Structures and methods for installing, constructing, replacing parts, or maintaining wind turbines

Abstract

The present invention relates to a structure for use in installing or replacing components, maintaining, and / or constructing a wind turbine, the structure comprising a vertical structure at least partially supported on a wind turbine tower, a guide track connected to the vertical structure, and a bogie configured to follow the guide track along the vertical structure.

Description

Detailed Description of the Invention

[0001] The present invention particularly relates to structures and related methods for use in wind turbine installation, construction, part replacement or handling, or maintenance processes.

[0002] Modern wind turbines typically include a tower, the upper end of which supports a number of blades connected to a rotating hub. The blades are connected to a generator at the top of the tower via a shaft and bearing arrangement. In use, the wind rotates the blades, which in turn rotates the shaft, generating electricity via the generator. In addition to the generator, auxiliary equipment such as a transformer and a control and monitoring system are typically included. A top structure, called a nacelle, is typically supported on the tower via bearings, allowing the nacelle to rotate about the tower's vertical axis and adjust to changes in wind direction. The blades are connected to the nacelle.

[0003] Wind turbines have evolved from small, land-based turbines well under 1 MW to today's large turbines of around 10 MW. Despite the differences in size, wind turbine configurations have largely maintained the same general design over the years. Current developments include floating wind turbines capable of generating up to 15-20 MW of installed power. Blades used can be over 100 meters long.

[0004] In today's wind turbines, blades are typically installed after the nacelle is attached to the top of the tower structure. The blades are hoisted by a crane either external to the turbine tower or supported by the turbine tower. During installation, the blades are typically lifted by the crane using a lifting yoke, which grips and holds the blade in a horizontal position while it is attached to the nacelle. Using a crane supported by the turbine tower can be advantageous, particularly for offshore wind turbine installations, because it minimizes relative motion between the wind tower and the crane. When installing the blade from a horizontal position, a crane head extends from the wind turbine tower to hold the blade in place. This causes the center of mass of the crane with the blade lifted to be offset from the center of mass of the turbine tower. Therefore, calm weather is generally required for installation, as both wind and waves can create stresses on the crane and the wind turbine tower, especially if the blade is lifted high away from the center of the turbine.

[0005] It is known to mount the blades in a substantially vertical position, holding them directly below the nacelle, and wires attached to the lower ends of the blades are commonly used to hold the blades away from the turbine tower and prevent them from being struck by wind and / or waves against the crane tower.

[0006] From time to time, there may be a need to install or remove wind turbine components, such as generators or related components, housed in a nacelle, and there may also be a need to efficiently and more conveniently raise and lower such components from the nacelle at the top of the wind turbine tower, while making such operations safer and / or less susceptible to weather or sea conditions.

[0007] The time interval for acceptable offshore wave conditions is often very short. Furthermore, installing offshore wind turbines can be technically challenging and expensive. Therefore, there is a need for easier and more robust installation methods specifically suited for offshore use. At least one object of the present invention is to improve or mitigate one or more disadvantages associated with the prior art.

[0008] According to a first aspect, the present invention relates to a structure for use in the installation, construction, part replacement or handling, or maintenance processes of a wind turbine, the structure comprising a vertical structure at least partially supported on a wind turbine tower, a guide track connected to the vertical structure, and a bogie configured to follow the guide track along the vertical structure.

[0009] The structure facilitates lifting and lowering the wind turbine blade or nacelle in close proximity to the wind turbine tower. By having the carriage follow a guide track, the structure prevents relative movement of the wind turbine blade or nacelle during installation. The structure also ensures that the center of mass of the wind turbine blade or nacelle remains close to the wind turbine tower during lifting and installation. An advantage of the structure is that it extends the time interval for installation by allowing the installation of the wind turbine blade or nacelle in more severe weather conditions.

[0010] The guide track may be configured to prevent lateral rotation of the carriage. The guide track may comprise two laterally spaced track members to prevent lateral rotation of the carriage. Preventing lateral rotation of the carriage is advantageous in that it enhances control of the wind turbine blade during lifting and installation.

