Method and apparatus for adjusting ballast of a wind turbine blade

Abstract

A method of adjusting the mass distribution of a wind turbine blade in-situ, comprising providing a blade ballasting machine comprising a plurality of blade ballasting tools; locating the blade ballasting machine at a position adjacent to a region of the blade to which ballast is to be applied; operating a first ballasting tool to create an aperture in the surface of the wind turbine blade and operating a second ballasting tool to deliver a ballast material through the aperture. The invention extends to a blade ballasting machine configured to perform the method. Beneficially the examples of the invention enhance the maintainability of a wind turbine by reducing the need for a manual process for blade ballast adjustment.

Description

[0001] METHOD AND APPARATUS FOR ADJUSTING BALLAST OF A WIND TURBINE BLADE

[0002] TECHNICAL FIELD

[0003] This disclosure relates generally to schemes or apparatus for adjusting ballast in a wind turbine blade.

[0004] BACKGROUND

[0005] On occasion it is necessary to adjust the mass of a wind turbine blade. This process is often referred to as ‘reballasting’ in the sense of adding a ballast mass to a particular interior zone or region of a wind turbine blade so as to adjust its total mass or mass distribution.

[0006] Such a process may be needed after repair work has been carried out in order to correct some blade damage, or to fine-tune blade-to-blade mass differences to reduce rotating unbalance of a rotor to which the blades are attached.

[0007] Current processes for reballasting blades typically involve stopping rotation of the rotor and locking it in a set angular position the rotor while the repair is made in situ by personnel supported near to the blade, for example by a temporary platform or rappel equipment. However, as wind turbines increase in size, conventional approaches for reballasting blades are becoming less practical.

[0008] It is against this background that the invention has been devised.

[0009] SUMMARY OF THE INVENTION

[0010] According to a first aspect of the invention, a method of adjusting the mass distribution of a wind turbine blade in-situ is provided. The method comprises providing a blade ballasting machine comprising a plurality of blade ballasting tools; locating the blade ballasting machine at a position adjacent to a region of the blade to which ballast is to be applied; operating a first ballasting tool to create an aperture in the surface of the wind turbine blade and operating a second ballasting tool to deliver a ballast material through the aperture. An advantage of the invention is that it enables a ballasting operation to be carried out on the blade in-situ, that is to say, whilst the blade is attached to the rotor and mounted on the wind turbine, much more easily than has previously been the case. In prior art approaches, blade ballasting has been a manual process which has been carried out by specially trained technicians. Previous approaches are time-consuming and expensive, and are less practical in larger wind turbines, and particularly in an offshore context.

[0011] In order that the various ballasting tools may be aligned with the aperture so that each can perform its function, the method may include moving the second ballasting tool to the position of the aperture after the aperture has been created.

[0012] The method may further comprise: operating a third ballasting tool to detect the location of an internal ballast chamber for application of the ballast material, and / or operating a fourth ballasting tool to close the aperture after the ballast material has been delivered to the wind turbine blade and / or operating a fifth ballasting tool to apply a surface treatment to the aperture after delivery of the ballast material.

[0013] In some examples, the second, third, fourth and fifth ballasting tools may be moved into position after the previous ballasting tool has performed its operation. The movement may be carried out in different ways. For example, the ballasting tools may be fixed statically to the blade ballasting machine and the machine itself may move in order to bring each of the ballasting tools into alignment with the aperture, in turn. Alternatively, each of the ballasting tools may be movably mounted. This may be achieved by mounting each tool individually to the blade ballasting machine, for example through the use of a robotically controlled arm. Another approach may be to mount two or more of the ballasting tools on a movable support for example a movable carriage or carousel so that the different tools may be moved at the same time. In this way, an indexing mechanism can be provided to ensure that each of the ballasting tools operates on the same point as the aperture.

[0014] Optionally, the first ballasting tool may be operated to create an aperture whilst one or more of the other ballasting tools are still operating to close / seal a different aperture.

[0015] Advantageously, mounting the different ballasting tools on individual robotic arms provides flexibility in the location of the ballasting tools, albeit at the expense of some mechanical complexity. The step of delivering a ballast material to the ballast chamber may include delivering a specified dose / volume / mass of the ballast material. Thus, the first ballasting tool can be operated in such a way that a precise amount of ballast material can be added to the blade, as calculated beforehand.

[0016] It is envisaged that the blade ballasting machine may be located onto or against the blade in a variety of ways. For example the machine may be suspended by a cable or network of cables, for example from a crane, and controlled into position on a blade. In another approach, a UAV may be used to fly the blade ballasting machine to the blade and set it down in a particular location. The UAV may be an integral part of the blade ballasting machine, or may be separable from it.

