WO2025093095A1

WO2025093095A1 - Wind turbine ice protection

Info

Publication number: WO2025093095A1
Application number: PCT/DK2024/050266
Authority: WO
Inventors: Thomas S. Bjertrup Nielsen; Peter FYNBO; Stephen Jude BUGGY; Mohamed Hashim ARIYUR
Original assignee: Vestas Wind Systems AS
Current assignee: Vestas Wind Systems AS
Priority date: 2023-11-01
Filing date: 2024-11-01
Publication date: 2025-05-08
Anticipated expiration: 2026-05-01

Abstract

A pitch controlled wind turbine has a tower, a nacelle mounted on the tower, a hub mounted rotatably on the nacelle, and at least three blades. The wind turbine includes at least three blade connecting members, each blade connecting member extending between neighbouring wind turbine blades. The wind turbine has at least three pre- tension members, each being connected to one of the blade connecting members and to the hub via a tensioning device. The tensioning device is configured to provide pre- tension in the blade connecting member to which it is connected. An anti-icing system and/or a de-icing system is provided that includes one or more heating elements for protecting one or more of the blades. One or more electrical power source paths for the anti-icing system or de-icing system are routed between the hub and the heating element along at least one of the blade connecting members and pre-tension members.

Description

WIND TURBINE ICE PROTECTION

FIELD OF THE INVENTION

The present invention relates to a pitch controlled wind turbine having an anti-icing and/or a de-icing system.

BACKGROUND OF THE INVENTION

Wind turbines are often deployed in regions where cold temperatures and adverse weather conditions occur, leading to the formation of ice on the blades of the wind turbine.

The accumulation of ice on wind turbine blades poses several significant challenges. First, the overall weight of the blades can increase, potentially causing imbalances and mechanical stress on critical components. Moreover, ice build-up on the blades can disrupt aerodynamic performance which can result in reduced efficiency and costly maintenance. Furthermore, ice throw from the blades can lead to structural damage, impacting the longevity of wind turbines. This is a particular issue in pitch controlled wind turbines having blade load sharing connecting members, which include various additional components intended to support larger blades. These additional components may be susceptible to damage from the impact of increased mechanical stress and ice throw.

As a result, anti-icing systems aiming to prevent ice build-up and/or de-icing systems for removing accumulated ice have become important to ensure the reliable and continuous operation of wind turbines in cold climates.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a pitch controlled wind turbine comprising a tower, a nacelle mounted on the tower, a hub mounted rotatably on the nacelle, and at least three wind turbine blades, wherein each wind turbine blade extends between a root end connected to the hub via a pitch mechanism, and a tip end; the wind turbine further comprising at least three blade connecting members, each blade connecting member extending from a connection point on one wind turbine blade towards a connection point on a neighbouring wind turbine blade, where the connection point on a given wind turbine blade is arranged at a distance from the root end and at a distance from the tip end of the wind turbine blade; at least three pre-tension members, each pre-tension member being connected to one of the blade connecting members and to the hub via a tensioning device, the tensioning device provides radial movement of a radially inward end of the pre-tension member with respect to an axis of rotation of the hub due to extension or retraction of the tensioning device, each pre-tension member thereby providing pre-tension in the blade connecting member to which it is connected; and an anti-icing system and/or a de-icing system including one or more heating elements for protecting one or more of the wind turbine blades, wherein one or more electrical power source paths for the anti-icing system or the de-icing system are routed between the hub and the heating element along at least one of the blade connecting members and pre-tension members.

The provision of an anti-icing system and/or a de-icing system can protect the blades of the pitch controlled wind turbine having blade load sharing connecting members from the accumulation of ice. It should be understood that the term “ice” as used herein refers to frozen water, e.g. including ice, snow, sleet, hail, slush, and the like.

Reducing or preventing ice build-up on the blades helps avoid issues caused by ice accumulation such as increased mechanical stress on the turbine, increased load on mechanical components and reduced aerodynamic efficiency of the blades, reduced power generation efficiency, potential damage from ice throw, and increased downtime and maintenance as well.

Electrical heating elements provide a precise and controlled temperature increase so as to melt ice or prevent its build-up. Electrical heating elements can generate heat quickly and efficiently, rapidly melting ice and restoring functionality to a component of the wind turbine. Moreover, the provision of an electrical heating element removes the need for a manual or mechanical means of removing ice or preventing its build-up. Such manual intervention is highly complex when considering the typical size and location of wind turbines.

The blade connecting members may cause the wind turbine blades to mutually support each other, in the sense that loads on the wind turbine blades, in particular edgewise loads and to some degree flapwise loads, are ‘shared’ among the wind turbine blades.

The connection points on the wind turbine blades may be arranged at a distance from the root end which is between 10% and 60% of the length of the wind turbine blades from the root end to the tip end, preferably radially inboard of 50% of the length of the respective wind turbine blade from the root end, and more preferably radially inboard of 45% of the length of the respective wind turbine blade from the root end.

The connection points on the wind turbine blades may be arranged at a position where a thickness-to-chord ratio of the wind turbine blade is between 20% and 50%.

The wind turbine blades may each comprise an inboard blade part comprising the root end and an outboard blade part comprising the tip end. The inboard blade part and the outboard blade part may be connected to each other at a split position. The inboard blade part may be joined to the outboard blade part by a connection joint. The connection joint may comprise a connector. The connection joint may be at least partially covered by a fairing.

The connector may be a metallic component, preferably a cast component or a machined component. The connector may be a composite component. The connector may be a co-cured or co-bonded component. Providing such a connector may improve ease of manufacture of the connector and provide a lightweight, high strength connector.

The connector may be coupled to transfer load between a spar cap portion of the inboard blade part and a spar cap portion of the outboard blade part. The connector may be arranged to transfer load from the blade connecting members into the spar cap portion of the inboard blade part. This may improve the load transfer efficiency of the turbine blade as the spar cap portions may be designed to withstand higher loads relative to the blade shell.

Each tensioning device may comprise an actuator having a first portion coupled to the hub and a second portion movable with respect to the first portion and coupled to the respective pre-tension member.

Each wind turbine blade may be coupled to two of the blade connecting members. Each of the two blade connecting members may extend from respective connection points of one of the blades. Routing the electrical power source paths for the anti-icing and/or the de-icing system along the blade connecting members and the pre-tension members avoids the need for at least some of the power source paths to be routed within the blade. Routing the power source paths within the blade can make the power source paths difficult to maintain, access and can increase the need for or complexity of lightning strike protection for the blade. Furthermore, the blade mass moment of the blade may be higher due to power source cables needing to run to the root of the blade. In contrast, providing such electrical power source path along the blade connecting members and the pre-tension members may provide simpler access to the power source path, allowing for simple maintenance and reducing any downtime of the wind turbine if an issue arises with the electrical power source path. Lightning protection requirements for the blade may also be reduced, saving blade manufacturing and operational cost and time.

In some arrangements, routing the electrical power source paths as set forth may reduce or eliminate radio frequency emission from an interface connection between the blade and the nacelle.

In some arrangements, a lightning current transfer unit (LCTLI) may be provided to transfer lightning current from a blade to the nacelle (i.e. to be transferred through the tower into ground), in the event the blade is struck by lightning. Typically, a first LCTLI is provided between the blade and the hub, and a second LCTLI between the hub and the nacelle.

