Wind turbine ice protection

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 pretension members, each 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 / retraction of the tensioning device, each pre-tension member thereby providing pre-tension in the blade connecting member to which it is connected. An anti-icing system and / or a de-icing system is provided for protecting one or more of the blade connecting members, the pre-tension members, the connection points, or the tensioning devices.

Description

[0001] WIND TURBINE ICE PROTECTION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a pitch controlled wind turbine having an anti-icing and / or a de-icing system.

[0004] BACKGROUND OF THE INVENTION

[0005] Wind turbines are often deployed in regions where cold temperatures and adverse weather conditions occur, leading to the formation of ice on various parts of the turbine structure.

[0006] The accumulation of ice on wind turbine components poses several significant challenges. First, the overall weight of the turbine can increase, potentially causing imbalances and mechanical stress on critical components, and aerodynamic impacts which can result in reduced efficiency and costly maintenance. Furthermore, ice throw 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 ice build-up, which if not mitigated could result in a reduction in performance and structural integrity of the wind turbine.

[0007] 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.

[0008] SUMMARY OF THE INVENTION

[0009] 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 for protecting one or more of the blade connecting members, the pre-tension members, the connection points, or the tensioning devices.

[0010] The provision of an anti-icing system and / or de-icing system can protect essential components 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 such components helps avoid issues such as increased mechanical stress, reduced power generation efficiency, potential damage from ice throw, and increased downtime and maintenance as well.

[0011] The anti-icing system and / or de-icing system may include one or more electrical heating elements.

[0012] 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 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.

[0013] 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.

[0014] 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.

[0015] 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%.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] The actuator may be a linear actuator, such as a hydraulic actuator, an electrical actuator or a mechanical actuator. The actuator may have a cylinder and a rod moveable into and out of the cylinder. The first portion of the actuator may include the cylinder, and the second portion of the actuator may include the rod.

[0021] The actuator may be a rotary actuator. The actuator may comprise a motor and a tension element, wherein a radially distal end of the tension element is connected to the radially inward end the pre-tension member, and a radially inward end of the tension element is wound around a drum connected to a rotatable shaft of the motor. The first portion of the actuator may include the motor, and the second portion of the actuator may include the tension element.

[0022] The electrical heating element may be embedded within the respective blade connecting member or pre-tension member.

[0023] Embedding the electrical heating element protects the electrical heating element against damage (e.g. from precipitation, dust and debris), reducing the risk of the electrical heating element becoming damaged. Moreover, embedding the electrical heating element provides for a convenient means of positioning and supporting the anti-icing system and / or de-icing system relative to the other components of the wind turbine, reducing the space and components required for the anti-icing system and / or de-icing system. Specifically, the electrical heating element 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.

[0024] The electrical heating element may be attached to an outer surface of the respective blade connecting member or pre-tension member.

[0025] Attaching the electrical heating element in this way provides for a convenient means of positioning and supporting the anti-icing system and / or de-icing system relative to the other components of the wind turbine, reducing the space and components required for the anti-icing system and / or de-icing system. Moreover, the electrical heating element can be easily removed / replaced by simply detaching the electrical heating element from the outer surface.

[0026] The electrical heating element may be coupled to the respective blade connecting member and / or pre-tension member either inside or outside a profile of the respective blade connecting member and / or pre-tension member.

[0027] It should be understood that the term “profile” relates to a profile defined by a core element of the respective blade connecting member or pre-tension 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 electrical heating may be coupled (i.e. coupled inside a profile). Alternatively, the electrical heating element may be coupled to the outer surface (i.e. the outer profile) of the respective blade connecting member or pre-tension member.

[0028] Coupling the electrical heating element in such a way provides for a secure and convenient means of providing the electrical heating element to component parts of the wind turbine, making use of the respective profile of the respective blade connecting member or pre-tension member.

[0029] 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 further comprises a respective fairing extending over at least the leading edge extension, and wherein the anti-icing system and / or de-icing system is for protecting the fairing.

[0030] The leading edge extension may be integrally formed with the connector. The fairing may cover the connection joint. The fairing may be secured to the connector. The connector may extend outside the profile of the blade shell at the connection joint. This may improve the load transfer across the connection joint but may require a larger fairing.

[0031] 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. The connection points of the one of the wind turbine blades may be adjacent each other on the same leading edge extension. Each blade connecting member may be independently moveable at the respective first and second connection points to which it attaches. The connection point(s) may comprise a bearing structure.

[0032] The fairing is an important component in improving aerodynamic performance of the wind turbine blade compared to a wind turbine blade having a leading edge extension coupled to the blade connecting member but with no fairing extending over the leading edge extension. As such, protecting such an important component from the effects of ice accumulation is important in maintaining the aerodynamic performance of the wind turbine blades.

