Mooring system

Abstract

The present 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 the bottom section (71) of each mooring line (7), each mooring line (7) also comprising a central section (72) coupled to a counterweight (8), the inclined arms (2) being joined to the main structure (4) of the floating platform (1) by means of articulated joints (3), each inclined arm (2) comprising an inner section (21) and an outer section (22), the bottom section (71) and the central section (72) of each mooring line (7) being joined to the end portion of the outer section (22) and the end portion of the inner section (21) of each inclined arm (2), respectively.

Description

Technical Field

[0001] Object of the Invention The object of the present invention is a mooring system particularly suitable for a floating platform that functions as a base for a wind turbine placed in the sea. The object of the mooring system of the present invention comprises a set of mooring cables or chains (mooring lines) attached to piles buried in the seabed or weights placed or installed on the seabed.

[0002] The object of the mooring system of the present invention has unique features that make it ideal for use in floating platforms that function as bases for offshore structures where it is important to avoid pitch or roll, and also solves certain drawbacks of other mooring systems for floating platforms in the state of the art.

[0003] The object of the mooring system of the present invention is intended to float on the sea surface and can be applied to any type of structure that requires having several mooring points on the seabed to hold the mooring cables or chains of the floating platform.

[0004] Background of the Invention and Technical Problems to be Solved Floating platforms, particularly those intended to support wind turbines that generate electrical energy from the wind at sea, require a mooring system to keep them in place and contribute to their stability.

[0005] In the state of the art, platforms known as tension leg platforms (TLP) are known. These platforms comprise three or more mooring lines (usually chains or cables connecting the platform to piles anchored to the seabed). The mooring lines of a TLP are designed to be installed under tension and join the platform at a vertical position to each of the piles anchored to the seabed. A TLP comprises a set of floats designed to produce an excess buoyancy of the platform (taking into account the weight of the structures placed on the platform). This excess buoyancy ensures a high tension in the cables, which ensures that the cables are always arranged in a vertical position. This prevents pitch and roll movements of the platform and the structures placed on the platform.

[0006] European Patent Application Publication No. 2743170 A1 describes a TLP similar to that described in the previous paragraph.

[0007] One drawback of a TLP is that the high cable tension required to keep the cables in a vertical position and thus avoid pitch and / or roll movements also prevents the platform from moving vertically. Thus, during rising tides, the platform cannot move upwards (since the mooring lines have little or no extensibility), and thus the tension in the mooring lines increases significantly. This creates a high risk of the mooring lines breaking, and it becomes necessary to have mooring lines with a thick cross-section or to increase the number of mooring lines. Furthermore, in the case of low tides, the TLP also descends, and the mooring lines can become very slack, increasing the risk of the platform moving both vertically and horizontally in an uncontrolled manner and potentially capsizing the platform (due to wind and / or wave thrust on the platform and the structures placed on it), as well as increasing the risk of pitch and / or roll movements.

[0008] To avoid the aforementioned drawbacks, other types of floating platforms are known in which the mooring lines are connected to a counterweight by means of pulleys arranged on the platform. These types of platforms allow for the vertical and lateral movement of the platform in response to tides, waves and wind, and thus do not require a large number of mooring lines or mooring lines with a thick cross-section.

[0009] The Spanish Patent Application Publication No. 2629867A2 describes a platform similar to that described in the previous paragraph.

[0010] One drawback of platforms equipped with a counterweight and pulleys as described above is that the mooring line is subject to bending and wear under tension as it passes through the pulley, and thus the mooring line wears over time due to bending (especially when it is a mooring cable). Over time, this can cause the mooring line to break.

[0011] Description of the Invention To solve the above-mentioned drawbacks, the present invention relates to a mooring system.

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

[0013] Each mooring line also comprises a central section joined to a counterweight (this stabilizes the platform and allows ensuring that there is always tension in the bottom section of the mooring line, while allowing the absorption of stress due to the movement of the floating platform, and thus eliminating the need for the bottom section of the mooring line to withstand the same level of tension as that generated in a TLP type platform).

