Deep sea self-propelled self-elevating offshore wind power installation ship and design method thereof

Abstract

This invention provides a deep-sea self-propelled and self-elevating offshore wind power installation vessel and its design method. The installation vessel includes: a streamlined main hull design; an elevator system comprising legs, pile shoes, cofferdams and guide structures, a pile clamping chamber and pile clamping and lifting equipment; four sets of cofferdams and guide structures are respectively located at the four corners of the main hull; each cofferdam contains one leg; the upper part of the leg is connected to the pile clamping chamber and pile clamping and lifting equipment, and the bottom of the leg is connected to a pile shoe; the leg length is greater than or equal to 130m; the main crane has a lifting capacity of 1600t and a lifting height of 175m; the main crane is integrated with one of the elevator systems, utilizing the cofferdams and guide structures as the support structure for the crane; excluding the elevator equipment and the bow living area, the remaining deck surface of the main hull is designed as a flat surface, with a deck area greater than or equal to 3400m². 2 The deck is designed to withstand 15 t / m 2 The uniform load distribution is enhanced. This invention can reduce navigation resistance and improve navigation capacity; it also solves the problems of insufficient operating water depth and lifting capacity.

Description

Technical Field

[0001] This invention belongs to the technical field of offshore wind power installation vessels, and specifically relates to a deep-sea self-propelled and self-elevating offshore wind power installation vessel and its design method. Background Technology

[0002] In response to global warming, countries around the world have successively set carbon neutrality goals, and renewable energy has become the leading direction for the low-carbon energy transition of various countries. Among them, offshore wind power is of great significance and has obvious advantages: coastal areas are densely populated and have concentrated economic activities, resulting in high energy consumption. Nearby offshore wind power can reduce power transmission losses; offshore wind energy resources are huge and belong to renewable energy, which can support the clean energy transition of major energy-consuming countries.

[0003] With the deepening exploration of offshore wind energy resources and the need to reduce the impact on near-shore tourism and fisheries, the trend of offshore wind farms developing towards deeper waters and open seas is evident. Taking the "Guangdong Provincial Offshore Wind Power Development Plan (2017-2030)" as an example, 15 offshore wind farms are planned in shallow near-shore areas, with an installed capacity of over 9 million kilowatts; and 8 offshore wind farms are planned in deep near-shore areas, with an installed capacity of 57 million kilowatts. Early wind turbine installation vessels were converted from crane vessels or other engineering vessels, lacking leg anchors or having short legs, which could not meet the requirements for installing wind turbine equipment in deep water areas. To enable deep-water operations, extremely tall legs are needed, but the gantry cranes of major shipbuilding companies are shorter than the leg height, failing to meet the installation requirements.

[0004] Offshore installation faces harsh environments, limited installation time windows, and high demands for wind turbine installation efficiency. Wind turbines have numerous components and operate for extended periods in the complex and ever-changing marine environment, requiring high installation precision. Therefore, onshore assembly and commissioning of wind turbines, followed by overall installation at the wind farm, offers the best efficiency, safety, and stability, making it the optimal solution for future offshore wind power installations. Existing wind turbine installation vessels have limited leg height and insufficient operating depth, failing to meet the needs of installing wind turbines in deep water. They lack self-propulsion capabilities and have weak deck transport capacity, requiring reliance on other vessels for transportation, resulting in high installation costs. Furthermore, their insufficient lifting capacity cannot meet the requirements for the overall hoisting of wind turbine equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a deep-sea self-propelled and self-elevating offshore wind power installation vessel and its design method that can adapt to the current stage of offshore wind power installation.

[0006] The first aspect of this invention provides a deep-sea self-propelled and self-elevating offshore wind power installation vessel, comprising:

[0007] The main hull features a streamlined design.

