Floating structures and mooring systems for offshore wind turbines
The tensioned mooring system with high-strength materials and aligned anchors and tendons addresses the cost and stability issues of conventional mooring systems, enhancing offshore wind turbine stability and performance.
Patent Information
- Application Number
- JP2025533624
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-22
- Filing Date
- 2023-12-15
- Publication Date
- 2025-12-11
AI Technical Summary
Existing offshore wind turbine installations face high costs and reduced performance due to structural motions from conventional mooring systems, particularly tension leg platforms, which are expensive and inefficient in maintaining stability.
A tensioned mooring system with aligned anchors and tendons, utilizing high-strength materials like HMPE, aramid, or carbon, is employed to stabilize the floating structure, comprising inner and perimeter tendons anchored on the seabed, ensuring stability and reducing costs through controlled tendon lengths.
The system provides enhanced stability against pitch and roll movements while minimizing costs by using a limited number of tendons, thus improving the performance and reducing installation expenses for offshore wind turbines.
Smart Images
Figure 2025540349000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a floating structure for an offshore wind turbine, more precisely to the subsea configuration and mooring of the floating structure on the seabed. [Background technology]
[0002] For the installation of offshore wind units, which comprise a turbine and a support connected to the seabed, it is well known to use a support structure, such as a jacket structure. Such a support structure rests on the seabed and is fixed to the ground using anchoring devices. The support structure extends above the sea surface to accommodate the wind turbine mast. Generally, this support structure is made in one piece, and the greater the depth, the higher the support structure must be. However, this solution is expensive.
[0003] Another solution for installing offshore wind units is to use floating structures moored to the seabed with mooring lines. This solution requires the use of floating technology. The structure of a floating offshore wind unit is as follows: a turbine corresponding to a rotor nacelle assembly (RNA) comprising blades, a hub and nacelle, and a tower; a floating substructure corresponding to the floating structure supporting the turbine; a station keeping system corresponding to the mooring lines and anchors, allowing the system to remain in place; It can be subdivided as follows:
[0004] The different types of floating substructures can be distributed in different families, for example barges, semi-submersibles, spars, tension leg platforms (TLP) or keels. The particularity of the tension leg platform system (TLP) is that the station keeping system (SKS) with mooring lines and anchors not only prevents structural drift but also ensures the stability of the floating structure by tensioning the mooring lines, also called tendons.
[0005] Tension leg platform systems are already known from offshore oil and gas operations, and tension leg platform systems used in oil and gas operations all include one or more tendon bundles that remain in a vertical position when static. With the tendons in a vertical configuration, the platform always remains in a vertical position (i.e., there is no pitch or roll movement).
[0006] However, even though tension leg platform systems reduce the motion of the floating structure compared to other mooring systems, motions can still be observed, and these motions reduce the performance and energy production of the offshore wind unit compared to moorings with supports connected to the seabed. Summary of the Invention [Problem to be solved by the invention]
[0007] One object of the present invention is to provide an improved, inexpensive mooring system for offshore wind turbines. [Means for solving the problem]
[0008] To this end, the invention relates to a floating structure comprising a tensioned mooring system, which is intended to moor and stabilize the floating structure to the seabed, preferably for an offshore wind turbine, The tension mooring system comprises: At least three joints arranged on the floating structure on an inner imaginary circle; at least three perimeter anchors arranged on the seabed, each having at least one perimeter tendon, each perimeter anchor connected to a respective joint point by at least one perimeter tendon, the perimeter tendons attached to the perimeter anchors on mooring points arranged on an outer imaginary circle that is coaxial with the inner imaginary circle and has a diameter larger than that of the inner imaginary circle; at least one inner anchor disposed on the seabed inside the inner imaginary circle, each joint point being attached to the at least one inner anchor by at least one inner tendon; Equipped with The peripheral tendons and / or the inner tendons are made of a material having a Young's modulus of 50 GPa or greater.
[0009] The peripheral anchors, their associated joint points, and the centers of the inner and outer virtual circles can be aligned on the same plane.
[0010] At least one medial anchor can be aligned in the same plane as its associated junction and the peripheral anchor connected to that junction.
[0011] The tension mooring system may include a single inner anchor located at the center of the inner and outer imaginary circles.
[0012] The anchoring points may have a regular distribution on the outer imaginary circle.
[0013] The junction points of the peripheral tendons and the inner tendons may have a regular distribution on the inner imaginary circle.
[0014] The anchor may be permanently sealed to the seabed.