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

[0015] In a novel way, the mooring system object of the present invention comprises a plurality of inclined arms. Each inclined arm is joined to the main structure (or central structure) of the floating platform by a joint, and the joint is arranged corresponding to the midpoint of the inclined arm.

[0016] Accordingly, each inclined arm comprises an inner section and an outer section. The inner section is arranged between the joint and the inside of the floating platform (understanding the inside of the platform, or the inside of the main structure of the floating platform, as the area arranged closer to the center of the floating platform than the point where the joint is arranged), and the outer section is arranged between the joint and the outside of the main structure of the floating platform (understanding the outside of the platform, or the outside of the main structure of the floating platform, as the area arranged closer to the center of the floating platform than the point where the joint is arranged).

[0017] The bottom section and the central section of each mooring line are respectively joined to the end of the outer section and the end of the inner section of each inclined arm.

[0018] The inclined arms are configured to rotate or tilt on a substantially vertical plane, and its axis of rotation is substantially horizontal. This vertical plane can be arranged radially (through the center of the platform), or can be oriented slightly laterally, giving the system a "spiral" appearance.

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

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

[0021] At the same time, the inclined arms eliminate the need for pulleys between the bottom section and the central section of each mooring line, thus avoiding the problem of wear due to bending of the cable on the pulley.

[0022] Therefore, the described system enables the use of cables with a cross-section much smaller than that of the mooring cables used in TLPs, and eliminates the risk of cable braking due to wear from bending on the pulley.

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

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

[0025] Similarly, according to one aspect of the present invention, the end portion of the inner section of each inclined arm is arranged near the center of the floating platform, which means that the length of the inner section is slightly smaller than the distance from its articulated connection to the center of the floating platform. This configuration makes the floating platform less susceptible to overturning by wind or waves, and results in a smaller pitch angle under the same conditions.

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

[0027] The inner and outer sections of each inclined arm can be displaced, for example, the inner and outer sections of each inclined arm can form an angle of 10° to 20°. This improves the dynamic characteristics of the floating platform and makes it possible to prevent 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 a closed annular geometry around the center of the floating platform. This geometry can be in the shape of a polygonal ring closed around the center of the floating platform, or it can be in the shape of a curved ring closed around the center of the floating platform.

[0029] According to this first embodiment, the floating platform can include several radii connecting the central float supporting the wind turbine tower to the surrounding alternating vertices. The articulated arms arranged radially (when looking at the wind turbine tower) are placed on the remaining vertices of the contour.

[0030] Similarly, according to this first embodiment, the floating platform can be asymmetric and include several radii connecting the central point (located on the vertical line of the central counterweight) to the surrounding alternating vertices. The articulated arms arranged radially (when looking at the wind turbine tower) are placed on the remaining vertices of the contour. The wind turbine tower can be placed on one (or more) of the particularly large-sized surrounding floats 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 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 outside 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), while 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 included between 20° and 70° with respect to the body of the protruding structural arm, thus providing greater support by the inclined arm. In this configuration (shown in Figures 2a, 2b, 3a and 3b), the inclined arm forms an angle complementary to the angle of the rotated second end of the protruding structural arm (meaning 70° - 20° respectively) with respect to the star's respective protruding structural arms, rather than being radial.

[0034] Of course, the floating platform can include other common elements of an offshore wind platform, such as a resistance hull that provides buoyancy and support for the wind turbine tower, several support points for the articulated arms, access elements for accessing the platform from an auxiliary boat, an electrical grounding connection system, auxiliary electrical equipment (bilge pumps, batteries, etc.).

[0035] The stability of the platform is provided by the mooring system described above. Brief Description of the Drawings The following figures are included as part of the description of at least one embodiment of the present invention.