The first LCTLI is typically positioned on an outer surface at or toward the root end of the blade. The first LCTLI is thus exposed to the environment, making the unit susceptible to wear and erosion. Routing the electrical power source paths as described facilitates for the direction of lightning current from the blade to the hub via the electrical power source paths on the blade connecting members and/or the pretension members. In this way, the first LCTLI can be bypassed or removed altogether without a detrimental impact on the lightning protection of the turbine.

The blade connecting members and/or the pre-tension members may include conductive material. The conductive material may be a structural load carrying conductive material. The structural load carrying material may be for supporting the tensile load in the blade connecting members and/or the pre-tension members. The conductive material may be steel or carbon (e.g. pultruded carbon) for example. The conductive material may, in addition to supporting structural loads, may be for transferring electrical power along the power source path between the hub and the heating element.

Advantageously, the blade connecting members and/or the pre-tension members provide multiple functions in both providing support to the blades and providing power to the anti-icing system and/or the de-icing system. As such, the component parts required for the wind turbine is reduced, improving the simplicity of the wind turbine and facilitating simpler maintenance.

The blade connecting members and/or the pre-tension members may include structural load carrying non-conductive material, and further include conductive material for transferring electrical power along the power source path between the hub and the heating element. The structural load carrying non-conductive material may be for supporting the tensile load in the blade connecting members and/or the pre-tension members. The non-conductive material may be ultra-high molecular weight polyethylene (LIHMWPE) for example.

Advantageously, the blade connecting members and/or the pre-tension members can provide the routing for the electrical power source path between the hub and the heating element in the blade without structural load carrying material thereof being made completely of a conductive material. Non-conductive material is typically more lightweight than conductive material, thereby reducing the weight of the blade connecting members and/or the pre-tension members and thus reducing the mechanical load on the wind turbine, while the conductive material still facilitates the transfer of electrical power to a blade via the blade connecting members and/or the pre-tension members.

The conductive material may be embedded within the non-conductive material of the respective blade connecting member or pre-tension member.

Embedding the conductive material within the non-conductive material protects the conductive material against damage (e.g. from precipitation, debris or dust erosion), reducing the risk of the conductive material becoming damaged. The aerodynamic performance of the blade connecting members and/or the pre-tension members incorporating the conductive material can be optimised. Moreover, embedding the conductive material provides for a convenient means of positioning and supporting the power source path relative to the other components of the wind turbine, reducing the space and components required for the anti-icing system and/or the de-icing system. Specifically, the power source path can be provided without requiring any additional components for support. Instead, pre-existing components (i.e. the blade connecting member or pre-tension member) can be utilised to provide this function.

The conductive material may be attached to an outer surface of the non-conductive material of the respective blade connecting member or pre-tension member.

Attaching the conductive material in this way provides for a convenient means of positioning and supporting the power source path relative to the other components of the wind turbine, reducing the space and components required for the anti-icing system and/or the de-icing system. Moreover, the conductive material can be easily accessed, removed, or replaced by simply detaching the conductive material from the outer surface of the non-conductive material.

The conductive material is coupled to the respective blade connecting member or pretension member either inside or outside a profile of the non-conductive material of the respective blade connecting member or pre-tension member.

It should be understood that the term “profile” relates to a profile defined by a core structural load bearing element of the respective blade connecting member or pretension member. In this way, the respective blade connecting member or pre-tension member may have a recessed region that defines a channel or a hole inside which the conductive material may be coupled (i.e. coupled inside a profile). Alternatively, the conductive material may be coupled to the outer surface (i.e. the outer profile) of the respective blade connecting member or pre-tension member.

Coupling the conductive material in such a way provides for a secure and convenient means of providing the power source path to the blades of the wind turbine, making use of the profile of the respective blade connecting member or pre-tension member for support. The blade connecting members and/or the pre-tension members having the conductive material may further comprise a lightning protection system configured to isolate the conductive material from lightning attachment and for conveying lightning current.

The lightning protection system may include a conductive sheath or braided screen wrapped around at least a portion of the respective blade connecting member or pretension member.

Advantageously, the risk of the conductive material becoming damaged from a lightning strike is reduced as the lightning protection system will isolate the conductive material from lightning current. In this way, the risk of the conductive material becoming damaged by a lightning strike is reduced. As such, maintenance requirements of the wind turbine are reduced.

The lightning protection system may include a metal mesh or layer. The metal mesh or layer may be arranged circumferentially around the conductive material of the blade connecting members and/or the pre-tension members.

The electrical power source path may provide residual or inherent heat when transferring electrical power along the power source path between the hub and the heating element so as to protect the blade connecting member or pre-tension member from ice accumulation or de-icing (during operation of the heating element in the blade when electrical power is supplied along the power source path). The secondary effect of resistance heating by conveying electrical power along the blade connecting members and pre-tension members to power the blade heating element may obviate the need for a separate, dedicated electrical heating element to provide anti-icing or de-icing to the blade connecting members and pre-tension members.

Advantageously, the electrical power source path can serve to prevent or remove ice accumulation on the blade connecting member and/or pre-tension member. Protecting the blade connecting member or pre-tension member from ice-build up is important in pitch controlled wind turbines having load sharing blade connecting members. Such inherent or residual heat provides for a reduction in ice build-up and/or improved ice removal on the blade connecting member or pre-tension member without requiring any additional component parts, thereby reducing the complexity of the wind turbine. The anti-icing system and/or the de-icing system may include an electrical power distribution system for distributing electrical power to each of the wind turbine blades. The electrical power distribution system may include a power distributer housed within the hub.

Providing the power distributor in the hub can facilitate power distribution to each blade without requiring power distributors in each blade, which decreases blade mass and hence rotor load, and enables easier access for maintenance or repair. Furthermore, it may reduce the number of power distributors from three (i.e. one per blade) to one, and simplify blade design and manufacturing.

The anti-icing system and/or the de-icing system may include one or more sensors in or on one or more of the blade connecting members or the pre-tension members for detecting either ice accumulation or a condition in which ice accumulation will occur.

Proving the sensors on the blade connecting members or the pre-tension members may avoid the need for sensors on the blades for sensing conditions relevant to icing on the blades. This may have significant benefits in terms of reduced rotor mass, improved access to the sensors for maintenance or repair, and reduced need for lightning strike protection of the blades.

One or more sensors may be arranged in/on the hub, nacelle and/or blades for detecting either ice accumulation or a condition in which ice accumulation will occur.

The anti-icing system and/or the de-icing system may include one or more meteorological sensors (e.g. external to the wind turbine) that can detect conditions of the turbine.

The provision of a sensor or sensors can provide improved control to the anti-icing system and/or the de-icing system, and can provide up-to-date information to an operator regarding the conditions at the blade connecting members or pre-tension members. The energy requirements of the anti-icing system and/or the de-icing system may be reduced, in that the respective system only operates when required (e.g. the heating element on the blade may only be powered when a predetermined amount of ice has accumulated, orwhen weather conditions suggest ice will begin to accumulate), and is not continuously operating. The sensor may be one or more of: an accelerometer, temperature sensor, position sensor, load sensor or strain sensor.

The sensor may be one or more of a liquid water content sensor, ice detection sensor, aero pressure sensor, surface electrical resistance or impedance sensor.

The one or more sensors may be provided at multiple locations along the length of the blade connecting member or pre-tension member.

The one or more sensors may be provided along substantially the entire length of the blade connecting member or pre-tension member.

