WO2010048959A2

WO2010048959A2 - A wind turbine generator with extended blade support

Info

Publication number: WO2010048959A2
Application number: PCT/DK2009/050280
Authority: WO
Inventors: Erik Sloth
Original assignee: Vestas Wind Systems A/S
Priority date: 2008-10-30
Filing date: 2009-10-27
Publication date: 2010-05-06
Also published as: WO2010048959A3

Abstract

The present invention relates to a wind turbine generator with a hub that has a plurality of radially extending support structures, one radially extending support structure for each rotor blade, and a plurality of inclined support beams, one inclined support beam for each rotor blade, and/or a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures. The inclined support beams, and/or the first peripheral support rod have an airfoil shape providing aerodynamic lift upon wind engagement. This is advantageous for obtaining a wind turbine where the rotor blades resonances are controlled by designing and dimensioning the plurality of inclined support beams and the first peripheral support rod accordingly. At the same time the volume of the hub is utilized for increasing the aerodynamic lift while still facilitating a relatively strong structure of the hub.

Description

A WIND TURBINE GENERATOR WITH EXTENDED BLADE SUPPORT

FIELD OF THE INVENTION

The present invention relates to wind turbine generator with a hub structure that provides extended rotor blades support. The invention also relates to the hub structure, and to a corresponding method for operating a wind turbine generator.

BACKGROUND OF THE INVENTION

Normally, a wind turbine generator (WTG) or wind turbine has one or more rotor blades which are rotatable around a horizontal axis mounted in a nacelle. The nacelle is pivotable around a vertical axis in order to turn the rotor blade to a position which is aligned with the wind direction. The one or more rotor blades is rotated at a speed which is depending on the wind and the aerodynamics of the rotor blades in order to drive a generator for converting wind energy into electric energy. The typically three rotor blades are connected with a hub, which is in turn mechanically connected with a rotating shaft. The hub is accordingly a critical mechanical part of a modern wind turbine generator. On one hand, the hub should be able to withstand a large mechanical load arising from the rotor blades, and on the other hand the hub, as a rotating part, should have a relatively low weight in order not to give rise to losses in the wind turbine generator. Moreover, the hub should preferably have a beneficial aero dynamical design in order not to increase air resistance and/or create noise upon rotation.

US patent application 2006/0104820 discloses the hub for the rotor of a wind energy turbine which comprises a hollow body rotatable around a rotation axis and provided with at least one flange for mounting to the hollow body, a bearing for a rotor blade and two or more stiffening webs. The webs are integrally formed with the hollow body and radially extending within a flange area of the hollow body surrounded by the flange to the center of the flange area, wherein at least two openings are provided within the flange area of the hollow body. This reinforced hub has a relatively low weight and is also sufficiently stiff to withstand forces acting on the rotor blades and forces resulting from the loads. However, with the current trend of increasing wind turbine generator size, the forces from the rotor blades influencing the hub, e.g. by a large moment over the blade bearing wherein the rotor blades are mounted, are correspondingly quite high, and the web-reinforced hub disclosed in US patent application

2006/0104820 might not even be sufficient. This hub also has a relatively complicated design which may significantly increase manufacturing time and/or cost. Furthermore, transportation of hubs of this size can be a problem. With the increasing size of rotor blades in wind turbine generators, and the corresponding loads from and on the rotor blades, rotor blade resonances, both in-plane and out-of-plane, can further severely impact life time and durability of the wind turbine generator.

Hence, an improved wind turbine generator would be advantageous, and in particular a more efficient and/or reliable wind turbine generator would be advantageous.

OBJECT OF THE INVENTION

It is a further object of the present invention to provide an alternative to the prior art.

In particular, it may be seen as an object of the present invention to provide an improved wind turbine generator that solves the above-mentioned problems of the prior art with inter alia high loads of the hitherto known hubs used in wind turbine generators.

SUMMARY OF THE INVENTION

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a wind turbine generator comprising: a plurality of rotor blades, a rotation shaft, and - a hub for connecting the plurality of rotor blades with the rotation shaft, wherein the hub further comprises

- a plurality of radially extending support structures, one radially extending support structure for each rotor blade, each support structure comprising at least a first blade support point for receiving and supporting a rotor blade, and

a plurality of inclined support beams, one inclined support beam for each rotor blade, the first end portion of each inclined support beam being connected to the corresponding radially extending support structure, the second end portion of each inclined support beam of the plurality of inclined support beams being collected in a common, connecting point in an exterior position on the hub, and/or - at least a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures.

wherein the inclined support beams, and/or the first peripheral support rod have an airfoil shape providing aerodynamic lift upon wind engagement.

