Gravity type variable-length seabed single-point mooring connecting device of floating fan

Abstract

A gravity type variable-length seabed single-point mooring connecting device of a floating fan comprises a floating body with at least two pulley fairlead devices, a single-point anchor arranged on the seabed and connected with a rotatable device, and at least one weight located in water below the floating body. Wherein the heavy block is connected with the single-point anchor through a mooring rope passing through the pulley fair lead. The offshore mooring system is small in seabed coverage area, environment-friendly, high in mooring system efficiency, safer, more reliable, practical and feasible, has a wind indicator function, and can be used for offshore mooring positioning of the floating type wind power platform with the water depth ranging from 50 m to 300 m or even larger than 1500 m.

Description

Technical Field

[0001] The present invention relates to a technology in the field of ocean engineering structures, specifically a gravity variable-length subsea single-point mooring connection device for a floating wind power platform that can be used in water depths from 50 meters to 300 meters and even exceeding 1500 meters. Background Art

[0002] Existing mooring and positioning technologies for offshore floating structures include catenary type, tensioned (or semi-tensioned) leg type, and tension leg type. Among them, the catenary mooring has a large footprint (coverage area) on the seabed, which has a great impact on the marine water body and seabed environment; for deep-water areas, the weight of the steel catenary is too heavy and the cost is very high; for sea areas with a water depth less than 100 meters, due to the insufficient water depth, a long enough catenary shape cannot be formed between the mooring point on the floating body and the anchoring point on the seabed by the mooring cable / chain to provide the required mooring restoring force to limit the horizontal offset range of the offshore floating structure under the action of external forces such as wind, waves, and currents. Therefore, its mooring and positioning ability is poor in shallow water, and the length of the mooring chain required on the seabed is usually several times the water depth, which makes the offshore installation difficult, time-consuming, and costly; the dynamic tension of the catenary mooring cable increases exponentially with the increase of the horizontal offset of the offshore floating structure, which poses a great challenge to the design of the mooring system, including the strength and fatigue problems of the mooring cable.

[0003] The existing mooring and positioning method for offshore floating wind turbines is mainly realized by a mooring system composed of multiple anchors distributed on the seabed and the mooring cables / chains connected thereto. The multiple anchors on the seabed are arranged distributively, and the mooring points on the floating body (floating wind turbine) are also distributively arranged outside the foundation of the floating wind turbine to resist winds and waves from all directions of 360 degrees. The disadvantage of this method is the low efficiency of the mooring system. In particular, the anchors fixed on the seabed can only be used to resist the external wind and wave forces from one direction, that is, the external forces from the direction from the seabed anchor point to the floating body mooring point. When the external forces come from other directions, the anchors on this mooring cable cannot effectively play their roles.

[0004] The existing single-point mooring technology is mainly applied to offshore floating production storage and offloading vessels. Specifically, multiple mooring cables are connected to a single mooring point on the floating body, that is, multiple anchors distributed on the seabed are connected to a rotatable single-point mooring device with a wind vane function on the floating body through the mooring cables. In this way, the floating production storage and offloading vessel can rotate around the single-point mooring device with the change of the direction of the external forces (wind, waves, and currents), and the bow of the ship always faces the direction of the external forces, which plays a good role in reducing the wind and wave forces. Its disadvantage is that the single-point mooring device installed on the ship (floating body) is extremely complex and costly, and the mooring system has low efficiency with multiple anchors distributed on the seabed.

[0005] The existing floating platform positioning technology using pontoons cannot withstand harsh environments. For example, in a typhoon, it will move violently with the waves, causing fatigue fractures in its frame structure. The pontoons will have large displacements under the influence of waves. Therefore, even if the frame structure is strengthened (resulting in a significant increase in cost), it cannot provide an effective positioning function for the target floating platform. The existing technology based on underwater anchors cannot provide effective positioning for the target floating body, can only limit the position in one dimension, has low mooring system efficiency, and cannot provide a weather vane function. Summary of the Invention

[0006] In view of the design problems existing in the existing catenary mooring connection device and the problems of large seabed coverage area and low mooring system efficiency caused by the distributed arrangement of multiple seabed anchors adopted by the existing single-point mooring device, the present invention provides a gravity variable-length seabed single-point mooring connection device for a floating wind turbine, which has a small seabed coverage area, is environmentally friendly, has a weather vane function, has high mooring system efficiency, is safer and more reliable, and is practical and feasible.