[0008] The main hull is equipped with lifting equipment and a hoisting system;

[0009] Lifting equipment includes main lifting equipment and auxiliary lifting equipment;

[0010] The lifting system includes pile legs, pile shoes, cofferdams and guide structures, pile holding chambers and pile holding lifting equipment. Four sets of cofferdams and guide structures are respectively set at the four corners of the main hull. Each set of cofferdams is equipped with a pile leg. The pile holding chamber and pile holding lifting equipment are connected to the upper part of the pile leg, and the pile shoe is connected to the bottom of the pile leg. The length of the pile leg is greater than or equal to 130m.

[0011] The main hoisting equipment has a lifting capacity of 1600 t and a lifting height of 175 m. The main hoisting equipment is combined with one of the lifting systems, and the cofferdam and guide structure are used as the support structure for the hoisting equipment.

[0012] Aside from the elevators and the bow living quarters, the remaining deck space of the main hull is designed as a flat surface, with a deck area of ​​3400 m² or more. 2 The deck is designed to withstand 15 t / m 2 The uniformly distributed load setting is strengthened.

[0013] Optionally, the pile leg includes a truss-type pile leg, comprising three diagonal bracing tubes arranged in a triangle along the horizontal direction, and an inner horizontal tube connecting two adjacent diagonal bracing tubes.

[0014] The second aspect of this invention provides a design method for a deep-sea self-propelled and self-elevating offshore wind turbine installation vessel, used for designing the deep-sea self-propelled and self-elevating offshore wind turbine installation vessel of the first aspect of this invention. The design method includes:

[0015] Ship-shaped design and ultra-high leg design;

[0016] The ship design includes:

[0017] ① The main hull adopts a streamlined waterline design to reduce the ship's sailing resistance. Stability, freeboard, buoyancy, and wind load calculations are performed to ensure the ship's floating state and stability. With the appropriate power and auxiliary machinery, the ship is guaranteed to have a self-propelled capability of about 8 knots.

[0018] ② Two lifting systems are installed on both the port and starboard sides of the vessel, for a total of four lifting systems, consisting of pile legs, pile shoes, cofferdam and guide structure, pile holding chamber and pile holding lifting equipment;

[0019] ③ Determine the length of the pile legs according to the "Design Method for Ultra-High Piles" based on the required water depth to meet the requirements for deep-water operation capability;

[0020] ④ Based on the weight and size parameters of the current largest 20 MW wind power equipment and the requirements for integrated transportation and hoisting, the lifting capacity of the main crane is determined to be 1600 t and the lifting height is 175 m. The main crane is combined with one of the lifting systems, and the cofferdam and guide structure are used as the crane support structure to ensure the crane's lifting capacity, lifting height and working radius.

[0021] ⑤ Apart from the elevator equipment and the bow living area, the remaining deck surface adopts a flat design, with a deck area of ​​3400m². 2 The deck is designed to withstand 15 t / m 2 The uniform load setting is strengthened to ensure that the large deck has the capacity to transport and hoist two sets of 20 MW wind power equipment.

[0022] Optionally, two lifting systems are installed on both the port and starboard sides of the vessel, fore and aft, for a total of four lifting systems. These systems consist of pile legs, pile shoes, cofferdams and guide structures, pile clamping chambers, and pile clamping and lifting equipment, including:

[0023] a. In accordance with the requirements for controlling the ship's center of gravity, the lifting system must ensure that the ship and wind power equipment remain balanced during the lifting process;

[0024] b. The load on the lifting system is determined by the rated lifting load, the reaction force of the pile legs, the static and storm support load, the lifting speed, the design temperature, and the design life;

[0025] c. Determine the performance of the power unit and the shape of the rack based on the load.

[0026] Optionally, the ultra-high leg design includes:

[0027] By extending the legs, the operating water depth is increased. The extended legs are over 130 meters long, enabling the vessel to operate in water depths of up to 75 meters, meeting the installation needs of nearshore deep waters and even offshore areas. To meet the requirements for self-elevation and hoisting of wind power equipment and to ensure vessel safety, the vessel is equipped with four truss-type legs to share the weight of the vessel and the wind power equipment, as well as external wind loads. At the same time, a pre-set gripping shoe is installed at the lowest point of each leg, penetrating deep into the seabed mud layer to ensure stability during self-elevation operations.

