Pitch-controlled wind turbine

Abstract

According to the present invention, there is provided a pitch-controlled wind turbine comprising a tower, a nacelle mounted on the tower, a hub mounted rotatably on the nacelle, and three or more wind turbine blades Each wind turbine blade extends between a root end connected to the hub, and a tip end arranged opposite to the root end. The wind turbine further comprises blade connecting assemblies comprising blade connecting members. Each blade connecting member extending between a connection location at one wind turbine blade and a connection location at a neighbouring wind turbine blade. The connection location at 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 one of the wind turbine blades has a first colour and at least one of the blade connecting assemblies is a contrast blade connecting assembly having a contrast colour and the contrast colour is different from the first colour.

Description

[0001] Pitch-controlled wind turbine

[0002] Technical field

[0003] The present invention relates to a pitch-controlled wind turbine comprising a tower, a nacelle mounted on the tower, and a hub mounted rotatably on the nacelle and a plurality of wind turbine blades.

[0004] Bird collisions with wind turbine blades (also referred to as bird strikes) are highly undesirable for both birds and blades and considerable effort to reduce bird strikes have been conducted. There are indications that frequency of bird strikes may be reduced by minimizing of motion smear of the blades by providing colour to one single blade. Such colour may be applied as paint or adhesive strips applied to the outer blade surface. Typically, the suggested colour is black as a contrast to the traditionally white blades.

[0005] Unfortunately, large, coloured members, such as black wind turbine blades, may heat up to an undesired level upon exposure to sunlight. Furthermore, colour contrasting of blades that reduce the motion smear of the blades tend to be very annoying to the human eye even from long distances and therefore may be unacceptable for practical applications.

[0006] It is against this background that the present invention has been devised.

[0007] According to the present invention, there is provided a pitch-controlled wind turbine comprising a tower, a nacelle mounted on the tower, a hub mounted rotatably on the nacelle, and three or more wind turbine blades. Each wind turbine blade extends between a root end connected to the hub, and a tip end arranged opposite to the root end. The wind turbine further comprises blade connecting assemblies comprising blade connecting members. Each blade connecting member extending between a connection location at one wind turbine blade and a connection location at a neighbouring wind turbine blade. The connection location at 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 one of the wind turbine blades has a first colour and at least one of the blade connecting assemblies is a contrast blade connecting assembly having a contrast colour and the contrast colour is different from the first colour.

[0008] It should be understood that references to each "connection location" refer to a location along the spanwise length of the blade. In some examples a plurality of blade connecting members may be connected to a blade at the same connection location, but at different points around the airfoil profile of the blade at the connection location.

[0009] The blade connecting members connected between corresponding connection locations of a pair of wind turbine blades advantageously reduce loading of the inboard portion of the blades in use because some of the blade loads are diverted to the blade connecting members instead of progressing to the hub via the inboard portion of the respective loaded blade. In particular, loads may be transferred from a higher loaded blade to a lesser loaded blade via a blade connecting member in use. The blade connecting members may reduce edgewise loads, flapwise loads or both edgewise loads and flapwise loads in the inboard portion of a higher loaded blade. The arrangement of blade connecting members is particularly advantageous for reducing edgewise fatigue loads, i.e. gravity driven loads. Accordingly, the blade connecting members facilitate the use of larger blades without necessitating an increase in blade root diameter to support the increased loads of such larger blades, because some of the blade loads are transferred to the blade connecting members, bypassing the inboard portion and blade root of the respective blade.

[0010] Each pitch mechanism preferably comprises a pitch bearing via which each respective blade is connected to the hub. Additionally, in some preferred examples each pitch mechanism may include a pitch drive, such as a geared drive or an actuator, for applying a force to each blade to rotate the blade about its respective pitch axis.

[0011] In the present context, the blade connecting assembly may comprise a braided or laid rope of metal wires (such as steel wires, for example), polymer fibres (such as polyethylene, polypropylene, nylon, polyester, aramid fibres, for example), inorganic fibres (such as carbon fibres, for example) or hybrid ropes of such materials. Most preferably the tension member comprises a polymer rope, such as a braided polymer rope. For example, a tension member may comprise ultrahigh molecular weight polyethylene fibres, such as Dyneema® DM20 based polymer rope. The colour of (part of) the blade connecting assembly may for example originate from one or more yarns, cords or wires being coloured, from a coating applied to the blade connecting assembly, from an overbraiding by coloured material, by application of shrink wrap onto the assembly.

