Method for positioning a keel of a floating structure, in particular a keel for a wind turbine

Abstract

The offshore floating structure (100) comprises a positively buoyant floater (200) and a negatively buoyant keel (300), as well as active and passive suspenders (400) connecting the nodes of the keel (300) and the floater (200) together. When the keel (300) at the offshore site is lowered by making the active suspenders (440) longer, the passive suspenders (420) having a certain length and being in tension will cause the keel (300) to rotate about the vertical during the lowering.

Description

Technical Field

[0001] The present invention relates to a floating structure configured to perform positioning and alignment of a keel of the floating structure.

Background Art

[0002] Offshore structures for modern wind turbines are huge and are subject to the forces of a large area of the sea. The operations of transportation, installation, and fixation each pose major challenges due to the wave and wind dynamic characteristics and diversity, as well as the enormous scale and size of the offshore structures.

[0003] This discussion is found in US3986471, which discloses a floating platform connected by a chain to a damping plate below the water surface. Also, US2012 / 0121340 discloses a polygonal base on the seabed that is cable-connected to a floating structure for installing and holding a wind turbine. The cable extends from the base to a central underwater counterweight via a pulley on the floating structure. US10774813 discloses a platform for a wind turbine, in which the counterweight is placed near the final floating platform during transportation to the deployment location and is then submerged to a greater depth. US2009 / 0235856 discloses a semi-submerged floating platform for use in offshore applications.

[0004] Installation at the site where the counterweight is deployed presents some issues regarding damage avoidance. Thorough discussions of various principles can be found in WO2017 / 157399, which itself discloses a support structure for a floating wind turbine, the support structure comprising a buoyancy tank and a sub-surface counterweight for increased stability. The buoyancy tanks are arranged in a triangle. During transportation, the counterweight is filled with air and placed near the buoyancy tank. Upon deployment, the counterweight is instead filled with water and, until the suspension chain stops further downward movement and determines the depth of the counterweight below the floating support tetrahedron, it is deeper in the sea below the surface.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] Theoretically, the sinking of the counterweight can be expected to occur smoothly and gradually while filling with water. However, in practice, the counterweight can gain a significant speed due to the sinking, which may result in a sudden stop when the chain extends. Such a sudden stop poses a risk of damage to the structure. Also, when the counterweight sinks, the chain does not guide the counterweight vertically, so there is a risk that the counterweight will move laterally with respect to the floating structure. WO2017 / 157399 also proposes using a telescopic arm when the counterweight sinks, but this can only partially solve the problem in that the telescopic arm when the counterweight sinks can have different lengths, resulting in deviation from the vertical sinking and posing a risk of damage to the structure.

[0007] It would be useful to find improved and more controlled ways of deploying the counterweight during the installation of an offshore platform on site.

Means for Solving the Problem

[0008] The object of the present disclosure is to improve the technology of transporting, installing, and deploying a floating structure, particularly a floating structure configured to support operating devices such as a wind turbine generator. Specifically, it aims to lower the keel from the floating structure during installation at an offshore site while minimizing the risk of slack in the suspender and the resulting snap load between the floater and the keel, which could cause damage to the floating structure.

[0009] This object is achieved by a method of positioning the keel of a floating structure. The method includes the acts as disclosed herein.

[0010] There is an act of providing a floating structure having a keel suspended by a suspender connected to a floater.

[0011] There is an act of positioning the keel while constantly maintaining the tension of the suspender at all stages of the keel positioning.

[0012] By constantly maintaining the tension of the suspender at all stages of the keel positioning, the floating structure is a substantially single rigid body both during and at all times before and after positioning. As a result, the slack of the suspender between the float and the keel and the resulting risk of snap load are significantly reduced.

[0013] A further advantage is that the method allows or enables adjusting the moment of rotational inertia of the floating structure while managing a single rigid body, and the moment of rotational inertia of the floating structure can be adjusted. It is to reduce the slack of the suspender between the float and the keel and the resulting risk of snap load.

[0014] This can be achieved by a method of positioning the keel of a floating structure that includes the following acts. There is an act of providing a floating structure including a keel with negative buoyancy suspended by a suspender at a first position below a float with positive buoyancy. There is an act of arranging the suspender so as to connect the keel and the float in a statically determined manner, forming the floating structure as a substantially dynamic single entity. There is an act of placing the keel at a second position while substantially maintaining the tension of the suspender. Thereby, the floating structure is maintained in a statically determined manner, and the floating structure is held as a substantially dynamic single entity.

[0015] There are a transfer mode and a keel deployment mode. During both modes, the keel can be placed at different positions, and each position results in a specific moment of rotational inertia of the floating structure, thereby providing an opportunity to optimize the dynamic behavior of the floating structure in the relevant sea state mainly through the adjustment of the pitch and roll frequencies through the adjustment of the moment of inertial rotation. The moment of rotational inertia can be adjusted alternately between the transfer mode and the keel deployment mode.

[0016] The method also enables adjustment of the moment of rotational inertia, for example, during the installation of a wind turbine generator on a floating structure. Sea surface and / or weather conditions may require different levels of moment of rotational inertia. For example, different levels of moment of rotational inertia may be required even during the installation phase of a wind turbine generator. The method of the present disclosure enables the structure to maintain a single rigid body during such alternations or installations. Also, the sagging of the suspender and the resulting risk of snap loads can be reduced or eliminated.

[0017] The provided floater has positive buoyancy. The floater can have adjustable buoyancy. The provided keel has negative buoyancy. The keel can have adjustable buoyancy.

[0018] Positioning is considered to include lowering or raising the keel relative to the floater. Positioning also includes positioning the keel at a specific distance or other position relative to the floater, including, for example, having rotated relative to the floater.

[0019] The provided floater is a substantially rigid structure. The floater can be configured to be more rigid within the floater plane and less rigid outside the floater plane. The provided keel is a substantially rigid structure. The keel can be configured to be rigid within the keel plane and less rigid outside the keel plane. The floater and keel can be provided as disclosed herein. In one aspect, such floater plane and keel plane can be provided as parallel planes.

[0020] Due to the opposing forces resulting from the positive buoyancy of the floater and the negative buoyancy of the keel, the entire floating structure comprising the floater and the keel is a substantially single rigid structure and will operate like a rigid body as the suspender is maintained substantially in tension or under tension.

[0021] In one embodiment, the act of providing the suspension includes providing a passive suspension and an active suspension that engage at substantially the same connection points on the keel and at separate connection points on the float.

[0022] The passive suspension is understood to be a suspension that is connected to a connection point on the float at one suspension end and to a connection point on the keel at the other end. Thus, the passive suspension has a certain length.

[0023] The active suspension is understood to be connected at one suspension end to at least one connection point of the float or the keel, and the other end is operably connected to the respective other keel or float such that the length of the active suspension between the respective connection points of the float and the keel is adjustable.

