Mooring Systems for Floating Wind Turbines

Abstract

The present invention relates to a foundation element 10 having a universal joint 20, 20' with a first universal joint member 22 co-rotatably connected to the foundation element 10 and a second universal joint member 24 which is rotatable about the longitudinal axis of the first universal joint member 22 by performing rotation about its own longitudinal axis, a floating wind turbine 100 and a floating wind turbine 100 having one end connected to the foundation element 10 by a first connection means 50 co-rotatably connected to the second universal joint member 24 and the other end connected to the floating wind turbine 100 by a second connection means 120 which is rotatably mounted on the floating wind turbine 100. and a mooring line 30, 130 connected to the floating wind turbine 100, wherein the controller causes the adoption of a rotational position of a second connection means 120 rotatably mounted on the floating wind turbine 100 based on a rotational position of the floating wind turbine 100 about the base element 10, the rotational position of the second connection means 120 rotatably mounted on the floating wind turbine 100 corresponding to a rotational position about a longitudinal axis of the second universal joint member 24, which rotational position geometrically corresponds to a rotational position of the floating wind turbine 100 about the base element 10.

Description

[Technical field]

[0001] The present invention relates to a mooring system for fixing a floating wind turbine to the bottom of a body of water. In particular, the present invention relates to a system comprising a foundation element with a universal joint having a first axle stub rotationally fixedly connected to the foundation element and a second axle stub which is rotatable about the longitudinal axis of the first axle stub by performing a rotation about its longitudinal axis, a floating wind turbine and a mooring line connected at one end to the foundation element by a first connection means rotationally fixedly connected to the second axle stub and at the other end to the floating wind turbine by a second connection means rotatably mounted on the floating wind turbine. [Background technology]

[0002] Such a system is known in particular from US Pat. No. 5,399,633, which discloses a self-aligning floating wind turbine designed as a leeward runner fastened to the bottom of the body of water at a single fixed point by means of only one mooring line. The mooring line is connected to the foundation element by a first universal joint and to the single-point moored wind turbine by means of a second universal joint. Also, the upper end of the mooring line is rotatably mounted on the wind turbine.

[0003] Furthermore, a single-point moored wind turbine is known from US Pat. No. 5,399,633, in which the connection between the mooring line and the floating wind turbine comprises a slip coupling and a vortex coupling which can be gimbaled separately or together. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102004056401 [Patent Document 2] German patent no. 102013111115 Summary of the Invention [Problem to be solved by the invention]

[0005] Known wind turbines have a partially very complicated structure which is difficult to realise. Therefore, the object of the present invention is to further develop a system comprising a foundation element, a floating wind turbine and mooring lines connecting the foundation element to the floating wind turbine, which is as simple as possible to build and efficiently install and maintain. [Means for solving the problem]

[0006] According to the invention, this object is achieved by a system having the features of claim 1. The dependent claims reflect advantageous embodiments of the invention.

[0007] The basic idea of ​​the invention consists in fixing the floating wind turbine to only one fastening point or foundation element at the bottom of the water body by mooring lines so that the floating wind turbine can turn itself according to the wind direction like a ship at anchor. This means that there is only one connection between the foundation element at the bottom of the water body and the floating wind turbine. For this, the foundation element at the bottom of the water body must be designed not only to absorb horizontal forces but also to absorb vertical loads. For this purpose, pile foundations or suction bucket foundations at deeper water depths are also suitable for this purpose. However, the type of connection of the foundation element to the bottom of the water body can also be of redundant design for safety reasons.

[0008] In order to prevent the mooring lines from tangling during the inevitable rotation of the entire floating wind turbine around the foundation element on the bottom of the body of water, suitable devices exist that actively counteract torsion. According to the invention, this is achieved by arranging a Cardan-type but torsionally rigid suspension on the foundation element, which always aligns the mooring lines from the foundation element in the direction of the floating wind turbine without tangling. To prevent the mooring lines from rotating during the rotation of the floating wind turbine around the foundation element, the mooring lines also rotate simultaneously around their own longitudinal axis on the floating wind turbine.

