Method for maintaining a wind tower by an auxiliary floating system

Abstract

The present invention relates to a method for maintaining a marine structure (2), said structure (2) comprising a wind turbine (20) and at least a substantially vertical axis (4). The method comprises the use of an auxiliary floating system (1), said auxiliary floating system (1) comprising: at least one floating element (5), said at least one floating element (5) remaining semi-submerged during the maintenance of the marine structure (2); at least one coupling structure (7), said at least one coupling structure (7) connecting the system (1) to the floating structure (2); and contact elements (9') and tensioning elements (9), said contact elements and tensioning elements being fixed to the coupling structure (7) and being intended to firmly connect the system (1) to the axis (4). Advantageously, this firm connection allows operations for maintaining the marine structure (2) to be carried out in a manner that is effective and safe for the maintenance staff involved in the operations and for the system.

Description

Field of the Invention

[0001] The present invention mainly relates to a method for maintaining an offshore tower using an auxiliary floating system, for example for maintaining an offshore wind turbine tower. Therefore, the main application field of the present invention is the civil construction industry, and particularly the tower and / or infrastructure construction and maintenance industry, and an industry combined with green or renewable, more specifically offshore wind energy. Background Art

[0002] In the field of offshore wind energy, the maintenance tasks of wind turbines (commonly referred to as "major corrective" maintenance) have a huge economic impact and importance, which require cranes to lift or lower heavy components of wind turbines located at extremely high heights (about 100 meters or higher).

[0003] Currently, the above-mentioned "major corrective" operations of offshore wind turbines are almost entirely carried out by lifting vessels, which are vessels equipped with legs that support on the seabed for lifting the hull of the vessel. Therefore, the crane incorporated in the actual vessel can operate and is hardly affected by the movement of the sea. However, these vessels are very scarce and costly, so they greatly increase the maintenance costs of offshore wind farms.

[0004] A far more cost-effective solution known in the art for operating a crane in marine construction is a solution based on using a conventional land crane on a barge or a floating bridge. However, in the case of offshore wind turbines, this option is not feasible. Because the working height is extremely high, the movement of the barge supporting the crane is multiplied at the end of the boom, which must operate at a specific height of the wind turbine, making the operation of the crane impracticable even under very favorable conditions regarding sea conditions. When the support structure of the wind turbine is not fixed but floating, the above problems become even more serious.

[0005] The present invention aims to overcome these limitations and disadvantages of known systems in the operation of maintaining marine structures through a novel auxiliary floating system and its corresponding usage method, which has the potential to eliminate the relative movement between the floating element supporting the maintenance crane and the marine structure supporting the wind turbine to be maintained. Summary of the Invention

[0006] To overcome the disadvantages of the prior art described above, the object of the present invention is to provide a method for maintaining a marine structure (such as a wind turbine tower) using an auxiliary floating system, wherein the marine structure is floating or non-floating, and wherein the system allows the maintenance operation to be optimized relative to known systems.

[0007] The object is preferably carried out by a method for maintaining a wind turbine supported on an offshore structure and comprising a shaft and / or a base, the offshore structure being capable of floating or being fixed to the seabed. The invention is particularly applicable to operations for maintaining components at very great heights, preferably by means of a crane. The invention also allows the limitations of known barge or floating crane systems to be overcome in operations in which the degrees of freedom of movement of said systems are a drawback or even not advisable, for example in the case of operations for maintaining wind turbines.

[0008] Advantageously, the method according to the invention comprises the use of an auxiliary floating system, which auxiliary floating system comprises:

[0009] - one or more floating elements.

[0010] - at least one crane located on at least one of said floating elements.

[0011] - at least one work area for the storage and / or repair of components of the wind turbine and / or of the offshore structure.

[0012] - at least one connection structure for connection to the offshore structure, wherein said connection structure in turn comprises:

[0013] - a hinged closing ring adapted to close around an element of the offshore structure (preferably the shaft or the tower), although it can also close on other elements of the base without departing from the scope of the invention.

[0014] - a plurality of contact elements located between the connection structure and the offshore structure. In a preferred embodiment, at least three contact elements are arranged at a higher level and at least three other contact elements are arranged at a lower level such that a torque is generated between the reaction forces of the upper-level elements and the reaction forces of the lower-level elements and thus the transmission of torque between the elements of the connection structure and the offshore structure to which the connection structure is connected is facilitated.

[0015] - one or more tensioning elements allowing the position of the contact elements to be adjusted, said tensioning elements being adapted to apply a tensioning force to the offshore structure via the contact elements.

[0016] Preferably, the connection structure for connection to the offshore structure can adopt at least three configurations:

[0017] - an open configuration, in which the closing ring is open.

[0018] - a closed configuration, in which the closing ring is closed.

[0019] - A tensioning configuration, in which the closed loop is closed and the tensioning element is arranged to apply a tensioning force to the marine structure.

[0020] Furthermore, the method of the present invention comprises performing the following steps in any technically possible order:

[0021] a) Floatingly transporting the auxiliary floating system to the location of the marine structure.

[0022] b) Bringing the auxiliary floating system close to the marine structure, wherein the coupling structure is in an open configuration.

