the floater all the way to the anchor) to the same anchor, the number of anchors used to restrain the floater 12 may be reduced, thus reducing the cost, both in terms of equipment and installation, and environmental impact on the sea floor of the mooring system 10.
In fact, computer simulations carried out reveal that when compared with the mooring system 10′ illustrated in
The invention is not limited by the embodiments described above; reference should be had to the appended claims.
This application is a continuation-in-part of application Ser. No. 17/880,678, filed on Aug. 4, 2022.
Number | Date | Country | |
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Parent | 17880678 | Aug 2022 | US |
Child | 18073605 | US |