[0033] The fairing may include one or more electrical heating elements.

[0034] As noted above, electrical heating elements are a convenient and efficient means of preventing and removing ice build-up from a component. Including an electrical heating element in the fairing further reduces the risk of ice build-up on the outer surface of the fairing, and thus reduces the risk of a reduction in aerodynamic performance of a blade.

[0035] The fairing may include a heating mat integrated into fibre material of a shell of the fairing.

[0036] Advantageously, integrating a heating mat into the shell of the fairing provides the electrical heating element without increasing the space occupied by the fairing (e.g. by having a heating element on the outer surface of the fairing), thus improving aerodynamic performance of the blade. Moreover, the integrated heating mat is less susceptible to damage and can distribute heat to the fairing from the inside, reducing the formation of ice on the fairing.

[0037] The tensioning devices may be coupled to a projection extending forward of the hub in an upwind direction of the wind turbine, a spinner coupled to the hub covers a radially inner portion of each tensioning device, and preferably wherein the anti-icing system and / or de-icing system is for protecting the spinner.

[0038] The spinner provides cover and protection to the radially inner portion of each tensioning device. As such, protecting the spinner from ice build-up is important in maintaining the functionality of essential parts to the pitch controlled wind turbine.

[0039] The spinner may include one or more electrical heating elements.

[0040] Including an electrical heating element in the spinner further reduces the risk of ice build-up on the outer surface of the spinner, and thus reduces the risk of damage to the tensioning devices. The one or more electrical heating elements may be a heating mat integrated into fibre material of a shell of the spinner.

[0041] Integrating a heating mat into the shell of the spinner provides the electrical heating element without increasing the space occupied by the spinner (e.g. by having a heating element on a surface of the spinner). Moreover, the integrated heating mat is less susceptible to damage and can distribute heat to the spinner from within the spinner, further reducing the formation of ice on the spinner.

[0042] The blade connecting member may be formed as a first connecting member portion extending from the connection point on the one wind turbine blade to a connector device, and a second connecting member portion extending from the connector device to the connection point on the neighbouring wind turbine blade. The respective pretension member may be connected to the blade connecting member via the connector device, and preferably wherein the anti-icing system and / or de-icing system is for protecting the connector device.

[0043] The connector device importantly supports the blade connecting members and pretension members relative to each other, thereby providing important additional support to the blades of the wind turbine. In this way, protecting the connector device from the effects of ice build-up is important in facilitating continued support to the connecting members and pre-tension members.

[0044] The anti-icing system and / or de-icing system may include an ice-phobic coating material.

[0045] The provision of an ice-phobic coating material has been found to assist in preventing the build-up of ice, reducing the requirements of the anti-icing system and / or de-icing system to remove ice that has accumulated. In this way, energy requirements of the anti-icing system and / or de-icing system are reduced, while the component parts of the wind turbine are effectively protected.

[0046] The anti-icing system and / or 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 condition in which ice accumulation will occur. The provision of a sensor can provide improved control to the anti-icing system and / or de-icing system, and can provide up-to-date information to an operator regarding the status on the blade connecting members or pre-tension members. The energy requirements of the anti-icing system and / or de-icing system may be reduced, in that the respective system only operates when required (e.g. when a predetermined amount of ice has accumulated, or when weather conditions suggest ice will begin to accumulate), and is not continuously operating.

[0047] The sensor may be one or more of: an accelerometer, temperature sensor, position sensor, load sensor or strain sensor.

[0048] The one or more sensors may be provided at multiple locations along the length of the blade connecting member or pre-tension member.

[0049] The one or more sensors may be provided along substantially the entire length of the blade connecting member or pre-tension member.

[0050] 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 operating regarding the state of the member in various positions. In this way, the anti-icing system and / or de-icing system may only be required to operate in a given position along the length of the blade connecting member or pre-tension member, reducing wasted energy where the anti- icing system and / or de-icing system is operational when not needed.

[0051] Providing multiple sensors improves 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.

[0052] 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.

[0053] 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.

[0054] The wind turbine may be an upwind wind turbine.

[0055] The anti-icing system and / or de-icing system may include a fluid heating system.

[0056] A fluid heating system is an effective means of providing heat to remove ice and / or prevent its build-up. The provision of a fluid heating system provides an alternative to electrical (resistance) heating and may provide advantages in avoiding the need for lightning strike protection of one or more parts of the anti-icing system and / or de-icing system.

[0057] The anti-icing system and / or de-icing system may comprise a lightning protection system configured to protect one or more of the blade connecting members, the pretension members, the connection points, or the tensioning devices from lightning current.