[0023] c) Arranging the coupling structure in a closed configuration such that the closed loop completely surrounds an element of the marine structure.

[0024] d) Acting on the tensioning element in a controlled manner to arrange the coupling structure in a tensioning configuration such that the marine structure and the auxiliary floating system are firmly connected with six degrees of freedom of movement (pitching, surging, heaving, yawing, rolling and swaying).

[0025] e) Performing maintenance tasks on the wind turbine and / or the marine structure using a crane.

[0026] f) Using the working area of the auxiliary floating system to store and / or repair components of the wind turbine and / or the marine structure.

[0027] g) Uncoupling the auxiliary floating system from the marine structure so as to arrange the coupling structure in an open configuration.

[0028] In a preferred embodiment of the method of the present invention, the auxiliary floating system comprises a plurality of floating elements which are connected to each other and / or to the coupling structure.

[0029] In another preferred embodiment of the method of the present invention, the auxiliary floating system comprises a single floating element in the form of a barge, in which both the crane and the working area are arranged, and wherein the barge is formed by a single body or by the attachment of several modules connected to each other. In this second case, the barge can be formed by a unique module which is specifically designed such that it comprises the coupling structure and standard or commercially available barge modules are coupled to the unique module to complete the barge with the required area. Thus, cost economy is achieved due to the minimization of the number of specific elements of the system; and the complementary use of standard modules of barges known in the art is allowed.

[0030] In another preferred embodiment of the method of the present invention, the crane is a telescopic and / or folding crane, and the crane is deployed after step d) and refolded again before step g). This possibility is advantageous because it facilitates and / or increases the floating system's floating and untethered (i.e., not coupled to the marine structure) state.

[0031] In another preferred embodiment of the method of the present invention, the working area is at least partially located at a certain distance from the crane, and this distance is greater than the minimum operating radius of the crane. The operating radius of the crane imposes limitations not only in the case of being too far away, but also in the case of being too close (this second case is the most restrictive case because in certain configurations, the crane cannot work with elements that are too close to the crane), and this ultimately imposes a minimum size on the barge. To prevent this from resulting in an extremely large barge whose movement is more difficult to avoid, the present invention contemplates the use of a "free" working area, whose configuration is similar to a configuration where a helipad can have ships or offshore structures that can move away from the crane without thereby increasing the size of the barge and the water surface area. The working area is at least partially free with respect to the floating element, such that at least a part of the area of the working area is not located on the deck of the floating element. The advantage of the free platform is that by its use, it is possible to move the working area of the crane away so that it is outside its minimum working radius without thereby unnecessarily increasing the area of the floating element. Limiting the area in turn allows the stress on the entire system and the marine structure itself to be limited during the connection between the two.

[0032] In another preferred embodiment of the method of the present invention, steps a) and / or b) are carried out by towing an auxiliary floating system, and this towing allows the cost of the auxiliary system to be reduced. However, the auxiliary floating system according to the present invention can also be self-propelled, so that in this case a tugboat is not required for its operation.

[0033] In another preferred embodiment of the method of the present invention, the floating element includes a hydrodynamic damping plate. The main advantage of the plate is its ability to limit floating movement, especially during connection and disconnection steps b), c) and g).

[0034] In another preferred embodiment of the method of the present invention, the floating element is capable of ballasting in a central or eccentric manner. The advantages of eccentric ballasting mainly include offsetting the weight of the crane in a preferred case, in which case the crane is arranged in an eccentric manner that is beneficial for preventing interference with the connection structure and allowing the working area of the crane to be properly moved away so as to keep it outside the minimum working radius of the crane. The eccentric ballasting system also allows other existing eccentric weights (such as the eccentric weight of the connection structure) to be offset.

[0035] In another preferred embodiment of the method of the present invention, the method includes the steps after step d):

[0036] j) Ballast at least one floating element to counteract the rising of the tide and / or unballast at least one floating element to counteract the falling of the tide. Thereby, the forces that must be transmitted through the coupling structure to maintain its firm connection with the marine structure during swaying are reduced. This advantage only applies to the case of a fixed marine structure and not to the case of a floating structure, because if the marine structure to be maintained is floating, then the tide affects the marine structure and the auxiliary floating system equally. Alternatively, the coupling structure can remain in a taut configuration and be firmly connected during swaying only when the crane is operating in step e). Conversely, when the crane is not operating, the coupling structure can release the tension force to move freely during swaying, allowing relative movement between the auxiliary floating system and the marine structure during swaying to accommodate tidal changes.

[0037] In another preferred embodiment of the method of the present invention, the freeboard of the auxiliary floating system is compatible with the tidal range such that when the auxiliary floating system remains connected to a fixed marine structure, the change in the tide never reduces the freeboard to less than 10 cm.

[0038] In another preferred embodiment of the method of the present invention, the auxiliary floating system is equipped with one or more proximity or fixed cables between the system and the marine structure, and the length of the cable is adjusted during the approach step b). These cables will typically be operated by a winch, and this has the advantage of allowing greater control during the operation of bringing the auxiliary floating system close to the marine structure. In a preferred embodiment, the cable is fixed to the marine structure at one end, and its length is adjusted by a winch of the auxiliary floating system. The cable can also, for example, partially surround the axis of the marine structure, and both ends are fixed to the auxiliary floating system.

