Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly ("directly driven") or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

The installation of wind turbine blades has become more and more of a challenging task due to the general tendency to increase the size and weight of modern wind turbines. Blades of modern wind turbines may be more than <NUM> or <NUM> meters, or even more than <NUM> meters long. During installation, the wind turbine blades may be hoisted towards the rotor hub.

A known way of mounting a wind turbine includes the steps of transporting the different elements to the site of the wind turbine, assembling the tower sections and the tower, lifting the wind turbine nacelle with a large crane and mounting the nacelle on top of the tower. Then the wind turbine rotor hub can be lifted with the crane and mounted to a rotor shaft and/or the nacelle. Alternatively, the hub can be mounted to the nacelle and then the nacelle-hub assembly can be hoisted.

Afterwards, one or more blades are mounted to the wind turbine rotor hub. The rotor hub generally comprises a plurality of annular mounting flanges. Pitch bearings can be arranged with the mounting flanges. The blade can comprise a plurality of fasteners, such as bolts, or pins or studs at its blade root. During installation, these fasteners are to be fitted into openings in the mounting flange or pitch bearing on the hub.

It is also known to hoist a complete rotor assembly, i.e. the hub with the plurality of blades, and mount it to e.g. the nacelle. But in order to mount a complete rotor assembly, a large surface area is required, which is typically not available e.g. in the case of offshore wind turbines.

It is further known to mount an incomplete rotor assembly on the nacelle, e.g. the hub with two blades and subsequently, mount the remaining blade. In these cases, the rotor with the two blades is normally mounted with the two blades pointing upwards, i.e. "bunny ears" configuration. There is thus no need for rotating the wind turbine rotor as the third blade could be vertically mounted from below. However, in order to be able to perform these operations, the prevailing wind speed has to be below a predetermined value for a prolonged period time. The period of time depends on the expected length of the installation step and a safety factor to be taken into account.

As mentioned before, blades can be mounted individually as well. It is known to mount each of the plurality of blades substantially horizontally (e.g. -30º - +30º with respect to a horizontal plane) or substantially vertically. This means that individual installation steps may require less time and may be performed at higher winds, thus increasing the time windows available for installation.

Wind is inherently variable and winds from different directions, turbulent winds, and wind gusts can act on the wind turbine blade during hoisting and may provoke sudden movements and possibly oscillations of the blade during the hoisting operation. Fitting the blade to a hub may thus be complicated and time-consuming.

For offshore installations, the installation can be even more complicated. The vessel carrying a crane may move under wind and wave forces. Also the wind turbine tower and the nacelle mounted on top of the tower can move under wind and wave forces.

Wind turbine farms may also be situated in remote sites, e.g. on hill-tops and typically in these places the lifting of the wind turbine blade may be subject to high winds.

Frequently difficulties can arise during the lifting operation due to oscillations. In order to perform the installation of the blade, manual aid is often required. This can lead to an increase of the risk for the operator.

The oscillation during hoisting operation may also lead to possible damage to the wind turbine blade or to other parts of the wind turbine. If for example a sudden movement occurs when a wind turbine blade is close to the hub, parts or components may be damaged e.g. the blade, a pitch bearing, blade fasteners.

In order to reduce oscillations of blades during hoisting and installation, the use of tagline systems is known, i.e. control ropes from a vessel or crane that are tied to a blade to prevent oscillations. However they may not completely prevent movements and blade oscillations caused by the wind.

The present disclosure provides examples of methods and tools that at least partially resolve some of the aforementioned disadvantages. A prior art example is disclosed in <CIT>.

In one aspect, a method for installing a wind turbine blade on a wind turbine hub is provided. The method comprises hoisting a blade towards the hub, and bringing the blade and the hub into contact through an adaptable resilient body such that the adaptable resilient body is compressed between the blade and the hub. The method further comprises reducing a dimension of the adaptable resilient body such that the blade approaches the hub and mounting the blade to the hub.

