An offshore wind turbine support structure, an installation support, and a method of constructing an offshore wind turbine support structure.

Abstract

An offshore wind turbine support structure comprising: a monopile; an external working platform; and a grouted connection to directly connect the external working platform to the monopile. An installation support for temporarily connecting an external working platform to a monopile to enable a grouted connection to be installed between the external working platform and the monopile, the support comprising: an interface configured to removably connect to the external working platform via one or more fixtures; and a guide configured to guide a connection region of the external working platform against a connection region of a monopile. A method of constructing an offshore wind turbine support structure, the method comprising: directly connecting an external working platform to a monopile by a grouted connection.

Description

[0001] TITLE

[0002] An offshore wind turbine support structure, an installation support, and a method of constructing an offshore wind turbine support structure.

[0003] TECHNICAL FIELD

[0004] Embodiments of the present disclosure relate to an offshore wind turbine support structure, an installation support, and a method of constructing an offshore wind turbine support structure. Some relate to a grouted connection directly connecting an external working platform to a monopile.

[0005] BACKGROUND

[0006] A commonly used foundation type for an offshore wind turbine comprises a monopile which is driven into the seabed.

[0007] Offshore wind turbines typically have an external working platform that allows a user (e.g., a person installing or maintaining the offshore wind turbine) access to external and internal portions of an offshore wind turbine. External working platform may sometimes be referred to as a main access platform or a main external platform. It provides the primary means of access to the wind turbine support structure.

[0008] The external working platform is typically connected to a transition piece which is in turn connected offshore to a monopile via a bolted or grouted connection. Where a transition piece is not used, the external working platform is typically connected offshore to a monopile by using bolted connections. Bolted connections can be difficult to connect due to the fabrication and fitment tolerances of the monopile and the external working platform, and the amount of time, and hence cost, that is required for offshore activities to perform the bolted connections. Furthermore, bolted connections can corrode due to the marine environment or loosen over time. Therefore, they require offshore inspection and maintenance which add significantly to the life cycle costs. Alternatives to bolted connections such as welding typically require significant offshore construction time, are difficult to achieve quality control and require coating reinstatement which can be costly. In addition, there are significant loads associated with offshore wind turbines which need to be transferred to the monopile by a transition piece when a transition piece is used. Omitting the transition piece provides a simple solution to reduce the complexity in the load path. Connecting the external working platform directly to the monopile allows for omission of the transition piece and is therefore desired.

[0009] It is the object of the present invention to overcome one or more of the above referenced problems.

[0010] SUMMARY

[0011] Some, not necessarily all, example embodiments of the present disclosure relate to an offshore wind turbine support structure comprising: a monopile; an external working platform; and a grouted connection to directly connect the external working platform to the monopile.

[0012] The grouted connection provides a more flexible connection between the external working platform and the monopile. One of the key advantages is that a grouted connection helps to deal with any fabrication tolerances of the connected components (e.g., the external working platform and the monopile) compared to other connection types such as bolted connections. The grouted connection also provides improved corrosion resistance to marine environment (e.g., to sea water) than bolted connections and has significantly reduced inspection and maintenance requirements over the lifetime of the structure. Grouting is a cost-effective solution that can be achieved quickly. That is, there is no requirement for a significant amount of offshore construction, which can be time consuming and expensive.

[0013] At least part of the structural load of the external working platform may pass to the monopile via the grouted connection. The grouted connection may provide uniform distribution of loads through the grouted connection. The grouted connection may provide redundancy in the distribution of loading. The grouted connection thereby provides an improved structural connection between the external working platform and the monopile.

[0014] The connection region of the monopile and a connection region of the external working platform may overlap along a longitudinal axis of the wind turbine. The grouted connection may be formed between the overlapping connection regions. This provides additional protection to the grouted connection (e.g. from corrosion due to the marine environment). The space between overlapping connection regions may form an annulus and the grouted connection may be formed in the annulus. This ensures that the grouted connection has a regular structure thereby reducing potential defects in the grouted connection.

[0015] The connection region of the monopile may comprise an external surface of the monopile.