[0007] The present invention is realized through the following technical solutions:

[0008] The present invention relates to a gravity variable-length seabed single-point mooring connection device for a floating wind turbine, comprising: a floating body with at least two pulley fairleads, a single-point anchor arranged on the seabed, and at least one counterweight located in the water below the floating body, wherein: the counterweight is connected to the single-point anchor by a mooring cable passing through the pulley fairleads.

[0009] A tower and a wind power generation device are provided on the floating body.

[0010] Preferably, the pulley fairleads are symmetrically arranged outside the floating body, and more preferably, they are centrosymmetrically arranged.

[0011] When one counterweight is adopted, the counterweight is connected to the single-point anchor arranged on the seabed by at least two mooring cables respectively passing through the corresponding pulley fairleads; the counterweight is located directly below the floating body during operation.

[0012] When the floating body is in the initial equilibrium position, the single-point anchor is located at the intersection of the vertical center line of the floating body and the seabed, the mooring points of multiple mooring cables / chains on the floating body are geometrically symmetrically arranged, and the counterweight is vertically located above the seabed single-point anchor and below the floating body.

[0013] When the floating body undergoes a horizontal displacement under the action of an external force from its initial equilibrium position, the effective length of its mooring cable is variable, that is, the length of the mooring cable between the floating body mooring point and the single point anchor on the seabed changes with the horizontal displacement of the floating body. At the same time, the counterweight moves up and down and left and right, and its position changes with the change of the effective length of the corresponding mooring cable. The sum of the vertical components of the tensions of all mooring cables is equal to the weight of the counterweight. The tension of each mooring cable is a non-constant value and changes with the angle with the water surface, thereby generating a mooring system restoring force, the absolute value of which is equal to the sum of the horizontal components of the tensions of all mooring cables. This restoring force increases with the increase of the floating body displacement. When the floating body displacement reaches a certain value, it is equal to the absolute value of the external force and has the opposite direction. When the external force disappears, it makes the floating body return to the initial position.

[0014] When more than two counterweights are adopted, each counterweight is respectively connected to the single point anchor arranged on the seabed through a mooring cable passing through the corresponding pulley fairlead; each counterweight is located directly below the corresponding pulley fairlead during operation.

[0015] When the floating body is in the initial equilibrium position, the single point anchor is located at the geometric center of the mooring connection device on the seabed, that is, the intersection of the vertical center line of the floating body and the seabed. The mooring points of multiple mooring cables / chains on the floating body are geometrically symmetrically arranged. The counterweight corresponding to each mooring cable is vertically located below the corresponding pulley fairlead and above the seabed.

[0016] When the floating body undergoes a horizontal displacement under the action of an external force (wind, wave, current) from its initial equilibrium position, the effective length of the mooring cable between the mooring point on the floating body and the single point anchor on the seabed changes with the change of the floating body displacement. The tension of the mooring cable is always equal to the weight of the corresponding counterweight. At this time, the tension of each mooring cable is a constant value, but the geometric angle with the water surface changes, thereby generating a mooring system restoring force, the absolute value of which is equal to the sum of the horizontal components of the tensions of all mooring cables. This restoring force increases with the increase of the floating body displacement. When the floating body displacement reaches a certain value, it is equal to the absolute value of the external force and has the opposite direction. When the external force disappears, it makes the floating body return to the initial position.

[0017] The upper part of the single point anchor on the seabed is provided with a rotatable mooring connection device, which is connected to the mooring cable to make the floating body and the wind turbine on its upper part always face the direction of the incoming wind, and at the same time, the position of the single point anchor on the seabed remains fixed. The single point anchor is preferably a concrete gravity anchor, with a skirt plate sunk below the seabed mud surface at the bottom and a cross-shaped watertight vertical partition inside. The rotatable mooring connection device is located at the center of the cross-shaped watertight vertical partition and is provided with a bearing rotating device inside.

[0018] The present invention relates to an integrated installation method based on the gravity-type variable-length submarine single-point mooring connection device. After a single-point anchor with a built-in vertical watertight bulkhead empty compartment and a counterweight are prepared by concrete, a mooring cable is used to connect the single-point anchor and the counterweight at a shore wharf, and a conventional marine transport lashing / fastening device is used to temporarily connect the single-point anchor and the floating body carrying a tower and a wind turbine. A tugboat is used to tow the entire system in an integrated manner. When arriving at the offshore installation site, the marine transport lashing / fastening device of the single-point anchor is first released and seawater is injected into its empty compartment. Under gravity operation, the single-point anchor is automatically lowered to the seabed. Then, the counterweights are released one by one from the marine transport lashing / fastening device and lowered to a preset depth in the water. The mooring cables are tightened one by one, thereby completing the offshore installation of the wind turbine, the floating body and the mooring system at one time.

