Mooring line anchored monopile for offshore wind turbine foundation

Abstract

Techniques are disclosed herein for minimizing movement of a fixed marine structure. Using the technologies described, a wind turbine may be mounted on a fixed marine platform that is secured by mooring lines coupled to one or more driven anchor piles. Each of the anchor piles may be driven into the seabed floor at an angle of batter that is less than or equal to an angle of inclination of a corresponding morning line.

Description

MOORING LINE ANCHORED MONOPILE FOR OFFSHORE WIND TURBINE FOUNDATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Number 63 / 581,097 entitled “Mooring Line Anchored Monopile as Offshore Wind Turbine Foundation,” filed September 7, 2023, which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Offshore wind power is of great importance and potential in transition energy production from traditional fossil fuels to more environmentally friendly solutions. In deep-water regions (e.g., depths of approximately 200 meters or more), floating marine structures, commonly referred to as “platforms,” are typically used for exploration activities and the mounting of wind turbines. In shallower regions (e.g., depths of approximately 50 meters or less), fixed structures that are mounted to the sea floor are commonly used to mount wind turbines and provide platforms for various activities. For platforms installed in either depth or depths in between, determining how to reduce movement of such platforms to support wind turbines, can be challenging. In an open ocean, winds, waves, and currents often act simultaneously and exert forces on the marine platforms causing the platforms to move.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIG. 1 illustrates an example wind turbine system supported by an FRP- monopile structure, in accordance with examples of the disclosure.

[0004] FIG. 2 illustrates an example FRP -monopile for supporting a wind turbine, in accordance with examples of the disclosure.

[0005] FIG. 3 illustrates an example floating ocean platform for supporting a wind turbine, in accordance with examples of the disclosure.

[0006] FIG. 4 illustrates an example fixed marine structure 400 having inclined anchor piles configurations from a bird’s eye view, in accordance with examples of the disclosure.

[0007] FIG. 5 illustrates an example FRP, mooring lines, and a mooring line tensioning system, in accordance with examples of the disclosure.

[0008] FIG. 6 illustrates an example driven anchor pile and mooring line assembly, in accordance with examples of the disclosure.

[0009] FIG. 7 illustrates another example driven anchor pile and mooring line assembly, in accordance with examples of the disclosure.

[0010] FIG. 8 illustrates yet another example driven anchor pile and mooring line assembly, in accordance with examples of the disclosure.

[0011] FIG. 9 illustrates an example multi driven anchor pile and mooring line assembly, in accordance with examples of the disclosure.

[0012] FIG. 10 illustrates an example installation of a driven anchor pile at an incline, in accordance with examples of the disclosure.

[0013] FIG. 11 illustrates fixed marine structure and mooring line configuration, in accordance with examples of the disclosure.

[0014] FIG. 12 further illustrates in diagram a relationship between the natural frequencies of exemplary FRP -monopiles implemented as described herein and wave frequencies.DETAILED DESCRIPTION

[0015] The following detailed description is directed to technologies for minimizing movement of a marine structure, such as an offshore wind turbine. Using the technologies described herein, a wind turbine may be mounted on a fixed marine platform that is constructed and mounted on the seabed in water of up to approximately 100 meters. In various examples, a wind turbine may be mounted on a fully restrained platform (FRP) monopile. A monopile is a pile structure that is driven into the seafloor and that may form a portion of or otherwise support a fixed marine platform, such as an FRP. As used herein, the terms FRP refers to a platform that has motions restrained in 6 degrees-of-freedom (DOFs) and FRP -monopile refers to an FRP that includes a monopile.

[0016] For purposes of explanation, the main structural component of a platform can be viewed as a rigid body. Its motions may be characterized by and measured in 6 degrees-of-freedom (DOFs) including 3 translational DOFs (surge, sway, and heave) and 3 rotational DOFs (roll, pitch, and yaw). Environmental loads may apply force to the platform in one or more DOFs. Some of these loads are dynamic in nature, such as loads due to water waves, while others may be largely static, such as loads due to ocean current induced drag.

[0017] An example platform design philosophy is that in shallow waters, the environmental loads are mainly resisted by the lateral stiffness of the platform, which is designed to be “fixed.” One such example is the jacket platform which is a lattice structure with its legs extending into the earth. In deeper waters, such as greater than 50 meters however, the amount of material required for a fixed platform may be uneconomical and, therefore, floating platforms may be used. As discussed herein, an FRP -monopile concepts may be configured with a variety of technologies to resist and / or allow motion operating at some or all of the 6 DOFs’ at depths between 50 meters and 120 meters, thereby extending the range of FRP platforms into deeper waters.

