Patent ID: 12258935

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS.1-3illustrate a pitch controlled wind turbine1according to a first embodiment of the invention.FIG.1is a front view of the wind turbine1,FIG.2is a side view of the wind turbine1, andFIG.3shows a detail of the wind turbine1.

The wind turbine1comprises a tower2, a nacelle3mounted on the tower2and a hub4mounted on the nacelle2. Three wind turbine blades5are connected to the hub4. Each wind turbine blade5extends between a root end6connected to the hub4and an oppositely arranged tip end7.

The wind turbine1further comprises three blade connecting members8. Each blade connecting member8interconnects two neighbouring wind turbine blades5by being connected to connection points9at the respective wind turbine blades5. The wind turbine blades5are able to mutually support each other via the blade connecting members8, in the sense that loads on the wind turbine blades5, in particular edgewise loads and flapwise loads, are shared among the wind turbine blades5, via the blade connecting members8. In particular, the loads at the part of the wind turbine blade5which is arranged between the root end6and the connection point9are reduced due to the presence of the blade connecting members8.

Each wind turbine blade5comprises an inboard blade part5acomprising the root end6, and an outboard blade part5bcomprising the tip end7. The inboard blade part5aand the outboard blade part5bare connected to each other at a split position10, i.e. the wind turbine blade5is a so-called ‘split blade’. Thereby the inboard blade part5aand the outboard blade part5bmay be manufactured separately and transported separately to a site of the wind turbine1, and the inboard blade part5aand the outboard blade part5bmay be assembled to form the wind turbine blade5at the site of the wind turbine1. Accordingly, the length of the wind turbine blade5is allowed to exceed a maximum length which is dictated by transport requirements.

The split position10is arranged between the root end6and the connection point9, i.e. the point where the blade connecting members8are connected to the wind turbine blade5. Thus, the split position10is arranged in the part of the wind turbine blade5where a significant load reduction, due to the blade connecting members8, is expected. It may therefore be expected that the wind turbine blade5will be able to handle the loads occurring during operation of the wind turbine1, despite the weakness in the wind turbine blade5which is introduced by splitting the wind turbine blade5.

Furthermore, arranging the split position10in this part of the wind turbine blade5allows the split position10to be easily accessible from the hub4.

FIGS.4and5illustrate a pitch controlled wind turbine1according to a second embodiment of the invention.FIG.4is a front view of the wind turbine1andFIG.5shows a detail of the wind turbine1.

The wind turbine1ofFIGS.4and5is very similar to the wind turbine1ofFIGS.1-3, and it will therefore not be described in detail here.

The wind turbine1ofFIGS.4and5further comprises three pre-tension members11. Each pre-tension member11is connected to one of the blade connecting members8, approximately half way between the connection points9at the wind turbine blades5, and to the hub4. Thus, the pre-tension members11pull the blade connecting members8towards the hub4, thereby providing pre-tension in the blade connecting members8.

The pre-tension in the blade connecting members8can thereby by adjusted by means of the pre-tension members11, and thereby controlling to which extend the wind turbine blades5support each other via the blade connecting members8.

Blade connecting members8may be comprise one or more sub parts, such as for example two sub parts or sections. This is particularly advantageous when the wind turbine comprises pre-tension member. Here, the connecting member8may for example and preferably comprising two sub sections, where each section is connecting a blade connection point to a connector element (not shown) to which connector element the pre-tension member is also connected. This allows for a safe and centred connection between the connecting members and the pre-tension member.

FIGS.6and7illustrate a pitch controlled wind turbine1according to a third embodiment of the invention.FIG.6is a front view of the wind turbine1andFIG.7shows a detail of the wind turbine1.

The wind turbine1ofFIGS.6and7is very similar to the wind turbine1ofFIGS.1-3, and it will therefore not be described in detail here.