[0016] The offshore wind turbine support structure may comprise a secondary connection to directly connect the external working platform to the monopile. The secondary connection may comprise at least one of a welded connection, a male-female connection or a direct bearing support. The secondary connection in addition to the grouted connection provides an improved connection between the monopile and the external working platform than the grouted connection alone.

[0017] The grouted connection extends at least 1 metre along the longitudinal axis of the wind turbine. This may ensure that the grouted connection provides adequate structural support.

[0018] Some, not necessarily all, example embodiments of the present disclosure relate to an installation support for temporarily connecting an external working platform to a monopile to enable a grouted connection to be installed between the external working platform and the monopile, the support comprising: an interface configured to removably connect to the external working platform via one or more fixtures; and a guide configured to guide a connection region of the external working platform against a connection region of a monopile.

[0019] The guide provides an improved method of locating the external working platform and the monopile. The interface enables the support to be removably connected to the external working platform.

[0020] The interface may comprise a male female connector. The male female connector may comprise a bolted connection.

[0021] The guide may comprise a levelling surface configured to align the connection regions in a dimension perpendicular to the longitudinal axis of the wind turbine. The levelling surface improves the connection between the monopile and the external working platform. The guide may comprise a sloped surface configured to align the connection regions in a dimension parallel to the longitudinal axis of the wind turbine.

[0022] The sloped surface may comprise a chamfer.

[0023] Some, not necessarily all, example embodiments of the present disclosure relate to an installation system comprising: the installation support; and an installation frame, the installation frame connectable to the installation support.

[0024] The installation frame enables both an external working platform and internal platform to be installed simultaneously.

[0025] The installation frame may comprise a hoist configured to lift and / or lower the installation support.

[0026] The installation frame may comprise a grouting station connectable to a grouting supply.

[0027] Some, not necessarily all, example embodiments of the present disclosure relate to a method of constructing an offshore wind turbine support structure, the method comprising: directly connecting an external working platform to a monopile by a grouted connection.

[0028] Directly connecting may comprise guiding a connection region of the external working platform against a connection region of the monopile.

[0029] Directly connecting may comprise forming a grouted connection between the connection regions.

[0030] The grouted connection may extend at least 1 metre along the longitudinal axis of the wind turbine.

[0031] Directly connecting may comprise guiding the connection region of the external working platform against a connection region of the monopile using the installation support.

[0032] Directly connecting may comprise aligning the connection regions in a dimension perpendicular to the longitudinal axis of the wind turbine using the installation support. The method may comprise removing the installation support once the direct connection is formed.

[0033] Directly connecting may comprise using the installation support connected to the installation frame; and using the installation frame to directly connect an internal platform to the monopile.

[0034] The method may comprise removing the installation frame once external working platform and, optionally, the internal platform are directly connected to the monopile.

[0035] BRIEF DESCRIPTION

[0036] Some examples will now be described with reference to the accompanying drawings in which:

[0037] FIG.1 illustrates a schematic of an offshore wind turbine support structure;

[0038] FIG. 2 illustrates an example offshore wind turbine;

[0039] FIG. 3A illustrates a cross-sectional side view of an example of an offshore wind turbine support structure;

[0040] FIG. 3B illustrates a cross-sectional top view of the offshore wind turbine support structure of FIG. 3A;

[0041] FIG. 4A shows a top view of an example installation support;

[0042] FIG. 4B shows a side view of the example installation support of FIG. 4A;

[0043] FIG. 4C shows a rear view of the example installation support of FIGs 4A and 4B; and

[0044] FIGs 5A to 5E show an example method of constructing an offshore wind turbine support structure.

[0045] It should be understood that the drawings are not necessarily to scale.

[0046] DETAILED DESCRIPTION

[0047] Embodiments of the invention relate to an offshore wind turbine support structure 100 (i.e., an offshore wind turbine foundation 100) comprising a monopile 110, an external working platform 130 and a grout / grouted connection 120 to directly connect the external working platform 130 to the monopile 110.

[0048] The grouted connection 120 directly connecting the external working platform 130 to the monopile 110 may comprise no other intervening component between the external working platform 130 and the monopile 110 (e.g., other than the grouted connection 120). For example, the external working platform 130 may be in direct contact with the grouted connection 120 and the grouted connection 120 may be in direct contact with the monopile 110.

