Floating energy dissipation device for offshore wind turbine support structures and method of installation thereof

Abstract

The application discloses a floating energy dissipation device for offshore wind turbine support structure and a mounting method thereof, which comprises a floating body, an elastic connecting piece, a tension leg and a suction type mooring anchor, the top of the floating body is connected with the inner wall of the support structure through the elastic connecting piece, the mechanical movement energy of the support structure is transmitted to the floating body through the elastic connecting piece, the bottom of the floating body is connected with the suction type mooring anchor through the tension leg, the suction type mooring anchor is fixed to the sea bed mud surface and extends downward, and the tension leg type floating body composed of the floating body and the tension leg bears and dissipates the mechanical movement energy transmitted by the support structure. The application utilizes the restoring force of the tension leg type floating body moored to the sea bed, provides the elastic energy dissipation effect of the support structure through the horizontal elastic connection with the support structure, further reduces the load borne by the support structure, has low comprehensive cost, has economic feasibility and low engineering risk.

Description

Technical Field

[0001] This invention relates to the technical field of load reduction for offshore wind turbine support structures, and in particular to a floating energy dissipation device for offshore wind turbine support structures and its installation method. Background Technology

[0002] Offshore wind power is an important component of the development of clean new energy sources, and its development is receiving increasing attention. However, due to the harsh marine environment, the construction cost of offshore wind power remains high, and the industry goal of achieving grid parity for offshore wind power is not yet achievable.

[0003] Cost reduction in offshore wind power inevitably requires multifaceted efforts and innovation from the entire industry to fully explore the cost reduction potential of each component. The support structure of monopile-mounted offshore wind turbines accounts for approximately 23% of the total cost of wind farm development projects. Furthermore, the investment scale of most domestic offshore wind farm development projects often reaches billions of RMB or even higher. Therefore, reducing the cost of the support structure will significantly lower the cost per kilowatt-hour of offshore wind power development, bringing it closer to the goal of grid parity.

[0004] Wind turbines capture wind energy, typically converting it into electricity at an efficiency of about 40% to 50%. The majority of the remaining energy is absorbed by the support structure and ultimately transferred to the seabed. Therefore, the support structure must possess significant rigidity and strength, which is one of the fundamental reasons for its high cost. As offshore wind power gradually expands into deeper waters and wind turbines become larger, the overall dimensions of the support structure have also increased to meet design requirements. The design diameter of the piles beneath the seabed mud surface has grown from the initial six or seven meters to eleven or twelve meters, with the wall thickness approaching one hundred millimeters. The diameter of the upper tower of the support structure has also generally reached about seven meters, with a wall thickness of several tens of millimeters. The total steel consumption of the support structure is close to three thousand tons.

[0005] The input control conditions for the design of the dimensions of the support structure generally include the fatigue load, ultimate load, and lower limit requirement of the modal frequency. The lower limit requirement of the modal frequency is proposed in order to control the magnitude of the fatigue load. Therefore, how to reduce the stiffness and strength requirements of the support structure and reduce the load on the support structure is the key to reducing the geometric dimensions of the support structure and thus reducing the amount of steel used. Developing energy-consuming devices that can be used to reduce the load on the support structure of offshore wind turbines will be one of the directions for cost reduction.

[0006] Traditional methods of dissipating energy in support structures typically involve installing dampers at the top of the structure. The most common type of damper is the pendulum, as seen in the rooftops of skyscrapers on land. However, offshore wind turbine support structures are generally slender structures with a narrowed top diameter, resulting in extremely limited internal space—often between 4 and 5 meters in diameter. This severely restricts the pendulum's movement, leading to less than ideal performance and compromising both cost-effectiveness and safety. Furthermore, while newer types of dampers have emerged in recent years, such as eddy current dampers and bucket dampers, detailed design analysis has shown that their effectiveness also falls short of economic viability, hindering large-scale adoption. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a floating energy dissipation device for the support structure of offshore wind turbines. Utilizing the unique conditions of the ocean, a floating energy dissipation device is installed inside the support structure. The floating body and tension cable are combined to form a tension leg floating body. By utilizing the restoring force of the tension leg floating body moored on the seabed and through a horizontal elastic connection with the support structure, an elastic energy dissipation effect is provided for the support structure, thereby reducing the load on the support structure. The overall cost is low, it is economically feasible, and the engineering risk is low.