[0018] For a wind turbine to function effectively, it is desirable that its host structure has as little movement as possible. A wind turbine supported by a platform that attempts to minimize motions in all of its 6 DOFs may more effectively generate power than turbines mounted on platforms that do not restrain motion in all 6 DOFs. Prior to the techniques described herein, no known fixed platforms that possess such features have been effectively implemented in intermediate-depth waters (e.g., 50 meters to 100 meters) to host wind turbines. As described herein, a fixed marine structure with mooring lines and anchors are disclosed that reduces and / or minimizes motions in shallow and intermediate-depth water (e.g., depths of up to 100 meters or more). The disclosed structures may host one or more wind turbines and associated structures and equipment.

[0019] An offshore wind turbine mounted on an FRP -monopile generally includes six main components: (1) a single pile (“monopile”) driven into the seafloor, (2) a wind tower to which a wind turbine is mounted, (3) a transition piece mounted to the monopile and to which the wind tower is mounted, (4) one or more anchors affixed to the seafloor, (5) one or more mooring lines affixed to the anchors and to the transition piece, and (6) the wind turbine, which may include a nacelle (e.g., housing), a rotor hub, blades, and various other components. In addition to a wind turbine, other structures and equipment can also be mounted on a platform such as the disclosed FRP- monopile. As described in more detail below, the mooring lines may be connected at one end to one or more connection components configured at the transition piece that may facilitate the application and adjustment of tension on the mooring lines and to one or more anchors secured to the seabed floor at the other end. In some cases, a buoyant structure (such as an air can or the like) may be incorporated into the upper end of themonopile to assist with restraining movement of the platform and turbine in deeper waters.

[0020] Using the techniques described herein, the motions in all of the 6 DOFs of an offshore wind turbine mounted on a fixed marine structure may be reduced and / or restrained. The motions referred to herein are those caused by various types of environmental loading. The external forces causing the motions include those from waves and ocean currents on the structure, from the moorings along with any part of the turbine and / or structure in contact with water, and from winds on any part of the structure above the sea surface.

[0021] In various examples, unlike conventional FRP systems that focus on the overall foundation system and top mooring assembly and physical coupling to the platform, the FRP -monopile, discussed herein, relates to methods and apparatus to transfer the global loads on the FRP foundation to the seabed soil. The FRP -monpile, discussed herein, may utilize pretensioned mooring lines and angularly installed mooring anchor piles to transfer the global loads to the seabed. For instance, during turbine operations, the mooring lines experience dynamic (e.g., changing) loads due to imbalance of the rotor and / or the blades passing the wind tower, in addition to the ambient environmental loads. For example, during a storm, the environmental loads (those from winds, waves, currents, and the like) on the platform are high and dominant, and the turbine is shut down.

[0022] In consideration of transferring a large, dynamic load from a mooring line to the seabed soil, a driven anchor pile, which possesses high load resistance capacity, may be used. In some cases, for the mooring lines of the FRP -monopile to provide lateral resistance, the mooring lines of the FRP -monopile are inclined from vertical by an angle (such as up to 45 degrees). The mooring loads at the seabed anchor positions are, therefore, primarily about or approximately the same angle (e.g., up to 45 degrees from vertical). These mooring lines mainly transfer axial loads even when the mooring line experiences lateral loads (such as caused by waves). In the FRP-monopile, discussed herein, the angular mooring lines may be coupled to an inclined (or batter) driven anchor pile to provide support for and transfer of the axial loads to the seabed floor. For example, the stiffness of a driven anchor pile derives from both the surrounding soil of the seabed and the anchor pile structure itself.

[0023] However, in the current implementation, the overall axial stiffness of a driven anchor pile dominates in the lateral direction due to the large difference in axialstiffness and lateral stiffness of the pile anchor structure itself. For example, the axial stiffness and lateral stiffness of a beam structure fixed at one end may be represented as EA / L and 3E / L3, respectively, where E is Young’s modulus, A is the cross section area, L is the length, and / is the area moment of inertia. Accordingly, for a circularshaped tubular anchor pile with dimensions for an engineering application (e.g., length L = 20 meters and a diameter = 2 meters), the axial stiffness may be 280 times that of the lateral direction. In this manner, by utilizing a driven anchor pile having an incline or angle substantially similar to (e.g., within a range or threshold of degrees) the incline or angle of the mooring lines, a smaller anchor pile (in terms of pile diameter and the embedded length) may be used when compared to conventional vertical driven piles. A reduction in the size of the anchor pile translates to reduced costs and installation time as the anchor pile is smaller than conventional anchor pile designs (e.g., reduced materials, manufacturing costs, and installation costs).

[0024] In the following detailed description, references are made to the accompanying drawings that form a part hereof, and that show, by way of illustration, specific or generalized examples. The drawings herein are not drawn to scale. Like numerals represent like elements throughout the several figures (which may be referred to herein as a “FIG.” or “FIGs.”).

[0025] FIG. 1 illustrates an example wind turbine system 100 supported by an FRP- monopile structure. The wind turbine system 100 may include a wind turbine 110 that may include a housing, a rotor hub, blades, and various other components associated with generating and / or collecting energy based on the rotation of one or more blades caused by wind forces. The wind turbine 110 may be mounted on, affixed to, or otherwise supported by a wind tower 120.