Brief Description of the Drawings

[0036]

Figure 1a

Figure 1b

Figure 2a

Figure 2b

Figure 3a

Figure 3b

Figure 4a

Figure 4b

Figure 4c

Figure 4d

Figure 4e

Figure 4f

Figure 5a

Figure 5b

Figure 5c

Mode for Carrying Out the Invention

[0037] Detailed Description As described above, the present invention relates to a mooring system including a floating platform (1).

[0038] The floating platform (1) includes a plurality of tilt arms (2). Each tilt arm (2) includes a joint (3) attached to one point of the main structure (4) of the floating platform (1).

[0039] Each tilt arm (2) includes an inner section (21) and an outer section (22). The inner section (21) of each tilt arm (2) is disposed closer to the center (5) of the floating platform (1) than the outer section (22) of each tilt arm (2). The inner section (21) and the outer section (22) of the tilt arm (2) are connected to each other at a point on the tilt arm (2) arranged corresponding to the joint (3).

[0040] Figures 1a and 1b show a first embodiment of the floating platform (1), and the main structure (4) of the floating platform (1) has a closed or annular geometry that defines a closed ring (in this case, having a substantially triangular geometry, but may have a polygonal geometry with any number of sides, or a circular or other closed curve geometry) around the center (5) of the floating platform (1).

[0041] In Figures 1a and 1b, it can be seen that the joints (3) of the main structure (4) attached to the tilt arms (2) are located at the vertices of a polygonal ring (in this case, a triangle). However, the joints (3) can be arranged at another point of the main structure (4), for example, at the center of one side of the polygonal ring.

[0042] According to other embodiments (see, for example, the second and third embodiments described below), the main structure (4) can have a star geometry with a specific number of spikes or protruding structural arms (6), and each spike or protruding structural arm (6) has a first end (61) joined to the center (5) of the floating platform (1) and a second end (62) where the articulated joint (3) is attached to the inclined arm (2).

[0043] Figures 2a and 2b show a second embodiment of the floating platform (1), in which the main structure (4) of the floating platform (1) has a star geometry with three spikes or three protruding structural arms (6).

[0044] Figures 3a and 3b show a second embodiment of the floating platform (1), in which the main structure (4) of the floating platform (1) has a star geometry with five spikes or five protruding structural arms (6).

[0045] Each inclined arm (2) forms part of the mooring line (7) of the floating platform (1).

[0046] Each mooring line (7) comprises a bottom section (71) and a central section (72) joined to each other by the inclined arm (2). The bottom section (71) and the central section (72) can comprise a mooring chain or cable.

[0047] The bottom section (71) of the mooring line (7) is connected to a bottom weight (73) (also called a "deadweight") or an anchor or a pile buried in the seabed and to the terminal end of the outer section (22) of the inclined arm (2). The central section (72) of the mooring line (7) is connected to the central counterweight (8) of the floating platform (1) and to the terminal end of the inner section (21) of the inclined arm (2).

[0048] Figure 4a schematically shows a side view of a floating platform (1) of a general configuration. Two symmetric mooring lines (7) are shown with respect to a plane of symmetry passing through the center (5) of the floating platform (1). This symmetric configuration can occur, for example, in a floating platform (1) having an even number of mooring lines (7) and / or a floating platform (1) having a main structure (4) with a geometric shape (such as a geometric shape in the form of an equilateral or isosceles triangle) that is symmetric with respect to a plane passing through the center (5) of the floating platform (1).

[0049] Figures 4a, 4b, 4c, 4d and 4f show embodiments in which each tilt arm (2) is placed on its respective articulation joint (3). In contrast, Figure 4e shows an embodiment in which each tilt arm (2) is suspended from its respective articulation joint (3).

[0050] Figure 4a shows a possible embodiment in which the inner section (21) and the outer section (22) of each tilt arm (3) have the same length. In contrast, Figure 4b shows an embodiment in which the inner section (21) of each tilt arm (2) is shorter than the outer section (22), and Figure 4c shows an embodiment in which the outer section (22) of each tilt arm (2) is shorter than the inner section (21).

