Wind turbine structure assembly team

Abstract

A support system designed to externally support equipment such as electrolyzers on a wind turbine. A hub, which surrounds or coincides with a tower or turbine transition piece, encircles a central vertical shaft. The hub defines at least one docking bay with brackets to which a support module can be detachably attached, thus creating an equipment platform cantilevered from the hub. When the hub comprises multiple docking bays spaced at angles around the central shaft, a corresponding plurality of support modules are attached to the hub in a petaloid arrangement. In plan view, the docking bays correspond to the respective sides of a polygon. During installation, each support module is suspended from hooks in a docking bay and then pivoted to engage with other brackets in the same bay. The hub can be assembled from sections around the tower during a retrofit operation.

Description

Wind turbine structure assembly team The present invention relates to the use of wind turbine structures to support external auxiliary equipment, such as solar panels and / or electrolyzers for producing hydrogen from seawater. The invention focuses particularly on the challenges of mounting equipment externally on the upright columnar structure of a wind turbine, such structure being its mast or tower, or a transitional support piece between the tower and a foundation. Because electricity generation from wind turbines is variable or intermittent, additional generating capacity may be needed to ensure a continuous supply of sustainable electricity. In this regard, excess energy generated from renewable sources can be used to produce hydrogen, known in this context as "green hydrogen," when electricity supply exceeds other demands. The principle of converting surplus electricity into hydrogen or another gaseous fuel is known as power-to-gas (P2G). Once electricity is converted into gas, it can be used for various purposes.For example, hydrogen produced from renewable energy can be used for power generation, such as fueling a fuel cell to generate electricity when electricity demand would otherwise exceed supply from other sustainable sources. Hydrogen can be produced through a carbon-free electrolysis process in an electrolyzer, in which an electric current splits water into hydrogen and oxygen. Seawater can be electrolyzed using an anode adapted to counteract the formation of chlorine gas from dissolved salt. The electrical energy for electrolysis can be generated by a wind turbine or by auxiliary generating equipment, such as a solar array, which can conveniently be supported by the turbine structure. When a wind turbine is located offshore, whether anchored to the seabed or floating on the surface, its structure can also support auxiliary generating equipment below or above the surface, such as a tidal turbine or a wave energy generator, in addition to solar panels above the surface. Thus, offshore wind turbines represent a substantial opportunity to utilize wind, solar, tidal, and / or wave energy for large-scale green hydrogen production. In principle, electrolyzers can also be supported by a wind turbine structure. Offshore, this eliminates the need for separate platforms or dedicated or adapted surface vessels. However, electrolyzers of sufficient capacity are bulky and therefore must be mounted externally to the wind turbine structure, especially if they are retrofitted onto an existing turbine. Auxiliary generating equipment, such as a solar panel array, also necessarily requires external mounting. Therefore, an external mount or platform is needed for a wind turbine to support auxiliary equipment such as electrolyzers and solar panels. This platform must be capable of supporting a heavy load if used to support electrolyzers, and it must define a usefully large surface area if used to support solar panels. Despite necessarily being large and robust for these purposes, a platform must also be easy to install and remove, especially in a marine environment, whether when constructing or dismantling a wind turbine, or when retrofitting an existing one. Ease of installation and removal is particularly important if the platform is designed to be interchangeable or modular and, therefore, removable and replaceable for repair or maintenance of the equipment it supports. The platform must also complement the wind turbine structure without compromising its integrity or balance. This is especially important in offshore applications, and even more so when used with a floating wind turbine. Of course, it is generally well known how to mount a platform on a wind turbine. For example, platforms are commonly mounted on a wind turbine tower to provide access to the interior of the tower and electrical equipment for maintenance. An example is shown in WO 2016 / 055067, which illustrates that such platforms are usually cantilevered and annular in shape to surround the circular cross-section of the supporting tower. In marine applications, such a platform may be connected to a ladder or staircase, allowing personnel to move from an adjacent vessel. A similar platform may also be located near the turbine nacelle for maintenance of its main moving parts.Conventional wind turbine platforms, such as the one shown in WO 2016 / 055067, do not extend far radially from the tower, instead resembling a walkway around