[0039] In another preferred embodiment of the method of the present invention, a closed loop maintains an internal space sufficient for the connection of the closed loop to the area of the marine structure, which includes a ship landing structure. Thus, interference with the ship landing is prevented during the operation of connecting / disconnecting the system from the marine structure.

[0040] In another preferred embodiment of the method of the present invention, the tensioning element includes:

[0041] A lever that is fixed at a hinge point and is rotatable relative to the hinge point;

[0042] A contact element that is connected to a point of the lever;

[0043] An extendable and / or foldable hydraulic cylinder that is connected to another point of the lever;

[0044] And by actuating the hydraulic cylinder to extend and / or fold it, the lever is caused to rotate, and thereby the position and / or the force applied by the contact element is adjusted.

[0045] In another preferred embodiment of the method according to the invention, the distance between the line of action of the hydraulic cylinder and the hinge point is greater than the distance between the line of action of the contact element and the hinge point, such that by a lever effect, the force F in the hydraulic cylinder generates a force F' in the contact element, which force F' is greater than F.

[0046] In another preferred embodiment of the method according to the invention, the method comprises a step prior to step c):

[0047] k) applying a strengthening device to an element of the marine structure to which the connection structure is connected, such that the marine structure is capable of withstanding these forces, and the auxiliary floating system can introduce the force into the marine structure through the contact element.

[0048] Thus, the system is applicable not only to marine structures previously designed for the system, but also to structures not previously designed for the system and suitably strengthened to withstand these forces, and the connection structure of the auxiliary floating system can transmit these forces.

[0049] In another preferred embodiment, the marine structure is a monopile structure, and the strengthening device comprises the interior of the monopile filled completely or partially with concrete. This filling is preferably carried out in the support area of the contact element with the marine structure, and it can be a complete or annular filling of the interior of the monopile (at two levels horizontally coinciding with the two contact elements (9') of the connection structure (7)). In the case of a monopile equipped with a transition section between the monopile and the wind turbine tower, the strengthening device can be applied in a similar manner to the transition section. This type of strengthening has the advantage of being very easy to implement in existing structures, by simply pouring concrete through the access door of the tower or other suitable passage into the monopile or the transition section, thereby generating a very robust strengthening in a simple and cost-effective manner in the area provided for connecting the auxiliary floating system. In other embodiments, therefore, other strengthening devices known in the art (which can be metallic or of another type) can be used without departing from the scope of the invention.

[0050] In another preferred embodiment of the method according to the invention, the auxiliary floating system comprises: means for controlling and / or monitoring the tension force and / or the position of the tensioning element; and / or means for opening and closing the closed loop. The means for opening and closing the loop can comprise, for example, a hydraulic actuator, one end of which is fixed to the central part of the loop and the other end is fixed to the lateral part of the loop, such that when extended, they push the lateral part to gradually close the loop, and when pulled in, they generate the opposite effect to open the loop.

[0051] In another preferred embodiment of the method of the present invention, the auxiliary floating system comprises a combination of active tensioning elements and passive elements. Within the scope of the present invention, the passive elements are understood to be contact elements lacking tensioning means, but which apply forces to the marine structure in a passive manner as reaction forces. The use of active elements is crucial for being able to adjust the tension force of the connection structure, but the combination with some passive elements can reduce the number of active elements required and thus reduce the cost of the system.

[0052] In another preferred embodiment of the method of the present invention, the contact element comprises a support plate which contacts the marine structure and has a coefficient of friction greater than 3%, such that when the contact element is tensioned against the marine structure, a frictional force is generated which contributes to forming a firm connection between the marine structure and the auxiliary floating system. In particular, when the closed loop surrounds the axis of the marine structure or another vertical element of the marine structure, said friction will be advantageous for transmitting vertical forces and allowing a firm connection during swaying. Thus, during step e) of the method (where the crane is operating), a greater force is applied between the contact element and the marine structure by the tensioning element, thereby generating a frictional force which is sufficient to prevent relative vertical movement. Conversely, when the crane is not operating, said force can be reduced or relaxed, thereby reducing the frictional force and enabling relative vertical movement to accommodate the tide (this only applies to fixed marine structures; it is not necessary in floating marine structures since the tide affects the marine structure and the auxiliary floating system equally).

[0053] In another preferred embodiment of the method of the present invention, the closed loop of the auxiliary floating system comprises a protective device, the position of which is such that during step b) and / or c), the protective device contacts the marine structure before the contact element. Herein, the protective device is understood to be a flexible element which is intended, for example, for damping impacts between two ships or between a ship and a fixed element.

[0054] In another preferred embodiment of the method of the present invention, the crane is a mobile land crane having caterpillars or wheels and supported on at least one floating element. The ability to use a land crane instead of a marine crane for maintaining an offshore wind turbine offers significant cost economies.