[0011] The wind turbine may be a land-based wind turbine or an offshore wind turbine, which may be a bottom-fixed wind turbine or a floating wind turbine.

[0012] The vertical structure may be fully supported by the wind turbine tower. The vertical structure may surround at least a portion of the wind turbine tower. The structure may include a lifting means for raising and lowering the carriage along the vertical structure. The lifting means may generally include at least one winch and at least one wire. The wire may be suspended from the top of the vertical structure. The wire may be threaded over a steel cart or other support member at the top of the vertical structure. One end of the wire may be fixed to the carriage, for example, with the wire unwound from the winch drum. The winch may be provided in any convenient location, for example, at or near the top or bottom of the vertical structure. The winch may be attached to the vertical structure. Alternatively, a drum may be located, for example, on the carriage, with the unwound end of the wire fixedly connected to the bottom of the vertical structure. The winch may be operated to reel in the wire, allowing the carriage to be lifted upward along the vertical structure.

[0013] The dolly may be used to facilitate installation of wind turbine components, such as a nacelle or a blade. In some examples, the wind turbine component, e.g., a blade or a nacelle, may be supported from above by at least one wire from at least one crane. The dolly may be positioned to laterally support the wind turbine component, e.g., a blade or a nacelle, being lifted by the crane wire. When a crane is used to lift the wind turbine component, e.g., to position it for installation, the dolly may be manipulated using a lifting means to move along the vertical structure as the crane raises or lowers the wind turbine component. In this manner, the dolly may be positioned to maintain a desired relationship with the wind turbine component as it is moved to a predetermined installation location using the crane. This may facilitate providing desired stability and support to the wind turbine component during installation. Generally, the dolly may follow upward toward the top of the vertical structure. When the dolly reaches an end position, the wind turbine component may be released from the dolly and moved to its final position supported only by one or more wires from the crane. In certain examples, the crane for lifting the blades or nacelle may be a crane external to the wind turbine tower. In certain examples, the crane for lifting the blades or nacelle may be a crane supported on the wind turbine tower.

[0014] The dolly may comprise blade holding means for holding the wind turbine blades. The advantage of the blade holding means is that the dolly can be easily used to lift and support the wind turbine blades during the blade installation process.

[0015] The blade retaining means may be configured to change position between a first position and a second position, wherein the blade retaining means in the first position is configured to retain the wind turbine blade in a substantially horizontal orientation and the blade retaining means in the second position is configured to retain the wind turbine blade in a substantially vertical orientation.

[0016] Holding the wind turbine blades in a substantially vertical orientation reduces their exposure to the wind, thereby minimizing stress on the lifting means and vertical structure, and also keeps the center of mass of the wind turbine blades close to the wind turbine tower during installation.

[0017] The carriage may comprise tilting means for tilting the blade holding means about a horizontal axis, so that the mounting of the wind turbine blade is moved closer to or further away from the wind turbine tower, thereby allowing fine adjustment of the position of the mounting relative to the nacelle.

[0018] The structure may include a lifting and handling device on a carriage. The lifting and handling device is typically a crane with at least one crane arm that typically extends from the carriage in a raised position and is configured to position the lifting point of the crane above the nacelle at the top of the wind turbine tower. A crane on a carriage may be referred to as a utility crane.

[0019] The carriage may be operable in one configuration in which the carriage is connected to the vertical structure and follows a guide track longitudinally along the front of the tower, and in another configuration in which the carriage is connected to the vertical structure and follows a guide track longitudinally along the side of the tower.

[0020] More specifically, the carriage may be rotatably coupled to the vertical structure to rotate about a vertical axis of the structure between the one and other configurations described above. Alternatively, the structure may further comprise a platform configured to be supported on the wind turbine tower. The vertical structure is rotatably coupled to the platform so as to rotate the vertical structure to which the carriage is connected about a vertical axis relative to the platform, thereby moving the carriage between the one and other configurations described above. The rotation between the one and other configurations described above is typically 90 degrees.