it. While a portion of the platform may cantilever further from the tower to support a small crane or hoist, this part cannot support heavy or bulky equipment. In fact, placing a heavy load on an asymmetrical platform would exert significant bending stresses on the tower and could destabilize the turbine, especially if it is floating offshore. Furthermore, a conventional platform like the one shown in WO 2016 / 055067 is a permanent attachment designed to be installed with the wind turbine and is often pre-installed on the tower before the tower and platform are erected and installed together.The platform is not suitable for refurbishment, nor for removal and replacement while the wind turbine is in service. In EP 2185816, a wind turbine platform is combined with the transition piece that connects the wind turbine tower to a foundation such as a monopile. The platform is complex to assemble and even more difficult to disassemble, as it is an intrinsic part of the wind turbine structure that will be held in place during turbine installation. The platform is also designed for personnel access and not for supporting heavy and bulky equipment. If it were scaled up to handle loads much heavier than those carried by personnel visiting the wind turbine, the platform would become even less practical to operate. EP 2586933 describes methods for assembling a conventional annular work platform on a wind turbine tower. In this example, the work platform is assembled in partially circular sections around the tower to complete a full circle. These sections are suspended from discrete lugs or flanges protruding from the tower. The sections are then permanently secured by welding. Precise alignment of the sections with the flanges is essential, which can be challenging when lifting from an installation vessel floating offshore. Furthermore, the vessel's crane needs access to the entire perimeter of the tower. Relocating the vessel to allow access to the entire perimeter is time-consuming and therefore may not be practical, especially if the vessel is a jack-up type, designed to remain temporarily on the seabed. WO 2016 / 122334 discloses a cantilevered platform mounted on the side of a jacket structure supporting an offshore platform. The cantilevered platform is not intended to permanently support equipment. Instead, it serves as an intermediate holding station for equipment lifted from a vessel by a low-lift crane before being further hoisted by another crane to the platform above. As such, the cantilevered platform is small and so close to sea level that it is susceptible to wave action in rough seas. In contrast, WO 2021 / 136570 discloses a work platform attached to the nacelle of a wind turbine. Consequently, the work platform is located at a considerable height, is limited in area, and cannot support heavy loads. Furthermore, since the work platform is mounted on a moving part of the wind turbine, it would not be practical to connect an electrolyzer on such a platform to a pipeline for hydrogen supply. KR20150111575 discloses a further prior art example of a work platform attached around the tower of a wind turbine. Given these backgrounds, the invention relates to an external equipment support system for a wind turbine, according to claim 1, the system comprising: a hub that surrounds, is coextensive with, or is integrated with a tower or transition piece of the wind turbine and surrounds a central axis of the tower or transition piece, the hub defining at least one coupling bay; and at least one support module that releasably engages with mounting configurations of the coupling bay(s) and is therefore cantilevered from the hub. The hub is configured to rotate relative to the tower or transition piece about the central axis. The support module(s) may be elongated radially outward from the central axis. At least one support module may support electrolyzer equipment and / or a solar cell array. To facilitate reconditioning, the hub may be in parts that, when assembled together, form a continuous loop around the central axis. Preferably, the hub comprises a plurality of mating bays that are angularly spaced around the central axis, in which case a plurality of support modules releasably engage with the mounting configurations of the respective mating bays. The hub may, for example, have a polygonal outline in plan view, with each of the mating bays corresponding to a respective side of the polygonal shape. The support modules may surround the hub in a petaloid arrangement. The hub suitably comprises a tubular wall surrounding the central shaft. When the support module, or each support module, comprises a platform, the hub may comprise a horizontal flange that may substantially abut the platform. The platform and the flange may be substantially at the same horizontal level when the support module is cantilevered from the hub. The mounting configurations for the docking bay(s) are appropriately spaced from, and symmetric about, a plane containing the center axis. The docking bay(s) and the support module have complementary mounting configurations that may include seats to receive respective trunnions. For example, the mounting configurations for the docking bay(s) may include the seats, and the mounting configurations for the support module(s) may include the trunnions. Elongated guides, such as grooves or channels, may extend from