IMPROVEMENTS RELATING TO ENVIRONMENTAL PROTECTION COVERS FOR WIND TURBINE STRUCTURES

Abstract

A wind turbine structure comprises a surface defining at least in part an opening, and a closure system provided adjacent the opening. The closure system includes an inflatable closure that is inflatable into a deployed state in which the inflatable closure engages the surface so as to cover at least a portion of the opening.

Claims

1. A wind turbine structure comprising: a surface defining at least in part an opening; and a closure system provided adjacent the opening, the closure system including an inflatable closure that is inflatable into a deployed state in which the inflatable closure engages the surface so as to cover at least a portion of the opening.

2. The wind turbine structure of claim 1, wherein the inflatable closure defines an edge profile that is configured to match a complementary engaging profile defined by the surface of the opening.

3. The wind turbine structure of claim 1, wherein the inflatable closure defines a substantially planar body in the deployed state.

4. The wind turbine structure of claim 1, wherein the inflatable closure in the deployed state defines a plurality of ribs interconnected by webs.

5. The wind turbine structure of claim 1, wherein the closure system includes a housing which is configured to contain the inflatable enclosure in a stowed state.

6. The wind turbine structure (10) of claim 1, wherein the closure system comprises a rigid plate that covers at least a portion of the opening.

7. The wind turbine structure of claim 6, wherein the inflatable closure is housed at least partially within the rigid plate in the stowed state.

8. The wind turbine structure of claim 6, wherein the rigid plate is foldable.

9. The wind turbine structure of claim 1, wherein the closure system includes an inflation pump to inflate the inflatable closure.

10. The wind turbine structure of claim 1, wherein the inflation pump is operable to deflate the inflatable closure.

11. The wind turbine structure of claim 1, wherein the inflatable closure is mounted on an edge of the opening.

12. The wind turbine structure of claim 1, wherein the inflatable closure engages the surface to form a water-tight seal.

13. The wind turbine structure of claim 1, wherein the inflatable closure comprises multiple air-tight internal chambers that can be individually inflated and deflated.

14. The wind turbine structure of claim 1, wherein the closure system comprises multiple inflatable closures.

15. The wind turbine structure of claim 1, wherein the inflatable closure comprises a base layer of drop-stitch material.

16. A method of at least partially covering an opening of a wind turbine structure, the method comprising; providing a closure system including an inflatable closure adjacent the opening; and inflating the inflatable closure from a stowed state to a deployed state in which the inflatable closure covers at least a portion of the opening.

17. The method of claim 16, comprising engaging the inflatable closure with a surface that defines, at least in part, the opening.

18. The method of claim 17, wherein engaging the inflatable closure with the surface comprises engaging an edge profile of the inflatable closure with a complementary engaging profile defined by the surface of the opening.

19. The method of claim 16, comprising inflating the inflatable closure from a housing in which it is contained in the stowed state.

20. The method of claim 19, comprising inflating the inflatable closure from a housing that forms part of a rigid plate that covers at least a portion of the opening.

21. The method of claim 16, comprising deflating the inflatable closure so as to provide access to a portion of the opening.

22. The method of claim 16, comprising inflating and/or deflating multiple air-tight internal chambers of the inflatable closure individually.

23. The method of claim 22, comprising inflating and/or deflating at least one of the internal chambers before at least one other of the internal chambers.

24. The method of claim 16, comprising remotely activating inflation and/or deflation of the inflatable closure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will now be described by way of example with reference to the accompanying drawings, in which:

[0028] FIG. 1 is a wind turbine that may comprise a wind turbine structure in accordance with an embodiment of the invention;

[0029] FIG. 2 is a perspective view of wind turbine structure comprising a closure system in accordance with an embodiment of the invention;

[0030] FIG. 3 is a perspective view of the wind turbine structure of FIG. 2, showing an inflatable closure of the closure system in its housing;

[0031] FIG. 4 is a perspective view of the wind turbine structure of FIG. 2, showing the inflatable closure in a partially deployed state;

[0032] FIG. 5 is a perspective view of the wind turbine structure of FIG. 2, showing the inflatable closure in a fully deployed state;

[0033] FIG. 6 is a cross-sectional view of the wind turbine structure of FIG. 5, showing engagement of the inflatable closure with a flange of the wind turbine structure;

[0034] FIG. 7a is a cross-sectional view of a closure system in accordance with another embodiment of the invention;

[0035] FIG. 7b is a cross-sectional view of a closure system in accordance with another embodiment of the invention;

