OFFSHORE SUPPORT STRUCTURE FOR WIND TURBINES

Description

[0001] The invention relates, according to the preamble of claim 1, to an offshore support structure for wind turbines, which can be connected to several, preferably six, piles anchored in the seabed, comprising: a receptacle for a tower of a wind turbine, a truss structure which can be connected to the piles and is composed of a plurality of tubes and which can be assembled from a plurality of prefabricated truss segments, wherein a segment has a plurality of tubes connected by means of an X-node and a plurality of tubes which are arranged essentially horizontally during operation and form a ring, and wherein the truss structure has a plurality of base nodes by means of which the truss structure can be coupled directly or indirectly to the piles.

[0002] Such support structures are used in particular for the installation of wind turbines (WTs) in offshore regions with great water depths. The offshore wind turbines and support structures are exposed to extreme conditions. They are often anchored at depths of 20 to 60 meters using the support structure. The support structure is exposed to high mechanical and chemical stresses. Various types are known, for example monopile, jacket, tripod, triple pile, or bucket constructions. The present invention primarily relates to a so-called jacket construction. This is a truss construction made of rod-shaped elements, in particular welded steel tubes. Such offshore structures are described, for example, in EP 3 056 611 A1, DE 20 2012 005 538 U1, and EP 2 067 914 A1.

[0003] Base nodes of the truss structure are located in the lower part of the supporting structure and serve to connect the pipes in the lower area and to transfer the weight forces to the foundation piles anchored in the seabed. In the area of the base nodes, the essentially X-shaped pipes, which are connected to each other by an X-node, converge on the one hand, and the essentially horizontally arranged pipes forming a ring, forming a ring. Several pipes connected by an X-node are also referred to below as X-pipes. A connection to the piles is established from the base nodes. This can be made directly from the node or with the interposition of additional connecting elements, in particular pipe segments.

[0004] Due to the increasing size of wind turbines, the demands placed on offshore support structures regarding their load-bearing capacity and continuous load are increasing. Furthermore, cost considerations aim to minimize material consumption while maintaining high load-bearing capacity and good manufacturability. Key components of the support structure are made of steel and are joined together using numerous welded joints.

[0005] As support structures for larger wind turbines become larger, the base nodes also become larger in order to be able to absorb and transfer the required loads. In practice, it has been shown that difficulties arise in the area of the base nodes due to the large number and density or proximity of the required welds relative to one another to connect the individual tubes or tube segments. For example, the X-tubes and the tubes forming a ring have to be welded in a relatively small space. Welds generally represent weak points. In the area of the base nodes, these are in the area of enormous forces, because the weight forces are at their greatest in the area of the base nodes. The sheer number of welds is a challenge, and the relatively close proximity of different welds can lead to strength problems or material weakening.The conditions are also made more difficult by the fact that the pipes have to be arranged at different angles to each other and fastened in the area of the base nodes.

[0006] The object of the present invention is to provide a support structure and a method that at least partially avoids the disadvantages of the prior art and can transmit the large, dynamic forces of a wind turbine with minimal design effort, preferably in the lower area of the so-called footnotes. Furthermore, the assembly and weldability are to be optimized, particularly in the area of the foot nodes.

[0007] The problem is solved by an offshore support structure having the features of claim 1.

[0008] According to the invention, a base node comprises a lower pipe segment during operation and a preferably welded adapter plate attached to the top of the pipe segment, which adapter plate can be coupled directly or indirectly to at least one pipe of the truss structure connected by an X-node during operation. According to the invention, a base node is essentially, but not necessarily exclusively, formed by the adapter plate and the lower pipe segment arranged underneath it, which could also be referred to as the base pipe, to which the pipes can advantageously be attached. By providing a lower pipe segment - arranged essentially vertically during operation - and an adapter plate welded (or otherwise securely attached) in its upper region, the X-pipes can be connected to the base node in a manner that is highly rigid and simultaneously reduces material requirements.The X-tubes, which are connected to each other by means of an X-node of the truss structure, can be connected to the adapter plate directly or indirectly during assembly - if necessary with the interposition of additional components - in particular by welding.