[0049] FIG.1 illustrates a schematic cross-section of the offshore wind turbine support structure 100. The offshore wind turbine support structure 100 comprises the monopile 110 and the external working platform 130. The monopile 110 is directly connected to the external working platform 130 by the grouted connection 120.

[0050] The monopile 110 (i.e., a monopile foundation 110) may be the portion of a wind turbine support structure 100 that is at least partly driven into the seabed. The monopile 110 may be substantially cylindrical in shape. The monopile 110 may be configured to support the structural load of the offshore wind turbine. The monopile 110 may be configured to transfer the structural load to the seabed.

[0051] The external working platform 130 may comprise a structure configured to enable one or more users to access the exterior of an offshore wind turbine (e.g., to provide maintenance to the exterior of the offshore wind turbine).

[0052] The grouted connection 120 may be at least partly formed of grout. Grout is a dense fluid that hardens over time. Once hardened, the grout may form a load transfer medium. The grouted connection 120 may be formed from a cementitious grout (i.e., the grout may comprise cement). The grouted connection 120 may comprise water, cement, and sand. The grouted connection 120 may be a proprietary cementitious grout. The proprietary cementitious grout may comprise water, cement and at least one of a polymer, additive, pigment, and fine-graded aggregate. The grouted connection 120 may be formed at least in part from Portland cement (e.g., Ordinary Portland cement). The grouted connection 120 formed from the Portland cement may have a compressive strength of up to 80 Megapascals. The grouted connection 120 formed from the Portland cement may have a 3-day compressive strength of up to 80 Megapascals. The grouted connection 120 formed from the Portland cement may have a 7-day compressive strength of up to 80 Megapascals. The grouted connection 120 formed from the Portland cement may have a 14-day compressive strength of up to 80 Megapascals. The grouted connection 120 formed from the Portland cement may have a 28-day compressive strength of up to 80 Megapascals.

[0053] The grouted connection 120 may be formed at least in part from MasterFlow 9500 grout. The grouted connection 120 may be formed at least in part from MasterFlow 9800 grout.

[0054] The grouted connection 120 may be formed from an epoxy grout. The epoxy grout may comprise one or more epoxy-based resins.

[0055] The grouted connection 120 directly connecting the monopile 110 and the external working platform 130 has the advantage of greater flexibility to a user providing the direct connection. For example, when the tolerances of the monopile 110 and external working platform 130 are greater than expected (e.g., due to fabrication accuracy of the monopile 110 or external working platform 130) a bolted connection may not be suitable to form the direct connection 120. The flexibility provided by a grouted connection 120 provides a connection that can overcome these issues.

[0056] Furthermore, a grouted connection 120 provides better corrosion resistance (e.g., to the marine environment) than a bolted connection. It also has reduced inspection and maintenance requirements compared to other types of connections.

[0057] At least part of the structural load of the external working platform 130 (e.g., from the weight of the external working platform 130) may pass to the monopile 110 via the grouted connection 120. In some examples, the grout connection 120 may support all of the structural load of the external working platform 130. That is to say that the grouted connection may be configured to support all of the self-weight of the external working platform along with expected live loads on the external working platform. Providing the external working platform 130 to couple with the monopile 110 in this manner also means that the external working platform 130 is not in the load path of a tower 212 of the wind turbine. That is to say that the load of the tower 212 does not pass through the external working platform (and therefore the grouted connection 120).

[0058] Each of the monopile 110 and the external working platform 130 may comprise a connection region 120. The connection regions may be configured to overlap a longitudinal axis of the offshore wind turbine support structure 100.

[0059] The grouted connection 120 may be formed, at least in part, between the overlapping connection regions. For example, the overlapping connection regions may form one or more spaces / cavities into which the grouted connection 120 can be formed.

[0060] In some examples, the overlapping connection regions form a space in the shape of an annulus. The grouted connection 120 may be formed in the annulus. In some examples, the annulus may be continuous. In other examples, the annulus may comprise one or more spaces separated from one other. The annulus does not need to be of uniform width all the way around. That is to say that one side of the annulus may have a smaller width compared with the other side. The difference in the annulus width may result from manufacturing and fabrication tolerances. For example, the monopile may not be perfectly circular and / or the connecting region of the external working platform 130 may not be perfectly circular. In some examples, the tolerances of the monopile 110 and / or the external working platform 130 may be 50mm. Providing the grouted connection 120 between the external working platform 130 and the monopile 110 obviates possible issues relating to manufacturing and fabrication tolerances.