[0024] The suspension can comprise flexible suspension means such as a chain, link, rope, or the like, or a combination thereof, or can comprise rigid suspension means such as a rod, tube or the like. Also, the suspension can comprise a combination of flexible suspension means and rigid suspension means. The suspension can be rotatably connected to the float and / or the keel, such as by a link, bearing, pin connection, universal joint or the like, or a combination thereof. The suspension can be of fixed length or can be adjustably connected to the float and / or the keel to adjust the length of the suspension connecting the float and the keel. The suspension can be capable of supporting both tensile and compressive loads, or can be capable of supporting only tensile loads.

[0025] The active suspension and the passive suspension can have different characteristics and / or can be made of different materials.

[0026] In one embodiment, both the active and passive suspensions are flexible ropes, such as steel ropes, or synthetic ropes made of ultra-high molecular weight polyethylene, polyester, or nylon. In this embodiment, the active and passive suspensions may be made of different materials and / or have different dimensions.

[0027] In another embodiment, the active suspension is a flexible rope and the passive suspension is a rigid member such as a steel pipe.

[0028] Those skilled in the art can understand from the above as a starting point and select or design the actual suspension according to the actual size or mass of the structural elements.

[0029] In one embodiment, there is a first connection point, such as I, on the float. From this first connection point I, the first ends of the active and passive suspensions are connected. The other and second ends of the active suspension are connected to a first connection point, such as I, on the keel. The other and second ends of the passive suspension are connected to a second connection point, such as II, on the keel.

[0030] In one aspect, the positioning act is performed by operably adjusting the length of the active suspension; that is, the length of the active suspension between the connection point on the float and the connection point on the keel. Positioning can lower and raise the keel relative to the float. The adjustment is made such that the active and passive suspensions are kept in a tensioned state. Due to the forces in opposite directions of the float and the keel, the length of the active suspension can be adjusted at a rate that ensures that the active suspension is always kept substantially in a tensioned state during the positioning of the keel, thereby eliminating the risk of suspension slack and the resulting snap load.

[0031] In one aspect, the passive and active suspensions at one end engage the respective floaters and keels at substantially the same points, and the other ends engage at separate points on the respective floaters and keels.

[0032] It is understood that the passive and active suspensions form an acute non - parallel angle.

[0033] The floaters and keels used can have complementary shapes. In particular, the shapes considered are those resulting from the projection onto the seabed level. As an example, a triangular shape is disclosed in the figures. Other polygonal or circular shapes may be used. The polygon can be formed to have an even or odd number of nodes or corners. The base elements can be linear or of other shapes to provide the required rigidity.

[0034] In one aspect, the floater is substantially a floater triangle and the keel is substantially a keel triangle. The positioning act is performed at a transfer position that substantially forms one triangle when the floater triangle and the keel triangle are superimposed. That is, in the case of the projection onto a flat horizontal plane with respect to the seabed. There is a positioning act to the deployed keel position where the floater triangle and the keel triangle substantially form a star shape when superimposed.

[0035] It is understood that the floater and the keel can have the same shape when projected onto the horizontal plane. At the transfer position, the nodes of the keel can be substantially aligned below the corresponding nodes on the floater.

[0036] During the positioning of the keel during keel deployment, the keel can rotate relative to the floater such that the nodes of the keel rotate with respect to the corresponding nodes on the floater. The nodes of the keel can rotate, for example, to a position where they have approximately the same distance from two adjacent nodes on the floater so that they are between the corresponding and adjacent nodes.

[0037] As will be illustrated in more detail below, in a triangular float structure and a triangular keel structure, three passive suspenders are used and three active suspenders are used. From each of the three corners I, II, III of the triangular float, a passive suspender extends to the corresponding corner of the three corners I', II', III' on the keel. Also, from each of the three corners I', II', III' of the triangular float, the active suspender extends not to the same corner where the passive suspender extends, but to an adjacent corner on the keel, and the active expander extends from corner I of the float to corner II' of the keel, and from corner II of the float to corner III' on the keel, and from corner III of the float to corner I' on the keel. Since the passive suspender is maintained in a tensioned state during the descent of the keel, the distance between the attachment point of the corner on the float and the corresponding corner on the keel is fixed by the length of the corresponding passive suspender, and when the keel is deployed from a close distance to a large distance from the float, the keel will rotate relative to the float during the descent.

[0038] Under more general conditions, for useful embodiments, the float has a plurality of polygonal float nodes including a first float node, a second float node, and a third float node, and the keel has a corresponding number of polygonal keel nodes including a first keel node, a second keel node, and a third keel node, and the node count is in the rotational direction around the corresponding polygon, for example clockwise. The suspenders are provided in a corresponding number of suspender pairs, and each pair includes a passive suspender and an active suspender.

[0039] Each of the active suspenders connects only one float node to one keel node. The first float node and the first keel node are connected by the first active suspender, the second float node and the second keel node are connected by the second active suspender, and the third float node and the third keel node are connected by the third active suspender.

[0040] Each passive suspender connects only one floater node to only one keel node. The first floater node and the second keel node are connected by the first passive suspender, the second floater node and the third keel node are connected by the second passive suspender, and the third floater node and the keel node adjacent to the second keel node are connected by the third passive suspender. Such adjacent keel node is the first keel node when the keel has only three keel nodes.

[0041] This method includes suspending the keel by a suspender at a first position at a first depth in the water below the floater, and then, while changing the vertical distance between the floater and the keel from the first position at the first depth to a second position at a second depth by changing the lengths of all active suspenders, keeping the suspenders substantially in a tensioned state. Further, simultaneously, by maintaining a constant distance between the connection point on the floater and the connection point on the keel for each passive suspender, the keel is forced to rotate relative to the floater and about the vertical direction.

[0042] To achieve the above, the length of the passive suspender can be adjusted. Increasing the length of the passive suspender makes it possible to lower the keel deeper.

[0043] A specific deployment position of the keel can be achieved when the lengths of the corresponding or all passive suspenders and active suspenders are the same.

[0044] In one aspect, the positioning act is performed by adjusting the length of the passive suspender by a winch. In principle, the length of the passive suspender can also be adjusted, but the passive suspender can have a predetermined fixed length. A person skilled in the art will understand that the active suspender is an operational suspender.

[0045] The length can be adjusted by controlling the suspender using one or more winches. The winch can be arranged on another ship or on a floating structure. By arranging the winch on the floating structure, the floating structure can be operated independently like a ship. The winch can be permanently arranged on the floating structure, or temporarily arranged during transportation and keel deployment and removed after the keel deployment is completed. The floating structure can also be provided in a transportation mode without a winch. Then, when deploying the keel to the installation position, the winch can be temporarily installed.

[0046] The winch can be arranged at a safe position of the floating structure. Its embodiments are shown in the detailed description. A guide to the suspender can be preferably arranged between the winch and the contact point.

[0047] The winch can be provided according to its size, weight and other operating conditions.