[0009] Cardan suspension is realized by conventional universal joints or eccentric universal joints with intersecting joint rotation axes. Conventional universal joints allow bending angles of 35 to 45 degrees or less, while eccentric universal joints allow bending angles of up to 90 degrees.

[0010] A rotary drive is preferably located on the floating wind turbine and is capable of rotating a slewing gear having a thrust bearing to which connection means for connecting the mooring lines to the wind turbine are attached, the rotary drive being controlled via a sensor system which determines the current position and also preferably the alignment of the floating wind turbine with respect to a foundation element.

[0011] For redundancy, the connection between the foundation element at the bottom of the water body and the floating wind turbine can preferably consist of two independent parallel mooring lines. The mooring lines are particularly preferably of about 1000 kg / m 3and is preferably a composite rope with a certain elasticity in order to damp as much as possible the dynamic forces acting on the floating wind turbine due to wind and wave loads. Most preferably, two mooring ropes are guided in parallel and doubled, so that the loads are distributed substantially evenly over the four cables. The mooring ropes are preferably designed in two parts, the ends of which are most preferably fastened to a connector designed as a buoy located close to the floating wind turbine. In this case, the sections of the mooring rope are placed on a foundation element on the bottom of the water body by means of blocks or idler pulleys, respectively, and are again guided upwards to the connector. The connection is made by two parallel mooring ropes in order to have redundancy in case of failure of one of the mooring ropes. This design makes it possible to replace the mooring ropes without the need for divers or submersibles to carry out work on the bottom of the water body.

[0012] The length of the section of the mooring line between the foundation element and the connector should be selected rationally so that the connector, having been decoupled from the wind turbine, can be floated up and float above the water surface, and particularly preferably also raised a few meters above the water in order to allow maintenance operations, e.g. replacement of the mooring line, to be carried out on board, while the connection should also not be too long so that the mooring line does not touch the bottom of the water body.

[0013] If the mooring line is designed in two sections and the two sections are connected to each other by a connector, further connection means are provided on the underside of the connector facing the foundation element and on the upper side of the connector not facing the foundation element in order to connect the sections of the mooring line to the connector. These further connection means are preferably provided redundantly in both cases and particularly preferably duplicated. However, the length of the section between the connector and the wind turbine is designed to be shorter than the length of the section between the foundation element and the connector. Both sections of the mooring line can consist of synthetic or steel cables. In both cases, the sections of the mooring line are detachably connected to the connector.

[0014] In principle, it is provided that the power cable connecting the wind turbine to the grid is also preferably guided between the mooring lines and parallel to them. The electrical connection at the connector can be released in order to free the floating wind turbine from the mooring system, for example to tow it to a port for repairs or maintenance. In this state, the connector designed as a buoy floats on the water surface, so that reconnection to the floating wind turbine can be easily performed on the water surface after repairs are completed. The power cable is preferably guided through the center of a universal joint on the foundation element at the bottom of the water body and exits through the foundation element and is connected to the outgoing subsea cable. The power cable from the floating wind turbine to the foundation element must have a certain material elasticity or geometrical elasticity so that it can follow the movements of the mooring lines and does not accumulate unacceptably large mechanical residual stresses. On the floating wind turbine side, the power cable runs through the center of a thrust bearing. Therefore, when the alignment of the floating wind turbine changes due to a change in wind direction, the rotary drive also rotates to compensate for the twisting of the connection and the power cable twists from the mooring line inside the wind turbine to the opposite side of the thrust bearing. To untwist the power cable when it reaches its tolerable limit of twisting, the floating wind turbine is disconnected from the grid by means of a medium voltage switchgear and the twisted power cable is untwisted by means of an electrical coupling known in particular from DE 102017119635 A1.