In accordance with this aspect, an adaptable resilient body can serve to absorb an impact in case of a sudden movement of a blade at it is hoisted towards the hub. Once contact has been made with the resilient body, the size of the body (in at least one dimension) may be reduced such that the blade approaches the hub. During this procedure the resilient body is compressed to an extent between the blade and the hub and thus supports the blade with respect to the hub and serves to absorb relative movements between hub or nacelle and blade. Such relative movement may be due to e.g. gusts of wind or wave impact in the case of offshore installation. Once the blade has sufficiently approached the hub, the blade can be mounted to the hub.

Resilient as used herein may be particularly understood as a property of a material or body to recoil or spring back into shape after bending, stretching, or being compressed. The term "resilient body" should be understood to cover bodies that are substantially flexible, or elastic. The resiliency of the body makes it possible for the body to absorb shocks or impacts while maintaining its structural integrity as well as the structural integrity of blade and hub.

And adaptable as used herein may be particularly understood as the ability of the body to change, shape, size, volume or position. Adaptable should be understood as covering e.g. pliable, variable, transformable.

In a further aspect, an assembly for assisting in mounting a wind turbine blade to a wind turbine hub is provided. The assembly comprises one or more shock absorbers having a body with a proximal end for mounting to one of the blades and the hub, and a contact surface for contacting the other of the blade and the hub. The body is configured to change a distance between the contact surface and the proximal end.

"Shock absorber" as used throughout the present disclosure should be regarded as any structure that because of material properties, structure, or shape has some flexibility or resiliency and thereby allows absorption of impacts, shocks, oscillations, vibrations and relative movements of the blade with respect to the hub.

In yet a further aspect, a wind turbine rotor hub comprising a mounting surface for mounting a wind turbine blade, a support plate, and a shock absorber mounted on the support plate is provided. The shock absorber is configured to change between a retracted configuration in which the shock absorber does not protrude beyond the mounting surface and a deployed configuration in which the shock absorber protrudes beyond the mounting surface.

<FIG> illustrates a perspective view of one example of a wind turbine <NUM>. As shown, the wind turbine <NUM> includes a tower <NUM> extending from a support surface <NUM>, a nacelle <NUM> mounted on the tower <NUM>, and a rotor <NUM> coupled to the nacelle <NUM>. The rotor <NUM> includes a rotatable hub <NUM> and at least one rotor blade <NUM> coupled to and extending outwardly from the hub <NUM>. For example, in the illustrated example, the rotor <NUM> includes three rotor blades <NUM>. However, in an alternative embodiment, the rotor <NUM> may include more or less than three rotor blades <NUM>. Each rotor blade <NUM> may be spaced from the hub <NUM> to facilitate rotating the rotor <NUM> to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub <NUM> may be rotatably coupled to an electric generator <NUM> (<FIG>) positioned within the nacelle <NUM> or forming part of the nacelle to permit electrical energy to be produced.

The wind turbine <NUM> may also include a wind turbine controller <NUM> centrally located within the nacelle <NUM>. However, in other examples, the wind turbine controller <NUM> may be located within any other component of the wind turbine <NUM> or at a location outside the wind turbine. Further, the controller <NUM> may be communicatively coupled to any number of components of the wind turbine <NUM> in order to control the operation of such components.

Furthermore, the wind turbine <NUM> may comprise a pitch system <NUM> for adjusting a blade pitch. Alternatively, the auxiliary drive system may comprise a yaw system <NUM> for rotating the nacelle <NUM> with the respect to the tower around a rotational axis. Details of both examples of auxiliary drive systems will be provided in the following. The dedicated controller <NUM> may be centrally located within the nacelle <NUM>. However, in other examples, the dedicated controller <NUM> may be located within any other component of the wind turbine <NUM> or at a location outside the wind turbine. The dedicated controller <NUM> may control a single auxiliary drive system or alternatively at least two of them.

The wind turbine <NUM> of <FIG> may be placed in an offshore or onshore location.

