Semi-submersible floating offshore wind turbine floating foundation and its application in offshore wind turbines

Abstract

This divisional application relates to a floating foundation for a semi-submersible floating offshore wind turbine and its application in an offshore wind turbine, belonging to the field of marine engineering technology. In order to solve the problem of reducing the stress concentration of the sharp vertical connection between the column and the bottom buoy, the key points are that it includes a column, a bottom buoy and a connecting buoy, and the connecting buoy is connected to the bottom surface of the column, and the bottom surface of the column is transitionally connected to the first end of the bottom buoy arranged in a horizontal plane parallel to the axis in a non-vertical connection manner, which has the effect of significantly reducing the cost of steel and reducing the stress concentration at the connection between the column and the bottom buoy.

Description

[0001] This application is a divisional application with application date 2024-01-27, application number 202410117106.3, and invention name: A low-cost large-scale semi-submersible floating offshore wind turbine. Technical Field

[0002] The present invention belongs to the field of marine engineering technology, and in particular relates to a low-cost, large-scale semi-submersible floating offshore wind turbine and a design solution thereof. Technical Background

[0003] The offshore wind power industry is facing a major shift from nearshore to offshore, as well as the challenge of transitioning from experimental prototypes to commercial-scale deployment. Floating offshore wind power technology has become a key innovation in exploiting deep-sea wind resources. This technology uses a floating foundation to support turbines, which are connected to the seabed via a mooring system. Unrestricted by water depth and independent of complex seabed topography and geology, it significantly expands the applicable sea area and available wind energy resources. As a cutting-edge model for deep-sea wind energy development, floating offshore wind turbines not only hold great promise but have also become a research focus. To fully utilize wind energy resources in medium-depth areas, the development of semi-submersible floating wind turbines is trending towards larger sizes. However, the complex foundation designs and diverse forms of current semi-submersible platforms have led to a lack of standardization in the construction, assembly, and installation processes. Furthermore, construction costs, particularly the use of steel, remain high, hindering the commercialization of these platforms.

[0004] For existing semi-submersible floating platforms, the unit steel consumption is generally positively correlated with platform stability and wind turbine capacity. Greater steel consumption generally results in greater platform stability and a correspondingly higher wind turbine capacity. This results in limited installation areas for large floating platforms, significant steel consumption, and extremely high steel costs. To ensure stability, existing semi-submersible floating platforms often utilize rectangular pontoons, which are vertically connected to columns, resulting in a higher unit steel consumption. However, this vertical connection between the pontoons and columns increases stress concentration at the connection points. Typically, those skilled in the art increase the amount of steel used at these vertical connections to reduce stress and improve the stability of the floating platform. As mentioned above, large floating platforms use a significant amount of steel, ensuring stability and enabling high wind turbine capacity. However, this significant increase in steel consumption leads to a sharp increase in costs, limiting the development of large floating platforms. Reducing unit steel consumption and increasing wind turbine capacity while ensuring platform stability has long been a pressing issue in the field. Summary of the Invention

[0005] In order to solve the problem of optimizing the steel configuration for large-scale semi-submersible floating offshore wind turbines, significantly reduce the steel cost, and at the same time achieve a considerable displacement and ease of assembly, especially to meet the platform stability requirements. According to some specific embodiments of the present application, the semi-submersible floating offshore wind turbines include:

[0006] Wind turbines;

[0007] a tower structure, wherein the upper end of the tower structure supports the wind turbine generator set;

[0008] a floating foundation connected to the lower end of the tower structure to support the tower structure;

[0009] A mooring system is connected to the floating foundation.

[0010] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the floating foundation comprises:

[0011] The columns include a first column, a second column, and a third column. The axes of the first column, the second column, and the third column are perpendicular to the horizontal plane and parallel to each other. The three columns are located at the three vertices of an equilateral triangle formed by the columns, and a column is provided at each vertex.

[0012] a main column connected to the lower end of the tower structure, wherein the axis of the main column is perpendicular to the horizontal plane and parallel to the axes of the columns;

[0013] an upper cross brace, the upper cross brace comprising a first upper cross brace, a second upper cross brace, and a third upper cross brace, the first upper cross brace being arranged between an outer circumferential surface of the first column facing the main column and an outer circumferential surface of the main column, the second upper cross brace being arranged between an outer circumferential surface of the second column facing the main column and an outer circumferential surface of the main column, and the third upper cross brace being arranged between an outer circumferential surface of the third column facing the main column and an outer circumferential surface of the main column;

[0014] A main bottom buoy, wherein the upper side surface of the main bottom buoy transitions from the first end of the main bottom buoy to the second end of the main bottom buoy through the cylindrical curved surface to the main bottom buoy bearing plane, and the main column is vertically arranged on the main bottom buoy bearing plane near the second end of the main bottom buoy;

[0015] The side bottom buoy has an upper side surface that transitions from the first end and the second end of the side bottom buoy to the middle of the side bottom buoy, from a cylindrical curved surface to a side bottom buoy bearing plane. The main bottom buoy and the axis of the side bottom buoy are arranged parallel to a horizontal plane and are at the same horizontal position. The second end of the main bottom buoy is horizontally and vertically connected to the middle of the side bottom buoy.

[0016] The connecting buoys include a first connecting buoy, a second connecting buoy, and a third connecting buoy, wherein the first connecting buoy is connected to the bottom surface of the first column, and the bottom surface of the first column is transitionally connected to the first end of the main bottom buoy arranged in a horizontal plane parallel to the axis in a non-perpendicular connection manner; the second connecting buoy is connected to the bottom surface of the second column, and the second column is transitionally connected to the first end of the side bottom buoy arranged in a horizontal plane parallel to the axis in a non-perpendicular connection manner; the third connecting buoy is connected to the bottom surface of the third column, and the third column is transitionally connected to the second end of the side bottom buoy arranged in a horizontal plane parallel to the axis in a non-perpendicular connection manner;

[0017] Wherein, the upright column, the main column, the upper cross brace, the main bottom buoy, the side bottom buoy and the connecting buoy are hollow cylinders.