Advantageously, the sensors can obtain the necessary data in multiple locations along the length, or along the entire length, of a respective blade connecting member or pretension member, providing information to an operator regarding the state of the member in various positions. In this way, the likelihood of erroneous data being obtained is reduced, further preventing the operation of the anti-icing system and/or the de-icing system when not required.

Providing multiple sensors may improve the redundancy of the sensor arrangement, as if one sensor becomes faulty, the remaining sensors can still provide an indication as to the status of the blade connecting member or pre-tension member. Providing multiple sensors may also enable measurements, such as the resonant frequency of the blade connecting member or pre-tension member to be calculated, the change in which may indicate the degree of ice accumulation thereon.

The anti-icing system or the de-icing system may include a lightning protection system including a lightning discharge filter system, preferably the lightning discharge filter system is housed within the hub. The lightning discharge filter system may for example comprise an inductor coil, and isolation transformer, and/or a surge protection device.

Providing the lightning discharge filter system in the hub rather than in the blades can provide simpler access for maintenance and the like, as the interior of the hub can be easier to access than the interior of each of the blades. By removing electrical power supply routes for the blade heating elements from within the blades and routing these instead via the blade connecting members or pre-tension members may remove the need for lightning strike protection of electrical power supply routes within the blades.

The wind turbine may further comprise at least three pre-tension members, each pretension member connected between one of the blade connecting members and the hub, each pre-tension member arranged to provide pre-tension in the blade connecting member to which it is connected.

The pre-tension members may be connected to a common point or region arranged at or adjacent the hub.

The hub may comprise a hub member extending from the hub substantially along a direction defined by a rotational axis of the hub. The pre-tension members may be connected to the hub member.

The blade connecting members and/or the pre-tension members may comprise at least one bearing. The at least one bearing may be located at or towards a terminal end of the respective blade connecting member and/or pre-tension member. The bearing may be non-conductive. The electrical power source path may be decoupled from a respective blade connecting member and/or pre-tension member so as to be diverted around the at least one bearing.

Each wind turbine blade may comprise a leading edge, a leading edge extension, and a blade shell, wherein the leading edge extension extends forward of the leading edge, and the connection point of the respective wind turbine blade is located forward of the leading edge on the leading edge extension, and each wind turbine blade may further comprise a respective fairing extending over at least the leading edge extension. The electrical power source path may be decoupled from a respective blade connecting member within the fairing.

Advantageously, the electrical power source path does not extend over the bearing, avoiding any transmission of electrical power over the bearing. Decoupling the electrical power source path from a blade connecting member inside the fairing provides additional protection of the decoupled electrical power source path (i.e. the fairing provides coverage and protection from the environment), reducing the risk that the power source path becomes damaged and ineffective. The wind turbine may be an upwind wind turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows a front view of a wind turbine according to a first example;

Figure 2 shows a side view of the wind turbine;

Figure 3 shows a wind turbine blade;

Figure 4 shows a portion of a wind turbine according to a second example;

Figure 5A shows an exploded view of a connection joint;

Figure 5B shows a detailed view of a connector for connecting blade portions;

Figure 5C shows a wind turbine blade having a fairing;

Figure 6 shows a schematic of a wind turbine according to a third example;

Figure 7 shows a cross-sectional view of an example blade connecting member or pretension member;

Figure 8 shows an example blade connecting member or pre-tension member schematic having a sensor arrangement;

Figure 9 shows an example blade connecting member or pre-tension member schematic having an alternative sensor arrangement;

Figure 10 shows a schematic of a wind turbine according to a fourth example;

Figure 11 shows a cross-sectional view of an example blade connecting member or pre-tension member;

Figure 12 shows a schematic of a wind turbine according to a fifth example;

Figure 13 shows a cross-sectional view of an example blade connecting member or pre-tension member;

Figure 14 shows a cross-sectional view of an example blade connecting member or pre-tension member;

Figure 15 shows a flow diagram of a power distribution system in a wind turbine according to a sixth example.

DETAILED DESCRIPTION OF EMBODIMENT(S)

In this specification, terms such as leading edge, trailing edge, pressure surface, suction surface, thickness, and chord are used. While these terms are well known and understood to a person skilled in the art, definitions are given below for the avoidance of doubt. The term leading edge is used to refer to an edge of the blade which will be at the front of the blade as the blade rotates in the normal rotation direction of the wind turbine rotor.

The term trailing edge is used to refer to an edge of a wind turbine blade which will be at the back of the blade as the blade rotates in the normal rotation direction of the wind turbine rotor.

The chord of a blade is the straight line distance from the leading edge to the trailing edge in a given cross section perpendicular to the blade spanwise direction. The term chordwise is used to refer to a direction from the leading edge to the trailing edge, or vice versa.

A pressure surface (or windward surface) of a wind turbine blade is a surface between the leading edge and the trailing edge, which, when the blade is in use, has a higher pressure than a suction surface of the blade.

A suction surface (or leeward surface) of a wind turbine blade is a surface between the leading edge and the trailing edge, which will have a lower pressure acting upon it than that of a pressure surface, when the blade is in use.

The thickness of a wind turbine blade is measured perpendicularly to the chord of the blade and is the greatest distance between the pressure surface and the suction surface in a given cross section perpendicular to the blade spanwise direction.

The term spanwise is used to refer to a direction from a root end of a wind turbine blade to a tip end of the blade, or vice versa. When a wind turbine blade is mounted on a wind turbine hub, the spanwise and radial directions will be substantially the same.

The term outboard refers to a radial direction from the hub of the blade towards the tip end of the blade. The term inboard refers to a radial direction from the tip end towards the hub.

A view which is perpendicular to both of the spanwise and chordwise directions is known as a planform view. This view looks along the thickness dimension of the blade. The term web or shear web is used to refer to a longitudinal, generally spanwise extending, reinforcing member of the blade that can transfer load from one of the windward and leeward sides of the blade to the other of the windward and leeward sides of the blade.

Figures 1 and 2 show a pitch controlled wind turbine 1 according to a first example. Figure 1 is a front view of the wind turbine 1 , and Figure 2 is a side view of the wind turbine 1 . The wind turbine 1 includes a tower 2 and a nacelle 3 mounted on the tower 2. A hub 4 is mounted rotatably on the nacelle 3, and carries three wind turbine blades 5 projecting outwardly from the nacelle 3. While the example wind turbine 1 shown in Figures 1 and 2 has three blades 5, it will be appreciated that other numbers of blades

5 are possible.

When wind blows against the wind turbine 1 , the wind turbine blades 5 generate a lift force which causes a generator (not shown) within the nacelle 3 to generate electrical energy.

It will be appreciated that the wind turbine 1 depicted may be any suitable type of wind turbine 1. The wind turbine 1 shown is an upwind wind turbine, although it will be appreciated the wind turbine 1 may be a downwind wind turbine. The wind turbine 1 may be an onshore wind turbine such that the foundation is embedded in the ground, or the wind turbine 1 may be an offshore installation in which case the foundation would be provided by a suitable marine platform.