The invention is particularly, but not exclusively, advantageous for obtaining a wind turbine generator where the resonances of the rotor blades are controlled, i.e. shifted and/or reduced, by designing and dimensioning the plurality of inclined support beams and/or the first peripheral support rod accordingly. At the same time the volume of the hub is utilized for increasing the aerodynamic lift while still facilitating a relatively strong structure of the hub.

This may facilitate the application of even longer rotor blades than hitherto applied in the wind turbine generator technology. This is quite important because the covered wind area of a wind turbine generator scales with the square of the length of the rotor blades.

Another advantage of the present invention arises from the fact that the connecting hub, due to its pyramid-like structure, may be transported in smaller parts, e.g. the radially extending structure, the support beams, and/or the peripheral support rods may be transported and assembled on or near the site of the wind turbine generator. This may also facilitate even larger wind turbine generators to be manufactured, transported and assembled because currently wind turbine generators have reached a size where limitations imposed by the transportation, both in terms of cost and physical limitations (e.g. width of roads and/or trucks), have reached a relatively high level.

As compared to many single-cast hubs currently applied, the mechanical properties of the present invention may be very attractive, even though the assembly of the hub near or on the site of the wind turbine generator may slightly complicate the final stage of the wind turbine generator assembly. It is however also envisioned that all, or alternatively, most of the various parts of the hub of the present invention may be assembled already during manufacturing.

In the context of the present invention, it is to be understood that the concept of an airfoil shape (or aerofoil shape) locally defines a structure which, upon wind engagement, provides a significant lift. The cross-sectional shape may be symmetric or anti-symmetric, but preferably an anti-symmetric cross-sectional shape may be chosen. The aspect ratio of the cross-sectional shape, i.e., the chord length to maximum thickness, is preferably in the interval from 2 to 10, more preferably in the interval from 4 to 8. Alternatively, the minimum aspect ratio is at least 2, 3, 4, 5, 6, 7, 8, 9, or 10. Preferably, the lift coefficient (C_L) may be at least 0.5, at least 0.7, at least 0.9, or at least 1.1 of any of the airfoil shaped hub parts according to the present invention.

In the context of the present invention, it is to be understood that the inclined support beams and/or peripheral support rods may in principle have any appropriate shape (longitudinal and cross-sectional) suitable for fulfilling their purpose of supporting the rotor blade and providing aerodynamic lift upon wind engagement. Thus, the support beam need not be limited to having a substantially straight shape in the longitudinal direction, but could have various curved or bent shapes. Furthermore, the peripheral support rods could in particular have a curved shape in the longitudinal direction. In particular, for a wind turbine with only two rotor blades, the shape of the two intermediate peripheral support rods could be half-arcs connecting each rotor blade. In one embodiment, the generator may be a variable-speed wind turbine generator that provides several known advantages.

Preferably, the airfoil shape of the inclined support beams, and/or the first peripheral support rod may cover at least 4%, preferably at least 8%, or more preferably at least 12%, of the projected circular area covered by the hub as defined by an outer end part of the plurality of radially extending support structures. The more area that is utilized of the hub for wind harvesting, the more energy will be obtained from the wind turbine. It should be noted that the present invention facilitates both larger hub structures and wind lift from the hitherto lost wind area of the hub structure thereby avoiding a compromise between these two constraints.

In another embodiment, the generator may further comprise a shaft having a substantially central position in the hub, the shaft extending substantially along the rotation shaft for supporting the plurality of inclined support beams in the common, connecting point. This may advantageously support the common connection point for the inclined beams.

The generator may preferably comprise a second peripheral support rod positioned in an exterior position on the hub, said second support rod connecting two of said radially extending support structures similarly to the first support rod. Typically, all rotor blades are inter-connected with support rods, but it could be sufficient for some wind turbines to just have two support rods to obtain e.g. blade edge vibration frequency shifting. Even more advantageously, each peripheral support rod directly connects two radially extending support structures, whereby the said support rod together with the two connected radially extending support structures have a substantially triangular shape. In one variant of the invention, at least one of said peripheral support rods may connect two radially extending support structures at two different radial positions relative to the rotating shaft because this may be advantageous for shifting the frequency of edge vibrations in a different manner as compared to the same radial positions. Typically, each radially extending support structure may comprise a first and a second rotor blade support point for receiving and supporting a rotor blade, said first and second rotor blade support points being located at radially different positions relative to the rotation shaft. This has the advantage that the two radial bearings result in reduction of moment over the blade bearings. Preferably, the said first and the said second rotor blade support points may be located opposite each other in separate radial half parts of the radially extending support structure. Preferably, the said first and the said second rotor blade support points may be located with a radial distance being at least 5%, 10% or 15% of the total rotor blade length as measured from the rotational shaft.