[0028] Optionally, the method for calculating the length of the pile leg includes:

[0029] The formula for calculating the height of the pile leg is: Depth into the mud + Working water depth + Air gap + Shaft depth + Height of the pile chamber + Safety margin.

[0030] Considering the requirements for deep-water operations, the operating water depth can reach 75 m, and the remaining heights can be calculated based on the following conditions;

[0031] Piling depth: Based on the characteristics of the seabed foundation and the type of pile shoe, the depth of pile insertion into the mud is calculated and analyzed. The maximum depth of insertion into the mud in deep water is 15 m.

[0032] Air gap: Based on the hull shape and sea state characteristics, the air gap in the nearshore deep water area is set at a limit of 15 m;

[0033] Depth: 0–10 m, depending on the overall ship design;

[0034] Height of the pile gripping chamber: Based on performance calculations and the layout requirements of the pile gripping equipment, the height of the pile gripping chamber is 0 to 10 m.

[0035] Safety margin: 5 m;

[0036] Therefore, the length of the pile leg = 15 m + 75 m + 15 m + 10 m + 10 m + 5 m = 130 m.

[0037] Optionally, the strength design methods for ultra-high pile leg structures include:

[0038] The ultra-high legs allow for a larger span of the truss after the seabed and ship are lifted, and the strength requirements for the legs are higher. Therefore, a truss with a triangular cross section is used to improve structural stability, and the legs are supported on the inside by an inner horizontal tube to ensure their strength.

[0039] Optionally, the pile legs are made of high-strength and / or ultra-high-strength marine steel. The jacking rack is made of special steel with a yield strength of not less than 690 MPa, a tensile strength of not less than 770 MPa, and a hardness between 240 and 290 HB, with a thickness of approximately 180 mm. It must ensure that the longitudinal impact strength is not less than 69 J and the transverse impact strength is not less than 46 J during a V-notch impact test at -40°C. The main hull tube is divided into two semicircles, enclosing the rack. It is made of round tube with a yield strength of not less than 690 MPa and a tensile strength of not less than 770 MPa, ensuring that the longitudinal impact strength is not less than 69 J and the transverse impact strength is not less than 46 J during a V-notch impact test at -40°C. The diagonal bracing tube is made of round tube with a yield strength of not less than 555 MPa and a tensile strength of not less than 625 MPa, ensuring that the impact strength is not less than 55 J during a V-notch impact test at -40°C. The inner horizontal tube is made of steel with a yield strength of not less than 360 MPa and a tensile strength of not less than 460 MPa. A round tube with a strength of MPa is used, and the impact strength is guaranteed to be no less than 34J during the V-notch -40℃ impact test.

[0040] Alternatively, the installation methods for ultra-high pile legs include:

[0041] Each pile leg is divided into two parts: part one is 70 m long and part two is about 60 m long. A total of 8 pile leg parts are obtained from the 4 pile legs.

[0042] Inside the shipyard's dry dock, a large gantry crane was used to lift and install the components of the four pile legs, and to conduct pile lifting and lowering tests to ensure that all four pile legs could properly grip the pile and rise and fall.

[0043] When the ship is sailed to the waters outside the shipyard, the water depth must meet the operating depth requirements of large crane vessels.

[0044] Using ship-mounted pile-holding equipment, the pile leg components are lowered, with the top surface of the pile leg components about 1 m above the top of the pile-holding chamber, which facilitates subsequent construction. If necessary, in order to ensure this 1 m of welding space, the pile leg can be inserted into the seabed mud layer.

[0045] Using a crane vessel, component two of the four pile legs was hoisted onto component one in sequence. After component one and component two were aligned and fixed, welding was carried out at sea.