[0012] It will be appreciated that as used herein, the contrast blade connecting assembly having a contrast colour means that at least a part of the blade connecting assembly is having a contrast colour. In one example, the part of the blade connecting assembly having a contrast colour is sufficiently large to be visible to approaching birds at a distance where approaching birds may deviate from the wind turbine generator.

[0013] Surprisingly, it was found that by providing a colour of at least a part of the blade connecting assemblies which colour is different from the colour of the blades, the wind turbine is more visible to birds in the vicinity of the wind turbine generator and the birds may hence evade the wind turbine and thereby the risk of collision may be reduced or even prevented. Hence, a similar positive effect as colouring of full blades may be realized without one or more of the disadvantages of providing coloured blades. For example, heating by sun light is significantly reduced due to the typical smaller size and generally circular cross section (leading to lower fraction of the surface exposed to direct sun light). As will be discussed below, colour may be provided to the blade connecting assembly by various well- known methods. Furthermore, contrasting colours of the blade connecting assembly may typically not be distracting to the human eye at distances above a few hundred meters whereas birds evading wind turbine generators typically deviate from the course only at shorter distances, where the contrasting colour would be visible.

[0014] In some examples, the blade connecting member of the contrast blade connecting assembly is contrast colour. In one embodiment, the blade connecting members all have contrast colour. It was found that instead of a smearing effect realized by applying contrast colour to a blade, providing all connecting members in contrast colour provided a sharp line in the rotor plane and during rotation of the rotor, the line would wobble in and out since the blade connecting members are straight tensioned sections, which enhance visibility.

[0015] In some preferred examples, the pitch-controlled wind turbine comprises a support structure and the support structure extends from the hub to define a support point. Each blade connecting assembly comprises a tension member arranged between the support point and an attachment point of the blade connecting member of the blade connecting assembly. In these examples, the support point is located upwind relative to each connection location. Such pitch- controlled wind turbines were found to allow for easier adjustment of tension in the blade connection members by adjusting the tension in the corresponding tension members.

[0016] In some examples, the tension member of the contrast blade connecting assembly is contrast colour. As the tension member is generally arranged closer to the hub than other parts of the blade connecting assembly, it could be theorized without being limited thereto that the smearing effect of a tension member being contrast colour may be smaller (doe to lower movement speed) than smearing effect of for example a coloured full wind turbine blade.

[0017] The contrast blade connecting assembly may comprise a contrast section having contrast colour and a first section having first colour. Such a contrast section may for example be at least a part of the blade connecting member. In some cases, combinations of sections of contrast colour and sections of first colours may be more visible to birds, particularly at relatively low rotor rotation speed.

[0018] In some examples, the contrast blade connecting assembly may comprise a second contrast section having a second contrast colour. Such second contrast colour may be different from the contrast colour and the first colour. This may for example be advantageous for enhancing visibility of the contrast blade connecting assembly at relatively low rotor rotation speed.

[0019] The contrast colour may be provided to the contrast blade connecting assembly by various ways. Examples are application of a coating, for example by surface coating or a dip-coating of the blade connecting assembly or a part thereof; application of a heat shrink wrap onto the blade connecting assembly or a part thereof; overbraiding of the blade connecting assembly or a part thereof by yarns of which at least some is of the contrast colour or when placed together in an overbraiding appears to be of the contrast colour. The contrast colour may also be provided as a coloured yarns of a main braid with no overbraiding of a (part of) a blade connecting assembly.

[0020] In preferred examples, the contrast blade connecting assembly may comprise a coating or an overbraiding having contrast colour. Overbraiding having contrast colour may be particularly advantageous as this allows for lower amounts of yarns having contrast colour than if the full contrast blade connecting assembly would be of yarns having contrast colour and allow for readily changes in contrast colour or colour patterns.

[0021] In some examples, the blade connecting assembly further comprises a bird scare. The bird scare may be a model of a predator bird and for example by connected to the blade connecting member or connected to the tension member. It is preferred that the bird scare is connected to the tension member as this allows for arranging the bird scare relatively close to the centre of the wind turbine where the wind exposure and associated drag is relatively limited as compared to positioning further out on the blade. Provision of bird scare may in some cases provide a synergetic bird repulsion effect in combination with the contrasting colour of (part of) the blade connecting assemblies.

