Apparatus for supporting an offshore wind turbine tower

Abstract

The present invention relates to an apparatus for supporting an offshore wind turbine tower. The apparatus includes a first body (1), a support (3) attached to the first body (1), a second body (2), and a plurality of legs (4) attached to the second body (2). The support (3) has a cylindrical interior and is configured to provide support and connection to a wind turbine tower (10). The first body (1) includes a central section (5) connected to the support (3) and a plurality of hollow arms (6) connected to the central section (5). Each hollow arm (6) includes a through-hole (7) configured to allow a leg (4) to pass through the through-hole. The first body (1) has a volume and weight configured to provide buoyancy of at least 20% of the weight of the entire apparatus when empty, and the weight of the first body (1) is less than 8% of the weight of the entire apparatus. The legs (4) and / or the first body (1) have a locking system configured to lock the relative position between the legs and the first body.

Description

[Technical Field]

[0001] The present invention is in the technical field of structures supporting offshore wind turbines. [Background technology]

[0002] When installing an offshore wind turbine tower, it is necessary to provide an appropriate system for laying and stabilizing the foundation.

[0003] There are many different methods and devices for this purpose, all of which can be classified into four types based on how the structure achieves stability: semi-submersible platforms, TLPs, SPARs or barges.

[0004] Semi-submersible platforms are platforms that have achieved stability as a result of their high floating inertia, which provides a high metacentric radius to compensate for their high center of gravity. They are characterized by good offshore performance, but based on the evolution of wind turbine power (which is getting higher and higher), their dimensions are becoming larger, making it difficult to find construction docks and ports with the required dimensions and draft.

[0005] Examples of these semi-submersible platforms are described in WO 2018 / 189084 and WO 2018 / 150064. WO 2018 / 189084 discloses a semi-submersible floating body device, including a means for forming an additional buoyancy and ballast caisson attached below the remainder of the floating body for movement between a retracted handling position relative to the floating body and a deployed use position spaced below the floating body. WO 2018 / 150064 discloses a floating structure for large offshore wind turbines, consisting of a lower triangular caisson made of reinforced concrete and an upper triangular caisson made of metal on which the wind turbine shaft is supported, both caissons connected by three liftable columns located at their corners. This floating structure has a semi-submersible component due to the presence of three floats at waterline level that increase its righting moment.

[0006] TLP (Tension Leg Platform) is a platform whose main structure has a hydrostatic thrust greater than its weight, and is stretched by an anchoring system to achieve stability. This type of platform performs exceptionally well offshore, but has the disadvantage of being difficult to install due to the large tendons.

[0007] The SPAR platform has a centre of gravity lower than the centre of the hull, making it a stable platform. It behaves exceptionally well offshore, as it is transparent to wave action as a result of its low sea level and high natural period.

[0008] Barges, like semi-submersible platforms, behave poorly offshore, but gain stability through high buoyancy.

[0009] The invention described below is based on the concept of SPAR type structures, as many of these platforms do not have the stability required for transportation, in addition to the installation problems inherent in this type of platform, and require additional means for transportation and installation (barges or cranes), which is not the case with the present invention.

[0010] The present invention provides an alternative solution to known solutions. Summary of the Invention

[0011] As mentioned above, the present invention provides an alternative solution for laying foundations for offshore towers by means of an apparatus for laying foundations as claimed in claim 1. Preferred embodiments of the invention are defined in the dependent claims.

[0012] Unless otherwise defined, all terms (including technical and scientific terms) used herein should be interpreted in the same manner as commonly used in the art. Furthermore, it will be understood that commonly used terms should be interpreted in the same manner as commonly used in the art, and not in an idealized or overly formalized sense, unless expressly defined herein.

[0013] As used herein, the term "comprises" and its derivatives should not be construed in an exclusive sense, i.e., these terms should not be interpreted to exclude the possibility that what is described and defined may include other elements, steps, etc.