[0058] The lightning protection system may be configured to isolate one or more electrical heating elements of the anti-icing system and / or de-icing system from lightning current.

[0059] Advantageously, the risk of wind turbine components becoming damaged from a lightning strike is reduced as the lightning protection system will isolate the components from lightning current. In this way, the risk of the components becoming damaged by a lightning strike is reduced. As such, maintenance requirements of the wind turbine are reduced.

[0060] BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0062] Figure 1 shows a front view of a wind turbine according to a first example;

[0063] Figure 2 shows a side view of the wind turbine;

[0064] Figure 3 shows a blade connecting member or pre-tension member according to a first example; Figure 4 shows a schematic of a blade connecting member or pre-tension member according to a second example;

[0065] Figure 5 shows a cross-sectional view of a blade connecting member or pre-tension member according to a fourth example;

[0066] Figure 6 shows a cross-sectional view of a blade connecting member or pre-tension member according to a fifth example;

[0067] Figure 7 shows a cross-sectional view of a blade connecting member or pre-tension member according to a sixth example;

[0068] Figure 8 shows a wind turbine blade;

[0069] Figure 9 shows an exploded view of a connection joint;

[0070] Figure 10 shows a turbine blade having a fairing;

[0071] Figure 11A shows a cross-sectional view of a wind turbine blade having a fairing, a connector and two blade portions;

[0072] Figure 11 B shows a schematic cross-sectional view of a fairing;

[0073] Figure 12A shows a partially side view of components of an anti-icing system and / or a de-icing system adjacent the hub of a wind turbine;

[0074] Figure 12B shows a schematic cross-sectional view of a spinner;

[0075] Figure 13 shows a portion of a wind turbine according to another example.

[0076] DETAILED DESCRIPTION OF EMBODIMENT(S)

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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 comprise a bearing structure.

[0092] A pre-tension member 8 extends between one of each of the blade connecting members 6 and a common point 25 (see Figure 12A) arranged at or adjacent the hub 4. In the example shown in Figures 1 and 2, 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.

[0093] The pre-tension members 8 are coupled 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 10 (see Figure 12A) 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.

[0094] The wind turbine 1 may include at least one connector device 43 for each blade 5. The connector device 43 may be provided to support the connection between a blade connection member 6 and a pre-tension member 8 for tensioning the blade connection member 6, such as shown in Figure 1. The connector device 43 may not be present in some examples. The blade connecting members 6 may be formed as a first connecting member portion 6a extending from the connection point 7a, 7b of one blade 5 to the connector device 43, and a second connecting member portion 6b extending from the connector device 43 to the connection point on the neighbouring blade 5. The respective pre-tension member 8 may be connected to the blade connecting member 6 via the connector device 43.

[0095] The wind turbine blades 5 have a root end 11 proximal to the hub 4, adapted to be connected to the hub 4 via a pitch mechanism 50 (see Figure 12A), and 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. Each of the blades 5 include a suction side 15 and a pressure side 16. A thickness dimension of the blade 5 extends between the suction side 15 and the pressure side 16.

[0096] 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.

[0097] The wind turbine 1 includes an anti-icing system and / or de-icing system 17. The provision of an anti-icing system and / or de-icing system can protect essential components of the pitch controlled wind turbine having blade load sharing connecting members from the accumulation of ice. Reducing or preventing ice build-up on such components helps avoid issues such as increased mechanical stress, reduced power generation efficiency, potential damage from ice throw, and increased downtime and maintenance as well. 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.

[0098] The anti-icing system and / or de-icing system 17 is configured for protecting one or more of the blade connecting members 6, the pre-tension members 8, the connection points 7a, 7b, or the tensioning devices 9. The anti-icing system may be configured to prevent or reduce ice accumulation on a given component of the wind turbine 1. The de-icing system may be configured to remove or reduce ice accumulation on a given component of the wind turbine 1. Preventing or reducing ice build-up on components of the wind turbine 1 avoids an increase in mechanical stress acting on the wind turbine 1 , as well as preventing a reduction in power generation efficiency.

[0099] Examples of the anti-icing system and / or de-icing system 17 are shown in Figures 3 to 13. The anti-icing system and / or de-icing system 17 may include one or more electrical heating elements 18. The electrical heating element 18 may be of any suitable kind, for example the electrical 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 electrical heating element 18 is configured to melt ice and / or prevent its build-up on a surface of a blade load sharing component of the wind turbine (e.g. by heating an outer surface of a component to a temperature at which ice formation and / or accumulation is prevented). Electrical heating elements 18 provide for a precise, efficient, and controlled temperature increase so as to melt ice, evaporate water and / or prevent ice build-up.