[0009] The geometry and material thickness of the adapter plate and its dimensions can be easily adapted to the size of the X-pipes. On the other hand, the adapter plate is welded (or otherwise connected) to the pipe segment below it. This pipe segment and the adapter plate can be dimensionally coordinated and designed accordingly to save material. The adapter plate enables load transfer from the X-pipes via the lower pipe segment through the base node to the piles. Appropriate dimensioning can reduce the total number of welds required. The welded joints can also be spatially offset. The overall welding work can be reduced, which saves material and time. The adapter plate enables smaller pipe diameters overall, particularly for the lower pipe segment.Given the considerable dimensions, with the base nodes several meters long, this results in significant material savings. It has also been shown that, for example, fatigue calculations can achieve advantageous load-bearing capacities and strengths.

[0010] Furthermore, the invention provides that two adapter tubes arranged essentially in a V-shape relative to one another are fastened, preferably welded, to the adapter plate, wherein each adapter tube is connectable, preferably weldable, to an (X-) tube of the truss structure. With the aid of preferably two adapter tubes fastened to the adapter plate, the X-tubes can be connected to the base node in a particularly advantageous manner, in particular by welding. The adapter tubes can be geometrically adapted to the dimensions of the X-tubes. Overall, this reduces the welding effort. Furthermore, the welded connections between adapter tubes and X-tubes and adapter plate can be produced successively in a simpler manner.

[0011] To increase the strength, it is proposed that a gusset plate is arranged, preferably welded, between the two V-shaped adapter tubes for stiffening.

[0012] A further preferred embodiment provides that the adapter plate is essentially in the shape of a circular disk, the diameter of which is preferably larger than the outer diameter of the lower pipe segment. Thus, only the diameter of the adapter plate needs to be increased to establish a simple connection to the X-shaped pipes, without requiring an increase in the diameter of the lower pipe segment, which has considerable dimensions. According to the invention, material can be saved if its diameter can remain as relatively small as possible.

[0013] According to a further development of this embodiment, it is proposed that the lower tube segment be further connected, preferably welded, to two essentially horizontal tubes of a lower ring during operation. The diameter of the lower tube segment is expediently larger than the diameter of a horizontal tube of the truss structure. This creates a robust base node structure overall.

[0014] According to a preferred development, it is proposed that the foot node is completely welded to two horizontal tubes arranged in a V-shape relative to one another and to the adapter plate and, by means of the adapter plate, to two upper V-shaped adapter tubes and, by means of these, to two X-tubes.

[0015] Overall, the loads can be absorbed favorably with little material expenditure if, according to a further development, each truss segment has six horizontal tubes forming a ring and six X-shaped tube structures each consisting of two tubes arranged in an X-shape to one another, whereby two, three or more truss segments can be arranged one above the other depending on the required size of the supporting structure.

[0016] According to a further aspect, the object is achieved by a method having the features of claim 9, i.e. a method for producing an offshore support structure according to the preceding claims, wherein the support structure is designed as a truss structure composed of a plurality of tubes and a base node has a lower tube segment and an adapter plate as well as two adapter tubes arranged in a V shape relative to one another, in which the adapter tubes are welded to tubes of the truss structure forming an X. By first welding the X-tubes to the adapter tubes, manufacturing advantages can be achieved. Preferably, the adapter plate is then welded to the lower tube segment. The base node itself is advantageously connected to a pile by means of a welded connection.

[0017] Further features and advantages of the invention will become apparent from the dependent claims and the following description of preferred embodiments with reference to the drawings. Fig. 1 shows an embodiment of an offshore support structure according to the invention with foot nodes according to the invention in a perspective view; Figure 2 shows the support structure in a side view; Figure 3 shows a part of the support structure in a perspective view; Figure 4 shows a part of the support structure in a side view; Figure 5 shows the several (six) central foot nodes in the lower region of the support structure above the piles in a perspective view; Figure 6 shows a foot node in an enlarged perspective view; and Figure 7 shows the foot node in a perspective view.

[0018] Evidentially Fig. 1The support structure 1 according to the invention for wind turbines 9 (WEA) has a truss structure 4, which can also be referred to as a jacket section 4, which comprises a plurality of bars, struts, in the exemplary embodiment preferably tubes 3, which are connected to one another in a truss-like manner.