[0018] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the bottom surface of the first column is inclined, the upper and lower end surfaces of the first connecting buoy are inclined, the end surface of the first end of the main bottom buoy is inclined, the upper end surface of the first connecting buoy and the connecting surface of the first column form a 45° angle in the horizontal direction, and the lower end surface of the first connecting buoy and the end surface of the first end of the main bottom buoy form a 45° angle in the horizontal direction;

[0019] The bottom surface of the second column is inclined, the upper and lower end surfaces of the second connecting buoy are inclined, the end surface of the first end of the side bottom buoy is inclined, the upper end surface of the second connecting buoy and the connecting surface of the second column form a 45° angle in the horizontal direction, and the lower end surface of the second connecting buoy and the end surface of the first end of the side bottom buoy form a 45° angle in the horizontal direction;

[0020] The bottom surface of the third column is tilted, the upper and lower end surfaces of the third connecting buoy are tilted, the end surface of the second end of the side bottom buoy is tilted, the upper end surface of the third connecting buoy and the connecting surface of the third column form a 45° angle in the horizontal direction, and the lower end surface of the third connecting buoy and the end surface of the second end of the side bottom buoy form a 45° angle in the horizontal direction.

[0021] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the upper side surface of the main bottom buoy transitions from a cylindrical curved surface at a horizontal inclination angle of 45° at the first end of the main bottom buoy to a main bottom buoy bearing plane toward the second end of the main bottom buoy;

[0022] The upper side surface of the side bottom buoy transitions from the first end and the second end of the side bottom buoy to the middle of the side bottom buoy at a 45° horizontal inclination angle from the cylindrical curved surface to the side bottom buoy bearing plane.

[0023] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the side bottom buoy transitions from a cylindrical curved surface to a main bottom buoy bearing plane at a horizontal inclination angle of 45° toward the second end of the main bottom buoy;

[0024] The upper side surface of the side bottom buoy transitions from the first end and the second end of the side bottom buoy to the middle of the side bottom buoy at a 45° horizontal inclination angle from the cylindrical curved surface to the side bottom buoy bearing plane.

[0025] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the first upper cross brace and the main bottom buoy bearing plane are arranged relatively parallel to each other at different horizontal plane heights;

[0026] The second upper cross brace and the side bottom buoy bearing plane connected to one side of the second column are arranged relatively parallel at different horizontal heights;

[0027] The third upper cross brace and the side bottom buoy bearing plane connected to one side of the third column are relatively parallel and arranged at different horizontal plane heights.

[0028] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the columns are at the same horizontal position and at the same height.

[0029] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the mooring system includes an anchor chain, which includes a first anchor chain and a second anchor chain. The bottom of the column is connected to the two anchor chains respectively, and two anchor chains are arranged on each column with the center of the column as the vertex at an angle of 10°.

[0030] According to some specific embodiments of the semi-submersible floating offshore wind turbine of the present application, the main column is arranged at the midpoint of the equilateral triangle surrounded by the vertical columns and is arranged on the bearing plane of the main bottom buoy.

[0031] According to some specific embodiments of the present application, the semi-submersible floating offshore wind turbine also includes a connecting rib, which is arranged between the cylinder body of the adjacent main bottom buoy and the side bottom buoy. The connecting rib is formed into an isosceles right triangle, one side of which is connected to the main bottom buoy, and the other side is connected to the side bottom buoy.

[0032] The beneficial effects of this invention are as follows: The floating foundation's structural design, including the columns, main columns, pontoons, and connecting pontoons, adopts a T-shaped layout, with the columns arranged in an equilateral triangle. This reduces steel usage compared to existing technologies. Furthermore, this structure optimizes performance under varying marine loads, mitigating the impact of waves and currents on the foundation's motion. Furthermore, the floating foundation's main structure adopts a hollow cylindrical shape, significantly reducing the amount of steel required while maintaining a displacement volume roughly equivalent to that of a traditional semi-submersible floating foundation.

[0033] On this basis, the present invention unifies the outer diameter dimensions of the adapter columns, connecting pontoons and bottom pontoons and designs them into a cylindrical structure. This not only allows the use of mature single-pile fixed wind turbine construction methods, but also achieves standardization of construction methods and processes, thereby significantly reducing construction costs.

[0034] On this basis, the present invention essentially employs a design that increases the curvature of the connecting buoys when connecting the columns to the bottom buoys. Specifically, the connecting buoys are designed to connect at an obtuse 135° angle between the columns and the bottom buoys. Compared to a sharp vertical connection between the columns and the bottom buoys, this reduces stress and improves platform stability. Specifically, based on the principle that a straight line is the shortest distance between two points, the connecting buoys are directly connected between the columns and the bottom buoys. Compared to the curved connection methods used for vertical connections, this connection method of the present invention not only reduces steel consumption, but also effectively avoids the stress concentration and improper connection transition problems associated with traditional vertical connection designs, thereby improving the safety and service life of the entire floating foundation structure. Compared to existing methods that address stress concentration caused by vertical connections by increasing steel consumption at the connection to reduce stress and improve platform stability, the above-mentioned method of the present invention overcomes technical biases, reduces steel consumption, and solves stress concentration problems while maintaining considerable platform stability.