[0046] After the four components are welded together, the pile legs 1 through 4 will be installed.

[0047] Alternatively, if the crane vessel's performance is limited, the four legs can be disassembled into two parts and installed sequentially at sea.

[0048] The beneficial effects of this invention are as follows:

[0049] As can be seen from the above scheme, the embodiments of the present invention provide a deep-sea self-propelled and self-elevating offshore wind turbine installation vessel. The main hull has a streamlined design, which reduces navigation resistance and improves navigation capacity. The leg length is greater than or equal to 130m, solving the problem of limited leg height and insufficient operating water depth for wind turbine installation vessels. The main crane has a lifting capacity of 1600t and a lifting height of 175m, solving the problem of insufficient lifting capacity that cannot meet the overall lifting requirements of wind turbine equipment. Except for the lifting equipment and the bow living area, the remaining deck surface of the main hull adopts a planar design, with a deck area greater than or equal to 3400m². 2 The deck is designed to withstand 15 t / m 2 The enhanced uniform load setting solves the problems of weak deck transport capacity, the need to rely on other ships for transportation, and high installation costs. Attached Figure Description

[0050] Figure 1 A first-view structural schematic diagram of a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to an embodiment of the present invention;

[0051] Figure 2 This is a second-view structural diagram of a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to an embodiment of the present invention;

[0052] Figure 3 This diagram illustrates the structure of a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to an embodiment of the present invention.

[0053] Figure 4 This diagram illustrates the leg arrangement of a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to an embodiment of the present invention.

[0054] Figure 5 This is a side view of the pile leg of a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to an embodiment of the present invention;

[0055] Figure 6 This is a top view of the pile legs of a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to an embodiment of the present invention.

[0056] In the diagram, 1. Main crane equipment; 2. Main hull; 3. Auxiliary crane equipment; 4. Pile clamping chamber and pile clamping lifting equipment; 5. Cofferdam and guide structure; 6. Pile leg; 7. Diagonal brace pipe; 8. Pile shoe; 91. Outer main hull pipe; 92. Inner main hull pipe; 10. Rack; 11. Inner horizontal pipe. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0058] This invention aims to address the problems of early wind turbine installation vessels lacking self-propulsion or having weak self-propulsion capabilities, limited lifting capacity, and poor maneuverability, positioning performance, inability to operate in strong winds, and low efficiency, thus failing to meet new installation requirements. The invention provides a self-propelled, self-elevating deep-sea wind turbine installation vessel with deep-water operation capabilities, high lifting capacity, and a large deck cargo capacity. This vessel enables integrated transportation of offshore wind turbines from the dock base to deep-water areas, completes the installation of offshore wind power equipment of 20MW and below, and solves the installation challenges of its ultra-high legs.

[0059] See Figures 1 to 6 The first aspect of the present invention provides a deep-sea self-propelled and self-elevating offshore wind power installation vessel, comprising:

[0060] Main hull 2, which features a streamlined design;

[0061] The main hull 2 ​​is equipped with lifting equipment and a hoisting system;

[0062] The lifting equipment includes main lifting equipment 1 and auxiliary lifting equipment 3;

[0063] The lifting system includes pile legs 6, pile shoes 8, cofferdams and guide structures 5, pile holding chambers and pile holding lifting equipment 4. Four sets of cofferdams and guide structures 5 are respectively set at the four corners of the main hull 2. Each set of cofferdams is equipped with a pile leg 6. The pile leg 6 is connected to the pile holding chamber and pile holding lifting equipment 4 at the top and the pile shoe 8 is connected to the bottom of the pile leg 6. The length of the pile leg 6 is greater than or equal to 130m. The pile leg 6 is a truss type pile leg, including three diagonal bracing pipes 7 arranged in a triangle along the horizontal direction, and an inner horizontal pipe 11 connecting two adjacent diagonal bracing pipes 7.