[0019] The marine transport lashing / fastening device adopts but is not limited to temporary connection components such as ropes. Technical Effects

[0020] Compared with the prior art, the technical effects of the present invention include:

[0021] i) The present invention breaks through the existing traditional constant-length mooring paradigm, that is, the physical length of the mooring cable between the mooring point on the floating body (such as the fairlead) and the anchor point on the seabed is a constant value, and proposes a new variable-length mooring paradigm, that is, the physical length of the mooring cable between the mooring point on the floating body (such as the fairlead) and the anchor point on the seabed is variable, which significantly reduces the maximum tension (static tension + dynamic tension) of the mooring cable and greatly improves the safety, reliability and fatigue life of the entire mooring system;

[0022] ii) The present invention reduces the footprint of the mooring system on the seabed to a minimum (only the size of an anchor), solving the problem that large-scale application of offshore floating wind power has a great impact on the marine ecological environment and the shared use of marine resources.

[0023] iii) The present invention has a wind vane function, so that the wind turbine always faces the direction of the incoming wind, which significantly improves the power generation efficiency of the wind turbine.

[0024] iv) The present invention can complete the offshore installation of the wind turbine, the floating body and the mooring system at one time through an integrated installation method, which greatly saves the offshore installation time and cost of the mooring system and significantly improves the offshore installation efficiency of the entire floating wind power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a two-dimensional schematic diagram of a gravity-type variable-length non-constant-tension seabed single-point mooring connection device;

[0026] Figure 2 It is a two-dimensional schematic diagram of the horizontal displacement of the floating body of the gravity-type variable-length non-constant-tension seabed single-point mooring connection device;

[0027] Figure 3 It is a three-dimensional rendering of a gravity-type variable-length non-constant-tension subsea single-point mooring connection device;

[0028] Figure 4 It is a two-dimensional schematic diagram of the fairlead of a gravity-type variable-length non-constant-tension subsea single-point mooring connection device, including a pulley and a connection structure, showing local details of the counterweight;

[0029] Figure 5 It is a three-dimensional schematic diagram of local details of the mooring cable connection ear plate of the counterweight of a gravity-type variable-length non-constant-tension subsea single-point mooring connection device;

[0030] Figure 6 It is a two-dimensional schematic diagram of a gravity-type variable-length constant-tension subsea single-point mooring connection device;

[0031] Figure 7 It is a two-dimensional schematic diagram of the horizontal offset of the floating body of a gravity-type variable-length constant-tension subsea single-point mooring connection device;

[0032] Figure 8 It is a side view of local details of the pulley fairlead and counterweight of a gravity-type variable-length constant-tension subsea single-point mooring connection device;

[0033] Figure 9 It is a three-dimensional schematic diagram of the connection between a gravity-type variable-length constant-tension subsea single-point mooring connection device and a floating wind turbine platform at the dock shore;

[0034] Figure 10 It is a side view of the overall sea tow of a gravity-type variable-length constant-tension subsea single-point mooring connection device and a floating wind turbine platform;

[0035] Figure 11 It is a three-dimensional schematic diagram of the installation of the subsea single-point gravity anchor of a gravity-type variable-length constant-tension subsea single-point mooring connection device;

[0036] Figure 12 It is a three-dimensional schematic diagram of the installation of the counterweight of a gravity-type variable-length constant-tension subsea single-point mooring connection device;

[0037] In the figure: 2 floating bodies, 2A upper hull of the floating body, 2B lower hull of the floating body, 4 wind tower, 6 fan nacelle, 8 fan blades, 30 fairlead, 30A vertical axial rotation mechanism, 30B support structure, 30R pulley, 31 mooring point of the floating body, 31A connection structure, 31B fairlead rotation structure, 32 mooring cable, 32L left mooring cable, 32R right mooring cable, 34 counterweight, 34A mooring connector, 34B connecting chain, 36 rotatable single point mooring connection device, 38 subsea single point anchor, 42 lower structure of the mooring connector, 44 upper structure of the mooring connector, 46 ear plate of the mooring connector, 48 inner connecting plate of the mooring connector, 50 fairlead, 50A pulley, 50B vertical axial rotation mechanism, 50C support structure, 51 mooring point of the floating body, 51A connection structure, 52A one end of the mooring cable, 52B the other end of the mooring cable, 54 counterweight, 56 rotatable single point mooring connection device, 58 subsea single point anchor, 101 water surface, 201 seabed / ocean floor, 301 wind load, 302 wave load, 401 restoring force of the mooring system, 501 tugboat, 601 gravity. Detailed implementation manners Embodiment 1