[0055] In another preferred embodiment of the method of the present invention, the crane is a mobile land crane, which includes: an upper body including at least one boom, a counterweight, and equipment for actuating the crane; a lower body including means for moving the crane by wheels and / or tracks; and wherein the auxiliary floating system only includes the upper body of the crane. Thus, the weight of the crane is reduced. Additionally, assuming that the crane does not need to move during the method of the present invention, the lower body can be dispensed with. In this embodiment, the auxiliary floating system must include anchoring means for connection of the upper body of the crane. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The foregoing and other features and advantages will be better understood according to the specific embodiments of the present invention and according to the preferred embodiments with reference to the accompanying drawings, in which:

[0057] Figure 1 A top view of the auxiliary floating system and the marine structure is shown.

[0058] Figures 2a to 2b show two detailed views of the tensioning element of the auxiliary floating system of the present invention, wherein in one of the views (Figure 2a), the element is not yet fixed to the marine structure, and in the other view (Figure 2b), the element is fixed to the marine structure, so that the floating system is firmly fixed to the marine structure.

[0059] Figures 3a to 3b show different views of the closed loop of the system of the present invention in its one preferred embodiment, in the open position (Figure 3a) and the closed position (Figure 3b).

[0060] Figure 4 A first preferred embodiment of the system of the present invention is shown, which is applied to the maintenance of a telescopic wind turbine tower.

[0061] Figures 5 to 7 Different views of a second preferred embodiment of the system of the present invention are shown, wherein its floating element is configured in the form of a barge.

[0062] Figure 8 A third preferred embodiment of the present invention is shown, wherein the marine structure is a monopile structure and preferably includes reinforcement means filled completely or partially inside the monopile.

[0063] Figures 9 to 10 Shows corresponding to Figures 5 to 7 Different views of a second preferred embodiment of the system of the present invention, wherein the floating element of the system is configured in the form of a barge.

[0064] List of reference numerals in the figures

[0065] (1) Auxiliary floating system (2) Marine structure (3) Base (4) Shaft (5) Floating element (6) Connecting element (7) Coupling structure (8) Closed loop of the coupling structure (9) Tensioning element (9’) Contact element (10) Lever (11) Hydraulic cylinder (12) Operating crane (13) Working area (14) Hinge point (15) Reinforcement device (20) Wind turbine Detailed implementation manners

[0066] Based on the present disclosure Figures 1 to 10 , the detailed implementation manners of the present invention with reference to its different preferred embodiments are explained below. The description is provided to illustrate but not limit the claimed invention.

[0067] Figure 1 A top (plan) view of the auxiliary floating system (1) of the present invention and the marine structure (2) is shown. The marine structure (2) supports a wind turbine (20), wherein the marine structure (2) includes a base (3) and a tower or shaft (4). In this embodiment, the auxiliary floating system (1) includes at least one floating element (5) (i.e., in the Figure 1 example shown, three elements (5) are shown). Preferably during the operation for its maintenance, the auxiliary floating system (1) is coupled to the marine structure (2) (although described in certain specific embodiments of the present invention, its use in other methods will also be possible, such as the installation or transportation of the marine structure (1) to its final offshore location).

[0068] The floating elements (5) of the system (1) are connected to a coupling structure (7) by connection elements (6) (e.g., a truss or lattice boom). The coupling structure (7) is preferably designed to surround at least one element of the marine structure (2), e.g., arranged around the shaft (4), such that the contact point or contact area with the coupling structure (7) provides means for a firm fixation to the marine structure (2), so that the floating system (1) maintains its position during the operation. Preferably, the coupling structure (7) forms a closed loop (8) around the shaft (4), and the closed loop (8) can be circular or can have any other closed geometric shape, e.g., curved or polygonal.

[0069] With respect to the contact point or contact area between the connection structure (7) and the marine structure (2), the system of the present invention is equipped with one or more tensioning elements (9), which are fixed to the connection structure (7) and are preferably arranged along a closed loop (8). The tensioning element (9) preferably includes an active actuator (such as a hydraulic cylinder); for example, once the system (1) is connected to the marine structure (2) through the connection structure (7), the active actuator allows a tensioning force to be generated in the marine structure, and thus allows the position of the system (1) to be firmly or quasi - firmly fixed to the marine structure (2). A firm attachment between the connection structure (7) and the marine structure (2) allows relative movement between the two structures to be eliminated or sufficiently restricted. Here, it should be understood that certain aspects (such as elastic deformation of materials) may result in small relative movements, and thus do not depart from the scope of the present invention. In any case, a firm attachment between the connection structure (7) and the marine structure (2) will always allow relative translational movement to be restricted to less than 50 cm, and relative rotational movement to be restricted to less than 2 degrees (roll or pitch) and less than 5 degrees (yaw).

[0070] In the bottom - fixed base (3), the movement of the marine structure (2) is almost zero, and thus a firm or quasi - firm connection is interpreted as meaning that the movement is almost zero for both the marine structure (2) and the connection structure (7). However, in a floating marine structure (2), this does not occur because there is generally movement. In this case, a quasi - firm or firm connection is understood as meaning an almost zero relative movement between the marine structure (2) and the connection structure (7).