[0017] The engagement between the blade ballasting machine and the blade may be enhanced through one or more of several measures. For example, a suction device may be operated to apply a force to the blade ballasting machine towards the blade surface. Further, a thruster device may be operated to apply a force to the blade ballasting machine towards the blade surface. Still further, a mechanical clamping device may be operated to clamp the blade ballasting device to the blade surface. Either of these options may be used individually or together.

[0018] The invention embraces a blade ballasting machine that is configured to adjust the mass distribution of a wind turbine blade whilst the blade is still installed on a wind turbine rotor. The blade ballasting machine comprises a support structure that supports a plurality of blade ballasting tools. The plurality of blast ballasting tools comprises an aperture creation tool configured to create an aperture in the surface of the wind turbine blade, and ballast delivery tool configured to deliver a ballast material through the aperture.

[0019] The blade ballasting machine may further comprise one or more of following: a detection tool configured to detect the location of an internal ballast chamber for application of the ballast material; an aperture closing tool configured to close the aperture after the ballast material has been delivered to the wind turbine blade; a surface treatment tool configured to apply a surface treatment to the aperture after delivery of the ballast material.

[0020] The various ballasting tools may be movably mounted to the support structure, as discussed above. Optionally the blade ballasting machine further comprises a drive arrangement configured to drive the blade ballasting machine along the blade surface. This enables the machine to drive to a required location for creating an aperture, or to fine tune its location once a suitable site for delivering ballast has been identified.

[0021] A further enhancement is for the blade ballasting machine to include a securing mechanism configured to secure the blade ballasting machine to the blade surface, wherein the securing mechanism comprises a suction device configured to apply a force to the blade ballasting machine towards the blade surface, and / or a thruster device configured to apply a force to the blade ballasting machine towards the blade surface, and / or a mechanical clamping device to clamp the blade ballasting device to the blade surface. Each of these devices may be used individually or combined as required to enhance the ability of the blade ballasting machine to maintain its hold on the blade.

[0022] It will be appreciated that preferred and / or optional features of each aspect of the invention may be incorporated alone or in appropriate combination in the other aspects of the invention also.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a front view of a horizontal axis wind turbine to which embodiments of the invention may be applied;

[0025] Figure 2 is a front view of a wind turbine blade of the wind turbine of Figure 1 ;

[0026] Figure 3 is a view of a blade ballasting machine configured to adjust the mass distribution of a wind turbine blade according to an example of the invention;

[0027] Figure 4 is a schematic diagram of a control system which may be used to control at least part of the blade ballasting machine of Figure 3;

[0028] Figure 5 is a schematic diagram of a ground station which is operable with the control system of Figure 4; Figures 6 to 10 are views of the blade ballasting machine of Figure 3 attached to a wind turbine blade depicting various operations that the blade ballasting machine may perform, according to an example of the invention;

[0029] Figure 11 is another view of the blade ballasting machine attached to a wind turbine blade in a vertical orientation;

[0030] Figure 12 is a flow chart that depicts as a method the various operational steps that the blade ballasting machine may perform.

[0031] DETAILED DESCRIPTION

[0032] In general terms, the examples of the invention provide apparatus and corresponding methods for adjusting the mass distribution of the blade or ‘ballasting’ by adding a ballast material to an internal zone of the blade, which may be a specific ballast chamber configured to receive the blast material. Notably, the blade does not have to be removed from the rotor for the method and apparatus to function, such that the blade ballasting is carried out in situ, whilst the blade is still attached to the rotor of the wind turbine.

[0033] The approach involves locating a blade ballasting machine at a position adjacent to a region of the blade to which ballast is to be applied. The blade ballasting machine may be located by an unmanned air vehicle (UAV), in which case the machine may form part of a suitable aerial platform. However, the UAV may then lift the blade ballasting machine to the blade and then detach from it. The ballasting machine may also be located by other techniques, for example it could be lifted by a crane.

[0034] In some examples of the invention, the blade ballasting machine is configured to generate a force to secure itself into engagement with the blade. In some examples, due to the horizontal orientation of the blade and the mass of the blade ballasting machine, this may not be needed. However, an additional means to apply a further force to the blade ballasting machine to urge it into engagement with the blade may be beneficial in improving the blade-machine connection. The means to apply a blade-engagement force to the blade ballasting machine is particularly advantageous in use cases where the machine is used on a blade oriented towards a vertical orientation. Therefore, the blade-engagement force emulates the effect of the blade ballasting machine being held in firm contact with the blade under self-weight if the machine were positioned on top of a blade oriented horizontally. In this use case, the force would be a lateral force, having a non-zero horizontal component, and typically a force that is predominantly or even exclusive directed horizontally.

