Support assembly for offshore installation

Abstract

The invention describes a support assembly (1) for an offshore installation (4, 5), comprising: a transition piece (2) for mounting on an offshore foundation (3); a plurality of support frames (10), each support frame (10) extending radially outward from the transition piece (2); a platform (11) for accommodating equipment of the offshore facility (4, 5), the platform (11) comprising a mounting sleeve (12) dimensioned to fit around the transition piece (2); the mounting sleeve (12) comprises: a plurality of downwardly extending portions (120), each dimensioned to fit between two adjacent support frames (10); and a plurality of transverse cutouts (121), each transverse cutout (121) being formed in the downwardly extending portion (120) and shaped to receive a support frame (10). The invention also describes an offshore wind water electrolysis plant (4, 5) comprising such a support assembly (1) and a method of installing such a support assembly (1).

Description

Background Art

[0001] The support structure of an offshore installation (such as a wind turbine) can be a monopile, tripod, jacket structure, etc., and is carried by a foundation fixed to the seabed. Similarly, the support structure can be a floating foundation. To facilitate access to a conventional offshore wind turbine (i.e., a wind turbine that outputs electricity to the grid), the support structure also carries a service platform, which is installed, for example, on a transition piece between the support structure and the wind turbine, which is familiar to those skilled in the art. The service platform of a conventional wind turbine only needs to be large enough to perform its functions, i.e., to provide a way for personnel to access the wind turbine, to provide space for lifting equipment such as a davit crane, and to provide space for an auxiliary power source during off-grid situations (such as installation, maintenance, etc.). For a 15MW–20MW offshore wind turbine, such a conventional service platform can have dimensions of approximately 20×10 meters and a relatively low weight of approximately 100 metric tons.

[0002] Instead of mainly outputting electricity, an offshore wind turbine can be used to provide electricity to drive a water electrolysis device. Such an offshore wind turbine can be one of many wind turbines in a wind farm or wind power plant, and the hydrogen (H2) generated by the wind turbine can be collected and transported, for example, through a subsea pipeline to an onshore facility. The water electrolyzer and its ancillary equipment (all the modules required to operate the electrolyzer) can be installed directly at the wind turbine. For example, a power converter can be part of the ancillary equipment. The advantage of placing the ancillary equipment near the wind turbine itself is that power transmission losses can be minimized. Thus, for example, the entire output power of the wind turbine can be directly used to drive a PEM, alkaline, or other electrolysis device, thereby maximizing the efficiency of the facility. A facility including an offshore wind turbine and a wind electrolysis device can be referred to as a "decentralized offshore hydrogen production facility" or simply "DOHP".

[0003] However, the total mass of a large water electrolysis device can be approximately several hundred metric tons, and the total area required to accommodate the necessary modules (for example, the modules can be housed in multiple shipping container modules) can be very large, making it challenging to adapt known types of offshore wind turbine support solutions to include a large enough platform.

[0004] In a method, the transition piece is redesigned to include a robust frame at its upper layer, and a platform structure large enough is installed onto the support frame. For a large-capacity electrolysis facility, the platform structure may include two layers. However, this method may significantly increase the total installation cost because the transition piece has to be redesigned to include the support frame, the wind turbine tower has to be connected to the transition piece before the platform structure can be assembled, and the platform structure has to be completed on site before the electrolysis equipment can be installed. The transportation and installation costs (requiring multiple voyages of specialized jack-up vessels and personnel on the platform) may be prohibitively high. In addition, the support frame has to be strong enough and correspondingly requires a large amount of expensive steel. Summary of the Invention

[0005] Accordingly, an object of the present invention is to provide a more economical way to implement an offshore wind electrolysis facility.

[0006] This object is achieved by the claimed support assembly, by the claimed offshore wind-hydrolysis device including such a support assembly, and by the claimed method of installing such a support assembly.

