DESC:TRANSITION PIECE FOR A HYBRID TOWER OF A WIND TURBINE, A HYBRID TOWER AND A WIND TURBINE

TECHNICAL FIELD

The invention relates to components of a wind turbine, and more particularly to a transition piece for a hybrid tower of a wind turbine, a hybrid tower and a wind turbine.

BACKGROUND

It is known to use in a wind turbine a hybrid tower, wherein a lower portion of the hybrid tower is designed as a lattice tower and an upper portion of the tower as a tube tower. The lattice tower and the tube tower are releasably connected to one another by means of a transition piece. The transition piece includes an adapter shell and a plurality of adapter plates, the adapter shell and the adapter plates are connected to each other, so that the adapter plates and the adapter cup partly overlap in the longitudinal direction of the tower. The adapter plates connect the transition piece with corner posts of the lattice tower and an adapter shell connects the tube tower with the transition piece, so that the forces and moments of the tube tower are controllably transferred to the lattice tower over the transition piece.

However, it has been found that with this known design, problems arise. That is, the existing transition piece (also referred to as “adapter”) consists of a cylindrical part and a conical part, which leads to high stress concentrations at the transition point between the conical and cylindrical part. In addition, a reinforcing rib has to be arranged at the transition point to prevent bulging problems and to reduce stress concentration. However, the reinforcing rib cannot be positioned optimally directly at the transition point between conical and cylindrical sections, as this would lead to an unfavorable welding seam constellation, which is to be avoided. The reinforcing rib therefore has to be positioned in a slightly unfavorable manner below the transition area from conical to cylindrical. This suboptimal design leads to the requirement for elaborate grinding/sanding of the welding seam in the transition area between the conical and cylindrical area in order to ensure sufficient fatigue strength.

OBJECTIVE OF THE INVENTION

The present invention seeks to overcome the aforementioned problems and to provide an improved transition piece for a hybrid tower of a wind turbine, a hybrid tower and a wind turbine.

SUMMARY

According to one aspect of the invention there is provided a transition piece for a hybrid tower of a wind turbine, a lower portion of the hybrid tower being a lattice tower and an upper portion of the hybrid tower being a tube tower. The transition piece comprises an adapter shell, the adapter shell being hollow and including an upper portion to which, in use, the tube tower is attached. The transition piece further comprises a plurality of adapter plates, the adapter shell and the adapter plates being connected to each other, whereby, in use, the adapter plates and the adapter shell partly overlap in the longitudinal direction of the hybrid tower. The transition piece is characterized in that the adapter shell is of substantially conical cross section.

Thus, at least in embodiments, a key element is to realise the transition between conical and cylindrical sections not in the transition piece itself, but in the parting line between transition piece and tube tower. Also, by shifting the transition point, stress concentration in the welding seam is reduced to such an extent that grinding/sanding of the welding seam can be omitted.

Preferably, the adapter shell is, at least at said upper portion, of conical cross section.

Preferably, the adapter shell is entirely of conical cross section.

Preferably, the adapter shell includes, at the upper portion, a circumferential flange. Preferably, the circumferential flange comprises, in cross-section, a first limb extending transversely to the axis of the adapter shell and a second limb extending so as to define an angle relative to the axis corresponding to a cone angle of the adapter shell. Preferably, the second limb extends so as to be aligned with a conical wall, when viewed in transverse cross-section, of the adapter shell. Thus, at least in embodiments, a flange of the transition piece has on the outside the same inclination (angle) as the conical adapter shell. As the conical flange itself is very stiff, a (second or nearby) reinforcement rib is not required.

In one embodiment, the circumferential flange is integrally formed with the adapter shell.

In another embodiment, the circumferential flange is releasably attached to the adapter shell.

Preferably, the first limb is configured to abut and support, in use, a circumferential base portion of the tube tower.

Preferably, the adapter shell includes, at a lower portion thereof, a reinforcing rib.

Preferably, the adapter shell includes the circumferential flange, the reinforcing rib and no other reinforcing elements.

Preferably, the stiffening rib is releasably connected to a cross member via at least one spacer.

Preferably, the adapter shell is so divisible along the axis, so that respective parts of the adapter shell, in at least one direction, do not exceed a width of about 4.3 meters.

According to another aspect of the invention there is provided a hybrid tower for a wind turbine, a lower portion of the hybrid tower being a lattice tower and an upper portion of the hybrid tower being a tube tower, the tube tower and the lattice tower being fixedly connected by said transition piece.