[0015] The rotation drive, which compensates for possible twists in the mooring lines (and power cables) between the foundation element and the floating wind turbine, is controlled, for example, by a compass that determines the alignment of the floating wind turbine with respect to the foundation element at the bottom of the body of water. Since the universal joint is not a constant velocity joint, the relationship between the rotation angle of the joint's pivot axis and the rotation angle around the vertical axis of the other side of the joint is not linear, but is subject to an angular function that depends on the bending angle of the universal joint. If a simple joint bends by a bending angle β and rotates in this state, the angle (φ 2(i.e., the rotation angle of the second axial bar stub) is the angle (φ 1 (i.e., the rotational position of the second shaft stub). The following relationship exists between the angles:

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[0016] In addition, in the rare situation of no wind, current or waves, it is preferable to ensure that the distance between the foundation element and the floating wind turbine does not fall below a minimum value, in order to prevent the mooring lines from touching the bottom of the body of water or from twisting the slack mooring lines. This is achieved, for example, by detecting the current position of the floating wind turbine relative to the position of the foundation element, by means of a satellite-based positioning system, and preferably when the distance falls below a predetermined minimum distance, i.e. when slack is present, a drive, in particular a ship's drive, is activated to propel the wind turbine away from the position of the foundation element, keeping the mooring lines slightly taut. The drive, preferably electrically driven, can be designed as a propeller or in the manner of a lateral jet control system. As an alternative to using a satellite-based positioning system, the tensile stress of the connection means can also be detected and an appropriate propulsion initiated when the tensile stress falls below a predetermined level.

[0017] Therefore, according to the invention a system is proposed comprising a foundation element with a universal joint, the universal joint having a first axial rod stub rotationally fixedly connected to the foundation element and a second axial rod stub which is rotatable around the longitudinal axis of the first axial rod stub by rotating about its longitudinal axis, a floating wind turbine and a mooring line, one end of which is connected to the foundation element by a first connection means rotationally fixedly connected to the second axial rod stub and the other end of which is connected to the floating wind turbine by a second connection means rotatably mounted on the floating wind turbine, wherein a controller is provided for adjusting a rotational position of the second connection means rotatably mounted on the floating wind energy plant depending on the rotational position of the floating wind turbine around the foundation element, the rotational position of the second connection means rotatably mounted on the floating wind turbine corresponding to a rotational position of the second connection means rotatably mounted on the floating wind turbine around the longitudinal axis, which corresponds geometrically to a rotational position of the floating wind turbine around the foundation element. In other words, the second shaft stub and the second connection means are always identically aligned with each other in their rotational positions, so that the mooring line does not twist.

[0018] The controller is preferably configured to cause a rotational position of the second connection means rotatably mounted on the floating wind turbine to take into account the alignment of the longitudinal axis of the floating wind turbine with respect to the foundation element, for which purpose it is particularly preferred that the controller comprises a compass to determine the alignment of the longitudinal axis of the floating wind turbine with respect to the foundation element.

[0019] More preferably, the controller has a sensor for positioning by a global positioning satellite system.

[0020] The controller preferably comprises a rotation drive for rotating the rotatably mounted second connection means, the rotation drive being in particular electrically driven and configured for unlimited rotation of the second connection means in both rotational directions, in particular the rotation drive having a sensor for detecting the rotational position of the second connection means relative to the wind turbine, whereby the controller, when a target rotational position is specified, is able to switch off the rotation drive when this rotational position detected by the sensor is reached.

[0021] It is furthermore preferably envisaged that the floating wind turbine comprises an electrical coupling for connection to an electric power cable connected to an electric power grid arranged outside the wind turbine, the electrical coupling comprising a first electrical plug connector connected to the electric power cable and a second electrical connector complementary to the first electrical connector and connected to the electric power grid located inside the wind turbine, the plug connectors being configured to be movable relative to one another to make and break the electric plug connection and to be rotatable relative to one another to undo the electric power cable connected to the first plug connector. This electrical coupling in particular has the features of the electrical coupling known from DE 102017119635 B1, which is incorporated herein by reference.

[0022] According to another preferred embodiment it is envisaged that the controller comprises a drive, in particular a ship drive, which keeps the floating wind turbine at a defined distance from the foundation element.