[0064] The main hoisting equipment 1 has a lifting capacity of 1600 t and a lifting height of 175 m. The main hoisting equipment 1 is combined with one of the lifting systems and uses the cofferdam and guide structure 5 as the support structure for the hoisting equipment.

[0065] Aside from the elevators and the bow living quarters, the remaining deck area of ​​the main hull 2 ​​is designed as a flat surface, with a deck area of ​​3400 m² or more. 2 The deck is designed to withstand 15 t / m 2 The uniformly distributed load setting is strengthened.

[0066] The second aspect of this invention provides a design method for a deep-sea self-propelled and self-elevating offshore wind turbine installation vessel, used for designing the deep-sea self-propelled and self-elevating offshore wind turbine installation vessel of the first aspect of this invention. The design method includes:

[0067] The design features a hull shape and ultra-high leg design.

[0068] The ship design includes:

[0069] ① Combination Figure 1 and Figure 2 The main hull adopts a streamlined waterline design to reduce the ship's sailing resistance. Stability, freeboard, buoyancy, and wind load calculations are performed to ensure the ship's floating state and stability. With the appropriate power and auxiliary machinery, the ship is guaranteed to have a self-propulsion capability of about 8 knots.

[0070] ② Combination Figure 3 and Figure 4 The ship is equipped with two sets of lifting systems, one forward and one aft, on both the port and starboard sides, for a total of four lifting systems. These systems consist of pile legs 6, pile shoes 8, cofferdam and guide structure 5, pile holding chamber and pile holding lifting equipment 4.

[0071] a. In accordance with the requirements for controlling the ship's center of gravity, the lifting system must ensure that the ship and wind power equipment remain balanced during the lifting process;

[0072] b. The load on the lifting system is determined by the rated lifting load, pile leg reaction force, static and storm support load, lifting speed, design temperature, design life, etc.

[0073] c. Determine the performance of the power unit and the shape of the rack based on the load.

[0074] ③ Based on the required water depth, the length of leg 6 is determined according to the "Design Method for Ultra-High Legs" below to meet the requirements for deep-water operation capability;

[0075] ④ Based on the weight and size parameters of the current largest 20 MW wind power equipment and the requirements for integrated transportation and hoisting, the lifting capacity of the main crane is determined to be 1600 t and the lifting height is 175 m. The main crane is combined with one of the lifting systems, and the cofferdam and guide structure 5 are used as the crane support structure to ensure the crane's lifting capacity, lifting height and working radius.

[0076] ⑤ Apart from the elevator equipment and the bow living area, the remaining deck surface is designed as a flat surface, with a deck area of ​​approximately 3400 m². 2 The deck is designed to withstand 15 t / m 2 The uniform load setting is strengthened to ensure that the large deck has the capacity to transport and hoist two sets of 20 MW wind power equipment.

[0077] The design of the ultra-high pile legs 6 includes:

[0078] By extending the legs 6, the operating water depth is increased. The length of the extended legs 6 exceeds 130 meters, enabling the vessel to operate in water depths of up to 75 meters, meeting the installation needs of nearshore deep water areas and even offshore areas. In order to meet the requirements of self-elevation and hoisting installation of wind power equipment and to ensure the safety of the vessel, the entire vessel is equipped with 4 truss-type legs to share the weight of the vessel itself and the wind power equipment, as well as external wind loads. At the same time, a pre-set gripping shoe 8 is installed at the lowest point of each leg 6, which penetrates deep into the seabed mud layer to ensure the stability of the vessel during self-elevation operations.

[0079] Combination Figure 3 The methods for calculating the length of the pile leg include:

[0080] Pile leg height = Mud penetration depth + Working water depth + Air gap + Shape depth + Pile chamber height + Safety margin

[0081] Considering the requirements for deep-water operations, the operating water depth can reach 75 m, and the remaining heights can be calculated based on the following conditions;

[0082] Depth of penetration into the mud: Based on the characteristics of the seabed foundation and the type of pile shoe, the depth of penetration into the mud is calculated and analyzed. The maximum depth of penetration into the mud in deep water is 15 m.