Three blade connecting members 6 interconnect neighbouring wind turbine blades 5 between connection points 7a, 7b on the wind turbine blades. The connecting members

6 are cables, e.g. metallic (e.g. steel) or polymer (for example comprising ultra-high molecular weight polyethylene - LIHMWPE) cables. In some examples, each wind turbine blade 5 is coupled to two blade connecting members 6. Each two blade connecting members 6 extend from respective connection points 7a, 7b on one of the blades 5. Each blade connecting member 6 may be independently moveable at the respective first and second connection points 7a, 7b to which it attaches. The connection point(s) 7a, 7b may include a bearing structure (see Figure 5B). A pre-tension member 8 extends between one of each of the blade connecting members 6 and a common point or region (not shown) arranged at or adjacent the hub 4. In the example shown in Figures 1 and 2, three pre-tension members 8 are provided, but it should be appreciated that more may be provided. The pre-tension members 8 extend to the hub 4. The pre-tension members 8 are configured to provide pre-tension in the blade connecting members 6. The pre-tension members 8 are typically cables, e.g. metallic or polymer cables.

The pre-tension members 8 are coupled or connected to the hub 4 by respective tensioning devices 9. Each tensioning device 9 provides radial movement of a radially inward end of the pre-tension member 8 with respect to an axis of rotation of the hub due to extension or retraction of the tensioning device 9. Each pre-tension member 8 thereby provides pre-tension in the blade connecting member 6 to which it is connected.

Although not illustrated, the tensioning devices 9 may include an actuator having a first portion coupled to the hub 4 and a second portion movable with respect to the first portion and coupled to the respective pre-tension member 8. The tensioning device 9 extends and retracts by movement of the second portion with respect to the first portion. Extension and retraction of the tensioning device 9 changes the tension in pre-tension member 8. The actuator may be a linear actuator, a rotary actuator or the like.

The wind turbine blades 5 have a root end 11 proximal to the hub 4 adapted to be connected to the hub 4, e.g. via a pitch mechanism. The wind turbine blades 5 have a tip end 12 distal from the hub 4. The blades 5 include a leading edge 13 and a trailing edge 14 that extend between the respective root end 11 and tip end 12. The blades 5 include a suction side 15 and a pressure side 16 (see Figure 3). A thickness dimension of the blade 5 extends between the suction side 15 and the pressure side 16.

The connection points 7a, 7b are provided between the root end 11 and the tip end 12 of a respective blade 5 (i.e. at a distance from the root end 11 and at a distance from the tip end 12). The connection points 7a, 7b may be between 10% and 60% of the length of the wind turbine blade 5 from the root end 11 to the tip end 12 in the radial direction but are preferably radially inboard of 50% of the length of the wind turbine blade 5 from the root end 11 to the tip end 12, and more preferably radially inboard of 45% of the length of the wind turbine blade 5 from the root end 11 to the tip end 12, e.g. around 30-40%. It will be appreciated that the connection points 7a, 7b may be adjacent each other. Alternatively, the connection points 7a, 7b may be spaced from one another.

The wind turbine 1 includes an anti-icing system and/or de-icing system 17. The anti- icing system and/or a de-icing system 17 is not shown in Figures 1 and 2 for purposes of clarity. The anti-icing system and/or the de-icing system 17 is configured for protecting one or more of the wind turbine blades 5. The anti-icing system may be configured to prevent or reduce ice accumulation on a given wind turbine blade 5. The de-icing system may be configured to remove accumulated ice on a given wind turbine blade 5. Preventing or reducing ice build-up on the wind turbine blades 5 avoids an increase in mechanical stress acting on the wind turbine 1 , as well as preventing a reduction in power generation efficiency. It should be understood that the term “ice” as used herein refers to frozen water, e.g. including ice, snow, sleet, hail, slush, and the like.

Figure 3 shows an example wind turbine blade 5. A thickness dimension of the blade 5 extends between the suction side 15 and the pressure side 16. Each blade 5 may have a cross section which has a substantially circular profile near the root end 11 . The blade 5 may transition from a circular profile to an aerofoil profile moving from the root end 11 of the blade 5 outboard. The blade 5 may include a "shoulder" 22 outboard of the root end 11 , which is the widest part of the blade where the blade 5 has its maximum chord. The blade 5 may have an aerofoil profile of progressively decreasing thickness in an outboard portion of the blade. The progressively decreasing thickness may extend from the shoulder 22 to the tip end 12.

Each of the blades 5 may be a split blade formed of an inboard blade portion 23 and an outboard blade portion 24 coupled together. Each blade portion 23, 24 has a blade shell 53 that defines a respective leading edge 42a, 42b, trailing edge 43a, 43b, suction side 44a, 44b, and pressure side 46a, 46b.

The inboard portion 23 and outboard portion 24 of each blade 5 may be connected at a connection joint indicated by connection line 40. The connection line 40 between the inboard and outboard blade portions 23, 24 may be a spanwise split, with the connection line 40 being chordwise. The inboard blade portion 23 extends from the blade root 11 to the connection line 40. The outboard blade portion 24 extends from the blade connection line 40 to the blade tip 12.

The connection joint may include any form of connection, for example a bolted connection. The connection joint may be at least partially covered by a fairing 20 (see Figure 5). With a split blade, the fairing 20 may span the gap between the two blade sections 23, 24 that are connected.

It will be appreciated that the blade 5 may have any number of blade portions 23, 24, with respective connection joints between them. Alternatively, the blades 5 may not be split blades and may instead extend continuously from the root end 11 to the tip end 12 without any connection joint.

As is shown in Figure 3, the anti-icing system and/or the de-icing system 17 includes one or more heating elements 18 for protecting the wind turbine blades 5. The heating element 18 is electrical, for example the heating element 18 may be a wire heating element (e.g. a nickel-chromium wire), a tubular heater, an infrared heating element or the like. The heating element 18 is configured to melt ice and/or prevent its build-up on a surface 10 of a wind turbine blade 5 (e.g. by heating an outer surface 10 of a blade 5 to a temperature at which ice formation and/or accumulation is reduced or prevented). Electrical heating elements 18 provide for a precise, efficient, and controlled temperature increase so as melt ice, evaporate water and/or prevent ice build-up.

The heating element 18 may be provided embedded, attached, or otherwise secured or coupled with/to a respective blade 5 (e.g. attached on the outer surface 10 of the blade 5 or at least partially embedded within the blade 5). It should be appreciated that any number of heating elements 18 may be provided at different positions along the length of the blade 5, or a heating element 18 may be provided that spans a substantial length of the blade 5.

One or more electrical power source paths 28 for the anti-icing system and/or the deicing system 17 are provided (e.g. for providing electrical power to the blade heating element(s) 18). In addition to ‘sharing’ the loads among the wind turbine blades 5, the connecting members 6 and/or the pre-tension members 8 can also assist in providing power to the anti-icing system and/or the de-icing system 17. Specifically, the one or more electrical power source paths 28 are routed between the hub 4 and the heating element 18 along at least one of the blade connecting members 6 and pre-tension members 8.

Electrical power source paths 28 are routed between the hub 4 to a heating element 18 on the blade 5 via a pre-tension member 8 and a blade connecting member 5, e.g. as shown in Figure 4. For example, electric power source paths 28 may be routed from the hub 4 to all of the pre-tension members 8 and to all of the blade connecting members 6 (e.g. to supply power to a heating element 18 on each of the blades 5). It should be appreciated that the electric power source path 28 may be routed along any number of the blade connecting members 6 and/or pre-tension members 8.

Routing the electrical power source paths 28 along the blade connecting members 6 and pre-tension members 8 avoids the need for power cables to significantly extend within the blade 5 which can be difficult to maintain and access. Utilising the blade connecting members 6 and pre-tension members 8 provides an electrical power source path that is easier to access and maintain.