[0014] In a first aspect, the present invention relates to an apparatus for supporting a wind turbine tower, the apparatus comprising: a first body, a support attached to the first body, a second body, and a plurality of legs attached to the second body, the support having a cylindrical interior defining a tower axis and configured to provide support and connection for the wind turbine tower; the first body includes a central portion connected to the support and a plurality of hollow arms connected to the central portion, each of the hollow arms extending radially from the central portion and including a first surface perpendicular to the tower axis and a second surface parallel to the first surface, the first surface of the hollow arm being included in a first reference plane and the second surface of the hollow arm being included in a second reference plane, the first reference plane being farther from the second body than the second reference plane; each of the hollow arms includes a through-hole extending from the first surface to the second surface, the through-hole configured to allow a leg to pass therethrough; the first body has a volume and weight configured to provide a buoyancy when empty that is at least 20% of the weight of the entire device, and the weight of the first body is less than 8% of the weight of the entire device; the first body having a first ballast management element that selectively allows water to enter and exit the first body; the second body has a first surface and a second surface, both of which are parallel to the first reference surface and the second reference surface, and the first surface is closer to the first body than the second surface; the second body having a ballast management element that selectively allows water to enter and exit the second body; The leg and / or the first body may have a locking system configured to lock the relative position between the leg and the first body.

[0015] The first body is hollow, providing a high buoyancy-to-weight ratio. In fact, it contributes at least 20% of the buoyancy of the entire device, but weighs less than 8% of the total device weight.

[0016] Furthermore, the fact that the second body is much heavier than the first body and that this second body is submerged several meters below the first body contributes to the high stability of the device by providing a stable position for the offshore wind turbine tower without the need for additional elements at the surface to provide buoyancy and inertia. The device according to the present invention is designed to be completely submerged during operation so that the support is the only element outside the water surface.

[0017] The ballast management elements on both the first and second bodies allow for good personalization of the final position and hydrostatic balance of the device, and allow for easy disassembly of the device in case of maintenance work or final dismantling.

[0018] In certain embodiments, the legs have a length greater than or equal to the sum of the distance between the first and second reference surfaces and 55% of the distance between the first and second reference surfaces and the second surface of the second body, such that the distance between the first and second bodies is large enough to positively contribute to the stability of the assembly.

[0019] In certain embodiments, the through-holes include a plurality of rollers to ensure smooth sliding of the legs within the through-holes.

[0020] The legs travel several meters to allow the second body to reach its final position below the surface of the sea, and these rollers therefore prevent the legs from being damaged when this movement takes place.

[0021] In certain embodiments, the central portion is hollow and has a major cross section with a larger area than a cross section of any of the hollow arms, the major cross section including the tower axis, the cross section of the hollow arm being measured according to a plane perpendicular to the tower axis and perpendicular to a first face of the hollow arm.

[0022] This creates a stable floating pattern, the central part of which accommodates auxiliary elements and support mechanisms (cranes, maintenance access, lights, etc.).

[0023] The corresponding extension axis, in the case of an arm, means an axis that starts at the midsection and extends along the arm. In the case of a midsection, any plane that cuts the midsection along the vertical central axis can be used.

[0024] In certain embodiments, each of the legs includes a stopper configured to cooperate with each of the through holes to prevent the leg from exiting the first body.

[0025] The stop provides an advantageous way to define the final position of the second body relative to the first body.

[0026] In certain embodiments, the leg and / or the first body comprises a locking system configured to lock the relative position between the leg and the first body.

[0027] The locking system is configured to prevent the relative position between the first body and the second body from being changed during operation of the device.

[0028] In certain embodiments, the locking system includes a hydraulic cylinder.

[0029] These hydraulic cylinders provide high force to ensure precise locking of these two elements.

[0030] In a particular embodiment, said second body has a chamfered hollow polygonal shape, preferably a chamfered hollow triangular shape.

[0031] This construction offers an optimum ratio between weight, volume and stability.

[0032] In a particular embodiment, each of the chamfered vertices of the triangle receives one of the legs.

[0033] Due to the fact that the legs are located at an outer distance from the center of the first part, the device operates stably.

[0034] In certain embodiments, the support comprises a plurality of radially arranged planar projections, the axial dimension of the support being greater than the radial dimension.

[0035] The central element usually has a cylindrical shape, whereby the vertical axis is defined by the axis of the cylinder, and the projections extend radially from said axis so that they are higher than they are larger, allowing stabilization of the system in the yaw direction.

