MOORING BUOY FOR A FLOATING WIND TURBINE

Description

[0001] The invention relates to a mooring buoy for a floating wind turbine. It is pre-installed and moved to the future location of the wind turbine. It is held in place by a plurality of connecting elements anchored to the seabed. This buoy is detachably connected to the floating wind turbine and also contains the power transmission cable.

[0002] In addition to the established use of onshore wind energy, offshore turbines are also increasingly being built. These turbines are subject to special requirements regarding low maintenance, reliability, turbine size, and environmental impacts. Currently, only ground-based offshore turbines are used, which are firmly connected to the subsoil by steel pipes.

[0003] Installing these systems requires large transport and installation vessels, which are particularly expensive to operate. In addition, for ground-based systems, the water depth is limited and the soil must have specific properties.

[0004] For some time now, however, there has been increasing attention given to floating offshore wind turbines that are more or less rigidly connected to the seabed.

[0005] These floating turbines, which are connected to the ground via chain systems, do not have the aforementioned disadvantages and can be used even in greater water depths. This can significantly expand the range of applications for wind turbines.

[0006] Today's few floating wind turbines are usually permanently connected to the seabed by chains. These chains are usually anchored to the seabed. To install the wind turbines on site, they are transported by tugboats, and the chains are then attached directly to the respective floats.

[0007] This is usually done very quickly and therefore requires a large number of large vessels that must be coordinated on site. This is not only expensive but also time-consuming. Furthermore, the weather window for such an operation is very narrow, as large wave heights are difficult to handle.

[0008] However, WO 2016 / 000681 A1 discloses a floating body anchored to the seabed by means of chains, which enables a floating wind turbine to be mechanically fixed while simultaneously being electrically coupled to a submarine cable.

[0009] However, this poses the problem that the wind turbine floating on the water surface must be connected to the floating body floating on the water surface, although this publication leaves open how this connection should be made. The object of the invention is therefore to create an anchoring system for a floating wind turbine that is safe, quick, and easy to implement.

[0010] This object is achieved according to the invention by the unit formed from a wind turbine and a mooring buoy with the features of claim 1. The subclaims reflect advantageous embodiments of the invention.

[0011] According to the invention, a buoy with a conical outer surface is used, with the small diameter of the cone facing upwards. The buoy preferably has a floodable and drainable annular water tank. The interior of the annular buoy is open. A rotary joint is arranged in the central region, which is watertightly connected to the buoy at the outer ring. The inner ring of the bearing is connected to a cover plate or is itself manufactured as such. This cover plate can therefore be rotated relative to the buoy.

[0012] The slewing ring, preferably a three-row roller slewing ring, is sealed against the ingress of seawater using special seals.

[0013] The base plate has a central hole through which the power cable is routed, sealing it from seawater. Holes are provided in the outer area of ​​the base plate for the anchoring elements, preferably wire ropes. The number depends on the permit requirements and the wind farm geometry. Typically, five anchoring elements are used, but three, four, and six anchoring elements are also not uncommon. For redundancy reasons, a larger number of anchoring elements can also be used. The anchoring elements are also firmly fixed in the base plate in the desired position.

[0014] The ground anchors are inserted into the waterbed at appropriate intervals around the desired location of the wind turbine, and the connecting elements, usually a chain attached to the anchor and the buoy section as a rope element, are laid to the center, the future location of the wind turbine. The buoy is then moved to this location and connected to the connecting elements. A flexible high-voltage underwater cable is also connected to the buoy. During this work, the buoy floats on the water.

[0015] Once the wind turbine is completed, it is towed to the buoy location by tugboats. The floating wind turbine emerges from the water in towed position. The wind turbine has a conical opening on the underside of the floating element at the front of the floating foundation. The opening's geometry is adapted to the outer contour of the buoy.

[0016] The slip ring body is located centrally above this conical opening for later connection to the power cable. This is located in the water-free space above the waterline during transport.

[0017] To connect the buoy to the floating wind turbine, upon reaching the desired position, the buoy is flooded with seawater by opening a (bottom) valve using a remote control. The water tank is lowered to a predetermined depth. The wind turbine is towed with a positioning system with its bottom opening precisely over the submerged buoy. Appropriate sensors must be provided. The ballast water is then expelled using compressed air stored, for example, in a compressed air tank. The buoy is slowly ascended again and inserted into the conical opening in the foundation of the wind turbine. A permanent connection between the buoy and the wind turbine is then established using screws or similar.

[0018] To protect the buoy from damage, it can be padded with rubber mats or similar materials. After connecting the buoy and the system, the space between them is drained of any entrained water and drained. The connection is sealed to permanently keep water out of this space. The power cable is then connected to the slip ring assembly above it, and the connection to the grid is established. The system is then lowered to its operating depth and put into operation.