[0021] The vertical structure may comprise a crane tower or utility tower, on the top of which a crane may be supported. According to a second aspect, the present invention relates to a method for raising and lowering at least one wind turbine blade, the method comprising providing a structure according to the first aspect of the invention, raising and lowering the wind turbine blade along a wind turbine tower using a carriage, and rotating the blade from a horizontal orientation to a vertical orientation during the raising.

[0022] According to a third aspect, the present invention relates to a method of raising and lowering a nacelle for installation on a wind turbine tower, the method comprising providing a structure according to the first aspect of the invention, raising and lowering the nacelle using a plurality of crane wires suspended from a crane, and supporting the nacelle adjacent to the wind turbine tower by a bogie.

[0023] According to a fourth aspect, the present invention relates to a method of raising and lowering a wind turbine tower section for installation on a partially constructed wind turbine tower, the method comprising providing a structure according to the first aspect of the invention, raising and lowering the wind turbine tower section using a plurality of crane wires suspended from a crane, and supporting the wind turbine tower section adjacent to the wind turbine tower by a carriage.

[0024] According to a fifth aspect, the present invention relates to a method of replacing a component of a nacelle on a wind turbine tower, the method comprising providing a structure according to the first aspect of the invention, raising and lowering a component on a carriage, and using a crane on the carriage to lift the component off the carriage, reach over the area between the carriage and the nacelle, and lower the component onto the nacelle. The component may be a generator component. The method may include using a crane on the carriage to reach over the nacelle and remove the replacement component.

[0025] Any of the first to fifth aspects of the invention may further comprise any one or more of the further components or steps described in relation to any other aspect of the invention, wherever described herein.

[0026] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0027] [Figure 1A] 1 shows a floating wind turbine structure for mounting wind turbine blades. [Figure 1B] FIG. 1B is a detailed view of a portion of FIG. 1A showing how the carriage holds the wind turbine blades. [Figure 1C] 10 shows a schematic representation of an exemplary lifting means for moving the carriage along the vertical structure. [Figure 2] 1 shows the carriage in a first position holding the wind turbine blade horizontally. [Figure 3] 12 shows the carriage approaching a second position, holding the wind turbine blade vertically. [Figure 4] 1 shows the structure in use to install a nacelle on top of a wind turbine tower, with the bogie and nacelle shown in two positions A and B. [Figure 5] FIG. 10 is a perspective view of another floating wind turbine structure used to lift and handle wind turbine components inserted into or removed from a nacelle housing. [Figure 6] FIG. 6 is a side view of the structure of FIG. 5. [Figure 7] FIG. 7 is a top view of the structure of FIGS. 5 and 6 with the dolly in a first position prior to use. [Figure 8] 7 is a top view of the structure of FIGS. 5 and 6 with the dolly in a second position for moving up and down along the vertical structure. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1A and 1B show a mounting structure 100 for an offshore wind turbine 300. The wind turbine 300 comprises a turbine tower 32 and is shown with a crane arrangement 200 comprising a crane tower 21 with a crane 22 mounted on top. The crane tower 21 is supported by and surrounds the wind turbine tower 32.

[0029] The installation structure 100 comprises a vertical support structure, which in this example comprises a crane tower 21, and a carriage 10 for transporting the turbine blades 31 upward along the crane tower 21. As shown in more detail in FIG. 1C , the installation structure 100 further comprises a lifting means 5. The lifting means 5 includes a winch 28 with a plurality of winch wires 27 attached to the carriage 10. The crane tower 21 further comprises a longitudinal guide track 23 provided on the outside of the crane tower 21 and supported thereon as part of the crane tower 21. The guide track 23 is configured to guide the carriage 10 along the turbine tower 32 while the carriage 10 is being raised by the lifting means 5, i.e. while the carriage 10 is being pulled upward by winding up each winch wire 27. Furthermore, the carriage 10 comprises blade holding means 2 for holding the wind turbine blades 31. The winch 28 of the lifting means 5 in a particular example is located in a convenient location on the crane tower 21, for example attached to the top of the crane tower or attached to the structure of the crane 22 itself.