[0035] Based on this, the present invention constructs the main bottom pontoon's bearing surface by cutting a horizontal incision of a specific depth into the top of the main bottom pontoon to create a flat, horizontal bearing surface. This improvement allows the main column to be installed on the pontoon in a more stable and precise manner. This design significantly simplifies the complexity of main column installation and facilitates contact surface preparation, ensuring a quality and stable installation. Compared to directly installing the main column on the uncut curved surface of the circular bottom pontoon, the present invention is technically easier to implement. Based on the principle of minimum surface area, by removing a portion of the curved surface at the top of the circular pontoon and replacing it with a flat surface, not only does this significantly reduce the unnecessary displacement volume of the bottom pontoon, but it also reduces the surface area of ​​the pontoon. Furthermore, this reduced surface area also reduces the amount of steel used in the manufacture of the bottom pontoon. Furthermore, according to the principle of shear stress distribution, a rectangular cross-section has a greater advantage in shear area than a circular cross-section, meaning that a rectangular cross-section exhibits stronger performance when subjected to shear forces. By cutting the top of the main bottom pontoon to create a horizontal bearing surface, the top shape changes from an arc to a horizontal one, effectively increasing the shear area. Therefore, the design of the main bottom pontoon bearing surface not only improves the overall stability of the structure, but also enhances the shear resistance, thereby improving the performance and safety factor of the entire pontoon structure, and reducing the amount of steel used in the main bottom pontoon.

[0036] On this basis, each column of the present invention is equipped with two mooring ropes (anchor chains), that is, the bottom of the column is connected to two anchor chains respectively, and two anchor chains are arranged on each column with the center of the column as the vertex at an angle of 10°. This method not only enhances the positioning ability of the structure, but also provides higher safety protection for the floating foundation.

[0037] As described above, the present invention is applicable to large-scale semi-submersible floating offshore wind turbines. By optimizing the steel usage, it significantly reduces steel costs while simultaneously achieving a comparable displacement and ease of assembly. In particular, it also meets platform stability requirements and increases wind turbine load capacity. Clearly, through the aforementioned means, the present invention achieves significant reductions in steel usage and increases wind turbine load capacity while ensuring platform stability. For relevant experimental data, please refer to the experimental section of the detailed implementation plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 3D illustration of a low-cost, large-scale semi-submersible floating offshore wind turbine design.

[0039] Figure 2 Front view of the low-cost, large-scale semi-submersible floating offshore wind turbine design.

[0040] Figure 3 Side view of a low-cost, large-scale semi-submersible floating offshore wind turbine design.

[0041] Figure 4A top view of the low-cost, large-scale semi-submersible floating offshore wind turbine design.

[0042] Figure 5 Time distribution of free decay of longitudinal surge.

[0043] Figure 6 Time history distribution of sway free decay.

[0044] Figure 7 Time history distribution of heave free decay.

[0045] Figure 8 Roll free decay time history distribution.

[0046] Figure 9 Pitch free decay time history distribution.

[0047] Figure 10 Time history distribution of free decay of bow roll.

[0048] Figure 11 Von-mise stress distribution of the floating body of the present invention when the wave amplitude is 2.5m and the wave period is 10.8s, (a) 0° wave direction angle working condition, (b) 180° wave direction angle working condition.

[0049] Figure 12 Shear stress distribution of the floating body of the present invention when the wave amplitude is 2.5m and the wave period is 10.8s, (a) 0° wave direction angle working condition, (b) 180° wave direction angle working condition.

[0050] In the figure: 1. Upper cross brace, 2. Vertical column, 3. Main column, 4. Main bottom pontoon, 5. Side bottom pontoon, 6. Main bottom pontoon bearing plane, 7. Side bottom pontoon bearing plane, 8. Bottom pontoon bearing transition surface, 9. Connecting pontoon, 10. Tower structure, 11. Wind turbine, 12. Connecting ribs, 13. Mooring system. DETAILED DESCRIPTION

[0051] The embodiments of the present application are described in detail below with reference to the accompanying drawings, examples of which are shown in the accompanying drawings, wherein the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions.

[0052] Example 1: Figure 1-4 As shown, a semi-submersible floating offshore wind turbine includes a wind turbine 11, a tower structure 9, a floating foundation, and a mooring system 13. The upper end of the tower structure 9 supports the wind turbine 11. The floating foundation is connected to the lower end of the tower structure 9 to support the tower structure 9. The mooring system 13 is connected to the floating foundation.

[0053] The floating foundation includes columns 2, main columns 3, upper cross braces 1, main bottom buoys 4, side bottom buoys 5, and connecting buoys 9.

[0054] The columns 2 include a first column, a second column and a third column. The axes of the first column, the second column and the third column are arranged perpendicular to the horizontal plane and are parallel to each other. The three columns 2 are located at the three vertices of the equilateral triangle surrounded by the columns 2, and a column 2 is arranged at each vertex position.

[0055] The main column 3 is connected to the lower end of the tower structure 9 , and the axis of the main column 3 is perpendicular to the horizontal plane and parallel to the axes of the columns 2 .

[0056] The upper cross brace 1 includes a first upper cross brace, a second upper cross brace and a third upper cross brace. The first upper cross brace is arranged between the outer peripheral surface of the first column facing the main column 3 and the outer peripheral surface of the main column 3. The second upper cross brace is arranged between the outer peripheral surface of the second column facing the main column 3 and the outer peripheral surface of the main column 3. The third upper cross brace is arranged between the outer peripheral surface of the third column facing the main column 3 and the outer peripheral surface of the main column 3.

[0057] The upper side surface of the main bottom buoy 4 transitions from the first end of the main bottom buoy 4 to the main bottom buoy bearing plane 6 by the cylindrical curved surface to the second end of the main bottom buoy 4, and the main column 3 is vertically arranged on the main bottom buoy bearing plane 6 near the second end of the main bottom buoy 4.