the seats and may be open at the end to receive the trunnions. For example, such guides may extend upward and outward from the seats to open outer ends. The mounting configurations of the docking bay(s) may further comprise at least one pivot stop and / or at least one locking configuration positioned at a level below the seats or trunnions. The pivot stop(s) may be opposite a pivot stop of a support module engaged with the hub. Conveniently, the locking configuration(s) may engage with a complementary locking configuration of a support module engaged with the hub following pivoting movement of such support module about the trunnions engaged with the seats. For example, the locking configurations of the docking bay(s) and support module appropriately overlap each other following such pivoting movement. At least one locking element, such as a locking pin, could operate between the locking configurations. The hub is configured to rotate relative to the tower or transition piece around the central axis. For example, an onboard drive can act between the hub and the tower or transition piece to rotate the hub, or an external drive can act on the hub to rotate it. The inventive concept also encompasses a corresponding method of externally supporting equipment on a wind turbine, according to claim 22. The method comprises: releasably engaging a first cantilever support module with a first coupling bay of a hub, the hub encircling, or being coextensive or integral with, a tower or transition piece of the wind turbine and surrounding a central axis of the tower or transition piece; rotating the hub about the wind turbine; and releasably engaging a second cantilever support module with a second coupling bay of the hub. Thereby, a plurality of support modules are releasably engaged with respective coupling bays of the hub that are angularly spaced about the central axis, with the hub rotating about the wind turbine between the installation of successive support modules on the hub.This allows an installation vessel to remain substantially stationary between the installation of successive support modules on the hub. The hub can then be immobilized relative to the wind turbine after the support modules have been installed. Conveniently, the support module(s) can be hung over the hub's coupling bay(s) for engagement with the hub. The support module(s) can then be pivoted around the hanging engagement, after which the locking configurations of the support module(s) and coupling bay can be engaged with each other by virtue of this pivoting motion relative to the hub. A locking element can also be engaged between the locking configurations. At least some equipment can be installed on the support module(s) after attaching the support module(s) to the hub. At least some equipment can also, or instead, be installed on the support module(s) before attaching the support module(s) that carry such equipment to the hub. Initially, the hub can be assembled from two or more parts around the tower or transition piece of the wind turbine. For example, the hub can be assembled during a retrofit operation performed on a previously operational wind turbine. In summary, the invention is exemplified by a standardized cantilever support module, such as a platform, capable of supporting bulky equipment such as hydrogen production infrastructure. The invention thus provides a scalable, modular system that allows for the pre-equipping of standard units, which can then be installed or coupled into bays or faces of a customizable mounting piece or receiving hub. Although the hub could be located at any level on the wind turbine, it is preferably located at or near the base of the wind turbine tower, for example at or near its interface with a foundation, but preferably above the waterline. The hub can be in the form of a polygon, the number of sides of which determines how many cantilever supports (24) can be installed. An installation locking system is also standardized and can be welded or otherwise incorporated into the hub. The embodiments of the invention provide an external platform system for wind turbines, such as offshore wind turbines. The system comprises: a hub on the wind turbine tower, the hub having at least one circumferentially flat face; and at least one cantilever module or support, exemplified as a platform, which is mounted or can be mounted on a flat face of the hub and serves as a mount or interface for the platform. The platform can, for example, be connected to the hub by means of flanges or trunnions by which the platform can be suspended from the hub. The system could comprise at least two distinct platforms mounted on different respective flat faces of the hub. At least one platform can carry an electrolyzer for producing hydrogen. The hub is suitable for integration into the tower or into a transition piece between the foundation and the tower. Alternatively, the hub could be positioned between the tower and a transition piece. In this way, the hub could be coextensive with the tower or the transition piece, or it could be mounted on and surround the tower. The hub is preferably annular in plan view. However, the hub may have a prismatic external shape that is polygonal in horizontal cross-section, the sides of such a polygon corresponding to the respective flat faces and, therefore, to the platforms. The hub is designed to rotate