A MULTIROTOR WIND TURBINE

Abstract

A multirotor wind turbine (1) with a tower (2) and at least two energy generating units, the units held by a load carrying structure (9, 10) extending transverse to the vertical direction of the tower. To enable improved access to the wind turbine, a platform (12) forming an upwards facing plane working surface (17) is provided.

Claims

1. A multirotor wind turbine comprising: a tower extending in a vertical direction from a tower bottom to a tower top; at least two energy generating units, each energy generating unit holding a rotor defining a rotor plane, and each energy generating unit comprising a drive train driven by the rotor, and a load carrying structure extending transverse to the vertical direction and arranged to carry the at least two energy generating units, the load carrying structure being carried rotationally by the tower via a yaw arrangement, the multirotor wind turbine further comprising a platform forming an upwards facing plane working surface.

2. The multirotor wind turbine according to claim 1, wherein the working surface is offset in horizontal direction relative to the energy generating units in such a way that the energy generating unit is at least partly outside the outer contour of the working surface when seen in a top view in the direction from the tower top to the tower bottom.

3. The multirotor wind turbine according to claim 1, wherein the working surface is offset in horizontal direction relative to the rotor planes of all energy generating units in such a way that all rotor planes are at least partly outside the outer contour of the platform when seen in a top view in the direction from the tower top to the tower bottom.

4. The multirotor wind turbine according to claim 1, wherein the working surface is arranged symmetrically between two rotor planes when seen in a top view in the direction from the tower top to the tower bottom.

5. The multirotor wind turbine according to claim 1, wherein the working surface is asymmetric relative to the tower top to thereby define an offset in horizontal direction between the geometric centre of the working surface and the geometric centre of a cross section transverse to the tower top.

6. The multirotor wind turbine according to claim 5, wherein the offset is of a size whereby the tower top is at least partly outside the outer contour of the working surface when seen in a top view in the direction from the tower top to the tower bottom.

7. The multirotor wind turbine according to claim 1, wherein a distance from the platform to the tower is smaller than a distance from the platform to the energy generating units.

8. The multirotor wind turbine according to claim 1, wherein the energy generating unit defines a hub-height, and the tower top is at a higher altitude than the hub-height, and the platform is at a higher altitude than the tower top.

9. The multirotor wind turbine according to claim 1, wherein the platform is structurally connected to at least a part of the load carrying structure.

10. The multirotor wind turbine according to claim 1, wherein the platform is structurally connected to the tower top.

11. The multirotor wind turbine according to claim 1, wherein the load carrying structure comprises: a load carrying hub rotationally carried by the tower via the yaw arrangement; a first load carrying arrangement extending outwards on a left side of the load carrying hub; and a second load carrying arrangement extending outwards on a right side of the load carrying hub; each load carrying arrangement comprising a primary structure attached to the load carrying hub in a lower interface and extending between the lower interface and a corresponding one of the at least two energy generating units.

12. The multirotor wind turbine according to claim 11, wherein each load carrying arrangement comprises a tension arrangement, the tension arrangement comprising at least one secondary structure attached to the load carrying hub in an upper interface and extending above the primary structure between the upper interface and the corresponding one of the at least two energy generating units such that gravity acting on the energy generating units causes compression of the primary structure and tension in the at least one secondary structure.

13. The multirotor wind turbine according to claim 12, wherein the tension arrangement comprises: a forward secondary structure attached to the load carrying hub in a forward point of the upper interface and extending above the primary structure between the forward point and the corresponding one of the at least two energy generating units, and a rearward secondary structure attached to the load carrying hub in a rearward point of the upper interface and extending above the primary structure between the rearward point and the corresponding one of the at least two energy generating units, where the forward point and rearward point are on opposite sides of the right side or left side of load carrying hub.

14. The multirotor wind turbine according to claim 11, wherein the platform is connected to at least one of the primary structures.

15. The multirotor wind turbine according to claim 12, wherein the platform is connected to at least one of the secondary structures.

16. The multirotor wind turbine according to claim 15, wherein the upper interface connecting the at least one secondary structure to the load carrying hub forms part of the platform.