[0071] The tensioning element (9) generally includes an active element (such as an arm, which can be deployed by an electromechanical, hydraulic, pneumatic or similar system), which allows the position of the contact element (9') to be adjusted and thus approach the marine structure (2) until contact is made. Thus, the tensioning element (9) also includes a passive element, which is configured as, for example, a stop, which restricts or prevents movement of the marine structure (2) relative to the floating system (1), thus keeping the position of the holder unchanged relative to the closed loop (8).

[0072] Optionally, the system (1) of the present invention may further include a contact element (9'), which is adapted to be used during the step before the tensioning element (9) is fully fixed to the marine structure (2). The contact element (9') may or may not be included in the tensioning element (9) itself, and is preferably adapted to provide a free sliding contact with the shaft (4). Thus, during the step before the tensioning element (9) is firmly assembled to the marine structure (2), the contact element (9') allows a relative vertical movement between the shaft (4) and the auxiliary floating system (1). Therefore, the coupling structure (7) provides a physical stop against changes in the horizontal position of the marine structure (2) through the contact element (9'), thereby also limiting the possible tilts (e.g., due to wind, waves, etc.) that the structure can undergo and contributing to the structure (2) maintaining its stability, but preferably through a sliding contact that allows its free movement along a substantially vertical axis. The free movement of the marine structure (2) can be performed by sliding, by rolling, on caterpillar tracks or any known technique that allows independent and sufficiently free relative movement between the contact elements (9') across the surface of the shaft (4).

[0073] Therefore, the contact element (9') prevents and / or limits other relative movements between the auxiliary floating system (1) and the shaft (4), whether it is a relative horizontal movement (preferably equal to or less than 1 m), a relative rotational movement during rolling and / or pitching (preferably equal to or less than 10 degrees), and a relative rotation during yaw (preferably less than 20 degrees). However, in a novel way of the present invention, the tensioning element (9) is responsible for preventing or limiting the relative vertical movement between the marine structure (2) and the floating system (1) during maintenance operations.

[0074] Similarly, in an embodiment of the present invention in which the marine structure (2) has a ship landing, the geometry of the closed loop (8) allows preventing interference with the ship landing. Therefore, the geometry can be adapted to the shape characteristics of the marine structure (2) to facilitate the fixing of the system (1) thereto, and thus improve maintenance operations.

[0075] Figures 2a to 2b show possible embodiments of the tensioning element (9), wherein the element at least comprises a contact element (9'), which is coupled to a lever (10), and the lever (10) can be actuated by a hydraulic cylinder (11). In this embodiment, once the coupling structure (7) closes onto the shaft (4), the lever (10) is actuated until it contacts the shaft (4), thereby maintaining the aforementioned actuation and the corresponding deployment of the lever (10) until the floating system (1) is firmly coupled to the marine structure (2). In this example, all the tensioning elements (9) can adopt an active configuration (applying a relative force in the form of the lever (10) through the hydraulic cylinder (11)), or a combination of the lever (10) and passive elements can be used, wherein the lever (10) applies a force against the passive elements through the shaft (4). In different embodiments of the present invention, the actuation of the lever (10) can be performed in-situ or by a remote control device. Similarly, the connection between the lever (10) and the hydraulic cylinder (11) can be articulated through one or more hinge points (14).

[0076] In a possible embodiment of the present invention, at least three contact elements (9') are used at a first height of the coupling structure (7), and at least three contact elements (9') are used at a second height of the coupling structure (7). Thus, the closed loop (8) is configured with two support levers, which improves the ability to absorb the torque generated by the relative inclination between the marine structure (2) and the auxiliary floating system (1). Similarly, the loop (8) can have different mechanisms for closing or maintaining its position around the marine structure (2), whether through pin shafts, cooperative attachments, electromechanical systems or any other known devices.

[0077] In the example of Figures 3a to 3b, the coupling structure (7) is formed by a metal lattice structure. In addition, the coupling structure (7) includes an opening and / or closing subsystem (not shown in the figures) to facilitate its placement and / or removal relative to the marine structure (2); and optionally includes one or more actuators for folding and / or deploying the system (1) onto the marine structure (2). The actuators can or cannot be remotely actuated, and in different embodiments, they can include telescopic hydraulic cylinders, which are capable of applying a force when extending and retracting. Alternatively, they can also include different types of devices known in the art, such as mechanical, pneumatic or hydraulic actuators, towing ropes, which are actuated by ropes, winches, etc. The devices for opening and closing the loop (8) can include, for example, hydraulic actuators, which have one end fixed to the central part of the loop (8) and the other end fixed to its lateral part, such that when extended, they push the lateral part to close the loop (8), and when pulled in, they generate the opposite effect to open the loop.

[0078] Figure 3a shows a top or plan view of the closed loop (8) in the open configuration. The closed loop has a central sector and two lateral sectors which are connected to the central sector at respective hinge points. By rotating the lateral sectors at said hinge points, the loop can be arranged in the closed configuration as shown in Figure 3b.