[0023] The foundation elements are preferably pile foundations, suction bucket foundations or weight foundations, and the universal joints connected to the foundation elements can be conventional universal joints or eccentric universal joints with intersecting joint rotation axes.

[0024] In any case, the universal joint is surrounded by a bellows that protects the universal joint, which follows the movement of the universal joint and is preferably intended to be made of stainless steel. This bellows is preferably filled with grease to lubricate the universal joint and to protect against corrosion or against seawater and fouling, and most preferably has a restoring force that biases the shaft stub of the universal joint to an extended configuration. Conventional universal joints are used, especially when a bending angle of approximately 35 degrees to 45 degrees is sufficient at the installation site of the floating wind turbine. When larger bending angles are required due to site conditions, it is preferable to use eccentric universal joints that allow bending angles of up to 90 degrees.

[0025] Furthermore, it is preferably provided that the foundation element has a connection configured for connecting to a power cable, this embodiment allows a simple prefabricated construction, which simplifies the additional work of connecting the floating wind turbine to the power grid.

[0026] The connection is especially designed as a plug connector which can or is connected to a power cable for electrically connecting to a power grid arranged outside the wind turbine. Alternatively, the connection can be provided as a bushing which accommodates a cable for connecting to a power grid located outside the wind turbine, through which bushing the power lines connecting the floating wind turbine to the power grid run and are fixed as required.

[0027] In both cases, however, the universal joint has a bushing that accommodates the power cable that is connected to the power grid located outside the wind turbine. In this case, the bushing is located in the center of the axial rod stubs that form the universal joint and the intermediate piece that connects the axial rod stubs to each other. This therefore always ensures that the bending angles and alignment of the universal joint are identical to the bending angles and alignment of the power cable.

[0028] The first and / or second connection means are preferably pulleys around which the mooring lines are guided. It is particularly preferred that further connection means arranged parallel to the first and second connection means and designed as pulleys are provided to guide further mooring lines, respectively. The particularly preferred redundant design of the connection of the foundation element to the floating wind turbine therefore ensures that the turbine continues to be held securely even in case of a mooring line breakage. Overall, therefore, the tensile load of the two mooring lines, each guided around a pulley, is substantially functionally uniformly distributed over the four cables, so that the diameter of the mooring lines can be selected to be relatively small, thereby reducing the weight. The use of idler pulleys on the foundation element has the advantage that work can be carried out on the water surface without the use of divers or submersibles, for example in the case of the need for replacement of the mooring lines due to wear of the mooring lines or at predefined time intervals as prescribed by the certifier. For this purpose, the old mooring line is removed and a new mooring line is installed by connecting the upper end of the mooring line to a new mooring line and then completely withdrawing the entire mooring line.

[0029] The mooring line is in particular of a two-part design, the two sections of which are connected to each other by a connector. Furthermore, the connector is preferably designed as a buoyant buoy. Most preferably, the connector has, on one of its surfaces, a first connection to a first power cable connecting the connector to a power grid arranged outside the wind turbine, and, on the surface opposite this surface, a second connection to a second power cable connecting the connector to the floating wind turbine. This embodiment allows a connection between the sections of the mooring line and thus to the foundation elements of the wind turbine on the surface of the water body.

[0030] In this case, the length of the section connecting the foundation element to the connector corresponds at least to the water depth in the area of ​​the foundation element.

[0031] Furthermore, the mooring line is preferably a cable, in particular a synthetic cable or a steel cable.