17. The multirotor wind turbine according to claim 13, wherein the platform is closer to one of the forward secondary structure and rearward secondary structure than to the other one of the forward secondary structure and rearward secondary structure.

18. The multirotor wind turbine according to claim 13, wherein one of the forward secondary structure and rearward secondary structure is connected to the platform and the other one of the forward secondary structure and rearward secondary structure is connected to the load carrying hub.

19. The multirotor wind turbine according to claim 13, wherein the platform is connected to both the forward secondary structure and to the rearward secondary structure.

20. The multirotor wind turbine according to claim 1, wherein at least the working surface of the platform is movable relative to the load carrying structure and fixed relative to the tower.

21. The multirotor wind turbine according to claim 1, wherein at least the working surface of the platform is fixed relative to the load carrying structure and movable relative to the tower.

22. The multirotor wind turbine according to claim 1, comprising electrical connection equipment located at the tower top beneath the platform.

23. The multirotor wind turbine according to claim 22, wherein the electrical connection equipment is located in the tower below or suspended on the side of the tower.

24. The multirotor wind turbine according to claim 1, wherein the rotor comprises a set of rotor blades and further comprising a rotor locking structure configured to lock rotation of the rotor in a position where one blade extends in a direction from the corresponding energy generating unit towards a lower surface of the platform.

25. The multirotor wind turbine according to claim 24, wherein locking structure is configured for coordinated locking of the rotor of two adjacent energy generating units in a position where at least one blade of each unit points towards a blade of the other unit.

26. A method of suspending a platform on a multirotor wind turbine, the wind turbine comprising: a tower extending in a vertical direction from a tower bottom to a tower top; a load carrying structure extending transverse to the vertical direction and arranged to carry at least two energy generating units, the load carrying structure being carried rotationally by the tower via a yaw arrangement; wherein the platform is arranged offset in a direction perpendicular to the vertical direction relative to the energy generating units.

27. The method according to claim 26, wherein the load carrying structure is provided with a first load carrying arrangement extending outwards on a left side of the tower and a second load carrying arrangement extending outwards on a right side of the tower, each load carrying arrangement comprising a primary structure extending from the tower towards a corresponding one of the at least two energy generating units, each load carrying arrangement is provided with a tension arrangement, the tension arrangement comprising at least one secondary structure extending above the primary structure between the tower and the corresponding one of the at least two energy generating units such that gravity acting on the energy generating units causes compression of the primary structure and tension in the at least one secondary structure, and the platform is connected to at least one of the secondary structures.

28. A method for bringing spare parts and personnel to and from a multirotor wind turbine according to claim 1, the method comprising landing a flying vehicle on the working surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The invention will now be described in further detail with reference to the accompanying drawings in which:

[0086] FIG. 1 is a front view of a multirotor wind turbine comprising two load carrying structures according to an embodiment of the invention,

[0087] FIG. 2 is a side view of the multirotor wind turbine of FIG. 1,

[0088] FIG. 3 is a top view of the multirotor wind turbine of FIGS. 1 and 2,

[0089] FIGS. 4-7 show details of different embodiments of the multirotor wind turbine,

[0090] FIG. 8 illustrates that the rotor planes are outside the contour of the platform, and

[0091] FIGS. 9-10 illustrate different properties of asymmetry between the platform and the tower top cross section.

DETAILED DESCRIPTION OF THE DRAWINGS

[0092] FIG. 1 is a front view of a multirotor wind turbine 1 comprising a tower 2 carrying two load carrying structures 3 according to an embodiment of the invention. The load carrying structures 3 are arranged, one above the other, along the length of the tower 2.

[0093] Each load carrying structure 3 comprises two load carrying arrangements 4, extending away from the tower 2 on opposite sides of the tower 2, as seen from the viewing angle of FIG. 1. Each load carrying arrangement 4 carries an energy generating unit 5, and each energy generating unit 5 comprises a nacelle 6 and a rotor 7 carrying three wind turbine blades 8.