[0035] To provide context for the invention, Figure 1 shows a horizontal axis wind turbine (HAWT) 2 that includes a tower 4, a nacelle 6 mounted at the top of the tower 4, and a rotor 8 supported on the nacelle 6. The rotor 8 includes a rotor hub 10 and three coplanar blades 12 supported by the rotor hub 10, each blade 12 extending radially from a root 14 at the rotor hub 10 to a tip 16. Each blade 12 has a generally aerofoil profile in transverse cross section which interacts with the wind to cause rotation of the rotor 8 which, in turn, drives a generator (not shown) to produce electrical energy.

[0036] Referring to Figure 2, the aerofoil profile of the blade 12 defines a leading edge 18 and a trailing edge 20 with respect to a sense of rotation of the blade 12, in use. The blade 12 is formed of a shell of a suitable material such as a fibre composite which encloses internal components of the blade. The outer surface 24 of the blade 12 is defined by several different layers of material (polymeric, elastomers, paint, etc), including an outermost topcoat, a second layer underneath the outmost topcoat, and a third layer underneath the second layer.

[0037] The blade 12 is shown having an interior chamber 26 towards the blade tip 16. The interior chamber 26 is known as a ballast chamber and is a defined region or zone that is configured to accommodate ballast material. Such ballast material may be needed to be delivered to the ballast chamber 26 in order to adjust the mass distribution of the blade and therefore provide a more rotationally balanced rotor. The ballast chamber 26 is typically located towards the blade tip 16 but may in practice be located anywhere in the blade.

[0038] Figure 3 illustrates a blade ballasting system or machine 30 according to an example of the invention for adjusting the ballast of the blade 12. It should be noted that the blade ballasting machine 30 is shown schematically in the following Figures so some components may be omitted for brevity. As such, the following figures and discussion are for explaining the main components and operation of the blade ballasting machine 30.

[0039] In Figure 3, the blade ballasting machine 30 is shown supported on the outer surface 24 of a blade 12 in a horizontal orientation. The blade ballasting machine 30 includes a main structure 32 which comprises a plurality of ballasting tools 34-42 which are used in this example to adjust the mass distribution of the blade 12. The main structure 32 includes a support structure 33 which supports the blade ballasting machine 30 on the blade surface 24 of the blade 12. The support structure 33 includes a plurality of legs 35, in this example, which spaces the main structure 32 away from the blade surface 24.

[0040] In overview, the blade ballasting tools comprise: a chamber locating tool 34, an aperture creation tool 36, a ballast delivery tool 38, a hole closing tool 40 and a surface treating tool 42.

[0041] The ballasting tools 34-42 are coupled to the main structure 32. In this example, the ballasting tools 34-42 are coupled to the main structure 32 so that they are able to move relative to the main structure 32. In this way, the ballasting tools 34-42 are each able to be moved to an optimum position for operation, as will be described in more detail below.

[0042] As will be explained in further detail below, each of the blade ballasting tools 34-42 has a particular role in adjusting the mass distribution of the blade 12. A brief discussion of each of the blade ballasting tools 34-42 now follows.

[0043] The chamber locating tool 34 has the function of locating the correct position into which ballast material should be delivered to the blade 12. As shown in Figure 3 schematically, a ballast chamber 26 is a defined region in the hollow interior of the blade 12 which is configured to receive and contain a ballast material. A suitable ballast material may be a two-part epoxy resin which can be delivered into the ballast chamber in a liquid form and which can then cure into a solid.

[0044] The chamber locating tool 34 may be any suitable tool for locating the ballast chamber 34. For example, it may be an x-ray imaging tool that is configured to detect the presence of the ballast chamber either directly, or indirectly by means of detecting an identifiable marker positioned in or near to the chamber. For example, a metallic marker may be clearly identified by the x-ray imaging tool enabling the ballast chamber to be located by the blade ballasting machine 30. The chamber locating tool 34 may also be a visual imaging device such as a camera. In such a case, the chamber locating tool 34 may be configured to identify a visual marker that denotes the presence of the ballast chamber 26 underneath it, this may be achieved by a fiducial marker (i.e. black and white checked pattern) on the blade surface 24.

[0045] Other means are acceptable, for example based on near field communications (NFC) technology with suitable NFC markers placed on the blade surface 24 or embedded therein.

[0046] It should be noted at this point that the functionality of the chamber locating tool 34 may be achieved in ways that do not rely on detecting directly the presence of the ballast chamber 26. For example, the tool control system 56 may be loaded with suitable mapping data that indicates the location of the ballast chamber 26 on the blade. Then, the ballasting machine 30 may travel to that specific location in order to be in the correct location for the ballast chamber 26.