[0019] The supporting structure 1 with a longitudinal axis A which is essentially vertical during operation is designed according to Figure 1can be coupled by means of six piles 30 anchored in the seabed. The lower jacket section 4 is connected to the piles 30 in the assembled state. It has a substantially hexagonal cross-section relative to a longitudinal axis A. The jacket section 4 is essentially tapered from bottom to top and has, for example, three superimposed truss segments 6, 8, 10, which are arranged coaxially to one another. The segments 6, 8, 10 and tubes 3 are connected to one another by means of nodes 5, 7. Node 5 is designed as a so-called rounded node; for details on this node 5, reference is made in particular to WO 2013 / 139816 A2, in which these nodes are described in detail. Two obliquely arranged tubes 3 each form an X-shape. They are connected to one another at a node 7. Several pipes 3 connected by means of an X-node 7 are also referred to below as X-pipes 3.

[0020] The Figure 2 The X-node 7 shown as an example encloses two acute and two obtuse angles between its legs and is designed to connect X-tubes 3 to one another. The tubes 3 are connected to one another by means of the node 7 in such a way that they all lie essentially in one plane. All nodes 5, 7 can alternatively or preferably be designed as double-tube structures. The tubes 3 are preferably connected to the nodes 5, 7 by orbital welding.

[0021] In each segment 6, 8, 10, a total of six X-shaped structures, each consisting of two or four X-tubes 3, are arranged. Two adjacent segments 6, 8, 10 are connected to each other by means of a circumferential ring, wherein the ring here has a hexagonal shape and is formed from adjacent and welded tubes 3, which are arranged essentially horizontally during operation.

[0022] As in particular Figures 1 to 4show, at the top of the supporting structure 1 there is a mount 16 for a tower (not shown) of a wind turbine 9 (in Fig. 1 and 2 (only indicated) a so-called transition piece with a transition piece tube 18 is arranged. The receptacle 16 is connected to the upper node of the uppermost segment 6. Tube 18 has a recess which extends along a substantially vertical longitudinal axis A and is cylindrical. In the exemplary embodiments, a force transmission module 20 is designed with a plurality of sheet metal segments 22 for transmitting forces, which extend substantially in the vertical direction during operation. The plurality of sheet metal segments 22 are designed and suitable for transmitting and dissipating forces due to the loads of the wind turbine downwards into the support structure 2.

[0023] A foot node 12 (enlarged in Figures 5 to 7) is designed to connect four tubes 3 to each other and represents an interface for connecting the support structure 2 to the piles 2. In the exemplary embodiment, six base nodes 12 are provided; a different number may be appropriate for that structure. The base node 12 has a - during operation lower - tube segment 24, which can also be referred to as base tube 24, as well as a preferably welded adapter plate 14 attached to the top of the tube segment 24, which adapter plate can be coupled directly or indirectly to at least one tube 3 of the truss structure 4 connected by means of an X-node 7 (see Fig. 2 , 6 and 7 ).

[0024] At least one adapter tube 17, or in the exemplary embodiment, two adapter tubes 17 arranged essentially in a V-shape relative to one another, are fastened to the adapter plate 14, namely welded, wherein each adapter tube 17 can be connected, preferably welded, to a tube 3 of the truss structure 4. The angle of the adapter tubes 17 is adapted to the acute angle of the X-node 7 or the course of the X-tubes 3. A gusset plate 19 is arranged, preferably welded, between the two V-shaped adapter tubes 17 for stiffening. The gusset plate 19 widens outwards in order to create a sufficiently long contact surface and thus the length of the weld seam with respect to the adapter tube 17.

[0025] The adapter plate 14 essentially has the shape of a circular disk, the Fig. 7illustrated diameter D is preferably larger than the outer diameter d of the lower pipe segment 24 and is also significantly larger than the diameter d of the X-pipe 3. The lower pipe segment 24 is connected in the assembled state, i.e. during operation, preferably by welding to two essentially horizontal pipes 3 which form a lower ring. This welded connection is made below the adapter plate 14. Diameter d of the lower pipe segment 24 is larger than the diameter d of a horizontal pipe 3 of the truss structure 4. This thus achieves that the base node 12 is completely welded to two horizontal pipes 3 arranged in a V shape relative to one another and to the adapter plate 14 and, by means of the adapter plate 14, to the two upper V-shaped adapter pipes 117 and, by means of these, to two X-pipes 3. At the bottom, the supporting structure 1 is coupled to six piles 2 by means of a welded connection by means of six base nodes 12.