[0007] According to the present invention, a support assembly for such an offshore facility includes: a transition piece for installation onto an offshore foundation; a plurality of support frames, wherein each support frame extends radially outward from the transition piece; a platform for carrying the equipment of the offshore facility, the platform including an installation sleeve sized to fit around the transition piece; and wherein the installation sleeve includes a plurality of downwardly extending sleeve portions, each downwardly extending sleeve portion sized to fit into the space between two adjacent support frames when the platform is lowered onto the transition piece. In other words, the installation sleeve includes vertical cuts between adjacent downwardly extending portions. Each downwardly extending sleeve portion includes a transverse cut, the shape of which is configured to receive a support frame or "fit around a support frame" in a subsequent step when the platform is rotated relative to the transition piece to its final position.

[0008] The offshore facility should be understood to be supported by a foundation such as a monopile and fixed to a transition piece installed on the foundation. At least it can be assumed that the upper part of the transition piece is substantially cylindrical, i.e., the upper part of the transition piece has the shape of a straight cylindrical structure.

[0009] The support frames may be arranged equidistantly around the transition piece. Alternatively, a set of support frames with a closer spacing may be provided in the area corresponding to the heavy-load area of the platform, while a set of support frames with a wider spacing may be provided in the area corresponding to the light-load area of the platform.

[0010] The advantages of the support assembly of the present invention are that it does not require much modification to the established transition piece design. It only needs to include a ring arrangement of support frames, which can be accomplished in a favorably simple manner. In addition, the support frames do not affect the established transportation and installation phases of the transition piece. Therefore, the modified transition piece can be achieved at a favorably low cost. The platform resting on the support frames can also have a favorably simple structure. Since the platform can be loaded at onshore facilities and installed by simply lowering it onto the waiting transition piece and rotating it slightly, the installation cost of the support assembly of the present invention is favorably low.

[0011] In the context of the present invention, an offshore facility should be understood to include a wind turbine and other equipment carried by the platform. Without in any way limiting the present invention, the offshore facility discussed hereinafter is a wind-powered water electrolysis device. Such an electrolysis device can include any number of water electrolyzers (such as PEM electrolyzers, alkaline electrolyzers, etc.) and modules including ancillary equipment, such as power converters, backup power supplies, instrument air sources, hydrogen compressors, etc., as well as specific modules for the type of electrolyzer. These modules can include, for example, a water purifier and a water purifier for a PEM electrolyzer; an electrolyte mixer and an electrolyte separator for an alkaline electrolyzer, etc. All the modules of the electrolysis device are arranged on the platform of the support structure of the present invention. The wind turbine of such an offshore facility can have a rated output power of about 15 MW - 20 MW, of which 90% - 95% can be used to drive the water electrolysis device, and it is assumed hereinafter that the size of the electrolysis device is set to utilize this available power. The remaining 5% - 10% of the wind turbine output power is required to drive various auxiliary devices.

[0012] According to the present invention, an offshore wind-powered water electrolysis device or DOHP includes an example of the support assembly of the present invention, wherein the transition piece of the support assembly is installed on an offshore foundation. The wind turbine of the DOHP is configured to provide power for the water electrolysis device and includes a tower, which is connected to the transition piece of the support assembly. The DOHP also includes a water electrolysis device located on the platform of the support assembly.

[0013] According to the present invention, a method of installing such a support assembly includes the steps of: installing the transition piece on an offshore foundation previously erected at the installation site and transporting the platform to the installation site. Using suitable lifting equipment, the platform is then lowered onto the transition piece to position each downwardly extending sleeve portion of the installation sleeve between two adjacent support frames of the transition piece. In a subsequent step, the platform is rotated relative to the transition piece until each transverse cut of the installation sleeve engages the corresponding support frame, and then, finally, the platform is released from the lifting equipment.

[0014] Particularly advantageous embodiments and features of the invention are given by the dependent claims, as shown in the following description. Features of different claim categories may be combined as appropriate to give other embodiments not described herein.

[0015] As indicated above, there are various types of water electrolyzers. Since PEM water electrolyzers and alkaline water electrolyzers are particularly suitable for wind electrolysis plants, these electrolyzers may be mentioned in the context of the exemplary configurations hereinafter. However, in the case of an offshore wind electrolysis plant, it should be understood that the present invention is equally applicable to other suitable types of water electrolyzers.

[0016] Hereinafter, it may be assumed that the dimensions of the platform can be large, for example, the platform may have an approximately square or rectangular shape with a side length of about 35 meters. The mass of the loaded platform, i.e., the total mass of the platform and the complete electrolysis plant powered by the large-capacity wind turbines as indicated above, should be understood to be approximately 800 metric tons.