[0032] The invention will now be described in more detail with reference to particularly preferred embodiments thereof which are illustrated in the accompanying drawings. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 shows (A) an external view of a particularly preferred design of a system according to the present invention, comprising a floating wind turbine of a particularly preferred design fixed to the bottom of a body of water by a foundation element; (B) a detailed view of a connector of a particularly preferred design connecting mooring lines attached to the foundation to the wind turbine; and (C) a detailed view of the foundation element fixed to the bottom of the body of water. [Diagram 2] 1A and 1B are perspective views of the basic elements of a particularly preferred arrangement comprising a conventional universal joint with intersecting joint rotation axes (A) and an eccentric universal joint (B). [Diagram 3] 1A and 1B are perspective and cross-sectional views showing the connection of mooring lines connected to a foundation element to a floating wind turbine. [Figure 4] 1 shows an external view of a particularly preferred design of a floating wind turbine before it is fixed to the bottom of a body of water (A) and a detailed view in the area of ​​the surface of the body of water (B). [Diagram 5] 5A and 5B are top and bottom perspective views of the connector shown in FIG. 4B for connecting the foundation element to the floating wind turbine. [Figure 6] 1A is a cross-sectional view of the connector in a disconnected state and in a connected state (B). [Figure 7] FIG. 1 is a side view of a floating wind turbine fixed to the bottom of a body of water in two positions caused by different wind directions. [Figure 8] FIG. 1 shows a plan view of a floating wind turbine in four positions caused by different wind directions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Fig. 1 shows (A) an external view of a particularly preferred design of the system according to the invention, comprising a particularly preferred design of a floating wind turbine fixed to the bottom of a body of water by a foundation element, (B) a detailed view of a particularly preferred design of a connector connecting a mooring line attached to the foundation to the wind turbine, and (C) a detailed view of the foundation element fixed to the bottom of the body of water. In particular, Fig. 1A shows a floating wind turbine 100 fixed to the bottom of the body of water by a foundation element 10, which is oriented upwind during operation and clamps a mooring line 30 connecting to the foundation element 10. In this regard, Fig. 4C shows a detailed view of the foundation element 10 fixed to the bottom of the body of water. During operation of the floating wind turbine 100, the angle that the mooring line 30 makes with respect to the bottom of the body of water is substantially the same as the angle that the mooring line passing between the connection of the mooring line 30 to the wind turbine 100 and the tower of the floating wind turbine 100 makes with the foundation of the floating wind turbine 100.

[0035] As a special feature of this exemplary embodiment, the mooring line 30 of the first section, which is connected to the foundation element 10, is not directly connected to the wind turbine 100, but to a connector 200, which is designed as a buoy. As shown in the detailed view of Fig. 4B, the connection of the mooring line 30 of the first section to the floating wind turbine 100 is made indirectly via the connector 200, which is connected to the mooring line 130 of the second section, which is connected to the floating wind turbine 100. It is also provided that the power cable 40', which runs to the foundation element 10, is connected to the connector 200 by means of a plug connection, and another power cable 40'' electrically connects the connector 200 to the floating wind turbine 100. The functions and tasks of the individual elements are described in detail below.

[0036] Fig. 2 shows a perspective view of a first exemplary embodiment of a foundation element 10 with a conventional universal joint with intersecting joint rotation axes (A) and a second exemplary embodiment of a foundation element with an eccentric universal joint (B). In particular, Fig. 1A shows a foundation element 10 designed as a pile foundation for fixing a floating wind turbine 100 to the bottom of a water body. The foundation element 10 has on the upper side a conventional universal joint 20 formed from two axial rod stubs 22, 24 connected to each other by a spherical intermediate part 26. In this case, one axial rod stub 22 is designed to have bending stiffness and is connected to the foundation element 10 in a rotationally fixed manner, while the other axial rod stub 24 is configured to connect to a mooring line 30 that connects the foundation element 10 to the floating wind turbine.

[0037] In particular, the other axial bar stub 24 has, as first connection means 50, two pulleys 50 formed parallel to one another, each of which accommodates a mooring line 30 in the form of a cable guided around a pulley 50 acting as an idler pulley. Between the pulleys 50 or between the cables 30, bushings are provided which accommodate the power cables 40'. The power cables 40' are connected to the floating wind turbine and integrate the latter into the electricity grid. For this purpose, the foundation element 10 has a connection part which is in particular adapted for connection to the power cables 40 and which provides an electrical connection between the power cables 40, in particular designed as submarine cables, which run from the foundation element 10, and the power cables 40' which run from the wind turbine to the foundation element 10.