[0008] Another object of the present invention is to provide an installation method for a floating energy dissipation device for a support structure of an offshore wind turbine.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A floating energy dissipation device for an offshore wind turbine support structure is disclosed. The floating energy dissipation device is disposed inside the support structure and includes a float, an elastic connector, a tension cable, and a suction mooring anchor. The top of the float is connected to the inner wall of the support structure through the elastic connector, and the mechanical kinetic energy of the support structure is transferred to the float through the elastic connector. The bottom of the float is connected to the suction mooring anchor through the tension cable. The suction mooring anchor is fixed to the seabed mud surface and extends downward. The tension leg-type float, composed of the float and the tension cable, bears and dissipates the mechanical kinetic energy transferred by the support structure.

[0011] Furthermore, the floating body includes a main body section, a transition section, and a connecting section connected sequentially from bottom to top. The main body section has a cylindrical structure, the diameter of which is determined according to the diameter of the supporting structure. It has multiple hollow chambers inside. The lower part of the main body section is submerged below the sea surface, and its draft can provide sufficient buoyancy and pretension for the tension cable. The diameter of the connecting section is smaller than that of the main body section, and its top is connected to the inner wall of the supporting structure through an elastic connector.

[0012] Furthermore, the float is a concrete float, a steel float, or a steel-concrete composite float.

[0013] Furthermore, the elastic connecting element is a spring or a hydraulic rod, and there are multiple of them, which are radially distributed around the outer periphery of the float.

[0014] Furthermore, the elastic connector is horizontally positioned.

[0015] Furthermore, the suction mooring anchor is a cylindrical structure with an open top and a closed bottom, and its top is provided with a lug for connecting with a tension cable.

[0016] Furthermore, the suction-type mooring anchor is made of steel.

[0017] Furthermore, there are multiple tension cables, which are arranged circumferentially between the suction mooring anchor and the float.

[0018] Furthermore, the tension cable is any one or more of the following: anchor chain, fiber cable, mooring chain, and wire rope.

[0019] Another objective of this invention is achieved through the following technical solution:

[0020] A method for installing a floating energy dissipation device for an offshore wind turbine support structure includes the following steps:

[0021] S1. The suction mooring anchor is hoisted according to the set offshore construction method and lowered to the preset positioning point on the seabed mud surface. The suction mooring anchor is penetrated to the preset depth below the seabed mud surface by the set negative pressure method.

[0022] S2. Tow the float into position and inject a set amount of ballast water into the hollow compartment of the float to make the float sink to the preset depth.

[0023] S3. Connect and install the tension cable between the float and the suction mooring anchor. Connect the upper and lower parts of the tension cable with a temporary shackle to temporarily fix the float.

[0024] S4. Drive the single piles of the support structure into place according to the established offshore construction piling procedures.

[0025] S5. Hoist the wind turbine generator set into place according to the established offshore wind power construction hoisting procedure, and connect the wind turbine generator set to the support structure with bolts;

[0026] S6. Release the temporary shackle connection of the tension cable and gradually discharge the set amount of ballast water from the hollow compartment of the float. Adjust the load to make the float rise to the surface and finally rise to the draft depth that meets the buoyancy and tension cable pretension requirements.

[0027] S7. Inside the support structure, measure the gap between the outer wall of the top of the float and the inner wall of the support structure. Based on the size of the gap, process the elastic connector. Inside the support structure, connect the top of the float to the inner wall of the support structure using the elastic connector to complete the installation.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. This invention utilizes the unique conditions of the ocean to install a floating energy dissipation device inside the support structure. The float and tension cable are combined to form a tension leg float. By utilizing the restoring force of the tension leg float moored on the seabed and elastically connected to the support structure horizontally, the elastic energy dissipation effect of the support structure is provided, thereby reducing the load on the support structure. The overall cost is low, it is economically feasible, and the engineering risk is low.

[0030] 2. The floating body of the present invention is located inside the monopile support structure and will not be affected by external wind, waves and currents at sea. Therefore, it does not require excessive rigidity, strength and dimensional accuracy. Under the premise that the volume meets the buoyancy, low-cost materials and construction methods can be used.

[0031] 3. The suction mooring anchor used in this invention is a conventional offshore suction foundation, which is convenient and quick to install and will not increase the load on the original monopile support structure. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of the floating energy-consuming device of the present invention.