According to another aspect of the invention there is provided a wind turbine comprising a nacelle housing a bearing assembly and a rotor shaft rotatable about an axis within the bearing assembly, the nacelle being mounted on said hybrid tower.

An advantage of the invention is that the new transition piece in fully conical design allows reduction of the weight of the transition piece as the cylindrical part is no longer present. Also, grinding/sanding of the welding seam between cylindrical and conical dish is no longer necessary, as with the disclosed design there are no stress peaks in the welding seam due to geometry. Further, a horizontal reinforcing rib is no longer required. These measures not only achieve a reduction in weight, but also manufacturing is facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention will become apparent from the drawings according to the description. In the drawings:

FIG. 1 (PRIOR ART) is a lateral view of a known hybrid tower;

FIG. 2 (PRIOR ART) is a perspective view from above of the upper part of a wind turbine using the known form of hybrid tower of Fig. 1;

FIG. 3 (PRIOR ART) is an external view of the transition piece used in the hybrid tower of Fig. 1, when mounted to a lattice tower;

Fig. 4 (PRIOR ART) shows (a) an external view of the known adapter shell of Fig. 1, in isolation, (b) a transverse cross-sectional view of the known adapter shell of Fig. 4(a), (c) the detail at B in Fig. 4(b), (d) the detail at G in Fig. 4(b) and (e) the detail at F in Fig. 4(b); and

Fig. 5 shows (a) an external view of an adapter shell for a transition piece according to an embodiment of the invention, in isolation, (b) a transverse cross-sectional view of the adapter shell of Fig. 5(a), (c) the detail at E in Fig. 5(b) and (d) the detail at F in Fig. 5(b).

DETAILED DESCRIPTION

In the following, like reference numerals are used to designate like elements.

FIG. 1 (PRIOR ART) is a lateral view of a known hybrid tower, wherein an upper section of the hybrid tower 11 is formed as a tube tower 3 and a lower section is formed as a lattice tower 12.

Referring briefly to FIG. 2 (PRIOR ART), this is a perspective view from above of the upper part of a wind turbine using the known form of hybrid tower of Fig. 1. Fig. 2 shows a wind turbine 2 with a tube tower 3 known from the prior art, a nacelle 4 mounted on the tower 3 and a rotor 5 with a hub 8 and three rotor blades 6 which are each rotatably mounted about a blade axle. The hub 8 is mounted on a rotor shaft which is rotatably mounted in the nacelle 4. According to this embodiment, the tube tower 3 is formed of multiple tube segments 16.

Returning to Fig. 1, the tube tower 3 and the lattice tower 12 are connected to each other via a transition piece 1. The lattice tower 12 comprises at least three, in this embodiment four, corner posts 13 which are connected to each other via a number of cross members 14 and cross braces 15. The corner posts 13 are configured to remove the bending moments acting perpendicular to the tower axis 7 and to remove forces acting in the tower axis 7. The cross braces 15 of the lattice tower 12 are configured to remove torsional moments acting around the tower axis and forces acting perpendicular to the tower axis 7. The corner posts are arranged at a tilting angle to the tower axis. The tube tower 3 is connected to the lattice tower 12 via the transition piece 1. For the tube tower 3 existing tube segments 16 from the known tube tower 3 can be used, e.g. here, the two upper segments 16 of the known tube tower 3 are used. The transition piece 1 is arranged at the height of the tip of the rotor blade 6 in the deepest position. Thus, the hybrid tower 11 is very slim in the area of the rotor 5 such that it is ensured that the rotor blades 6 can rotate from the hybrid tower 11 even if they are strongly bent. Below the rotor 5 the width of the lattice tower 12 can freely increase such that a large footprint and thus a stable standing of the hybrid tower 11 is ensured.