[0079] As described above, the coupling structure (7) is preferably modular or adjustable such that it can be adapted to marine structures (2) and / or shafts (4) of different sizes and / or characteristics without the need to previously modify said structures (2) or provide them with additional devices or substructures. For example, modules can be added to or removed from the lattice booms of the coupling structure (7) to adjust its length and thus its distance to the shaft (4), thereby preventing the shaft (4) itself from having to be altered. In an alternative or complementary manner, the position and / or dimensions of the tensioning elements (9) and / or contact elements (9') can be changed or adjusted such that the same auxiliary floating system (1) can be used for the maintenance of marine structures (2); the marine structures (2) having shafts (4) of different diameters, or shafts (4) having variable diameters or different sections (e.g., hexagonal or circular) and different sizes (e.g., different apothems or diameters).

[0080] As can be seen in Figure 4 the cross-section of Figure 1 In a preferred embodiment of the system (1) of the present invention, the system includes a maintenance operation crane (12) which is preferably arranged in the working area (13) of the system. The position of the maintenance operation crane (12) can be within the floating element (5) itself or in an attached structure installed therefor. The working area (13) will also and preferably be used for the storage and / or repair of components of the marine structure (2) (e.g., components of the turbine or blades of the wind turbine (20)). In different embodiments of the present invention, the working area (13) can be an elevated area and / or a free area relative to the floating element (5).

[0081] Preferably, a land crane (12) which is more cost-effective than a marine crane can be used (understood as a mobile commercially available crane or a crawler crane which is typically used for construction work on land). This is possible as a result of the fact that the firm connection of the floating system (1) to the marine structure (2) limits the movement of the system and facilitates the operation of the crane during maintenance operations, even for working at great heights, as for example occurs in operations for the maintenance of wind turbines (20). In different embodiments, the crane (12) can be a folding and / or telescopic crane, and its firm connection between the floating system (1) and the marine structure (2) ( Figure 5During the steps in between, it will preferably remain folded. Once the connection has been made, the crane can be deployed in a safe manner and thus maintenance tasks at height can be carried out in a safe manner.

[0082] Figures 5 to 7 A second preferred embodiment of the present invention is shown, in which the floating element (5) of the auxiliary floating system (1) incorporates a single support block in the form of a barge, in which both the crane (12) and the working area (13) are arranged. Figure 5 and Figure 6 A front view and a plan view are shown of the case where the crane (12) has a folded telescopic boom. This case is preferred for the phases in which the auxiliary floating system (1) floats separately and is decoupled from the marine structure (2) (for example, step a)). During these phases, the boom and hook of the crane (12) may have temporary elements for fixing to the fixing elements of the auxiliary floating system (1) to mitigate the possible effects of the movement of the system (1) while floating.

[0083] Likewise, in different embodiments of the present invention, the floating element (5) may include hydrodynamic damping plates (for example, rocking plates) to reduce and damp the unwanted movements caused by the waves. Likewise, the floating element (5) of the system (1) may be ballasted to provide additional means for controlling buoyancy and thus the stability of the marine structure (2). Thus, the floating element (5) may include one or more ballast adjustment devices located in its underwater body (i.e., a part of the floating body that is submerged and in contact with water) to allow and / or control the flow of water between the inside of the floating element (5) and the water in which it floats. This allows its behavior to be adjusted, thus modifying the damping and natural frequency of the assembly during the phase of transfer to the marine structure (2). During maintenance operations, it limits the influence of the tides on the components of the floating system (1) and the marine structure (2). This ability is particularly advantageous in those operations in which the system (1) holds heavy equipment (for example, the blade of a wind turbine (20) to be replaced) in an eccentric manner, which would otherwise change its levelness. Due to the eccentric ballasting of the floating element (5), the system can counteract the destabilizing effects of the equipment during maintenance operations and even in the previous steps of transferring the system (1) to the offshore location of the marine structure (2). Likewise, the ballast device can be used as a tide offset device, thus allowing water to be introduced or emptied from the floating element (5). This ballast can be used to counteract the action of the tides while the system (1) is connected to the marine structure (2) during, for example, the maintenance of a fixed wind turbine (20).

[0084] The ballast regulating device preferably includes a gate and / or a pump having an opening, the gate being adjustable and / or actuated remotely; the pump being for removing or introducing water. Adjusting the opening of the gate allows establishing the filling level of the floating elements (5) of the system and / or the water inlet / outlet level, which in practice is equivalent to adjusting the effective water surface area and / or the draft. Thus, it is also possible to indirectly control the oscillation periods that the floating elements (5) and / or the assemblies formed by them together with the marine structure (2) will be in during different operating steps (for the transportation or maintenance of the marine structure (2)).

[0085] Subsequently, the floating elements (5) can be manufactured using materials known in the art, preferably concrete and / or metallic materials. Hybrid constructions can also be used, such that the lower part is made of concrete and the remaining part of the floating element (5) is made of steel. Prefabricated concrete techniques similar to those commonly used in prefabricated tank construction can also be used.