[0030] During installation of the wind turbine blades 31, the carriage 10 is lowered along the turbine tower 32 using the lifting means 5, i.e., by unwinding each winch wire 27. The carriage 10 is guided by the longitudinal track 23. The blade holding means 2 is activated to engage with and hold the wind turbine blade 31. Subsequently, the carriage 10 holding the turbine blade 31 is raised along the turbine tower 32 by the lifting means 5. The turbine blade 31 can then be attached to the nacelle 33 at the top of the turbine tower 32 while being supported by the carriage 10. During the installation work, it is convenient for the carriage 10 to be fixed and positioned adjacent to the crane tower 21 by the installation structure 100 equipped with the guide track 23.

[0031] The installation of such blades does not necessarily require the use of a crane 22, as the carriage 10 can be configured to position the blade roots adjacent the nacelle as needed to make the connections. However, a crane 22 is typically used when installing a wind turbine tower section or nacelle. The tower section or nacelle being installed is then first connected to and suspended from a plurality of crane wires 25, and then may be lowered from the crane 22 directly to the base of the tower or onto the carriage 10.

[0032] The installation structure 100, the crane apparatus 200, and the wind turbine 300 will be described in more detail below. The wind turbine 300 comprises a floating base 39 and a wind turbine tower 32 with a nacelle 33 located on top. The nacelle 33 is shown with two blades 31 fixed to it. The figure also shows a crane arrangement 200 surrounding the wind turbine tower 32.

[0033] The crane apparatus 200 is shown supported on the wind turbine tower 32. The crane apparatus 200 comprises a platform 20, a crane tower 21, and a crane 22. The platform 20 is clamped to the wind turbine tower 32 at or near the lower end of the wind turbine tower 32. The crane tower 21 is supported on the platform 20 and comprises a cylindrical structure that surrounds the turbine tower 32. The crane 22 is attached to the upper end of the crane tower 21. FIGS. 1A and 1B show an embodiment in which a carriage 10 supported by a vertical support structure holds a blade 31 in a substantially vertical position near the nacelle 33 using a blade holding means 2. The vertical support structure allows the carriage 10 to move close to the wind turbine tower 21 as it transports the blade 31 upward toward the nacelle 33.

[0034] It will be appreciated that in other variations, the platform 20 can be attached to the wind turbine tower 32 in ways other than by clamping. In certain other examples, the platform 20 is mounted on a floating base 39. In land-based wind turbine examples, the ground or other foundation serves as the platform. In further land-based examples, the platform sits directly on the ground or other foundation without being attached to the wind turbine tower.

[0035] In the process of installing multiple wind turbine blades 31, the carriage 10 moves downward along the crane tower 21 and engages the blade holding means 2 with the wind turbine blade 31 arranged in a horizontal position. The carriage 10 then moves upward toward the nacelle 33, lifting the blade 31 while gradually rotating the blade 31 to a vertical position. The carriage 10 holds the blade 31 in a substantially vertical position facing the nacelle 33 while the blade 31 is fixedly attached to the nacelle 33. The carriage 10 can then be released from the blade 31 by disengaging the blade holding means 2, and move downward to engage another blade 31.

[0036] The dolly 10 will now be described in more detail with reference to Figures 1B and 1C. The carriage 10 comprises a body 1 and a blade holding means 2 having one or more pairs of clamping members 8 (two pairs shown) for gripping and holding a wind turbine blade 31. The blade holding means 2 is connected to the body 1 via a rotatable connection 3. The rotatable connection 3 is configured to rotate the blade holding means 2 about a horizontal axis, such that when holding the blade 31, the blade 31 can be rotated between a horizontal and a vertical orientation.

[0037] The rotatable connection 3 may have an axis of rotation between the body 1 and the blade holding means 2. The axis of rotation may have a substantially horizontal direction pointing outward from the wind turbine tower 32.

[0038] The carriage 10 further includes a track follower 4, which is attached to the body 1 and configured to move along a longitudinal guide track 23 on the crane tower 21. The guide track 23 extends vertically along the outside of the crane tower 21 between the platform 20 and the nacelle 33. The track follower 4 slides or rolls the carriage 10 along the guide track 23, allowing the carriage 10 to move along the crane tower 21 while being fixed to the crane tower 21. Each winch wire 27 engages an upper portion of the guide follower 4, allowing the carriage 10 to be raised or lowered using a winch 28. Furthermore, a power cable (not shown) connects a power source (not shown) on the platform 20 to the carriage 10 to provide power, for example, to rotate the blade holding means 2 and to operate the blade holding means 2 to grip and hold the blade 31. The winches 28 controlling each wire 27 may be located on or near the platform 20.