The wind turbine controller (or "central control system") <NUM> may include one or more processor(s) and associated memory device(s) configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). The wind turbine controller may perform various different functions, such as receiving, transmitting and/or executing wind turbine control signals and controlling the overall operation of the wind turbine. The wind turbine controller may be programmed to control the overall operation based on information received from sensors indicating e.g. loads, wind speed, wind direction, turbulence failure of a component and other.

The wind turbine controller may also include a communications module to facilitate communications between the controller and the components of the wind turbine and their individual control systems. the wind turbine controller may in operation communicate with a pitch control system, a yaw control system, a converter control system and other controls and components.

Further, the communications module may include a sensor interface (e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors to be converted into signals that can be understood and processed by the processors. It should be appreciated that the sensors may be communicatively coupled to the communications module using any suitable means as for example a wired connection or a wireless connection. As such, the processor may be configured to receive one or more signals from the sensors.

As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. The processor is also configured to compute advanced control algorithms and communicate to a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory device(s) may comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) may be configured to store suitable computer-readable instructions that, when implemented by the processor(s), configure the controller to perform the various functions as described herein.

<FIG> illustrates a simplified, internal view of one example of the nacelle <NUM> of the wind turbine <NUM> of the <FIG>. As shown, the generator <NUM> may be disposed within the nacelle <NUM>. In general, the generator <NUM> may be coupled to the rotor <NUM> of the wind turbine <NUM> for generating electrical power from the rotational energy generated by the rotor <NUM>. For example, the rotor <NUM> may include a main rotor shaft <NUM> coupled to the hub <NUM> for rotation therewith. The generator <NUM> may then be coupled to the rotor shaft <NUM> such that rotation of the rotor shaft <NUM> drives the generator <NUM>. For instance, in the illustrated embodiment, the generator <NUM> includes a generator shaft <NUM> rotatably coupled to the rotor shaft <NUM> through a gearbox <NUM>.

It should be appreciated that the rotor shaft <NUM>, gearbox <NUM>, and generator <NUM> may generally be supported within the nacelle <NUM> by a support frame or bedplate <NUM> positioned atop the wind turbine tower <NUM>.

The nacelle <NUM> is rotatably coupled to the tower <NUM> through the yaw system <NUM> in such a way that the nacelle <NUM> is able to rotate about a rotating axis or "yaw axis" RA. The yaw system <NUM> comprises a yaw bearing having two bearing components configured to rotate with respect to the other. The tower <NUM> is coupled to one of the bearing components and the bedplate or support frame <NUM> of the nacelle <NUM> is coupled to the other bearing component. The yaw system <NUM> comprises an annular gear <NUM> and a plurality of yaw drives <NUM> with a motor <NUM>, a gearbox <NUM> and a pinion <NUM> for meshing with the annular gear <NUM> for rotating one of the bearing components with respect to the other.

Blades <NUM> are coupled to the hub <NUM> with a pitch bearing <NUM> in between the blade <NUM> and the hub <NUM>. The pitch bearing <NUM> comprises an inner ring and an outer ring (shown in <FIG>). A wind turbine blade may be attached either at the inner bearing ring or at the outer bearing ring, whereas the hub is connected at the other. A blade <NUM> may perform a relative rotational movement with respect to the hub <NUM> when the pitch system <NUM> is actuated. The rotational movement is performed around a pitch axis PA and thus can be measured in degrees as will be further detailed in conjunction with <FIG>. The inner bearing ring may therefore perform a rotational movement with respect to the outer bearing ring. The pitch system <NUM> of <FIG> comprises a pinion <NUM> that meshes with an annular gear <NUM> provided on the inner bearing ring to set the wind turbine blade into rotation.

Even though the pitch axis is shown for only a single blade, it should be clear that each of the blades has such a pitch axis. And a single pitch system or a plurality of individual pitch systems may be used to rotate the blade around their longitudinal axes.

<FIG> illustrate an example of a method for mounting a wind turbine blade to a wind turbine hub.