[0038] As Figures 1-3 shown, this embodiment relates to a gravity type variable length non-constant tension subsea single point mooring connection device, including: a set of mooring connection device 1, a floating body 2, a plurality of fairleads 30, a plurality of mooring cables 32, a large counterweight 34 and an attached mooring connector 34A, a subsea single point anchor 38 located on the seabed 201 and an attached rotatable single point mooring connection device 36, wherein: each fairlead 30 is connected to a mooring point 31 of the lower hull 2B of the floating body, and each mooring cable 32 passes through the corresponding fairlead 30, one end is connected to the counterweight 34, and the other end is connected to the rotatable single point mooring connection device 36 above the subsea single point anchor 38.

[0039] The upper hull 2A of the floating body is above the water surface 101, the lower hull 2B of the floating body is below the water surface 101, and a wind tower 4 is provided on the upper hull 2A of the floating body for supporting the fan nacelle 6 at the top of the wind tower 4 and the fan blades 8 connected to the fan nacelle 6.

[0040] When the floating body 2 is in the initial equilibrium position, the subsea single point anchor 38 is located at the geometric center of the mooring connection device 1 on the seabed, that is, the intersection of the vertical center line of the floating body 2 and the seabed 201. The plurality of fairleads 30 and the corresponding plurality of mooring cables 32 are geometrically symmetrically arranged at the corresponding mooring points 31 on the floating body 2. The counterweight 34 is vertically located at a certain distance below the lower hull 2B of the floating body above the subsea single point anchor 38; the total sum of the vertical components of the tensions of all mooring cables 32 is equal to the weight of the counterweight 34. Due to the symmetric arrangement, the initial tensions of each mooring cable 32 are equal.

[0041] When the floating body 2 generates a horizontal offset in the right direction under the action of the external wind load 301 and wave load 302, the effective lengths of the mooring cables 32L and 32R, that is, the lengths of the mooring cables between the floating body mooring point 31 and the single-point anchor 38 on the seabed, change with the change of the horizontal offset of the floating body 2. Among them, 32L becomes shorter and 32R becomes longer. At the same time, the counterweight 34 and the attached mooring connectors 34A are connected to the mooring cables 32L and 32R, generating up-and-down and left-and-right movements to keep the physical total length of each mooring cable 32L and 32R from the counterweight 34 to the single-point anchor 38 on the seabed unchanged. At this time, the horizontal angles of the mooring cables 32L and 32R with the floating body mooring point 31 change, and the tensions are not equal. The sum of the vertical components of the tensions of the mooring cables 32L and 32R is equal to the weight of the counterweight 34. The horizontal component of the tension of the mooring cable 32L becomes smaller, and the horizontal component of the tension of the mooring cable 32R becomes larger. Thus, the resultant value of the horizontal direction of the tensions of all the mooring cables 32L and 32R of the mooring connection device 1 generated is greater than zero, and its direction is to the left, that is, a restoring force 401 of the mooring system is generated, and its direction is opposite to the directions of the external acting forces wind load 301 and wave load 302, and the absolute values are equal, so as to achieve the dynamic balance of the horizontal displacement of the floating hull 2. This restoring force 401 increases with the increase of the horizontal displacement of the floating hull 2, and its magnitude can be calculated according to the internal tension values of the mooring cables 32L and 32R, the water depth, and the magnitude of the horizontal displacement of the floating hull 2. The magnitude of the initial internal tension of the mooring cables 32L and 32R is determined by the weight of the counterweight 34 and its position in the water.

[0042] A rotatable mooring connection device 36 with a wind vane function is provided on the single-point anchor 38 on the seabed, so that the floating body 2 rotates with the directions of the external forces 301 and 302, and the upper fan systems 6 and 8 always face the directions of the external forces 301 and 302. This wind vane function can significantly improve the power generation efficiency of the fan. When the external force disappears, the restoring force 401 of the mooring system makes the floating body 2 return to the initial position.