[0086] The configuration of the floating elements (5) can also be modular to adjust their overall dimensions. The parts or modules that can be used to form the floating elements (5) can adopt various shapes, and thus their dimensions are preferably such that they can be placed in a container (without exceeding the dimensions of a standard container) to facilitate their transportation and reuse. The modules can be attached to each other at the base and in height to form the floating elements (5).

[0087] Preferably, the assembly formed by the floating elements (5) and the coupling structure (7) (which is for coupling to the marine structure (2)) is hydrodynamically self-supporting, such that the mass distribution of the floating elements (5) and the coupling structure (7) and its corresponding center of buoyancy cause the floating elements (5) to be in balance in the upright position when the opening and / or closing subsystem (10) is open (i.e., where the system (1) is decoupled from the marine structure (2)).

[0088] In another preferred embodiment of the present invention, the method for maintenance can include an additional step, in which a reinforcement device (15) is applied to the elements of the marine structure (2), the coupling structure (7) is coupled to the marine structure (2) such that the marine structure (2) can withstand these forces, and the auxiliary floating system (1) can introduce these forces into the marine structure through the contact element (9').

[0089] Figure 8A single-pile offshore structure (2) is shown, and the reinforcement device (15) therein preferably includes the interior of the single pile filled completely or partially with concrete. This filling is preferably carried out in the contact area of the contact element (9'), and can be a complete, partial or annular filling of the interior of the single pile (at two horizontal heights that coincide with the two horizontal heights of the contact element (9') of the coupling structure (7)). For single piles equipped with a transition section between the single pile and the offshore structure (2), the said reinforcement device can be applied to the transition section in a similar manner. In other embodiments, therefore, other reinforcement devices known in the art (which can be metallic or of another type) can be used without departing from the scope of the present invention.

[0090] In another preferred embodiment of the present invention, the crane (12) is a mobile land crane, which is equipped with at least one boom, a counterweight and equipment for actuating the crane, and a lower body; the lower body includes means for moving the crane by wheels and / or caterpillars; and wherein the auxiliary floating system (1) only includes the said upper body of the crane (12) (the weight of which is thus reduced). Furthermore, it is assumed that during the method for maintenance, the crane (12) does not need to move, and the lower body can be dispensed with. In this embodiment, the auxiliary floating system (1) must include anchoring means for the connection of the said upper body of the crane (12). An example of the said embodiment is shown in Figure 4 wherein it can be seen that only the upper body of the crane is used, as compared to, for example Figures 5 to 7 where a land crane with two bodies (including a lower body with wheels) is used.

[0091] Finally, by way of illustration, Figures 9 to 10 shows different views of a preferred embodiment of the auxiliary floating system (1) of the present invention corresponding to Figures 5 to 7 wherein the floating element (5) is configured in the form of a barge.

Claims

1. A method for maintaining a wind turbine (20), the wind turbine (20) being supported on an offshore structure (2) and comprising a shaft (4) and / or a base (3), the offshore structure (2) being capable of floating or being fixed to the seabed; the The method is characterized in that it comprises using an auxiliary floating system (1), said auxiliary floating system (1) comprising: - one or more floating elements (5); - at least one crane (12), said at least one crane (12) being located on at least one of said floating elements (5); - at least one working area (13) for the storage and / or repair of components of the wind turbine (20) and / or the marine structure (2); - at least one coupling structure (7) for coupling to the marine structure (2); wherein said coupling structure (7) is connected to one or more floating elements by longitudinal connecting elements which extend from said one or more floating elements in a substantially horizontal direction perpendicular to the axis (4), and said coupling structure (7) comprises: - a hinged closing loop (8) adapted to close around an element of the marine structure (2), said hinged closing loop (8) being spaced apart from said one or more floating elements by said longitudinal connecting elements in said substantially horizontal direction perpendicular to the axis (4); - a plurality of contact elements (9') located between said coupling structure (7) and the marine structure (2); - a plurality of tensioning elements (9) allowing adjustment of the position of said contact elements (9'), said tensioning elements (9) being adapted to apply a tensioning force to the marine structure (2) in a substantially horizontal direction through said contact elements (9'); and wherein said coupling structure (7) is capable of assuming at least three configurations: - an open configuration, wherein said closing loop (8) is open; - a closed configuration, wherein said closing loop (8) is closed; - a tensioned configuration, wherein said closing loop (8) is closed and said tensioning elements (9) are arranged to apply a tensioning force to the marine structure (2); and the method is characterized in that it comprises performing the following steps in any technically possible order: a) transporting said auxiliary floating system (1) floatingly to the location of the marine structure (2); b) bringing said floating auxiliary floating system (1) close to the marine structure (2), wherein said coupling structure (7) is in said open configuration and is spaced apart from said one or more floating elements by said longitudinal connecting elements in said substantially horizontal direction perpendicular to the axis (4); c) arranging said coupling structure (7) in said closed configuration while said auxiliary floating system (1) remains floating and self-supporting until said closing loop (8) completely surrounds an element of the marine structure (2); d) acting on said tensioning elements (9) in a controlled manner to arrange said coupling structure (7) in said tensioned configuration while said auxiliary floating system (1) remains floating and self-supporting until the marine structure (2) and said auxiliary floating system (1) are rigidly connected with six degrees of freedom of movement, namely, sway, surge, heave, yaw, pitch and roll; e) using the crane (12) to perform maintenance tasks on the wind turbine (20) and / or on the offshore structure (2); f) using the working area (13) of the auxiliary floating system (1) to store and / or repair components of the wind turbine (20) and / or the offshore structure (2); g) uncoupling the auxiliary floating system (1) from the offshore structure (2) so as to arrange the coupling structure (7) in the open configuration; wherein the method further comprises a step prior to step c): k) applying a strengthening device (15) to an element of the offshore structure (2) to which the coupling structure (7) is coupled, such that the offshore structure (2) is capable of withstanding the forces which the auxiliary floating system (1) can introduce into the offshore structure (2) via the contact element (9').