[0061] The connection region of the monopile 110 may comprise an external surface of the monopile 110. The connection region of the external working platform 130 may comprise an internal surface of the external working platform 130.

[0062] The grouted connection may extend at least 0.5 metres along the longitudinal axis of the offshore wind turbine support structure 100. The grouted connection may extend at least 0.75 metres along the longitudinal axis of the offshore wind turbine support structure 100. The grouted connection 120 may extend at least 1 metre along the longitudinal axis of the offshore wind turbine support structure 100. The grouted connection may extend between 0.5 metres to 2 metres along the longitudinal axis of the offshore wind turbine support structure 100. The grouted connection 120 may extend around 1.5 metres along the longitudinal axis of the offshore wind turbine support structure 100. The grouted connection 120 may extend up to 5 metres along the longitudinal axis of the offshore wind turbine support structure 100. The grouted connection 120 may extend around 10 metres along the longitudinal axis of the offshore wind turbine support structure 100. The inventor has found that the grouted connection 120 extending at least 1 metre along the longitudinal axis provides sufficient structural support of the external working platform 130.

[0063] The size of the grouted connection 120 may depend on the structural load that the grouted connection 120 is required to support. In some examples, the grouted connection 120 may extend at least 5 metres along the longitudinal axis of the offshore wind turbine support structure 100. In other examples, the grouted connection 120 may extend at least 10 metres along the longitudinal axis of the offshore wind turbine support structure 100.

[0064] In addition to the grout connection 120, the offshore wind turbine support structure 100 may comprise a secondary connection (not shown) to directly connect the external working platform 130 to the monopile 110. The secondary connection may comprise at least one of a welded connection, a male-female connection or a direct bearing support.

[0065] FIG. 2 illustrates an example offshore wind turbine 200. The offshore wind turbine 200 comprises a wind turbine generator 210 and the offshore wind turbine support structure 100. As illustrated by the vertical arrows in FIG. 2, the wind turbine support structure 100 may comprise the elements of the offshore wind turbine 200 below the external working platform 130. The wind turbine generator 210 may comprise the elements of the offshore wind turbine 200 that are above the external working platform 130.

[0066] In the illustrated example, the wind turbine generator 210 comprises a tower 212, a nacelle 214, blades 216, and a hub 218. The offshore wind turbine support structure 100 comprises the external working platform 130, a boat landing system 220, and the monopile 110. The boat landing system 220 may be a structure in which vessels (e.g., boats) can dock (e.g., be attached) to allow a user to access the offshore wind turbine support structure 100 from the vessel.

[0067] As shown in FIG. 2, the monopile 110 may be driven into the seabed 240. Scour protection 250 may be provided around the monopile 110 at the seabed 240. The boat landing system 220 may be located on the monopile 110 such that the boat landing system 220 is in contact with the surface of the sea 230.

[0068] FIG. 3A illustrates a cross-sectional side view of an example of an offshore wind turbine support structure 100. The offshore wind turbine support structure 100 comprises a monopile 110 and an external working platform 130. The monopile 110 is directly connected to the external working platform 130 by the grouted connection 120.

[0069] In the example shown in FIG. 3A, the monopile 110 comprises a stopper 310. The stopper 310 is configured to prevent / stop grout from the grouted connection 120 moving down the monopile 110 after the grouted connection 120 has been installed (e.g., whilst the grouted connection 120 is setting). Additionally or alternatively, the stopper 310 may be configured to provide a waterproof seal between the grouted connection 120 and the sea.

[0070] FIG. 3B illustrates a cross-sectional top view of an example of the offshore wind turbine support structure 100 of FIG. 3A. As shown in FIG. 3B, the grouted connection 120 is formed in an annulus (e.g., an annulus shaped cavity) between the external working platform 130 and the monopile 110.