[0083] Air gap: Based on the hull shape and sea state characteristics, the air gap in the nearshore deep water area is set at a limit of 15 m;

[0084] Depth: 0–10 m, depending on the overall ship design;

[0085] Height of the pile gripping chamber: Based on performance calculations and the layout requirements of the pile gripping equipment, the height of the pile gripping chamber is 0 to 10 m.

[0086] Safety margin: 5 m for the entire length;

[0087] Therefore, the length of the pile leg = 15 m + 75 m + 15 m + 10 m + 10 m + 5 m = 130 m.

[0088] Combination Figures 4 to 6 The structural strength design method for ultra-high pile legs includes:

[0089] The ultra-high pile legs 6 allow for a larger span of the truss after the seabed and ship are lifted, and the strength requirements for pile legs 6 are higher. Therefore, a truss with a triangular cross section is used to improve structural stability, and it is supported on the inside by an inner horizontal tube 11 to ensure the strength of pile legs 6.

[0090] Furthermore, the pile legs 6 are made of high-strength and ultra-high-strength marine steel. The jacking rack 10 is made of special steel with a yield strength of not less than 690 MPa, a tensile strength of not less than 770 MPa, and a hardness between 240 and 290 HB, with a thickness of approximately 180 mm. It is guaranteed that during the V-notch -40℃ impact test, the longitudinal impact strength is not less than 69 J and the transverse impact strength is not less than 46 J. The main hull tube is divided into two semicircles, including an outer main hull tube 91 and an inner main hull tube 92. The outer and inner main hull tubes 91 and 92 are arranged opposite each other, enclosing the rack 10. These tubes are circular with a yield strength of not less than 690 MPa and a tensile strength of not less than 770 MPa (approximately 500 mm in diameter and 80 mm thick), and are guaranteed that during the V-notch -40℃ impact test, the longitudinal impact strength is not less than 69 J and the transverse impact strength is not less than 46 J. The diagonal brace tube 7 is made of steel with a yield strength of not less than 555 MPa and a tensile strength of not less than 625 MPa. The inner horizontal tube 11 is a round tube with a yield strength of not less than 360 MPa and a tensile strength of not less than 460 MPa (diameter 152.4 mm, thickness 10 mm), and the impact strength is guaranteed to be not less than 55 J during the V-notch -40℃ impact test; the inner horizontal tube 11 is a round tube with a yield strength of not less than 360 MPa and a tensile strength of not less than 460 MPa (diameter 152.4 mm, thickness 10 mm), and the impact strength is guaranteed to be not less than 34 J during the V-notch -40℃ impact test.

[0091] Alternatively, the installation methods for ultra-high pile legs include:

[0092] The offshore wind turbine installation vessel is nearly 200 meters long and is considered a large vessel. It can only be built in large shipyards. However, the effective lifting height of the large lifting equipment gantry cranes of major shipbuilding companies in China is only about 75 to 80 meters, which cannot meet the lifting and installation requirements of the 130-meter-long pile leg 6.

[0093] Each leg 6 is divided into two parts: Part 1 is 70 m long, and Part 2 is approximately 60 m long, resulting in a total of 8 leg 6 parts for the 4 legs 6. In the shipyard's dry dock, a large gantry crane is used to hoist Part 1 of the 4 legs 6 separately for hoisting, pile insertion, and leg lifting / lowering tests to ensure that all 4 legs 6 can properly grip the pile and lift / lower. The ship is then sailed to the sea area outside the shipyard, where the water depth must meet the operating depth requirements of the large crane vessel. Using the ship's pile-gripping equipment, Part 1 of leg 6 is lowered, with its top surface approximately 1 m above the pile-gripping chamber top to facilitate subsequent construction. If necessary, to ensure this 1 m of welding space, the legs 6 can be inserted into the seabed mud layer. Using the crane vessel, Part 2 of the 4 legs 6 is sequentially hoisted onto Part 1. After Part 1 and Part 2 are aligned and fixed, welding is carried out at sea. Once the welding of the 4 Part 2 parts is completed, legs 1 through 4 of the 6 are installed. If the crane vessel's performance is limited, the two components of the four legs 6 can be disassembled into two parts and installed sequentially at sea.