[0017] As explained above, the platform is installed on a previously installed transition piece. For this purpose, a jack-up vessel equipped with a suitable crane may be used to transport the platform to the installation site, and the suitable crane may lift the platform from the deck onto the transition piece. In a particularly preferred embodiment of the present invention, the loaded platform is installed on the transition piece, i.e., before being transported to the installation site, the platform has been filled with the electrolysis plant. The expression "loaded platform" should be understood to mean a platform that has carried the electrolysis plant (all electrolyzer modules and ancillary equipment). Hereinafter, any "platform" mentioned may be understood to refer to the loaded platform. As mentioned above, the platform may be loaded at a land-based facility, and before being transported to an offshore facility, a comprehensive test of the functionality of the electrolysis plant may be carried out.

[0018] To facilitate the step of rotating the suspended platform before releasing it from the crane (i.e., before transferring its weight to the transition piece), a tag-line arrangement may be deployed. For example, two or more tag-lines may be connected to appropriate points on the platform. A motor-driven winch at the other end of the tag-line may be actuated as appropriate to unwind or rewind the tag-line. In this way, the spatial position of the platform can be adjusted with high precision. Once the platform is in its final position, i.e., "locked" to the transition piece, the crane is detached from the platform.

[0019] The modules of the electrolysis equipment can be planned on the platform to distribute their weights in an optimal manner. For example, the platform can have a generally "square" shape, with a circular hole in the center for mounting the wind turbine tower, and the modules of the electrolysis equipment are arranged generally uniformly around the tower (in terms of weight). In this way, the weight of the loaded platform can be transferred to the transition piece in an optimal manner and from the transition piece to the base. The terms "mounting sleeve" and "central ring" can be regarded as synonyms and are used interchangeably herein.

[0020] The platform can be constructed in any suitable manner. In a preferred embodiment of the present invention, the platform includes a circular hole for receiving the base of the wind turbine tower such that the wind turbine tower can be lowered into place for connection to the transition piece. The mounting sleeve extends around the hole. The lower diameter of the tower of a 15MW wind turbine can be about 7 - 8 meters, and the diameter of the transition piece at its uppermost part generally corresponds to the diameter of the tower base. In an exemplary embodiment, the platform can include a wire mesh floor enclosed by a railing, and the wire mesh floor is supported by a horizontal frame. To support the frame and the wire mesh floor, the platform preferably includes an arrangement of radially extending floor support beams that extend between the connection points of the mounting sleeve and the frame. For example, the floor support beams can be I-beams or H-beams.

[0021] The mounting sleeve can be implemented in any suitable manner. In a preferred embodiment of the present invention, to ensure sufficient structural strength, the downwardly extending portion of the mounting sleeve extends between an upper horizontal flange and a lower horizontal flange. These flanges can extend outwardly by a desired amount, i.e., the outer diameter of the flange can exceed the diameter of the transition piece by several meters, for example. The inner end of each floor support beam can be surrounded by the upper and lower horizontal flanges of the mounting sleeve and can be welded or otherwise fixed to the mounting sleeve portion.

[0022] The hole in the platform can be slightly larger than the lower diameter of the tower to facilitate access to the tower base and the top of the transition piece. The mounting sleeve can have a diameter large enough to allow the mounting sleeve to "slide onto" the transition piece (to position the support sleeve within each vertical cut of the mounting sleeve). In a preferred embodiment of the present invention, to facilitate the movement of the mounting sleeve on the transition piece, a low-friction interface is provided between the mounting sleeve and the transition piece. In a preferred embodiment of the present invention, a number of sliding pads can be arranged at the inner surface of the mounting sleeve (e.g., at the inner surface of the downwardly extending sleeve portion).

[0023] In a particularly preferred embodiment of the present invention, each support frame includes an upwardly facing contact surface which, during rotation of the platform, receives the downwardly facing contact surface of the corresponding lateral incision. In other words, after the platform has been rotated to its final position, the contact surfaces of each "pair" (support frame and incision) will come into physical contact such that the weight of the platform is transferred through this surface contact to the transition piece and from the transition piece to the base. The contact surfaces may be roughened to achieve a friction fit.