[0038] The conventional universal joint 20 shown in FIG. 2A has a maximum bending angle of approximately 35 degrees to 45 degrees, while the eccentric universal joint 20 shown in FIG. 2B has a maximum bending angle of up to 90 degrees due to the cubic intermediate piece 26.

[0039] 3 shows a perspective view (A) and a cross-sectional view (B) of the connection of the mooring lines 30 connected to the foundation element to the floating wind turbine 100. The connection of the mooring lines 30 to the underside of the floating wind turbine 100 is in particular designed as a corresponding connection to the foundation element 10. In particular, a connection means 120, here designed as two pulleys 120, is provided, which connects the two mooring lines 30 to the wind turbine 100. The second connection means 120 is rotatably mounted by a swivel device 110 relative to the wind turbine 100. The deflection pulley 120 is in particular fixedly connected to the swivel device 110 via a support frame so as to transfer the wind and wave loads of the floating wind turbine 100 to the mooring system and thus to the foundation element 10 at the bottom of the water body.

[0040] The pivoting device 110 has a bushing for the power cable 40' arranged between the pulleys 120 and is provided with a rotation drive 140 which effects the rotation of the pivoting device 110. The rotation drive 140 is controlled by a controller configured with a device for detecting the rotational position of the floating wind turbine 100 relative to the base element 10. In this regard, the second connection means 120 can be selectively rotated in a controlled manner via the rotation drive 140 so as to prevent twisting of the connection element 30 and the power cable 40' when the horizontal alignment of the floating wind turbine 100 changes. A direction sensor 150 is attached to the floating wind turbine for determining the rotational position of the floating wind turbine 100 around the base element 10 in order to determine the required rotation angle through which the rotation drive 140 must rotate the second connection means 120 so that the connection means 30 extending to the base element 20 is aligned straight, i.e. without rotation. It must be taken into consideration that when the universal joint 20 is bent, the transmission of rotation is uneven.

[0041] Figure 4 shows an external view (A) of the floating wind turbine 100 shown in Figure 1 before it is fixed to the bottom of the water body, and a detailed view (B) in the area of ​​the surface of the water body. In particular, Figure 4A shows the mooring line 30 of the first section fastened to the foundation element 10, the free (upper) end of which is fastened to a connector 200 designed as a buoy. In this case, the mooring line 30 of the first section has a length that corresponds at least to the depth of the water body in the area of ​​the foundation element 10 that is placed on the bottom of the water body. In both cases, the buoyant connector 200 has fastening means on its underside for fastening the mooring line 30 of the first section and the power cable 40'. Figure 4B shows a detailed view of Figure 4A, where it can be seen that the connector 200 in the illustrated example floats above the water surface and the mooring line 130 of the second (upper) section is temporarily fastened to the wind turbine 100. The floating wind turbine 100 has a second connection means 120 to which a second section of mooring line 130 is pre-attached and accompanied so as to be able to connect the wind turbine 100 to the connector 200 at the water surface and thus indirectly to the foundation element 10.

[0042] A particularly preferably provided connector 200 is shown in more detail in a top perspective view (A) and a bottom perspective view (B) in Figure 5. The connector 200, designed as a buoy, essentially consists of a floating body 210 to which are connected additional connection means for fastening sections of the mooring lines 30, 130. In its center there is a waterproof connection box 220', 220'', into which the power cables 40', 40'' are inserted from above and below and are electrically connected to each other.

[0043] Fig. 6 shows a cross-sectional view of a particularly preferably provided connector 200 in the uncoupled state (A) and in the coupled state (B). The float 210 is especially designed to be able to support the weight of the first section of the mooring lines 30 and the lower power cable 40' and to hold the whole unit on the water surface. To release the connection between the foundation element 10 at the bottom of the water body and the floating wind turbine 100, the second section of the mooring lines 130 is mechanically released from the connection buoy 200 and the electrical connection of the power cable 40'' is cut off. For this purpose, the three-phase plug 45'' housed in the connection box 220'' is pulled out from the socket 220''.

