Mooring system

Abstract

The invention relates to a mooring system comprising a floating platform (1) having a plurality of mooring lines (7) configured to fix or anchor the floating platform (1) to the seabed by means of a bottom section (71) of each mooring line (7) wherein each mooring line (7) also comprises a central section (72) joined to a counterweight (8), wherein the tilting arms (2) are joined to the main structure (4) of the floating platform (1) by means of an articulated joint (3), where each tilting arm (2) comprises an inner section (21) and an outer section (22), where a bottom section (71) and a central section (72) of each mooring line (7) are respectively engaged with an end of the outer section (22) and an end of the inner section (21) of each tilting arm (2).

Description

Technical Field

[0001] The object of the present invention is a mooring system particularly suitable for a floating platform as a foundation for a wind turbine located in the sea. The mooring system object of the present invention comprises a set of mooring cables or mooring chains (mooring lines) attached to piles buried in the seabed or to a counterweight located or placed on the seabed.

[0002] The mooring system object of the present invention has unique features making it ideal for use in floating platforms used as bases for offshore structure foundations, where it is important to avoid pitching or rolling, and also addresses certain disadvantages of other state of the art mooring systems for floating platforms.

[0003] The mooring system object of the present invention can be applied to any type of structure which is intended to float on the sea surface and which requires a plurality of mooring points on the seabed to secure the mooring cables or chains of the floating platform. Background Art

[0004] Floating platforms, in particular those intended for supporting wind turbines in the sea for generating electrical energy from the wind, require a mooring system to enable the floating platform to maintain its position and to contribute to its stability.

[0005] The platforms known as tension leg platforms (TLP) are currently the most advanced platforms. These platforms include three or more mooring lines (usually chains or cables connecting the platform to piles anchored to the seabed). The mooring lines of the TLP are designed to be arranged in a tensioned state, so as to engage the platform in the vertical direction to each of the piles anchored on the seabed. The TLP includes a set of floats, which are designed to generate excess buoyancy of the platform (taking into account the weight of the structure parked on the platform). This excess buoyancy ensures a high tension of the cables, which in turn ensures that they are always arranged in the vertical direction. This avoids pitch and roll movements of the platform and the structure parked on the platform.

[0006] Document EP 2743170 A1 describes a TLP similar to the one described in the previous paragraph.

[0007] One disadvantage of TLP is that the highly tensioned cables must keep them in the vertical direction, thus avoiding pitch and / or roll movements, and also avoiding movement of the platform in the vertical direction. Therefore, as the tide rises, the platform cannot move upwards (because the mooring lines have low or no extensibility), so the tension on the mooring lines increases significantly. This creates a high risk of breaking the mooring lines, making it necessary to have mooring lines with thick cross-sections, or to increase the number of mooring lines. Furthermore, when the tide is low, the TLP also drops and the mooring lines become very slack, increasing the risk of the platform moving vertically and laterally in an uncontrolled manner, and also increasing the risk of pitch and / or roll movements (due to the thrust of wind and / or waves on the platform and structures resting on the platform), which can cause the platform to capsize.

[0008] In order to avoid the above disadvantages, other types of floating platforms are known in which the mooring lines are connected to the counterweight by means of pulleys located on the platform. These types of platforms allow the platform to move vertically or laterally in response to tides, waves and wind, thus making it unnecessary to have a large number of mooring lines, or mooring lines with thick cross-sections.

[0009] Document ES2629867 A2 describes a platform similar to the one described in the previous paragraph.

[0010] One disadvantage of platforms equipped with counterweights and pulleys, such as described above, is that mooring lines, particularly when they are mooring cables, become worn over time due to bending, as the mooring lines bend and wear under tension as they pass over the pulleys. Over time, this can lead to the mooring lines breaking. Summary of the invention

[0011] In order to solve the above disadvantages, the present invention relates to a mooring system.

[0012] The mooring system object of the present invention comprises a floating platform (particularly suitable for supporting a wind turbine, but it may support any other type of structure) having a plurality of mooring lines (comprising chains or cables) configured to fix or anchor the floating platform to the seabed by means of a bottom section of each mooring line.