FIG. 3 (PRIOR ART) is an external view of the transition piece 1 used in the hybrid tower of Fig. 1, when mounted to a lattice tower 12. The transition piece 1 consists of an adapter shell 17’ and several adapter plates 18. The number of adapter plates 18 corresponds to the number of corner posts 13 of the lattice tower 12, in this case four. In this embodiment the adapter shell 17’ is formed partly conical, the cone angle aSchale of the adapter shell 17’ corresponds to the tilting angle aStiel of the corner posts 13. Due to the partially conical form of the adapter shell 17’ the adapter plate 18 can be compact and vertical forces and bending torques can mainly be transferred via pressure from the adapter shell 17’ at the corner posts 13 of the lattice tower 12. The offset moments resulting from the offset d between adapter shell 17’ and corner post 13 remain low. Production of the adapter plate is relatively easy for an adapter shell 17’ as the adapter plate 18 does not have to compensate the tilting difference between adapter shell 17’ and corner post 13. An upper section of the adapter shell 17’ in the area of the connection to the tube tower 3 has a cylindrical form; this is designed to ensure an easier assembly and better distribution of forces and moments from the tube tower 3. In order to use the maximum transporting diameter for the tube tower 3, the adapter shell 17’ is here split. The diameter of the lower area of the adapter shell 17’ can thus exceed in mounted condition the maximum transporting diameter. During transport the parts of the adapter shell 17’ are dismantled, so that the width to be transported is reduced. The parts of the adapter shell 17’ are here connected to each other via a screwed fishplating 20. The adapter plates 18 are detachably connected to the adapter shell 17’ via fasteners 19; here the fasteners 19 are screw connections.

Fig. 4(a) (PRIOR ART) shows an external view of the known adapter shell 17’ of Fig. 1, in isolation. As can be seen, the adapter shell 17’ comprises a lower conical section 40’ and an upper cylindrical section 42, a weld or seam 46 being formed therebetween. At an upper portion 41’ of adapter shell 17’ is provided a circumferential flange 44‘, on which the tube tower (not shown; see Fig. 1) is supported and connected.

Fig. 4(b) (PRIOR ART) shows a transverse cross-sectional view of the known adapter shell 17’ of Fig. 4(a).

Fig. 4(c) (PRIOR ART) shows the detail at B in Fig. 4(b), showing the circumferential flange 44’ disposed at the upper portion 41’; for example, a lower point on the circumferential flange 44’ abuts an upper surface of cylindrical section 42. It can be seen that, peripherally and when viewed in cross-section, the circumferential flange 44’ includes a transversely extending first limb 43’ and second limb 45’ extending parallel to the axis of the adapter shell 17’ and tower. That is, the circumferential flange 44’ has an „L“ shaped configuration.

Fig. 4(d) (PRIOR ART) shows the detail at G in Fig. 4(b). As illustrated, an upper reinforcing rib 22c is provided in the vicinity of the weld 46 between the conical section 40’ and the cylindrical section 42.

Fig. 4(e) (PRIOR ART) shows the detail at F in Fig. 4(b). As illustrated, a lower reinforcing rib 22a is provided spaced apart from the weld 46 and part way down the conical section 40’.

However, with the design of Figs 1-4, the aforementioned problems arise. That is, the existing transition piece 1’ consists of a cylindrical part 42 and a conical part 40’, which leads to high stress concentrations at the transition point 46 between the conical part 40’ and cylindrical part 42. In addition, a reinforcing rib 22c has to be arranged at the transition point 46 to prevent bulging problems and to reduce stress concentration. However, the reinforcing rib 22c cannot be positioned optimally directly at the transition point 46 between conical 40’ and cylindrical 42 sections, as this would lead to an unfavorable welding seam constellation, which is to be avoided. The reinforcing rib 22c therefore has to be positioned in a slightly unfavorable manner below the transition area 46 from conical to cylindrical. This suboptimal design leads to the requirement for elaborate grinding/sanding of the welding seam in the transition area between the conical and cylindrical area in order to ensure sufficient fatigue strength.

Fig. 5 shows (a) an external view of an adapter shell 17 of a transition piece 1 according to an embodiment of the invention, in isolation, (b) a transverse cross-sectional view of the adapter shell 17 of Fig. 5(a), (c) the detail at E in Fig. 5(b) and (d) the detail at F in Fig. 5(b). The construction is as set out in respect of Figs 1 to 4, except as described otherwise hereinafter. All components are formed of high strength steel, unless stated otherwise.

As can be seen in Fig. 5(a), the adapter shell 17 comprises a purely conical section 40. At an upper portion 41 of adapter shell 17 is provided a circumferential flange 44, on which the tube tower (not shown; see Fig. 1) is supported and connected. In embodiments, the section 40 is substantially conical and/or has a conical form at least at the upper portion 41.

Fig. 5(b) shows a transverse cross-sectional view of the adapter shell 17 of Fig. 5(a).