[0047] The aperture creation tool 36 may take various forms. In one example, the tool 36 may be configured to create an aperture in the blade by removing a cover or plug from an existing aperture. In the illustrated example, however, the aperture creation tool 36 is in the form of a suitable boring tool or drill that is configured to bore a hole through the blade 12 in the direction of the ballast chamber 26. As is shown in Figure 3, the aperture creation tool 36 is oriented so that a drill bit 44 has an axis that is generally perpendicular to the blade surface 24. Precise perpendicularity is not required, however.

[0048] The ballast delivery tool 38 comprises a nozzle 46 which is configured to deliver a ballast material through the created aperture and into the ballast chamber 26. The ballast delivery tool 38 may further comprise a ballast supply, e.g a container of material such as an epoxy resin, for example a two-part container containing an epoxy and a hardener, and a pumping system to pump the ballast material through the nozzle. These components are not shown on Figure 3, but examples of their configuration are considered to be within the capabilities of a skilled person.

[0049] The closing tool 40 is configured to close the aperture that has been created by the aperture creation tool 36 and may be configured in any suitable way for this purpose. For example, it is envisaged that the ballast delivery tool 38 may be configured to fill the ballast chamber 26 to a level such that the ballast material also fills the aperture that was made in the blade 12. In such a case, therefore, the closing tool 40 may simply scrape off excess ballast material and create a flat surface.

[0050] In other examples, it is envisaged that the closing tool 40 may be configured to apply a plug to the open aperture in order to close it off and protect the interior of the blade 12 from outside elements.

[0051] Finally, the surface treating tool 42 is configured to apply a suitable surface treatment to the blade 12 in the region of the aperture. The surface treatment may be a layer of paint, for example, to ensure that the closed aperture blends in aesthetically with the surrounding surface of the blade 12. Considered more likely, though, is that the surface treating tool 42 may apply a suitable sealing substance to the blade surface 24 that covers the closed aperture. Such a measure would improve the weather resistance of the closure.

[0052] Each of the plurality of ballasting tools 34-42 may be movable with respect to the blade surface 24 so that the tools can be positioned appropriately to be in the correct location with respect to the required position for the aperture. This may be achieved in various ways.

[0053] It is envisaged that one way in which this may be achieved is for the ballasting tools 34-42 to be fixed relative to the main structure 32 and that the entire blade ballasting machine 30 could be caused to move relative to the blade surface 24.

[0054] Alternatively, the ballasting tools 34-42 may be mounted on the main structure 32 so that they are movable relative to it. In one approach, each of the ballasting tools 34-42 could be associated with a respective robotic arm (not shown) of a suitable configuration. In this way, each of the ballasting tools 34-42 may be provided with multiple degrees of freedom which would benefit the process of positioning the ballasting tools 34-42 for use.

[0055] Another option, as is illustrated in Figure 3, is that the ballasting tools 34-42 are mounted to a carriage 50. The carriage 50 is mounted to the main structure 32 of the blade ballasting machine 30 on a suitable movement control arrangement 52 that allows the carriage 50 to move with respect to the main structure 32. The movement control arrangement 52 may be a set of rails and rollers 54 that allows the carriage to slide in a linear fashion in a single degree of freedom. Another option is for the carriage to be controlled so that it can move angularly, in the manner of a carousel. In Figure 3, the movable carriage 50 is able to move left and right, in the orientation of the drawings, as it is coupled to the main structure 32 by the rollers 54.

[0056] In either configuration discussed above, means may be provided to enable the movable carriage 50 to be indexed through selected ones of a plurality of positions so that each of the ballasting tools 34-42 can be bought into position, in turn, so that they can be used on the blade 12. Further discussion of this process will be described later.

[0057] The blade ballasting machine 30 also includes a suitable tool control system 56 to provide over control of the functionality and operation of each of the ballasting tools 34-42. The tool control system 56 may include suitable services such as power and communication in order for the ballasting tools 34-42 and the movable carriage 50 to be operated as required. It is envisaged that the tool control system 56 may be configured for full-authority remote control over the functionality of the ballasting tools 34-42, and / or for supervisory control allowing for semi-autonomous operation of the tools.

[0058] The tool control system 56 comprises a suitable processing environment having a processor 57 and a memory 58 with associated on-board communications functionality, such as a data bus, so it is able to communicate with other on-board systems.

[0059] The blade ballasting machine 30 may be located on the blade by various means. As shown in Figure 3, the blade 12 is in a horizontal position and the blade ballasting machine 30 is resting on the upper surface of the blade 12. One option is for the blade ballasting machine 30 to be lifted to the blade by an appropriate hoist system, for example a crane. Another option is for the blade ballasting machine 30 to be carried to the blade by an unmanned air vehicle (UAV). Such a UAV can either remain in an airborne status above the blade ballasting machine 30 whilst it is in operation, or the UAV can depart from its position and leave the blade ballasting machine 30 on the blade 12 so that it can carry out its work.