[0013] Each mooring line also comprises a central section which is joined to a counterweight (making it possible to stabilize the platform and ensure that the bottom section of the mooring line is always in tension, while allowing the stresses due to the movement of the floating platform to be absorbed, so that the bottom section of the mooring line does not need to be subject to the same degree of tension as occurs in a TLP type platform.

[0014] The bottom section of each mooring line can include one, two or three cables that join the platform to the seabed. Similarly, the center section of each mooring line can also include one, two or three cables.

[0015] In a novel manner, the mooring system object of the present invention comprises a plurality of tilting arms. Each tilting arm is joined to the main structure (or central structure) of the floating platform by means of an articulated joint, wherein said articulated joint is located corresponding to the middle point of the tilting arm.

[0016] Therefore, each tilting arm comprises an inner section and an outer section, wherein the inner section is located between the articulated joint and the interior of the floating platform (the interior of the platform or the main structure of the platform is understood to be an area closer to the center of the floating platform than where the articulated joint is located), and wherein the outer section is located between the articulated joint and the exterior of the main structure of the floating platform (the exterior of the platform or the main structure of the platform is understood to be an area closer to the center of the floating platform than where the articulated joint is located).

[0017] The bottom section and the center section of each mooring line are respectively engaged with the end of the outer section and the end of the inner section of each inclined arm.

[0018] The tilt arm is configured to rotate or tilt in a substantially vertical plane with its axis of rotation approximately horizontal. The vertical plane may be arranged radially (extending through the center of the platform) or oriented slightly laterally, giving the system a "spiral" appearance.

[0019] The system preferably has three, four or five radial mooring lines evenly distributed along its profile.

[0020] The above mooring system allows the central section of each mooring line together with the counterweight to absorb most of the stresses due to wind, waves and tidal currents, thereby allowing the floating platform to move.

[0021] At the same time, the tilting arm eliminates the need for pulleys between the bottom and center sections of each mooring line, thereby avoiding the problem of wear on the pulleys due to bending of the cables.

[0022] The above described system thus allows the use of cables with a much smaller cross section than the mooring cables used in TLPs and eliminates the risk of cable breakage due to wear from bending over the pulleys.

[0023] According to one aspect of the present invention, the inner section of each inclined arm may have a length shorter than the length of the outer section of the inclined arm. This configuration allows the floating platform to be installed in an area with larger waves.

[0024] Alternatively, according to another aspect of the invention, the outer section of each inclined arm may have a length that is shorter than the length of the inner section of the inclined arm. This configuration allows for the use of a lighter counterweight.

[0025] Likewise, according to one aspect of the invention, the end of the inner section of each tilting arm is located close to the center of the floating platform, meaning that the length of the inner section is slightly less than the distance from the center of its hinged connection to the floating platform. This configuration makes the floating platform less susceptible to capsizing from wind or waves, and has a smaller pitch angle under the same conditions.

[0026] The tilt arms may be supported on their respective articulated joints, or may be suspended from their respective articulated joints.

[0027] The inner section and the outer section of each tilting arm may be misaligned, for example, the inner section and the outer section of each tilting arm may form an angle between 10° and 20°. This makes it possible to improve the dynamic characteristics of the floating platform and avoid the outer section from contacting the sea surface when the platform moves.

[0028] According to a first embodiment of the mooring system, the floating platform has an annular geometry around the center of the floating platform. The geometry may be in the shape of a polygonal ring around the center of the floating platform, or it may be in the shape of a curved ring around the center of the floating platform.

[0029] According to this first embodiment, the floating platform may comprise a plurality of radii connected to alternating vertices on the periphery, with the central float supporting the wind turbine tower. Radially arranged articulated arms (when looking towards the wind turbine tower) rest on the remaining vertices of the profile.

[0030] Likewise, according to this first embodiment, the floating platform may be asymmetric, comprising several radii connected to alternating vertices on the periphery, with a central point (located in the vertical direction of the central counterweight). Radially arranged articulated arms (when looking towards the wind turbine tower) rest on the remaining vertices of the profile. The wind turbine tower may rest on one (or more) peripheral buoys, which are particularly oversized to support the weight of the tower and the wind turbine.

[0031] According to some embodiments of the mooring system, the floating platform has a star-shaped geometry with a plurality of protruding structural arms (or spikes) extending radially from a first end joined to the center of the floating platform to a second end protruding to the outside of the floating platform.