[0026] The wind tower 120 may be mounted on, affixed to, or otherwise supported by a transition piece 130 that may in turn be mounted on, affixed to, or otherwise supported by a monopile 140. In some cases, the transition piece 130, and the monopile 140 may form an FRP -monopile 190 that supports the wind tower 120 and / or the wind turbine 110 (or other types of turbines). Each of the wind tower 120, the transition piece 130, and the monopile 140 may be constructed of one or more materials of any type and may include one to more portions and / or components configured for various purposes. For example, the materials used to construct each of the wind tower 120, the transition piece 130, and the monopile 140 may be substantially rigid and / or treated to withstand oceanic environmental conditions (e.g., long-term exposure to salt water,high winds, etc.). In a particular example, one or more buoyant structures may be configured at or otherwise affixed to a submerged portion of one or more of the monopile 140 to compensate for forces that may be applied to such components, such as mooring loads.

[0027] The monopile 140 may be a single pile driven into the seafloor 180 and may be substantially (e.g., entirely) submerged. The monopile 140 may affix to the transition piece 130 underwater. The transition piece 130 may include portions below water and above the waterline 170, supporting the wind tower 120 substantially (e.g., entirely) above the waterline 170.

[0028] One or more stability-enhancing components, such as moorings, may be affixed to the FRP -monopile 190. In examples, such components may be affixed to the transition piece 130. For instance, one or more mooring lines 150 may be affixed or otherwise connected to the transition piece 130. The mooring lines 150 may be affixed or otherwise attached to one or more driven anchor piles 160 that may be driven into or otherwise attached to the seafloor 180. As described in more detail below, the individual mooring lines 150 may be connected to one or more connection components configured at the transition piece 130 that may facilitate the application and adjustment of tension on the mooring lines. The mooring lines 150 may resist the environmental forces that may be applied to the FRP-monopile 190.

[0029] As discussed herein, the one or more anchor piles may be driven into the seabed floor 180 at an incline that is within a range or substantially similar to the incline of the corresponding mooring line 150, as illustrated. It should be understood that the angle of each mooring line 150 may vary during use (such as in response to waves, current, winds, and the like) and that the alignment between the incline or angle of the anchor pile 160 and the corresponding mooring line 150 may vary within a predefined range during use.

[0030] The FRP-monopile 190 may form a beam column “clamped” at a first end (e.g., driven into the seabed floor 180) and carrying a payload (e.g., the wind turbine 110) at the opposite end. The moorings lines 150 attached to the FRP-monopile 190 may form intermediate supports for this beam column. As an axially loaded structure configured in an oceanic environment, the FRP-monopile 190 may be subject to various steady and dynamic loads (e.g., from typical weather and less common weather events, such as storms). Such loads may be primarily lateral, for example resulting from winds waves, and currents.

[0031] FIG. 2 illustrates an example FRP-monopile 200 for supporting a wind turbine, in accordance with examples of the disclosure. In the current example, inclined mooring lines 210 are attached to the monopile 200 (such as at the monopile-transition piece structure 130 of FIG. 1) at an angle 220, in order to provide a desired lateral resistance. The angle of the top end of the line from the vertical direction is defined herein as the departure angle 220. If the mooring line itself is not neutrally buoyant, the self-weight of the line causes the mooring line itself to sag. For example, if the departure angle 220 is 45 degrees, the actual departure angle 220 may be slightly smaller, such as 43.4 degrees. In dynamics, the departure angle 220 may change over time (such as caused by stretching of the mooring line). In some implementations, the departure angle 220 may be configured to be within a range of 30 to 60 degrees from vertical. In other implementations, the departure angle 220 may be configured to be within a range of 40 to 50 degrees from vertical. In still other some implementations, the departure angle 220 may be configured to be within a range of 20 to 70 degrees from vertical. Accordingly, to provide lateral resistance to the FRP-monopile 200, the mooring lines 210 may be designed to have a range of departure angles 220 to accommodate design limits such as footprint constraints, unfavorable soil conditions, and the like.

[0032] In some examples, the anchor piles 230 are oriented or inclined in a manner to have an incline (or angle of batter 240) substantially corresponding to the departure angle 220. It is also noted that even if not perfectly aligned (e.g., the departure angle 220 is not perfectly matched with the angle of batter 240), there are benefits in making use of the axial holding capacity of the inclined driven pile. As used herein, the angle between the axial axis of each driven anchor pile 230 and the vertical direction 250 is defined as angle of batter 240. The angle of batter 240 may be in a range of values for various FRP-monopile designs, such as a driven anchor pile with an angle of batter larger than 45 degrees. One advantage of an angle of batter larger than 45 degrees is the higher horizontal projection of the mooring tension and line axial stiffness, which is beneficial to the lateral resistance of the overall FRP-monopile foundation, potentially resulting in a lower grade of line required and reduced costs.