[0044] Figures 7 and 8 serve to explain the geometrical relationships fundamentally represented by the system. In this regard, Figure 7 shows in side view a particular configuration of the system according to the invention, where the floating wind turbine 100 is shown in two opposing positions with respect to its alignment with respect to the foundation element 10 on the bottom of the body of water. It can be seen that the floating wind turbine 100 moves around the foundation element 10 in response to the wind direction, and the mooring lines 30 and the power cables are aligned accordingly and held tight by the wind and wave loads. Due to these movements, the mooring lines 30 and the universal joints 20 on the foundation element 10 tilt spatially around the vertical axis in response to the orientation. The angle between the vertical (shown in dashed lines) and the alignment of the mooring lines 30 corresponds to the bending angle β of the second axial bar stub 24 of the universal joint 20.

[0045] Finally, Fig. 8A shows in plan view a particular configuration of the system according to the invention, where the floating wind turbine 100 connected to the foundation element 10 by the mooring lines 30 is shown in four different positions, each offset by 90 degrees. The floating wind turbine 100 rotates around the foundation element 10 in response to the wind and waves, and the mooring lines 30 are held tight by the wind and wave loads. Additionally, one can see the submarine cable 40 connected to the wind turbine 100, which conducts the electrical energy generated by the wind turbine 100 to the transfer station.

[0046] These four positions shown in Fig. 8A are shown in Fig. 8B in a detailed plan view of the base element 10. It can be seen that, based on the alignment of the pulley 50, when the second axle stub 24 of the universal joint 20 rotates about the longitudinal axis of the first axle stub 22, it simultaneously rotates about its own axis, so that the pulley 50 at the position of the second axle stub rotated 90 degrees with respect to its previous position also rotates 90 degrees. In that case, the rotational position of the second axle stub 24 about the first axle stub 22 is rotated by an angle φ 1 and the rotational position of the second axial rod stub 24 about its own axis is represented by an angle φ 2 In other words, the angle between the instantaneous direction of rotation of the mooring line 30 in the horizontal plane and the direction of rotation of the pivot of the universal joint 20 is given by the deviation angle φ 1 The rotation angle of the second shaft stub of the universal joint connected to the mooring line 30 is defined as φ 2 In order to prevent twisting of the mooring lines 30 and the power cables 40, the rotary drive 140 rotates at an angle φ 2 Therefore, the second connecting means 120 must be rotated only by 100 degrees.

[0047] The reason is that a conventional universal joint is tilted by a bending angle β, and when it rotates in this state, the rotation angle of the output shaft is φ 2 is the rotation angle of the input shaft φ 2 The following relationships apply:

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[0048] 10 Basic Elements 20 Universal joint 22 Axle stub 24 Axle stub 26 Intermediate parts 30 Mooring lines, cables, connecting elements, connecting means 40 Power cables, submarine cables 40' Power Cable 40'' Power Cable 45'' plug 50 Connection means, pulley 100 Wind turbine, floating wind turbine 110 Swivel 120 Connection means, pulley 130 Mooring line 140 Rotation drive unit 150 Directional Sensor 200 Connection buoy, connector 210 Floating Body 220' Junction Box 220'' Junction Box β bending angle φ 1 deviation angle, angle φ 2 Angle, Rotation Angle

Claims

1. A base element (10) having a universal joint (20, 20') with a first axial rod stub (22) rotationally fixedly connected to the base element (10) and a second axial rod stub (24) rotatable about the longitudinal axis of the first axial rod stub (22) by performing a rotation about its own longitudinal axis; A floating wind turbine (100); a mooring line (30, 130) connected at one end to the foundation element (10) by a first connection means (50) rotationally fixedly connected to the second shaft stub (24) and at the other end to the floating wind turbine (100) by a second connection means (120) rotatably mounted on the floating wind turbine (100); a controller having a rotation drive (140) for rotating the rotatably mounted second connection means (120); the controller causes a rotational position of the second connection means (120) rotatably mounted on the floating wind turbine (100) depending on a rotational position of the floating wind turbine (100) about the base element (10), and the rotational position of the second connection means (120) rotatably mounted on the floating wind turbine (100) is aligned with a rotational position about the longitudinal axis of the second shaft stub (24).