Advantageously, each radially extending support structure may have a radial extension of at least 10%, preferably at least 15%, or more preferably at least 20%, of the total rotor blade length as measured from the rotational shaft. In general, the longer radial support structure, the less amplitude there will be on the edge and/or the flap vibration of the blades.

Preferably, each radially extending support structure may comprise a hollow portion for receiving a corresponding end portion of the rotor blade. Typically, the rotor blades may be pitchably mounted, for example in the first and the second support point in a type of pitch bearing.

In one embodiment, the radially extending support structures may also have an airfoil shape providing aerodynamic lift upon wind engagement. Even further, these structures may be arranged in order for these shapes to be pitchable, though sufficient support should also be provided to the rotor blades.

In a preferred embodiment, the airfoil shape of the inclined support beams, and/or the first and/or the second peripheral support rod(s) may be pitchably mounted in order to optimize the wind lift by changing the angle of attack for each element.

In another embodiment, which is particularly relevant for remote locations such as off-shore wind turbines, each rotor blade in the plurality of rotor blades may be adapted to be temporally fixated to the corresponding radially extending support structure in a manner different from the normal mounting, for instance to allow for exchange of the first and/or the second rotor blade support point in the radially extending support structure, thereby enabling repair of bearings to be performed while the blade is for example clamped to the hub without use of the bearings used during normal operation.

In a second aspect, the present invention relates to a hub for use in a wind turbine generator comprising a plurality of rotor blades and a rotation shaft, the hub being arranged for connecting the plurality of rotor blades with the rotation shaft, wherein the hub comprises:

- a plurality of radially extending support structures, one radially extending support structure for each rotor blade, each support structure comprising at least a first blade support point for receiving and supporting a rotor blade, and a plurality of inclined support beams, one inclined support beam for each rotor blade, the first end portion of each inclined support beam being connected to the corresponding radially extending support structure, the second end portion of each inclined support beam of the plurality of inclined support beams being collected in a common, connecting point in an exterior position on the hub, and/or at least a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures, wherein the inclined support beams, and/or the first peripheral support rod have an airfoil shape providing aerodynamic lift upon wind engagement.

In a third aspect, the invention further relates to a method being adapted to enable operation of a wind turbine generator according to a first aspect of the invention. The method comprises: - providing a plurality of rotor blades, providing a rotation shaft, and providing a hub for connecting the plurality of rotor blades with the rotation shaft, wherein the hub further comprises - a plurality of radially extending support structures, one radially extending support structure for each rotor blade, each support structure comprising at least a first blade support point for receiving and supporting a rotor blade, and a plurality of inclined support beams, one inclined support beam for each rotor blade, the first end portion of each inclined support beam being connected to the corresponding radially extending support structure, the second end portion of each inclined support beam of the plurality of inclined support beams being collected in a common, connecting point in an exterior position on the hub, and/or at least a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures, wherein the inclined support beams, and/or the first peripheral support rod have an airfoil shape providing aerodynamic lift upon wind engagement.

This aspect of the invention is particularly, but not exclusively, advantageous in that the method according to the present invention may be implemented near or on the site of assembly of the wind turbine generator providing easier transportation of at least the hub of the wind turbine generator.

The first, second and third aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The wind turbine generator according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 is a perspective drawing of a wind turbine generator according to the present invention, Figure 2 is a side view drawing of a wind turbine generator according to the present invention,

Figure 3 is schematic drawing of selected part of a hub for a wind turbine generator according to the present invention,

Figure 4 is a schematic drawing of a peripheral support rod configuration according to the present invention,

Figures 5 and 6 are schematic perspective drawings of three connected radially extending support structures according to the present invention,

Figure 7 is a schematic plan view of three connected radially extending support structures with radial support points according to the present invention,

Figure 8 is a schematic perspective drawing of three connected radially extending support structures with airfoil shape according to the present invention, and

Figure 9 is a schematic plan view of three connected radially extending support structures with temporary fixation points according to the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1 is a perspective drawing of a wind turbine generator 1 according to the present invention, the tower being omitted for clarity. The wind turbine generator 1 comprises a plurality of rotor blades 2, i.e. three blades in this embodiment. The blades 2 are mechanically connected to a rotation shaft 3 by the hub 4.