[0036] FIG. 8a is a cross-sectional view of a closure system having multiple inflatable closures in accordance with another embodiment of the invention;

[0037] FIG. 8b is a perspective view of the closure system of FIG. 8a;

[0038] FIG. 9a is a perspective view of another wind turbine structure in accordance with an embodiment of the invention, showing an inflatable closure in a stowed state;

[0039] FIG. 9b is a perspective view of the wind turbine structure of FIG. 9a, showing the inflatable closure in a partially deployed state;

[0040] FIG. 9c is a perspective view of the wind turbine structure of FIG. 9a, showing the inflatable closure in a fully deployed state;

[0041] FIG. 10 is a plan view of another wind turbine structure in accordance with the invention, in which the closure system includes a rigid frame;

[0042] FIG. 11 is a perspective view of a portion of the wind turbine structure of FIG. 10, showing an inflatable closure housed within the rigid frame in a stowed state; and

[0043] FIG. 12 is a perspective view showing a closure system in accordance with another embodiment of the invention being deployed from a stowed state to a deployed state.

DETAILED DESCRIPTION

[0044] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the invention. Other embodiments may be utilised, and structural changes may be made without departing from the scope of the invention as defined in the appended claims.

[0045] FIG. 1 shows a wind turbine 8 that may comprise a wind turbine structure 10 in accordance with an embodiment of the invention. The wind turbine 8 includes a nacelle 12 that is supported on a generally vertical tower 14, which is itself mounted to a foundation (not shown). The tower 14 is formed of a number of tower segments 15, which are attached end-to-end. The nacelle 12 houses a number of functional components, including a gearbox and a generator (not shown), and supports a main rotor arrangement 16. The main rotor arrangement 16 comprises a plurality of wind turbine blades 18, and in this example comprises three wind turbine blades 18.

[0046] Examples of wind turbine structures 10 are towers or tower sections, foundations, transition pieces, blades, hubs, nacelles, and wind turbine structure support which may, for example, be provided at a preassembly site or on a vessel. FIGS. 2 to 5 illustrate a wind turbine structure 10 in accordance with an embodiment of the invention, exemplified in a non-limiting manner by a tower section 15 having an opening 22 at its top or upper end 24.

[0047] The wind turbine structure 10 comprises a closure system 20 that is configured to at least partially cover an opening 22 of the wind turbine structure 10 when deployed, so as to protect the interior of the wind turbine structure 10 from the external environment.

[0048] In this embodiment, the opening 22 of the wind turbine structure 10 to be covered is defined at an upper end 24 of a tower segment 15 of the wind turbine 8, to which another tower segment 15, or the nacelle 12, may be attached when the turbine 8 is assembled.

[0049] FIG. 2 shows a typical situation where the interior of a tower segment 15 is left open during the installation process, ready for another tower segment to be secured on top of it. As can be seen, the tower segment 15 is generally cylindrical and further comprises a lower end (not shown), and an outer surface 26.

[0050] The upper end 24 of the tower segment 15 comprises a circumferential flange 28 to which a further tower segment 15, or the nacelle 12, is bolted when the wind turbine 8 is assembled. The circumferential flange 28 extends radially inwardly from the outer surface 26 of the tower segment 15 to an inner surface 30 of the flange 28, and comprises a plurality of fastener-receiving openings or ‘bolt holes’ 32. The inner surface 30 of the flange 28 defines the opening 22 of the tower segment 15 to be covered. The opening 22 leads to an internal volume or chamber 34 of the tower segment 15, which defines a generally cylindrical volume within the tower segment 15.

[0051] The closure system 20 is located within the internal chamber 34 of the wind turbine structure 10, and is positioned adjacent the opening 22. As can be seen in FIG. 2, the closure system 20 is preferably located in a generally central position in the internal chamber 34 and slightly set back, along the tower axis, from the tower flange 28. It is in this sense that the closure system 20 is considered to be adjacent to the opening 22, as from this position the closure system 20 can be activated so that components thereof are deployed so as to cover the opening 22, as will be apparent from the discussion that follows.

[0052] The closure system 20 comprises an inflatable closure 36 that can be deployed from a stowed state illustrated in FIG. 2, to a deployed, or inflated, state illustrated in FIG. 5. In this embodiment the inflatable closure 36 defines a substantially planar body that fully covers the opening 22 of the wind turbine segment 15 in the deployed state. In other embodiments, the closure 36 may be different shapes and sizes, and may only partially cover the opening 22 when deployed.