[0071] FIG. 4A shows a top view of an example installation support 400 for temporarily connecting an external working platform 130 to a monopile 110 to enable a grouted connection 120 to be installed between the external working platform 130 and the monopile 110. FIG. 4B shows a side view of the example installation support 400 of FIG. 4A. FIG. 4C shows a rear view of the example installation support of FIGs 4A and 4B.

[0072] The installation support 400 comprises an interface 410 configured to removably connect to the external working platform 130 via one or more fixtures 412. The installation support 400 comprises a guide 420 configured to guide a connection region 132 of the external working platform 130 against a connection region 112 of a monopile 110.

[0073] The interface 410 may comprise a male female connector. As shown in the example illustrated in FIGs 4A to 4C, the male female connector may be a bolted connection. It should be understood that the interface 410 may comprise any removably connectable connector. As shown in FIG. 4B, the guide 420 may comprise a levelling surface 422 configured to align the connection regions 112, 132 in a dimension perpendicular to the longitudinal axis of the wind turbine (e.g., the tower of the wind turbine).

[0074] As shown best in FIG. 4B, the guide 420 may comprise a sloped surface 424 configured to align the connection regions 112, 132 in a dimension parallel to the longitudinal axis of the wind turbine. The sloped surface 424 may comprise a chamfer.

[0075] FIG. 4B shows that the example installation support 400 comprises a connector 430 configured to enable the installation support 400 to be connected to an installation frame (described below).

[0076] FIGs 5A to 5E show an example method of constructing / manufacturing an offshore wind turbine support structure.

[0077] FIG. 5A shows an example installation system 500 comprising an installation frame 510. The installation frame 510 may be used to directly connect the external working platform 130 to the monopile 110.

[0078] The installation system 500 may comprise the installation frame 510 and the installation support 400. The installation frame 510 may be connectable to the installation support 400. The installation frame 510 may comprise one or more lifting points configured to attach the installation frame 510 to a crane. For example, a crane of a vessel may position the installation system 500 into the configuration shown in FIG. 5A by the one or more lifting points.

[0079] The installation frame 510 may comprise one or more hoists 514 configured to lift and / or lower the installation support 400. The one or more hoists 514 may comprise one or more winches. FIGs 5A to 5D show two hoists 514 configured to lift and / or lower the installation support 400 denoted by reference signs 514a and 514b. In some examples, the installation frame 510 comprises three or more hoists 514. The hoists 514 may be evenly spaced at the periphery of the installation frame 510. For example, in embodiments in which the installation frame 510 comprises three hoists 514, the hoists 514 may be spaced around the periphery at 120 degree intervals. Additionally or alternatively, the hoists 514 may be located on an upper surface of the installation frame 510. The installation frame 510 may be connectable to an internal platform 550 (that is different from the external working platform 130) via one or more of the hoists 515. As shown in FIGs 5A to 5D, the internal platform 550 is connected to the installation frame 510 via two hoists denoted by reference signs515a and 515b. The one or more hoists 515 may be configured to lift and / or lower the internal platform 550. The one or more hoists 515 may comprise one or more winches. In some examples, the installation frame 510 comprises three or more hoists 515. The hoists 515 may be evenly spaced at the periphery of the installation frame 510. For example, in embodiments in which the installation frame 510 comprises three hoists 515, the hoists 515 may be spaced around the periphery at 120 degree intervals. Additionally or alternatively, the hoists 515 may be located on a lower surface of the internal platform 550.

[0080] The installation frame 510 may comprise a grouting station 512 connectable to a grouting supply. The grouting supply may be located on a vessel (e.g., a boat) or the installation frame itself. The grouting supply may be connectable to the grouting station 512 via a conduit (e.g., a pipe).

[0081] The installation frame 510 may comprise one or more supports 516a, 516b. The one or more supports 516a, 516b may be configured to support the installation frame 510 against the monopile 110. In some examples, the installation frame 510 may comprises three or more supports 516a, 516b. The supports 516a, 516b may be evenly distributed at the periphery of the installation frame 510. The supports 516a, 516b may be located on a lower surface of the installation frame 510.