[0033] In the current examples, the mooring lines 210 are coupled to the FRP- monopile 200 above a waterline 260, however, it should be understood that in some implementations, the mooring lines 210 may be coupled at or below the waterline 260.

[0034] FIG. 3 illustrates an example floating ocean platform 300 for supporting a wind turbine, in accordance with examples of the disclosure. In some cases, the waterdepth and / or the soil composition may not be suitable for a monopile structure. In these cases, a floating ocean platform 300 may be secured using the inclined anchor piles 310 and corresponding mooring lines 320 as discussed herein. In the current example, inclined mooring lines 320 are attached to the platform 300 again at a known departure angle 330 from vertical 340. Likewise, the anchor piles 310 are oriented or inclined in a manner to have an angle of batter 340 substantially corresponding to the departure angle 330. As discussed above, even if not perfectly aligned (e.g., the departure angle 330 is not perfectly matched with the angle of batter 340), there are benefits in making use of the axial holding capacity of the inclined driven pile 310.

[0035] FIG. 4 illustrates an example fixed marine structure 400 having inclined anchor piles 420 configurations from a bird’s eye view, in accordance with examples of the disclosure. As illustrated, an FRP -monopile structure 410 may be secured to three or more inclined anchor piles 420 by three groups of mooring lines (not shown). Each of the groups of mooring lines may have any number of mooring lines. Each mooring line in the groups of mooring lines may be connected to a single anchor pile 420 or a group of multiple anchor piles, or the like, and may connect to the FRP- monopile structure 410 with a top mooring assembly (TMA) that has a proximate vertical orientation, with respect to the FRP -monopile structure 410, to the other TMAs connecting other mooring lines 420, that are located substantially evenly about the perimeter of the FRP -monopile structure 410 (e.g., at separation angles of substantially 120 degrees in the illustrated example).

[0036] It should be understood that any other configuration and distribution of mooring lines and mooring line groups that may be used are contemplated as within the scope of the instant disclosure. For example, a group of four or five sets of mooring lines may be utilized. Moreover, any of the tensioning systems, TMAs, mooring lines, and associated components and techniques described may be used interchangeably. For example, any of the hydraulic and pulley tensioning techniques may be used with any stopper position securing techniques described herein, and the like. All combinations of any of the various systems, components, techniques, and subsets thereof are contemplated as within the scope of the instant disclosure.

[0037] FIG. 5 illustrates a mooring line system 500 for mitigating motion at an FRP -monopile according to various examples. An FRP -monopile 510 may be driven into or otherwise attached to a seafloor 560 as discussed herein. At least a portion of the FRP -monopile 510 may be below the waterline 520, while another portion may beabove the waterline. A mooring line 530 having a departure angle 540 as shown. Note that in this example, a single mooring line 530 is illustrated for exemplary purposes, but multiple mooring lines and their associated components may typically be installed at an FRP -monopile 510. The mooring line 530 may be physically coupled to a top surface of an anchor pile 550. As discuses herein, the anchor pile 550 may be driven into or otherwise attached to the seabed floor 560 at an incline between 1 degree and 45 degrees. In some cases, the anchor 550 may be a pile driving at an angle of batter 570 that is within a range of degrees from the departure angle 540, as discussed herein.

[0038] In the current example, the mooring line 530 may be coupled to the monopile 510 via a top mooring assembly (TMA) 580. In various examples, the TMA 580 may be mounted to the FRP -monopile 510 substantially above the waterline 520. The TMA 580 may include a mooring porch 582 affixed to the FRP-monopile 510 and that may directly bear the load applied by the mooring line 530 tension. The porch 582 may be welded or otherwise permanently and non-detachably affixed to the FRP- monopile 510. The TMA 580 may further include a stopper 584 to which the mooring line 530 may be connected. The mooring line 530 may connect to the stopper 584 above the porch 582 and pass through an opening in the porch 582, exiting below the porch 582. This opening may prevent the stopper 584 from passing through the porch 582 (e.g., may be smaller than the dimensions of the stopper 584). By connecting the mooring line 530 to the stopper 584, the stopper 584 may be configured to prevent the mooring line 530 from moving below the porch 582. By applying a linear upwards force to the stopper 584 (e.g., “pulling” the stopper 584up), the tension in the mooring line 530 may be increased. Detailed examples of techniques and systems to perform this increase of tension are described herein.

[0039] FIG. 6 illustrates an example driven anchor pile and mooring line assembly 600, in accordance with examples of the disclosure. In the current example, the assembly 600 may include the driven anchor pile 610 having a coupling mechanism 620 along a top surface of the pile 610. The coupling mechanism 620 may be utilized to secure a morning line 630 to the anchor pile 610.