The hub 4 comprises three radially extending support structures 5, one radially extending support structure 5 for each rotor blade 2. Each support structure comprises at least a first blade support point for receiving and supporting a rotor blade 2 (not shown in this Figure). Furthermore, the hub 4 has three inclined support beams 6, one inclined support beam for each rotor blade 2. The first end portion of each inclined support beam 6 is connected to the corresponding radially extending support structure 5, and the second end portion of each inclined support beam 6 is collected in a common, connecting point 7 in an exterior position on the hub 4, which is in the front part of the hub 4.

Three peripheral support rods 8 are positioned in an exterior position on the hub 4, each of the three peripheral support rods 8 are connecting two of the radially extending support structures 5.

In addition, the inclined support beams 6 and the three peripheral support rods 8 have an airfoil shape providing aerodynamic lift upon wind engagement. This is shown in the exploded cross-sectional view named X6 of one beam 5. Similarly, this is also indicated by the exploded cross-sectional view named X8 of one rod 8.

The wind turbine generator 1 further comprises a shaft 9 having a substantially central position in the hub 4. This shaft 9 is extending substantially along the rotating shaft 3 for supporting the plurality of inclined support beams in the common, connecting point 7.

In Figure 1, the airfoil shape of the three inclined support beams or stays 6 and the airfoil shape of the three peripheral support rods 8 are indicated as one airfoil shape, but it is also contemplated that separate, and possibly independently pitchable, parts could form part of the airfoil shape for each rod 8 or beam 6. It is to be understood that the beams 6 are inclined relative to a rotational plane of the radially extending structures 5.

In another embodiment, it is contemplated that additional auxiliary inclined beams (not shown in Figure 2) may be provided in the hub 4. The auxiliary beams may be fixed to the common point 7 in one end and fixed or mounted on a peripheral support rod 8 at the other end. By having airfoil shape even more wind could be advantageously applied or "harvested" by a hub according to the present invention. In Figure 1, the root of each rotor blade 2 is adapted for mounting on a corresponding radially extending support structure 5 so that the rotor blade 2 is pitchable, i.e. it may rotate around its longitudinal axis. The lower part of the lift contributing part of the rotor blade must accordingly be dimensioned for such a rotation, i.e. it must not collide with the hub structure 4. On the other hand, it is desirable to maximize the effective area of the blades 2 to provide the best aerodynamic lift upon wind engagement. Thus, a compromise is to be made, but the lower part of the rotor blade has other sizes and shapes than the shown one, in particular the lower part could be closed to the hub structure 4 but for clarity this has not been drawn here.

In the present context, the hub structure 4 is considered to comprise inter alia the radially extending support structures 5 that may have an airfoil shape (cf. Figure 8). However, in other contexts it may be understood that the airfoil shaped radially extending support structures 5 are considered as an inner part of a blade structure of a wind turbine generator.

Figure 2 is a side view drawing of a wind turbine generator similar to Figure 1, where the pyramid-like open hub structure positioned in front of the nacelle 20 is apparent. The tower 21 is also indicated. The rotation shaft is lifted with a small angle relative to horizontal.

Figure 3 is a schematic drawing of a selected part of a hub in a wind turbine generator according to the present invention. In particular, the each of three peripheral support rods 8 connects two radially extending support structures 5 directly. Thus, one support rod 8 together with the two connected radially extending support structures 5 have a substantially triangular shape.

Figure 4 is a schematic drawing of a peripheral support rod configuration according to the present invention, where a peripheral support rod 8 connects two radially extending support structures 5' and 5" at two different radial positions relative to the rotating shaft. For clarity, the inclined support beams are omitted in this Figure. Thus, rod 8 is connected to structure 5' at a larger radial distance, as seen from the rotation centre of the rotor blades 2, than the radial position where the rod 8 is connected or joined with the other structure 5". This has advantages both with respect to shifting the frequencies of edge vibrations of the rotor blades 2, and with respect to obtained beneficial aero dynamical benefit of the airfoil shape of the support rod 8.