[0024] Existing transition piece designs can be adapted to include support frames. In a preferred embodiment of the present invention, the support frames are at least partially incorporated into the body or wall of the transition piece. For example, the support frame may include a substantially horizontal contact surface and one or more substantially vertical supports, the substantially horizontal contact surface being welded or otherwise fixed to the (one or more) supports and the internal regions of these elements extending into the wall of the transition piece. In a particularly preferred embodiment of the present invention, the support frame extends through the wall of the transition piece and into its interior and is designed such that only a relatively small portion of the support frame extends to the exterior. For example, the support frame design described above - the contact surface and supports visible on the exterior - can be constructed such that the visible portion only comprises a part of the entire support frame structure while the hidden part of the support frame continues in the transition piece body and inside the transition piece. In an exemplary embodiment, the supports extend radially through the interior of the transition piece and converge at the central axis of the transition piece where all the supports can be joined together. In an alternative manner, the supports of each support frame continue in a substantially vertical direction inside the transition piece for a number of meters.

[0025] The support frames and the corresponding lateral incisions (collectively hereinafter referred to as "platform support features") can have any suitable shape and size. For example, the support frame may include a horizontally projecting element and a number of vertical supports, and the lateral incision includes a complementary shape such that when the platform is brought to its final position, all the complementary surfaces of the support features meet or engage. In a preferred embodiment of the present invention, the support frames and the lateral incisions are formed to allow the platform to rotate at least 5°, more preferably to allow a rotation of approximately 10°.

[0026] In a preferred embodiment of the present invention, the total contact area of the support assembly - i.e., the total area of the contact surfaces of the support features - is at least 10 square meters. This total contact area can be distributed over a suitable number of support features, for example ten or twelve support features. Description of the Drawings

[0027] Other objects and features of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawings. It should be understood, however, that the drawings are only designed for the purpose of illustration and are not a limitation of the scope of the present invention.

[0028] Figure 1 Shows a transition piece of an exemplary embodiment of the support assembly of the present invention;

[0029] Figures 2 - 7 Illustrates an exemplary stage of the method of the present invention;

[0030] Figure 8 Shows an exemplary platform of the support assembly of the present invention after installation is completed;

[0031] Figure 9 Shows a partial cross-section through an exemplary embodiment of the support assembly of the present invention;

[0032] Figure 10 and Figure 11 Illustrates another exemplary embodiment of the present invention;

[0033] Figure 12 Shows a partial cross-section through an exemplary embodiment of the support assembly of the present invention;

[0034] Figures 13 - 14 Shows a conventional offshore wind turbine installation.

[0035] In the figures, the same numbers throughout refer to the same objects. The objects in the figures are not necessarily drawn to scale. Detailed Description

[0036] Figure 1 Shows the transition piece 2 of the support assembly of the present invention. The transition piece 2 is designed to support a wind turbine and a wind electrolysis device and is installed on a foundation 3, such as a monopile as shown here. As shown in the figure, the transition piece 2 includes an annular arrangement of outwardly projecting support frames 10. In this exemplary embodiment, ten equally spaced support frames 10 are arranged at the same level around the transition piece 2. The figure also shows a ladder assembly 20 which will allow personnel to move between the platform and a vessel moored to the transition piece 2 after installation is completed.

[0037] An installation vessel 6 (shown schematically), such as a jack-up vessel, can transport the loaded platform 11 to the installation site for installation on the transition piece 2. Figure 2 Shows the platform 11 (previously loaded with all modules of the electrolysis device 4) being lowered into place onto Figure 1 the transition piece 2. In the exemplary embodiment shown here, ten equally spaced vertical cuts 120 in the installation sleeve 12 (or "central ring") of the platform 11 will allow the installation sleeve 12 to pass through the support frames 10 when being lowered above the transition piece 2.