[0060] In the illustrated example, the ballasting machine 30 includes a UAV system 60. The UAV system 60 may form part of the main structure 32 of the blade ballasting machine 30. The UAV system 60 may be separable from the main structure 32 or form an integral part of the main structure 32 so it is not separable from it.

[0061] The UAV system 60 may be a conventional configuration such as a multirotor design having two, four, six, or eight or more rotors. Figure 4 illustrates a system diagram of a typical architecture of a UAV system 60 which may be used in the implementation of the embodiments of the invention. In overview, the UAV system 60 includes: a UAV control system 62, one or more propulsion units 64, a power system 66, a communication system 68, a sensor suite 70, mission planning system 74 and a navigation system 76. The UAV system 60 may be operated in conjunction with a ground-or base-station computer system 80, hereinafter referred to as the ‘ground-station’, which will be described in more detail later with reference to Figure 5.

[0062] The UAV control system 62 is the main computing unit that controls the flight of the UAV system 60 by controlling the propulsion units 64 based on inputs from the sensor suite 70, mission planning system 74 and navigation system 76. The UAV control system 62 may implement remote control flight based on received control inputs from a ground-based controller, autonomous flight, based on its internal mission planning algorithms, or semi- autonomous flight, in which a blend of on-board mission planning and ground-based direction are used.

[0063] The main responsibility of the UAV control system 62 is as a lower layer controller which is responsible for positional control of the drone (altitude and lateral position), attitude control (pitch, roll and yaw), and velocity control (horizontal and vertical speed) based on remote control actions or based on self-generated flight directions. The UAV control system 62 comprises a suitable processing environment having a processor 82 and a memory 84 with associated on-board communications functionality, such as a data bus, so it is able to communicate with other on-board systems.

[0064] To directly control the flight profile the UAV control system 62 communicates with the one or more propulsion units 64. Four propulsion units 24 are shown here, as would be consistent with the UAV system 60 being a multirotor system. However, more or fewer propulsion units are also appropriate. For example an autonomous helicopter may have a single propulsion unit. The propulsion units 64 may be any suitable units for providing controllable flight for the UAV system 60, and may be electric motors driving suitable rotor blades, as are typical with multirotor systems of varying size and lift capacities. However, the propulsion units 64 may also be gas turbines or internal combustion engines, for example.

[0065] The on-board power system 66 is selected to be suitable for the propulsion units 64. For example, for electric motors the on-board power system 66 may be a battery pack, a fuel cell, or even an external power plug so as to receive electrical power from an external source. Conversely, the power system 66 could be an on-board fuel tank in the event that the propulsion units are gas-turbines or ICEs.

[0066] The communication system 68 provides the means to send and receive data to and from systems that are external to the UAV system 60. For example, the UAV system 60 may send telemetry data to the ground station 80. The communication system 68 may also receive data from external systems and, in this context, it may receive remote control commands from the ground station 80 if the UAV system 60 is operated in remote control flight mode. Alternatively, it may upload mission data from the ground station 80. The communication system 68 may direct signals by any means known in the art including, but not limited to, cellular or other phone-based networks, over remote-control radio frequency links, UHF or L-band frequency links, microwave frequency links, or other appropriate datalinks, networks, or communication paths.

[0067] The sensor suite 70 is operably connected to the UAV control system 62 and provides appropriate sensor data to assist operation. For example, the sensor suite 70 may comprise proximity detectors, a satellite-based positioning system, including for example differential GPS, RTK-GNSS, PPP-GNSS or any other local positioning system set up for positioning control, optical still and video cameras for carrying out inspection and guidance tasks, or inertial navigation systems to name a few examples. Typically, such a sensor suite 70 would be adaptable to carry more or fewer sensors as required for a particular task. Note that in this context the GPS unit may receive signals directly from satellites in order to fix the position of the UAV system 60, although another option would be to implement a differential GPS system (known in the art) which receives signals from a ground-based differential GPS beacon in order to provide a higher positional accuracy compared to direct GPS. Note that a GPS unit 84 is shown here as integral with the navigation system 76. The sensor suite 70 may also incorporate a suitable camera / video / imaging system to permit remote monitoring of the blade ballasting machine 30 for assistance in remote control or supervisory control.

[0068] Mission planning system 74 provides a link to the ground station 80 to store missions that have been generated thereon and to which the UAV system 60 follows in use. The mission planning system 74 may include suitable memory storage and algorithms to store, provide and generate on the fly appropriate mission objectives, waypoints, operational envelopes and so on. Navigation system 76 provides control inputs to the UAV control system 62 regarding path following based on inputs from GPS data from the sensor suite 70.