[0040] In the current example, the angle of batter 640 between a vertical position 650 and the anchor pile 610 may be substantially equal or aligned with the departure angle of the morning line 630. In this manner, the mooring line 630 and the anchor pile 610 may be approximately aligned along a plane or trajectory defined by the trajectory of the mooring line 630. In various implementations, the angle of batter 640 may bewithin a threshold number of degrees of the departure angle. For instance, in various examples, the angle of batter 640 may be less than or equal to 1 degree of difference than the departure angle, less than or equal to 2 degrees of difference than the departure angle, less than or equal to 5 degrees of difference than the departure angle, less than or equal to 10 degrees of difference than the departure angle, less than or equal to 15 degrees of difference than the departure angle or the like.

[0041] FIG. 7 illustrates another example driven anchor pile and mooring line assembly 700, in accordance with examples of the disclosure. In the current example, the assembly 700 may include the driven anchor pile 710 having a coupling mechanism 720 along a top surface of the pile 710. The coupling mechanism 720 may be utilized to secure a morning line 730 to the anchor pile 710.

[0042] In the current example, the angle of batter 740 between a vertical position 750 and the anchor pile 710 may be less than or equal to the departure angle of the morning line 730 and / or the angle of line inclination 750. For instance, installation of a vertical pile may be easier, such as less costly or less resource intensive (time and energy). In other cases, the soil material may affect the angle of batter 740 and / or the ability or ease at which an anchor pile 710 may be driven into the seabed floor. In these cases, the angle of batter may be less than or equal to the angle of line inclination 750 and / or the departure angle of the mooring line 730. In some examples, the angle of batter may be less than or equal to 45 degrees, 40 degrees, 30 degrees, 20 degrees, or the like.

[0043] FIG. 8 illustrates yet another example driven anchor pile and mooring line assembly 800, in accordance with examples of the disclosure. In the current example, the assembly 800 may include the driven anchor pile 810 having a coupling mechanism 820 along a top surface of the pile 810. The coupling mechanism 820 may be utilized to secure two or more morning lines 830 and 840 to the anchor pile 810, as shown.

[0044] For instance, if there is only one mooring line 830, the axial axis of the anchor pile 810 may be aligned with a threshold number of degrees with the angle of departure or the angle of line inclination associated with the mooring line 830 as illustrated above with respect to FIG. 6. However, when there are two or more mooring lines, such as mooring lines 830 and 840 in the current example, in a group for attaching to a single anchor pile 810, the axial axis of the anchor pile 810 cannot align with the with the angle of departure or the angle of line inclination associated with both of the mooring lines 830 and 840. In this example, the axial axis of the anchor pile 810 maybe aligned with a center line 850 of the group of moorings 830 and 840, as shown. In the current example, two mooring lines 830 and 840 are illustrated, however, it should be understood that any number of mooring lines may be coupled to a single anchor pile 810.

[0045] FIG. 9 illustrates an example multi driven anchor pile and mooring line assembly 900, in accordance with examples of the disclosure. In the current example, the assembly 900 may include two or more driven anchor piles, such as anchor piles 910, 920, and 930 in the illustrated example. The anchor piles 910-930 may be physically coupled (such as welded to) a horizontal plate 940. The horizontal plate 940 may include a coupling mechanism 950 along a top surface of the plate 940 for securing the morning line 980 to the anchor piles 910, 920, and 930.

[0046] In the current example, the angle of batter 960 for each of the anchor piles 910-930 may be approximately equal with each other. The angle of batter 960 may also be approximately equal to the departure angle and / or the angle of line inclination 970 associated with the mooring line 980, as shown. As discussed above, the angle of batter 960 for each of the anchor piles 910-930 may be within a threshold number of degrees of the departure angle and / or the angle of line inclination 970. For instance, in various examples, the angle of batter 960 may be less than or equal to 1 degree of difference than the departure angle and / or the angle of line inclination 970, less than or equal to 2 degrees of difference than the departure angle and / or the angle of line inclination 970, less than or equal to 5 degrees of difference than the departure angle and / or the angle of line inclination 970, less than or equal to 10 degrees of difference than the departure angle and / or the angle of line inclination 970, less than or equal to 15 degrees of difference than the departure angle and / or the angle of line inclination 970, or the like.

[0047] In other examples, the angle of batter 960 of the anchor piles 910-930 may be less than or equal to the departure angle and / or the angle of line inclination 970 of the morning line 980.

[0048] FIG. 10 illustrates an example installation 1000 of a driven anchor pile 1010 at an incline, in accordance with examples of the disclosure. For example, in order for the mooring lines to provide lateral resistance to the monopile in 360 degrees around the piles 1010 circumference, there must be several piles (such as a group of three, a group of four, a group of five, and or the like) evenly spaced around the monopile. Therefore, there are several inclined driven piles 1010 to be installed. The inclined anchor pile 1010 can be installed with the aid of a driven pile support 1020. The drivenpile support 1020 may include a grip 1022 at a lower end. The pile support 1020 is configured to support the self-weight of the pile 1010 and guide the pile 1010 along the angle of batter during hammering. In this example, an underwater hammer 1030 is applied in the direction of the angle of batter to drive the anchor pile 1010 into its final position in the seabed floor 1040.