[0038] Figure 3 Shows the platform 11 approaching the level of the support frames 10, andFigure 4 A perspective view of this stage of the assembly procedure is given. Looking from below, Figure 4 the central ring 12 of the platform 11 is shown and the radially extending support beams 13 are indicated, which extend to connection points on the underside of the platform floor. The central ring 12 includes respective radially extending flanges 125, 126 which serve to provide structural strength and to connect to the support beams 13. As can be seen in the figure, the shape of each vertical cut 120 is arranged to receive the support frame 10 or "enclose the support frame 10 for assembly", such that the platform 11 can be lowered to the level of its final position without initially contacting the support frame 10. The vertical cut 120 extends into the lower flange 126 such that when the platform 11 is lowered onto the transition piece 2, the mounting sleeve 12 can pass over the support frame 10.

[0039] Figure 5 An elevation view of the inventive assembly after the platform 11 has been lowered onto the transition piece 2 is shown. Figures 2 - 5 The transverse cuts 121 in the central ring 12 of the platform structure 11 shown in are now aligned with the respective support frames 10. At this stage, the weight of the platform 11 is still borne by the installation vessel crane 60 (as indicated by the lifting cable 63).

[0040] The next stage of the inventive method is to "lock" the platform 11 to the transition piece 2. This is done as Figure 6 illustrated, which shows a perspective view of the loaded platform 11 still suspended from the crane, and a draw wire 61 between the platform 11 and a winch 62 (which can be positioned on the installation vessel). The winch 62 is deployed to pay out and rewind the draw wire 61 as appropriate in order to effect a controlled rotation R of the platform 11 by the desired amount. Figure 7 also aids in illustrating this step, which shows an "internal view" in which only the support frames 10 of the transition piece 2 are visible (the remainder of the transition piece 2 is not visible in order to show the inner surface 12S of the central ring 12 of the platform). When the draw wire winch is actuated as described above, the platform 11 rotates to engage the support frames 10 with their respective transverse cuts 121. As shown, the rotation angle α is determined by the dimensions of the support frames 10 and the transverse cuts 121. In this exemplary embodiment, a shift angle α of 5° is sufficient to engage the contact surfaces 121F of the support frames 10 with their respective transverse cuts 121. Also shown in the figure are low friction blocks 124 (comprising a suitable material, such as nylon) attached to the inner side of the mounting ring to facilitate rotation of the closely fitting central ring 12 around the transition piece 2 during the rotation step.

[0041] Figure 8Shows the platform 11 of the support assembly 1 of the present invention after the installation of the platform 11 is completed. The figure shows that the platform 11 is loaded with an electrolysis device 4 (i.e., the electrolyzer module and the supporting equipment module described above), a davit crane for general lifting operations, etc. The wind turbine tower 50 can now be connected to the transition piece 2 in the usual way, and then, the fully installed and commissioned wind turbine 5 can drive the electrolysis device 4.

[0042] Figure 9 Shows a partial perspective view of the transition piece 2, the support frame 10 and the central ring 12 of the platform 11. In this embodiment, the support frame 10 has a horizontal contact plate 100 carried by two vertical brackets 101. The upper surface of the contact plate 100 is the contact surface 100F of the support frame 10, and will receive the contact surface 121F of the mounting sleeve 12. The shown support frame 10 is located "inside" the vertical cut 120 and beside the sleeve part 12P having a transverse cut 121. The figure shows how the weight of the platform 11 will be transferred to the transition piece 2 (and downward to the base 3) when the platform 11 together with the mounting sleeve 12 is rotationally displaced as shown, causing the support frame 10 to engage with the transverse cut 121 of the sleeve part 12P.

[0043] Figure 10 and Figure 11 Illustrates another embodiment of the present invention. The simplified schematic diagram shows a part of the central ring 12 around the transition piece 2. In this embodiment, each support frame 10 is slightly inclined. For example, the contact surface 100F of the support frame 10 can be inclined about 10° relative to the horizontal plane. Each transverse cut 120 has a corresponding shape, that is, has a contact surface 121F inclined by the same amount. In Figure 10 in, the platform 11 has been lowered to the initial level. In the next stage, the platform 11 rotates as described above so that the central ring 12 rotates relative to the transition piece 2 (indicated by the horizontal arrow), causing the transverse cut 120 to move into place with respect to the respective support frame 10. In Figure 11 the final step shown, the platform 11 is lowered by a further amount (indicated by the vertical arrow) until the inclined contact surface 121F of each cut 120 rests on the inclined surface 100F of its corresponding support frame 10, as shown in the figure. Additional contact surfaces 100F, 121F are provided in the lower regions of the support features 10, 121. In this embodiment, gravity ensures that the platform 11 will never disengage from the support frame 10 even under extreme conditions.