Fig. 5(c) shows the detail at E in Fig. 5(b), showing the circumferential flange 44 disposed at the upper portion 41; for example, a lower point on the circumferential flange 44 abuts an upper surface of conical section 40. It can be seen that, peripherally and when viewed in cross-section, the circumferential flange 44 includes a transversely extending first limb 43 and second limb 45 extending at a conically tapering angle to the axis of the adapter shell 17 and tower. That is, the second limb 45 extends in a direction aligned with the wall of the conical section 40 of the adapter shell 17.

Fig. 5(d) shows the detail at F in Fig. 5(b). As illustrated, a single reinforcing rib 22 is provided spaced apart from the upper portion 41 of the conical section 40.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It is to be understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.

List of reference signs

1 transition piece
2 wind turbine
3 tube tower
4 nacelle
5 rotor
6 rotor blade
7 tower axis
8 hub
11 hybrid tower
12 lattice tower
13 corner post
14 cross member
15 cross brace
16 tube segment
17/17’ adapter shell
18 adapter plate
19 fastener
20 fishplating
22 reinforcing rib
22a lower reinforcing rib
22b stiffening rib
22c upper reinforcing rib
32 spacer
40/40’ conical section
41/41’ upper portion
42 cylindrical section
43/43’ first limb
44/44’ circumferential flange
45’ second limb
46 weld / seam
,CLAIMS:We claim:
1. A transition piece (1) for a hybrid tower (11) of a wind turbine (2), a lower portion of the hybrid tower (11) being a lattice tower (12) and an upper portion of the hybrid tower (11) being a tube tower (3), the transition piece (1) comprising:

- an adapter shell (17), the adapter shell being hollow and including an upper portion (41) to which, in use, the tube tower (3) is attached;

- a plurality of adapter plates (18), the adapter shell (17) and the adapter plates (18) being connected to each other, whereby, in use, the adapter plates (18) and the adapter shell (17) partly overlap in the longitudinal direction of the hybrid tower (11);

characterized in that the adapter shell (17) is of substantially conical cross section.

2. A transition piece (1) according to claim 1 characterized in that the adapter shell (17) is, at least at said upper portion (41), of conical cross section.

3. A transition piece (1) according to claim 1 characterized in that the adapter shell (17) is entirely of conical cross section.

4. A transition piece (1) according to claim 1, 2 or 3 characterized in that the adapter shell (17) includes, at the upper portion (41), a circumferential flange (44).

5. A transition piece (1) according to claim 4 characterized in that the circumferential flange (44) comprises, in cross-section, a first limb (43) extending transversely to the axis of the adapter shell (17) and a second limb (45) extending so as to define an angle relative to the axis corresponding to a cone angle of the adapter shell (17).

6. A transition piece (1) according to claim 5 characterized in that the second limb (45) extends so as to be aligned with a conical wall, when viewed in transverse cross-section, of the adapter shell (17).

7. A transition piece according to claim 4, 5 or 6 characterized in that the circumferential flange (44) is integrally formed with the adapter shell (17).

8. A transition piece (1) according to claim 4, 5 or 6 characterized in that the circumferential flange (44) is releasably attached to the adapter shell (17).

9. A transition piece (1) according to claim 5, or any claim dependent thereon, characterized in that the first limb (43) is configured to abut and support, in use, a circumferential base portion of the tube tower (3).

10. A transition piece (1) according to claim 4, or any claim dependent thereon, characterized in that the adapter shell (17) includes, at a lower portion thereof, a reinforcing rib (22).

11. A transition piece (1) according to claim 10 characterized in that the adapter shell (17) includes therein the circumferential flange (44), the reinforcing rib (22) and no other reinforcing elements.

12. A transition piece (1) according to any of the preceding claims, characterized in that the stiffening rib (22b) is releasably connected to a cross member (14) via at least one spacer (32).

13. A transition piece (1) according to claim 10 or 11, characterized in that the adapter shell (17) is so divisible along the axis (7), so that respective parts of the adapter shell (17), in at least one direction, do not exceed a width of about 4.3 meters.

14. A hybrid tower (11) for a wind turbine (2), a lower portion of the hybrid tower (11) being a lattice tower (12) and an upper portion of the hybrid tower (11) being a tube tower (3), the tube tower (3) and the lattice tower (12) being fixedly connected by a transition piece (1) according to any of claims 1 to 13.

15. A wind turbine (2) comprising a nacelle (4) housing a bearing assembly and a rotor shaft rotatable about an axis within the bearing assembly, the nacelle being mounted on the hybrid tower (11) according to claim 14.