[0082] FIG. 5A shows an initial step of the example method of constructing an offshore wind turbine support structure 100. As shown in FIG. 5A, the external working platform 130 is connected to the installation frame 510 via the installation support 400 and the hoists 514a, 514b. The internal working platform 550 is connected to the installation frame 510 via the hoists 515a, 515b. It should be understood that in some examples, the internal working platform 550 is not connected to the installation frame 510 during the initial step.

[0083] In the initial step, the installation frame 510 lifts / raises the external working platform 130 from a vessel. The initial step may also comprise lifting the internal platform 550 from a vessel (either the same or separate from the vessel from the which the external working platform 130 was lifted from). The installation frame 400 may then be positioned above (e.g., directly over) the monopile 110. FIG. 5B shows a second step of the example method of constructing an offshore wind turbine support structure 100. Once the installation frame 510 is located above the monopile 110, the second step comprising lowering the installation frame 510 against the monopile 110 such that the supports 516a, 516b contact the monopile 110 (e.g., an upper surface of the monopile 110). The supports 516a, 516b may be configured to temporarily connect the installation frame 510 to the monopile 110. The temporary connection may comprise one or more of a hydraulic clamp or latch connection (not shown).

[0084] FIG. 5C shows a third step of the example method of constructing an offshore wind turbine support structure 100. In the third step, the external working platform 130 is lowered into position against the monopile 110. The grouted connection 120 between the monopile 110 and the external working platform 130 is formed / installed in this step. In some examples, once the external working platform 130 has been lowered into position, one or more users may form the grouted connection 120.

[0085] FIG. 5D shows a fourth step of the example method of constructing an offshore wind turbine support structure 100. In the fourth step, the internal platform 550 is lowered into position against an internal structure of the monopile 110. The connection between the internal platform 550 and the monopile 110 is formed in this step. The connection may be at least one of a malefemale, welded, or grouted connection.

[0086] In some examples, the fourth step can occur before the third step. In some examples, the third step and the fourth step can occur simultaneously. The skilled person should understand that the third step and the fourth step are independent from one another.

[0087] FIG. 5E shows a fifth step of the example method of constructing an offshore wind turbine support structure 100. In the fifth step, upon completion of the installation of the external working platform 130 and optionally the internally platform 550, the installation frame 510 is removed.

[0088] Whilst the above examples relate to a grouted connection 120 for providing a direct connection between a monopile 110 and an external working platform 130 of an offshore wind turbine support structure 100, it should be understood that the grouted connection 120 could be provided between a monopile 110 and an external working platform 130 of other structures (e.g., a meteorological mast). CLAUSES:

[0089] 1 . An offshore wind turbine support structure comprising: a monopile; an external working platform; and a grouted connection to directly connect the external working platform to the monopile.

[0090] 2. The offshore wind turbine support structure of clause 1 , wherein at least part of the structural load of the external working platform passes to the monopile via the grouted connection.

[0091] 3. The offshore wind turbine support structure of clause 1 or 2, wherein a connection region of the monopile and a connection region of the external working platform overlap along a longitudinal axis of the wind turbine; and wherein the grouted connection is formed between the overlapping connection regions.

[0092] 4. The offshore wind turbine support structure of clause 3, wherein space between overlapping connection regions form an annulus and the grouted connection is formed in the annulus.

[0093] 5. The offshore wind turbine support structure of clauses 3 or 4, wherein the connection region of the monopile comprises an external surface of the monopile.

[0094] 6. The offshore wind turbine support structure of any preceding clause, comprising a secondary connection to directly connect the external working platform to the monopile.

[0095] 7. The offshore wind turbine support structure of clause 6, wherein the secondary connection comprises at least one of a welded connection and a male-female connection.

[0096] 8. The offshore wind turbine support structure of any preceding clause, wherein the grouted connection extends at least 1 metre along the longitudinal axis of the wind turbine.

[0097] 9. An installation support for temporarily connecting an external working platform to a monopile to enable a grouted connection to be installed between the external working platform and the monopile, the support comprising: an interface configured to removably connect to the external working platform via one or more fixtures; and a guide configured to guide a connection region of the external working platform against a connection region of a monopile.

[0098] 10. The installation support of clause 9, wherein the interface comprises a male female connector.

[0099] 11. The installation support of clause 10, wherein the male female connector comprises a bolted connection.