[0044] Figure 12 Shows a partial cross-section through another exemplary embodiment of the support assembly 1 of the present invention. Here, two diametrically opposed support frames 10 are shown, one on the left side of the figure and one on the right side of the figure. The basic structure of the support frame can be, for example, inFigures 1 - 5 and Figure 9 As described in Figure 9 , although the basic idea described herein can of course be applied to a variety of other designs, namely, a large part of the support frame 10 is positioned inside the transition member 2. In the exemplary embodiment shown here, only about one-third of each support frame 10 extends beyond the outer surface of the transition member 2. As shown, the inclined bracket 101 extends downward a relatively long distance into the transition member 2. Here, the lower end of the bracket 101 abuts against an inwardly extending flange 22 positioned at a lower level inside the transition member 2. The upper end of the bracket 101 can be welded to the contact plate 100 of the support frame 10, while the lower end of the bracket 101 can be welded to the inner flange 22. The flange 22 itself can be supported by any suitable fitting (not shown) as the case may be. The figure also shows the possible shape of the slit 24 in the transition member 2, which can be provided to accommodate the vertical bracket 101 and the horizontal contact plate 100 of the support frame 10.

[0045] As shown by the exemplary embodiment described above, the support assembly of the present invention only requires a slight modification to the established transition member design, namely, adding the support frame 10. The platform 11 resting on the support frame 10 can advantageously have a simple structure. Since the platform 11 can be loaded at onshore facilities and installed by simply lowering it onto the waiting transition member 2 and rotating it slightly, the installation cost of the support assembly 1 of the present invention is advantageously low.

[0046] Figure 13 A conventional offshore wind turbine 5 for outputting power to the power grid is shown. The wind turbine tower 50 is connected to the transition member 2, which in turn is installed on the foundation 3, such as the monopile shown here. A typical service platform 7 at the base of the wind turbine tower 50 is shown to facilitate access to the tower by personnel. A davit crane can be permanently fixed to the platform 7, for example, to assist in lifting equipment between the service / installation vessel and the service platform 7. The service platform 7 can also have space for a temporary auxiliary power supply, for example, during the installation of the wind turbine 5, to assist in routine maintenance, etc. during the service life of the wind turbine. Such a relatively compact service platform 7 and transition member 2 can be assembled and transported as a single structure for installation on the foundation 3.

[0047] Figure 14 An offshore wind electrolysis facility is shown. Here, the wind turbine tower is also connected to the transition member 9, which in turn is installed on the foundation. The transition member 9 can have the same as Figures 1 - 12the same dimensions as the conventional transition piece 2, but has been extensively modified to increase the platform support interface 90, as shown here. The platform 8 shown in the figure is large enough to accommodate all the modules of the electrolyzer device. To achieve the required surface area, the platform 8 implemented in this example is a two-layer structure. Since the wind turbine tower must be installed on the transition piece 9 before the electrolyzer platform 8 is installed, the platform 8 must be assembled (and transported) independently of the transition piece 9. After the wind turbine tower is installed, the platform 8 can be assembled and then loaded with the electrolyzer and its associated equipment. This prior art solution requires extensive modification to the established transition piece design, which is widely used in conventional power output wind turbines as shown in Figure 13 and, in the support assembly 1 of the present invention shown in Figures 1 - 12 , the established transition piece design only needs to be slightly modified for use. The prior art structures 8, 9 shown here require significantly more materials than the support assembly 1 of the present invention, and the installation costs incurred are also significantly higher than the method of the present invention.

[0048] Although the present invention has been disclosed in the form of preferred embodiments and their variants, it will be understood that many additional modifications and variations can be made thereto without departing from the scope of the present invention. For example, although the support structure is particularly suitable for an offshore wind-hydro electrolysis facility, the platform of the support structure can equally be relatively small, for example, used as a general service platform for an offshore wind turbine that outputs power to the power grid. Here, the ability to "twist-lock" the platform onto the transition piece will also simplify the installation procedure of the offshore wind turbine.