[0033] Figure 2 This is a top view of the floating energy-consuming device of the present invention.

[0034] Figure 3 This is a schematic diagram of the structure of the float of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Example 1:

[0037] like Figures 1 to 3As shown, this embodiment provides a floating energy dissipation device for the support structure of an offshore wind turbine. The floating energy dissipation device is disposed inside the support structure 2 and includes a float 3, an elastic connector 4, a tension cable 5, and a suction mooring anchor 6. The top of the float 3 is connected to the inner wall of the support structure 2 through the elastic connector 4. The mechanical motion energy of the support structure 2 is transmitted to the float 3 through the elastic connector 4. The bottom of the float 3 is connected to the suction mooring anchor 6 through the tension cable 5. The suction mooring anchor 6 is fixed to the seabed mud surface and extends downward. The tension leg float, composed of the float 3 and the tension cable 5, bears and dissipates the mechanical motion energy transmitted by the support structure 2.

[0038] Specifically, the float 3 can be a concrete float 3, a steel float 3, or a reinforced concrete float 3. The float 3 includes a main body section 301, a transition section 302, and a connecting section 303 connected sequentially from bottom to top. The main body section has a cylindrical structure, the diameter of which is determined according to the diameter of the supporting structure 2. It has multiple hollow chambers inside. The lower part of the main body section is submerged below the sea surface, and the underwater part needs to be designed with a sufficient draft to provide sufficient buoyancy and pretension of the tension cable 5. The connecting section is a slender upright with a diameter smaller than that of the main body section. Its top is connected to the inner wall of the supporting structure 2 through an elastic connector 4.

[0039] In this embodiment, the float 3 is located inside the support structure 2 and will not be affected by external winds, waves and currents at sea. Therefore, it does not require excessive rigidity, strength and dimensional accuracy. Under the premise that the volume meets the buoyancy requirements, low-cost materials and construction methods can be used.

[0040] Specifically, the elastic connector 4 is a spring or a hydraulic rod, and there are multiple of them, preferably more than eight, which are radially distributed on the outer periphery of the float 3, and each elastic connector 4 is horizontally arranged.

[0041] Specifically, the suction mooring anchor 6 is a cylindrical structure with an open top and a closed bottom. Its top is equipped with a lug for connecting with the tension cable 5. The diameter of the cylinder must be greater than 6 meters and smaller than the inner diameter of the support structure 2 at the seabed mud surface. The specific values ​​of the cylinder diameter and the design depth of the mud penetration are designed according to the seabed soil conditions and the tension requirements of the tension cable 5.

[0042] Furthermore, the suction mooring anchor 6 is made of steel.

[0043] Specifically, there are multiple tension cables 5, preferably 6 to 8 or more. These tension cables 5 are arranged circumferentially between the suction mooring anchor 6 and the float 3, and the tension cables 5 must have sufficient pretension during installation.

[0044] Furthermore, the tension cable 5 can be any one or more combinations of anchor chain, fiber cable, mooring chain, and wire rope.

[0045] Offshore wind turbine support structures are typically slender with a narrower top, resulting in extremely limited internal space, often between 4 and 5 meters in diameter. Adding a damper weight significantly restricts the pendulum's movement, leading to less than ideal performance. This invention's floating energy dissipation device utilizes the buoyancy of seawater and the tension of the tension cable to dissipate energy, thus avoiding the need for a damper weight on top of the support structure. Such a heavy damper weight is detrimental to load reduction and poses safety concerns. Furthermore, the elastic connector can be positioned lower as needed, allowing the tension leg-type float to have greater movement space and improved energy dissipation.

[0046] Example 2:

[0047] This embodiment provides an installation method for a floating energy dissipation device used in the support structure of an offshore wind turbine, including the following steps:

[0048] S1. The suction mooring anchor is a conventional offshore suction foundation. The suction mooring anchor is hoisted according to the set offshore construction method and lowered to the preset positioning point on the seabed mud surface. The suction mooring anchor is penetrated to the preset depth below the seabed mud surface by the set negative pressure method.

[0049] S2. Tow the float into position and inject a set amount of ballast water into the hollow chamber of the float to make the float sink to a preset depth, that is, the top of the float is lower than the single pile driving point of the supporting structure.