[0015] The present invention also relates to a method for installing a floating structure, preferably for an offshore wind turbine, said method comprising the steps of: - placing at least three perimeter anchors on the seabed and attaching at least one perimeter tendon to each perimeter anchor of dedicated mooring points, so that the mooring points are arranged in an outer virtual circle; placing at least one inner anchor on the seabed and attaching at least three inner tendons to the at least one inner anchor, the inner anchor being arranged inside an inner virtual circle that is coaxial with the outer virtual circle and has a smaller diameter than the outer virtual circle; towing the floating structure at a location above the anchor location; connecting the perimeter tendon of each perimeter anchor to a dedicated joint point on the floating body structure and connecting the inner tendon of the at least one inner anchor to the joint point such that each joint point is attached to at least one inner anchor by an inner tendon, and tensioning the perimeter tendons and the inner tendon, the joint points being located on the inner virtual circle; Includes:
[0016] With respect to the installation method, the peripheral anchors, their associated joint points, and the centers of the inner and outer imaginary circles can be positioned to align on the same plane.
[0017] With respect to the method of placement, at least one medial anchor can be aligned in the same plane as its associated junction and the peripheral anchor connected to that junction.
[0018] Regarding the placement method, a single medial anchor can be placed at the center of the inner and outer virtual circles.
[0019] Regarding the installation method, the anchoring points on the perimeter anchors can be arranged in a regular distribution on an outer imaginary circle.
[0020] Regarding the installation method, the joints on the floating structure can be arranged in a regular distribution on the inner imaginary circle.
[0021] Regarding the installation method, the inner anchors and / or the perimeter anchors may be permanently sealed to the seabed. [Brief explanation of the drawings]
[0022] Further characteristics and advantages of the invention will become apparent from the following description, given by way of non-limiting example with reference to the accompanying drawings, in which:
[0023] [Figure 1] 1 is a side view of a schematic diagram of an offshore wind unit according to a first embodiment of the present invention; FIG. [Figure 2] FIG. 2 is a top view of the schematic diagram of the offshore wind unit of FIG. 1. [Figure 3] FIG. 10 is a top view of a schematic diagram of an offshore wind unit according to a second embodiment of the present invention.
[0024] In these figures, like elements have like reference numerals. The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference pertains to the same embodiment or that a feature applies only to a single embodiment. Individual features of different embodiments can be combined or interchanged to provide other embodiments. DETAILED DESCRIPTION OF THE INVENTION
[0025] 1 shows a floating structure 3, which can be designed to receive wind turbines 4 or other structures such as, for example, electrical substations for wind farms. The floating structure 3 comprises a tension mooring system 5 intended to moor and stabilize the floating structure 3 to the seabed Sb. The floating structure 3 preferably floats between two bodies of water below the sea surface Sl.
[0026] The tension mooring system 5 comprises at least three abutment points 31 arranged on the floating structure 3 on an inner imaginary circle A. As shown in Figure 2, the centre of this inner imaginary circle A is preferably the relative centre of the floating structure 3, where for example the mast of the turbine 4 is intended to be arranged.
[0027] The tension mooring system 5 also comprises at least three perimeter anchors 53 disposed on the seabed Sb, each having at least one perimeter tendon 52. Each perimeter anchor 53 is connected to an individual junction 31 having at least one perimeter tendon 52. The perimeter tendons 52 are attached to the perimeter anchors 53 on mooring points 51 disposed on an outer imaginary circle B, which is coaxial with the inner imaginary circle A and has a larger diameter than the inner imaginary circle A.
[0028] The tension mooring system 5 also includes at least one inner anchor 53′, which is located on the seabed Sb within the inner imaginary circle A. Each joint 31 of the floating structure 3 is attached to at least one inner anchor 53′ by at least one inner tendon 52′.
[0029] This mooring arrangement provides excellent stability for the floating structure 3, especially with regard to pitch or roll movements of the floating structure 3. Furthermore, by using a limited number of tendons 52, costs remain controlled and reduced.
[0030] This configuration reduces costs by limiting the length of the perimeter tendons 52.
[0031] As shown in FIG. 2, the peripheral anchors 53, their associated junctions 31, and the centers of the inner and outer imaginary circles A and B may be aligned on the same plane.
[0032] At least one medial anchor 53 ′ may also be aligned in the same plane as its associated junction 31 and the peripheral anchor 53 connected to this junction 31 .
[0033] 2 and 3, the tension mooring system 5 may comprise a single inner anchor 53′ located at the center of the inner imaginary circle A and the outer imaginary circle B. This particular embodiment makes it possible to limit the number of inner anchors 53′, which can limit the installation costs of the floating structure 3.
[0034] In order to constrain all degrees of freedom, the floating body structure 3, the peripheral tendons 52 and / or the inner tendons 52' have a Young's modulus of 50 GPa or more. The peripheral tendons 52 and / or the inner tendons 52' can then be made from a rigid material such as a highly elastic synthetic material such as HMPE (High Modulus Polyethylene), aramid, or carbon, alone or in combination with these materials.