[0048] In a floating structure configured to support an offshore wind turbine, the keel mass can be approximately several hundred tons to several thousand tons. During transportation from the port to the final position, in order to provide stability to the complete structure including the floater and the keel, the keel can be deballasted to an appropriate negative buoyancy before transportation. The deballasting is usually up to the vinegar plane that provides sufficient negative buoyancy to ensure that the suspender is always in a tension state during transportation and deployment, while maintaining the stability of the complete structure at the desired level. As an additional advantage of deballasting, only a certain proportion of the final and ballast weight of the keel needs to be supported, so the size of the winch required for positioning becomes smaller.

[0049] In one embodiment, the floating structure has a floater formed as a tetrahedral structure with a base being a floater base. Elements or legs extending from the floater base towards the apex can support a winch, and the suspender is supported by such legs and can reach a node or corner on the base.

[0050] In one aspect, the positioning act is performed by controlling the suspender with one or more winches arranged on one or more vessels.

[0051] Controlling or adjusting the length of the suspender can be done via a vessel operated separately from the floating structure. The vessel can be equipped with one or more winches.

[0052] The floating structure includes a suspender guide arranged to guide one or more suspenders from the vessel to the connection point. The suspenders can be operated by their respective individual vessels. The suspenders can be guided to be operated by one vessel equipped with one or more winches for operating each suspender. The suspender guide can be arranged as a direction change, turning, or guide along the straight path of the suspender.

[0053] The advantage is that the positioning of the keel, i.e., the positioning is separated from the installation and can be started in a simple way. The positioning of the keel can save time, which is a sparse offshore resource, and thus reduce the complexity of the operation.

[0054] When configured to support an offshore wind turbine, the time spent on the keel lowering of the floating structure can be less than 1 hour or less than 30 minutes.

[0055] In one aspect, the positioning act is performed by a vessel equipped with a winch for operating the active suspender at each floater node of the floater to position the keel.

[0056] In this way, the complexity of the suspender or line is minimized.

[0057] In one aspect, the positioning act is performed by a single vessel operating an active suspender at each floater node of the floater in order to position the keel nodes step by step, one by one.

[0058] In this way, the complexity of the suspender or line is minimized and only a single vessel is required.

[0059] In one aspect, the positioning act is performed by a single vessel including a plurality of winches, each operating an active suspender connected to a respective keel node to position the keel.

[0060] In this way, only one vessel is required and each keel node can be positioned individually or simultaneously. A further advantage is that the interaction between the vessel and the floater is simpler as the vessel interacts with the floater along the legs rather than at the nodes, as illustrated in the detailed description.

[0061] In one aspect, the positioning act is performed by a single vessel having a single winch operating a plurality of active suspenders connected to respective keel nodes to position the keel.

[0062] In this way, a single vessel equipped with a standard (although a large ship equipped with a large winch) winch can be used.

[0063] The object is achieved by a floating structure with a floater, keel, active, and passive suspenders.

[0064] The float is configured to have positive buoyancy according to the support structure. The float is configured to have a suspender arranged to suspend a keel configured to have negative buoyancy. The suspender comprises at least a passive suspender configured with a fixed length and at least an active suspender configured such that the length is adjustable so that the keel can be lowered and / or lifted.

[0065] The passive suspender and the active suspender are arranged at one end such that they engage at substantially the same point. At the other end of the passive and active suspenders, they connect to separate points on their respective floats and keels.

[0066] Thereby, a floating structure is provided that can operate as generally described, and the keel can be positioned while having the same advantages as generally described above.

[0067] The passive suspender is configured with a fixed length in the sense that the passive suspender is connected to the float and the keel at a given length. The given length can be selected, predetermined, changed, or adjusted, but generally, the passive suspender is provided with a predetermined length that defines a predetermined distance between the connection point on the float and the connection point on the keel.

[0068] The active suspender is configured such that the length is operably adjustable so that the distance between the connection points on the respective floats and keels is adjusted.

[0069] The floating structure may comprise means for adjusting and holding the active suspender. The floating structure can be configured with means for adjusting the suspender alone so that an auxiliary device or a ship can adjust the length of the active suspender, and interface means such as a guide can be arranged on the floating structure.

[0070] The active and passive suspensions can be placed in a predetermined position so as to function as the permanent suspension of the keel in the final deployed position. Alternatively, these functions in the keel suspension can be taken over by other permanent suspensions.

[0071] In one embodiment, the keel is permanently supported by a permanent suspension. During transfer and deployment, some of the permanent suspensions function as passive suspensions for keel positioning, and the remaining permanent suspensions are attached to the float and / or the keel by appropriate means and do not provide or at least do not fully provide part of the positioning performed by the active suspension. In this case, the active suspension lowers the keel to a position where the permanent suspension takes over and the active suspension relaxes.

[0072] To illustrate the floating structure, the keel is formed as a keel polygon having keel elements including permanent negative buoyancy elements. The float is formed as a float polygon having float elements including positive buoyancy elements connected at float nodes. The keel polygon and the float polygon may be substantially the same or may be scaled versions of each other. In one embodiment, the form can be such that the float is a float triangle and the keel is a keel triangle.

[0073] The floating structure can be configured such that the keel polygon, for example, the keel triangle, is substantially the same as the float polygon, for example, the float triangle. The float and the keel are substantially aligned and configured for the transfer mode.

[0074] According to the above disclosure, since the active suspension is gradually released while maintaining a tension state, the keel and the float can rotate relative to each other during the keel deployment mode.

[0075] There can be means for controlling the length of the active suspension. There can be means for holding the active suspension at a given length.

[0076] In one aspect, at least one active suspension is operably connected to at least one winch. The winch can adjust the length of the active suspension and can hold the length of the active suspension.

[0077] The arrangement of the active suspension and the winch can be configured such that the length of the active suspension can be adjusted from a given length to a certain length, whereby it is possible to separate the keel from the float by a distance equal to the passive length with respect to the predetermined length of the passive suspension. In one embodiment, the active suspension can be provided such that its length can be adjusted from the length of the passive suspension composed of "zero" (as short as possible).

[0078] There can be a computing unit having a computer program configured to receive inputs from sensors disposed on the float, the keel, and the active suspension, and further configured to control the active suspension such that the length of the active suspension is controlled or adjusted under tension while positioning the keel.

[0079] In one aspect, the float is formed as a tetrahedral structure including buoyancy elements whose float base is connected at a float node. The vertices of the tetrahedron are configured to support the wind turbine tower. The keel is formed as a keel triangle formed substantially complementary to the float base.

[0080] Such a floating structure is a substantially rigid single structure when attached to the keel and has been found to be capable of supporting an offshore wind turbine generator between various offshore conditions. This structure has been found to have a natural frequency outside the natural frequency of waves in the relevant sea state and to avoid the relaxation forces that arise due to the mutual mechanical relationship between the forces due to wind and waves acting on the wind turbine and the reaction force from the keel.