[0053] Referring to FIGS. 2 to 4 in particular, the closure system 20 of this embodiment comprises a housing 38 that contains the inflatable closure 36 in the stowed state. The housing 38 includes a body 40 and a lid 42, and in this example has a generally rectangular cross-section, so as to be shaped generally like a box. The body 40 defines an internal volume 44 in which the inflatable closure 36 is housed when stowed, and an opening 46 from which the inflatable closure 36 inflates into its deployed state. The lid 42 is a removable cover that closes the opening 46 of the body 40. Note that the specific example of the housing 38 is given here as an illustration of one configuration of shape and size, but it will be appreciated that the invention should not be considered to be limited to the specifics of the housing 38 as shown here.

[0054] As best illustrated in FIG. 5, the inflatable closure 36 has a generally circular shape in plan view in this example, and is dimensioned so as to fully cover the circular opening 22 at the upper end 24 of the tower segment 15 when deployed.

[0055] The inflatable closure 36 comprises upper and lower surfaces, 48 and 50 respectively, that are generally circular in shape, and a circumferential surface 52 that joins the upper and lower surfaces, 48 and 50 respectively, at their edges. The upper surface 48 faces away from the internal chamber 34 when the inflatable closure 36 is deployed, and the lower surface 50 faces towards the internal chamber 34 when deployed.

[0056] The inflatable closure 36 of this embodiment is formed by a base layer (not shown) and an outer layer 54.

[0057] The base layer preferably comprises a layer of drop-stitch material/fabric, which is a known technology, for example at www.duletai.com. The drop-stitch material will not be described in detail here but, briefly, is formed by two support layers of polyester woven fabric joined by polyester threads that extend between them.

[0058] The outer layer 54 comprises an air tight coating that surrounds and encloses the base layer, and that defines an internal volume or chamber (not shown) that is filled with air when the closure is inflated. In this embodiment, the outer layer 54 includes two elongate ridges or ribs 56 that extend across the upper surface 48 of the closure 36, to enhance its structural rigidity in the deployed state.

[0059] The inflatable closure 36 further comprises a valve (not shown) through which the closure is inflated and deflated in use. To inflate and deflate the closure 36, an inflation pump (not shown) is attached to the valve, and the internal volume is filled with or emptied of air using the pump. In other embodiments, the closure 36 may be inflated using an inflator unit that forms a part of the closure system 20. The inflator unit may be integrated within the internal volume of the inflatable closure 36. Examples of suitable inflator units could be electrical blowers, which may be battery powered, canisters of compressed gas e.g. air, or inflators that are based on chemical reactions to generate gas to inflate the closure 36, or on physical reactions (i.e. evaporation or sublimation) to generate gas to inflate the closure 36. If the closure system 20 comprises a housing 38, then it is preferred that the inflator unit is integral with the housing or is integrated in the inflatable closure 36.

[0060] The valve may be provided at any position on the inflatable closure 36. In some embodiments, the valve is provided so as to be accessible to a user without removing the inflatable closure 36 from the housing 38. In this way, the inflation pump can be attached to the valve without first removing the inflatable closure 36 from the housing 38. In other embodiments, the valve may be positioned such that the inflatable closure 36 must be removed from the housing 38 before the inflation pump can be attached. In some embodiments, in particular those in which the closure 36 fully covers the opening 22 in the deployed state, the valve is preferably positioned on the upper surface 48 of the closure 36, so as to be accessible even when the closure 36 is fully deployed and secured in place. In some embodiments, in particular those in which the inflatable closure 36 forms a roof over the internal chamber 34 of the structure 10 when deployed, the valve is preferably positioned to face the internal chamber 34. In some embodiments, in particular those where the upper and lower surfaces 48, 50 of the inflatable closure 36 are both accessible after deployment, multiple valves may be arranged on the inflatable closure 36. In particular, at least one valve may be provided on the upper surface 48 of the closure 36 and at least one valve may be provided on the lower surface 50 of the closure 36.

[0061] In one embodiment, the valve and/or the inflator unit is remotely operable. This is particularly advantageous where the closure 36 covers an opening 22 that may be used for access of tools to handle, for example to lift, the wind turbine structure 10. The ability to remotely operate the valve and/or the inflator unit removes the need for personnel to travel to the structure 10 to inflate and/or deflate the closure 36, thus saving considerable time and resources. Furthermore, the ability to remotely operate the valve and/or the inflator unit may improve site safety. For example, in a scenario in which a tower section 15 is being lifted on site, it is preferable that personnel are not in the vicinity, because it is unsafe for personnel to be working near or under suspended loads. Remote operation of the valve and/or inflator unit allows an operator to inflate and/or deflate the closure 36 without having to enter the site. In this case, it is preferred that one or more sensors are arranged in the vicinity of the structure 10 so as to provide confirmation that the closure 36 has been properly inflated/deflated/positioned before engagement of, for example, a tool for lifting the structure 10. The one or more sensors may be any suitable sensors, including but not limited to cameras for capturing images and/or video footage, and/or contact/proximity sensors.