[0069] Having described the functional components of the UAV system 60, discussion will now turn to the ground station 80 as shown in Figure 5. Ground station 80 provides a control hub for the UAV system 60 and is suitably equipped with a computing platform 86 having an appropriate processing module 88 and memory storage 90. The computing platform 86 implements a suitable control station software package 92 to provide appropriate control station facilities for controlling and coordinating the UAV system 60. For example, the software package may include telemetry feeds, status information updates, first person visual (FPV) feeds, mission planning interfaces and algorithms and so on. A user interface 94 is provided to enable to a user / operator to view data relating to the UAV system 60 and to input control and parameter data into the ground station 80. The user interface 94 may comprise of a display screen and audio output, and a user input means such as a keyboard, joystick, mouse, on-screen buttons or a combination of these. The ground station 80 also has a communications system 96 to send data to and receive data from the UAV system 60.

[0070] It should be appreciated that the above description of a UAV system 60 is intended as merely an example of the main components of an autonomous air vehicle and that other components may also be included in a typical system. In general, it should be noted that drones for use in the embodiments of the invention are known and are able to perform in remote control flight modes, semi- and fully-autonomous flights modes, and are able to carry out manoeuvres in a coordinated fashion in fixed positional relationship with other drones.

[0071] A suitable type of drone is the Griff 300 model from Griff Aviation, or a comparable heavylift drone.

[0072] In the above discussion, it will be noted that the tool control system 56 and the UAV control system 62 have been described as separate entities. However, it should be appreciated that the functionality provided by these systems may be combined into a single computing environment.

[0073] As has been described above, the blade ballasting machine 30 is supported on the blade surface 24 by a plurality of legs 35. The legs 35 may be static and simply provide support for the blade ballasting machine 30, or they may also provide further functionality. A first functionality is that the legs 35, and more broadly the support structure 33 embodied as the legs 35, may provide a locomotive function for the blade ballasting machine 30. Such a locomotive function may be provided by powered wheels or a tracked arrangement. Alternatively, the legs 35 may be arranged into a ‘walker’ configuration with powered joints enabling the legs 35 to move relative to one another in a suitable manner to enable the blade ballasting machine 30 to be moved relative to the blade 12.

[0074] In a further example, the support structure 33 may be configured to generate a force on the blade ballasting machine 30 to urge it against the blade surface 24 therefore ensuring that it is properly secured and not likely to slip. To this end, one example is for one or more suction devices to be provided. In Figure 3, suction devices 96 are provided on the end of the legs 35. Here, the suction devices 96 are in the form of cups through which a partial vacuum can be applied to ensure that the blade ballasting machine is ‘stuck’ to the blade surface 24 during operation. A vacuum generator 97 is provided on the main structure 32 to generate the required suction force. Such a suction force can also be combined with a locomotive function for the support structure 33 since suction can be applied by way of wheels or tracks.

[0075] The discussion will now turn to Figures 6 to 10 which show various stages of operation of the blade ballasting machine 30, together with Figure 12 which illustrates the following procedure specifically as a method 200 of operation.

[0076] In Figure 6, the blade ballasting machine 30 is shown as being located (step 202; Figure 12) on a blade surface 24 much like in Figure 3. Here, the chamber locating tool 34 is shown as operating to detect the location of the ballast chamber 26. The movable carriage 50 may move during operation of the chamber locating tool 34 in order for it to find the optimum location. Alternatively, the blade ballasting machine 30 may drive about the blade surface 24 whilst the chamber locating tool 34 is operating / scanning to locate the ballast chamber 26. Whilst locating the ballast chamber 26, the chamber locating tool 34 may also be configured to determine the current capacity of ballast in the ballast chamber 36, which may be achievable with suitable scanning functionality such as x-ray. This will be helpful in circumstances where the ballast chamber 26 has already been filled partially with ballast material and the empty capacity needs to be determined. Once the ballast chamber 26 has been identified, the tool control system 56 identifies an appropriate point for operation of the aperture creation tool 36.

[0077] In Figure 7, the aperture creation tool 36 is shown operating. Here, the movable carriage 50 is shown as having moved to the right, in the orientation of the Figures, so that the aperture creation tool 36 is brought into alignment with the point identified by the tool control system 56 in the previous step. The aperture creation tool 36 is shown as a boring device such as a drill in the illustrated example and in Figure 7 has bored a hole / aperture 98 through the blade surface and into the ballast chamber 26 (step 204; Figure 12).