[0019] For returning the turbine to port for repairs, the process is reversed and can be configured as desired. For major repairs, lengthy, dangerous, and costly offshore operations are thus eliminated. Instead, two small, inexpensive dinghies can be used to transport the turbine to port, while simultaneously connecting a new or refurbished turbine to the vacated buoy for power generation. This is not possible with current floating offshore systems.

[0020] According to the invention, a unit is provided with a floating wind turbine having a floating foundation and a floating mooring buoy which can be connected to the floating foundation of the floating wind turbine and which has at least one anchoring means for anchoring the mooring buoy to the bottom of the water, wherein the floating foundation of the floating wind turbine has a recess for receiving the mooring buoy, wherein the recess of the mooring buoy is accessible from the underside of the foundation and is at least partially complementary to the outer contour of the mooring buoy.

[0021] Exact positioning and a form fit between the wind turbine and the mooring buoy, which is fundamentally advantageous for the transmission of forces, is achieved in particular if the mooring buoy is conical (and the recess is complementary to it).

[0022] According to the invention, the mooring buoy itself is formed from a conically tapered wall forming a hollow cylinder and a base plate closing the hollow cylinder on one side, wherein the wall of the mooring buoy is rotatably mounted relative to the base plate.

[0023] In particular, a first passage arranged centrally in the base plate is provided for the passage of a submarine cable, wherein at least one further second passage arranged in the base plate for the passage of the anchoring means is advantageous.

[0024] To enable the buoy to descend and ascend, a ballast water tank is provided in the mooring buoy, preferably in its wall. This tank can be filled with water from the surrounding area and purged using compressed air. Appropriate aids in the form of pumps and valves must be provided for this purpose. These aids are preferably operated via radio remote control from the tug or wind turbine.

[0025] Furthermore, it is preferably provided that the recess of the floating foundation and the mooring buoy inserted into the recess form an enclosed space. The advantage of this design is that it creates a dry space that is also accessible for maintenance work and in which the electrical components of the wind turbine are protected from moisture.

[0026] In particular, means for tensioning the anchoring devices and / or the submarine cable must also be provided.

[0027] Finally, the mooring buoy may have shock-absorbing elements arranged on its outer circumference to help prevent damage to the mooring buoy or the wind turbine when connected to the wind turbine.

[0028] The following steps are required to install a unit equipped with a ballast water tank: Anchoring a mooring buoy (with connecting elements) at the predetermined location for installing the floating wind turbine, attaching a submarine cable to the mooring buoy, lowering the mooring buoy by flooding the ballast water tank, positioning the recess of the floating foundation of the floating wind turbine above the mooring buoy, inserting the mooring buoy into the recess of the floating foundation by surfacing the mooring buoy by emptying the ballast water tank, and connecting the submarine cable to the floating wind turbine by means of a slip ring.

[0029] The preferred method is to lower the wind turbine together with the mooring buoy by flooding ballast water tanks provided in the foundation of the wind turbine.

[0030] The invention will be explained in more detail with reference to a particularly preferred embodiment shown in the accompanying drawings. They show: Fig. 1 is a perspective view of a particularly preferred mooring buoy according to the invention; Fig. 2 is a perspective view of the particularly preferred mooring buoy according to the invention with a cover closing the buoy compartment; Fig. 3 is a sectional view of the mooring buoy; Fig. 4 is a perspective view of a particularly preferred unit according to the invention during installation at an offshore location; Fig. 5 is a side view of the Fig. 4 shown unit; Fig. 6 a detailed side view of the lowered mooring buoy in the area of ​​the recess of the foundation of the floating wind turbine; Fig. 7 a side view of the wind turbine positioned above the mooring buoy; and Fig. 8 the wind turbine connected to the mooring buoy.

[0031] Fig. 1 shows a perspective view of a particularly preferred mooring buoy according to the invention.

[0032] The mooring buoy 20 has an upwardly tapered, conical outer contour formed by the wall 22. The base of the cone is formed by a base plate 24, with the mooring buoy 20 being connected to the waterbed by means of several anchoring means 30. Furthermore, the mooring buoy 20 is connected to a submarine cable 40, thus providing the mooring buoy 20 as the sole anchor point for a floating wind turbine.

[0033] Also shown is a means 70 supported on the upper edge of the wall 22 for tensioning the anchoring means 30 and / or the submarine cable 40, so that the buoy 20 can be anchored precisely during its installation.

[0034] Fig. 2 shows a perspective view of the particularly preferred mooring buoy 20 according to the invention with a cover 50 closing the space formed by the wall 22 and the base plate 24.

[0035] A float 60 is attached to the cover 50, which - as Fig. 6 shows - can serve as a guide when inserting buoy 20 into the foundation of the wind turbine.

[0036] The cover 50 ensures that no water can penetrate into the space provided in the buoy 20. This is particularly important when the recess in the foundation of the wind turbine is accessible from below the foundation and the buoy 20 must be lowered. The geometry of the cover 50 allows it to be removed after the buoy 20 has been inserted into the foundation of the wind turbine.