[0081] In short, there can exist a floating structure with a computing unit configured to perform the acts shown schematically and generally. It is possible to provide a computer program for executing instructions.

[0082] In some embodiments, the present invention relates to a method of installing an offshore floating structure, the floating structure comprising a floater having positive buoyancy, a keel having negative buoyancy, and a suspender connecting the keel and the floater to each other. The floater has a plurality of floater nodes arranged in a polygonal configuration, including a first floater node, a second floater node, and a third floater node. The keel has a corresponding number of keel nodes arranged in a polygonal configuration, including a first keel node, a second keel node, and a third keel node. The suspender is provided in a corresponding number of suspender pairs, each pair including a passive suspender and an active suspender. Each of the active suspenders connects at least one floater node and at least one keel node. Preferably, each of the active suspenders connects only one floater node to one keel node. The first floater node and the first keel node are connected by a first active suspender, the second floater node and the second keel node are connected by a second active suspension, and the third floater node and the third keel node are connected by a third active suspender. Each of the passive suspenders connects at least one floater node and at least one keel node. Preferably, each of the passive suspenders connects only one floater node and only one keel node. The first floater node and the second keel node are connected by a first passive suspender, the second floater node and the third keel node are connected by a second passive suspender, and the third passive suspender connects the third floater node to a keel node adjacent to the second keel node. This adjacent keel node is the first keel node when the keel has only three keel nodes. The method includes suspending the keel by the suspender at a first position at a first depth in the water below the floater.

[0083] As shown in FIG. 1, the polygonal configuration may be triangular, but the polygonal configuration may be a different configuration.

[0084] The method may further include substantially maintaining the tension of the suspenders while varying the vertical distance between the float and the keel from a first position at a first depth in the water to a second position at a second depth by changing the length of all active suspenders, and causing relative rotation of the keel with respect to the float about a vertical axis by maintaining each of the passive suspenders at a fixed length with a fixed distance from a connection point on the float to a connection point on the keel.

[0085] The keel can be formed as a polygon having keel elements including negative buoyancy elements connected at keel nodes, and the float is formed as a polygon having float elements including positive buoyancy elements connected at float nodes.

[0086] In some embodiments, the float has only three float nodes arranged as a triangle from which the suspenders extend to the keel nodes, and the keel has only three keel nodes arranged as a triangle from which the suspenders extend to the float.

[0087] The float can be formed substantially as a float triangle, and the keel is substantially formed as a keel triangle (333) of complementary shape. The method includes transporting the offshore floating structure to the offshore deployment site while the float triangle and the keel triangle substantially form a single triangle when superimposed, and at the site, changing to a deployment configuration in which the float triangle and the keel triangle are rotated relative to each other.

[0088] The float can also be formed as a tetrahedral structure having a float base including buoyancy elements connected at float nodes, with the apex (240) of the tetrahedral structure supporting a wind turbine tower.

[0089] Aspects The following presents several related aspects that can be combined with other features described herein.

[0090] Aspect 1. A method (1000) for positioning the keel of a floating structure (100), comprising: the act (1100) of providing a floating structure (100) including a keel (300) having negative buoyancy suspended by a suspender (400) at a first position (1001) below a floater (200) having positive buoyancy; the act (1150) of arranging the suspender (400) to connect the keel (300) and the floater (200) in a statically determined manner to form a substantially dynamic unit; the act (1200) of positioning the keel (300) at a second position (1002) while substantially maintaining the suspender (400) in a tensioned state (1210); and including.

[0091] Aspect 2. The method (1000) according to aspect 1, wherein the act (1100) of providing the suspender (400) includes the step (1200) of providing a passive suspender (420) and an active suspender (440) that engage at substantially the same connection points (450I; 452I) and separate connection points (450II, 450III; 454II, 454III) on each of the floater (200) and the keel (300), the passive suspender being configured to have a fixed length and the active suspender being configured to have an adjustable length.

[0092] Aspect 3. The method (1000) according to aspect 2, wherein the act of positioning (1200) is performed by operably adjusting the length of the active suspender (440) while always substantially maintaining the active suspender (440) in a tensioned state during the positioning (1200).

[0093] Aspect 4. The method (1000) according to embodiment 2 or 3, wherein the passive suspension (420) and the active suspension (440) at one end (410A) engage at substantially the same connection points (450I; 452I) and separate connection points (450II, 450III; 454II, 454III) on their respective floaters (200) and keels (300).

[0094] Embodiment 5. The floater (200) can be substantially a floater triangle (233), the keel (300) is substantially a keel triangle (333), and the positioning act (1200) is a transfer position (1510) that forms substantially a single triangle when the floater triangle (233) and the keel triangle (333) are superimposed, and a deployment position (1710) that forms substantially a star when the triangle of the floater (233) and the triangle of the keel are superimposed, The method (1000) according to any one or two or more of embodiments 1 to 4, which is performed at the above positions.

[0095] Embodiment 6. The positioning act (1200) is performed by operating the suspension (400) using one or more winches (500) arranged on the floating structure, and the method (1000) according to any one or two or more of embodiments 1 to 5.

[0096] Embodiment 7. The positioning act (1200) can be performed by operating the suspension (400) using one or more winches (500) arranged on one or more ships (700), and the method (1000) according to any one or two or more of embodiments 1 to 5.

[0097] Embodiment 8. The act of positioning (1200) is the method (1000) according to aspect 7, which is performed on a ship (700; 700I, III) each having a winch (500; 500I, II, III) that operates an active suspender (440; 440I, II, III) at each floater node (220; 220I, II, III) of the floater (200) in order to position the keel (300).

[0098] Aspect 9. The act of positioning (1200) is the method (1000) according to aspect 7, which is performed by a single ship (700) that operates an active suspender (440; 440I, II, III) at each floater node (220; 220I, II, III) of the floater (200) in order to position the keel nodes (320; 320I, II, III) step by step, one by one.

[0099] Aspect 10. The act of positioning (1200) is the method (1000) according to aspect 7, which is performed on a single ship (700) including a plurality of winches (500; 500I, II, III) that each operate an active suspender (440; 440I, II, III) connected to each keel node (320; 320I, II, III) in order to position the keel (300).

[0100] Aspect 11. The act of positioning (1200) is the method (1000) according to aspect 7, which is performed on a single ship (700) having a single winch (500) that operates a plurality of active suspenders (440; 440I, II, III) connected to each keel node (320; 320I, II, III) in order to position the keel (300).

[0101] Aspect 12. A floating structure (100), A floater (200) configured to have positive buoyancy such that a suspender (400) is suspended at the other end (410B) at one end (410A), A keel (300) configured to have negative buoyancy, comprising The floating structure (100) includes a passive suspension (420) configured with a fixed length and an active suspension (440) configured to adjust the length. The passive suspension (420) and the active suspension (440) at one end (410A) engage at substantially the same connection point (450I; 452I) and engage at separate connection points (450II, 450III; 454II, 454III) at the other end (410B) on their respective floaters (200) and keels (300).