[0094] Each load carrying arrangement 4 comprises a primary structure 9, in the form of a tube, and two secondary structures 10, in the form of double wires. In FIG. 1, only one of the secondary structures 10 for each load carrying arrangement 4 is visible.

[0095] The primary structures 9 extend away from the tower 2 along a direction which forms an acute angle with respect to a substantially vertical longitudinal axis defined by the tower 2. Thereby the primary structures 9 extend away from the tower 2 along an inclined upwards direction.

[0096] The secondary structures 10 extend away from the tower 2 along a direction which is substantially perpendicular to the substantially vertical longitudinal axis defined by the tower 2. Thereby the secondary structures 10 extend away from the tower 2 along a substantially horizontal direction. Accordingly, an angle is defined between the direction in which primary structure 9 of a given load carrying arrangement 4 extends, and the plane in which the secondary structures 10 of the load carrying arrangement 4 extend.

[0097] The primary structures 9 and the secondary structures 10 are attached to the tower 2 via a yaw arrangement 11, allowing the entire load carrying structure 3 to perform yawing movements with respect to the tower 2 in order to direct the rotors 7 into the incoming wind.

[0098] The multirotor wind turbine further comprising a platform 12 forming an upwards facing plane working surface

[0099] The primary structures 9 of a given load carrying structure 3 and the secondary structures 10 of the load carrying structure 3 are attached to the tower 2 at separate positions along the length of the tower 2.

[0100] When gravity acts on the energy generating units 5, the mutual positions of the primary structures 9 and the secondary structures 10 causes push in the primary structures 9 and pull in the secondary structures 10. Thereby a preload is introduced in the secondary structures 10, due to the gravity acting on the energy generating units 5.

[0101] During operation of the multirotor wind turbine 1, thrust forces will act on the energy generating units 5, in the direction of the incoming wind or in the opposite direction. When this occurs, the pull in one of the secondary structures 10 of each of the load carrying arrangements 4 is decreased while the pull in the other secondary structure 10 is increased. However, the preload introduced in the secondary structures 10, due to gravity acting on the energy generating units 5, is sufficiently high to ensure that the secondary structure 10, in which the pull is decreased, remains tight. Accordingly, the load carrying structure 1 is capable of handling the thrust forces introduced during operation of the multirotor wind turbine 1.

[0102] FIG. 2 is a side view of the multirotor wind turbine 1 of FIG. 1. It can be seen in FIG. 2 that the primary structures 9 extend from a position behind the tower 2 to a position in front of the tower 2, thereby positioning the rotors 7 of the energy generating units 5 in front of the tower 2, and facing the incoming wind.

[0103] It can further be seen that one of the secondary structures 10 of each load carrying arrangement 4 extends from an attachment point behind the tower 2 to the position of the energy generating unit 5. This will be described in further detail below with reference to FIG. 3.

[0104] FIG. 3 is a top view of the multirotor wind turbine 1 of FIGS. 1 and 2. In FIG. 3 it can be seen that the platform 12 is offset in horizontal direction relative to the rotor planes 19, i.e. it is located at a distance behind the rotor planes.

[0105] Each load carrying arrangement 4 comprises two secondary structures 10′, 10″ extending on opposing sides of the primary structure 9 from the position of the energy generating unit 5 to respective attachment points at the tower 2. This, combined with the fact that the primary structures 9 extend in an inclined upwards direction, as described above with reference to FIG. 1, has the consequence that the primary structure 9 and the secondary structures 10 of each load carrying arrangement 4 form a three-dimensional structure, which ensures that an appropriate preload is introduced in the secondary structures 10, due to gravity acting on the energy generating unit 5.

[0106] The working surface 17 of the platform 12 is made with an open structure allowing wind to blow through the surface. This improves the landing conditions for a vehicle.