[0039] FIG. 2 shows the carriage 10 in a first position, with the blade holding means 2 oriented horizontally near the platform 20. To engage the turbine blade 31, the clamp members 8 are opened, allowing the turbine blade 31 to be inserted horizontally and the clamps to be closed. Insertion of each turbine blade into the blade holding means 2 can be facilitated by an external vessel or a movable rack (not shown) located on the platform 20 to hold each turbine blade 31 and feed it to the carriage 10. The carriage 10 with the attached turbine blade 31 is then raised and lowered using the lifting means 5. As the carriage 10 rises toward the nacelle 33, the blade holding means 2 rotates to orient the turbine blade 31 vertically. FIG. 3 shows the carriage 10 approaching a second position, with the turbine blade 31 held facing the nacelle 33 so that the turbine blade 31 can be attached to the nacelle 33.

[0040] 1B, the carriage 10 comprises eight hinged connections 6 (only five are shown) between the guide followers 4 and the body 1. Two pistons 7 (one is shown) are provided for tilting the body 1 to which the blade holding means 2 is fixed. Thus, by using the pistons 7, each turbine blade 31 can be slightly tilted. In this way, the mounting portion 31 a of each turbine blade 31 can be moved closer to or further away from the wind turbine tower 32 to facilitate alignment of the mounting portion 31 a with respect to the nacelle 33. The number of hinged connections 6 and / or pistons 7 may be different in other examples.

[0041] In other examples, the lifting means 5 may be configured differently and may, for example, comprise a rack and pinion drive mechanism for raising and lowering the carriage 10 along the vertical structure 23 .

[0042] The structure 100 described above can also be used, with some modifications, to facilitate the installation of a nacelle 33. An example is shown in FIG. 4. A plurality of crane wires 25 are connected to the nacelle 33. The bogie 10 facilitates lateral support and / or positioning of the nacelle 33. However, due to the considerable size and weight of the nacelle 33, the weight of the nacelle 33 is primarily supported by the crane 22 and the plurality of crane wires 25 under tension from the crane 22. The nacelle 33 is lifted by the crane 22 using the plurality of crane wires 25. The bogie 10 is actively controlled by a separate drive mechanism (i.e., a plurality of lifting means 5). During the lifting of the nacelle 33 by the crane 22, the bogie 10 moves upward along the crane tower together with the nacelle 33, maintaining the nacelle 33 positioned relative to the crane tower 22. For example, the bogie 10 may be provided with members or connections or other configurations to prevent uncontrolled lateral movement of the nacelle 33 so that the nacelle 33 is positioned close to the wind turbine tower 32 while it is being lifted along the tower. Thus, during lifting, the nacelle 33 is suspended from the crane 22, and the bogie 10 minimizes lateral movement of the nacelle 33 relative to the crane tower 22. As the nacelle 33 is lifted, the bogie 10 moves from position A to its terminal position B at the top of the crane tower. At terminal position B, only a small lifting distance remains to bring the nacelle 33 into connection with the wind turbine tower. If the bogie 10 is coupled to the nacelle 33 during the initial stage of lifting, the bogie 10 is uncoupled, releasing the nacelle 33 from the bogie 10. The crane 22 then lifts the nacelle 33 away from the carriage 10 as shown at position C and brings the nacelle 33 into connection with the wind turbine tower 32 .

[0043] Similarly, the structure 100 of FIG. 4 may be used in the process of constructing a wind turbine tower 32 to assist in lifting and supporting the wind turbine tower sections with the crane 22 and dolly 10.

[0044] The apparatus and methods described herein may be used as part of the process of installing, constructing, replacing or maintaining a wind turbine 300 . 5-8, another structure for a floating wind turbine is depicted generally as 600. Structure 600 is used in this example to lift and / or handle wind turbine components, such as components that may need to be inserted into or removed from the interior of nacelle 633.