[0102] Aspect 13. The keel (300) of the floating structure can be formed as a keel polygon (330) having a keel element (310) including a negative buoyancy element connected at a keel node (320), and the floater (200) can be formed as a floater polygon (230) having a floater element (210) including a positive buoyancy element connected at a floater node (220). The floating structure (100) according to aspect 12

[0103] Aspect 14. The floater (200) is formed as a tetrahedral structure (240), the floater base (212) includes a buoyancy element connected at a floater node (220), the apex (240) is configured to support a wind turbine tower (122), and the keel (300) is formed as a keel triangle (333) formed substantially complementary to the floater base (212). The floating structure (100) according to aspect 12 or 13

[0104] Aspect 15. The floating structure is the floating structure (100) according to any one of aspects 12 to 14, wherein at least one active suspension (440) in the floating structure is operably connected to at least one winch (500).

[0105] Aspect 16. A floating structure (100) according to any one or two or more of aspects 12 to 15, comprising a computing unit (600) configured to perform an action according to any one or two or more of aspects 1 to 11.

[0106] Embodiments of the present invention will be described with reference to the drawings.

Brief Description of the Drawings

[0107]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

[0108] Part Number Item 100 Floating structure 110 Sea surface 120 Wind turbine generator (WTG) 122 Tower 200 Floater 210 Floater element 212 Floater base 220 Floater node 230 Floater polygon 233 Floater triangle 240 Tetrahedral structure 242 Vertex 300 Keel 310 Keel element 320 Keel node 330 Keel polygon 333 Keel triangle 400 Suspender 410 Suspender end 420 Passive suspender 440 Active suspender 450 Connection point 452 Floater connection point 454 Keel connection point 460 Suspender guide 470 Transfer line 500 Winch 510 Winch support 520 Yaw gear 530 Yaw ring 540 Yaw clamp 550 Drum 600 Computer unit 700 Vessel 710 Damper / Bumper 1000 Positioning of the keel 1001 First position 1002 Second position 1100 Provide 1150 Arrange 1200 Positioning 1210 Hold 1500 Transfer 1510 Transfer position 1600 Install 1610 Installation position 1700 Deploy 1710 Deployment position

DETAILED DESCRIPTION OF THE INVENTION

[0109] FIG. 1 shows a floating structure 100 including a floater 200 and a keel 300. The keel 300 is suspended by a suspender 400. As an example, the floating structure 100 is configured to support a tower 122 of a wind turbine generator 120. The position of the keel 300 is here at the deployment position 1710.

[0110] The principles disclosed herein are general, but for purposes of illustration, the floating structure 100 is shown relative to the sea surface 110. Optional anchor lines are shown extending toward the seabed (not shown).

[0111] Generally, the figures relate to a method of positioning a keel of a floating structure between a first position 1001 and a second position 1002 that maintain the structure in a statically determined manner such that the first position 1001, the second position 1002, and the floating structure form a substantially dynamically unitary body between the first and second positions 1001, 1002.

[0112] There is an act of providing a floating structure 100 having a keel 300 with negative buoyancy suspended by a suspender 400 at a first position 1001 below a floater 200 having positive buoyancy. There is an act of arranging a suspender 400 to connect the keel 300 and the floater 200 in a statically determined manner so as to form a substantially dynamically unitary body, and an act of positioning the keel 300 at a second position 1002 while keeping the suspender 400 substantially taut.

[0113] As described above, the first position 1001 or the second position 1002 can be, for example, a transfer position, an installation position, or a deployment position. The positions depicted are the deployed position 1710 or the anchor position.

[0114] FIG. 2 is a view showing the floating structure 100 in top view A and perspective view B.

[0115] FIG. 3 is a view for explaining the details of the floating structure 100 in the perspective view from FIG. 2B.

[0116] Referring to FIG. 1, the floating structure 100 has keels 300 at different positions. This position represents the position of the keel 300 during deployment.

[0117] The floating structure 100 includes a float 200 configured to have positive buoyancy. There is a keel 300 configured to have negative buoyancy.

[0118] The float 200 suspends the keel 300 via a suspender 400.

[0119] The suspender 400 includes a passive suspender 420 configured such that its length is fixed, and an active suspender 440 configured such that its length is adjustable.

[0120] In this case, the suspender end 410A is connected to the float 200, and the suspender end 410B is connected to the keel 300. FIG. 3 shows that the active suspender 440 is connected to the connection point 450A of the float 100 at the suspender end 410A, and the opposite suspender end 410B is connected to the connection point 450B of the float 200.

[0121] As can be seen in FIGS. 2 to 3 and further in FIG. 4, the passive suspender 420 and the active suspender 440 at one end 410A engage at substantially the same connection points 450I; 452I, and the other end 410B engages at separate connection points 450II, 450III; 454II, 454III of the respective floaters 200 and keels 300.

[0122] In this case, the active suspender 440 and the passive suspender 420 are connected to the same point or the same floater node 220. The floater 200 is shown as a floater polygon 230 and more specifically as a floater triangle 233. The floater triangle 233 has floater nodes 220I, II, III (clockwise when viewed from above). The floater 200 has a floater base 212 formed as a floater polygon 230, that is, a floater triangle 233, and floater elements 210 including positive buoyancy elements are connected at the floater nodes 220.

[0123] The keel (300) is formed as a keel polygon (330) having a keel element (310) including a negative buoyancy element connected at a keel node (320). The keel polygon 330 is here formed as a keel triangle 333 having nodes 320I, II, III, and by this numbering, the floater nodes 220 and the keel nodes 320 correspond, and the corresponding keel nodes 320 are positioned directly below the floater nodes 220 at the transfer position 1510 (see FIG. 2).

[0124] In this particular configuration, FIG. 2 shows an embodiment in which the floater (200) is formed as a tetrahedral structure (240) including a buoyancy element connected at the floater base (212) at the floater nodes (220). The vertices (242) of the tetrahedral structure 240 are configured to support the wind turbine tower (122). The keel (300) is formed as a keel triangle (333) formed complementary to the floater base (212), as can be seen in FIG. 2A.

[0125] The perspective view of FIG. 4A and the top view of FIG. 4B show the same floating structure 100 as in FIG. 2 and are shown in detail in FIG. 3. The keel 300 is positioned at 1000.

[0126] FIG. 4A is a diagram for explaining the arrangement of the suspenders 400. In the example, the passive suspender 420 and the active suspender 440 engage at substantially the same connection points 450I; 452I on their respective floaters 200 and keel 300, and at separate connection points 450II, 450III; 454II, 454III.