[0100] The anti-icing system and / or de-icing system 17 as discussed in relation to the below examples may include an ice-phobic coating material, e.g. arranged to at least partially coat an outer surface of a component the anti-icing system and / or de-icing system 17 is intended to protect. The ice-phobic coating may be configured to prevent ice buildup on a surface, e.g. by reducing the adhesion of ice and frost to surfaces. The icephobic coating may be any suitable coating, e.g. a hydrophobic coating, a fluoropolymer-based coating, a silicone-based coating, a polyurethane-based coating, or the like. The ice-phobic coating may be provided in addition to or as an alternative to the electrical heating elements 18. The provision of an ice-phobic coating material may reduce the energy requirements of the anti-icing system and / or de-icing system 17 as ice build-up is reduced, requiring less energy from the electrical heating elements

[0101] 18 to melt ice or prevent its build-up.

[0102] 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 form part of the anti-icing system and / or de-icing system 17, as will be discussed below.

[0103] Figures 3 to 7 schematically indicate an example blade connecting member 6 or a pretension member 8 (i.e. a cable that could serve either function). As can be seen, the heating element 18 is provided with the respective blade connecting member 6 or pretension member 8. As will be discussed below, the heating element 18 is provided with the respective blade connecting member 6 or pre-tension member 8 so as to provide heat to an outer surface 20 of the blade connecting member 6 or pre-tension member 8 such that ice thereon is melted and thus removed from the surface 20 as a liquid or vapour. The heating element 18 may be provided embedded, attached, or otherwise secured or coupled with / to a respective blade connecting member 6 or pre-tension member 8. In the examples of Figures 3 and 4, only one electrical heating element 18 is provided in a central region of the blade connecting member 6 or pre-tension member 8. It should be understood that any number of heating elements 18 may be provided at any location of the blade connecting member 6 or pre-tension member 8. In some examples, an electrical heating element 18 may be provided that extends along the entire length of the respective blade connecting member 6 or pre-tension member 8. An electrical heating element 18 may be provided to the blade connecting member(s) 6 and the pre-tension member(s) 8 in some examples.

[0104] The anti-icing system and / or de-icing system 17 may include a lightning protection system 45 configured to protect one or more of the blade connecting members 6, the pre-tension members 8, the connection points 7a, 7b, the tensioning devices 9, or the electrical heating elements 18 from lightning current. The lightning protection system 45 may be configured to isolate one or more components of the wind turbine 1 from lightning current. The lightning protection system 45 may couple one or more of the blade connecting members 6, the pre-tension members 8, the connection points 7a, 7b, the tensioning devices 9, or the electrical heating elements 18 to ground (e.g. via the hub 4, through the nacelle 3 and tower 2, to ground). The lightning protection system 45 may be configured to protect wind turbine components in case of direct or indirect lightning attachment. The lightning protection system 45 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 46, but the receptor could be a lightning rod, a lightning array or similar. The lightning antenna 46 is arranged such that any incident lightning strike will attach to the antenna 46 and lightning current will flow along the lightning current path to the ground. Although not illustrated, it should be appreciated that a lightning receptor may be positioned in any suitable position to protect wind turbine 1 components. In some arrangements, multiple lightning receptors are provided in various positions about the wind turbine 1.

[0105] The lightning protection system 45 reduces the risk of wind turbine 1 components becoming damaged from a lightning strike, since components of the turbine 1 are isolated from the lightning protection system 45. The risk of damage to components 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 components, e.g. the blade connecting members 6 and / or pre-tension members 8. The anti-icing system and / or de-icing system 17 may include one or more sensors 19. The sensors 19 may be provided within the blade connecting member 6 or pre-tension member 8 (e.g. embedded within the cable) or on an outer surface 20 of the respective blade connecting member 6 or pre-tension member 8. In some examples the sensor is arranged away from the blade connecting member 6 and pre-tension member 8, such as on a part of the blade or on the nacelle. The sensors 19 may be 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 8 or on other components of the wind turbine 1. The anti-icing system and / or 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 de-icing system 17 may be reduced as the one or more heating elements 18 may only be operational when required. In another embodiment, the anti-icing system and / or deicing system 17 may be configured such that the sensor furthermore or alternatively provides an operator or a control system (not shown) with information regarding safety aspects of the blade connecting member 6 and / or the pre-tension member 8, such as for example (change in) creep rate, or overheating and thereby prevents or reduces the risk of breakage of the blade connecting member 6 and / or the pre-tension member 8. The sensor 19 may be an accelerometer, temperature sensor, position sensor, load sensor, strain sensor or combinations thereof. A plurality of sensors 19 may be provided with the respective blade connecting member 6 or pre-tension member 8, e.g. as shown in figure 3. The plurality of sensors 19 may be provided in multiple locations along the length of the respective blade connecting member 6 or pre-tension member 8. The sensors 19 may be evenly distributed across the length of the respective blade connecting member 6 or pre-tension member 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 may provide information regarding the state of the blade connecting member 6 or pre-tension member 8 at various positions. This allows the anti-icing system and / or de-icing system 17 to only operate in a required area along the length of the respective blade connecting member 6 or pre-tension member 8, reducing wasted energy that may occur if the heating element 18 is operating in an area where ice accumulation is not an issue. Moreover, multiple sensors 19 improve redundancy of the anti-icing system and / or de-icing system 17, as information can still be obtained from other sensors 19 if a sensor becomes faulty.