[0062] Turning now to FIG. 6, this shows how the inflatable closure 36 of the first embodiment of the invention may engage with and be secured to the flange 28 of the tower segment 15 in the deployed state. As is shown clearly in the illustrated embodiment, the edge of the inflatable enclosure 36 features suitable means to secure, fix or otherwise fasten a portion of the inflatable enclosure 36 to the wind turbine structure.

[0063] The circumferential surface 52 of the inflatable closure 36 defines an edge profile 58 that includes a flange-receiving aperture 60 defined between upper and lower edge portions, 62 and 64 respectively, of the inflatable closure 36, and configured to receive the flange 28 of the tower segment 15 when deployed. In this way, the flange 28 defines an engaging profile 66 that is complementary to the edge profile 58 of the inflatable closure 36. In this embodiment, the flange receiving aperture 60 forms a circumferential groove that extends around the edge of the inflatable closure 36 and that corresponds to the flange 28 that forms a circumferential edge that extends around the upper end 24 of the tower segment 15.

[0064] The upper and lower edge portions, 62 and 64 respectively, each include a plurality of fastener-receiving openings 68. Openings 70 of the lower edge portion 64 define generally circular through-holes that extend from the lower surface 50 of the closure 36, to an upper surface 72 of the lower edge portion 64 that faces the flange 28 when the closure 36 is deployed. Openings 74 of the upper edge portion 62 define generally circular holes in a lower surface 76 of the upper edge portion 62 that faces the flange 28 when the inflatable closure 36 is deployed. Each opening 68 comprises a threaded metal coating or insert 78 on its interior surface 80 for engagement with a bolt 82. It should be appreciated that the use of such fastener receiving openings and corresponding bolts is not required, but is an additional safety feature that may ensure maintained connection between the closure 36 and the structure 10, even in the unlikely event that the closure 36 should lose pressure or be torn from the opening 22 by weather, for example.

[0065] When the closure 36 is inflated and properly positioned for use, the flange 28 of the tower segment 15 is received in the flange-receiving aperture 60 of the closure 36, and the fastener-receiving openings 68 of the upper and lower edge portions 62, 64 align with the fastener-receiving openings 32 of the flange 28. Thus, complementary profiles of the closure 36 and the flange 28 are engaged, and the inflatable closure 36 is mounted on an edge 84 of the opening 22.

[0066] In this embodiment, the upper edge portion 62 terminates so as to be flush with the outer surface 26 of the tower segment 15. To secure the inflatable closure 36 to the tower segment 15, fasteners such as bolts 82 or screws extend through one or more of the aligned sets of fastener-receiving openings 68, 32 of the upper and lower edge portions 62, 64 of the closure 36 and the flange 28.

[0067] The inflatable closure 36 may be deployed during transport of the tower segment 15 to an installation site at which the wind turbine 8 is to be assembled, and up until installation, so as to protect the tower segment 15, and in particular the internal chamber 34 of the tower segment 15, from the external environment. For example, the closure 36 may protect the internal chamber 34 from ingress of water, snow, ice and/or other contaminants. Thus, although FIG. 6 shows gaps to exist between the inflated closure 36 and the flange 28, it is preferred that the closure 36 engages the flange 28 in a tight-fit, to form a sealed, and preferably water-tight, connection with the flange 28. For this, a rubber or silicone member (not shown) may be provided between the closure 36 and the flange 28, and the inflated closure 36 may push against the flange 28 and member to form a seal for preventing water or gas ingress. This may be particularly important in offshore environments to prevent salt sprays or salt containing aerosols, which may be very corrosive, from entering the structure 10.

[0068] When the wind turbine 8 is ready to be installed, the inflatable closure 36 can simply be deflated via a release valve or using the inflation pump to release air from its interior, and removed from the tower segment 15 along with the housing 38 in which it can be re-packed ready for future use. It is envisaged that suitable fold lines can be introduced to the inflatable enclosure during manufacturing to ensure that the inflatable enclosure can re-configured itself into a stowed state inside the housing 38 when air is pumped out.