[0127] In the example, for the floater node 220I: there is an active suspender 440I-I (connecting the floater node 220I and the keel node 320I). The active suspender 440I-I is connected to the floater node 220I at the floater connection point 452I and is connected to the keel connection point 454I. It can be seen that the keel connection point 454I is connected to the keel element 310I-III (connecting the keel node 320I and the keel node 320III) at the end towards the keel node 320I. The corresponding passive suspender 420 is the suspender 420III-I (connecting the floater anode 220III and the keel node 320I). The passive suspender 420III-I is connected at the floater connection point 452III in a way that is seen as the floater connection point 452I for the floater node 220I, and is connected by the keel element 310II-I (connecting the keel node 320II and the keel node 320I) at the end towards the keel node 320II.

[0128] It can be seen that the floater has the connection point 450 as the floater connection point 452 in a specific floater node structure. Such an equivalent floater node structure can be applied to the keel node. Also, it can be seen that the floater node 220I is the same connection point 452I for the passive suspender 420I-II connecting to the keel node 320II and the active suspender 440I-I connecting to the keel node 320I separated from the keel node 320II.

[0129] In this way, the floater triangle 233 suspends the keel triangle 333 by the suspender 440 that is operably arranged according to the above numbering.

[0130] The floater node 220I has the same connection point 452I for the passive suspender 420I-II connecting to the keel node 320II and the active suspender 440I-I connecting to the keel node 320I separated from the keel node 320II.

[0131] The floater node 220II has the same connection point 452II for the passive suspender 420II-III connecting to the keel node 320III and the active suspender 440II-II connecting to the keel node 320II separated from the keel node 320III.

[0132] The floater node 220III has the same connection point 452III for the passive suspender 420III-I connecting to the keel node 320I and the active suspender 440III-III connecting to the keel node 320II separated from the keel node 320I.

[0133] Also, the following can be understood.

[0134] The keel node 320I has the same connection point 454I for the passive suspender 420III-I connecting to the floater node 220III and the active suspender 440I-I connecting to the floater node 220I separated from the floater node 220III.

[0135] The keel node 320II has the same connection point 454II for the passive suspender 420I-II connecting to the floater node 220I and the active suspender 440II-II connecting to the floater node 220II separated from the floater node 220I.

[0136] The keel node 320III is the same as the connection point 454III of the passive suspender 420II-III connected to the floater node 220III and the active suspender 440I-I connected to the floater node 220I separated from the floater node 220III.

[0137] The resulting grid structure is a statically determined substantially single rigid body that is maintained while the suspenders remain in tension while the keel 300 is positioned 1000. The keel 300 shown here is at approximately one-third of the position from the transfer position 1510 (from FIG. 2) and the deployment position 1710 (see, for example, FIG. 9).

[0138] FIG. 5 is a view showing an embodiment of the suspender 400 of the floating structure 100 at the positioning 1000 when applying a winch arranged on a ship. The passive suspenders 420I, II, III and the active suspenders 440I, II, III are shown. In particular, the guidance of the active suspender 440 is shown. The suspender 440 can be "rotated or oriented" by a suspender guide 460 arranged in an array along a desired suspender path. In this embodiment, the suspender guide 460 is arranged on the floater 200 so that the active suspender 440 can be substantially operable in place.

[0139] The active suspender 440III can follow the floater node 220III from an operable location and be connected to the keel node 320III. The same applies when the active suspenders 440II, 440I position the respective keel nodes 320II, 320I.

[0140] The floating structure 100 can be configured with a suspender guide 460 to accommodate one or more alternative suspender paths for alternative operating modes. The suspender guide can be selected from a plurality of readily available chucks and bits depending on the purpose.

[0141] FIG. 6 is a diagram showing an aspect of a winch 500 that operates an active suspension 440 (not shown). The winch 500 includes a winch support 510 that engages a yawing 530 to rotate a drum 550 and supports an arrangement of a plurality of gears or motors 520 here.

[0142] The winch support 510 can be configured to be arranged on a floating body or on a ship as shown.

[0143] FIG. 7 is a diagram showing operating the active suspension 440 using the winch 500 on the floating structure 100.

[0144] FIGS. 7A and B are diagrams showing the apex 242 of the floating structure 100 that supports the wind turbine generator tower 122. The floating structure 100 is composed of a winch 500 in which a winch support 510 is fixed to the floating structure 100 and supports a drum 550 and a plurality of gears 520.

[0145] FIG. 7C is a diagram showing the winch 500 arranged toward the top 242 and operated by inhauling from the platform at the top 242. The active suspension 440 extends from the winch 500 along the legs of the tetrahedral structure 240 to the suspension guide 460 of the floater node 220 and further toward a keel connection point 454 (not shown).

[0146] FIG. 8 is a diagram showing the installation of the winch 500 on the floating structure 100. The winch 500 can be supplied via a ship 700 and hoisted to be installed on the floating structure 100. In this way, the floating structure 100 can be prepared to receive one or more winches 500 that can be temporarily installed when arranging the keel 300 (not shown).

[0147] Figures 9 and 10 show the positioning 1000 of the keel by operating the active suspenders 440I, II, III respectively arranged on the single ship 700. For simplicity, the passive suspender 420 is not shown.

[0148] The ship 700 holds three individually controllable winches 500I, II, III. The first winch 500I operates the first active suspender 440I guided to the first floater node 220I of the floater 200 and connects to the first keel node 320 on the keel 300. For the triangular floater 233 and keel 333, the respective paths of the suspenders 440I, II, III are shown. The vessel 700 is located at the center of the floater leg opposite the floater node 220II, and it is observed that a force perpendicular to the floater leg connecting the opposite floater node 220II is generated. The damper 710 can be applied on the floater leg. Also, the other two active suspenders 440III, I are directly led from their respective floater nodes 220III, I to their respective winches 500III, I on the ship 700, and it can be seen that they provide a force parallel to the resulting force from the active suspender line 440II.

[0149] This arrangement enables the use of only a single ship and applies or distributes the operating force to the floating structure 100 in a manageable way during the positioning 1000 of the keel 300.

[0150] Figure 10A details the arrangement of the active suspenders 440 from each winch 500 on the ship 700 engaged with the floating structure 100 via the damper 710 during positioning 1000. In particular, the discussion of the floating connection point 452 on the floater node 220 is shown. By way of example, the active suspender 440III operated by the winch 500III goes directly to the floater connection point 452III of the floater node 220III and is seen to connect from there to the keel node 320III at the keel connection point 454III placed at the end of the keel element 310III-I towards the keel node 320III.

[0151] Figure 10B is a view showing the engagement of the ship 700 and the floating structure 100 via the damper 710 and the active suspenders 440 entering the ship 700. For the sake of simplification, the passive suspenders 420 are not shown.

[0152] Figure 10C details the arrangement of the winches 500I, II, III on a single ship 700.

[0153] Positioning 1200 is carried out on a single ship 700 equipped with a plurality of winches 500; 500I, II, III, each of which operates the respective active suspenders 440; 440I, II, III connected to the respective keel nodes 320; 320I, II, III for the positioning 1200 of the keel 300. The keel nodes 320I, II, III may be positioned simultaneously or can perform stepwise positioning.