[0045] Structure 600 has many components in common with structure 100 described above. Components corresponding to those described above in connection with Figures 1-4 are designated with the same reference numerals, increased by 500.

[0046] Wind turbine structure 600 comprises a vertical support structure in the form of a utility tower 521 disposed about and supported by wind turbine tower 532. Utility tower 521 is the same as or similar to crane tower 21 described above, except for the inclusion of crane 22. Utility tower 521 therefore comprises longitudinal guide tracks 523 disposed outside of and supported by utility tower 521 as part of utility tower 521. Tower 521 and platform 520 are supported on base 539 in this example.

[0047] The structure 600 further comprises a carriage 510, which is coupled to the multi-purpose tower 521 and configured to move up or down along the multi-purpose tower 521 while being guided by a guide track 523. This allows the carriage 510 to be raised or lowered to a desired height along the multi-purpose tower 521. Suitable lifting means are used to move the carriage to the appropriate position along the tower and raise or lower it. In this example, the lifting means comprises a wire 505, one end of which is connected to the carriage 510, which passes over a support member of the multi-purpose tower 521 and is passed to a winch on the platform 520. The winch winds or unwinds the wire 505 to appropriately move the carriage 510 along the track 523.

[0048] Attached to the dolly 510 in this example is lifting and handling equipment, in the form of a small utility crane 550, for performing lifting and handling operations. In Figures 5 and 6, the utility crane 550 is shown lifting a wind turbine component 560 that has been inserted into or removed from a nacelle 533. The component 560 may be, for example, a wind turbine generator component housed within the nacelle 533. The dolly 510 also includes a platform 511 on which the wind turbine component may rest, for example, while traveling along the tower. For example, a component removed from the nacelle may be placed on the dolly 510 and transported down the utility tower 521. A component to be inserted into the nacelle 533 may be placed on the dolly 510 and transported up the utility tower 521. With the carriage 510 in the upper position as shown in Figures 5 and 6, the crane 550 can lift parts from the platform 511 into the nacelle, and vice versa. The crane 550 has one or more arms that can extend laterally so that their suspension points are above the nacelle, from which parts suspended on crane wires can be easily lowered / raised, in this example through the access opening 534.

[0049] 7 and 8, the dolly 510 is positioned at or near the base of the utility tower 521. In FIG. 7, the dolly 510 is positioned at the front of the utility tower 521, with the platform 511 extending from the utility tower 521 forward of the blade deployment position. In FIG. 8, the dolly 510 is positioned on one side of the utility tower 521, with the platform extending outward from that side. Thus, the dolly 510 can be moved from the position in FIG. 7 to the position in FIG. 8 before the dolly 510 is used to attach the utility crane 550, and can be moved up and down the utility tower 521 along the longitudinal track 23. When the dolly 510 is in the front position as shown in FIG. 7, it can first be used in the manner described above in connection with FIGS. 1-4 to facilitate installation of the blades and / or nacelle. When the dolly 510 is in the side position as shown in Figure 8, a utility crane 550 may be mounted on the dolly 510 and used in the manner described in connection with Figures 5 and 6 to facilitate lifting components onto or from the nacelle 533. Using the dolly 510 with the utility crane 550 mounted in the side position may facilitate side access to the nacelle 533 without rotating the nacelle 533 and blades 531 relative to the wind turbine tower 532.

[0050] In this example, utility tower 521 includes a rotational connection to platform 520 such that it can rotate relative to platform 520 and wind turbine tower 532. Utility tower 521 can thus rotate 90 degrees about a vertical axis. The rotational connection may be, for example, a slewing ring connection. Carriage 510 is attached to utility tower 521 and can move with utility tower 521 as it rotates from the front position of FIG. 7 to the side position of FIG. 8.

[0051] However, in various examples, the dolly 510 with the utility crane 550 attached is used in a front position as shown in FIG. 8, and then the nacelle 533 is subsequently rotated to raise the dolly 510 along the track 23 to an upper position where it is positioned to the side of the nacelle 533.