[0094] The vessel of this invention is self-propelled, has a self-elevating function, and possesses deep-water operation capabilities, high lifting capacity, and large deck cargo capacity. It enables integrated transportation of offshore wind turbines from the dock base to deep-water areas and completes the installation of offshore wind power equipment of 20MW and below. It also solves the manufacturing and installation problems of its ultra-high pile legs 6.

[0095] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A design method for a deep-sea self-propelled and self-elevating offshore wind turbine installation vessel, characterized in that, The deep-sea self-propelled and self-elevating offshore wind power installation vessel includes: a main hull with a streamlined design; lifting equipment and a hoisting system installed on the main hull; the lifting equipment includes a main hoist and auxiliary hoisting equipment; the hoisting system includes pile legs, pile shoes, cofferdams and guide structures, a pile clamping chamber and a pile clamping and lifting device, with four sets of cofferdams and guide structures respectively located at the four corners of the main hull, each cofferdam containing one pile leg, the upper part of which is connected to the pile clamping chamber and the pile clamping and lifting device, and the bottom of which is connected to the pile shoe; the length of the pile leg is greater than or equal to 130m; the main hoist has a lifting capacity of 1600t and a lifting height of 175m, and the main hoist is combined with one of the hoisting systems, using the cofferdams and guide structures as the support structure for the hoist; excluding the hoisting equipment and the bow living area, the remaining deck surface of the main hull is designed as a flat surface with a deck area greater than or equal to 3400m². 2 The deck is designed to withstand 15 t / m 2 The uniformly distributed load setting is strengthened; the pile leg includes a truss-type pile leg, including three diagonal bracing pipes arranged in a triangle along the horizontal direction, and an inner horizontal pipe connecting two adjacent diagonal bracing pipes; The design method includes: hull design and ultra-high leg design; wherein the hull design includes: 1) The main hull adopts a streamlined waterline design to reduce the ship's sailing resistance, and performs stability, freeboard, buoyancy, and wind load calculations to ensure the ship's floating state and stability. With the appropriate power and auxiliary machinery, the ship is guaranteed to have a self-propelled capability of 8 knots. 2) Two sets of lifting systems are installed on both the port and starboard sides of the vessel, for a total of 4 lifting systems, which consist of pile legs, pile shoes, cofferdam and guide structure, pile holding chamber and pile holding lifting equipment; 3) Based on the required water depth, determine the length of the pile legs according to the design method for ultra-high pile legs to meet the requirements for deep-water operation capability; 4) Based on the weight and size parameters of the current largest 20 MW wind power equipment and the requirements for integrated transportation and hoisting, the lifting capacity of the main hoist equipment is determined to be 1600 t and the lifting height is 175 m. The main hoist is combined with one of the lifting systems, and the cofferdam and guide structure are used as the support structure for the hoist to ensure the hoist's lifting capacity, lifting height and working radius. 5) Excluding the space occupied by the elevator equipment and the bow living quarters, the remaining deck surface adopts a flat design, with a deck area of ​​3400 m². 2 The deck is designed to withstand 15 t / m 2 The uniform load distribution setting is strengthened to ensure that the large deck has the maximum cargo carrying capacity for transporting and hoisting two sets of 20 MW wind power equipment; The vessel is equipped with two lifting systems, one forward and one aft, on both the port and starboard sides, totaling four lifting systems. These systems consist of pile legs, pile shoes, cofferdams and guide structures, pile clamping chambers, and pile clamping and lifting equipment, including: a. In accordance with the requirements for controlling the ship's center of gravity, the lifting system must ensure that the ship and wind power equipment remain balanced during the lifting process; b. The load on the lifting system is determined by the rated lifting load, the reaction force of the pile legs, the static and storm support load, the lifting speed, the design temperature, and the design life; c. Determine the performance of the power unit and the shape of the rack based on the load; The ultra-high leg design includes: using extended legs to increase the operating water depth, with the extended legs exceeding 130 meters in length, enabling the vessel to operate in water depths of up to 75 meters, meeting the installation needs of nearshore deep waters and even offshore areas; to meet the requirements of self-elevation and hoisting installation of wind power equipment and to ensure vessel safety, the vessel is equipped with four truss-type legs to share the weight of the vessel itself and the wind power equipment, as well as external wind loads. At the same time, a pre-set gripping shoe is installed at the lowest point of each leg, penetrating deep into the seabed mud layer to ensure stability during self-elevation operations; The method for calculating the length of the pile leg includes: Pile leg height calculation formula = depth into mud + working water depth + air gap + mold depth + pile holding chamber height + safety margin.