around the tower to facilitate the installation of the cantilevered platforms. After the cantilevered platforms are installed, the hub can be locked in a permanent position. Accordingly, the embodiments of the invention implement a method for installing a cantilevered platform on the exterior of a wind turbine. The method comprises providing a hub on or above the wind turbine tower, wherein the hub circumferentially comprises at least one flat face; lifting a cantilevered platform from or by means of an installation vessel; and assembling the cantilevered platform onto the flat face of the hub. Configuring the hub to rotate around the wind turbine means that the installation vessel does not need to move while cantilevered platforms are installed on respective faces of the hub. The method may further include locking the hub in a permanent position, for example by welding or by inserting pins, shafts, or other locking members that act between the hub and the static structure of the wind turbine. The embodiments of the invention can also implement a method for retrofitting an existing wind turbine to install additional equipment. Such a method comprises: assembling a hub around a wind turbine tower, the hub having at least one flat face; installing a cantilevered platform on the flat face of the hub; and installing additional equipment on the cantilevered platform, either before or after installation of the cantilevered platform. In summary, the invention provides and exploits a system arranged to support equipment, such as electrolyzers, externally on a wind turbine. A hub, which surrounds or is coextensive with a tower or transition piece of the wind turbine, surrounds a central vertical shaft. The hub defines at least one docking bay having mounting configurations to which a support module can be releasably attached, thereby providing an equipment platform cantilevered from the hub. When the hub comprises a plurality of coupling bays angularly spaced around the central axis and corresponding to respective sides of a polygon in plan view, a corresponding plurality of support modules can be engaged with the hub in a petaloid arrangement. In the installation, each support module can be suspended in hook configurations from a docking bay and then pivoted to engage with other docking bay mounting configurations. The hub is suitable for assembly from sections around the tower in a retrofit operation performed on a previously operational wind turbine, or it can be incorporated or added to the structure of a wind turbine before the turbine is first used. In order to make the invention more easily understood, reference will now be made, by way of example, to the accompanying drawings where: Figure 1 is a perspective view of a mounting piece that serves as a bushing for attaching up to six cantilever supports to a wind turbine structure; Figure 2 is a perspective view of one of the cantilever supports that can be attached to the hub of Figure 1; Figures 3a to 3c are a sequence of schematic side views of detail showing a cantilever support of Figure 2 being attached to a bushing of Figure 1; Figure 4 is a perspective view of a wind turbine structure equipped with an array of six cantilever supports from Figure 2 attached to a hub from Figure 1, such supports serving as platforms for electrolyzers topped by arrays of solar panels; Figures 5a and 5b are a sequence of schematic plan views showing an installation vessel attaching a series of cantilever supports to a hub that is in a fixed relationship with respect to a tower of an offshore wind turbine; Figure 6 corresponds to Figures 5a and 5b, but shows the installation vessel that attaches a series of cantilever supports to a hub that rotates around the wind turbine tower; Figure 7 is a detailed schematic plan view showing an on-board drive arrangement for rotating the hub of Figure 6 around the wind turbine tower; Figure 8 is a detailed schematic plan view showing an external drive arrangement for rotating the hub of Figure 6 around the wind turbine tower; Figures 9 and 10 are perspective views of a floating offshore wind turbine structure whose tower is surrounded by an array of cantilever supports of Figure 2, such supports are attached to a hub of Figure 1 located above a buoyant base that supports the wind turbine; Figure 11 is a perspective view of an offshore wind turbine structure whose tower is surrounded by an array of cantilever supports fixed to a hub; the generator is supported, in this case, by a lattice structure that rests on the seabed; and Figure 12 is a group of perspective views of variants where the bushings are configured for fixing three, four, five, and eight cantilever supports. Referring first to Figure 1 of the drawings, a mounting piece or bushing (10) of the invention is made of steel. Centrally, the bushing (10) is traversed by an opening of circular cross-section defined by an internal tubular core (12) that is rotationally symmetric about a vertical central axis (14). In plan view, however, the bushing (10) presents a faceted polygonal outline whose sides are defined by upright faces (16), spaced equiangularly about the central axis (14). In this example of the hub (10), there are six identical faces (16) in a hexagonal arrangement, but other polygonal arrangements are also contemplated, as will be explained. Each side of the polygonal outline, and