[0106] A sensor 19 may alternatively be provided that extends along substantially the entire length of the respective blade connecting member 6 or pre-tension member 8, e.g. as shown in figure 4. In this way, information regarding ice accumulation can be obtained across the entire length of a respective blade connecting member 6 or pre-tension member s. 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 anti-icing system and / or de-icing system 17). A combination of distributed sensors (i.e. as shown in Figure 3) 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.

[0107] The electrical heating element 18 may be embedded within the respective blade connecting member 6 or pre-tension member 8, e.g. as shown in figure 5. The respective blade connecting member 6 or pre-tension member 8 (i.e. the cable material) may surround the electrical heating element 18. The heating element 18 may only be partially surrounded in some examples. This arrangement may protect the electrical heating element 18 from damage (e.g. from precipitation, dust and debris) and supports the electrical heating element 18 relative to the blade connecting member 6 or pre-tension member 8 so as to provide heat to the surface 20 of the blade connecting member 6 or pre-tension member 8 without requiring additional components to provide support.

[0108] The electrical heating element 18 may be attached to the outer surface 20 of the respective blade connecting member 6 or pre-tension member 8, e.g. as shown in Figures 6 and 7. The electrical heating element 18 may be attached to the outer surface 20 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. In one example, the electrical heating element 18 may be secured to the respective blade connecting member 6 or pre-tension member 8 via an over-braiding arrangement (not shown) that extends around an outer surface of the blade connecting member 6 or pre-tension member 8 and the heating element 8 positioned externally to the blade connecting member 6 or pre-tension member 8.

[0109] The electrical heating element 18 may be coupled outside a profile of the respective blade connecting member 6 or pre-tension member 8, e.g. as shown in figure 6. The term “profile” relates to a profile defined by a core element (i.e. the tension carrying member, such as a cable) of the blade connecting member 6 or pre-tension member 8. In Figure 6, the electrical heating element is coupled outside this profile, i.e. coupled to the outer surface 20. This may for example be via a socket or another fixation means or by winding the electrical heating element 18 around the connecting member or pretension member 8.

[0110] Over the lifetime of operation, the connecting member 6 and pre-tension member 8 may creep slightly, and it is preferred that the electrical heating element 18 is arranged helically with a large pitch around the connecting member 6 and pre-tension member 8 or in another way is prepared for some length change over time.

[0111] In the example of Figure 7, the electrical heating element 18 is coupled inside a profile of the respective blade connecting member 6 or pre-tension member s. In this example, the outer surface 20 of the blade connecting member 6 or pre-tension member 8 includes a recessed region that defines a channel or a hole 22. The electrical heating element 18 is received and supported in the channel 22 (i.e. supported by the cable). The electrical heating element 18 may be fixedly secured to the channel 22 (e.g. via any of the means noted above), and / or may be press fitted into the channel 22.

[0112] The anti-icing system and / or de-icing system 17 may be configured to protect other components of the wind turbine 1 from the effects of ice accumulation in addition or alternatively to protecting the blade connecting member 6 or pre-tension member 8, as will now be discussed in more detail.

[0113] In one example, the anti-icing system and / or de-icing system 17 may be configured to protect blade load sharing components of the wind turbine 1 forming part of the wind turbine blade 5. An example of a wind turbine blade 5 is shown in Figure 8. The blades 5 include a suction side 15 and a pressure side 16. 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 comprise 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.

[0114] 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 52 that defines a respective leading edge 30a, 30b, trailing edge 32a, 32b, suction side 34a, 34b, and pressure side 36a, 36b.

[0115] 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. 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

[0116] 12 without any connection joint.

[0117] The split blade 5 may include a bolted connection in some examples. An example connection between the inboard and outboard blade portions 23, 24 is indicated in Figure 9. The blade portions 23, 24 are coupled by a connection joint that includes a connector 41. The connector 41 connects a first blade end surface 26 of the inboard blade portion 23 to a second blade end surface 27 of the outboard blade portion 24. The connector 41 is adapted to transfer load between the inboard blade portion 23 and the outboard blade portion 24. In particular, the connector 41 may be adapted to transfer load between a first spar cap portion 55 (see Figure 11 A) of the inboard blade portion 23 and a second spar cap portion 56 of the outboard blade portion 24. The connector 41 may be arranged to transfer load from the blade connecting members 6 into the spar cap portion 55 of the inboard blade portion 23.