[0058] The upper side surface of the side bottom buoy 5 transitions from the first end and the second end of the side bottom buoy 5 to the middle of the side bottom buoy 5, and becomes the side bottom buoy bearing plane. The axes of the main bottom buoy 4 and the side bottom buoy 5 are arranged parallel to the horizontal plane and are in the same horizontal position. The second end of the main bottom buoy 4 is horizontally and vertically connected to the middle position of the side bottom buoy 5.

[0059] The connecting buoy 9 includes a first connecting buoy, a second connecting buoy and a third connecting buoy. The first connecting buoy is connected to the bottom surface of the first column, and the bottom surface of the first column is transitionally connected to the first end of the main bottom buoy 4 set in the horizontal plane parallel to the axis in a non-vertical connection manner. The second connecting buoy is connected to the bottom surface of the second column, and the second column is transitionally connected to the first end of the side bottom buoy 5 set in the horizontal plane parallel to the axis in a non-vertical connection manner. The third connecting buoy is connected to the bottom surface of the third column, and the third column is transitionally connected to the second end of the side bottom buoy 5 set in the horizontal plane parallel to the axis in a non-vertical connection manner.

[0060] The upright columns 2, main columns 3, upper cross braces 1, main bottom pontoons 4, side bottom pontoons 5, and connecting pontoons 9 are hollow cylinders. The hollow cylindrical shape of the pontoons improves drainage and reduces steel usage. The present invention relates to an improved bottom pontoon design, based on the geometric advantages of the isoperimetric theorem. The isoperimetric theorem states that among all closed curves of the same perimeter, a circle can enclose the largest area. Similarly, in three-dimensional space, when the surface area remains constant, a sphere can enclose the largest volume. Because the cylindrical structure is the closest to the shape of a sphere among all cylindrical shapes, it can enclose a larger volume with the same surface area. Based on this principle, the present invention proposes a hollow cylindrical pontoon design. Compared to traditional rectangular pontoons, cylindrical pontoons have a smaller surface area while maintaining the same displacement volume. This design optimization not only means that less steel can be used in the pontoon construction, thereby reducing costs, but also ensures sufficient displacement volume. In general, the improvement in the buoy design of the present invention significantly enhances the stability and economy of ships, offshore platforms and other aquatic structures, and has broad application prospects and important practical value.

[0061] In one embodiment, the bottom surface of the first column is tilted, the upper and lower end surfaces of the first connecting buoy are tilted, the end surface of the first end of the main bottom buoy 4 is tilted, the upper end surface of the first connecting buoy forms a 45° angle with the connecting surface of the first column in the horizontal direction, and the lower end surface of the first connecting buoy forms a 45° angle with the end surface of the first end of the main bottom buoy 4 in the horizontal direction. The bottom surface of the second column is tilted, the upper and lower end surfaces of the second connecting buoy are tilted, the end surface of the first end of the side bottom buoy 5 is tilted, the upper end surface of the second connecting buoy forms a 45° angle with the connecting surface of the second column in the horizontal direction, and the lower end surface of the second connecting buoy forms a 45° angle with the end surface of the first end of the side bottom buoy 5 in the horizontal direction. The bottom surface of the third column is inclined, the upper and lower end surfaces of the third connecting buoy are inclined, and the end surface of the second end of the side bottom buoy 5 is inclined. The upper end surface of the third connecting buoy forms a 45° horizontal angle with the connection surface of the third column, and the lower end surface of the third connecting buoy forms a 45° horizontal angle with the end surface of the second end of the side bottom buoy 5. In this intermediate solution, the connecting buoy 9 can reduce steel usage and stress. Conventional semi-submersible floating wind turbine columns are directly connected to the bottom buoy at a 90° right angle, but this sharp connection angle can lead to stress concentration. The present invention optimizes the connection design by introducing the connecting buoy 9 as an intermediate structure between the column 2 and the main bottom buoy 4 and the side bottom buoy 5. The connecting buoy 9 is designed to connect to the column and bottom buoy at an obtuse angle of 135°. This design conforms to the principle of smooth stress distribution and effectively reduces stress concentration. Compared with traditional designs, the use of the connecting buoy in the present invention not only improves the stress distribution of the structure but also optimizes the steel usage. Specifically, the axis of the connecting tube intersects with the axes of the columns and pontoons at an obtuse angle of 135°. The extended area of ​​these axes forms an isosceles triangle, with the connecting tube of the present invention acting as the base of the triangle; the columns and bottom pontoons of the conventional connection method acting as the two sides of the triangle. Based on the principle of the relationship between the sides of a triangle, where the sum of the two sides is greater than the length of the base, this design can reduce the amount of steel used in the floating wind turbine while still meeting the structural strength requirements, thereby reducing costs.