[0051] Figure 4f shows a possible embodiment in which the inner section (21) of each tilt arm (2) extends to approximately the center (5) of the floating platform (1).

[0052] Figure 4d shows a possible embodiment in which the inner section (21) and the outer section (22) of each tilt arm (2) are offset (for example, forming an angle of 15° with respect to each other).

[0053] Figures 5a and 5b show the behavior of the floating platform (1), in particular the behavior of the mooring line (7) when the tide or a wave causes the floating platform (1) to move vertically upwards or downwards (without horizontal movement). They show the case of the tilting arms (2) placed on their respective articulated joints (3), with the inner section (21) and the outer section (22) of each tilting arm (2) being aligned and having the same length.

[0054] When the tide rises (Figure 5a), the floating platform (1) moves upwards. Considering that the bottom section (71) and the central section (72) of the mooring line (7) are substantially inextensible, the end of each outer section (22) of each tilting arm (2) remains essentially in its same initial position (in the figure, a minimal horizontal movement is observed). In other words, the tilting arm (2) rotates around the end of the outer section (22).

[0055] Figure 5a shows the initial position of the floating platform (1) with a dashed line and the final position (after the tide has risen) of the floating platform (1) with a solid line.

[0056] Therefore, when the tide rises, the bottom section (71) of each mooring line (7) pulls the end of each outer section (22) of each tilting arm (2), tilting the tilting arm (2) towards the outside of the floating platform (1), thus pulling the central section (72) of the mooring line (7) and thereby raising the counterweight (8).

[0057] Since part of the tension is cancelled out by the tilting movement of the tilting arm (2) and the raising of the counterweight (8), the tension borne by the bottom section (71) is less than the tension that would have to be borne in the case of a TLP.

[0058] When the tide ebbs (Figure 5b), the floating platform (1) moves downwards. Figure 5b shows the initial position of the floating platform (1) with a dashed line and the final position of the floating platform (1) (after the tide has receded) with a solid line.

[0059] When the structure is a TLP, the design of the mooring line (7) and the buoyancy of the floating platform (1) must be such that the mooring line (7) is not tightened too much when the tide ebbs (to avoid uncontrolled movement of the floating platform (1)).

[0060] However, in the case of the mooring system object of the present invention, it is not necessary to tighten the mooring line (7) too much in the design, because at low tide the counterweight (8) descends below the main structure (4) of the floating platform (1), pulls on the inner section (21) of each inclined arm (2), and firmly holds the bottom section (71) of the mooring line (7).

[0061] Therefore, when the tide ebbs, the end of each outer section (22) of each inclined arm (2) also remains essentially in the same initial position (a minimum horizontal movement is seen in the figure). In other words, the inclined arm (2) rotates around the end of the outer section (22).

[0062] Therefore, at low tide, the central section (72) of each mooring line (7) pulls on the end of each inner section (21) of each inclined arm (2), inclines the inclined arm (2) towards the inside of the floating platform (1) (towards the center (5)), thus pulling on the bottom section (71) of the mooring line (7), thereby firmly holding the bottom section (71) and thus ensuring the stability of the floating platform (1).

[0063] Figure 5c shows the behavior of the floating platform (1), particularly the behavior of the mooring line (7), when waves, currents or wind move the floating platform (1) horizontally. It shows the case of the tilt arms (2) mounted on their respective articulated joints (3), with the inner section (21) and the outer section (22) of each tilt arm (2) being aligned and having the same length.

[0064] Figure 5c shows the initial position of the floating platform (1) in dashed lines and the final position (after horizontal movement) of the floating platform (1) in solid lines.

[0065] As can be seen, in the case of horizontal movement of the floating platform (1), the tilt arms (2) of the mooring line (7) located upwind receive a greater tilt than the tilt received by the tilt arms (2) of the mooring line (7) located downwind.