[0036] In certain embodiments, the first body includes a planar plate extending from a base of the first body proximate the second body.

[0037] These planar plates allow for fore-aft instability to be controlled, and the increased mass and damping increases the natural period of the device for fore-aft vibrations, increasing the overall stability of the device.

[0038] In certain embodiments, the apparatus further comprises a tether attached to said first body.

[0039] In certain embodiments, the legs have a cylindrical shape, but in other situations they can have a polygonal cross section, for example a triangle, which is advantageous when there is no means available to bend the plate forming the legs.

[0040] In certain embodiments, the leg has a first guide element and the through hole includes a second guide element configured to cooperate with the first guide element to guide movement of the leg through the through hole.

[0041] This ensures optimum sliding and prevents play and movement on axes other than the axis of motion.

[0042] In certain embodiments, one of the guide elements is a groove and the other guide element is a protrusion configured to slide in the groove. [Brief explanation of the drawings]

[0043] To complete the description and to provide a better understanding of the invention, a set of drawings are provided. Such drawings are an integral part of the specification and illustrate embodiments of the invention. The embodiments should not be construed as limiting the scope of the invention, but only as examples of how the invention may be practiced. The drawings include the following figures: [Figure 1] FIG. 1 shows an operational diagram of an apparatus for laying a foundation for a wind turbine tower according to the present invention. [Figure 2] FIG. 2 shows a detail of the guide system of the legs relative to the holes in the first body of the device for laying a foundation for a wind turbine tower according to the invention. [Figure 3] FIG. 3 shows the steps in assembling the device according to the invention. [Figure 4] FIG. 4 shows the steps in assembling the device according to the invention. [Figure 5] FIG. 5 shows the steps in assembling the device according to the invention. [Figure 6] Figure 6 shows the leg length relative to the dimensions of the device. DETAILED DESCRIPTION OF THE INVENTION

[0044] The following reference numerals are used in the above drawings: 1. First Body 2 Second Body 3 supporting books 4 legs 5 Center of the first body 6 First body arm 7 First body through hole 8 Mooring Cable 9 Yaw stabilization protrusion 10 Windmill Tower 11 Front and rear stabilization plates 12 Slide roller 13 Guide protrusion 14 Guide groove 15 Hydraulic cylinder 20 First surface of second body 21 Second surface of second body 30 Tower Axis 100 First reference surface of first body 101 second reference surface of first body

[0045] The embodiments have been described in sufficient detail to enable those skilled in the art to incorporate and practice the systems and processes described herein, and it is important to understand that the embodiments may be provided in many alternative forms and should not be construed as limited to the examples set forth herein.

[0046] Thus, while the embodiments may be modified in several ways and may take several alternative forms, the drawings show specific embodiments which will be described in detail below by way of example. It is not intended to be limited to the particular forms disclosed. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims. Elements of the illustrated embodiments will, where appropriate, be designated by the same reference numerals consistently throughout the drawings and detailed description.

[0047] FIG. 1 shows an operational diagram of an apparatus for laying a foundation for a wind turbine tower according to the present invention.

[0048] In this figure, the device is shown without the wind turbine tower and without the waterline reference.

[0049] The device comprises a first body 1 and a second body 2 .

[0050] Above the first body there is a support 3 attached to the first body 1. This support 3 serves to receive the wind turbine tower and is therefore cylindrical inside. This support 3 defines a tower axis 30 which serves as a reference for defining the orientation of the other elements.

[0051] The first body 1 has a core 5 which is connected to the support 3. This core 5 is also cylindrical and concentric with the support 3. This fixes the wind turbine tower in the centre of the foundation laying device.

[0052] The first body 1 has a central portion 5 and a plurality of arms 6 connected to the central portion 5. Each of the hollow arms 6 extends radially from the central portion 5 and includes an upper surface perpendicular to the tower axis and a lower surface parallel to the first surface. The upper surface of each hollow arm is included in a first reference plane 100, and the lower surface of each hollow arm is included in a second reference plane 101. Thus, the first reference plane 100 is farther from the second body 2 than the second reference plane 101. These arms 6 are hollow to allow adjustment of the levitation provided by the first body 1.