[0049] In various examples, the installation 1000 may include transporting an installation vessel to a desired location along the surfaces of a body of water, such as a sea. The installation vessel may lower the anchor pile 1010 to the seabed floor 1040. The underwater hammer 1030 may be mounted on the seabed floor 1040 and aligned with the pile support 1020. The anchor pile 1010 may be placed on the pile support 1020 such that a lower end of the pile 1010 is positioned within the pile grip 1022. The underwater hammer 1030 may then drive the pile 1010 into the seabed floor 1040 via a hammering, pounding, or other pressure driven technique. Once the pile 1010 is driven to a desired depth within the seabed floor 1040, the hammer 1030 and pile support 1020 may be dismounted and returned or raised to the surface or moved to a desired location of a second pile.

[0050] FIG. 11 illustrates fixed marine structures and mooring line configurations 1110, 1120, and 1130, in accordance with examples of the disclosure. Mooring lines, or groups of mooring lines, may be symmetrically distributed about the perimeter of a fixed marine structure. In configuration 1110, a fixed marine structure 1112 may be secured by three groups 1111 of mooring lines. Each of the groups 1111 of mooring lines may have any number of mooring lines. Each mooring line in mooring line groups 1111 may be connected to a single incline driven anchor pile (or group of incline driven anchor pile) and may connect to the structure 1112 at a position that is proximate to other connection points for other mooring lines that are located substantially evenly about the perimeter of the structure 1112 (e.g., at separation angles of substantially 120 degrees).

[0051] In configuration 1120, a fixed marine structure 1122 may be secured by four groups 1121 of mooring lines. Here again, each of the groups 1121 of mooring lines may have any number of mooring lines, each mooring line in a group may be connected to a single incline driven anchor pile (or group of incline driven anchor piles), and each mooring line in a group may connect to the structure 1122 with at a connection point that is proximate to other connection points coupling other mooring lines in the same group. As shown here, the four mooring line groups 1121 may be distributedsubstantially evenly about the perimeter of the structure 1122 (e.g., at separation angles of substantially 90 degrees).

[0052] In another example configuration 1130, a fixed marine structure 1132 may be secured by five groups 1131 of mooring lines. Here again, each of the groups 1131 of mooring lines may have any number of mooring lines, each mooring line in a group may be connected to a single incline driven anchor pile (or group of incline driven anchor piles), and each mooring line in a group may connect to the structure 1132 with a connection point that is proximate to other connection points coupling other mooring lines in the same group. As shown here, the five mooring line groups 1131 may be distributed substantially evenly about the perimeter of the structure 1132 (e.g., at separation angles of substantially 72 degrees).

[0053] Any other configuration and distribution of mooring lines and mooring line groups that may be used are contemplated as within the scope of the instant disclosure. Moreover, any of the tensioning systems, mooring lines, and associated components and techniques described may be used interchangeably. For example, any of the hydraulic and pulley tensioning techniques may be used with any stopper position securing techniques described herein, etc. All combinations of any of the various systems, components, techniques, and subsets thereof are contemplated as within the scope of the instant disclosure.

[0054] FIG. 12 further illustrates in diagram 1200 a relationship between the natural frequencies of exemplary FRP-monopiles implemented as described herein and wave frequencies. As illustrated in the diagram 1200, the systems and techniques described herein, including the use of high tension mooring lines and associated aspects described herein, may be used to implement an FRP-monopile structure 1210 with a wave frequency zone substantially below the natural frequencies corresponding to the 6 DOFs. As shown in this diagram, all of the 6 natural frequencies for surge, sway, heave, roll, pitch, and yaw are on the right side of the significant wave frequency (the peak in the diagram) where the wave energy is the largest. Thus, an FRP-monopile structure 1210 implemented according to the instant disclosure may experience minimal movement in both normal operating conditions and extreme (e.g., storm) conditions.

[0055] While the examples described herein may refer to FRP-monopiles 1210 used as supporting structures for wind turbines, the disclosed FRP-monopiles 1210 may be used to provide marine support for other objects, systems, and components, such as energy storage units, offshore substations, etc. Because the disclosed FRP-monopilesare not payload sensitive, FRP-monopiles 1210 as described herein may be scaled up and / or down as needed to support objects having a wide range of mass.

[0056] As described throughout the instant disclosure, mooring lines may be used to provide further stability to an FRP -monopile 1210. Mooring lines may be configured to maintain tension, in some examples, within a tension range. Over time, such mooring lines may loosen due to dynamic forces (e.g., wind, waves, currents, etc.). This loosening may result in mooring line tension falling outside of a design tension range, therefore reducing the ability of the loosened mooring lines to mitigate motion in the 6 DOFs. While re-tensioning systems and techniques have been successfully implemented for land-based applications and for floating marine platforms, these systems and techniques have not been successfully implemented for mooring lines used to stabilize fixed marine structures.