In accordance with an aspect, a method for installing a wind turbine blade <NUM> on a wind turbine hub <NUM>. The method comprises hoisting a blade <NUM> towards the hub <NUM>. Then, the blade <NUM> and the hub <NUM> are brought into contact through an adaptable resilient body <NUM> such that the adaptable resilient body <NUM> is compressed between the blade and the hub.

<FIG> illustrates a situation in which the blade and the hub have just made contact. Then, a dimension of the adaptable resilient body <NUM> is reduced such that the blade approaches the hub. This is illustrated schematically in <FIG>. Then the blade may be mounted to the hub <NUM>.

The body according to the invention is adaptable in a controlled or active manner, i.e. actuators may be activated and/or controlled such that the blade can approach the hub in a controlled fashion.

In some examples, like in the example of <FIG>, the adaptable resilient body may be mounted on the hub <NUM>. In this example, hub <NUM> has a mounting flange <NUM>. A pitch bearing <NUM> is mounted on flange <NUM>. The adaptable resilient body <NUM> is mounted on a support plate <NUM>. The support plate <NUM> may be a pitch carrier plate carrying a pitch mechanism. Specifically, the pitch carrier plate may support a motor and gearbox assembly which are configured to drive a pinion. The pinion may engage with an annular gear for pitching the blade i.e. for rotating the blade around its longitudinal axis. The annular gear may be arranged with the blade or with the pitch bearing.

The support plate, or pitch carrier plate <NUM> may be integrally formed with the hub.

Alternatively, the pitch carrier plate <NUM> may be arranged between the hub and the pitch bearing.

The pitch bearing may include an inner bearing ring and an outer bearing ring with one or more rows of rolling elements in between the rings. The rolling elements may be e.g. balls or cylindrical rollers.

One of the bearing rings may be fixedly mounted to the hub, and the other bearing ring may be fixedly mounted to the blade. With this arrangement, the blade can rotate with respect to the hub.

The bearing ring that is to be fixed to the blade may have a plurality of holes <NUM> (for clarity purposes only two holes are shown). Before hoisting a blade towards the hub, the hub may carry the pitch bearing.

The blade <NUM> may include a mounting flange <NUM> at the blade root <NUM>. The flange <NUM> of the blade may carry a plurality of fasteners <NUM> which are adapted to mate with holes <NUM>. The fasteners may be e.g. pins, bolts or studs. The adaptable resilient body <NUM> may function as a shock absorber and may be arranged on the pitch carrier plate <NUM>. The blade <NUM> may carry a bulkhead <NUM> at or near blade root <NUM>. The body <NUM> may be compressed between bulkhead <NUM> and pitch carrier plate <NUM> as the blade is brought towards the hub.

In some cases, aligning and/or orienting the blade with respect to the hub may take place when the adaptable resilient body is compressed between the blade and the hub. The resilient body <NUM> may act as support for the blade.

Mounting the blade to the hub may comprise introducing a plurality of fasteners on the blade into holes of a pitch bearing mounted on the hub. This is schematically illustrated in <FIG>.

In some examples, one or more of the plurality of fasteners are guiding fasteners that are longer than other fasteners of the plurality of fasteners, and one of the guiding fasteners is introduced into a corresponding hole on the pitch bearing first. A guiding pin may be larger than the other fasteners and therefore be introduced into a corresponding hole on the hub. Once these guiding pins have been introduced, then the blade is properly oriented with respect to the hub.

In some examples, a dimension of the adaptable resilient body may be further reduced after at least one or more of the fasteners on the blade has been introduced into the holes on the pitch bearing of the hub. The remainder of the fasteners may then be introduced. That is, in some examples, the adaptable resilient body when in its fully inflated or deployed state avoids any contact between the fasteners and the hub, including possible longer guiding fasteners. Then, a first reduction of the resilient body may be performed to bring the guiding fasteners closer and be able to introduce them into corresponding holes. After these guiding fasteners have been introduced, a further reduction of at least one dimension of the adaptable resilient body may take place, such that the other fasteners can be attached. Possibly, a further reduction may take place during or after the insertion of the fasteners before removing the adaptable resilient body.