[0049] For clarity, it should be understood that the use of "a" or "an" throughout this application does not exclude a plurality, and "comprising" does not exclude other steps or elements.

Claims

1. A support assembly (1) for a marine installation (4, 5), the support assembly (1) comprising - an adapter (2) for mounting to a marine base (3); - A plurality of support frames (10), wherein, each support frame (10) extends radially outwards from the adapter (2); - a platform (11) for accommodating equipment of the marine installation (4, 5), the platform (11) comprising a mounting sleeve (12) sized to fit around the adapter (2); and wherein the mounting sleeve (12) comprises - a plurality of downwardly extending portions (120), each downwardly extending portion (120) sized to fit between two adjacent support frames (10); and - a plurality of transverse cuts (121), each transverse cut (121) being formed in a downwardly extending portion (120) and each transverse cut (121) shaped to receive a support frame (10).

2. The support assembly according to the preceding claim, wherein, The support frame (10) and the transverse cut (121) are formed to allow the platform (11) to rotate through an angle (α) of up to 10°, more preferably up to 5°.

3. The support assembly according to any one of the preceding claims, wherein The support frame (10) comprises an upwardly facing contact surface (100F) for receiving a downwardly facing contact surface (121F) of a corresponding transverse cut (121).

4. The support assembly according to the preceding claim, wherein, The support frame (10) further comprises a portion (10in) extending into the interior of the adapter (2), the inwardly extending portion (10in) comprising at least 50%, more preferably at least 70% of the entire support frame (10).

5. The support assembly according to any one of the preceding claims, wherein, The platform (11) comprises a circular aperture (110) for accommodating the base of a wind turbine tower (50), and wherein the mounting sleeve (12) extends around the aperture (110).

6. The support assembly according to any one of the preceding claims, wherein, The mounting sleeve (12) comprises a plurality of outwardly extending horizontal flanges (125, 126), and wherein the sleeve portion (120) extends between the upper horizontal flange (125) and the lower horizontal flange (126).

7. The support assembly according to any one of the preceding claims, comprising a low friction interface (124) between the mounting sleeve (12) and the adapter (2).

8. A marine wind-hydroelectrolysis device (4, 5), comprising - The support assembly (1) according to any one of claims 1 to 7, wherein, the adapter (2) of the support assembly (1) is mounted on a marine base (3); - a wind turbine (5) comprising a tower (50) connected to the adapter (2) of the support assembly (1); - a hydroelectrolysis device (4) mounted on the platform (11) of the support assembly (1), and wherein the wind turbine (5) is configured to supply power to the hydroelectrolysis device (4).

9. The offshore wind power electrolysis device according to the previous claim, wherein, The platform (11) and the hydroelectrolysis device (4) have a total mass of approximately 800 metric tons.

10. The offshore wind power electrolysis equipment according to claim 8 or claim 9, wherein, The lower diameter of the wind turbine tower (50) is approximately 8 meters.

11. A method of installing a support assembly (1) according to any one of claims 1 to 7, the method comprising the steps - installing the transition piece (2) onto an offshore base (3) previously erected at the installation site; - transporting the platform (11) to the installation site; - lowering the platform (11) onto the transition piece (2) to position each downwardly extending sleeve portion (120) of the installation sleeve (12) between two adjacent support frames (10) of the transition piece (2); and - rotating the platform (11) relative to the transition piece (2) until each transverse cut (121) of the installation sleeve (12) engages with a corresponding support frame (10).

12. The method according to the preceding claim, comprising a preparatory step of assembling the platform (11) by - providing an installation sleeve (12) sized to fit around the transition piece (2); - providing a platform base plate (14); and - connecting the platform base plate (14) to the installation sleeve (12).

13. The method according to claim 11 or claim 12, comprising a preparatory step of loading the platform (11) with a complete water electrolysis device (4).

14. According to the method according to any one of claims 11 to 13, wherein The step of installing the support assembly (1) is performed using a jack-up vessel (6).

15. The method according to the preceding claim, wherein, The step of rotating the platform (11) relative to the transition piece (2) is performed using a number of guy wires (61), each guy wire (61) extending between the platform (11) and a winch (62) of the jack-up vessel.

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