[0057] For example, the various systems and techniques available for re-tensioning in floating structures typically involve large increases or decreases in tension, preventing the fine tension adjustment often needed for FRP-monopile mooring lines. The various systems and techniques available for re-tensioning in land-based structures typically use less robust stabilizing components due to land-based structures being subject to lower axial loads (e.g., lower levels of motion in the 6 DOFs). FRP-monopile structures 1210 require stabilizing systems and techniques that address the higher axial loads to which such structures are subject while providing finer tension adjustment. The FRP-monopile structure stabilizing systems and techniques described herein address these issues while providing safer, easier, and more cost-effective means of applying and adjusting tension in the environments in which such structures are typically located.

[0058] For example, in a FRP monopile design, all its motions (namely surge, sway, heave, roll, pitch, and yaw) are restrained by the monopile and the moorings. In general, an FRP monopile is a stiffness-controlled structure with its lateral stiffness, e.g., produced by a combination of the monopile and the moorings, can be on the order of 30,000 kN / m. The vertical stiffness is on the order of 5,000,000 kN / m. For supporting a turbine with a payload under 3,000 MT (a downward force of 29,420 kN), the vertical stiffness is significantly high. As a result, all of its six natural frequencies (corresponding to the 6 DOF motions) are above the significant wave frequency zone. Consequently, this structure has less movement in normal operations and even storm conditions.

[0059] Based on the foregoing, it should be appreciated that technologies for minimizing movement of a fixed marine structure that may support a wind turbine have been presented herein. The subject matter described above is provided by way of illustration only and should not be construed as limiting. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. Various modifications and changes may be made to the subject matter described herein without following the examples and applications illustrated and described, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.

[0060] Although the discussion above sets forth example implementations of the described techniques, other architectures may be used to implement the described functionality and are intended to be within the scope of this disclosure. Furthermore, although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claims.EXAMPLE CLAUSES

[0061] A. A system, comprising: a fixed marine platform to host a wind turbine; at least one mooring line coupled to the fixed marine platform, the at least sone mooring line having a departure angle; and at least one anchor pile driven into a seabed floor at an angle of batter that is equal to or less than a threshold number of degrees from the departure angle, each of the at least one anchor piles having a coupling mechanism to secure a corresponding one of the at least one mooring lines.

[0062] B. The system of A, wherein the seabed floor is between a depth of about fifty meters and one hundred and twenty meters under a surface of water.

[0063] C. The system of A, wherein: an individual one of the at least one mooring lines comprises a group of two or more mooring lines; and the departure angle is an angle of a center line associated with the two or more mooring lines of the group of two or more mooring lines.

[0064] D. The system of A, wherein: each anchor pile comprises a first anchor pile driven into the seabed floor at the angle of batter and a second anchor pile driven intothe seabed floor at the angle of batter; and the first anchor pile is physically coupled to the second anchor pile.

[0065] E. The system of A, wherein the threshold number of degrees is one or more of the following threshold number of degrees: five degrees; ten degrees; fifteen degrees; or thirty degrees.

[0066] F. The system of A, wherein the angle of batter is greater than the angle of departure angle and less than a threshold angle of batter.

[0067] G. The system of A, wherein the angle of batter is less than or equal to the departure angle.

[0068] H. A structure for hosting a wind turbine, comprising: a mooring line physically coupled to the monopile structure; and an anchor pile having a coupling mechanism to secure the mooring line to the anchor pile, the anchor pile driven into a seabed floor at an angle of batter that is less than a threshold angle of batter.

[0069] I. The monopile structure of H, wherein the threshold angle of batter is an angle of line inclination associated with the mooring line.

[0070] J. The monopile structure of H, wherein the structure for hosing the wind turbine is fully restrained marine platform embedded in a seabed floor.

[0071] K. The monopile structure of H, wherein the mooring line is physically coupled to the monopile structure above a water line.

[0072] L. The monopile structure of H, wherein the mooring line is physically coupled to the monopile structure below a water line.

[0073] M. The monopile structure of H, wherein the angle of batter is equal to or less than a threshold number of degrees from the angle of line inclination.

[0074] N. The monopile structure of H, wherein the anchor pile comprises a first anchor pile driven into the seabed floor at the angle of batter and a second anchor pile driven into the seabed floor at the angle of batter.

[0075] O. The monopile structure of N, wherein the first anchor pile is physically coupled to the second anchor pile by a horizontal plate and the coupling mechanism is physically coupled to the horizontal plate.

[0076] P. The monopile structure of H, wherein: the mooring line comprises two or more mooring lines; and the angle of line inclination is an angle associated with a center line between the two or more mooring lines.

[0077] Q. The monopile structure of H, wherein the mooring line comprises a first mooring line and a second mooring line, the first mooring line coupled to the structureat a first evaluation from the seabed floor and the second mooring line coupled to the structure at a second evaluation form the seabed floor, the second elevation different than the first elevation.