[0118] The connector 41 may be a metallic component, preferably a cast component or a machined component. The connector 41 may be a composite component. The connector 41 may be a co-cured or co-bonded component. As explained in further detail below, the connection points 7a, 7b of the connecting members 6 may be on the connector 41 at the connection joint.

[0119] A leading edge extension 42 may extend forward of the leading edge 13 of the blade 5. The leading edge extension 42 may be integrally formed with the connector 41 , although it will be appreciated that in alternative examples the leading edge extension 42 may be a separate component to the connector 41. The leading edge extension 42 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

[0120] 13 and adjacent the pressure side 16, such as shown in Figure 9. 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 wind turbine blade 5 may have a fairing 44 extending over at least the leading edge extension 42, such as shown in figures 10 and 11A. The fairing 44 may be secured to the connector 41 . In some examples, the connector 41 may extend outside the profile of the blade shell 52 at the connection joint. This may improve the load transfer across the joint, but may require a larger fairing 44. With a split blade, the fairing 44 may span the gap between the two blade sections 23, 24 connected by the connector 41 (or any other form of connection). The fairing 44 may extend over the leading edge extension 42 and the connector 41. As shown in Figure 11 A, the fairing 44 may be sealed to the blade shell 52 by any suitable means, such as a sealant 46.

[0121] The fairing 44 is important in improving aerodynamic performance of a split wind turbine blade 5, i.e. compared to a blade 5 having a leading edge extension 42 coupled to the blade connecting member 6 with no fairing 44. The anti-icing system and / or deicing system 17 may be for protecting the fairing 44 in some examples. Protecting the fairing from the effects of ice accumulation is important in maintaining the aerodynamic performance of the blades 5. Moreover, protecting the fairing 44 may provide ice protection to the connection points 7a, 7b which are covered by the fairing.

[0122] The fairing 44 may include one or more electrical heating elements 18 in some examples, e.g. as shown in figure 10. The electrical heating element(s) 18 provided to the fairing 44 may be substantially the same as that discussed in relation to the blade connecting member 6 or pre-tension member 8. The electrical heating element(s) 18 may be provided embedded in the fairing 44 or otherwise attached to a surface of the fairing 44. The electrical heating element 18 may be integrated into the fairing 44. Although only one heating element 18 is indicated in Figure 10, it should be appreciated that any number of heating elements 18 may be provided within and / or on the fairing 44. The heating element 18 is not shown in Figure 11A for purposes of clarity.

[0123] Figure 11 B shows a cross-sectional view of the fairing 44. In this example, the fairing 44 is formed from a laminate layup process and so includes a shell 48 of fibre material. In this example, the electrical heating element 18 is integrated into the fibre material of the shell 48. The electrical heating element 18 may be a heating mat that is integrated with the fibre material. The fibre material may be fibre glass or any suitable material. Integrating the heating element 18 in this way provides heat to the fairing 44 without increasing the space occupied by the fairing 44 (i.e. by having a heating element 18 on an outer surface of the fairing 44), thus improving aerodynamic performance of the blade 5 having the fairing 44. Moreover, the integrated heating element 18 is less susceptible to damage when integrated within the fairing 44.

[0124] The tensioning devices 9 may also be susceptible to ice accumulation. Referring to Figure 12A, the anti-icing system and / or de-icing system 17 may additionally or alternatively be configured to protect the tensioning devices 9. The hub 4 may comprise a hub member 57 extending from the hub substantially along a direction defined by a rotational axis of the hub 10. The pre-tension members 8 may be connected to the hub member 57.

[0125] The tensioning device 9 may include an actuator 51 having a first portion 53 coupled to the hub 4 and a second portion 54 movable with respect to the first portion 53 and coupled to the respective pre-tension member 8. The tensioning device 9 extends and retracts by movement of the second portion 54 with respect to the first portion 53. Extension and retraction of the tensioning device 9 changes the tension in pre-tension member 8.

[0126] The actuator 51 may be a linear actuator having a cylinder and a rod moveable into and out of the cylinder. The actuator 51 may be hydraulic or electro-mechanical, for example. The cylinder may be the first portion 53 and the rod may be the second portion 54.

[0127] The actuator 51 may be a rotary actuator. Although not shown, the actuator 51 may include a motor and a tension element, wherein a radially distal end of the tension element is connected to the radially inward end the pre-tension member 8, and a radially inward end of the tension element is wound around a drum connected to a rotatable shaft of the motor. The first portion 53 of the actuator 51 may include the motor, and the second portion 54 of the actuator 51 may include the tension element.