[0107] For each load carrying arrangement 4, one of the secondary structures 10′, 10″ is attached to the tower 2 at a rearward point via the spacer 13 and via the platform 12 to which the spacer 13 is attached. In the illustrated embodiment, the platform is displaced rearward relative to the tower and it increases the distance from the tower 2 to the rearward secondary structure 10″. The other, forward, secondary structure 10′ is attached to the tower 2 via a forward point on the platform 12 at a position in front of the tower 2 and closer to the tower 2 than the rearward secondary structure 10″. As described above with reference to FIG. 2, the primary structure 9 extends from a position behind the tower 2 to a position in front of the tower 2. This allows the rotor 7 of each of the energy generating units 5 to be arranged in front of the tower 2, and in front of the primary structure 9 and both of the secondary structures 10. Thereby the wind turbine blades 8 are kept clear from not only the load carrying structure 3 but also from the platform 12, and the risk of collision is minimised.

[0108] FIG. 4 illustrates in further details the forward and rearward attachment points via the platform 12 to thereby provide an increased distance between the forward and rearward secondary structures 10′, 10″. The illustrated platform is plane had forms an outwards, and slightly downwards fence 14 making the working surface suitable for landing with a vehicle.

[0109] FIG. 5 illustrates an alternative embodiment of the wind turbine, where the platform includes an upwards fence 15 making the working surface suitable for personnel to work and receive objects which are hoisted down from a vehicle above the wind turbine. Again, the rearward secondary structure 10″ is attached to the tower 2 via a spacer 13 and via the platform 12, and the forward secondary structure 10′ is attached to the tower 2 via the platform 12.

[0110] FIG. 6 illustrates an alternative embodiment, wherein the working surface forms a landing surface for a vehicle. In this embodiment, the working surface is asymmetric relative to the tower top, i.e. it has a geometric centre which is offset in horizontal direction relative to tower. In the illustrated embodiment, the offset has a size whereby in such a way that the tower top is completely outside the outer contour of the working surface when seen in a top view in the direction from the tower top to the tower bottom. In this embodiment, the rearward secondary structure 10″ is fixed to, and extends below the working surface. The illustrated platform 12 includes a passage bridge 16 allowing access for personnel between the interior of the tower 2 and the working surface 17.

[0111] FIG. 7 illustrates further details of the passage bridge 16 and the entrance opening 18 allowing entrance from the access bridge 16 into the tower 2.

[0112] FIG. 8 illustrates a top view of an embodiment where the working surface 17 is offset in horizontal direction relative to the rotor planes 19 of the energy generating units 5 such that all rotor planes are at least partly outside the outer contour of the platform.

[0113] FIGS. 9 and 10 illustrate details of asymmetry between the tower cross section and the platform. Both FIG. 9 and FIG. 10 illustrate the wind turbine seen from above and FIG. 8 illustrates an embodiment where the contour of the platform 12 overlaps the contour of the tower top 2″. FIG. 9 illustrates an embodiment where the contour of the platform 12 does not overlap the contour of the tower top 2″.

[0114] The illustrated wind turbine has blades forming a rotor plane 20 by rotation of blades around the rotor axes 21, and in both embodiments the platform 12 is asymmetric in the direction away from the rotor planes 20, and in both embodiments, the platform 12 is completely within the borders defined on right and left sides by the rotor exes 21.

[0115] The platform 12 is asymmetric relative to the tower top 2″ which means that the geometrical centre of the platform 12 is shifted relative to the geometric centre of the cross section of the tower top.

[0116] In both FIGS. 9 and 10, a front point 22 of the outer periphery of the platform 12 is behind the corresponding front point 23 of the periphery of the tower top cross section in the direction of the arrow 24, i.e. in the direction from the rotor plane 20 along the rotor axes 21 and rearwards. The distance between the front points 22 and 23 in the direction of the arrow 24 could be anything above zero such as 10, 20, 30, 40, 50, 60 or more percent of the largest dimension of the platform.

[0117] An opposite asymmetry can also be applied, i.e. instead of the front point 22 of the outer periphery of the platform 12 being behind the corresponding front point 23 of the periphery of the tower top cross section in the direction of the arrow 24, the front point 22 of the outer periphery of the platform 12 is in front of the corresponding front point 23 of the periphery of the tower top cross section in the direction opposite the arrow 24. Again, the distance between the front points 22 and 23 in the direction opposite the arrow 24 could be anything above zero such as 10, 20, 30, 40, 50, 60 or more percent of the largest dimension of the platform.