[0078] R. A method comprising: lowering an anchor pile, a pile support, and an underwater hammer to a seabed floor; mounting the underwater hammer on the seabed floor; placing a lower end of the anchor pile into a pile grip along the pile support at a position that the anchor pile is to be driven into the seabed floor; aligning the underwater hammer with the anchor pile; and causing the underwater hammer to drive the anchor pile into the seabed floor to a desire depth and at a desired angle of inclination.

[0079] S. The method of R, further comprising: coupling a first end of a mooring line to a coupling mechanism associated with the anchor pile; and wherein the desired angle of inclination is determined based at least in part on a departure angle of the mooring line from a monopile structure coupled to a second end of the mooring line, the second end opposite the first end.

[0080] T. The method of R, further comprising transporting the anchor pile, the pile support, and the underwater hammer to a desired location along a surface of a body of water via an installation vessel.

[0081] U. The method of R, wherein the pile support is at an angle of inclination between five and forty five degrees from vertical.

[0082] While the example clauses described above are described with respect to one particular implementation, it should be understood that, in the context of this document, the content of the example clauses can also be implemented via a method, device, system, a computer-readable medium, and / or another implementation. Additionally, any of examples may be implemented alone or in combination with any other one or more of the other examples.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A system, comprising: a fixed marine platform to host a wind turbine; at least one mooring line coupled to the fixed marine platform, the at least sone mooring line having a departure angle; and at least one anchor pile driven into a seabed floor at an angle of batter that is equal to or less than a threshold number of degrees from the departure angle, each of the at least one anchor piles having a coupling mechanism to secure a corresponding one of the at least one mooring lines.

2. The system of claim 1, wherein the seabed floor is between a depth of about fifty meters and one hundred and twenty meters under a surface of water.

3. The system of claim 1, wherein: an individual one of the at least one mooring lines comprises a group of two or more mooring lines; and the departure angle is an angle of a center line associated with the two or more mooring lines of the group of two or more mooring lines.

4. The system of claim 1, wherein: each anchor pile comprises a first anchor pile driven into the seabed floor at the angle of batter and a second anchor pile driven into the seabed floor at the angle of batter; and the first anchor pile is physically coupled to the second anchor pile.

5. The system of claim 1, wherein the threshold number of degrees is one or more of the following threshold number of degrees: five degrees; ten degrees; fifteen degrees; orthirty degrees.

6. The system of claim 1, wherein the angle of batter is greater than the angle of departure angle and less than a threshold angle of batter.

7. The system of claim 1, wherein the angle of batter is less than or equal to the departure angle.

8. A structure for hosting a wind turbine, comprising: a mooring line physically coupled to the monopile structure; and an anchor pile having a coupling mechanism to secure the mooring line to the anchor pile, the anchor pile driven into a seabed floor at an angle of batter that is less than a threshold angle of batter.

9. The monopile structure of claim 8, wherein the threshold angle of batter is an angle of line inclination associated with the mooring line.

10. The monopile structure of claim 8, wherein the structure for hosing the wind turbine is fully restrained marine platform embedded in a seabed floor.

11. The monopile structure of claim 8, wherein the mooring line is physically coupled to the monopile structure above a water line.

12. The monopile structure of claim 18, wherein the mooring line is physically coupled to the monopile structure below a water line.

13. The monopile structure of claim 8, wherein the angle of batter is equal to or less than a threshold number of degrees from the angle of line inclination.

14. The monopile structure of claim 8, wherein the anchor pile comprises a first anchor pile driven into the seabed floor at the angle of batter and a second anchor pile driven into the seabed floor at the angle of batter.

15. The monopile structure of claim 14, wherein the first anchor pile is physically coupled to the second anchor pile by a horizontal plate and the coupling mechanism is physically coupled to the horizontal plate.

16. The monopile structure of claim 8, wherein: the mooring line comprises two or more mooring lines; and the angle of line inclination is an angle associated with a center line between the two or more mooring lines.

17. The monopile structure of claim 8, wherein the mooring line comprises a first mooring line and a second mooring line, the first mooring line coupled to the structure at a first evaluation from the seabed floor and the second mooring line coupled to the structure at a second evaluation form the seabed floor, the second elevation different than the first elevation.

18. A method compri sing : lowering an anchor pile, a pile support, and an underwater hammer to a seabed floor; mounting the underwater hammer on the seabed floor; placing a lower end of the anchor pile into a pile grip along the pile support at a position that the anchor pile is to be driven into the seabed floor; aligning the underwater hammer with the anchor pile; and causing the underwater hammer to drive the anchor pile into the seabed floor to a desire depth and at a desired angle of inclination.

19. The method of claim 18, further comprising: coupling a first end of a mooring line to a coupling mechanism associated with the anchor pile; and wherein the desired angle of inclination is determined based at least in part on a departure angle of the mooring line from a monopile structure coupled to a second end of the mooring line, the second end opposite the first end.

20. The method of claim 18, further comprising transporting the anchor pile, the pile support, and the underwater hammer to a desired location along a surface of a body of water via an installation vessel.

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