[0062] In one embodiment, the upper side surface of the main bottom buoy 4 transitions from a cylindrical curved surface at a 45° horizontal inclination angle from the first end of the main bottom buoy 4 to a main bottom buoy bearing plane 6 toward the second end of the main bottom buoy. The upper side surface of the side bottom buoy 5 transitions from a cylindrical curved surface at a 45° horizontal inclination angle from the first end and the second end of the side bottom buoy 5 to the middle of the side bottom buoy 5 to a side bottom buoy bearing plane. In the present invention, the main bottom buoy bearing plane 6 is constructed by forming a flat horizontal bearing plane by making a horizontal cut of a specific depth on the top of the main bottom buoy 4. This improvement allows the main column to be installed on the buoy in a more stable and precise manner. By adopting this design, the complexity of installing the main column is significantly simplified, and the processing of the contact surface becomes easier, ensuring the quality and stability of the installation. Compared with directly installing the main column on the uncut circular bottom buoy curved surface, the design proposed by the present invention is technically easier to implement. Based on the minimum surface principle, by removing part of the curved surface at the top of the circular pontoon and replacing it with a flat surface, not only is the unnecessary displacement volume of the bottom pontoon significantly reduced, but the surface area of ​​the pontoon is also reduced. In addition, the design optimization that reduces the surface area can also reduce the amount of steel used to manufacture the bottom pontoon. Furthermore, according to the principle of shear stress distribution, the rectangular cross-section has an advantage over the circular cross-section in terms of shear area, which means that when subjected to shear force, the rectangular cross-section can exhibit stronger performance. By cutting the top of the main bottom pontoon into a horizontal bearing surface, the shape of its top is changed from an arc to a horizontal surface, effectively increasing the shear area. Therefore, the design of the main bottom pontoon bearing plane 6 not only improves the overall stability of the structure, but also enhances the shear resistance, thereby improving the performance and safety factor of the entire pontoon structure, and reducing the amount of steel used in the main bottom pontoon 4. The principle of the side bottom pontoon bearing plane 7 is the same as that of the main bottom pontoon bearing plane 6. The side bottom pontoon bearing plane 7 can also provide an installation platform for the future expansion of the functions of floating wind turbines.

[0063] In one embodiment, the first upper cross brace is relatively parallel to the main bottom buoy bearing plane 6 at different horizontal plane heights. The second upper cross brace is relatively parallel to the side bottom buoy bearing plane connected to the second column at different horizontal plane heights. The third upper cross brace is relatively parallel to the side bottom buoy bearing plane connected to the third column at different horizontal plane heights.

[0064] In one embodiment, the pillars 2 are at the same horizontal position and the same height.

[0065] In one embodiment, the mooring system 13 includes anchor chains, including a first anchor chain and a second anchor chain. The bottoms of the columns 2 are connected to the two anchor chains, with two anchor chains positioned on each column 2 at 10° intervals, with the center of the column 2 as the vertex. This approach not only enhances the structure's positioning capabilities but also provides greater security for the floating foundation.

[0066] In one embodiment, the main column 3 is positioned at the midpoint of the equilateral triangle formed by the uprights 2 and is located on the main bottom buoy bearing plane 6. This approach improves stability: The central position helps align the structure's center of gravity with its center of buoyancy, reducing tilt and sway caused by wind loads or waves, and enhancing overall structural stability. It evenly distributes loads: Through the centralized tower layout, forces generated by wind turbine operation and pressures induced by environmental conditions are more evenly distributed across the triangular platform, reducing structural stress points and extending its service life. It optimizes symmetry: The central position ensures symmetrical mass distribution on the platform in the horizontal plane, which helps maintain the structure's dynamic balance under wind or wave action. It improves dynamic response: Compared to other positions, the central position helps mitigate the adverse dynamic effects of waves and currents, particularly in irregular wave conditions, improving the structure's responsiveness and adaptability. It also simplifies installation and maintenance: The central position of the tower simplifies the layout of cables and pipelines, reduces wiring length, and thus reduces the difficulty and cost of installation and maintenance. Able to improve power generation efficiency: The central position of the tower helps reduce the interference of the floating structure on the wind flow, helping to maximize the efficiency of the wind rotor.

[0067] In one embodiment, the semi-submersible floating offshore wind turbine further includes a connecting rib 12, which is disposed between the cylinder of the adjacent main bottom buoy 4 and the side bottom buoy 5. The connecting rib is shaped as an isosceles right triangle, one side of which is connected to the main bottom buoy 4 and the other side of which is connected to the side bottom buoy 5. Thus, the connecting rib 12 is located on both sides of the connection between the main bottom buoy 4 and the side bottom buoy 5, and the connecting rib is connected to the main bottom buoy 4 and the side bottom buoy 5 at a 45-degree angle. The connecting rib 12 serves to strengthen the connection between the main bottom buoy 4 and the side bottom buoy 5, avoiding stress concentration problems caused by overly sharp connections.

[0068] As described above, the present invention discloses a low-cost, large-scale, semi-submersible, floating offshore wind turbine design suitable for use in the field of marine engineering technology. This design is intended to provide a support platform for wind turbines of 15 MW or higher. The large-scale semi-submersible, floating offshore wind turbine system described herein primarily comprises key components such as a floating foundation, a mooring system, a wind turbine, and a tower structure. The floating foundation, the core of the invention, consists of an upper cross brace, columns, a main column, connecting buoys, and a bottom buoy, all of which have a circular cross-section. This design significantly reduces the amount of steel required to construct the semi-submersible floating foundation while ensuring sufficient displacement volume. To address the stress concentration problem caused by the lack of a transitional connection between the columns and the bottom buoy, the present invention utilizes a steeply curved, inclined connecting buoy, significantly enhancing the structural safety and extending its service life. The bottom buoy is designed with a horizontal bearing surface, which not only facilitates the placement of the main column, tower, and wind turbine, but also effectively improves its resistance to shear forces. The size of the horizontal bearing surface can be flexibly adjusted to accommodate towers and wind turbines of different sizes and models, increasing the adaptability and versatility of the design. The columns, connecting buoys and bottom buoys have a uniform outer diameter and all adopt a cylindrical structure, which allows for the use of standardized construction methods and processes and can utilize existing mature single-pile fixed wind turbine construction technology, thereby significantly reducing construction costs. In addition, the number of connection points of the main structures is reduced, facilitating the modular assembly of floating offshore wind turbines. The floating foundation of the present invention has a T-shaped structural layout, with three columns distributed in an equilateral triangle. This configuration can reduce the headwind contact area between the floating foundation and waves and currents under different marine environmental load conditions, thereby reducing the adverse effects of environmental loads on the movement performance of the floating foundation. In addition, the present invention adopts a 2×3 mooring system, that is, each column is equipped with two anchor chains, which further improves the positioning capability of the platform, making it more suitable for deployment under the specific conditions of my country's medium-depth waters. In summary, this invention provides a low-cost, large-scale semi-submersible floating wind turbine design solution with the characteristics of simple structure, low cost, high safety, and strong adaptability, contributing a valuable technical solution to the commercial development of my country's floating offshore wind power field.