[0022] In some examples, at least one of the wind turbine blades is a contrasting wind turbine blade comprising a blade contrast portion having a further contrast colour and the further contrast colour is different from the first colour. Here, the blade contrast portion may be in an outboard portion of the contrasting wind turbine blade. It will be appreciated that the ourboard portion may be between the connection location and the tip end of the contrasting wind turbine blade. Provision of blade contrast portions may in some cases provide a synergetic bird repulsion effect in combination with the contrasting colour of (part of) the blade connecting assemblies.

[0023] In some examples, the blade contrast portion is a patterned portion or a continuously coloured portion of the contrasting wind turbine blade. A patterned portion may for example be portion having spots, lines, geometrical or randomly arranged contrast coloured features.

[0024] Another aspect of the invention concerns use of a contrast blade connecting assembly for reducing likelihood of bird collision with a pitch-controlled wind turbine. The wind turbine comprises a tower, a nacelle mounted on the tower, a hub mounted rotatably on the nacelle, and three or more wind turbine blades. Each wind turbine blade extends between a root end connected to the hub, and a tip end arranged opposite to the root end. The wind turbine further comprises blade connecting assemblies comprising blade connecting members. Each blade connecting member extends between a connection location at one wind turbine blade and a connection location at a neighbouring wind turbine blade. The connection location at 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 one of the wind turbine blades has a first colour and at least one of the blade connecting assemblies is a contrast blade connecting assembly having a contrast colour and the contrast colour is different from the first colour

[0025] Brief description of the drawinas

[0026] Examples of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

[0027] Figure 1 is a schematic perspective view of a pitch-controlled wind turbine comprising blade connecting assemblies with blade connecting members having contrast colour;

[0028] Figure 2 is a schematic front view of a rotor of the pitch-controlled wind turbine in a plane parallel to a rotor plane of the turbine;

[0029] Figure 3 is a schematic perspective view of a pitch-controlled wind turbine comprising a support structure and blade connecting assemblies comprising tension members connected between the support structure and a respective blade connecting member; Figure 4 is a schematic front view of the rotor comprising tension members in a plane parallel to the rotor plane;

[0030] Figure 5 is a schematic perspective view of a rotor comprising a blade contrast portion;

[0031] Figure 5 is a schematic front view of the rotor comprising tension members in a plane parallel to the rotor plane.

[0032] Detailed

[0033] In Figure 1, a pitch-controlled wind turbine 10 is a shown. It comprises a tower 12, a nacelle 14 mounted on the tower 12, a hub 18 mounted rotatably on the nacelle 14, and three or more wind turbine blades 20. Each wind turbine blade 20 extends between a root end 22 connected to the hub 18, and a tip end 24 arranged opposite to the root end. The wind turbine 10 further comprises blade connecting assemblies 33 comprising blade connecting members 32. Each blade connecting member 32 extends between a connection location 30 at one wind turbine blade 20 and a connection location 30 at a neighbouring wind turbine blade 20. The connection location 30 at a given wind turbine blade 20 is arranged at a distance (such as for example 25 - 60% of the blade length) from the root end 22 and at a distance (such as for example 40 - 75% of the blade length) from the tip end 24 of the wind turbine blade 20.

[0034] The wind turbine blades 20 of the rotor 16 in Figure 1 are white and the first colour is therefore white. Even thou smaller areas of the blade may have another colour, for example due to local aviation safety requirements coloured dots, strips or blade tip areas may be present on a blade, the dominating blade colour is referred to as the first colour in the present context. Typically (as is the case in Figure 1), the first colour is white.

[0035] Each wind turbine blade has an outboard portion 28 between the connection location 30 and the tip end 24 and an inboard portion 26 between the connection location 30 and the blade root 22. The blade connecting assemblies 33 of Figure 1 are black and hence contrast blade connecting assemblies 33a as black is different from white. When the first colour is white, then examples (in addition to black) of other contrast colours are yellow, red, blue, green, cyan, magenta.