therefore each face (16), lies on a respective tangent to a common circle centered on the central axis (14). The polygonal shape generally features straight sides, with each side inclined at 120° to its adjacent sides. The faceted shape of the hub (10) is defined by upper and lower flanges (18), (20) extending horizontally from the tubular core (12). These flanges (18), (20) are mutually spaced along the central axis (14). The upper and lower flanges (18), (20) are joined by vertical ribs (22) extending outwards from the core (12), the ribs (22) are spaced angularly around the central axis (14).The ribs (22) are grouped in pairs, one pair per face (16) of the hub (10), and the ribs (22) of each pair lie in mutually parallel vertical planes. In general terms, each face (16) of the bushing (10) is flat, but in detail, each face (16) comprises mounting configurations to serve as a mount or docking station for attaching a respective modular cantilever support (24), as illustrated in Figure 2. The mounting configurations comprise a hook configuration (26) and a bearing plate (28) on each rib (22), and a central recess (30) positioned between each pair of ribs (22) of each face (16). In this example, the mounting configurations are symmetrical or mirror-image about a plane bisecting the face (16) and containing the central axis (14). Each hook configuration (26) is defined by an outer edge portion formed from a rib (22). Specifically, an upper part of the outer edge portion extends upward and outward and contains an outward-opening trim groove (32), which groove (32) also extends upward and outward. The base of the groove (32) defines a partially circular seat (34). The grooves (32) of each pair of ribs (22) are in mutual alignment on a horizontal axis (36) extending between such grooves (32), parallel to the associated face (16). Thus, the seats (34) of their grooves (32) are at the same level and are equidistant from the central axis (14) of the hub (10). Each bearing plate (28) is positioned on an outer edge of a respective rib (22) below the groove (32), near the lower flange (20). An outer side of each bearing plate (28) lies in a vertical plane, orthogonal to the plane of the associated rib (22). The rectangular depressions in the lower flange (20) define the central recesses (30) of the respective faces (16). Each recess (30) extends between the ribs (22) of the associated face (16) and is oriented upwards towards the upper flange (18). A central protrusion (36) projects from the base of each recess (30). Such a protrusion (36) may be integrated with the lower flange (20) or could be removably fixed to the lower flange (20), like a pin. Each recess (30) in the lower flange (20) is opposite a respective rectangular cutout (40) in the outer edge of the upper flange (18), such cutout (40) extending laterally beyond the ribs (22). The cutout (40) thus exposes the hook configurations (26) in the outer edge portions of the ribs (22) when viewed from above. Returning to Figure 2, the left side shows an outward-facing end of the cantilever support (24), and the right side shows an inward-facing end of the cantilever support (24). The inward-facing end of the cantilever support (24) is an interface that can be engaged with any of the faces (16) of the hub (10). These faces (16) thus serve as coupling bays for a corresponding number of cantilever supports (24). The cantilevered support (24) comprises an elongated horizontal platform (42) which, in this example, is generally rectangular in plan view. An optional handrail and equipment mounts (44) that crown the platform (42) are shown. The platform (42) rests on a pair of parallel longitudinal bracing beams (46) that lie in respective vertical planes, such planes being symmetrically spaced around, and parallel to, a longitudinal centerline of the platform (42). Each bracing beam (46) comprises an enlarged, relatively deep, inward-facing portion that decreases in height towards a shallower, outward-facing portion. The inwardly located portions of the bracing beams (46) retain cantilever bracket (24) mounting configurations that complement and cooperate with the mounting configurations (26), (28), (30) of the bushing (10), allowing the cantilever bracket (24) to be mounted on any of the faces (16) of the bushing (10). Specifically, the cantilever bracket (24) mounting configurations comprise a trunnion (48) and a bearing plate (28) on each bracing beam (46), and a tongue (50) positioned centrally between the bracing beams (46). An inner upper portion of each bracing beam (46) supports a respective trunnion (48). The trunnions (48) of each cantilever support (24) extend orthogonally with respect to the planes of their respective bracing beams (46) and, in this example, face inwards towards each other, although in other examples they could face outwards in opposite directions. The trunnions (48) are in mutual alignment about a common horizontal axis (52) that lies parallel to the inward edge of the platform (42). The horizontal spacing between the bracing beams (46) is slightly greater than the horizontal spacing between paired ribs (22) of the hub (10). This allows the pair of bracing beams (46) of a cantilever support (24) to fit snugly around and outside, or encompass, any pair of ribs (22) of the hub (10). The aforementioned cutouts (40) on the outer edge of the upper flange (18), which extend laterally beyond the paired ribs (22), provide lateral clearance to receive the bracing beams (46) around the ribs (22). By doing so, the trunnions (48) on the inner sides of the bracing beams (46) can fit into respective grooves (32) in the hook configurations (26) of the ribs (22). The bracing beams (46) of the cantilever support (24) also support bearing plates (28) that are positioned opposite each other to the bearing plates (28) of the ribs (22). Thus, each bearing plate (28) of the cantilever support (24) is positioned on an inward-facing edge of a respective bracing beam (46), below a trunnion (48). An inward-facing side of each bearing plate (28) lies in a vertical plane, orthogonal to the plane of the supporting bracing beam (46). The tongue (50) is supported by a horizontal crossbar (54) that extends between the bracing beams (46) at the bottom of their inwardly enlarged portions. In addition to supporting the tongue (50), the crossbar (54) completes a box section that stiffens the structure of the bracing beams (46). The tongue (50) is a plate or projection that extends horizontally inward from a central point of the crossbar (54). The tongue (50) is pierced by a central opening (56). The functions of the various mounting configurations will now be explained with additional reference to the sequence of views in Figures 3a to 3c. Figure 3a shows a cantilever support (24) suspended from a crane hoisting rigging (58) and descending towards a face (16) of the hub (10). Figure 3b then shows a first engagement stage of the cantilever support (24) with the hub (10), where a trunnion (48) enters a groove (32) and is received in the partially circular seat (34) at the base of the groove (32). The groove (32) thus serves as a guide for downward and inward movement of the trunnion (48) until it engages with the seat (34). Up to and including this stage, the platform (42) of the cantilever support (24) may be inclined upward and outward, as shown, to facilitate insertion of the trunnions (48) into the grooves (32). Figure 3c shows that when the trunnions (48) are positioned in the seats (34) of the grooves (32) to support the weight of the cantilever support (24), the cantilever support (24) is lowered further to bring the platform (42) into a horizontal orientation. In doing so, the cantilever support (24) pivots about the axis (52) of the trunnions (48), causing the tongue (50) to pass over the recess (30) in the lower flange (20) of the hub (10). The recess (30) thus accommodates the tongue (50), which lies parallel to and above the horizontal base of the recess (30). The pivoting of the cantilever support (24) is completed when the bearing plates (28) of the cantilever support (24) seat against the bearing plates (28) of the hub (10). In this way, the bearing plates (28), which are abutting each other, serve as pivot stops. The engagement of the cantilever support (24) with the hub (10) is then substantially complete. The platform (42) then abuts and lies substantially level with the upper flange (18). In this way, the upper flange (18) can join multiple platforms (40) to define a common continuous level area surrounding the central axis (14). The central opening (56) of the tongue (50) receives and engages with the central protrusion (36) of the recess (30). The opening (56) of the tongue (50) may either pass over and engage with a fixed protrusion (36), or the protrusion (36), in the form of a movable or removable pin or lug, may be inserted into the opening (56) after the tongue (50) has been received in the recess (30). The tongue (50) and the recess (30) thus serve as locking configurations, with the protrusion (36) acting as a latch member or locking element that locks the cantilever support (24) to the hub (10), further restricting both lateral and longitudinal movement of the cantilever support (24). Turning now to Figure 4, this shows a hub (10) attached to, or incorporated in, a wind turbine tower (60). For example, the hub (10) may encircle the tower (60) and may be attached to the tower (60) by means of inwardly extending bolts or suspended from a flange that is welded or bolted to the tower (60). The hub (10) is equipped with a circumferential array of cantilever supports (24) spaced at angles in a petaloid arrangement. Once attached to the hub (10) as shown in Figure 4, the cantilever supports (24) are ready to be fitted with any equipment components they are designed to support. Electrolyzers (62) fitted to some of the cantilever supports (24) are shown herein. Furthermore, some of these electrolyzers (62) are used to support solar panel arrays (64), which can be tilted in any direction that is optimal for capturing the prevailing solar radiation. Figure 4 shows the cantilever supports (24) attached to the hub (10) before the cantilever supports (24) are fitted with equipment. However, it may instead be possible to lift the cantilever supports (24) to engage them with the hub (10) with at least some equipment already mounted on them. Figures 5a and 5b show an installation vessel (66) using its crane (68) to lift cantilever supports (24) from a barge (70) and engage them with a hub (10) in a secure position on the tower (60) of a wind turbine. Figure 5a shows the first of six cantilever supports (24) being engaged with the hub (10), and Figure 5b shows the last of these cantilever