In some arrangements, a lightning current transfer unit (LCTU) may be provided to transfer lightning current from a blade 5 to the nacelle 3 (i.e. to be transferred through the tower 4 into ground), in the event the blade 5 is struck by lightning. Typically, a first LCTU is provided between the blade 5 and the hub 4, and a second LCTU between the hub 4 and the nacelle 3. The first LCTU may include, for example, a blade band mountable to the root of the blade 5, a lightning ring, a blade part contact device and a nacelle side contact device mounted to the nacelle and adapted for providing lightning current transfer from the lightning ring.

The first LCTU is typically positioned on an outer surface at or toward the root end 11 of the blade 5. The first LCTU is thus exposed to the environment, making the unit susceptible to wear and erosion. Routing the electrical power source paths 28 as described (i.e. along the blade connecting members 6 and pre-tension members 8) facilitates for the direction of lightning current from the blade 5 to the hub 4 via the electrical power source paths 28 on the blade connecting members 6 and the pretension members 8. In this way, the first LCTU can be bypassed or removed altogether without a detrimental impact on the lightning protection of the turbine 1. The electrical power source path 28 may additionally provide residual or inherent heat when transferring electrical power along the power source path 28 between the hub 4 and the heating element 18. In this way, the electrical power source path 28 may protect the blade connecting member 6 or pre-tension member 8 from ice accumulation or de-icing (i.e. during operation of the heating element 18). The electrical power source path 28 may generate heat when electrical power is transferred therethrough via resistive heating, e.g. by selecting a material to provide the power source path 28 that has a low resistance, or by increasing the current flowing through the wire, or by any suitable means. Of course, the electrical power source path 28 may be dedicated to providing electrical power to the blade heating elements 18 and may not provide any additional heating or ice protection to the blade connecting member 6 or pre-tension member 8.

Configuring the electrical power source path to provide residual or inherent heat when transferring electrical power can serve to protect the blade connecting members 6 and/or pre-tension members 8 from ice build-up, as well as protecting the blades 5 without requiring any additional component parts.

The heating element 18 may be positioned on the outboard portion of the blade 5 where ice protection may be most needed due to the higher rotational speeds which can promote ice accumulation. Advantageously, the blade connecting members 6 may be further inboard on the rotor than the heating element 18 and so the blade connecting members may provide a convenient route for the power source path 28 to the heating element 18. Of course, the blade heating element 18 may additionally or alternatively be located further inboard than the blade connecting members 6 in which case the power source path 28 may be less direct when routed via the blade connecting member 6, but the advantages of avoiding routing the power source path 28 within the blade 5 remain. Where the blade 5 is a split blade having a connection joint, the connection joint may facilitate a simple means of transferring power from the electric power source path 28 on the blade connecting members 6 to the heating element 18. An example of such an arrangement is shown in Figure 5. It will of course be appreciated that on a blade 5 without a connection joint, the connection point for attaching the blade connecting member 6 to the blade 5 will still have a suitable rigid structure through which the power source path 28 may be configured to route to the heating element 18.

Figures 5A-5C indicate an example wind turbine blade 5 having a fairing 20. The blade portions 23, 24 are coupled by a connection joint that includes a connector 47. The connector 47 connects a first blade end surface 48 of the inboard blade portion 23 to a second blade end surface 27 of the outboard blade portion 24. The connector 47 is adapted to transfer load between the inboard blade portion 23 and the outboard blade portion 24.

A leading edge extension 49 may extend forward of the leading edge 13 of the blade

5. The leading edge extension 49 may be integrally formed with the connector 47, although it will be appreciated that in alternative examples the leading edge extension 49 may be a separate component to the connector 47. The leading edge extension 49 may include connection points 7a, 7b that attach to the connecting members 6. The first and second connection points 7a, 7b may be arranged forward of the leading edge 13 and adjacent the pressure side 16, such as shown in Figure 5A. This provides additional clearance for the connecting members 6 as the wind turbine blades 5 rotate with the hub 4 about the nacelle 3. In particular, sufficient clearance may be provided between the connecting members 6 and the blades 5 when the blades 5 are pitched between about -5 degrees and about +95 degrees. The connection points on the wind turbine blades 5 may be arranged at a position where a thickness-to-chord ratio of the wind turbine blade 5 is between 20% and 50%.

The connection points 7a, 7b may permit at least some freedom of movement of the connecting members 6 at its respective connection point. In the example shown in Figure 5B, the connection points 7a, 7b permit rotation of each blade connecting member 6 about the respective connection point 7a, 7b in two orthogonal rotational degrees of freedom. This allows each connecting member 6 to move independently of each other, thereby reducing constraints on the wind turbine 1 .

The two orthogonal rotational degrees of freedom may be provided by a bearing structure, for example as shown in Figure 5B. In this example, the first rotational freedom is provided by a pin 51 of the bearing structure about which a respective blade connecting member 6 is rotatable, and the second rotational freedom provided by a spherical plain bearing 52 between the pin 51 and the respective connecting member

6. However, it will be appreciated that other bearing structures may be applicable. The blade connecting member 6 and the pre-tension members 8 may include a bearing 50 at or towards each terminal end. The bearing 50 may define the terminal ends of a respective blade connecting member 6 or pre-tension member 8. In some arrangements, only one bearing 50 may be provided at or towards a terminal end of a respective blade connecting member 6 or pre-tension member 8. It should be understood that the term “terminal end” refers to a longitudinal end of the blade connecting member 6 or pre-tension member 8.

In Figure 5B, the bearing 50 is configured to assist in attaching the connecting members 6 to the bearing structure, e.g. the bearing 50 includes an eyelet for receiving the respective pin 51. Although not shown, the bearing 50 may be configured to connect a blade connecting member 6 to a respective pre-tension member 8, and to connect a pre-tension member 8 to a respective tensioning device 9.

The bearing 50 may non-conductive (i.e. not conduct electricity). For example, the bearing 50 may be formed from a non-conductive material. As shown in Figure 5B, the electrical power source path 28 on the blade connecting member 6 does not extend over the bearing 50. The electrical power source path 28 is decoupled from the blade connecting member 6 before reaching the bearing 50. The electrical power source path 28 may be diverted around the bearing 50, e.g. to the electrical heating element 18 on a blade 5. It will be understood that the power source path 28 may decouple from the blade connecting member 6 and the pre-tension member 8 before each terminal end so as to be diverted around the bearing 50 at each respective end.

Figure 5C indicates a fairing 20 extending over at least the leading edge extension 49. As mentioned previously, the wind turbine blade 5 may have a split and include the first blade section 23 and second blade section 24 coupled together, for example by the connector 47 as described above. With a split blade the fairing 20 may extend over the leading edge extension 49 and the connector 47.

The electric power source path 28 may be provided along the blade connecting member 6 and to the heating element 18 via the fairing 20. The fairing 20 may include an aperture 21 that receives the blade connecting member 6. The electric power source path 28 can also be routed through the aperture 21 and then be further directed from the fairing 20 to the heating element 18. The electrical power source path 28 may decouple from the blade connecting member 6 inside the fairing 20, (i.e. so as to be diverted around the bearing 50 within the fairing 20 and thus be directed to the heating element 18 on the blade 5).

The blade connecting members 6 and the pre-tension members 8 may be configured in numerous ways to accommodate the electric power source path 28. Examples of such configurations will now be discussed with reference to Figures 6 to 14. It should be understood that these figures may represent the blade connecting members 6 and/or the pre-tension members 8.