[0078] In Figure 8 the ballast delivery device 38 is shown operating (step 206; Figure 12). Here, the movable carriage 50 is shown having moved again to the right thereby to bring the ballast delivery device 38 into alignment with the position on the blade surface 24 at which the aperture 98 has been created. Once the ballast delivery device 98 has been moved into the correct position, it is operated by the tool control system 56 to pump suitable ballast material into the ballast chamber 26, as is shown. This process may be controlled manually by an operator of the blade ballasting machine 30 e.g. by way of the ground station 80. As such, the operator may start operation of the ballast delivery device 38 to start the transfer of the ballast material into the ballast chamber 26 and then stop delivery of the ballast material when it is estimated that the correct amount has been delivered. Alternatively, the ballast delivery device 38 and / or the tool control system 56 may be configured to deliver a precise dose of the ballast material to the ballast chamber 26, that dose amount having been calculated previously. By way of context, the ballast delivery device 38 may be configured to deliver in the region of between 5kg and 20kg of ballast material to the ballast chamber 26.

[0079] Turning to Figure 9 here it is shown that the movable carriage 50 has moved to the left in the orientation of the Figures such that the closing tool 40 is brought into alignment with the aperture 98. The closing tool 40 may be configured to provide different functions depending on how the aperture 98 is to be closed. For example, a plug material may be pumped into the aperture 98. The plug material may be a different material to the ballast material, for example with different weather resistant properties, or it may be the same material. In some examples, it is envisaged that the ballast delivery device 36 may be configured to fill the ballast chamber 26 completely as well as fill the aperture 98. As shown, the closing tool 40 has inserted a plug 100 into the aperture 98 (step 208; Figure 12). The plug 100 may be a relatively soft polymeric material sized appropriately so that it defines an interference fit with the aperture 98. Other configurations of plug 100 are conceivable. The closing tool 40 may be configured with further functionality such as a scraper or sanding tool to smooth off the upper surface of the aperture 98 after it has been plugged.

[0080] Once the aperture 98 has been closed by the closing tool 40, the final step can be carried out. As shown in Figure 10, the movable carriage 50 has again been moved to the left, in the orientation of the drawings, such that the surface treating tool 42 is brought into alignment with the aperture 98 and operated to seal the aperture with a suitable surface treatment (step 210; Figure 12). In this example, the surface treating tool 42 has a substance-spraying function such that it can spray a layer of surface treatment over the aperture 98. The surface treatment may for example be a sealing lacquer or a paint which may ensure that the aperture 98 is weather tight.

[0081] After this final procedure, the movable carriage 50 may be caused to reset its position so that it returns to the configuration shown in Figure 6. It should be noted that in principle any of the ballasting tools 34-42 may be operated from any position of the movable carriage 50. However, in it also envisaged that the ballasting tools 34-42 may only be operated from a single position, such as from a central position relative to main structure 32 of the blade ballasting machine 30 as is shown in Figures 6 to 10.

[0082] An advantage of the invention is that it enables a ballasting operation to be carried out on the blade in-situ, that is to say, whilst the blade is attached to the rotor and mounted on the wind turbine, much more easily than has previously been the case. In prior art approaches, blade ballasting has been a manual process which has been carried out by specially trained technicians. Previous approaches are time-consuming and expensive, and are less practical in larger wind turbines, and particularly in an offshore context.

[0083] As mentioned above, in the illustrated example the blade ballasting machine 30 incorporates the main structure 32, which carries the blade ballasting tools 34-42, wherein the main structure 32 is combined with the UAV system 60 which provides the blade ballasting machine 30 with a means to be transported to and from the blade 12, but also to be repositioned on the blade 12. As is also mentioned, in other examples the main structure 32 of the blade ballasting machine 30 may be transported in other ways. For example, the blade ballasting machine 30 may be hung from a crane and positioned on the blade, or the blade ballasting machine 30 may be suspended from a network of cables in order to position the blade ballasting machine 30 selectably in three-dimensional space so that it can be located onto the blade 12 as required.

[0084] Although the orientation of the blade ballasting machine 30 is shown as being horizontal in the illustrated examples, such that the machine is working on a horizontally-oriented blade, it is also envisaged that the blade ballasting machine 30 may be configured to work on vertically-oriented blade, or at least blades that are not oriented in a precise horizontal orientation.

[0085] Figure 11 shows an example of this. Here, the blade ballasting machine 30 as a main structure 32 which is comparable to the examples discussed above. Therefore, a detailed discussion of the features of the blade ballasting machine 30 will not be repeated. Instead, the discussion will focus on the differences.

[0086] In Figure 11 , the blade 12 is oriented generally vertically. Likewise, the blade ballasting machine 30 is oriented vertically. For this purpose, the blade ballasting machine 30 is suspended from an attachment point 102 by a cable 104. It should be noted that the location of the attachment point 102 and the number of attachment points 102 may be selected to ensure that the blade ballasting machine 30 can hang in a suitable orientation.