[0043] The single-point anchor 38 is preferably a concrete gravity anchor, which is internally provided with a cross-shaped vertical watertight partition. The rotatable mooring connection device 36 is located at the center of the cross-shaped vertical watertight partition and is internally provided with a bearing rotating device. The bottom of the concrete gravity anchor is provided with a skirt plate, which sinks into the seabed mud surface under the action of gravity to provide horizontal resistance.

[0044] As Figure 3 shown, when three fairleads 30 and three corresponding floating body mooring points 31 are provided on the floating body 2, three mooring cables 32 are adopted, and each mooring cable 32 passes through the corresponding fairlead 30, one end is connected to the counterweight 34, and the other end is connected to the rotatable single-point mooring connection device 36 located above the single-point anchor 38 on the seabed.

[0045] When the floating body 2 is in the initial equilibrium position, the subsea single point anchor 38 is located at the geometric center of the mooring connection device 1 on the seabed, that is, at the intersection of the vertical center line of the floating body 2 and the seabed 201. The three fairleads 30 are geometrically symmetrically arranged on the floating body 2. The counterweight 34 is vertically located at a certain distance above the subsea single point anchor 38 and below the floating body 2. In this symmetric arrangement state, the initial tensions of each mooring cable 32 are equal, and the total vertical component of the tensions of all mooring cables 32 is equal to the weight of the counterweight 34.

[0046] The mooring cable 32 is a steel cable, a steel chain, a polyester cable, a nylon cable or a combination thereof.

[0047] The counterweight 34 is made of concrete material, steel material or other heavy materials or a combination thereof. There are multiple empty compartments inside its main body and it can temporarily float on the water surface. It is provided with a mooring connector 34A including three ear plates for connecting the mooring cables. The subsea single point anchor 38 is a suction anchor pile, a driven anchor pile or a gravity anchor.

[0048] As Figure 4 shown, the fairlead 30 is located on the right side of the lower hull 2B of the floating body and includes: a pulley 30R with a groove, a set of vertical axial rotation mechanisms 30A, a support structure 30B and a mooring cable 32R. Among them: the vertical axial rotation mechanism 30A is connected to the floating body mooring point 31 through a connection structure 31A. One end of the mooring cable 32R is connected to the subsea single point anchor (not shown in the figure), changes direction upward through the groove of the pulley 30R, and the other end is connected to the mooring connector 34A. The size of the groove of the pulley 30R matches the size of the mooring cable 34A.

[0049] The upper end of the mooring connector 34A is simultaneously connected to the mooring cable 32L on the left side, and the lower end is connected to the upper end of the counterweight 34 through a connecting chain 34B.

[0050] As Figure 5 shown, the mooring connector 34A includes: a lower structure 42, an upper structure 44, three ear plates 46 respectively used for connecting their corresponding mooring cables 32 and a plurality of connecting inner plates 48. Among them: the lower structure 42 is connected to the counterweight 34 through a connecting chain 34B.

[0051] In actual application, the weight of the counterweight 34 usually depends on the magnitude of the maximum external wind and wave forces. For large-scale (such as 15 MW) floating offshore wind turbines, its weight range is usually 500 - 1000 tons or more. Since the counterweight 34 has a relatively large (hundreds of tons) weight and is suspended below the floating body 2, the stability of the floating body 2 can be increased. Embodiment 2

[0052] As Figures 6-8As shown, this embodiment relates to a gravity-type variable-length constant-tension subsea single-point mooring connection device. Specifically, as Figure 6 shown, when two counterweights and two mooring cables are used, each mooring cable 52 passes through the corresponding fairlead 50, one end is vertically downwardly connected to the corresponding counterweight 54, and the other end is connected to the rotatable single-point mooring connection device 56 above the subsea single-point anchor 58. When the floating body 2 is in the initial equilibrium position, the subsea single-point anchor 58 is located at the geometric center of the mooring connection device 1A on the seabed, that is, the intersection of the vertical centerline of the floating body 2 and the seabed 201. Each fairlead 50 and the corresponding mooring cable 52 are geometrically symmetrically arranged at the corresponding floating body mooring point 51 on the floating body 2. The counterweight 54 is vertically located a certain distance below the corresponding fairlead 50, and the tension of the mooring cable 52 is equal to the weight of the corresponding counterweight 54.