[0069] FIGS. 7a and 7b show variations of the inflatable closure 36 of the first embodiment of the invention, in which the circumferential surface 52 has a different profile for engaging with the flange of the tower segment.

[0070] In FIG. 7a, the upper edge portion 62 extends radially outwardly past the outer surface 26 of the tower segment 15, and downwardly along the outer surface 26 to form a circumferential lip 86. In this way, the wind turbine structure 10 is engaged to prevent relative movement between the flange 28 and the closure 36. In particular, movement of the closure 36 in an upwards direction, a downwards direction, and left and right directions with respect to the view shown in FIG. 7a is prevented. The closure 36 is therefore locked to, i.e. retained in place with respect to, the flange 28. In this variant, the circumferential lip 86 and the lower edge portion 64 act to secure the inflatable closure 36 in place without the use of fasteners, but in other embodiments the closure 36 may also include fastener-receiving openings 68 as in the embodiment of FIG. 6.

[0071] FIG. 7b shows a variant of the inflatable closure 36 that preferably engages the flange 28 from one side only. Here, the upper edge portion 62 of the closure 36 terminates at the outer surface 26 of the tower segment 15. The lower edge portion 64 (present in the embodiments of FIG. 6 and FIG. 7a) is not present. The inflatable closure 36 of this example may simply be supported from underneath by an upper surface 88 of the flange 28, or may include fastener-receiving openings 68 in the upper edge portion 62.

[0072] Turning now to FIG. 8, this shows a wind turbine structure 10 in accordance with another embodiment of the invention.

[0073] In this embodiment, the closure system 20 comprises three inflatable closures 36 which together cover the opening 22 of the tower segment 15 when deployed. As illustrated, the different inflatable enclosures 36 engage with one another when in the inflated state so as to span the gap across the opening 22. Usefully, the different enclosures can contribute different functionality to the overall coverage of the opening 22. For example and as will be described further below, the middle enclosure 90 is formed into generally an I-beam shape so as to provide increased strength and rigidity to the overall closure structure. This may be useful where high loads are expected to be supported by the closure 36, for example after heavy snow fall.

[0074] Specifically, the closure system 20 comprises a central closure 90 and two outer closures 92. Each inflatable closure 36 is formed from a base layer and an air-tight outer layer 54, and includes a valve (not shown) for inflation and deflation, as in previous embodiments. In other embodiments one or more of the closures 36 may comprise an airtight inner layer and a protective or structural outer layer.

[0075] The central inflatable closure 90 preferably comprises a flat rectangular lower surface 94 and a curved upper surface 96 that generally defines a segment of a cylinder, as is best seen in FIG. 8a. The upper and lower surfaces 96, 94 are joined by first and second side faces, 98 and 100 respectively, and first and second end faces, 102 and 104 respectively. Each end face 102, 104 is curved so as to match the curvature of the outer surface 26 of the tower segment 15, and defines a flange-receiving opening (not shown) for receiving the flange 28 in the deployed state. Each side face 98, 100 defines a closure-receiving opening 108 for receiving an edge 110 of a corresponding outer closure 92 in the deployed state. The inflatable closure 36 may be configured so that selected part(s) of the closure 36 inflate sequentially, before or after other part(s) of the closure 36.

[0076] This may be illustrated using the embodiment shown in FIG. 8b. Here, as an example, a first edge part incorporating an end face 102 or 104 of the central closure 90 may inflate first to secure the central closure 90 on the structure 10, and prevent it from falling off the wind turbine structure 10 during further deployment. Thereafter, a main part of the central closure 90, adjacent the first edge part, may be inflated to spread out the inflatable closure. Finally, a second edge part, adjacent the main part and opposed to the first edge part, and incorporating an end face 102 or 104 of the central closure 90, is inflated to finally secure the whole inflatable closure 90 to the wind turbine structure 10. The order of inflation/deflation may, for example, be realised by the positioning of one or more valves of the closure 90 and/or through sectioning the inflatable closure 90 to produce multiple internal chambers having no, or only small, apertures between them. In the case in which separate internal chambers are present, separate means for inflation of each of these sections/chambers may be provided.