2. The design method for a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to claim 1, characterized in that, The strength design method for ultra-high pile leg structures includes: The ultra-high pile legs result in a larger span of the truss after the seabed and ship are lifted, and the strength requirements of the pile legs are higher. Therefore, a truss with a triangular cross section is used to improve structural stability, and the inner side is supported by an inner horizontal tube to ensure the strength of the pile legs.

3. The design method for a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to claim 2, characterized in that: The pile legs are made of high-strength and / or ultra-high-strength marine steel. The jacking rack is made of special steel with a yield strength of not less than 690 MPa, a tensile strength of not less than 770 MPa, and a hardness between 240 and 290 HB, with a thickness of approximately 180 mm. It is guaranteed that the longitudinal impact strength will be not less than 69 J and the transverse impact strength will be not less than 46 J during a V-notch impact test at -40°C. The main hull tube is divided into two semicircles, enclosing the rack. It is made of circular tube with a yield strength of not less than 690 MPa and a tensile strength of not less than 770 MPa, and is guaranteed that the longitudinal impact strength will be not less than 69 J and the transverse impact strength will be not less than 46 J during a V-notch impact test at -40°C. The diagonal bracing tube is made of circular tube with a yield strength of not less than 555 MPa and a tensile strength of not less than 625 MPa, and is guaranteed that the impact strength will be not less than 55 J during a V-notch impact test at -40°C. The inner horizontal tube is made of steel with a yield strength of not less than 360 MPa and a tensile strength of not less than 460 MPa. The tube has a strength of MPa and is designed to withstand a V-notch impact test at -40℃ with an impact strength of not less than 34 J.

4. The design method for a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to claim 3, characterized in that, The method for installing ultra-high pile legs includes: Each pile leg is divided into two parts: part one is 70 m long and part two is about 60 m long. A total of 8 pile leg parts are obtained from the 4 pile legs. Inside the shipyard's dry dock, a large gantry crane was used to lift and install the components of the four pile legs, and to conduct pile lifting and lowering tests to ensure that all four pile legs could properly grip the pile and rise and fall. When the ship is sailed to the waters outside the shipyard, the water depth must meet the operating depth requirements of large crane vessels. Using ship-mounted pile-holding equipment, the pile leg components are lowered, with the top surface of the pile leg components about 1 m above the top of the pile-holding chamber, which facilitates subsequent construction. If necessary, in order to ensure this 1 m of welding space, the pile leg can be inserted into the seabed mud layer. Using a crane vessel, component two of the four pile legs was hoisted onto component one in sequence. After component one and component two were aligned and fixed, welding was carried out at sea. After the four components are welded together, the pile legs 1 through 4 will be installed.

5. The design method for a deep-sea self-propelled and self-elevating offshore wind power installation vessel according to claim 4, characterized in that, If the crane vessel's performance is limited, the two components of the four legs can be disassembled into two parts and installed sequentially at sea.

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