[0053] The device further comprises a second body 2. The second body 2 is intended to be fully submerged at a depth of several meters, in contrast to the first body 1, which is intended to be located near (but below) the sea surface. The second body 2 has a first face 20 and a second face 21 parallel to the first and second reference faces, the first face 20 being closer to the first body 1 than the second face 21.

[0054] The movement of the second body 2 relative to the first body 1 is achieved by a series of cylindrical legs 4. These legs 4 are integrally fixed to the second body 2 and are inserted into through-holes 7 in the first body 1, which extend from the upper surface to the lower surface of each arm. During transportation, the first body 1 and the second body 2 are positioned very close to each other, so the legs 4 protrude several meters above the first body 1. When the device reaches the foundation location, the second body 2 is lowered, along with the legs 4 attached to the second body 2, so that the legs 4 slide through the through-holes 7 in the first body 1. Once in the final position, the device includes a locking system that locks the relative position between the legs 4 and the first body 1 in the operating position to prevent the legs 4 from moving relative to the first body 1 due to waves or forces experienced by the device. This would change the distance between the first body 1 and the second body 2, impairing the device's operation for laying the foundation.

[0055] Both the first body 1 and the second body 2 have ballast management elements that selectively allow water to enter or exit the corresponding body, thereby allowing the buoyancy of both bodies to be controlled during the transport, assembly, lowering and final fixation process of the device.

[0056] The first body 1 has a volume and weight configured to provide a buoyancy of 25% of the weight of the entire device when empty, with the empty weight of the first body 1 being approximately 4% of the weight of the entire device, while the empty weight of the second body 2 is approximately 90% of the weight of the entire device, resulting in a very low center of gravity and a very high center of buoyancy, improving the stability of the system.

[0057] Furthermore, the central portion 5 is hollow and has a major cross section (measured perpendicular to the cylindrical axis) that has a larger area than the cross sections of either of the hollow arms (measured along the axis along which each arm extends).

[0058] The second body 2 has a hollow, chamfered triangular shape, with each chamfered vertex of the triangle receiving one of the legs 4. This hollow interior provides stability for the weight.

[0059] Each of the legs 4 includes a stopper configured to cooperate with each of the through holes 7 to prevent the legs 4 from coming off the first body 1 as the second body 2 descends and the distance that each of the legs 4 protrudes decreases.

[0060] The diagram also shows two stability elements.

[0061] Firstly, there are a number of planar protrusions 9 arranged radially from the support 3, the axial dimension of which is greater than the radial dimension of the support. The protrusions extend radially from the axis of the support 3, and as a result are taller than their length, allowing stabilisation of the system in yaw.

[0062] Next, there are planar plates 11 extending from the lower base of the first body 1. These planar plates allow for fore and aft instability to be controlled, increasing the natural period of the device for fore and aft vibrations by increasing mass and damping so that the overall stability of the device is increased.

[0063] FIG. 2 is a cross-sectional view of some of the elements that make up the device according to the invention.

[0064] In this view, the hollow arm 6 has been cut away to allow a better understanding of the elements included in this view.

[0065] As shown in the previous figure, the legs 4 are inserted into through holes 7 located in each arm 6. Inside the arms are rollers 12 that ensure the legs slide precisely, without any play or movement in any direction other than the vertical direction. This prevents the legs from wearing out due to the forces coming from the shaft.

[0066] This figure also shows the projections and grooves of the legs 4. This guidance is provided by cooperation of vertical projections 13 formed on the legs with grooves 14 formed in the through holes 7, which are suitable for receiving the projections 13 and guiding the legs 4.

[0067] In addition to the above, there are also hydraulic locking cylinders 15 intended to fix the position of the legs 4 once they have reached their final position.

[0068] 3 to 5 show different steps in the assembly of the device according to the invention.

[0069] FIG. 3 shows the assembly formed by the device for laying the foundation and the wind turbine tower 10 assembled to a support 3 on land.

[0070] The ability to install equipment in the port area using land-based means reduces the logistics process and removes the risks inherent in offshore operations and between two objects with different relative movements due to different buoyancies.

[0071] A number of tugboats may then transport the structure to the installation site.