[0053] As Figure 7 shown, when the floating body 2 generates a horizontal offset to the right under the action of the external wind load 301 and wave load 302, the effective lengths of the mooring cables 52L and 52R, that is, the mooring cable lengths between the floating body mooring point 51 and the subsea single-point anchor 58, change with the horizontal offset of the floating body 2. Among them, the mooring cable 52L becomes shorter and 52R becomes longer. At the same time, the counterweight 54L moves downward and the counterweight 54R moves upward to keep the physical total length of each mooring cable (52L and 52R) from the corresponding counterweight (54L and 54R) to the subsea single-point anchor 38 unchanged. At this time, the horizontal angles between the mooring cables 52L and 52R and the corresponding floating body mooring point 51 change, resulting in a decrease in the horizontal component of the tension of the mooring cable 52L and an increase in the horizontal component of the tension of the mooring cable 52R. Thus, the resultant value of the horizontal direction of the tensions of all the mooring cables 52L and 52R of the mooring connection device 1A is greater than zero, and its direction is to the left, that is, a restoring force 401 of the mooring system is generated, and its direction is opposite to the directions of the external acting wind load 301 and wave load 302 and has the same absolute value, so as to realize the dynamic balance of the horizontal displacement of the floating hull 2. This restoring force 401 increases with the increase of the horizontal displacement of the floating hull 2, and its magnitude can be calculated according to the internal tension values of the mooring cables 52L and 52R, the water depth, and the magnitude of the horizontal displacement value of the floating hull 2. The internal tension values of the mooring cables 52L and 52R are constant values equal to the weights of their corresponding counterweights 54L and 54R. When the external force disappears, the restoring force 401 makes the floating body 2 return to the initial position.

[0054] The upper part of the subsea single point anchor 58 is provided with a rotatable mooring connection device 56 with a wind vane function, which includes a set of vertical axial rotation mechanisms, a connection structure, and a mooring connector with at least three ear plates for connecting mooring cables, enabling the floating body 2 to rotate along with the directions of external forces 301 and 302, and the wind turbine systems 6 and 8 on its upper part to always face the directions of external forces 301 and 302. This wind vane function can significantly improve the power generation efficiency of the wind turbine.

[0055] The single point anchor 58 is preferably a concrete gravity anchor, internally provided with a cross-shaped vertical watertight partition. The rotatable mooring connection device 56 is located at the center of the cross-shaped vertical watertight partition and is internally provided with a bearing rotation device. The bottom of the concrete gravity anchor is provided with a skirt plate, which sinks into the seabed mud surface under the action of gravity to provide horizontal resistance.

[0056] As Figure 8 shown, the fairlead 50 is located on the right side of the lower hull 2B of the floating body, and includes a pulley 50A with a groove, a set of vertical axial rotation mechanisms 50B, and a support structure 50C. The fairlead 50 is connected to the floating body mooring point 51 through a connection structure 51A.

[0057] The mooring cable includes a vertical section 52A and an inclined section 52B. One end of the vertical section 52A is vertically downwardly connected to the corresponding counterweight 54, and changes direction upward through the groove of the pulley 50A. One end of the inclined section 52B is connected to the vertical section 52A in the groove of the pulley 50A, and the other end is connected to the subsea single point anchor (not shown in the figure). Among them, the size of the groove of the pulley 50A matches the diameter of the mooring cable.

[0058] When the floating body 2 generates vertical axial rotation, the vertical axial rotation mechanism 50B drives the pulley 50A and the mooring cables 52A, 52B to rotate together around the vertical axis.

[0059] When the gravity type variable length constant tension subsea single point mooring connection device is actually applied to a floating wind power platform, usually three counterweights with the same weight, three fairleads, and three mooring cables are adopted. The weight of the counterweight depends on the magnitude of the maximum external wind and wave forces. For large-scale (such as 15 MW) floating offshore wind turbines, the weight range of each counterweight is usually 300 - 700 tons or more. Since the counterweight has a relatively large (hundreds of tons) weight and is suspended under the floating wind power platform, its stability can be improved.