2. The method according to the preceding claim, wherein the auxiliary floating system (1) comprises a plurality of floating elements (5) which are connected to one another and / or to the coupling structure (7).

3. The method according to claim 1, wherein the auxiliary floating system (1) comprises a single floating element (5) in the form of a barge, and both the crane (12) and the working area (13) are arranged in the single floating element (5), and wherein the barge is formed by a single body or by the attachment of several modules connected to one another.

4. The method according to any one of the preceding claims, wherein the crane (12) is a folding crane, and wherein the crane (12) is deployed and folded after step d) and folded again before step g).

5. The method according to claim 1, wherein the working area (13) is at least partly located at a distance from the crane (12) which is greater than the minimum operating radius of the crane (12).

6. The method according to claim 1, wherein the working area (13) is at least partly free with respect to the floating element (5), such that at least a part of the area of the working area (13) is not located on the deck of the floating element (5).

7. The method according to claim 1, wherein step a) and / or b) is performed by towing the auxiliary floating system (1) or by self-propelled conveyance of the system (1).

8. The method according to claim 1, wherein the floating element (5) comprises a hydrodynamic damping plate.

9. The method according to claim 1, wherein the floating element (5) can be ballasted in a central or eccentric manner.

10. The method according to claim 1, comprising a step after step d): j) ballasting at least one floating element (5) to counteract the rise of the tide and / or de-ballasting at least one floating element (5) to counteract the fall of the tide.

11. The method according to claim 1, wherein the freeboard of the auxiliary floating system (1) is compatible with the tidal range such that when the auxiliary floating system (1) remains coupled to a fixed marine structure, the change in the tide never causes the freeboard to decrease to less than 10 cm.

12. The method according to claim 1, wherein the auxiliary floating system (1) is equipped with one or more cables between the system (1) and the marine structure (2) for bringing the system (1) close to or fixing it to the marine structure (2), and wherein the length of the cable is adjusted during the approaching step b).

13. The method according to claim 1, wherein the closed loop (8) maintains an internal space sufficient for the connection of the closed loop (8) to an area of the marine structure (2), the marine structure (2) including a ship landing structure.

14. The method according to claim 1, wherein the tensioning element (9) includes a lever (10) and an extendable and / or foldable hydraulic cylinder (11), the lever (10) being fixed at a hinge point (14), the lever (10) being rotatable relative to the hinge point (14), and the extendable and / or foldable hydraulic cylinder (11) being connected to a point on the lever (10); The contact element (9') is connected to another point on the lever (10); and wherein by actuating the hydraulic cylinder (11) to extend and / or fold it, the lever (10) is caused to rotate, and thus the position and / or the force applied by the contact element (9') is adjusted.

15. The method according to claim 14, wherein the distance between the line of action of the hydraulic cylinder (11) and the hinge point (14) is greater than the distance between the line of action of the contact element (9') and the hinge point (14), such that by a lever effect, the force F in the hydraulic cylinder (11) generates a force F' in the contact element (9'), the force F' being greater than F.

16. The method according to claim 1, wherein the marine structure (2) is a monopile structure, and the reinforcement device (15) includes the interior of the monopile filled completely or partially with concrete.

17. The method according to claim 1, wherein the auxiliary floating system (1) includes: - means for controlling and / or monitoring the tensioning force and / or position of the tensioning element (9); and / or - means for opening and closing the closed loop (8).

18. The method according to claim 1, wherein the contact element (9') includes a support plate that contacts the marine structure and has a coefficient of friction greater than 3%, such that when the contact element (9') is tensioned against the marine structure (2), a frictional force that contributes to a firm connection between the marine structure (2) and the auxiliary floating system (1) is generated.

19. The method according to claim 1, wherein the closed loop (8) comprises a protective device, the position of the protective device being such that during step b) and / or c), the protective device contacts the marine structure before the contact element (9').

20. The method according to claim 1, wherein the crane (12) is a mobile land crane with crawlers or wheels, the mobile land crane being supported on at least one floating element (5).

21. The method according to claim 1, wherein the crane (12) is a mobile land crane, the mobile land crane comprising: - an upper body, the upper body comprising at least one boom, a counterweight, and equipment for actuating the crane; - a lower body, the lower body comprising means for moving the crane by wheels and / or crawlers; and wherein the auxiliary floating system (1) only comprises the upper body of the crane.

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