[0035] The inner anchors 53' and / or the peripheral anchors 53' may be, for example, steel piles driven into the seabed, drilled and grouted piles driven into the seabed, or other means used in the area of offshore wind turbines, such as, for example, suction buckets. Preferably, the anchors 53, 53' are permanently sealed on the seabed Sb to ensure stability and mooring of the floating structure 3.
[0036] As mentioned above, the outer imaginary circle B has a larger diameter than the inner imaginary circle A. The peripheral tendons 52 are inclined outward (of the inner imaginary circle A) from a vertical line below the floating structure 3, preferably at an angle comprised between 30° and 60°, as they descend towards their mooring points 51. The inner tendons 52' are also inclined inward (of the inner imaginary circle A) from a vertical line below the floating structure 3 as they descend towards their inner anchors 53'. This configuration is particularly advantageous for further increasing the stability of the floating structure 3.
[0037] In order for the entire floating structure 3 to have excellent stability, the mooring points 51 of the peripheral tendons 52 and peripheral anchors 53 preferably have a regular distribution on the outer imaginary circle B, as shown in Figures 2 and 3 .
[0038] In addition, in order to ensure that the entire floating structure 3 has excellent stability, the joint points 31 of the peripheral tendons 52 and the inner tendons 52' preferably have a regular distribution on the inner imaginary circle A.
[0039] In the example of Figures 1 and 2, the floating structure 3 has a triangular shape and comprises only three joints 31 and, consequently, three perimeter anchors 53. It is also possible to imagine floating structures 3 having different shapes with more joints 31, more perimeter anchors 53 and more perimeter tendons 52. Figure 3, for example, shows a square floating structure 3 with four joints 31 and four perimeter anchors 53 at each corner of the square. Other shapes are also possible.
[0040] The present invention also relates to a method for installing a floating structure 3 designed to receive a wind turbine 4 .
[0041] The installation method includes a first step of placing at least three perimeter anchors 53 on the seabed Sb and attaching at least one perimeter tendon 52 to each anchor 53 on a dedicated mooring point 51. As described above, the mooring points 51 are located on the outer imaginary circle B. In this first step, at least one inner anchor 53' is also placed on the seabed Sb, and at least three inner tendons 52' are attached to the at least one inner anchor 53'. The inner anchor 53' is located within an inner imaginary circle A that is coaxial with the outer imaginary circle B and has a smaller diameter than the outer imaginary circle B.
[0042] As mentioned above, the centers of the outer imaginary circle B and the inner imaginary circle A are preferably the relative centers of the floating structure 3, where, for example, the masts of the turbines 4 are located. If the inner tendon 52' and / or the peripheral tendons 52' are, for example, metal, chain or metal cable, it is possible to rest them directly on the seabed Sb while waiting for the next step in the installation method. If the inner tendon 52' and / or the peripheral tendons 52' are, for example, synthetic cables, underwater buoys can be used to prevent the tendons 52, 52' from resting directly on the seabed Sb while waiting for the next step in the installation method.
[0043] During this first step of placing the anchors 53, 53' on the seabed Sb, the inner anchors 53' and / or the peripheral anchors 53 are advantageously permanently sealed on the seabed Sb.
[0044] Still during this first step, the peripheral anchors 53 may be arranged so that the anchoring points 51 on said peripheral anchors 53 are arranged in a regular distribution on the outer imaginary circle B.
[0045] A single inner anchor 53' can be placed at the center of the inner imaginary circle A and the outer imaginary circle B during this first step.
[0046] The installation method includes a second step of towing the floating structure 3 in place above the location of the anchors 53, 53'.
[0047] The joints 31 on the floating structure 3 are advantageously arranged in a regular distribution on the inner imaginary circle A.
[0048] The installation method includes a third step of connecting the perimeter tendons 52 of each perimeter anchor 53 to a dedicated joint 31 on the floating structure 3. During this third step, the inner tendon 52 of at least one inner anchor 53' is connected to the joint 31, so that also each joint 31 is attached to at least one inner anchor 53 by an inner tendon 52'. The joint 31 is positioned during this third step so that it lies on the inner imaginary circle A.
[0049] During this third step, the peripheral tendons 52 and the inner tendons 52' are also tensioned. Different methods for tensioning the tendons 52 are possible.
[0050] A first method may be to first connect the tendons 52, 52' to the floating body structure 3 at their joints 31 and then tension the tendons 52, 52' by known means.
[0051] A second method may be to submerge the floating structure 3, e.g., with ballast, to a first depth to connect the tendons 52, 52'. After the tendons 52, 52' are connected, the floating structure 3 is raised to a shallower depth, e.g., by emptying the ballast and tensioning the tendons 52, 52'.