[0128] The anti-icing system and / or de-icing system 17 may include at least one electrical heating element 18 in or on the tensioning device(s) 9, e.g. as shown in figure 12A. The electrical heating element 18 may be identical to that described in relation to the blade connecting member 6 or pre-tension member 8 and so will not be discussed here in detail, but it should be understood that the electrical heating element 18 is configured to provide heat to an outer surface of the tensioning device 9 so as to prevent or reduce ice build-up thereon. The electrical heating element 18 is provided on the first portion 52 of the actuator 51 , but it should be appreciated that the electrical heating element(s) 18 may be provided at any location of the tensioning device 9.

[0129] As previously discussed, the tensioning devices 9 are connected at a radial inner end thereof to the common region or point 25. The common point 25 may provide a pivotal connection to each of the tensioning devices 18. In Figure 12A, the common point 25 is on a projection 37 extending forward of the hub 4 in an upwind direction of the wind turbine 1. The projection 37 may be a framework or structure rigidly coupled to the hub 4. A spinner 29 may be coupled to the hub to cover a radially inner portion of each tensioning device 9 The spinner 29 may shroud the common point 25. In this way, the spinner 29 can be seen as an important component in providing protection to the radially inner portion of each tensioning device 9.

[0130] In some examples, the anti-icing system and / or de-icing system 17 may be configured to protect the spinner 29 (e.g. from the build-up of ice thereon). The anti-icing system and / or de-icing system 17 may include at least one electrical heating element 18 in or on the spinner 29. The electrical heating element 18 may be similar to that described in relation to the blade connecting member 6 or pre-tension member 8, but it should be understood that the electrical heating element 18 may be configured to provide heat to an outer surface of the spinner 29 so as to prevent or reduce ice build-up thereon.

[0131] A cross-sectional schematic view of an example spinner 29 is indicated in Figure 12B. The electrical heating element 18 may be integrated with an outer shell 38 of the spinner 29. The spinner 29 may be formed from a laminate layup process and so the spinner shell 38 may be formed from a layup of fibre material. The electrical heating element 18 may be integrated into the fibre material of the shell 38. The electrical heating element 18 may be a heating mat that is integrated with the fibre material. The fibre material may be fibre glass or any suitable material. Integrating the heating element 18 in this way provides heat to the spinner 29 without increasing the space occupied by the spinner 29. Moreover, the integrated heating element 18 is less susceptible to damage when integrated within the spinner 29.

[0132] The anti-icing system and / or de-icing system 17 may additionally or alternatively be configured to protect one or more of the connector devices 43. Figure 13 indicates a section of an example wind turbine 1 having connector devices 43. The anti-icing system and / or de-icing system 17 may include at least one electrical heating element 18 in or on a respective connector device. The electrical heating element 18 may be similar to those described previously, but it should be understood that the electrical heating element 18 may be configured to provide heat to an outer surface of the connector device 43 so as to prevent or reduce ice build-up thereon.

[0133] The anti-icing system and / or de-icing system 17 has been described as providing protection to various components of the blade load sharing components of the wind turbine 1 . It should be understood that any combination of the above examples may be implemented. Any of the arrangements of anti-icing system and / or de-icing system 17 may include sensors 19 that may be substantially identical to the sensors described in relation to the blade connecting members 6 or pre-tension members 8.

[0134] The electrical connection to one or more of the anti-icing and / or de-icing system 17 components may beneficially be routed from the blade 5 to the blade connecting member 6 and then back again into the blade 5. In other versions the electrical connection may be routed from the hub 4 along the pre-tension member 8 and further into the blade connecting member 6. These and other examples of providing electrical power to the anti-icing and / or de-icing system 17 will be appreciated.

[0135] Not all parts of the blade load sharing components of the wind turbine 1 may need ice protection by the anti-icing and / or de-icing system 17. For example, only the connector fairing 44 and / or the connection points 7a, 7b and the outboard parts of the blade connecting members 6 may be protected. It is known that the outboard parts of the wind turbine rotor are typically more susceptible to ice build-up due to the higher rotational speeds there. In another example, the entire length of the blade connecting members 6 may also be protected. In a further example, the pre-tension members 8 may also be protected. In a yet further example, the spinner 29 and / or hub 4 may also be protected.