Referring firstly to Figure 6, a schematic of an example wind turbine 1 is indicated. The wind turbine 1 may be substantially the same as that described previously, and so only the differences will be discussed in detail. In the schematic, only one blade 5 is indicated and only one blade connecting member 6 and/or pre-tension member 8 is indicated. It should be appreciated that the same arrangement may be applied to any number of blades 5 and/or blade connecting members 6 and/or pre-tension members 8 of the wind turbine 1.

The anti-icing system and/or the de-icing system 17 includes an electrical power distribution system 25 configured to distribute electrical power to each of the wind turbine blades 5. The electrical power distribution system 25 is discussed in more detail with reference to Figure 15. The electrical power distribution system 25 includes a power distributer 26. The power distributor 26 may include power outlets, monitoring systems, safety features and the like. In Figure 6, the power distributor 26 is housed within the hub 4, although it should be appreciated that the power distributor 26 may be located in any suitable position. Locating the power distributor in the hub 4 protects the power distributor 26 from damage (e.g. from dirt, debris, ice, etc.) and facilitates an effective pathway of power to each blade 5 from a centralised location. Moreover, the centralised power distributor 26 in the hub 4 removes the requirement for power distributors in the blades 5. This may be beneficial in reducing blade mass and therefore rotor loads, enable improved access to the power distribution system 25 for maintenance, and reduce the need for or complexity of lightning strike protection of the blades 5.

Electrical power may be transmitted from the power distributor 26 in the hub 4 to a respective blade 5 via the electrical power source path 28 that is routed along a respective blade connector member 6 and pre-tension member 8. For example, the electrical power source path 28 may extend from the power distributor 26 in the hub 4, along a pre-tension member 8, along a blade connector member 6 and to a respective blade 5.

In Figures 6 to 14, the blade connecting members 6 and/or pre-tension members 8 includes a conductive material 29. The conductive material 29 may be any material suitable for transferring electrical power along the power source path 28 between the hub 4 and the heating element 18. The conductive material 29 may be any material or combination of materials capable of conducting electricity, e.g. copper, aluminium, steel, silver, gold, graphite, a copper alloy, carbon fibre, carbon fibre reinforced composite, a conductive polymer, tin, nickel, or combinations thereof. The conductive material 29 may provide the electrical power source path 28 along the blade connecting members 6 and/or pre-tension members 8.

In the example of Figure 6, the conductive material 29 is a structural load carrying conductive material. For example, the structural load carrying conductive material may be a metal. In this way, the conductive material 29 can serve to both provide the electrical power source path 28 between the hub 4 and the blade 5, but also provide the functionality of the blade connecting member 6 and/or pre-tension member 8 (i.e. supporting the load of neighbouring blades 5). In this way, the component parts of the wind turbine 1 are reduced, as a single cable can provide at least a portion of the electrical power source path 28 to the heating element 18 and can provide load sharing between neighbouring blades 5.

Figure 7 is a cross-sectional view of an example blade connecting member 6 and/or pre-tension member 8, e.g. the blade connecting member 6 and/or pre-tension member 8 of Figure 6. In this example, the entire cable of the blade connecting members 6 and/or pre-tension members 8 is formed from the conductive material 29. In this way, the entire blade connecting member 6 and/or pre-tension member 8 can provide the electrical power source path 28. It should be appreciated that other materials may also be present in some examples, e.g. a casing or sheath around the conductive material 29, as erosion protection, or as isolator splitting the conductive material into a plurality of conductive paths for example for different electrical phases or an electrical return path. Returning to Figure 6, the blade connecting member 6 and/or the pre-tension member 8 may include a lightning protection system 30 configured to isolate the conductive material 29 from lightning current. The lightning protection system 30 may couple the blade connecting member 6 and/or pre-tension member 8 to ground (e.g. via the hub 4, through the tower 2 and nacelle 3, to ground). The lightning protection system 30 may include a lightning receptor mounted to the blade connecting member 6 and/or pre-tension member 8. The receptor may be electrically coupled to a lightning current path (e.g. via a conductive cable (not shown)) that directs the current to the ground. In the illustrated example, the lightning receptor is a lightning antenna 31 , but the receptor could be a lightning rod, a lightning array or similar. The lightning antenna 31 is arranged such that any incident lightning strike will attach to the antenna 31 and lightning current will flow along the lightning current path to the ground. The lightning protection system 30 reduces the risk of the blade connecting members 6 and/or pretension members 8 becoming damaged from a lightning strike, since the conductive material 29 is isolated from the lightning protection system 30. The risk of damage to the blade connecting members 6 and/or pre-tension members 8 is therefore reduced, thereby reducing the risk that electrical power supply to the heating element 18 is prevented, and reducing the risk of damaging the structural integrity of the blade connecting members 6 and/or pre-tension members 8.

In some arrangements, the lightning protection system 30 includes a metal mesh or layer (not shown). The metal mesh or layer may be arranged circumferentially around the conductive material 29 of the blade connecting members 6 and/or the pre-tension members 8.

In Figure 6, the lightning protection system 30 includes a lightning discharge filter system 32. The lightning discharge filter system 32 is configured to divert surges that occur during a lightning strike away from key components of the wind turbine 1 , particularly away from the blade connecting members 6 and/or pre-tension members 8. The lightning discharge filter system 32 includes a path to ground (e.g. a low- resistance path). As can be seen, the lightning discharge filter system 32 is housed within the hub 4 in the figures, although it should be appreciated that the lightning discharge filter may be positioned in any suitable location. Housing the lightning discharge filter system 32 in the hub 4 is preferable in protecting the lightning discharge filter system 32 from becoming damaged and ineffective. Moreover, providing the lightning discharge filter system 32 in the hub 4 provides a centralised point of operation for the system 32 in the wind turbine 1 , facilitating simpler access, e.g. for maintenance, and require only one lightning discharge filter system as compared to three when arranging one lightning discharge filter systems in each blade.

The anti-icing system and/or the de-icing system 17 may include one or more sensors 19. The sensors 19 may be provided in or on one or more of the blade connecting members 6 or pre-tension members 8. The sensors 19 may be provided within the respective blade connecting member 6 or pre-tension member 8 (e.g. embedded within the cable) or on an outer surface 34 of the respective blade connecting member 6 or pre-tension member 8. The sensors 19 are configured to detect ice accumulation or a condition in which ice accumulation will occur. The sensors 19 may provide an operator or a control system (not shown) with information regarding the status at the respective blade connecting member 6 or pre-tension member, which will provide information regarding conditions at the blade surface 10. The anti-icing system and/or the de-icing system 17 may be configured such that the electrical heating elements 18 are only operational when the sensors 19 detect ice accumulation or a condition in which ice accumulation will occur. In this way, the energy requirements of the anti-icing system and/or the de-icing system 17 are reduced as the one or more heating elements 18 are only operational when required. The sensor 19 may be an accelerometer, temperature sensor, position sensor, load sensor, strain sensor or combinations thereof. One or more sensors 19 may be arranged in/on the hub, nacelle and/or blades for detecting either ice accumulation or a condition in which ice accumulation will occur. The sensors 19 may be one or more of a liquid water content sensor, ice detection sensor, aero pressure sensor, surface electrical resistance or impedance sensor.