In some examples, hoisting the blade <NUM> towards the hub <NUM> may comprises attaching a blade holder to the wind turbine blade and hoisting the blade holder with a crane. Specifically, the blade holder may be configured to hold the blade close to its centre of gravity. The blade holder may be or include a sling. In some examples, the blade holder may be gripping unit that is configured to grip a blade. And in some examples, the gripping unit may include one or more degrees of freedom. For example, the gripping unit may be used to rotate and/or move a blade to align the blade with the hub.

A crane and taglines and the blade holder may be used to control movements of the blade. This applies both before the blade and hub (through the resilient body) make contact, and after they have made contact.

It may be seen in <FIG>, that a dimension of body <NUM> may be reduced to an extent that it does not protrude beyond a mounting surface of the hub to which the blade is mounted.

Once the blade has been mounted, the body <NUM> may be removed from the pitch carrier plate to which it was mounted. In some examples, the same body <NUM> be attached to the pitch carrier plate of the subsequent blade to be mounted. The assembly may take place on the ground, and the pitch carrier plate may then be hoisted to the corresponding flange of the hub. In other examples, a plurality of bodies is attached, i.e. at least one for each of the rotor blades.

<FIG> and <FIG> schematically illustrate two examples of wind turbine blades carrying a shock absorber. In an alternative example, one or more resilient bodies <NUM> or shock absorbers may be mounted to the blade <NUM>, rather than to the hub. Blade <NUM> may carry a plurality of fasteners <NUM> at blade root <NUM>. In the example of <FIG>, the shock absorber <NUM> may be mounted on bulkhead <NUM>.

In another example, like <FIG>, one or more shock absorbers <NUM> may be attached to a mounting flange <NUM> of blade <NUM>. A blade flange <NUM> may be relatively wide to provide sufficient surface area for mounting the shock absorbers <NUM>.

<FIG> schematically illustrate examples of shock absorbers for use in the installation of wind turbine blades on a hub.

According to an aspect, an assembly for assisting in mounting a wind turbine blade to a wind turbine hub is provided. The assembly comprises one or more shock absorbers <NUM> having a body with a proximal end <NUM> for mounting to one of the blade and the hub, and a contact surface <NUM> for contacting the other of the blade and the hub. The body is configured to change a distance between the contact surface and the proximal end.

In some examples, the body may be expandable. Specifically, the body may be inflatable. In some examples, the assembly may comprise a pneumatic system for inflating and deflating the body of the shock absorber. Such a pneumatic system may be mounted on the hub, or on blade.

A further example of an inflatable body <NUM> is shown in <FIG>. In the example of <FIG>, the body comprises a plurality of compartments <NUM>, <NUM>, <NUM> and <NUM> that are individually expandable. Each of the compartments may include a gas supply with a dedicated compressor to provide pressurized air to the compartments.

<FIG> shows the inflatable body in a fully deployed state. <FIG> shows the same inflatable body in which some of the compartments are not inflated anymore. A first contact between blade and hub may be established when the inflatable body is fully deployed. By releasing pressurized air, the height of the inflatable body may be controllably reduced, one compartment after another. The blade may thus be brought closer to the hub.

<FIG> shows a further inflatable body <NUM> with a plurality of independent compartments <NUM> - <NUM>. In this example, the compartments are not only arranged on top of each other, as in <FIG>, but also next to each other. By selectively inflating and deflating specific compartments, the shape of the inflatable body <NUM> may be varied. In a first instance, to absorb a first impact, the body <NUM> may be fully inflated as in <FIG>. Depending on the orientation and position of the blade, selectively compartments may be partly or completely deflated as in <FIG>. At the same time, a crane and/or blade holder may be used to force the blade towards the hub. As the size and shape of the body <NUM> is varied, a corrective movement may be applied to the blade, such that the blade is properly aligned and/or oriented with the hub.