[0050] S3. Connect and install the tension cable between the float and the suction mooring anchor. Connect the upper and lower parts of the tension cable by means of temporary shackles, that is, only use a section of the tension cable length to temporarily fix the float.

[0051] S4. Drive the single piles of the support structure into place according to the established offshore construction piling procedures.

[0052] S5. Hoist the wind turbine generator set into place according to the established offshore wind power construction hoisting procedure, and connect the wind turbine generator set to the support structure with bolts;

[0053] S6. Release the temporary shackle connection of the tension cable and gradually discharge the set amount of ballast water from the hollow compartment of the float. Through precise load adjustment, the float will rise to a draft depth that meets the buoyancy and tension cable pretension requirements.

[0054] S7. Inside the support structure, accurately measure the gap between the outer wall of the top of the float and the inner wall of the support structure. Based on the size of the gap, i.e., based on the final installation accuracy of the support structure, customize and precisely process the elastic connector to meet the actual usage requirements. Inside the support structure, connect the top of the float to the inner wall of the support structure through the elastic connector to complete the installation.

[0055] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A floating energy dissipation device for the support structure of offshore wind turbines, characterized in that: The floating energy dissipation device is installed inside the support structure and includes a float, elastic connectors, tension cables, and a suction mooring anchor. The top of the float is connected to the inner wall of the support structure via the elastic connectors, and the mechanical kinetic energy of the support structure is transferred to the float via the elastic connectors. The bottom of the float is connected to the suction mooring anchor via the tension cables. The float includes a main body section, a transition section, and a connecting section connected sequentially from bottom to top. The main body section has a cylindrical structure, and its diameter is determined according to the diameter of the support structure. It has multiple hollow compartments inside. The lower part of the main body section is submerged below the sea surface, and its draft can provide sufficient buoyancy and pretension of the tension cables. The diameter of the connecting section is smaller than that of the main body section, and its top is connected to the inner wall of the support structure via the elastic connectors. The suction mooring anchor is fixed to the seabed mud surface and extends downward. The tension leg float, composed of the float and the tension cables, bears and dissipates the mechanical kinetic energy transferred by the support structure.

2. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 1, characterized in that: The float can be a concrete float, a steel float, or a steel-concrete composite float.

3. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 1, characterized in that: The elastic connecting element is a spring or a hydraulic rod, and there are multiple of them, which are radially distributed around the outer periphery of the float.

4. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 3, characterized in that: The elastic connector is horizontally positioned.

5. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 1, characterized in that: The suction mooring anchor is a cylindrical structure with an open top and a closed bottom, and its top is provided with a lug for connecting with a tension cable.

6. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 5, characterized in that: The suction-type mooring anchor is made of steel.

7. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 1, characterized in that: The tension cables are multiple and are arranged circumferentially between the suction mooring anchor and the float.

8. The floating energy dissipation device for the support structure of offshore wind turbines according to claim 7, characterized in that: The tension cable is any one or more of the following: anchor chain, fiber cable, mooring chain, and wire rope.

9. A method for installing a floating energy dissipation device for a support structure of an offshore wind turbine as described in any one of claims 1 to 8, characterized in that, Including the following steps: S1. The suction mooring anchor is hoisted according to the set offshore construction method and lowered to the preset positioning point on the seabed mud surface. The suction mooring anchor is penetrated to the preset depth below the seabed mud surface by the set negative pressure method. S2. Tow the float into position and inject a set amount of ballast water into the hollow chamber of the float to make the float sink to the preset depth. S3. Connect and install the tension cable between the float and the suction mooring anchor. Connect the upper and lower parts of the tension cable with a temporary shackle to temporarily fix the float. S4. Drive the single piles of the support structure into place according to the established offshore construction piling procedures. S5. Hoist the wind turbine generator set into place according to the established offshore wind power construction hoisting procedure, and connect the wind turbine generator set to the support structure with bolts; S6. Release the temporary shackle connection of the tension cable and gradually discharge the set amount of ballast water from the hollow compartment of the float. Adjust the load to make the float rise to the surface and finally rise to the draft depth that meets the buoyancy and tension cable pretension requirements. S7. Inside the support structure, measure the gap between the outer wall of the top of the float and the inner wall of the support structure. Based on the size of the gap, process the elastic connector. Inside the support structure, connect the top of the float to the inner wall of the support structure using the elastic connector to complete the installation.

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