In some examples, one or more sensors 19 are arranged away from the blade connecting member 6 and pre-tension member 8, such as on a part of the blade 5 or on the nacelle 3 or on the hub 4. The anti-icing system and/or the de-icing system 17 may include one or more meteorological sensors (e.g. external to the wind turbine 1) that can detect conditions of the turbine 1.

In Figure 6, only one sensor 19 is provided, but it should be appreciated that any number of sensors 19 may be provided, as will now be discussed with reference to Figures 8 and 9. Figures 8 and 9 are schematic diagrams of the blade connecting members 6 and/or pre-tension members 8 having different sensor arrangements. In the example of Figure 8, a plurality of sensors 19 are provided with the respective blade connecting member 6 or pre-tension member 8. The plurality of sensors 19 are provided in multiple locations along the length of the respective blade connecting member 6 or pre-tension member 8 in the illustrated example. The sensors 19 are evenly distributed across the length of the respective blade connecting member 6 or pre-tension member 8 in Figure 8. The plurality of sensors 19 may not be evenly distributed in some examples. The provision of multiple sensors 19 along the length of the blade connecting member 6 or pre-tension member 8 provides information regarding the state of the blade connecting member 6 or pre-tension member 8 at various positions. This improves the ability of the anti-icing system and/or the de-icing system 17 to only operate when required, e.g. when the conditions at the blade connecting members 6 and/or pre-tension members 8 are sufficient to indicate that the heating element 18 in the blade may be required, thereby reducing wasted energy that may occur if the heating element 18 is operating when ice accumulation is not an issue. Moreover, multiple sensors 19 improves redundancy of the anti-icing system and/or the de-icing system 17, as information can still be obtained from other sensors 19 if a sensor becomes faulty.

Referring to Figure 9, an alternative example blade connecting member 6 or pretension member 8 is illustrated. In this example, a sensor 19 is provided that extends along substantially the entire length of the respective blade connecting member 6 or pre-tension member 8. In this way, information regarding ice accumulation can be obtained across the entire length of a respective blade connecting member 6 or pretension member 8. In some examples, a plurality of sensors 19 extending over the entire length of the blade connecting member 6 or pre-tension member 8 may be provided (e.g. to increase redundancy of the sensor arrangement). A combination of distributed sensors (i.e. as shown in Figure 8) and elongated sensors (i.e. that extend along substantially the entire length of the respective blade connecting member 6 or pre-tension member 8) may be implemented. The sensors 19 may be provided on the outer surface 20 of the blade connecting member 6 or pre-tension member 8, embedded therein, or combinations of both.

It should be appreciated that the sensor arrangements described in relation to Figures

8 and 9 may be applied to any of the examples discussed herein. Referring to Figures 10 to 14, alternative examples of wind turbines 1 and blade connecting members 6 and/or pre-tension members 8 are indicated. The wind turbines 1 and blade connecting members 6 and/or pre-tension members 8 illustrated are similar to those previously described, and so only the differences will be discussed in detail. In these examples, the blade connecting member 6 and/or pre-tension member 8 includes a structural load carrying non-conductive material 33, and the conductive material 29 for transferring electrical power along the power source path 28 between the hub 4 and the heating element 18. In the figures, the blade connecting member 6 and/or pre-tension member 8 includes only the structural load carrying non-conductive material 33 and the conductive material 29, but it should be appreciated that other materials may be present. The structural load carrying non-conductive material 33 may be any material suitable for supporting the blades 5 relative to each other but that does not conduct electricity, e.g. a polymer such as ultra-high molecular weight polyethylene - LIHMWPE. The conductive material 29 may be any material suitable for conducting electrical power, as discussed above. The blade connecting members 6 and/or pretension members 8 of these examples can provide the electrical power between the hub 4 and heating element 18 without being made completely from a conductive material. Non-conductive material is typically more lightweight than conductive material, thereby reducing the weight of the blade connecting members 6 and/or pretension members 8 and rotor loads on the turbine 1 , while still facilitating the convenient routing of the electrical power source path 28 via the blade connecting members 6 and/or pre-tension members 8.

In Figures 10 and 11 , the conductive material 29 is embedded within the non- conductive material 33 of the respective blade connecting member 6 or pre-tension member 8. As can be seen in the cross-sectional view of Figure 11 , the non-conductive material 33 surrounds the conductive material 29 (e.g. completely surrounds or encases the conductive material 29 such that the electrical power source path 28 is surrounded by non-conductive material 33). The conductive material 29 may only be partially encased in some examples. The arrangement of Figures 10 and 11 protects the conductive material 29 and thus the electrical power source path 28 from damage (e.g. from precipitation, dust and debris) and supports the conductive material 29 relative to the blade connecting member 6 or pre-tension member 8 so as to provide power to the heating element 18 without requiring additional components to provide support. An alternative configuration is indicated in the examples of Figure 12. The conductive material is attached to an outer surface 34 of the non-conductive material 33 of the respective blade connecting member 6 or pre-tension member 8. The conductive material 29 may be attached to the outer surface 34 via any suitable means, e.g. a mechanical connection, an adhesive bond, welding, clamping, winding around the non- conductive material (e.g. in a helix-like structure) or combinations thereof. Attaching the conductive material 29 to the outer surface 34 of the non-conductive material 33 provides for convenient access to the conductive material 29.

Figure 13 shows a cross-sectional view of a blade connecting members 6 and/or pretension members 8 in which the conductive material 29 is attached to the outer surface 34 of the non-conductive material 33. In this example, the conductive material 29 is coupled to the blade connecting members 6 and/or pre-tension members 8 outside a profile of the respective blade connecting member 6 or pre-tension member 8. The term “profile” relates to a profile defined by a core element (i.e. the cable or the non- conductive material 33) of the blade connecting member 6 or pre-tension member 8. In Figure 6, the conductive material 29 is coupled outside this profile, i.e. coupled to the outer surface 34. In the figure, the conductive material 29 is secured to the outer surface 34 via a braided sleeve 35. The braided sleeve 35 may envelope the conductive material 29 to the non-conductive material 33 to secure the conductive material 29 relative to the non-conductive material 33. The braided sleeve 35 may be used in combination with any other securing means, or may not be present in some examples.

In the example of Figure 14, the conductive material 29 is coupled to the blade connecting member 6 and/or pre-tension member 8 inside a profile of the respective blade connecting member 6 or pre-tension member 8. In this example, the blade connecting member 6 or pre-tension member 8 includes a recessed region that defines a channel or a hole 36. The channel 36 may be defined in the non-conductive material 33 (i.e. the outer surface 34 of the non-conductive material includes the recessed region). The conductive material 29 is received and supported in the channel 36 (i.e. supported by the non-conductive material 33). The conductive material 29 may be fixedly secured to the channel 36 (e.g. via any of the means noted above), and/or may be press fitted into the channel 36. In some examples, the braided sleeve 35 may additionally or alternatively be provided to secure the conductive material 29 in the channel 36. The anti-icing system and/or the de-icing system 17 has been described as providing protection via various configurations of the blade connecting members 6 and/or pretension members 8. It should be understood that any combination of the above examples may be implemented. For example, different blade connecting members 6 and/or pre-tension members 8 in the wind turbine 1 may include any combination of the features of the examples.