[0077] It should be understood that the inflatable closure 36 may take another shape than generally flat. For example, the inflatable closure 36 may take the shape of a dome or pyramid having, for example, 3, 4, 6, 8 or more faces. A non-flat shape has been found to be particularly advantageous for closures 36 acting as a generally horizontal cover of a wind turbine structure 10, as this tends to aid in the removal of rain, snow, dust or other debris from the closure 36, and hence prevents or reduces the risk of build-up of large weights of debris that potentially may damage the closure 36. Non-flat structures may, for example, be realised through the use of ribs, which may or may not be inflatable, and which are integrated with the inflatable closure 36. Alternatively or additionally, non-flat structures may be realised through the use of separate support elements arranged vertically under the closure 36 to support the closure 36.

[0078] The outer inflatable closures 92 are identical to each other, and each comprises an upper surface 112 and a lower surface 114. The upper and lower surfaces 112, 114 are joined by an outer side surface 116 that engages with the flange 28 of the tower segment 15 when deployed, and an inner side surface 118 that engages with the central closure 90 when deployed. The outer side surface 116 may for example have an identical profile to the circumferential surface 52 of the embodiment of FIG. 7a, or similar functionality, and thus will not be described again for conciseness. The inner side surface 118 defines a protrusion 120 that is dimensioned to be receivable in the closure-receiving opening 108 of the central inflatable closure 90, and that in this example has a rectangular cross-section.

[0079] When deployed, the protrusions 120 of the outer closures 92 are received in the closure-receiving openings 108 of the central closure 90, and the flange 28 of the tower segment 15 is received in the flange-receiving openings 60 of the central and outer closures 90, 92. The central closure 90 extends across the diameter of the opening 22, and covers a central portion 122 of the opening 22. The outer closures 92 are positioned on either side of the central inflatable closure 90, and cover the rest of the opening 22.

[0080] In this way, the inflatable closures 90, 92 together form a covering that fully covers the opening 22 of the tower segment 15 when deployed. In other embodiments, one or more of the inflatable closures 90, 92 may be omitted, or the dimensions of the closures 90, 92 may differ, such that the inflated closures 90, 92 only partially cover the opening 22 of the tower segment 15 when deployed. This also allows deflation of part of the full closure system 20 to allow access to the inside of the wind turbine structure 10 without complete removal of the closure system 20. For example, to enable access to personnel, or for equipment or tools for lifting the wind turbine structure 10.

[0081] FIG. 9 illustrates a wind turbine structure 10 according to another embodiment of the invention.

[0082] FIG. 9a shows the inflatable closure 36 in an uninflated state, adjacent the opening 22 of a wind turbine structure 10 in which it is to be deployed. In this case, the opening 22 is defined by a frame 124 the forms part of a bigger wind turbine structure.

[0083] The frame 124 is generally square-shaped, and comprises a base 126 and first and second flanges 128, 130. Other shapes of the frame 124 such as circular or polyhedral are similarly feasible when the shape of the inflatable closure 36 is shaped accordingly. The first and second flanges 128, 130 extend inwardly towards the centre of the frame 124, from first and second edges 132, 134 of the base 126, and are generally perpendicular to the base 126. In this way, the frame 124 has a U-shaped profile in cross-section, and defines a rectangular aperture 136 in which edges 138 of the inflatable closure 36 are received in the deployed state.

[0084] The inflatable closure 36 of this embodiment is generally square when inflated, as shown in FIG. 9c, so as to fully cover the square opening 22 defined by the frame 124 in which it is deployed. Similarly to the closure 36 of the first embodiment, the inflatable closure 36 of this embodiment is formed by a base layer and an air-tight outer layer 54 that defines an internal volume. A valve 140 is provided on an upper surface 142 of the closure 36 for inflation and deflation using an inflation pump.

[0085] To deploy the inflatable closure 36, an inflation pump is connected to the valve 140, and air is pumped into the closure 36. The closure 36 inflates from an uninflated state shown in FIG. 9a, through a partially deployed state shown in FIG. 9b, to a fully deployed state shown in FIG. 9c. In the deployed state, edges 138 of the inflatable closure 36 are received in the rectangular aperture 136 of the frame 124, and abut against internal surfaces 144 of the frame that define the aperture 136. In this way, the inflatable closure 36 is secured in place with respect to the frame 124 by means of friction between the internal surfaces 144 and the closure 36.

[0086] FIGS. 10 and 11 show a wind turbine structure 10 in accordance with a further embodiment of the invention, in which the closure system 20 includes a plate 146 that covers a part of the opening 22 to be protected, closed off or sealed. As in the embodiments of FIGS. 2 to 8, the opening 22 of this embodiment is formed in the upper end 24 of a tower segment 15.