supports (24) about to be engaged with the hub (10). The installation vessel (66) and the barge (70) are repositioned relative to the wind turbine as necessary to allow access to the next unoccupied docking bay defined by one face (16) of the hub (10). To avoid the inconvenience of moving the installation vessel (66) during the installation of a series of cantilever supports (24), the hub (10) is rotated about the vertical axis (14) of the wind turbine tower (60), as shown in Figure 6. For example, the hub (10) could be moved on a circumferential horizontal rail surrounding the tower (60). The gradual angular movement of the hub (10) brings unoccupied docking bays into a fixed position and orientation that is easily accessible to the crane (68) of the installation vessel (66). The installation vessel (66) is shown herein about to engage the fifth of six cantilever supports (24) with the hub (10), the first four cantilever supports (24) having already been installed. In Figures 5a, 5b, and 6, the cantilever supports (24) could instead be raised from a deck of the installation vessel (66) itself, if such a deck is sufficiently large. Furthermore, the cantilever supports (24) can be installed on the hub (10) in any order, for example, in circumferential succession or in opposing pairs, one on one side of the tower (60) and the next on an opposite side of the tower (60) to maintain balance. The installation vessel (66) could float on the surface of the surrounding water or could be a self-elevating unit that remains above the seabed and has a hull raised free from the surface. Figure 6 also shows a split (72) illustrating how a hub (10), whether fixed or rotating, could be divided into two or more parts, each forming part of a complete loop. The hub (10) parts can be assembled together around the tower (60) or transition piece of a wind turbine, thus completing a continuous loop. This facilitates retrofitting the hub (10) to an existing wind turbine installation. Figures 7 and 8 show ways to drive the rotational movement of the hub (10) as contemplated in the arrangement of Figure 6. Specifically, Figure 7 shows an onboard drive arrangement, and Figure 8 shows an external drive arrangement for rotating the hub (10) around the tower (60) of a wind turbine. In the on-board drive arrangement of Figure 7, a drive unit (74) attached to the hub (10) drives wheels (76) or gears that engage the tower (60) to drive rotational movement of the hub (10). The arrangement could be reversed, with the drive unit (74) attached, instead, to the tower (60) and driving wheels or gears that engage the hub (10). In the external drive arrangement of Figure 8, the lines (76) extend from opposite attachment points (78) on the hub (10) to one or more winches on a surface vessel (not shown herein), such as the installation vessel (66). By applying tension to a suitable line (76), the winches drive rotational movement of the hub (10) in a desired direction around the tower (60). Figures 9, 10, and 11 show a petaloid array of cantilever supports (24) attached to a hub (10) located at the base of a wind turbine tower (60). In Figures 9 and 10, the wind turbine is supported by a semi-submersible buoy (80), while the wind turbine in Figure 11 is supported by a lattice structure (82) whose legs terminate in underwater foundations (84) such as suction piles to be embedded in seabed soil. Finally, Figure 12 shows variants in which bushings (10) are configured for attaching three, four, five, and eight cantilever supports (24) in triangular, square, pentagonal, and octagonal arrangements, respectively. Other petaloid variants are possible, such as a heptagonal arrangement involving seven cantilever supports (24). In general, for a given bushing size (10), the fewer the sides or faces (16), the greater the width of the cantilever supports (24) that can be attached to those faces (16). However, smaller, lighter, and more numerous cantilever supports (24) can be useful for operational flexibility and ease of installation. Cantilever supports do not have to be rectangular or parallel-sided in plan view. Instead, they could taper outwards, thus having outward-converging sides, or they could widen outwards, thus having outward-diverging sides. In the latter case, the sides of the cantilever supports could expand outwards to such an extent that angular gaps between adjacent supports are narrowed or even eliminated. In this way, the cantilever supports could define a circumferentially continuous support surface around the tower of a wind turbine. Although the described hubs have regular polygonal outlines with all sides of equal length and faces, therefore, all of equal width, it would in principle be possible for at least some of the sides to be of unequal length. In this way, the cantilever supports could be of different widths from one to the next around the circumference of the hub. It would also be possible for the cantilever supports to be of different lengths and, therefore, extend to different radial measurements relative to the central axis of a common hub. It is not essential that trunnions be in the cantilever supports and that complementary seats be in the mating bays. The arrangement could therefore be reversed, with trunnions in the mating bays engaging with inverted seats in the cantilever supports, or other interlocking arrangements could be provided.