[0069] Example 2: The present invention proposes an innovative, low-cost, large-scale semi-submersible floating wind power platform design. Compared with traditional designs, this solution adopts a large-curvature inclined connecting buoy to connect the three columns and the bottom buoy, thereby reducing the problem of stress concentration. In addition, the columns, bottom buoys and connecting buoys all adopt a unified circular cross-section design, which simplifies the construction process. The T-shaped distribution of the bottom buoy and the equilateral triangle layout of the three columns reduce the number of structural connection points, which not only enhances the modular assembly capability of the floating offshore wind turbine, but also effectively reduces the contact area of ​​the floating foundation with the marine environment load. The 2×3 mooring system design adopted, that is, each column is equipped with two mooring ropes, which enhances the positioning capability of the platform. Overall, the solution of the present invention shows obvious advantages in reducing the amount of steel used in the floating foundation structure, reducing construction and assembly costs, and improving safety, providing a feasible solution for the large-scale and commercial development of semi-submersible floating wind power platforms.

[0070] This invention aims to propose a low-cost, large-scale, semi-submersible, floating offshore wind turbine design suitable for medium-depth areas in the East China and South China Seas. Compared to traditional semi-submersible floating wind turbine foundations, this design significantly reduces the steel requirement. While ensuring structural safety, the structure simplifies the construction process and facilitates modular assembly. This invention provides an economically viable design blueprint for promoting the commercial development of floating offshore wind farms in my country.

[0071] The present invention proposes a low-cost, large-scale, semi-submersible floating offshore wind turbine design comprising a floating foundation, a mooring system 13, a wind turbine 11, and a tower structure 10. The floating foundation comprises an upper cross brace 1, columns 2, a main column 3, a main bottom buoy 4, a side bottom buoy 5, a main bottom buoy bearing plane 6, a side bottom buoy bearing plane 7, a bottom buoy bearing transition surface 8, and a connecting buoy 9. The upper cross brace 1 is horizontally arranged, with the main column at its center of gravity, and is connected to each of the three columns 2. The columns 2 are connected to the main bottom buoy 4 and the side bottom buoy 5 via connecting buoys 9. The main bottom buoy 4 and the side bottom buoy have horizontal main bottom buoy bearing planes 6 and 7 at their tops, respectively. Their ends feature bottom buoy bearing transition surfaces 8, which gently transition from the cylindrical surface to 6 and 7 at a 45° horizontal inclination to prevent stress concentration. The main bottom buoy 4 is connected to the main column 3 via the upper main bearing plane 6. The tower structure 10 is supported above the main column 3. The upper part of the tower structure 10 carries a wind turbine 11. The bottoms of the columns 2 are respectively connected to the mooring system 12. Two anchor chains are distributed on each column at an angle of 10°, with the column center as the vertex. The main bottom buoy 4 is located in the middle of the inner side of the side bottom buoy 5 and is connected to the side bottom buoy 5 in a 90° T-shape. The three columns are distributed at the vertices of the three sides of the equilateral triangle with the center of the main column as the center. The connecting buoy makes an angle of 45° with the horizontal direction. The upper part of the connecting buoy is respectively connected to the three columns, and the lower part is respectively connected to the main bottom buoy 4 and the side bottom buoy 5. The main bottom buoy bearing plane 6 and the side bottom buoy bearing plane 7 coincide and are connected in the horizontal direction.

[0072] The low-cost, large-scale, semi-submersible floating offshore wind turbine design comprises a floating foundation structure comprising three horizontally oriented upper cross braces 1, three vertically oriented columns 2, a vertically oriented main column 3, three connecting buoys 9 with axes at 45° angles to the horizontal, a main bottom buoy 4, a side bottom buoy 5, three bottom buoy load-bearing transition surfaces 8 at 45° angles to the horizontal, a main bottom buoy load-bearing plane 6, and a side bottom buoy load-bearing plane 7. The upper surface of the connecting buoy 9 connects to the columns 2 at a 45° horizontal angle, while the lower surface of the connecting buoy 9 connects to the ends of the main bottom buoy 4 and the side bottom buoy 5 at a 45° horizontal angle.

[0073] The floating foundation structure of this invention utilizes a fully cylindrical main structure. This design significantly reduces the amount of steel required while maintaining the same displacement volume as traditional semi-submersible floating foundations. By standardizing the outer diameters of the columns, connecting buoys, and bottom buoys, and designing them as cylindrical structures, this not only allows for the use of established monopile-fixed wind turbine construction methods, but also standardizes construction methods and processes, significantly reducing construction costs. A unique, highly curved, inclined connecting buoy design connects the columns to the bottom buoys, effectively avoiding the stress concentration and improper connection transitions common in traditional designs, significantly improving the safety and service life of the entire floating foundation structure. Furthermore, the floating foundation adopts a T-shaped layout with columns arranged in an equilateral triangle, optimizing its performance under varying marine loads and reducing the impact of waves and currents on foundation movement compared to traditional designs. To further enhance the platform's stability, a 2×3 mooring system has been designed, with two mooring lines per column. This approach not only enhances the structure's positioning capabilities but also provides greater safety for the floating foundation.

[0074] Overall, the design concept of this invention is simple and reliable. Compared with traditional floating offshore wind turbines, it significantly reduces steel usage, simplifies the construction process, facilitates modular assembly, and significantly improves safety and positioning capabilities. These features make this invention a promising and efficient design solution for the commercialization and development of floating offshore wind power in China.