[0026] To manufacture and assemble the offshore support structure 1 of the type described above, the preferred procedure is to weld the adapter pipes to X-pipes of the truss structure 4. Then, the adapter plate 14 is welded to the lower pipe segment 24. The base node 12 is connected to a pile 2 by means of a flange or welded connection. List of reference symbols

[0027] 1 Offshore support structure 2 Piles 3 Pipes 4 Truss structure (jacket section) 5, 7 Nodes 6, 8, 10 Truss segments 9 Wind turbine 12 Base node 14 Adapter plate 17 Adapter pipe 16 Support 19 Gusset plate 18 Transition piece pipe 20 Power transmission module 22 Plate segment 24 Pipe segment (base pipe)

Claims

1. Offshore support structure (1) for wind turbines, which can be connected to several, preferably six piles (2) anchored in the seabed, comprising: a mount for a wind turbine tower, a truss structure (4) connectable to the piles (2) and composed of a plurality of tubes (3), which can be assembled from a plurality of prefabricated truss segments (6, 8, 10), wherein a segment (6, 8, 10) has a plurality of tubes connected by means of an X-joint and a plurality of tubes arranged essentially horizontally in operation and forming a ring, and wherein the truss structure (4) has a plurality of foot joints (12) by means of which the truss structure (4) can be coupled to the piles (2), characterized in that a foot node (12) has a lower pipe segment in operation and an adapter plate (14) fastened at the top of the pipe segment, preferably by welding, which, during operation, can be coupled directly or indirectly to at least one pipe of the truss structure (4) connected by means of an X-joint, wherein two adapter pipes arranged substantially V-shaped relative to each other are fastened, preferably welded, to the adapter plate (14), wherein each adapter pipe can be connected, preferably welded, to a pipe of the truss structure (4).

2. Offshore support structure (1) according to claim 1, wherein a gusset plate is arranged, preferably welded, between the two V-shaped adapter tubes for stiffening purposes.

3. Offshore support structure (1) according to claim 1 or 2, wherein the adapter plate (14) essentially has the shape of a circular disc whose diameter is preferably greater than the outer diameter of the lower pipe segment.

4. Offshore support structure (1) according to at least one of the preceding claims, wherein the lower pipe segment is connected, preferably welded, in operation to two substantially horizontal pipes of a lower ring.

5. Offshore support structure (1) according to claim 4, wherein the diameter of the lower pipe segment is greater than the diameter of a horizontal pipe of the truss structure (4).

6. Offshore support structure (1) according to at least one of the preceding claims, wherein the foot node (12) is completely welded to two horizontal pipes arranged in a V-shape relative to each other and to the adapter plate (14) and, by means of the adapter plate (14), to two upper V-shaped adapter pipes and, by means of these, to two X-shaped pipes.

7. Offshore support structure (1) according to at least one of the preceding claims, wherein six foot nodes (12) are coupled to six piles (2) by means of flange connections or welded connections.

8. Offshore support structure (1) according to at least one of the preceding claims, wherein each truss segment comprises six horizontal pipes forming a ring and six X-shaped pipe structures, each comprising two pipes arranged in an X-shape relative to each other.

9. Method for manufacturing an offshore support structure (1) according to one of the preceding claims, wherein the support structure (1) is designed as a truss structure (4) composed of a plurality of tubes (3) and a foot node (12) has a lower tube segment and an adapter plate (14) as well as two adapter tubes arranged in a V-shape relative to each other, wherein the adapter pipes are welded to pipes of the truss structure (4) forming an X.

10. Method according to claim 9, wherein the adapter plate (14) is welded to the lower pipe segment.

11. Method according to claim 9 or claim 10, wherein the foot node (12) is connected to a post by means of a flange or welded connection.