[0087] Here, the cable 104 is shown as depending from a crane 106, which is shown schematically, although the cable 104 may also be hung from a UAV system (not shown) or other aerial vehicle.

[0088] In this example, the blade ballasting machine 30 incorporates a system to provide a horizontally-oriented force which in effect presses the blade ballasting machine 30 against the blade surface 24. For this purpose, the blade ballasting machine 30 comprises a thruster unit 108 comprising a propeller 106 configured to rotate to generate the required pressing force. In this sense, the horizontally-oriented force does not need to be precisely horizontal, but should have a horizontal force component.

[0089] The thruster unit 108 may be controlled by comparable control system as has been discussed above in relation to the previously-illustrated examples. The skilled person will appreciate that modifications may be made to the specific embodiments described above without departing from the inventive concept as defined by the claims.

Claims

Claims1. A method of adjusting mass distribution of a wind turbine blade in-situ, the method comprising: providing a blade ballasting machine comprising a plurality of blade ballasting tools; locating the blade ballasting machine at a position adjacent to a region of the blade to which ballast is to be applied, operating a first ballasting tool to create an aperture in the surface of the wind turbine blade, and operating a second ballasting tool to deliver a ballast material through the aperture.

2. The method of Claim 1, further comprising moving the second ballasting tool to the position of the aperture after the aperture has been created.

3. The method of any one of the preceding claims, further comprising operating a third ballasting tool to detect the location of an internal ballast chamber for application of the ballast material.

4. The method of Claim 3, further comprising moving the third ballasting tool relative to the wind turbine blade prior to creating the aperture in the wind turbine blade.

5. The method of any one of the preceding claims, further comprising operating a fourth ballasting tool to close the aperture after the ballast material has been delivered to the wind turbine blade.

6. The method Claim 5, further comprising moving the fourth ballasting tool relative to the wind turbine blade to align with the aperture, after the ballast material has been delivered to the wind turbine blade.

7. The method of any one of the preceding claims, further comprising operating a fifth ballasting tool to apply a surface treatment to the aperture after delivery of the ballast material.

8. The method of Claim 7, further comprising moving the fifth ballasting tool relative to the blade surface to align with the aperture after the ballast material has been applied.

9. The method of any one of Claims 2, 4, 6 and 8, wherein, in moving the plurality of blade ballasting tools relative to the blade surface, the method comprises relocating the blade ballasting machine along the blade surface in a selected direction, and / or moving selected ones of the blade ballasting tools relative to the blade ballasting machine.

10. The method of any one of the preceding claims, wherein the step of operating the second ballasting tool to deliver a ballast material through the aperture comprises delivering a predetermined dose of ballast material.

11. The method of any one of the preceding claims, wherein the step of locating the blade ballasting machine at a position adjacent to a region of the blade comprises operating an unmanned air vehicle to move the ballasting machine to the required location.

12. The method of any one of the preceding claims, further comprising releasably securing the blade ballasting machine to the blade surface by at least one of i) operating a suction device to apply a force to the blade ballasting machine towards the blade surface, ii) operating a thruster device to apply a force to the blade ballasting machine towards the blade surface, and iii) operating a mechanical clamping device to clamp the blade ballasting device to the blade surface.

13. A blade ballasting machine comprising a support structure that supports a plurality of blade ballasting tools, the plurality of blast ballasting tools comprising: an aperture creation tool configured to create an aperture in the surface of the wind turbine blade, and a ballast delivery tool configured to deliver a ballast material through the aperture.

14. The blade ballasting machine of Claim 13, further comprising a detection tool configured to detect the location of an internal ballast chamber for application of the ballast material.

15. The blade ballasting machine of Claim 13 or Claim 14, further comprising an aperture closing tool configured to close the aperture after the ballast material has been delivered to the wind turbine blade.

16. The blade ballasting machine of any one of Claims 13 to 15, further comprising a surface treatment tool configured to apply a surface treatment to the aperture after delivery of the ballast material.

17. The blade ballasting machine of any one of Claims 13 to 16, wherein one or more of the plurality of ballasting tools are movably mounted to the support structure.

18. The blade ballasting machine of any one of Claims 13 to 17, further comprising a drive arrangement configured to drive the blade ballasting machine along the blade surface.

19. The blade ballasting machine of any one of Claims 13 to 18, further comprising a securing mechanism configured to secure the blade ballasting machine to the blade surface, wherein the securing mechanism comprises at least one of i) a suction device configured to apply a force to the blade ballasting machine towards the blade surface, ii) a thruster device configured to apply a force to the blade ballasting machine towards the blade surface, and iii) a mechanical clamping device to clamp the blade ballasting device to the blade surface.

20. The blade ballasting machine of any one of Claims 13 to 18, further comprising an unmanned air vehicle coupled to the support structure.

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