[0066] The counterweight (8) moves horizontally by a distance slightly shorter than the distance by which the center (5) of the floating platform (1) moves and is thus offset with respect to the symmetry plane 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 undergo any vertical movement, the counterweight (8) undergoes an upward vertical movement towards the main structure (4) of the floating platform (1).

[0067] As already mentioned (and as shown in Figure 4d), there are embodiments in which the inner section (21) and the outer section (22) of each tilt arm (2) form an angle with each other.

[0068] This tilt angle between the inner section (21) and the outer section (22) of the tilt arm (2) has the effect of moving the said sections (21, 22) away from the water surface and thus makes it easier to tilt without coming into contact with the water during descent.

[0069] In the case where there is no such inclination angle between both sections (21, 22) of the inclined arm (2), and in the absence of wind, the inclined arm (2) must initially be horizontal (so that it can rise or fall at the same distance from the waves). However, the floating platform (1) is usually laterally displaced by the wind (it is desirable that there is always wind for generating energy in the wind turbine arranged on the floating platform (1)). When moving laterally, the outer sections (22) of each inclined arm (1) move downward, but it is preferable that they can move up and down the same distance, which is the reason for the embodiment in which the inclined arm (2) is designed such that its sections (21, 22) form an angle with each other. This is particularly useful for the outer section (22) of the inclined arm (2) because the inner section (21) always tends to move away from the water surface. In any case, the inner section (21) remains substantially perpendicular to the central section (72) of the mooring line (7), and as a result, a greater effectiveness of the inner section (21) is also achieved (by having a greater lever arm).

Claims

1. A mooring system comprising a floating platform (1), having a plurality of mooring lines (7) configured such that the floating platform (1) is fixed or anchored to the seabed by a bottom section (71) of each mooring line (7), and each mooring line (7) also comprises a central section (72) joined to a counterweight (8), wherein the mooring system comprises a plurality of inclined arms (2), each inclined arm (2) being joined to the main structure (4) of the floating platform (1) by an articulated joint (3), the articulated joint (3) being positioned corresponding to the midpoint of the inclined arm (2). A mooring system characterized in that each inclined arm (2) comprises an inner section (21) and an outer section (22), the inner section (21) being positioned between the articulated joint (3) and the interior of the floating platform (1), the outer section (22) being positioned between the articulated joint (3) and the exterior of the main structure (4) of the floating platform (1), and the bottom section (71) and the central section (72) of each mooring line (7) being joined to the end of the outer section (22) and the end of the inner section (21) of each inclined arm (2), respectively.

2. The mooring system according to claim 1, characterized in that the inner section (21) of each inclined arm (2) has a length less 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 less 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 portions of the inner sections (21) of each inclined arm (2) are positioned near the center (5) of the floating platform (1).

5. The mooring system according to any one of claims 1 to 3, characterized in that the inclined arm (2) is supported by each of the articulated joints (3) thereof.

6. The mooring system according to any one of claims 1 to 3, characterized in that the inclined arm (2) is suspended from each of the joint connections (3) thereof.

7. The mooring system according to any one of claims 1 to 3, characterized in that the inner section (21) and the outer section (22) of each inclined arm (2) are misaligned.

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

9. The mooring system according to any one of claims 1 to 3, characterized in that the floating platform (1) has a closed annular geometric shape 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 shape in the form of a closed polygonal ring 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 shape in the form of a closed curved ring around the center (5) of the floating platform (1).

12. The mooring system according to any one of claims 1 to 3, characterized in that the floating platform (1) has a star-shaped geometric form having a plurality of protruding structural arms (6) extending radially from a first end (61) joined to the center (5) of the floating platform (1) to a second end (62) protruding to the outside of the floating platform.

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

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

15. The mooring system according to claim 12, characterized in that the protruding structure arm (6) has a second end (62) which is rotated by an angle between 20° and 70° with respect to the body of the protruding structure arm (6), and each inclined arm (2) is joined to each of the second ends (62) of each protruding structure arm (6) by its respective articulated joint (3).

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