Figure 5 is a schematic perspective drawing of three connected radially extending support structures 5 comprised in the hub 4 according to the present invention. For clarity, the inclined support beams and the peripheral support rods are omitted in this Figure. As seen for the two lower structures 5, each radially extending support structure 5 comprises a hollow portion 5a for receiving a corresponding end portion of the rotor blade 2, which is positioned under the wing and therefore not visible in this Figure. Preferably, the rotor blades 2 are pitchably mounted in a first and a second support point (not visible in this Figure) within the structure 5, e.g. in a pitch bearing.

Figure 6 is a similar schematic perspective drawing of three connected radially extending support structures 5 comprised in the hub 4 according to the present invention. For clarity, the inclined support beams and the peripheral support rods are also omitted in this Figure. As seen for the two lower structures 5, each radially extending support structure 5 comprises a shaft extension 5b for entering a corresponding hollow portion (not shown in this view) of the rotor blade 2 for assembly. Preferably, the rotor blades 2 are pitchably mounted in a first and a second support point (not visible in this Figure) within the rotor blade 2, e.g. in a pitch bearing. The shaft extension 5b can be made as one solid entity with the radially extending structure 5, or the shaft extension or stub shaft 5b may be mounted on the radially extending structure 5.

Figure 7 is a schematic plan view of three connected radially extending support structures 5 with two radial support points 60a and 60b according to the present invention, the support points 60a and 60b may be bearings or similar means for receiving the corresponding end part of a rotor blade 2. For clarity, the inclined support beams and the peripheral support rods are also omitted in this Figure. The first 60a and a second 60b rotor blade support points are located at radially different positions relative to the rotating shaft 3 connected to the hub 4. The said first and the said second rotor blade support points 60a and 60a may be located opposite each other in separate radial half parts of the radially extending support structure 5. Thus, in the Figure, support points 60a are located in the outer half part of the radial length RS of the radially extending support structure 5, whereas support points 60b are located in the inner half part of the radial length RS of the radially extending support structure 5.

More specifically, the first 60a and the second 60b rotor blade support points are located with a radial distance r being at least 5%, 10% or 15% of the total rotor blade length R as measured from the rotational shaft 4.

Advantageously, the radially extending support structure 5 may have a radial extension RS of at least 10%, preferably at least 15%, or more preferably at least 20%, of the total rotor blade length R as measured from the rotational shaft 3. Generally, the longer the radially extending support structure 5 is, the less amplitude there will be on the edge and flap vibration of the rotor blades 2. Also, improved control vibration frequencies of rotor blades will be obtained.

Figure 8 is a schematic perspective drawing similar to Figure 6 of three connected radially extending support structures 5 with airfoil shape according to the present invention. The radially extending support structures have an airfoil shape providing aerodynamic lift upon wind engagement. The structures 5 define a shape which, upon wind engagement, provides a significant lift. The cross- sectional shape may be symmetric or anti-symmetric, but preferably an anti- symmetric cross-sectional shape may be chosen. The aspect ratio of the cross- sectional shape, i.e. the chord length to maximum thickness, is preferably in the interval from 2 to 10, more preferably in the interval from 4 to 8. Alternatively, the minimum aspect ratio is at least 2, 3, 4, 5, 6, 7, 8, 9, or 10.

In one embodiment, it is possible to pitch the airfoil shape of one or more radially extending support structures 5, i.e. the angle of attack with the wind is variable upon appropriate actuation.

Similarly, the airfoil shape of the inclined support beams 6 and the peripheral support rods 8 can be pitchably mounted in order to provide a controllable lift, where the angle of attack can be changed. Preferably, the lift coefficient (C_L) can be at least 0.5, 0.7, 0.9, or at least 1.1 of any of the airfoil shaped hub parts according to the present invention.

Figure 9 is a schematic plan view of three connected radially extending support structures with temporary fixation means 80a and 80b according to the present invention. The fixation means 80 has the functionality that the rotor blade 2 is adapted to be temporally fixated to the corresponding radially extending support structure 5 to allow for exchange of the first and the second rotor blade support 60a and 60b point within the radially extending support structure 5. Thus, for instance repair or replacement of a bearing in the support points 60a or 60b can be performed while the blade 2 is fixed to the hub 4. The fixation means 80a and 80b can be various mechanical fixation means, such as hydraulic jacks, screw jacks, etc. Moreover, the rotor blade 2 can have a receiving part 81a and 81b corresponding to the fixation means 80a and 80b, as indicated in Figure 8. Thus, the fixation means 80 could for instance have a protruding part shaped to fit in a corresponding hollow part in the rotor blade 2. Preferably, the receiving part 81a and 81b and the fixation means 80a and 80b may, upon engagement, have a locking cooperation so as to firmly secure the rotor blade 2 during maintenance and service of the first and the second rotor blade support 60a and 60b points.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A wind turbine generator comprising:

- a plurality of rotor blades,

a rotating shaft, and

a hub for connecting the plurality of rotor blades with the rotating shaft,

wherein the hub further comprises

a plurality of inclined support beams, one inclined support beam for each rotor blade, the first end portion of each inclined support beam being connected to the corresponding radially extending support structure, the second end portion of each inclined support beam of the plurality of inclined support beams being collected in a common, connecting point in an exterior position on the hub, and/or at least a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures,

2. The generator according to claim 1, wherein the wind turbine generator is a variable-speed wind turbine generator.

3. The generator according to claim 1, wherein the airfoil shape of the inclined support beams, and/or the first peripheral support rod covers at least 4%, preferably at least 8%, or more preferably at least 12%, of the projected circular area covered by the hub as defined by an outer end part of the plurality of radially extending support structures.

4. The generator according to claim 1, wherein the generator further comprises a shaft having a substantially central position in the hub, the shaft extending substantially along the rotating shaft for supporting the plurality of inclined support beams in the common, connecting point.

5. The generator according to claim 1, wherein the generator further comprises a second peripheral support rod positioned in an exterior position on the hub, said second support rod connecting two of said radially extending support structures.

6. The generator according to claim 5, wherein each peripheral support rod connects two radially extending support structures directly, whereby the said support rod together with the two connected radially extending support structures have a substantially triangular shape.

7. The generator according to claim 5 or claim 6, wherein at least one of said peripheral support rods connects two radially extending support structures at two different radial positions relative to the rotation shaft.

8. The generator according to claim 1, wherein each radially extending support structure further comprises a first and a second rotor blade support point for receiving and supporting a rotor blade, said first and second rotor blade support points being located at radially different positions relative to the rotation shaft.

9. The generator according to claim 8, wherein the said first and the said second rotor blade support points are located opposite each other in separate radial half parts of the radially extending support structure.

10. The generator according to claim 8 or 9, wherein the said first and the said second rotor blade support points are located with a radial distance being at least 5%, 10% or 15% of the total rotor blade length as measured from the rotational shaft.

11. The generator according to claim 1, wherein each radially extending support structure has a radial extension of at least 10%, preferably at least 15%, or more preferably at least 20%, of the total rotor blade length as measured from the rotational shaft.

12. The generator according to claim 1, wherein each radially extending support structure comprises a hollow portion for receiving a corresponding end portion of the rotor blade.

13. The generator according to any of the preceding claims, wherein the rotor blades are pitchably mounted.

14. The generator according to any of the preceding claims, wherein the radially extending support structures have an airfoil shape providing aerodynamic lift upon wind engagement.

15. The generator according to any of the preceding claims, wherein the airfoil shape of the inclined support beams, and/or the first and/or the second peripheral support rod(s) are pitchably mounted.

16. The generator according to any of the preceding claims, wherein each rotor blade in the plurality of rotor blades are adapted to be temporally fixated to the corresponding radially extending support structure in a manner different from the normal mounting.

17. A hub for use in a wind turbine generator comprising a plurality of rotor blades and a rotation shaft, the hub being arranged for connecting the plurality of rotor blades with the rotation shaft, wherein the hub comprises:

- a plurality of radially extending support structures, one radially extending support structure for each rotor blade, each support structure comprising at least a first blade support point for receiving and supporting a rotor blade, and a plurality of inclined support beams, one inclined support beam for each rotor blade, the first end portion of each inclined support beam being connected to the corresponding radially extending support structure, the second end portion of each inclined support beam of the plurality of inclined support beams being collected in a common, connecting point in an exterior position on the hub, and/or at least a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures,

18. A method for operating a wind turbine generator, the method comprises:

providing a plurality of rotor blades,

providing a rotation shaft, and

providing a hub for connecting the plurality of rotor blades with the rotation shaft,

wherein the hub further comprises

- a plurality of inclined support beams, one inclined support beam for each rotor blade, the first end portion of each inclined support beam being connected to the corresponding radially extending support structure, the second end portion of each inclined support beam of the plurality of inclined support beams being collected in a common, connecting point in an exterior position on the hub, and/or at least a first peripheral support rod positioned in an exterior position on the hub, said first peripheral support rod connecting two of said radially extending support structures,