In a further example, an adaptable resilient body such as the inflatable body <NUM>, may comprise compartments in various directions. A first direction has been illustrated e.g. in <FIG>, in which compartments are stacked on top of each other in a direction substantially along the longitudinal axis of a blade to be mounted. A second direction has been illustrated e.g. in <FIG> wherein along one direction perpendicular to a longitudinal axis of the blade compartments are provided. In further examples, such compartments may also provided along a further direction perpendicular to the longitudinal axis of the blade to be mounted. in a mounting plane or in the plane of the pitch carrier, the compartments may be provided along two directions that are perpendicular to each other.

In a further aspect, a wind turbine rotor hub is provided comprising a mounting surface for mounting a wind turbine blade, a support plate, and a shock absorber mounted on the support plate. The shock absorber is configured to change between a retracted configuration in which the shock absorber does not protrude beyond the mounting surface and a deployed configuration in which the shock absorber protrudes beyond the mounting surface.

In some examples, the wind turbine rotor hub may further comprise a pitch bearing and wherein the support plate is arranged between the hub and the pitch bearing.

In some examples, the support plate may be integrally formed with the hub.

In some examples, the shock absorber may have an inflatable body. In some of the examples, the wind turbine rotor hub may further comprise a pneumatic system for inflating and deflating the body of the shock absorber.

<FIG> schematically illustrate a further example of a shock absorber in a deployed state and in a folded state. In the examples shown so far, the shock absorbers have been shown to be inflatable or pressurized structures. However, other arrangements are possible. in <FIG>, a telescopic resilient body <NUM> is shown. Such a resilient body <NUM> may be mounted e.g. to the hub or to a blade as was shown before.

The shock absorber <NUM> may include a mounting surface at a proximal end and a resilient distal end <NUM> to absorb an impact of a hub with a blade. In this particular example, three independent bodies are shown. The base <NUM> may be attached to e.g. a hub. Intermediate body <NUM> may slide or otherwise be moved with respect to base <NUM>. The base <NUM> may include suitable guides. Distal body <NUM> may perform a similar movement with respect to intermediate body <NUM>. In its deployed state, the shock absorber may protrude beyond a mounting surface of the hub. Once contact has been made with a blade, the height of body <NUM> may be reduced such that the blade can approach the hub.

In the folded or retracted state, the shock absorber <NUM> does not protrude beyond a mounting surface of the hub, and the blade can thus be mounted. Transitioning from a retracted state to a deployed state may include inflating (in the case of an inflatable body or shock absorber), unfolding, telescopically extracting, expanding, hydraulic actuation or other.

<FIG> illustrates yet a further example of a shock absorber <NUM> that may be mounted on a hub in a process for mounting a wind turbine blade. In the example of <FIG>, the shape of the shock absorber, or at least a part of the shape of the shock absorber may be complementary to a part of the wind turbine blade. A male-female coupling may be established between a part of the shock absorber, e.g. the most distal part and a part of the blade, e.g. an inner edge of a blade flange <NUM>.

In this particular example, the shock absorber may include two separate substantially cylindrical compartments <NUM> and <NUM>. However, this is merely one possible example.

In further examples, the shock absorber may be mounted on a wind turbine blade and its shape may be adapted to engage with a portion of e.g. the pitch carrier plate.

Male-female couplings as schematically described herein may help in centering a wind turbine blade with respect to the hub.

Claim 1:
A method for installing a wind turbine blade (<NUM>) on a wind turbine hub (<NUM>) comprising:
hoisting a blade (<NUM>) towards the hub (<NUM>);
bringing the blade (<NUM>) and the hub (<NUM>) into contact through an adaptable resilient body (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) such that the adaptable resilient body (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is compressed between the blade (<NUM>) and the hub (<NUM>);
reducing a dimension of the adaptable resilient body (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) such that the blade (<NUM>) approaches the hub (<NUM>) in a controlled fashion; and
mounting the blade (<NUM>) to the hub (<NUM>).