In the wind turbine1ofFIGS.6and7each wind turbine blade5further comprises an intermediate blade part5carranged between the inboard blade part5aand the outboard blade part5b. The inboard blade part5aand the intermediate blade part5care connected to each other at a first split position10a, and the intermediate blade part5cand the outboard blade part5bare connected to each other at a second split position10b. Thus, each wind turbine blade5is split into three blade parts5a,5b,5c, and defines two split positions10a,10b. Both split positions10a,10bare arranged between the root end6and the connection point9, i.e. in the part of the wind turbine blade5where the load reduction caused by the support provided by the blade connecting members8is expected to be most significant. In another example (not shown) the blade connection point is on the intermediate blade part5c. The blade connection point may be on the inboard blade part5a, but this is not preferred as the load carried by the connecting members will be relatively low.

Splitting the wind turbine blades5into three parts allows for even longer wind turbine blades5without coming into conflict with transport constraints. Furthermore, this allows a modular design of the wind turbine1, in the sense that the rotor diameter of the wind turbine1can be varied by appropriately selecting the length of the intermediate blade part5c, without changing the design of the inboard blade part5aand the outboard blade part5b.

FIG.8is a perspective view of a wind turbine blade5for a wind turbine according to an embodiment of the invention. The wind turbine blade5comprises an inboard blade part5aand an outboard blade part5bconnected to each other at a split position10, as described above with reference toFIGS.1-3.

The inboard blade part5aand the outboard blade part5bare connected to each other via a pitch bearing12. Thereby the outboard blade part5bis able to perform pitching movements relative to the inboard blade part5a, i.e. to perform partial pitch.

FIG.9is a side view of a wind turbine blade5for a wind turbine according to an alternative embodiment of the invention. The wind turbine blade5comprises an inboard blade part5aand an outboard blade part5bconnected to each other at a split position10.

The inboard blade part5acomprises a first inboard blade part5a′ and a second inboard blade part5a″. The first inboard blade part5a′ comprises a leading edge13of the inboard blade part5a, and the second inboard blade part5a″ comprises a trailing edge14of the inboard blade part5a.

The first inboard blade part5a′ and the second inboard blade part5a″ are connected to each other along a split interface15which extends substantially along a direction defined by the length of the wind turbine blade5, and substantially perpendicularly to the transverse split interface between the inboard blade part5aand the outboard blade part5bat the split position10. Thus, the wind turbine blade5illustrated inFIG.9is split into three parts, i.e. the first inboard blade part5a′, the second inboard blade part5a″ and the outboard blade part5b. Here, the blade connection point is preferably on the first inboard blade part5a′ or the outboard part5bincluding in the split position.

The chord of the wind turbine blade5is larger in the inboard blade part5athan in the outboard blade part5b. By splitting the inboard blade part5ainto the first inboard blade part5a′ and the second inboard blade part5a″, it can be obtained that none of the blade parts5a′,5a″,5bhas a width which exceeds maximum transporting constraints.

FIG.10is a perspective view of part of a wind turbine blade5for a wind turbine according to an embodiment of the invention. More particularly,FIG.10shows a part of the wind turbine blade5which comprises the connection point9, i.e. the position where blade connecting members8are connected to the wind turbine blade5.

The blade connecting members8are connected to the wind turbine blade5via a bearing structure16. This allows the wind turbine blade5to perform pitching movements without affecting the blade connecting members8. Thereby it is avoided that undesired loading, twist or tension is applied to the blade connecting members8during pitching of the wind turbine blade5.

FIGS.11and12illustrate two different bearing structures16for connecting a blade connecting member to a wind turbine blade for a wind turbine according to an embodiment of the invention. For instance, the bearing structures16ofFIGS.11and12may each be applied in the wind turbine blade illustrated inFIG.10.

Plate-like structure17is attached to the wind turbine blade.FIGS.11and12illustrate two different structures for providing this attachment.

The blade connecting members are attached to an eyelet18which is mounted rotatably on the plate-like structure17, thereby allowing the wind turbine blade, with the plate-like structure17attached thereto, to perform pitching movements relative to the eyelet18, and thereby relative to the blade connecting members connected thereto.