[0032] More specifically, according to a second embodiment of the mooring system, the floating platform has a star-shaped geometry with three protruding structural arms (or spikes), and according to a third embodiment of the mooring system, the floating platform has a star-shaped geometry with five protruding structural arms.

[0033] The second end of the protruding structural arm (or spike) can be rotated within an angle of 20° to 70° relative to the body of the protruding structural arm, thereby providing greater support to the tilting arm. Figure 2a , Figure 2b , Figure 3a and Figure 3b ), the inclined arms are not radial, but form the complementary angle (with the corresponding structural arm of the star structure) of the angle of the second end of rotation (meaning 20° to 70° respectively) of the protruding structural arm.

[0034] Of course, the floating platform may include common elements of other offshore wind platforms, such as: a resistant hull that provides buoyancy and supports the wind turbine tower, multiple support points for the articulated arm, access elements for accessing the platform from an auxiliary vessel, an electrical grounding connection system, auxiliary power equipment (cabin pumps, batteries, etc.).

[0035] The stability of the platform is provided by the mooring system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The following drawings are included as part of the explanation of at least one embodiment of the present invention.

[0037] Figure 1a : A schematic perspective view of a first embodiment of a mooring system according to the present invention is shown.

[0038] Figure 1b : Shows Figure 1a Schematic diagram of the details of the mooring system.

[0039] Figure 2a : A perspective schematic diagram of a second embodiment of the mooring system according to the present invention is shown.

[0040] Figure 2b : Shows Figure 2a Schematic diagram of the details of the mooring system.

[0041] Figure 3a : shows a perspective schematic diagram of a third embodiment of the mooring system according to the present invention.

[0042] Figure 3b : Shows Figure 3a Schematic diagram of the details of the mooring system.

[0043] Figure 4a : A schematic diagram showing the most common configuration of tilting arms, wherein two tilting arms are seen to be located in symmetrical positions relative to a plane passing through the center of the floating platform structure.

[0044] Figure 4b : shows a schematic diagram of a construction in which the inner section of the tilting arm is shorter than the outer section, wherein the two tilting arms are seen to be located in symmetrical positions relative to a plane passing through the center of the floating platform structure.

[0045] Figure 4c: shows a schematic diagram of a construction in which the outer section of the tilting arm is shorter than the inner section, wherein the two tilting arms are seen to be located in symmetrical positions relative to a plane passing through the center of the floating platform structure.

[0046] Figure 4d : shows a schematic diagram of a construction in which the inner section and the outer section of the tilting arm are not aligned, wherein the two tilting arms are seen to be in symmetrical positions relative to a plane passing through the center of the floating platform structure.

[0047] Figure 4e : shows a schematic diagram of a construction in which tilting arms are suspended from respective articulated joints at which they are attached to a floating platform structure, wherein two tilting arms are seen to be in symmetrical positions relative to a plane passing through the centre of the floating platform structure.

[0048] Figure 4f : shows a schematic diagram of a construction in which the inner section of the tilting arm extends almost to the center of the floating platform structure, wherein relative to a plane passing through the center of the floating platform structure, it can be seen that the two tilting arms are located in symmetrical positions.

[0049] Figure 5a : Schematic diagram showing the behavior of the tilting arm of a floating platform during an upward vertical movement due to a high tide or swell.

[0050] Figure 5b : Schematic diagram showing the behavior of the tilting arm of a floating platform during downward vertical movement due to low tide or waves.

[0051] Figure 5c : Schematic diagram showing the behavior of the tilting arm of a floating platform during horizontal movement due to swell or tidal current or horizontal thrust of wind. DETAILED DESCRIPTION

[0052] As mentioned above, the present invention relates to a mooring system comprising a floating platform 1 .

[0053] The floating platform 1 comprises a plurality of tilting arms 2 .

[0054] Each tilting arm 2 comprises an articulated joint 3 attached to a point of the main structure 4 of the floating platform 1 .

[0055] Each tilting arm 2 includes an inner section 21 and an outer section 22. The inner section 21 of each tilting arm 2 is arranged closer to the center 5 of the floating platform 1 than the outer section 22 of each tilting arm 2. The inner section 21 and the outer section 22 of the tilting arm 2 are connected to each other at a point on the tilting arm 2 corresponding to the location of the articulated joint 3.