[0052] Although the structure 600 is described above in relation to a floating wind turbine, it may alternatively be used with a bottom-fixed wind turbine or an onshore wind turbine.

Claims

1. A structure for use in the process of installing, constructing, replacing or handling parts of, or maintaining a wind turbine, a vertical structure at least partially supported by the wind turbine tower; a guide track connected to the vertical structure; a carriage configured to follow the guide track along the vertical structure; A structure comprising:

2. 10. The structure of claim 1, The structure further comprising lifting means for raising and lowering said carriage along said tower structure.

3. 3. The structure of claim 2, The lifting means comprises at least one winch and at least one wire.

4. 4. The structure of claim 3, The at least one winch is disposed on the crane tower.

5. The structure according to claim 3 or claim 4, The lifting means comprises a crane wire and at least one crane.

6. 10. A structure according to any one of the preceding claims, comprising:

10. A structure wherein the carriage comprises blade retention means for retaining wind turbine blades.

7. 7. The structure of claim 6, 1. A structure, wherein the blade retaining means is configured to move between a first position and a second position, the blade retaining means in the first position being configured to retain the wind turbine blade in a substantially horizontal orientation and the blade retaining means in the second position being configured to retain the wind turbine blade in a substantially vertical orientation.

8. The structure according to claim 6 or claim 7, The carriage comprises tilting means for tilting the blade holding means about a horizontal axis, so that the mounting of the wind turbine blades is moved closer to or further away from the wind turbine tower structure.

9. 10. A structure according to any one of the preceding claims, comprising: The structure further comprising a lifting and handling device on said carriage.

10. 10. The structure of claim 9, the lifting and handling device is a crane with at least one crane arm configured to extend from the carriage in a raised position to a lifting point of the crane above a nacelle at the top of the wind turbine tower.

11. 10. A structure according to any preceding claim, comprising: a bogie operable in one configuration in which the bogie is connected to a vertical structure and follows the guide track longitudinally along the front of the tower, and in another configuration in which the bogie is connected to the vertical structure and follows the guide track longitudinally along the side of the tower.

12. 12. The structure of claim 11, the structure further comprising a platform configured to be supported by the wind turbine tower; wherein the vertical structure is rotatably coupled to the platform so as to rotate the vertical structure to which the carriage is connected about a vertical axis relative to the platform, thereby moving the carriage between the one configuration and the other configuration.

13. 14. The structure according to claim 12 or claim 13, A structure wherein the rotation between said one configuration and said other configuration is 90 degrees.

14. 10. A structure according to any one of the preceding claims, comprising: The vertical structure comprises a crane tower.

15. A structure according to the preceding claim, A structure having a crane supported at the top of the crane tower.

16. 1. A method for raising and lowering at least one wind turbine blade, comprising: Providing the structure of any one of the preceding claims; using the carriage to raise and lower the wind turbine blade along the wind turbine tower; rotating the wind turbine blade from a horizontal position to a vertical position while the blade is rising; A method comprising:

17. 1. A method of raising and lowering a nacelle for attachment to a wind turbine tower, comprising: Providing the structure of any one of the preceding claims; Raising and lowering the nacelle using a plurality of crane wires suspended from a crane; supporting the nacelle adjacent to the wind turbine tower by the bogie; A method comprising:

18. 1. A method of raising and lowering a wind turbine tower section for attachment to a partially constructed wind turbine tower, comprising: Providing the structure of any one of the preceding claims; raising and lowering the wind turbine tower sections using a plurality of crane wires suspended from a crane; supporting the wind turbine tower section adjacent to the wind turbine tower by the bogie; A method comprising:

19. 1. A method for replacing a nacelle component on a wind turbine tower, comprising: Providing the structure of claim 9 or claim 10; Raising and lowering the part on the carriage; using a crane on the carriage to lift the component off the carriage and extend beyond the area between the carriage and a nacelle and lower the component onto the nacelle; A method comprising:

20. 20. The method of claim 19, using the crane on the carriage to reach above the nacelle and remove the part; The method further comprises:

21. 21. The method of claim 19 or claim 20, The method wherein the component is a generator component.

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