2. 2. The system according to claim 1, characterized in that the controller is configured to cause a rotational position of the second connection means (120) rotatably mounted on the floating wind turbine (100) taking into account an alignment of a longitudinal axis of the floating wind turbine (100) with respect to the base element (10).

3. The system of claim 2, characterized in that the controller comprises a compass to determine the alignment of the longitudinal axis of the floating wind turbine (100) with respect to the foundation element (10).

4. The system according to any one of claims 1 to 3, characterized in that the controller comprises a sensor for determining the position by means of a global positioning satellite system.

5. 4. The system according to claim 1, wherein the floating wind turbine (100) comprises an electrical coupling (160) for connecting to an electrical power cable (40, 40') connected to an electrical grid located outside the wind turbine (100), the electrical coupling (160) comprising a first electrical plug connector for connecting to the electrical power cable (40, 40') and a second electrical plug connector complementary to the first electrical plug connector and connected to an electrical grid located within the wind turbine (100), the first electrical plug connector and the second electrical plug connector being configured to be movable relative to each other to make and break an electrical plug connection and to be rotatable relative to each other to undo the electrical power cable (40, 40') connected to the first electrical plug connector.

6. The system according to any one of claims 1 to 3, characterized in that the controller comprises a drive for keeping the floating wind turbine (100) at a predetermined distance from the foundation element (10).

7. The system according to any one of claims 1 to 3, characterized in that the foundation element (10) is a pile foundation, a suction bucket foundation or a gravity foundation.

8. A system according to any one of claims 1 to 3, characterized in that the universal joint (20) is a conventional universal joint (20) with intersecting joint rotation axes or an eccentric universal joint (20').

9. A system according to any one of the preceding claims, characterized by a bellows housing said universal joint (20, 20').

10. 10. The system of claim 9, wherein the bellows has a restoring force that biases the shaft stubs (22, 24) of the universal joints (20, 20') in an extended configuration.

11. The system according to any one of claims 1 to 3, characterized in that the foundation element (10) has a plug connector configured to be connected to a power cable (40, 40') connecting to an electric power grid located outside the wind turbine (100).

12. The system according to any one of claims 1 to 3, characterized in that the foundation element (10) has a bushing for accommodating a cable (40, 40') for connection to an electric grid arranged outside the wind turbine (100).

13. The system according to any one of claims 1 to 3, characterized in that the universal joint (20) has a bushing that accommodates a power cable (40, 40') that is connected to a power grid located outside the wind turbine (100).

14. 14. The system according to claim 13, characterized in that the bushing is arranged in the center of the rod stubs (22, 24) forming the universal joint (20) and an intermediate piece (26) connecting the rod stubs (22, 24) to each other.

15. A system according to any one of claims 1 to 3, characterised in that the first connection means (50) and / or the second connection means (120) are pulleys around which the mooring lines (30, 130) are guided.

16. 16. The system according to claim 15, characterized by another connection means arranged parallel to the first connection means (50) and the second connection means (120) and designed as a pulley around which another mooring line (30, 130) is guided.

17. The system according to any one of claims 1 to 3, characterized in that the mooring line (30, 130) is designed in two parts, the two sections (30, 130) of the mooring line (30, 130) being connected to each other by a connector (200).

18. The system of claim 17, wherein the connector (200) is configured as a buoyancy buoy.

19. 18. The system according to claim 17, characterized in that the connector (200) has on one of its surfaces a first connection (220'') for a first power cable (40'') connecting the connector (200) to an electrical grid located outside the wind turbine (100) and on the opposite surface to this surface a second connection (220'') for a second power cable (40'') connecting the connector (200) to the floating wind turbine (100).

20. 18. The system according to claim 17, characterized in that the length of the section (30) connecting the foundation element (10) to the connector (200) corresponds at least to the water depth in the area of ​​the foundation element (10).

21. A system according to any one of claims 1 to 3, characterized in that the mooring lines (30, 130) are cables.

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