[0037] The cover 50 thus seals the buoy 20 after it has been anchored until it is connected to the wind turbine. The free end of the pre-installed submarine cable 40 is thus protected from corrosion during this period.

[0038] In the Fig. 3 In the sectional view shown, it can be seen that the wall 22 of the mooring buoy 20 is mounted so as to be rotatable about its base plate 24. The anchoring means 30 and the submarine cable 40, however, are connected to the base plate 24 in a rotationally fixed manner by means of passages 26, 28 provided in the base plate 24. The submarine cable 40 is guided centrally through the base plate 24 in order to minimize any load acting on the submarine cable 40 caused by a rotational movement of the buoy 20. A seal 34 provided on the upper fastening flange of the buoy 20 seals the recess 12 of the foundation against the seawater after the buoy 20 is connected to the wind turbine 100 (see also Fig. 8 ).

[0039] Due to the relative rotatability of wall 22 to base plate 24, the wind turbine can rotate about the base plate 24 fixed by means of the anchoring element 30 via the rotary joint 32 when the wall 22 and the foundation of the wind turbine are fixed.

[0040] To install such a trained unit, as Fig. 4 shown - a floating wind turbine 100 is pulled by its foundation 10 by two tugs S1, S2 to the installation site in such a way that the tugs S1, S2 take the mooring buoy 20 between them and the mooring buoy 20 and foundation 10 of the floating wind turbine 100 approach each other.

[0041] In Fig. 5 It can be seen that both the mooring buoy 20 and the floating foundation 10 of the wind turbine 100 float on the water surface in this process step.

[0042] In order for the mooring buoy 20 to be inserted into the recess 12 of the foundation 10, which is accessible from below the waterline, the buoy 20 must be lowered. This is achieved, in particular, by absorbing ballast water. The buoy 20 preferably has a ballast water tank arranged in the wall 22, in particular a ring-shaped one. This can be flooded with seawater by remotely controlling a seacock.

[0043] Fig. 6 shows a side view of the lowered mooring buoy 20 in the area of ​​the foundation 10 of the floating wind turbine 100, wherein the float 60 arranged on the buoy 20 can also be seen.

[0044] The float 60 can be used as a guide structure for inserting the buoy 20 into the recess 12, e.g., by being grasped and guided. Alternatively or additionally, the float 60 can also be designed such that it can be actively or passively located to facilitate the positioning of the wind turbine 100 relative to the buoy 20.

[0045] About the Fig. 7 In the position shown in side view, the mooring buoy 20 is finally moved into the Fig. 8 shown position, in which the mooring buoy 20 is connected to the wind turbine 100 after being inserted into the recess 12 of the foundation 10.

[0046] It can also be seen that the submarine cable 40 is connected to the slip ring body 110, which is arranged above the bushing 26 arranged centrally in the bottom 24 of the buoy 20.

[0047] The wind turbine 10 is therefore basically ready for operation.

[0048] For stability reasons, the foundation 10 is lowered by flooding ballast water tanks provided in the foundation 10, so that the influence of waves is less than with a wind turbine 100 floating on the water surface.

Claims

1. A unit comprising - a floating wind turbine (100) having a floating foundation (10) and - a floating mooring buoy (20) connectable to the floating foundation (10) of the floating wind turbine (100), having at least one anchoring means (30) for anchoring the mooring buoy (20) on the floor of the body of water, wherein - the floating foundation (10) of the floating wind turbine (100) has a recess (12) for accommodating the mooring buoy (20), wherein the recess (12) of the mooring buoy (20) is accessible from the lower side of the foundation (10) and is formed at least partially complementary to the outer contour of the mooring buoy (20) characterized in that the mooring buoy (20) is formed from a conically tapering wall (22), which forms a hollow cylinder, and a base plate (24) closing the hollow cylinder on one side, the wall (22) being mounted rotatably relative to the base plate (24).

2. Unit according to claim 1, characterized by a first feedthrough (26), arranged centrally in the base plate (24), for feeding through an undersea cable (40).

3. Unit according to any one of the preceding claims, characterized by at least one second feedthrough (28), arranged in the base plate (24), for feeding through the anchoring means (30).

4. nit according to any one of the preceding claims, characterized in that the mooring buoy (20) has at least one ballast water tank.

5. Unit according to any one of the preceding claims, characterized in that the recess (12) of the floating foundation (10) and the mooring buoy (20) inserted into the recess (12) form a closed space.

6. Unit according to any one of the preceding claims, characterized in that means for tensioning the anchoring means (30) and / or the undersea cable (40) are provided in the mooring buoy (20).

7. Unit according to any one of the preceding claims, characterized by shock absorbing elements arranged on the outer circumference of the mooring buoy (20).