[0075] Experimental example:

[0076] Table 1 Natural period of low-cost large-scale semi-submersible floating offshore wind turbine

[0077] Type of exercise Natural period unit Wandering 143.222 Second swaying 161.125 Second Dangling 18.681 Second Roll 31.439 Second pitch 32.225 Second Bow 161.125 Second

[0078] Table 2 Typical natural periods of floating foundations for semi-submersible floating wind turbines according to DNV-RP-0286

[0079]

[0080]

[0081] Table 3 Comparison of unit steel consumption of domestic floating wind turbines

[0082] Floating foundation name Unit steel consumption unit Carrying fan capacity Three Gorges "Leading" 790.91 Tons / MW 5.5 MW Haizhuang "Fuyao" 677.42 Tons / MW 6.2 MW CNOOC "Guanlan" 510.34 Tons / MW 7.25 MW "T-SEMI" proposed by this invention 236.26 Tons / MW 17 MW

[0083] Table: The inherent period of the low-cost, large-scale semi-submersible floating offshore wind turbine design proposed in this invention meets the requirements of DNV-RP-0286. The new semi-submersible floating foundation proposed in this invention has a significant advantage in reducing steel consumption compared to existing semi-submersible floating foundations in my country.

[0084] Table 3 shows that the unit steel consumption of current domestic floating wind turbines remains high. The floating wind turbine proposed in this invention uses 236.26 tons of steel per MW, a reduction of 70% to 53.7% compared to current domestic floating wind turbines. Furthermore, the floating wind turbine proposed in this invention supports a wind turbine capacity of 17 MW, a significant improvement over current domestic floating wind turbines.

[0085] The experimental data of the main bottom buoy bearing plane 6, the side bottom buoy bearing plane 7, the connecting buoy 9, and the connecting rib 12 of the present invention can reduce stress:

[0086] pass Figure 11 The Von-mise stress analysis of the floating structure of the present invention is presented, and it can be observed that the Von-mise stress of the floating structure of the present invention under various working conditions is uniformly distributed on the main bottom buoy bearing plane 6 and the side bottom buoy bearing plane 7. The distribution range of stress values ​​is relatively narrow, indicating the efficiency and rationality of the structural design in stress distribution. The connecting buoy 9 designed in the structure plays a key role in alleviating stress concentration at the connection between the column and the bottom buoy, which is confirmed by the fact that there is no significant stress concentration at the connection between the column and the bottom buoy. The stress value at the bottom buoy bearing transition surface 8 is relatively low, which indicates that the transition surface 8 has played its intended function in smoothing the structural stress distribution. In addition, according to the stress distribution, it can be seen that the connecting rib 12 effectively enhances the stability of the connection between the main bottom buoy 4 and the side bottom buoy 5, preventing the occurrence of stress concentration that may be harmful to the integrity of the structure.

[0087] Figure 12 The shear stress analysis of the float of the present invention further confirms the rationality of the structural design. Under various working conditions, the shear stress is mainly concentrated in the main bottom buoy bearing plane 6 and the side bottom buoy bearing plane 7, and also shows a smaller stress value range, which means that the entire float structure maintains good mechanical properties under the action of shear force. The reinforcement effect of the connecting ribs 12 ensures that there is no adverse shear stress concentration at the connection point between the main bottom buoy 4 and the side bottom buoy 5, thereby improving the structural integrity and durability of the float. In general, through reasonable design and layout, the new float not only shows excellent uniformity in Von-mise stress distribution, but also reflects the superior performance of the structure in the distribution of shear stress. These design considerations play a vital role in improving structural stability and durability, so that the new float of this invention has significant competitive advantages in practical applications.

[0088] The experimental data on the stability of the floating foundation of the present invention illustrate that: In the present invention, the vibration amplitude control principle is an important theoretical basis for evaluating the stability of floating structures. According to this principle, floating structures with longer natural periods can avoid most of the wave period, which helps to improve the motion stability of the structure under the action of waves and can effectively reduce the risk of violent movement and instability caused by wave dynamics. In the present invention, Figure 5-10 The results of free decay numerical simulation tests of a low-cost, large-scale, semi-submersible, floating offshore wind turbine under still water conditions are presented. Post-processing and analysis of the test results yielded Table 1, which clearly presents the natural period data for the floating wind turbine structure involved in this invention.

[0089] Table 2 provides typical reference values ​​of the natural period of the floating foundation of a semi-submersible floating wind turbine established in accordance with the DNV-RP-0286 specification. Through comparative analysis, the natural periods of the floating wind turbine in the present invention in the longitudinal, vertical and pitch directions are all within the range shown in Table 2. This fact shows that the dynamic response of the design of the present invention in the above directions is consistent with the industry standard. In particular, the natural period of the present invention in the bow roll direction is greater than the bow roll period range recommended in the DNV-RP-0286 specification. According to the vibration amplitude control principle, this shows that in the bow roll direction, the floating structure designed by the present invention will be insensitive to the influence of long-period waves, which is conducive to improving the motion stability in this direction.

[0090] In summary, through comparison with industry standards and theoretical analysis, we conclude that the low-cost, large-scale, semi-submersible floating offshore wind turbine proposed in this invention meets or exceeds design requirements for initial stability in all major design directions. This conclusion not only demonstrates the uniqueness of this invention's design but also its potential technical advantages in ensuring structural stability. This demonstrates that this invention significantly reduces steel usage while maintaining platform stability.