Claims

1. An external equipment support system for a wind turbine, the system comprising: a hub (10) encircling or coextensive with a tower (60) or transition piece of the wind turbine and surrounding a central axis (14) of the tower or transition piece, the hub defining at least one coupling bay; and at least one support module releasably engaging with mounting configurations (26), (28), (30) of the respective coupling bay(s) and thereby cantilevered from the hub, characterized in that the hub is configured to rotate relative to the tower or transition piece about the central axis.

2. The system according to claim 1, wherein the hub comprises a plurality of coupling bays angularly spaced about the central axis and a plurality of support modules releasably engaging with the mounting configurations of the respective coupling bays. 3.The system according to claim 2, wherein the hub has a polygonal outline in plan view, each of the coupling bays corresponding to a respective side of the polygonal shape.

4. The system according to claim 2 or claim 3, wherein the support modules surround the hub in a petaloid arrangement.

5. The system according to any preceding claim, wherein the hub comprises a tubular wall surrounding the central axis.

6. The system according to any preceding claim, wherein the support module, or each support module, comprises a platform and the hub comprises a horizontal flange, the platform and the flange being substantially at the same horizontal level when the support module is cantilevered from the hub. 7.The system according to any preceding claim, wherein the mounting configurations of the docking bay(s) are spaced from, and symmetric about, a plane containing the central axis.

8. The system according to any preceding claim, wherein the docking bay(s) and support module(s) have complementary mounting configurations, such mounting configurations including seats for receiving respective trunnions.

9. The system according to claim 8, wherein the mounting configurations of the docking bay(s) comprise the seats and the mounting configurations of the support module(s) comprise the trunnions.

10. The system according to claim 8 or claim 9, further comprising elongated guides extending from the seats and open at their outer ends. 11.The system according to claim 10, wherein the guides extend upward and outward from the seats to the open outer ends.

12. The system according to any of claims 8 to 11, wherein the mounting configurations of the docking bay(s) further comprise at least one pivot stop positioned at a level below the seats or trunnions, the pivot stop(s) being opposite a pivot stop of a support module engaged with the hub. 13.The system according to any preceding claim, wherein the mounting configurations of the or each docking bay further comprise at least one locking configuration positioned at a level below the seats or trunnions, the or each locking configuration being capable of engaging with a complementary locking configuration of a support module engaged with the hub after pivoting of such support module about the trunnions engaged with the seats.

14. The system according to claim 13, wherein the locking configurations of the or each docking bay and support module overlap each other after such pivoting.

15. The system according to claim 13 or claim 14, further comprising at least one locking element acting between the locking configurations. 16.The system according to any preceding claim, wherein the support module, or each support module, is elongated radially outward from the central axis.

17. The system according to any preceding claim, wherein the hub is in parts which, when assembled together, form a continuous loop around the central axis.

18. The system according to any preceding claim, further comprising an onboard drive acting between the hub and the tower or transition piece to rotate the hub.

19. The system according to any of claims 1 to 17, further comprising an external drive acting on the hub to rotate the hub.

20. The system according to any preceding claim, wherein at least one support module supports electrolyzing equipment. 21.The system according to any preceding claim, wherein at least one support module supports a solar cell array.

22. A method for externally supporting equipment on a wind turbine, the method comprising: releasably engaging a first cantilever support module with a first hub coupling bay, the hub encircling or being coextensive with a tower or transition piece of the wind turbine and surrounding a central axis of the tower or transition piece, rotating the hub about the wind turbine, and releasably engaging a second cantilever support module with a second hub coupling bay.

23. The method according to claim 22, comprising releasably engaging a plurality of support modules with respective hub coupling bays that are angularly spaced about the central axis. 24.The method according to claim 22 or claim 23, comprising hanging the support module(s) over the hub's coupling bay(s) to engage the support module(s) with the hub.

25. The method according to claim 24, further comprising pivoting the support module(s) about the hanging engagement.

26. The method according to claim 25, comprising engaging locking configurations of the support module(s) and coupling bay by means of pivoting the support module(s) relative to the hub.

27. The method according to claim 26, comprising engaging a locking element between the locking configurations.

28. The method according to any one of claims 22 to 27, comprising installing equipment on the support module(s) after engaging the support module(s) with the hub. 29.The method according to any of claims 22 to 28, comprising installing equipment on the support module(s) before attaching the support module(s), which carries such equipment, to the hub.

30. The method according to any of claims 22 to 29, comprising keeping an installation vessel substantially stationary between the installation of successive support modules on the hub.

31. The method according to any of claims 22 to 30, comprising securing the hub relative to the wind turbine after installing the support modules on the hub.

32. The method according to any of claims 22 to 31, comprising, preliminarily, assembling the hub from two or more parts around the tower or transition piece of the wind turbine. 33.The method according to claim 32, wherein the hub is assembled in a reconditioning operation performed on a previously operational wind turbine.

Images