[0087] The plate 146 is rigid and has first and second ends, 148 and 150 respectively, joined by first and second sides, 152 and 154 respectively. The plate 146 comprises an upper generally planar surface 156 and a lower generally planar surface (not shown), which are joined by a peripheral surface 160. The upper surface 156 includes a plurality of ridges or ribs 162 that extend across the plate 146, from the first end 148 to the second end 150, and that are connected by webs 164. The ribs 162 act to enhance the structural rigidity of the plate 146. The plate 146 of this embodiment further includes four hinges 166 at which the plate 146 can fold. The hinges 166 allow the width of the plate 146 to be reduced, which may be advantageous, for example, during transport of the closure system 20, and when not in use.

[0088] The plate 146 is dimensioned in this example to cover a central portion 168 of the opening 22, and to define first and second openings, 170 and 172 respectively, between the plate 146 and the flange 28 of the tower segment 15, when installed on the tower segment 15. In this way, the internal chamber 36 of the tower segment 15 can still be accessed via the first and second openings, 170, 172, even when the plate 146 is installed on the tower segment 15, and the closure system 20 is ready to be fully deployed.

[0089] When installed at the tower segment 15, the plate 146 extends across the diameter of the opening 22. As best seen in FIG. 10, the first and second ends 148, 150 of the plate 146 are curved to follow the curvature of the outer surface 26 of the tower segment 15, and the first and second sides, 152, 154, of the plate 146 each define a generally U-shaped profile in plan view.

[0090] Referring now to FIG. 11, an inflatable closure 36 is attached at the first side 152 of the plate 146, towards the first end 148 of the plate 146. The inflatable closure 36 of this embodiment is similar to the inflatable closures 36 of the other embodiments, having a base layer, an air-tight outer layer 54, and a valve (not shown) for inflation and deflation. The inflatable closure 36 is dimensioned so as to fully cover the first opening 170 when deployed. Thus, the inflatable closure 36 has generally U-shaped upper and lower surfaces (not shown), to match the size and shape of the first opening 170. It should be understood that in other embodiments the deployed closure 36 may be dimensioned to only partially cover the first opening 170.

[0091] When in the stowed state, the inflatable closure 36 is stored at least partially within the plate 146, in a housing cavity (not shown) defined between the upper surface 156 and the lower surface (not shown) of the plate 146. In other embodiments, the inflatable closure 36 may be contained within a separate housing attached to the plate 146.

[0092] To deploy the inflatable closure 36, the closure 36 is partially removed from the housing cavity and the valve is located. An inflation pump is attached to the valve, and the closure 36 is inflated. When deployed, the inflatable closure 36 covers the first opening 170, and is supported from below by the flange 28 of the tower segment 15. An edge region (not shown) of the closure 36 that engages with the plate 146 when inflated is received in an aperture (not shown) that extends across the first side 152 of the plate 146, and in the housing cavity, and engages with the plate 146 in a similar manner to that shown in FIG. 9.

[0093] Although the closure system 36 of this embodiment includes only a single inflatable closure 36, other embodiments may include additional inflatable closures 36, attached at different positions of the plate 146. For example, a second inflatable closure may be attached at a corresponding position at the second side 154 of the plate 146, so as to cover the second opening 172 when deployed. In another variant, multiple inflatable closures 36 may be installed at one side of the plate 146, and be configured to together fully or partially cover the corresponding opening when deployed.

[0094] Many variations and modifications to the above-described arrangements are possible within the scope of the invention.

[0095] For example, the wind turbine structure 10 may include additional supports 176, as shown in FIG. 12, configured to help support the or each inflatable closure 36 in the deployed state. Such supports 176 may be especially useful when the opening 22 to be covered is large, and may help to prevent the deployed closure 36 from sagging.

[0096] Although the embodiments described in the preceding paragraph each include a base layer and an outer layer 54, in other embodiments the closure 36 may only include an air-tight outer layer 54, and not include a base layer. Alternatively, the closure 36 may include an airtight inner layer and a protective or structural outer layer.

[0097] Closures 36 of the invention are also not limited to including only one valve and one internal chamber 34. Closures 36 of other embodiments of the invention may include multiple valves associated with one internal volume. Closures 36 of other embodiments may further define multiple air-tight chambers, which can be inflated and deflated separately, and preferably sequentially, by means of one or more associated valves.