[0091] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0092] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0093] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0094] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0095] In the present invention, the term "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and subsequent associated objects are in an "or" relationship. "At least one" means one or more; "at least one of A and B" is similar to "A and / or B", describing the association relationship of associated objects, indicating that three relationships may exist. For example, at least one of A and B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0096] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0097] The above description is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A semi-submersible floating offshore wind turbine floating foundation, characterized in that: include pillars; bottom buoys; A connecting buoy is connected to the bottom surface of the column, and the bottom surface of the column is transitionally connected to one end of a bottom buoy arranged on a horizontal plane parallel to the axis in a non-vertical connection manner; The bottom buoys include a main bottom buoy and a side bottom buoy; The upper side surface of the main bottom buoy transitions from the first end of the main bottom buoy to the main bottom buoy bearing plane through the cylindrical curved surface to the second end of the main bottom buoy, and the column is vertically arranged on the main bottom buoy bearing plane near the second end of the main bottom buoy; The upper side surface of the side bottom buoy transitions from the first end and the second end of the side bottom buoy to the middle of the side bottom buoy to form a side bottom buoy bearing plane, and the axes of the main bottom buoy and the side bottom buoy are arranged parallel to the horizontal plane and are in the same horizontal position; The columns include a first column, a second column and a third column, the axes of the first column, the second column and the third column are arranged perpendicular to the horizontal plane and parallel to each other, and the three columns are located at the three vertices of the equilateral triangle surrounded by the columns, with one column arranged at each vertex; The connecting buoys include a first connecting buoy, a second connecting buoy, and a third connecting buoy. The first connecting buoy is connected to the bottom surface of the first column, and the bottom surface of the first column is transitionally connected to the first end of the main bottom buoy arranged in a horizontal plane parallel to the axis in a non-perpendicular connection manner. The second connecting buoy is connected to the bottom surface of the second column, and the second column is transitionally connected to the first end of the side bottom buoy arranged in a horizontal plane parallel to the axis in a non-perpendicular connection manner. The third connecting buoy is connected to the bottom surface of the third column, and the third column is transitionally connected to the second end of the side bottom buoy arranged in a horizontal plane parallel to the axis in a non-perpendicular connection manner. The bottom surface of the first column is inclined, the upper and lower end surfaces of the first connecting buoy are inclined, the end surface of the first end of the main bottom buoy is inclined, the upper end surface of the first connecting buoy and the connecting surface of the first column form a 45° angle in the horizontal direction, and the lower end surface of the first connecting buoy and the end surface of the first end of the main bottom buoy form a 45° angle in the horizontal direction; The bottom surface of the second column is inclined, the upper and lower end surfaces of the second connecting buoy are inclined, the end surface of the first end of the side bottom buoy is inclined, the upper end surface of the second connecting buoy and the connecting surface of the second column form a 45° angle in the horizontal direction, and the lower end surface of the second connecting buoy and the end surface of the first end of the side bottom buoy form a 45° angle in the horizontal direction; The bottom surface of the third column is inclined, the upper and lower end surfaces of the third connecting buoy are inclined, the end surface of the second end of the side bottom buoy is inclined, the upper end surface of the third connecting buoy and the connecting surface of the third column form a 45° angle in the horizontal direction, and the lower end surface of the third connecting buoy and the end surface of the second end of the side bottom buoy form a 45° angle in the horizontal direction; The upper side surface of the main bottom buoy transitions from the first end of the main bottom buoy to the main bottom buoy bearing plane at a horizontal inclination angle of 45 degrees from the cylindrical curved surface to the second end of the main bottom buoy; The upper side surface of the side bottom buoy transitions from the first end and the second end of the side bottom buoy to the middle of the side bottom buoy at a 45° horizontal inclination angle from the cylindrical curved surface to the side bottom buoy bearing plane.

2. The semi-submersible floating offshore wind turbine floating foundation according to claim 1, characterized in that: Also includes A main column is connected to the lower end of the tower structure, the axis of the main column is arranged vertically to the horizontal plane, and is parallel to the axes of each column, wherein the second end of the main bottom buoy is horizontally and vertically connected to the middle position of the side bottom buoy.

3. The semi-submersible floating offshore wind turbine floating foundation according to claim 2 is characterized in that: Also includes The upper cross brace includes a first upper cross brace, a second upper cross brace and a third upper cross brace, the first upper cross brace is arranged between the outer peripheral surface of the first column facing the main column and the outer peripheral surface of the main column, the second upper cross brace is arranged between the outer peripheral surface of the second column facing the main column and the outer peripheral surface of the main column, and the third upper cross brace is arranged between the outer peripheral surface of the third column facing the main column and the outer peripheral surface of the main column.

4. The semi-submersible floating offshore wind turbine floating foundation according to claim 3 is characterized in that: The first upper cross brace and the main bottom buoy bearing plane are arranged relatively parallel to each other at different horizontal plane heights; The second upper cross brace and the side bottom buoy bearing plane connected to one side of the second column are arranged relatively parallel at different horizontal heights; The third upper cross brace and the side bottom buoy bearing plane connected to one side of the third column are relatively parallel and arranged at different horizontal plane heights.

5. The semi-submersible floating offshore wind turbine floating foundation according to claim 3 is characterized in that: The columns are at the same horizontal position and height, and the main column is arranged at the midpoint of the equilateral triangle formed by the columns and is arranged on the bearing plane of the main bottom buoy; The floating foundation further includes a connecting rib plate, which is arranged between the cylinder body of the adjacent main bottom buoy and the side bottom buoy, and the connecting rib is formed into an isosceles right triangle, one side of which is connected to the main bottom buoy and the other side is connected to the side bottom buoy; The upright column, the main column, the upper cross brace, the main bottom buoy, the side bottom buoy and the connecting buoy are hollow cylinders.

6. Use of the floating foundation according to any one of claims 1 to 5 in a semi-submersible floating offshore wind turbine.

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