Referring to Figure 15, an example power distribution system 25 is indicated. As previously discussed, the power distribution system 25 includes the power distributor 26 located in the hub 4. The system 25 may also include the lightning discharge filter system 32 located in the hub 4. Electrical power may be supplied to the power distributor 26 from various sources. In the example of Figure 15, power 45 is supplied to the power distributor 26 from a distributed control node 41 in the hub 4. The distributed control node 41 may receive power from a generator in the nacelle 3 or from any source external to the hub 4. The distributed control node 41 may provide a control signal 39 to the power distributor 26 regarding the conditions at or near the blades 5. The distributed control node 41 may be configured to receive data from the sensors 19 and issue the control signal 39 to the power distributor 26 based on this data. For example, if it is determined, based on data from the sensors 19, that ice is likely to be accumulating on a blade 5, the distributed control node 41 may transmit a control signal 39 to the distribution box to begin providing electrical power to the heating elements 18 along the electrical power source path 28 that is routed along the blade connecting members 6 and/or pre-tension members 8. The control signal 39 may also instruct the power distributor 26 to increase the electrical power provided to the heating elements 18 (e.g. to increase the temperature generated at the blade surface 10 by the heating element 18).

The power distributor 26 may also be coupled to the lightning discharge filter system 32 within the hub 4. In this way, in the event of lightning striking the lightning receptor, current 38 from the strike is directed from the lightning receptor to the power distributor 26 (e.g. via a power source path 28 described above), where it is then directed to the lightning discharge filter system 32. The lightning discharge filter system 32 then directs lightning current 37 to ground (e.g. via the nacelle 3 and tower 2) and protecting the power supply to the blade heating elements 18. Locating the power distributor 26, lightning discharge filter system 32 and distributed control node 41 within the hub 4 provides protection to these key components, and reduces the electrical components required (i.e. a separate distribution box and/or discharge filter is not required on each blade connecting members 6 and/or pre-tension members 8 or on each blade), thereby reducing the mechanical load on the wind turbine 1.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims

Claims

1. A pitch controlled wind turbine (1) comprising a tower (2), a nacelle (3) mounted on the tower (2), a hub (4) mounted rotatably on the nacelle (3), and at least three wind turbine blades (5), wherein each wind turbine blade (5) extends between a root end (11) connected to the hub (4) via a pitch mechanism, and a tip end (12); the wind turbine further (1) comprising at least three blade connecting members (6), each blade connecting member (6) extending from a connection point (7a, 7b) on one wind turbine blade (5) towards a connection point (7a, 7b) on a neighbouring wind turbine blade (5), where the connection point (7a, 7b) on a given wind turbine blade (5) is arranged at a distance from the root end (11) and at a distance from the tip end (12) of the wind turbine blade (5); at least three pre-tension members (8), each pre-tension member (8) being connected to one of the blade connecting members (6) and to the hub (4) via a tensioning device (9), the tensioning device (9) provides radial movement of a radially inward end of the pre-tension member (8) with respect to an axis of rotation of the hub (4) due to extension or retraction of the tensioning device (9), each pre-tension member (8) thereby providing pre-tension in the blade connecting member (6) to which it is connected; and an anti-icing system and/or a de-icing system (17) including one or more heating elements (18) for protecting one or more of the wind turbine blades (5), wherein one or more electrical power source paths (28) for the anti-icing system or the de-icing system (17) are routed between the hub (4) and the heating element (18) along at least one of the blade connecting members (6) and pre-tension members (8).

2. The pitch controlled wind turbine (1) according to claim 1 , wherein the blade connecting members (6) and/or the pre-tension members (8) include conductive material (29), and the conductive material (29) is a structural load carrying conductive material for transferring electrical power along the power source path (28) between the hub (4) and the heating element (18).

3. The pitch controlled wind turbine (1) according to claim 1 , wherein the blade connecting members (6) and/or the pre-tension members (8) include structural load carrying non-conductive material (33), and further include conductive material (29) for transferring electrical power along the power source path (28) between the hub (4) and the heating element (18).

4. The pitch controlled wind turbine (1) according to claim 3, wherein the conductive material (29) is embedded within the non-conductive material (33) of the respective blade connecting member (6) or pre-tension member (8).

5. The pitch controlled wind turbine (1) according to claim 3, wherein the conductive material (29) is attached to an outer surface (34) of the non-conductive material (33) of the respective blade connecting member (6) or pre-tension member (8).

6. The pitch controlled wind turbine (1) according to claim 5, wherein the conductive material (29) is coupled to the respective blade connecting member (6) or pre-tension member (8) either inside or outside a profile of the non-conductive material (33) of the respective blade connecting member (6) or pre-tension member (8).

7. The pitch controlled wind turbine (1) according to any one of claims 2 to 6, wherein the blade connecting members (6) and/or the pre-tension members (8) having the conductive material (29) further comprise a lightning protection system (30) configured to isolate the conductive material (39) from lightning current.

8. The pitch controlled wind turbine (1) according to any preceding claim, wherein the electrical power source path (28) provides residual or inherent heat when transferring electrical power along the power source path (28) between the hub (4) and the heating element (18) so as to protect the blade connecting member (6) or pre-tension member (8) from ice accumulation or de-icing (during operation of the heating element (18)).

9. The pitch controlled wind turbine (1) according to any preceding claim, wherein the anti-icing system or de-icing system (17) includes an electrical power distribution system (25) for distributing electrical power to each of the wind turbine blades (5), and wherein the electrical power distribution system (25) includes a power distributer (26) housed within the hub (4).

10. The pitch controlled wind turbine (1) according to any preceding claim, wherein the anti-icing system and/or de-icing system (17) includes one or more sensors (19) in or on one or more of the blade connecting members (6) or the pre-tension members (8) for detecting either ice accumulation or a condition in which ice accumulation will occur.

11. The pitch controlled wind turbine (1) according to claim 10, wherein the sensor (19) is one or more of: an accelerometer, temperature sensor, position sensor, load sensor, liquid water content sensor, ice detection sensor, aero pressure sensor, surface electrical resistance or impedance sensor, or strain sensor.

12. The pitch controlled wind turbine (1) according to claim 10 or claim 11 , wherein the one or more sensors (19) are provided at multiple locations along the length of the blade connecting member (6) or pre-tension member (8), or wherein the one or more sensors (19) are provided along substantially the entire length of the blade connecting member (6) or pre-tension member (8).

13. The pitch controlled wind turbine (1) according to any preceding claim, wherein the anti-icing system or de-icing system (17) includes a lightning protection system (30) including a lightning discharge filter system (32), preferably the lightning discharge filter system (32) is housed within the hub (4).

14. The pitch controlled wind turbine (1) according to any preceding claim, wherein the blade connecting members (6) and/or the pre-tension members (8) comprise at least one bearing (50), the at least one bearing (50) located at or towards a terminal end of the respective blade connecting member (6) and/or pre-tension member (8), wherein the bearing (50) is non-conductive, and wherein the electrical power source path (28) is decoupled from a respective blade connecting member (6) and/or pre-tension member (8) so as to be diverted around the at least one bearing (50).

15. The pitch controlled wind turbine (1) according to claim 14, wherein each wind turbine blade (5) comprises a leading edge (13), a leading edge extension (49), and a blade shell (53), wherein the leading edge extension (49) extends forward of the leading edge (13), and the connection point (7a, 7b) of the respective wind turbine blade (5) is located forward of the leading edge (13) on the leading edge extension (49), and each wind turbine blade (5) further comprises a respective fairing (20) extending over at least the leading edge extension (49), and wherein the electrical power source path (28) is decoupled from a respective blade connecting member and diverted around the bearing (50) within the fairing (20).