[0098] It is to be understood that many different methods may be used to secure a closure 36 of the invention to a wind turbine structure 10. For example, the closure 36 may be secured in place simply by means of friction between the closure 36 and a surface of the wind turbine structure 10, or may be secured via friction and fastening means. Fastening means may include bolts, screws, and wires, that may extend through fastener-receiving openings of the closure and the wind turbine structure 10. Furthermore, the use of magnets may be employed, especially in embodiments in which the wind turbine structure 10 does not include fastener receiving openings in the vicinity of the closure system 20. In this case, a magnetic element may be attached to the wind turbine structure 10, and a wire may extend from the magnet to a connection point of the closure 36, thereby securing the closure 36 to the structure 10. Alternatively, the magnet may be directly integrated into the inflatable closure 36 and/or attached to the surface of the closure 36.

[0099] Many different shapes and sizes of the closure 36 are possible within the scope of the invention, as well as many different profiles of the closure 36 for engaging with the wind turbine structure 10. For example, the edge profiles 58 of the closures 36 shown in FIGS. 6, 7 and 9 are not intended to be limiting, and it will be understood that many different profiles 58 are possible. In particular, the edge profile 58 of the closure 36 will depend on the surface that the closure 36 is intended to engage, and if the engagement is in one, two, three, four, five or six directions to the connection region of the wind turbine structure 10.

[0100] Finally, it will be understood that although the invention has been described in the context of a tower segment 15, a closure system 20 of the invention could be incorporated at any location at which an opening 22 is to be covered. In other embodiments, the closure system 20 may protect other portions of the wind turbine 8. For example, the closure system 20 could protect blade-receiving apertures of the hub, before the blades 28 have been attached, or could protect hatches or doorways of the wind turbine 8 as well as foundations, transition pieces, blades, nacelles, and wind turbine stands at a preassembly site or a vessel.

REFERENCE NUMBERS

[0101] wind turbine 8 [0102] wind turbine structure 10 [0103] nacelle 12 [0104] tower 14 [0105] tower segment 15 [0106] main rotor arrangement 16 [0107] wind turbine blade 18 [0108] closure system 20 [0109] wind turbine structure opening 22 [0110] upper end of tower segment 24 [0111] outer surface 26 [0112] flange 28 [0113] inner surface of flange 30 [0114] fastener-receiving openings 32 [0115] internal chamber 34 [0116] inflatable closure 36 [0117] housing 38 [0118] body 40 [0119] lid 42 [0120] internal volume of body 44 [0121] opening of body 46 [0122] upper surface of inflatable closure 48 [0123] lower surface of inflatable closure 50 [0124] circumferential surface of inflatable closure 52 [0125] outer layer of inflatable closure 54 [0126] ribs of inflatable closure 56 [0127] edge profile 58 [0128] flange-receiving aperture 60 [0129] upper edge portion of inflatable closure 62 [0130] lower edge portion of inflatable closure 64 [0131] engaging profile of flange 66 [0132] fastener-receiving openings of inflatable closure 68 [0133] openings of lower edge portion 70 [0134] upper surface of lower edge portion 72 [0135] openings of upper edge portion 74 [0136] lower surface of upper edge portion 76 [0137] threaded metal coating 78 [0138] interior surface 80 [0139] bolt 82 [0140] edge of opening 84 [0141] circumferential lip 86 [0142] upper surface of circumferential flange 88 [0143] central closure 90 [0144] outer closure 92 [0145] lower surface of outer closure 94 [0146] upper surface of outer closure 96 [0147] first side face 98 [0148] second side face 100 [0149] first end face 102 [0150] second end face 104 [0151] closure-receiving opening of side faces 108 [0152] edge of outer closure 110 [0153] upper surface of outer closure 112 [0154] lower surface of outer closure 114 [0155] outer side surface of outer closure 116 [0156] inner side surface of outer closure 118 [0157] protrusion of outer closure 120 [0158] central portion of opening 122 [0159] frame 124 [0160] base of frame 126 [0161] first flange of frame 128 [0162] second flange of frame 130 [0163] first edge of base 132 [0164] second edge of base 134 [0165] rectangular aperture of frame 136 [0166] edges of inflatable closure 138 [0167] valve 140 [0168] upper surface of inflatable closure 142 [0169] internal surfaces of frame 144 [0170] plate 146 [0171] first end of plate 148 [0172] second end of plate 150 [0173] first side of plate 152 [0174] second side of plate 154 [0175] upper surface of plate 156 [0176] peripheral surface of plate 160 [0177] ribs of plate 162 [0178] webs of plate 164 [0179] hinges of plate 166 [0180] central portion of opening 168 [0181] first opening 170 [0182] second opening 172 [0183] support 176