[0056] Figure 1a and Figure 1bA first embodiment of a floating platform 1 is shown, wherein the main structure 4 of the floating platform 1 comprises a closed or annular geometry defining a closed loop around a center 5 of the floating platform 1 (in this case having an approximately triangular geometry, but it may have a polygonal geometry (with any number of sides), or a circular or other closed curved geometry).

[0057] exist Figure 1a and Figure 1b In FIG. 4 , it can be seen that the articulated joint 3 of the main structure 4 to which the tilting arm 2 is attached is located at the vertex of the polygonal ring (in this case a triangle). However, the articulated joint 3 may be located at another point of the main structure 4, for example in the middle of one side of the polygonal ring.

[0058] According to other embodiments (see, for example, the second and third embodiments described below), the main structure 4 may include a star-shaped geometric structure having a specific number of spikes or protruding structural arms 6, wherein each spike or protruding structural arm 6 includes a first end 61 engaged with the center 5 of the floating platform 1, and a second end 62, wherein the articulated joint 3 is located and attached to the tilting arm 2.

[0059] exist Figure 2a and Figure 2b In FIG. 4 , a second embodiment of a floating platform 1 is shown, wherein the main structure 4 of the floating platform 1 comprises a star-shaped geometry with three spikes or three protruding structural arms 6 .

[0060] exist Figure 3a and Figure 3b In FIG. 4 , a second embodiment of a floating platform 1 is shown, wherein the main structure 4 of the floating platform 1 comprises a star-shaped geometry with five spikes or five protruding structural arms 6 .

[0061] Each inclined arm 2 forms part of a mooring line 7 of the floating platform 1 .

[0062] Each mooring line 7 comprises a bottom section 71 and a central section 72 joined together by the inclined arm 2. The bottom section 71 and the central section 72 may comprise a mooring chain or cable.

[0063] The bottom section 71 of the mooring line 7 is connected to a bottom weight 73 (also called a "dead weight") or an anchor or foundation pile buried in the seabed, and is connected to the end of the outer section 22 of the tilting arm 2. The central section 72 of the mooring line 7 is connected to the central weight 8 of the floating platform 1, and is connected to the end of the inner section 21 of the tilting arm 2.

[0064] Figure 4aA side view of a floating platform 1 of a general configuration is schematically shown. Two symmetrical mooring lines 7 are present relative to a symmetry plane passing through the center 5 of the floating platform 1. This symmetrical configuration may occur, for example, in a floating platform 1 having an even number of mooring lines 7 and / or in a floating platform 1 having a main structure 4 having a symmetrical geometry relative to a plane passing through the center 5 of the floating platform 1 (such as a geometry in the form of an equilateral triangle or an isosceles triangle).

[0065] Figure 4a , Figure 4b , Figure 4c , Figure 4d and Figure 4f An embodiment is shown in which each tilting arm 2 rests on its respective articulated joint 3. Figure 4e An embodiment is shown in which each tilting arm 2 is suspended from its respective articulated joint 3 .

[0066] Figure 4a A possible embodiment is shown in which the inner section 21 and the outer section 22 of each inclined arm 2 have the same length. Figure 4b An embodiment is shown in which the inner section 21 of each tilting arm 2 is shorter than the outer section 22, and Figure 4c An embodiment is shown in which the outer section 22 of each inclined arm 2 is shorter than the inner section 21 .

[0067] Figure 4f A possible embodiment is shown, in which the inner section 21 of each tilting arm 2 extends almost to the centre 5 of the floating platform 1 .

[0068] Figure 4d One possible embodiment is shown, in which the inner section 21 and the outer section 22 of each tilting arm 2 are not aligned (eg, forming an angle of 15° relative to each other).

[0069] Figure 5a and Figure 5b The behavior of the floating platform 1 and in particular the behavior of the mooring lines 7 when the tide or waves produce respectively a vertical rise or vertical fall (without horizontal movement) of the floating platform 1. They show the case where the tilting arms 2 rest on their respective articulated joints 3, wherein the inner section 21 and the outer section 22 of each tilting arm 2 are aligned and have the same length.