[0036] A colour may be defined in the RGB colour model by its RGB (red, green, blue) values with values of 0-255 for colour channel) and a colour difference between two colours within this colour space may be defined by the Euclidean distance, d :

[0037] In the present context, it is preferred that the colour distance between the first colour and the contrast colour is at least 100 and preferably at least 150. It is also preferred that the colour distance between the second contrast colour and the contrast colour is at least 100 and preferably at least 150. It is further preferred that the colour distance between the second contrast colour and the first colour is at least 100 and preferably at least 150. Similarly, it is preferred that the colour distance between the first colour and the further contrast colour is at least 100 and preferably at least 150.

[0038] In Figure 2, a schematic front view of a rotor is shown with wind turbine blades 20 being connected to the hub 18 at the root end 22 of the blades. The blades have a first colour, white, and the connecting assemblies 33 are a combination of:

[0039] • A, one blade connection assembly 33 in the same colour as the blade first colour (white);

[0040] • B, one blade connection assembly having a black blade connecting member 32 and hence being a contrasting blade connection assembly 33a;

[0041] • C, one blade connection assembly having a blade connecting member 32 with a black section (being a contrast section 35a having a contrast colour) and a white section (being a first section 35b) and hence being a contrast blade connection assembly 33a.

[0042] Figure 3 shows a schematic perspective view of a pitch-controlled wind turbine 10 comprising a support structure 56 and blade connecting assemblies 33 / 33a comprising tension members 60. The support structure 56 extends from the hub 18 to define a support point 58. The tension members 60 are arranged between the support point 58 and an attachment point 62 of the blade connecting member 32 of the blade connecting assembly 33. The support point 58 is located upwind relative to each connection locations 30 Each tension member 60 may be connected to the support point 58 via a respective linear actuator 64. Such an actuator 64 preferably has an adjustable length and may therefore be configured to adjust the tension in the tension member 60 and the associated blade connecting member 32.

[0043] The blade connecting assemblies 33a on Figure 3 comprises tension members 60 and blade connection members 32, which are black - a contrasting colour of the white wind turbine blades 20. Hence, the blade connection assemblies are all contrast blade connection assemblies 33a.

[0044] Figure 4 shows another schematic front view of a rotor with wind turbine blades 20. The blades have a first colour, white, and the connecting assemblies 33 arranged between connection locations 30 of neighbouring wind turbine blades 20 comprises blade connecting members 32 and tension members 60 connected at connection locations 62. The connection assemblies are a combination of:

[0045] • D, one blade connection assembly 33 in the same colour as the blade first colour (white);

[0046] • E, one blade connection assembly having a black blade connecting member 32 and tension member 60, and hence being a contrasting blade connection assembly 33a;

[0047] • F, one blade connection assembly having a blade connecting member 32 with a black blade connection member section (being a contrast section 35a having a contrast colour), a white section blade connection section (being a first section 35b) and a yellow tension member (being a second contrast section 35c since yellow is different from both the black contrast colour and the white first colour), hence forming a contrast blade connection assembly 33a.

[0048] In some cases, bird protection by contrasting colours of (part of) blade connecting assemblies 33 may be further may enhanced by combining with at least one of the wind turbine blades 20 being a contrasting wind turbine blade 20a. In Figure 5, a contrasting wind turbine blade 20a is coloured black on the outboard portion of the blade, so this portion of the blade forms a blade contrast portion 28a. Since the inner part of the rotor already has the contrasting bird protection feature from the contrasting blade connection assembly 33a, it was found to be advantages that the blade contrast portion 28a is the outboard portion of the contrasting wind turbine blade 20a as shown in Figure 5, but in some cases the inboard portion may be the blade contrast portion or the whole blade may have contrasting colour.