[0072] As shown in Figure 4, at the installation site, the ballast means is activated to fill the second body 2 with water, which causes the second body 2 to be submerged and the legs 4 to slide through the through holes in the first body 1. This assumes that the legs 4 are integrally attached to the second body 2 and therefore descend together with the second body 2.

[0073] Figure 5 shows how the legs 4 are fixed relative to the first body 1 so that the distance between the first body 1 and the second body 2 remains constant after the second body 2 has reached its operating position. The first body 1 is then partially ballasted so that it is submerged. Finally, mooring cables 8 are deployed to secure the first body 1 to the seabed.

[0074] FIG. 6 shows that the leg has a length LL that is greater than the sum of the distances between the first reference surface and the second reference surface L1 plus 55% of the distance between the first reference surface and the second surface of the second body L2.

[0075] LL>L1+0.55·L2

[0076] Therefore, the visible length of the structure after it is fully deployed is at least 55% of the distance between the first reference plane and the second plane of the second body, ensuring that the distance between the first body and the second body positively contributes to the stability of the device after it is deployed and installed at sea.

Claims

1. 1. An apparatus for supporting a wind turbine tower, the apparatus including: a first body; a support attached to the first body; a second body; and a plurality of legs attached to the second body; the support has a cylindrical interior defining a tower axis and is configured to provide support and connection for a wind turbine tower; the first body includes a central portion connected to the support and a plurality of hollow arms connected to the central portion, each of the hollow arms extending radially from the central portion and including a first surface perpendicular to the tower axis and a second surface parallel to the first surface, the first surface of the hollow arm being included in a first reference plane and the second surface of the hollow arm being included in a second reference plane, the first reference plane being farther from the second body than the second reference plane; each of the hollow arms includes a through hole extending from the first surface to the second surface, the through hole configured to allow a leg to pass therethrough; the first body has a volume and weight configured to provide a buoyancy when empty that is at least 20% of the weight of the entire device, and the weight of the first body is less than 8% of the weight of the entire device; the first body having a first ballast management element that selectively allows water to enter and exit the first body; the second body has a first surface and a second surface, both of which are parallel to the first reference surface and the second reference surface, and the first surface is closer to the first body than the second surface; the second body having a ballast management element that selectively allows water to enter and exit the second body; The device, wherein the leg and / or the first body has a locking system configured to lock the relative position between the leg and the first body.

2. 2. The device of claim 1, wherein the leg has a length greater than or equal to the sum of the distance between the first reference surface and the second reference surface and 55% of the distance between the first reference surface and a second surface of the second body.

3. 3. The device of claim 1 or 2, wherein the through-holes include a plurality of rollers to ensure smooth sliding of the legs within the through-holes.

4. 4. The apparatus of claim 1, wherein the central portion is hollow and has a main cross section having a larger area than a cross section of any of the hollow arms, the main cross section including the tower axis, the cross section of the hollow arms being measured according to a plane perpendicular to the tower axis and perpendicular to a first face of the hollow arms.

5. 5. The device of claim 1, wherein each of the legs includes a stopper configured to cooperate with a respective one of the through holes to prevent the leg from exiting the first body.

6. 6. The device of claim 1, wherein the locking system comprises a hydraulic cylinder.

7. 7. The device according to any one of the preceding claims, wherein the second body has the shape of a chamfered hollow polygon, preferably a chamfered hollow triangular shape.

8. 8. The device of claim 1, wherein each of the chamfered vertices of the triangle receives one of the legs.

9. 9. The device of claim 1, wherein the support comprises a plurality of planar projections arranged in a radial direction, the axial dimension of the support being greater than the radial dimension.

10. 10. The apparatus of claim 1, wherein the first body includes a planar plate extending from a base of the first body proximate the second body.

11. 11. The apparatus of claim 1, further comprising a tether attached to the first body.

12. 12. The device of claim 1, wherein the legs have a cylindrical shape.

13. 13. The device of claim 1, wherein the leg has a first guide element and the through hole includes a second guide element configured to cooperate with the first guide element to guide movement of the leg through the through hole.

14. 14. The device of claim 13, wherein one of the guide elements is a groove and the other guide element is a protrusion configured to slide in the groove.

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