[0070] When the tide rises ( Figure 5a ), the floating platform 1 moves upward, and since the bottom section 71 and the central section 72 of the mooring line 7 are practically inextensible, the end of each outer section 22 of each tilting arm 2 remains essentially in its same initial position (minimum horizontal movement is observed in the figure). In other words, the tilting arm 2 rotates around the end of the outer section 22.

[0071] Figure 5a The initial position of the floating platform 1 is shown in dotted lines, and the final position of the floating platform 1 (after the tide has risen) is shown in solid lines.

[0072] Therefore, when the tide rises, the bottom section 71 of each mooring line 7 pulls the corresponding end of the outer section 22 of each inclined arm 2, thereby tilting the inclined arm 2 toward the outside of the floating platform 1, thereby pulling the central section 72 of the mooring line 7, thereby raising the counterweight 8.

[0073] The tension to which the bottom sections 71 are subjected is lower than they would have had to withstand in the case of a TLP, since part of said tension is counteracted by the tilting movement of the tilting arm 2 and the raising of the counterweight 8 .

[0074] When the tide goes out ( Figure 5b ), the floating platform 1 moves downward.

[0075] Figure 5b The initial position of the floating platform 1 is shown in dotted lines, and the final position of the floating platform 1 (after the tide has receded) is shown in solid lines.

[0076] If the structure is a TLP, the mooring lines 7 and the buoyancy of the floating platform 1 will have to be designed in such a way that the mooring lines 7 are over-tightened, so that when the tide recedes, the mooring lines will continue to tighten (to avoid uncontrolled movement of the floating platform 1).

[0077] However, in the case of the mooring system object of the present invention, there is no need in the design to over-tighten the mooring line 7, since at low tide the counterweight 8 descends further than the main structure 4 of the floating platform 1 and pulls on the inner section 21 of each inclined arm 2, thereby keeping the bottom section 71 of the mooring line 7 taut.

[0078] Thus, when the tide recedes, the end of each outer section 22 of each tilting arm 2 remains essentially in its same initial position (minimal horizontal movement can be seen in the figure). In other words, the tilting arm 2 rotates around the end of the outer section 22.

[0079] Therefore, at low tide, the central section 72 of each mooring line 7 pulls the corresponding end of the inner section 21 of each inclined arm 2, thereby causing the inclined arm 2 to tilt toward the inside of the floating platform 1 (towards the center 5), thereby pulling the bottom section 71 of the mooring line 7, thereby keeping the bottom section 71 taut and thus ensuring the stability of the floating platform 1.

[0080] Figure 5c The behavior of the floating platform 1 and in particular the behavior of the mooring lines 7 when waves, currents or wind cause the floating platform 1 to move horizontally are shown. They show the tilting arms 2 resting on their respective articulated joints 3, wherein the inner section 21 and the outer section 22 of each tilting arm 2 are aligned and have the same length.

[0081] Figure 5c The initial position of the floating platform 1 is shown in dotted lines, and the final position of the floating platform 1 (after having been moved horizontally) is shown in solid lines.

[0082] As can be seen, in case of horizontal movement of the floating platform 1 , the sloping arm 2 of the mooring line 7 located windward experiences a greater inclination than the sloping arm 2 of the mooring line 7 located leeward.

[0083] The counterweight 8 moves horizontally a distance that is slightly less than the distance that the center 5 of the floating platform 1 moves, and thus becomes offset relative to a plane of symmetry passing through the center 5 of the floating platform 1. Furthermore, despite the fact that the main structure 4 of the floating platform 1 does not experience any vertical movement, the counterweight 8 does experience an upward vertical movement towards the main structure 4 of the floating platform 1.

[0084] As already mentioned (and as Figure 4d As shown), there is an embodiment in which the inner section 21 and the outer section 22 of each inclined arm 2 form an angle with each other.

[0085] The angle of inclination between the inner and outer sections 21, 22 of the tilting arm 2 has the effect of moving these sections 21, 22 away from the water surface, thus making it easier for them to tilt when descending without coming into contact with the water surface.