[0154] Figure 11 details the arrangement of the active suspenders 440 from each winch 500 on the ship 700 of the floating structure 100 during the positioning 1000 of the keel by operating the individual suspenders using the winches arranged on one ship 700I, II, III for each respective ship, i.e., floating nodes 220I, II, III.

[0155] The positioning 1000 of the keel is performed by the ships 700I, II, III operating the active suspenders 440I, III at each floater node 220I, II, III of the floater 200 for the positioning 1200 of the keel nodes 320I, II, III simultaneously or stepwise with the positioning of the keel 300.

[0156] In the illustrated embodiment, the first ship 700I supports the first winch 500I, and the first ship engages with the floating structure 100 at the first floating node 220I. The first active suspender 440I is directly operated by the first winch 500I to the first keel node 330I. The second and third keel nodes 320II, III are operated similarly.

[0157] Figure 11A shows the positioning 1000 of the keel 300 immediately after the transfer position 1510, and Figure 11B shows the positioning 1000 of the keel in the vicinity of the deployment position 1710.

[0158] Figures 12A and B are views showing a single ship 700 in which the winch 500 operates or positions 1000 the keel node 320 at the floater node 220 by means of the suspender 440. It can be seen that the suspender is kept in a tensioned state. Also, in Figure 12A, the transfer line 470 can be seen. The transfer line 470 is kept in a tensioned state. The positioning 1000 of the keel 300 is carried out by a single ship 700 operating the active suspenders 440I, II, III at each floater node 220I, II, III of the floater 200 to position 1200 the keel nodes 320I, II, III stepwise one by one.

[0159] Figures 13A and B show a floating structure 100 configured with active suspenders 440 having operating ends arranged to be operated by a single winch 500 (not shown). The floater nodes 220I, II, III and the keel nodes 320I, II, III are as described in the previous figures.

[0160] Positioning 1200 is performed by operating a plurality of active suspenders 440I, II, III connected to respective keel nodes 320I, II, III with a single winch 500 on a single ship 700 to position the keel nodes 320I, II, III simultaneously at 1200, thereby positioning the keel 300.

[0161] The active suspenders 440I, II, III are shown in FIG. 10A to have a common connection to a single winch 500 that is substantially at the sea surface or within the plane of the float 200. The active suspenders are guided at the legs of the float base 212 or substantially at the center of the float element 210II-I.

[0162] The active suspenders 440I, II, III are shown in FIG. 10B to have a common connection to a single winch 500 at the sea surface or in the plane of the float 200. The active suspenders 440I, II, III are guided along the legs of the tetrahedral structure 240. The path and the uniform force applied by the winch 500 are evenly distributed along the legs of the tetrahedral structure 240, here distributed from around the apex 242.

[0163] FIG. 14 shows a positioning method of a method 100 (not shown) for positioning the keel 1000 of a floating structure.

[0164] The method includes the act (1100) of providing a floating structure 100 including a keel 300 suspended from a float 200 by a suspender 400, as can be easily identified as an example of the previous figure.

[0165] The method includes the act 1000 of positioning the keel 300 and, on the one hand, the act 1210 of keeping the suspender 400 substantially in a taut state or under tension. The suspender may always be kept in a taut state or under tension, or at least, can be done in an intended or controlled manner.

[0166] As illustrated in the previous figure, the suspender 400 can be provided as a passive suspender 420 and an active suspender 440 that engage at substantially the same connection points 450I; 452I and separate connection points 450II, 450III; 454II, 454III on each of the floaters 200 and the keel 300, respectively.

[0167] The act of positioning 1200 can be performed by operatively adjusting the length of the active suspender 440 while always keeping the active suspender 440 substantially in a tensioned state during the positioning 1200.

[0168] As illustrated in the previous figure, the positioning method 1200 can be performed by operating a configuration in which one end 410A of the passive suspender 420 and the active suspender 440 engages at substantially the same connection points 450I; 452I, and the other end 410B engages at separate connection points 450II, 450III; 454II, 454III on each of the floaters 200 and the keel 300, respectively.

[0169] FIG. 15 is a diagram for explaining a method of positioning the keel 300 during one or more of the acts of transfer 1500, installation 1600, and deployment 1700.

[0170] The act of transfer 1500 can be performed with the keel 300 in the transfer position 1510, as illustrated in the previous figure. The transfer mode or position 1510 may be a state where the inertia of the floating structure is relatively low.

[0171] The act of installation 1600 can be performed by placing the keel at the installation position 1610, as illustrated as the intermediate position of the keel in the previous figure. The installation mode or position 1610 can be made to have an intermediate but intended inertia according to the installation stage and the inertia of the structure supported by the floating excitation structure, for example, the assembled wind turbine generator.

[0172] The unfolding act 1700 can be performed with the keel 300 in the unfolded position 1710, as illustrated in the previous figure. The unfolded mode or position 1710 may be a state where the inertia of the floating structure is relatively high.

[0173] Referring to the previous figure, the floater 200 may be substantially a floater triangle 233, and the keel 300 may be substantially a keel triangle 333. The act 1200 of positioning the keel 300 is performed at the transfer position 1510 that substantially forms one triangle when the floater triangle 233 and the keel triangle 333 are overlapped, as shown in FIG. 2 for example.

[0174] The act of positioning 1000 can be up to the deployment position 1710 that substantially forms a star when the floater triangle 233 and the keel triangle 333 are overlapped, as shown in FIGS. 3 and 9 for example.

[0175] The positioning act 1000 can be for the installation position 1610 where the floater triangle 233 and the keel triangle 333 are at an intermediate position between the transfer position 1510 and the deployment position 1710, as illustrated in FIGS. 4 and 5 for example.

[0176] Referring to the figures described above, embodiments of the method include the following. A method of installing an offshore floating structure, The floating structure 100 includes a floater 200 having positive buoyancy, a keel 300 having negative buoyancy, and a suspender 400 connecting the keel 300 and the floater 200 to each other (FIG. 1), The floater 200 has a plurality of floater nodes 220 arranged in a polygonal configuration including a first floater node 220I, a second floater node 220II, and a third floater node 220III, and the keel 300 has a corresponding number of keel nodes 320 arranged in a polygonal configuration including a first keel node (320I), a second keel node 320II, and a third keel node 320II (FIGS. 2a and b), The above-mentioned suspenders 400 are provided in a corresponding number of suspender pairs, each of the above pairs including a passive suspender 420 and an active suspender 440 (Figure 4a), each of the above active suspenders 440 connects only one floater node 220 to one keel node 320, the above first floater node 220I and the above first keel node 320I are connected by a first active suspender 440I-I, the second floater node 220II and the second keel node 320II are connected by a second active suspender 440II-II, and the third floater node 220III and the third keel node 320III are connected by a third active suspender 440III-III (Figure 4A), each of the above passive suspenders 420 connects only one floater node 220 to one keel node 320, the above first floater node 220I and the above second keel node 320II are connected by a first passive suspender 420I-II, the above second floater node 220II and the above third keel node 320III are connected by a second passive suspender 420II-III, and a third passive suspender 420III-I connects the above third floater node 220III to a keel node 320I adjacent to the above second keel node 320II, and the adjacent keel node is the above first keel node 320I when the keel has only three keel nodes 320), and the method includes suspending the above keel 300 by the above suspenders 400 at a first position 1001 at a first depth in the water below the above floater 200 (Figure 1). The method is changing the vertical distance between the above floater 200 and the above keel 300 from the above first position (1001) at the above first depth in the water to a second position 1002 at a second depth by changing the lengths of all the above active suspenders 440, while substantially maintaining the suspenders 400 in a tensioned state in step 1210, and By maintaining each of the passive suspenders 420 of fixed length at a fixed distance between the connection point on the floater and the connection point on the keel, causing relative rotation of the keel 220 with respect to the floater 300 about a vertical axis, including.