[0136] Whilst electrical heating may be a preferred form of heating for the anti-icing and / or deicing system 17, it is also contemplated that the components of the wind turbine blade load sharing that require heating may be heated by a fluid heating system. The fluid heating system may transfer heat energy from a working fluid to a component of the wind turbine blade loading sharing system that requires heating as part of the anti-icing and / or de-icing system 17. The working fluid may circulate, e.g. by pumping, to transfer heat energy from a heat source to the component. An advantage of a fluid heating system over an electrical heating system is that the working fluid and a conduit for conveying the working fluid may be made of non-electrically conductive materials and which are therefore not susceptible to lightning strikes. This may avoid the cost and weight of lightning strike protection for at least some parts of the anti-icing and / or deicing system 17. Examples of working fluid for a fluid heating system are gas, such as dried air; ethylene glycol; ethylene glycol-water mixtures; and salt water.

[0137] It will be understood that any references herein to the electrical heating element 18 may also be applicable to a fluid heating system. In this way, the electrical heating element 18 of the figures may be replaced or present in combination with a fluid heating system, e.g. the electrical heating element 18 may be replaced with or utilised in combination with one or more flexible pipes for carrying the working fluid. 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

CLAIMS1. 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 (50), and a tip end (12); the wind turbine (1) further 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 (10) 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) for protecting one or more of the blade connecting members (6), the pre-tension members (8), the connection points (7a, 7b), or the tensioning devices (9).

2. The pitch controlled wind turbine (1) according to claim 1 , wherein the anti-icing system and / or de-icing system (17) includes one or more electrical heating elements (18).

3. The pitch controlled wind turbine (1) according to claim 2, wherein the electrical heating element (18) is embedded within the respective blade connecting member (6) or pre-tension member (8).

4. The pitch controlled wind turbine (1) according to claim 2, wherein the electrical heating element (18) is attached to an outer surface (20) of the respective blade connecting member (6) or pre-tension member (8).

5. The pitch controlled wind turbine (1) according to claim 4, wherein the electrical heating element (18) is coupled to the respective blade connecting member (6) or pretension member (8) either inside or outside a profile of the respective blade connecting member (6) or pre-tension member (8).

6. The pitch controlled wind turbine (1) according to any preceding claim, wherein each wind turbine blade (5) comprises a leading edge (13), a leading edge extension (42), and a blade shell (52), wherein the leading edge extension (42) 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 (42), and each wind turbine blade (5) further comprises a respective fairing (44) extending over at least the leading edge extension (42), and wherein the anti-icing system and / or de-icing system (17) is for protecting the fairing (44).

7. The pitch controlled wind turbine (1) according to claim 6, wherein the fairing (44) includes one or more electrical heating elements (18), preferably a heating mat integrated into fibre material of a shell (48) of the fairing (44).

8. The pitch controlled wind turbine (1) according to any preceding claim, wherein the tensioning devices (9) are coupled to a projection (37) extending forward of the hub (4) in an upwind direction of the wind turbine (1), a spinner (29) coupled to the hub (4) covers a radially inner portion of each tensioning device (9), and preferably wherein the anti-icing system and / or de-icing system (17) is for protecting the spinner (29).

9. The pitch controlled wind turbine (1) according to claim 8, wherein the spinner (29) includes one or more electrical heating elements (18), preferably a heating mat integrated into fibre material of a shell (38) of the spinner (29).

10. The pitch controlled wind turbine (1) according to any preceding claim, wherein the blade connecting member (6) is formed as a first connecting member portion (6a) extending from the connection point (7a, 7b) on the one wind turbine blade (5) to a connector device (43), and a second connecting member portion (6b) extending from the connector device (43) to the connection point (7a, 7b) on the neighbouring wind turbine blade (5), and wherein the respective pre-tension member (8) is connected to the blade connecting member (6) via the connector device (43), and preferably whereinthe anti-icing system and / or de-icing system (17) is for protecting the connector device (43).11 . The pitch controlled wind turbine (1) according to any preceding claim, wherein the anti-icing system and / or de-icing system (17) includes an ice-phobic coating material.

12. 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 condition in which ice accumulation will occur.

13. The pitch controlled wind turbine (1) according to claim 12, wherein the sensor (19) is one or more of: an accelerometer, temperature sensor, position sensor, load sensor or strain sensor.

14. The pitch controlled wind turbine (1) according to claim 12 or claim 13, 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).

15. The pitch controlled wind turbine (1) according to any preceding claim, wherein the anti-icing system and / or de-icing system (17) includes a fluid heating system.

16. The pitch controlled wind turbine (1) according to any preceding claim, wherein the anti-icing system and / or de-icing system (17) comprises a lightning protection system (45) configured to protect one or more of the blade connecting members (6), the pretension members (8), the connection points (7a, 7b), or the tensioning devices (9) from lightning current; optionally, wherein the lightning protection system (45) is configured to isolate one or more electrical heating elements (18) of the anti-icing system and / or de-icing system (17) from lightning current.

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