[0060] As Figure 9As shown in the figure, the subsea single point anchor 58 is a reinforced concrete structure with multiple internal vertical watertight bulkhead voids, which can float temporarily on the water surface, connect with the rotatable mooring connection device 56 above it, and integrally connect with the floating body 2, the wind tower 4, the fan nacelle 6, the fan blades 8, the fairlead 50, the mooring cable 52 and the counterweight 54 at the dock shore to form a floating wind turbine integrated system 1B. Among them, the mooring cable 52, the counterweight 54, the subsea single point anchor 58 and the floating body 2 are temporarily connected by a marine fastening / tying device (not shown in the figure). Specifically, the floating body 2 has three columns, three fairleads 50, three mooring cables 52 and three counterweights 54 with the same weight.

[0061] This embodiment relates to the above floating wind turbine integrated system 1B, and realizes the offshore installation through the following methods and processes.

[0062] The first step, as Figure 10 shown in the figure, the tugboat 501 towes the floating body 2, the wind tower 4, the fan nacelle 6, the fan blades 8, the fairlead 50, the mooring cable 52, the counterweight 54, the subsea single point anchor 58 and its attached rotatable mooring connection device 56 to the offshore wind farm location.

[0063] The second step, as Figure 11 shown in the figure, when reaching the offshore wind farm location, release the marine fastening / tying device of the subsea single point anchor 58 and its corresponding mooring cable 52, and inject seawater into its voids. Under the action of gravity 601, the subsea single point anchor 58 and its attached rotatable mooring connection device 56 sink to the seabed 201.

[0064] The third step, as Figure 12 shown in the figure, release the marine fastening / tying device of the counterweight 54 and its corresponding mooring cable 52 one by one. Under the action of gravity 601, the counterweight 54 sinks to a predetermined depth in the water, and the mooring cable 52 is tightened to complete the installation of the gravity variable length constant tension subsea single point mooring connection device of the present invention.

[0065] The above specific implementation can be locally adjusted by those skilled in the art in different ways without departing from the principles and purposes of the present invention. The protection scope of the present invention is subject to the claims and is not limited by the above specific implementation. All implementation solutions within its scope are subject to the present invention.

Claims

1. A gravity - type variable - length non - constant - tension subsea single - point mooring device, characterized in that, it includes: a floating body, which is connected with a wind tower above the water surface to support a set of wind power generation devices, a large - scale shared underwater weight, which is vertically located at a certain distance below the center of the floating body, a subsea single - point anchor, multiple mooring cables, multiple fairleads connected to the corresponding mooring points of the floating body, wherein: each mooring cable passes through the corresponding fairlead, one end is connected to the shared underwater weight below and inside, and the other end is connected to the subsea single - point anchor. The total vertical component of the tensions of all mooring cables is equal to the weight of the shared underwater weight; when the floating body generates a horizontal offset, the shared underwater weight moves up and down and left and right. The effective length of each mooring cable, that is, the length between the mooring point of the floating body and the subsea single - point anchor, changes with the change of the offset of the floating body, generating a mooring system restoring force; the upper part of the subsea single - point anchor is provided with a rotatable mooring device with a wind vane function. The rotatable mooring device includes: a set of vertical - axis rotation mechanisms, a connection structure, and a mooring connector with at least three ear plates for connecting the mooring cables, so that the floating body rotates with the direction of the external environmental force.

2. The gravity - type variable - length non - constant - tension subsea single - point mooring device according to claim 1, characterized in that, the mooring points of the floating body, fairleads, and mooring cables form a mooring unit, and at least three sets of such mooring units are provided; the mooring points of the floating body are symmetrically arranged; the subsea single - point anchor is located at the geometric center of the mooring device on the seabed, that is, the intersection of the vertical center line of the floating body and the seabed; the shared underwater weight is vertically located above the subsea single - point anchor.

3. The gravity - type variable - length non - constant - tension subsea single - point mooring device according to claim 1, characterized in that, the shared underwater weight is made of concrete material, steel material or a combination thereof, and multiple empty compartments are provided inside it for temporarily floating on the water surface; the upper part of the shared underwater weight is provided with a mooring connector with at least three ear plates for connecting the mooring cables; the subsea single - point anchor is a suction anchor pile, a driven anchor pile or a gravity anchor; the mooring cable / chain is a steel cable, a steel chain, a polyester cable, a nylon cable or a combination thereof.

4. The gravity - type variable - length non - constant - tension subsea single - point mooring device according to claim 1, characterized in that, the fairlead includes: a pulley with a groove, a set of vertical - axis rotation mechanisms and a connection structure. Among them: the pulley is connected to the corresponding mooring point of the floating body through the connection structure. One end of the mooring cable is connected to the shared underwater weight, changes direction through the pulley groove, and the other end is connected to the subsea single - point anchor. The vertical - axis rotation mechanism drives the pulley and the mooring cable to rotate around its vertical axis together.