[0086] If there is no such angle of inclination between the two sections 21, 22 of the inclined arm 2, and if there is no wind, the inclined arm 2 should initially be horizontal (so it can move the same distance up or down from the waves). However, the floating platform 1 often moves laterally due to the wind (it is desirable that there is always wind to generate energy in the wind turbines on the floating platform 1). When moving laterally, the outer sections 22 of each inclined arm 2 move downwards, but it is good that they can move the same distance up and down, which is why there are embodiments in which the inclined arm 2 is designed with these sections 21, 22 forming an angle with each other. This is particularly useful for the outer sections 22 of the inclined arm 2, because the inner section 21 always tends to move away from the water surface, but in any case the inner section 21 is thus kept approximately perpendicular to the central section 72 of the mooring line 7, so that a greater effectiveness of the inner section 21 is also achieved (by having a larger lever arm).

Claims

1. A mooring system comprising: A floating platform (1) having a plurality of mooring lines (7) configured to fix or anchor the floating platform (1) to the seabed by means of a bottom section (71) of each mooring line (7), wherein each mooring line (7) also comprises a central section (72) connected to a counterweight (8), characterized in that it comprises a plurality of inclined arms (2), wherein each inclined arm (2) is connected to a main structure (4) of the floating platform (1) by means of an articulated joint (3), wherein the articulated joint (3) corresponds to the bottom section (71) of each mooring line (7). The midpoint of the inclined arms (2) is positioned so that each inclined arm (2) comprises an inner section (21) and an outer section (22), wherein the inner section (21) is located between the articulated joint (3) and the interior of the floating platform (1) and wherein the outer section (22) is located between the articulated joint (3) and the exterior of the main structure (4) of the floating platform (1), wherein the bottom section (71) and the center section (72) of each mooring line (7) are respectively engaged with the end of the outer section (22) and the end of the inner section (21) of each inclined arm (2).

2. The mooring system according to claim 1, characterized in that: The inner section (21) of each inclined arm (2) has a length that is smaller than the length of the outer section (22) of the inclined arm (2).

3. The mooring system according to claim 1, characterized in that: The outer section (22) of each inclined arm (2) has a length that is smaller than the length of the inner section (21) of the inclined arm (2).

4. The mooring system according to claim 2 or 3, characterized in that: The end of the inner section (21) of each tilting arm (2) is located close to the center of the floating platform (1).

5. Mooring system according to any one of the preceding claims, characterized in that The tilting arms (2) are supported by their respective articulated joints (3).

6. The mooring system according to any one of claims 1 to 4, characterized in that: The tilting arms (2) are suspended from their respective articulated joints (3).

7. A mooring system according to any one of the preceding claims, characterised in that The inner section (21) and the outer section (22) of each tilting arm (2) are not aligned.

8. The mooring system according to claim 7, characterized in that: The inner section (21) of each inclined arm (2) forms an angle with the outer section (22) between 10° and 20°.

9. Mooring system according to any one of the preceding claims, characterized in that The floating platform (1) has a ring-shaped geometry that is closed around the center (5) of the floating platform (1).

10. The mooring system according to claim 9, characterized in that The floating platform (1) has a geometric structure in the form of a polygonal ring closed around the center (5) of the floating platform (1).

11. The mooring system according to claim 9, characterized in that: The floating platform (1) has a geometric structure in the form of a curved ring closed around the center (5) of the floating platform (1).

12. The mooring system according to any one of claims 1 to 8, characterized in that: The floating platform (1) has a star-shaped geometric structure with a plurality of protruding structural arms (6), which extend radially from a first end (61) connected to the center (5) of the floating platform (1) to a second end (62) protruding toward the outside of the floating platform (1).

13. The mooring system according to claim 12, characterized in that The floating platform (1) has a star-shaped geometry with three protruding structural arms (6) with their corresponding mooring lines.

14. The mooring system according to claim 12, characterized in that The floating platform (1) has a star-shaped geometry with five protruding structural arms (6) with their corresponding mooring lines.

15. A mooring system according to any one of claims 12 to 14, characterized in that The protruding structural arm (6) includes its second end (62), which is rotated at an angle of 20° to 70° relative to the body of the protruding structural arm (6), and wherein each inclined arm (2) is connected to the corresponding second end (62) of each protruding structural arm (6) by means of its corresponding hinged joint (3).

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