[0100] 12. The installation support of clause 9, 10 or 11 , wherein the guide comprises a levelling surface configured to align the connection regions in a dimension perpendicular to the longitudinal axis of the wind turbine.

[0101] 13. The installation support of any of clauses 9 to 12, wherein the guide comprises a sloped surface configured to align the connection regions in a dimension parallel to the longitudinal axis of the wind turbine.

[0102] 14. The installation support of clause 13, wherein the sloped surface comprises a chamfer.

[0103] 15. An installation system comprising: the installation support of clauses 9 to 14; and an installation frame, the installation frame connectable to the installation support.

[0104] 16. The installation system of clause 15, wherein the installation frame comprises a hoist configured to lift and / or lower the installation support.

[0105] 17. The installation system of clause 15 or 16, wherein the installation frame comprises a grouting station connectable to a grouting supply.

[0106] 18. A method of constructing an offshore wind turbine support structure, the method comprising: directly connecting an external working platform to a monopile by a grouted connection. 19. The method of clause 18, wherein directly connecting comprises guiding a connection region of the external working platform against a connection region of the monopile.

[0107] 20. The method of clause 18 or 19, wherein directly connecting comprises forming a grouted connection between the connection regions.

[0108] 21. The method of any of clauses 18, 19, or 20, wherein the grouted connection extends at least 1 metre along the longitudinal axis of the wind turbine.

[0109] 22. The method of any of clauses 19 to 21 , wherein directly connecting comprises guiding the connection region of the external working platform against a connection region of the monopile using the installation support of any of clauses 9 to 14.

[0110] 23. The method of any of clauses 19 to 22, wherein directly connecting further comprises aligning the connection regions in a dimension perpendicular to the longitudinal axis of the wind turbine using the installation support of any of clauses 9 to 14.

[0111] 24. The method of any of clauses 18 to 23, comprising removing the installation support of any of clauses 9 to 14 once the direct connection is formed.

[0112] 25. The method of any of clauses 18 to 24, wherein directly connecting comprises using the installation support of any of clauses 9 to 14 connected to the installation frame of any of clauses 15 to 17; and using the installation frame to directly connect an internal platform to the monopile.

[0113] End of detailed description.

Claims

CLAIMS:1 . An offshore wind turbine support structure comprising: a monopile; an external working platform; and a grouted connection to directly connect the external working platform to the monopile, wherein the grouted connection is configured to support all of the structural load of the external working platform.

2. The offshore wind turbine support structure of claim 1 , wherein the grouted connection is formed from one or more epoxy-based resins.

3. The offshore wind turbine support structure of claim 1 or 2, comprising a stopper configured to prevent grout from the grouted connection moving down the monopile after the grouted connection has been installed.

4. The offshore wind turbine support structure of claim 1 , 2 or 3, wherein a connection region of the monopile and a connection region of the external working platform overlap along a longitudinal axis of the wind turbine; and wherein the grouted connection is formed between the overlapping connection regions.

5. The offshore wind turbine support structure of claim 4, wherein space between overlapping connection regions form an annulus and the grouted connection is formed in the annulus.

6. The offshore wind turbine support structure of claims 4 or 5, wherein the connection region of the monopile comprises an external surface of the monopile.

7. The offshore wind turbine support structure of any preceding claim, wherein the grouted connection extends at least 1 metre along the longitudinal axis of the wind turbine.

8. A method of constructing an offshore wind turbine support structure, the method comprising:directly connecting an external working platform to a monopile by a grouted connection, wherein the grouted connection is configured to support all of the structural load of the external working platform.

9. The method of claim 8, wherein the grouted connection is formed from one or more epoxy-based resins.

10. The method of claim 8 or 9, wherein the monopile comprises a stopper configured to prevent grout from the grouted connection moving down the monopile after the grouted connection has been installed.

11. The method of claim 8, 9, or 10, wherein directly connecting comprises guiding a connection region of the external working platform against a connection region of the monopile.

12. The method of any of claims 8 to 11 , wherein directly connecting comprises forming a grouted connection between the connection regions.

13. The method of any of claims 8 to 12, wherein the grouted connection extends at least 1 metre along the longitudinal axis of the wind turbine.

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