[0049] In some cases, bird protection by contrasting colours of (part of) blade connecting assemblies 33 may be further may enhanced by combining with connecting a bird scare 37 to a blade connecting member 32 or a tension member 60. An example of this is shown in Figure 6, where the bird scare 37 is connected to the tension member. It is advantageous to arrange the bird scare relatively close to the centre of the rotor 16, as the speed of the tension member is relatively low in this area so wear and drag is limited while the effect of a moving bird scare is maintained. Other types of bird scares may also be added, such as stickers indicating bird eyes. It will be appreciated that the description provided above serves to demonstrate a plurality of possible examples of the present invention. Features described in relation to any of the examples above may be readily combined with any other features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. A pitch-controlled wind turbine (10) comprising a tower (12), a nacelle (14) mounted on the tower (12), a hub (18) mounted rotatably on the nacelle (14), and three or more wind turbine blades (20), wherein each wind turbine blade (20) extends between a root end (22) connected to the hub (18), and a tip end (24) arranged opposite to the root end (22), the wind turbine (10) further comprising blade connecting assemblies (33) comprising blade connecting members (32), each blade connecting member (32) extending between a connection location (30) at one wind turbine blade (20) and a connection location (30) at a neighbouring wind turbine blade (20), where the connection location (30) at a given wind turbine blade (20) is arranged at a distance from the root end (22) and at a distance from the tip end (24) of the wind turbine blade (20), wherein at least one of the wind turbine blades (20) has a first colour and at least one of the blade connecting assemblies (33) is a contrast blade connecting assembly (33a) having a contrast colour and the contrast colour is different from the first colour.

2. The pitch-controlled wind turbine (10) according to claim 1, wherein the blade connecting member (32) of the contrast blade connecting assembly (33a) is contrast colour.

3. The pitch-controlled wind turbine (10) according to claim 1 or 2, further comprising a support structure (56), wherein the support structure (56) extends from the hub (18) to define a support point (58), wherein each blade connecting assembly (33) comprises a tension member (60) arranged between the support point (58) and an attachment point (62) of the blade connecting member (32) of the blade connecting assembly (33), and wherein the support point (58) is located upwind relative to each connection location (62).

4. The pitch-controlled wind turbine (10) according to claim 3, wherein the tension member (60) of the contrast blade connecting assembly is contrast colour.

5. The pitch-controlled wind turbine (10) according to any one of the preceding claims, wherein the contrast blade connecting assembly (33a) comprises a contrast section (35a) having contrast colour and a first section (35b) having first colour.

6. The pitch-controlled wind turbine (10) according to claim 5, wherein the contrast section 35a is at least a part of the blade connecting member (32).

7. The pitch-controlled wind turbine (10) according to claim 5 or 6, wherein the contrast blade connecting assembly (33a) comprises a second contrast section (35c) having a second contrast colour, and the second contrast colour is different from the contrast colour and the first colour.

8. The pitch-controlled wind turbine (10) according to any one of the preceding claims, wherein the contrast blade connecting assembly (33a) comprises a coating or an overbraiding having contrast colour.

9. The pitch-controlled wind turbine (10) according to any one of the preceding claims, wherein the blade connecting assembly (33) further comprises a bird scare (37) connected to the blade connecting member (32) or connected to the tension member (60).

10. The pitch-controlled wind turbine (10) according to any one of the preceding claims, wherein at least one of the wind turbine blades (20) is a contrasting wind turbine blade (20a) comprising a blade contrast portion (28a) having a further contrast colour, wherein the further contrast colour is different from the first colour.

11. The pitch-controlled wind turbine (10) according to claim 10, wherein the blade contrast portion is in an outboard portion (28) of the contrasting wind turbine blade (20a) between the connection location (30) and the tip end (24) of the contrasting wind turbine blade (20a).

12. The pitch-controlled wind turbine (10) according to claim 10 or 11, wherein the blade contrast portion (28a) is a patterned portion or a continuously coloured portion of the contrasting wind turbine blade (20).

13. Use of a contrast blade connecting assembly (33a) for reducing likelihood of bird collision with a pitch-controlled wind turbine (10), wherein the wind turbine comprises a tower (12), a nacelle (14) mounted on the tower (12), a hub (18) mounted rotatably on the nacelle (14), and three or more wind turbine blades (20), wherein each wind turbine blade (20) extends between a root end (22) connected to the hub (18), and a tip end (24) arranged opposite to the root end (22), the wind turbine (10) further comprising blade connecting assemblies (33) comprising blade connecting members (32), each blade connecting member (32) extending between a connection location (30) at one wind turbine blade (20) and a connection location (30) at a neighbouring wind turbine blade (20), where the connection location (30) at a given wind turbine blade (20) is arranged at a distance from the root end (22) and at a distance from the tip end (24) of the wind turbine blade (20), wherein at least one of the wind turbine blades (20) has a first colour and at least one of the blade connecting assemblies (33) is a contrast blade connecting assembly (33a) having a contrast colour and the contrast colour is different from the first colour.

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