5. A gravity - type variable - length constant - tension subsea single - point mooring device, characterized in that, it includes: a floating body, which is connected with a wind tower above the water surface to support a set of wind power generation devices, a subsea single - point anchor, multiple mooring cables, multiple fairleads connected to the corresponding mooring points of the floating body on the floating body, multiple underwater weights, Wherein: Each mooring cable passes through a corresponding fairlead, with one end vertically downwardly connected to a corresponding underwater weight and the other end connected to the single-point mooring anchor on the seabed. The underwater weight is vertically located below the corresponding fairlead, and the tension of the mooring cable is equal to the weight of the underwater weight; When the floating body undergoes a horizontal offset, the underwater weight moves up and down, and the effective length of each mooring cable, that is, the length between the mooring point of the floating body and the single-point mooring anchor on the seabed, changes with the change of the offset of the floating body, generating a mooring system restoring force; The upper part of the single-point mooring anchor on the seabed is provided with a rotatable mooring device with a weather vane function. The rotatable mooring device includes: a set of vertical axial rotation mechanism, a connection structure, and a mooring connector with at least three ear plates for connecting the mooring cable, enabling the floating body to rotate along with the direction of the external environmental acting force.

6. The gravity-type variable-length constant-tension single-point mooring device on the seabed according to claim 5, characterized in that, The mooring points of the floating body, fairleads, mooring cables, and underwater weights form mooring units, and there are at least three sets of such mooring units; The mooring points of the floating body are symmetrically arranged; The single-point mooring anchor on the seabed is located at the geometric center of the mooring device on the seabed, that is, the intersection of the vertical center line of the floating body and the seabed; The mooring cables are steel cables, steel chains, polyester cables, nylon cables, or a combination thereof; The underwater weights are made of reinforced concrete materials, steel materials, or a combination thereof.

7. The gravity-type variable-length constant-tension single-point mooring device on the seabed according to claim 5, characterized in that, The fairlead includes: a pulley with a groove, a set of vertical axial rotation mechanism, and a support structure. Among them: the pulley is connected to the corresponding mooring point of the floating body through the support structure. One end of the mooring cable is vertically downwardly connected to the corresponding underwater weight, changes its direction upward through the pulley groove, and the other end is connected to the single-point mooring anchor on the seabed, and the internal tension thereof is equal to the weight of the corresponding underwater weight; When the floating body undergoes a vertical axial rotation, the vertical axial rotation mechanism drives the pulley and the mooring cable to rotate around its vertical axis together.

8. An integrated installation method for a gravity-type variable-length constant-tension single-point mooring device on the seabed according to any one of claims 5 - 7, characterized in that, The single-point mooring anchor on the seabed is a reinforced concrete structure with a cross-shaped vertical watertight partition inside, and there are multiple empty compartments inside for temporarily floating on the water surface. Its upper part is connected to a rotatable mooring device with a weather vane function located at the center of the cross-shaped vertical watertight partition, and is integrated with the floating body, the wind turbine system, and the mooring device on the dock shore to form a floating wind turbine integrated system. Among them, the mooring cable, the underwater weight, and the single-point mooring anchor on the seabed are respectively temporarily connected to the floating body through offshore fastening devices; The wind turbine system includes: a wind tower, a wind turbine nacelle, and wind turbine blades; The mooring device includes: fairleads, mooring cables, and underwater weights; The bottom of the concrete gravity anchor is provided with a skirt plate, which can sink into the seabed mud surface under the action of gravity.

9. The integrated installation method according to claim 8, characterized in that, The floating wind turbine integrated system floats on the water surface and is towed to the offshore wind farm location by a tugboat.

10. The integrated installation method according to claim 8, characterized in that, the floating wind turbine overall system is positioned at the offshore wind farm location. First, the offshore fastening device of the subsea single point anchor and its corresponding mooring cable is released, and seawater is injected into its empty cabin. Under the action of gravity, the subsea single point anchor and its attached rotatable mooring device sink to the seabed. Then, the offshore fastening devices of the underwater weights and their corresponding mooring cables are released one by one. Under the action of gravity, the underwater weights sink to a predetermined depth in the water, and the mooring cables are tightened to complete the installation of the mooring device.

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