[0052] During installation, the perimeter anchors 53, their associated junctions 31, and the centers of the inner A and outer B imaginary circles can be positioned to align on the same plane.
[0053] During placement, at least one medial anchor 53 ′ can be aligned in the same plane as its associated junction 31 and the peripheral anchor 53 connected to this junction 31 .
Claims
1. A floating structure (3) comprising a tension mooring system (5), said tension mooring system (5) intended to moor and stabilize said floating structure (3) to a seabed (Sb), preferably for an offshore wind turbine, The tension mooring system (5) comprises: at least three joints (31) arranged on said floating structure (3) on the inner imaginary circle (A); at least three perimeter anchors (53) arranged on the seabed (Sb), each with at least one perimeter tendon (52), each perimeter anchor (53) being connected to a respective joint point (31) by at least one perimeter tendon (52), the perimeter tendons being attached to the perimeter anchors (53) on mooring points (51) arranged on an outer imaginary circle (B) coaxial with the inner imaginary circle (A) and having a diameter larger than the inner imaginary circle (A); at least one inner anchor (53') arranged on the seabed (Sb) inside the inner imaginary circle (A), each joint point (31) being attached to the at least one inner anchor (53') by at least one inner tendon (52'); Equipped with The floating body structure (3), wherein the peripheral tendons (52) and / or the inner tendons (52') are made of a material having a Young's modulus of 50 GPa or more.
2. 2. The floating structure (3) according to claim 1, wherein the perimeter anchors (53), their associated joints (31), and the centres of the inner imaginary circle (A) and the outer imaginary circle (B) are aligned on the same plane.
3. 3. The floating structure (3) according to claim 1 or 2, wherein the at least one inner anchor (53') is aligned in the same plane as its associated junction (31) and the peripheral anchors (53) connected to this junction (31).
4. 4. The floating structure (3) according to claim 3, wherein the tension mooring system (5) comprises a single inner anchor (53') located at the center of the inner imaginary circle (A) and the outer imaginary circle (B).
5. The floating structure (3) according to any one of claims 1 to 4, wherein the mooring points (51) have a regular distribution on the outer imaginary circle (B).
6. The floating structure (3) according to any one of claims 1 to 5, wherein the joint points (31) of the peripheral tendons (52) and the inner tendons (52') have a regular distribution on the inner virtual circle (A).
7. The floating structure (3) according to any one of claims 1 to 6, wherein the anchor (53) is permanently sealed on the seabed (Sb).
8. A method for installing a floating structure (3) preferably for an offshore wind turbine, said installation method comprising the steps of: - arranging at least three perimeter anchors (53) on the seabed (Sb) and attaching at least one perimeter tendon (52) to each perimeter anchor (53) on dedicated mooring points (51) so that the mooring points (51) are arranged on an outer imaginary circle (B), and arranging at least one inner anchor (53') on the seabed (Sb) and attaching at least three inner tendons (52') to the at least one inner anchor (53'), the inner anchor being arranged inside an inner imaginary circle (A) that is coaxial with the outer imaginary circle (B) and has a smaller diameter than the outer imaginary circle (B); - towing the floating structure (3) at a location above the location of the anchors (53, 53'); - connecting the perimeter tendons (52) of each perimeter anchor (53) to dedicated joints (31) of the floating body structure (3) and the inner tendon (52') of the at least one inner anchor (53') to the joints (31) so that each joint (31) is attached to at least one inner anchor (53) by an inner tendon (52'), and tensioning the perimeter tendons (52) and the inner tendon (52'), the joints (31) being located on the inner imaginary circle (A); Including, installation methods.
9. 9. The installation method of claim 8, wherein the peripheral anchors (53), their associated joint points (31), and the centers of the inner and outer imaginary circles (A, B) are arranged to align on the same plane.
10. 10. The method of claim 8 or 9, wherein the at least one inner anchor (53') is aligned in the same plane as its associated junction (31) and the peripheral anchor (53) connected to this junction (31).
11. 11. The installation method of claim 10, wherein a single inner anchor (53') is placed at the center of the inner imaginary circle (A) and the outer imaginary circle (B).
12. The installation method according to any one of claims 8 to 11, wherein the anchoring points (51) on the peripheral anchors (53) are arranged in a regular distribution on the outer imaginary circle (B).
13. The installation method according to any one of claims 8 to 12, wherein the joints (31) on the floating structure (3) are arranged in a regular distribution on the inner imaginary circle (A).
14. The installation method according to any one of claims 8 to 13, wherein the inner anchors (53') and / or the peripheral anchors (53) are permanently sealed on the seabed (Sb).