[0177] The keel 300 is formed as a polygon 330 having keel elements 310 including negative buoyancy elements connected at keel nodes 320, and the floater 200 can be formed as a polygon 230 having floater elements 210 including positive buoyancy elements connected at floater nodes 220.

[0178] The floater, according to some embodiments, has only three floater nodes 220 arranged as a triangle and from which the suspender 400 extends to the keel node 320, and the keel 300 can have only three keel nodes (320) arranged as a triangle and from which the suspender 400 extends to the floater 220.

[0179] The floater 200 can be formed substantially as a floater triangle 233, and the keel 300 is formed substantially as a keel triangle 333 of complementary shape, where the method includes transporting the offshore floating structure to the offshore deployment site while forming substantially a single triangle when the floater triangle 233 and the keel triangle 333 are superimposed, and changing to a deployment configuration in which the floater triangle 233 and the keel triangle are rotated relative to each other at the site.

[0180] The floater 200 can be formed as a tetrahedral structure 240 having a floater base 212 with buoyancy elements connected at floater nodes 220, and the apex 240 of the tetrahedral structure 240 supports the wind turbine tower 122.

Claims

1. A method for installing an offshore floating structure, wherein the floating structure (100) comprises a floater (200) having positive buoyancy and a keel (300) having negative buoyancy, and a suspender (400) connecting the keel (300) and the floater (200) to each other, wherein the floater (200) has a plurality of floater nodes (220) arranged in a polygonal configuration, including a first floater node (220I), a second floater node (220II), and a third floater node (220III), and the keel (300) has a corresponding number of keel nodes (320) arranged in a polygonal configuration, including a first keel node (320I), a second keel node (320II), and a third keel node (320II), wherein the suspender (400) is provided in a corresponding number of suspender pairs, each pair including a passive suspender (420) and an active suspender (440), each of the active suspenders (440) connects only one floater node (220) to only one keel node (320), the first floater node (220I) and the first keel node (320I) are connected by a first active suspender (440I-I), the second floater node (220II) and the second keel node (320II) are connected by a second active suspender (440II-II), and the third floater node (220III) and the third keel node (320III) are connected by a third active suspender (440III-III), Each of the passive suspenders (420) connects only one floater node (220) to one keel node (320), the first floater node (220I) and the second keel node (320II) are connected by a first passive suspender (420I-II), the second floater node (220II) and the third keel node (320III) are connected by a second passive suspender (420II-III), and a third passive suspender (420III-I) connects the third floater node (220III) to a keel node (320I) adjacent to the second keel node (320II), and the adjacent keel node is the first keel node (320I) when the keel has only three keel nodes (320). The method includes suspending the keel (300) by the suspender (400) at a first position (1001) at a first depth in the water below the floater (200). The method is Step (1210) of substantially maintaining the suspender (400) in a tensioned state while changing the vertical distance between the floater (200) and the keel (300) from the first position (1001) at the first depth in the water to a second position (1002) at a second depth by changing the lengths of all the active suspenders (440). Step of causing relative rotation of the keel (220) with respect to the floater (300) about the vertical direction by maintaining each of the passive suspenders (420) of fixed length at a fixed distance between the connection point on the floater and the connection point on the keel. A method comprising. Claim 2 The method (1000) according to claim 1, wherein the keel (300) is formed as a polygon (330) having a keel element (310) including a negative buoyancy element connected at the keel node (320), and the floater (200) is formed as a polygon (230) having a floater element (210) including a positive buoyancy element connected at the floater node (220). Claim 3 The method (1000) according to claim 1, wherein the float has only three float nodes (220) arranged as a triangle and from which the suspender (400) extends to the keel node (320), and the keel (300) has only three keel nodes (320) arranged as a triangle and from which the suspender (400) extends to the float (220).

4. The float (200) is substantially formed as a float triangle (233), and the keel (300) is substantially formed as a keel triangle (333) having a complementary shape. The method comprises transferring the offshore floating structure (100) to an offshore deployment site while substantially forming a single triangle when the float triangle (233) and the keel triangle (333) are superimposed; at the site, changing to a deployment configuration in which the float triangle (233) and the keel triangle are rotated relative to each other. The method (1000) according to claim 3, comprising the above steps.

5. The float (200) is formed as a tetrahedral structure (240) having a float base (212) including buoyancy elements connected at the float nodes (220), and the apexes (240) of the tetrahedral structure (240) support the wind turbine tower (122). The method according to claim 1.

6. The act of positioning (1200) is performed by operating the suspender (400) using one or more winches (500) arranged on the floating structure (100). The method (1000) according to claim 1.

7. The act of positioning (1200) is performed by operating the suspender (400) using one or more winches (500) arranged on one or more ships (700). The method (1000) according to claim 1.

8. The act of positioning (1200) is performed by ships (700; 700I, II, III) each having a winch (500; 500I, II, III) for operating an active suspender (440; 440I, II, III) at each float node (220; 220I, II, III) of the float (200) to position the keel (300). The method (1000) according to claim 7.

9. The act of said positioning (1200) is performed by a single ship (700) that operates active suspenders (440; 440I, II, III) at each floater node (220; 220I, II, III) of said floater (200) to position (1200) said keel node (320; 320I, II, III), the method (1000) according to claim 7.

10. The act of said positioning (1200) is performed using a single ship (700) that includes a plurality of winches (500; 500I, II, III) each operating an active suspender (440; 440I, II, III) connected to a respective keel node (320; 320I, II, III) to position (1200) said keel (300), the method (1000) according to claim 7.

11. The act of said positioning (1200) is performed by a single ship (700) having a single winch (500) that operates a plurality of active suspenders (440; 440I, II, III) connected to respective keel nodes (320; 320I, II, III) to position (1200) said keel (300), the method (1000) according to claim 7.

12. The method according to claim 1, wherein the support structure is an offshore support structure for a wind turbine.

13. Use of the method according to any one of claims 1 to 12 for installing a support structure of a wind turbine in an offshore state.

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