Wind turbine nacelle structure

A wind turbine includes a nacelle which houses components including a generator connected to a rotor. The nacelle includes a cover and a skeleton, the skeleton including a plurality of connected elongated skeleton members. The skeleton members include a first skeleton member, a second skeleton member non-parallel to the first skeleton member, and a bolt extending in parallel with the second skeleton member for connecting the second skeleton member and the first skeleton member. Also, a method is presented for removing a component housed in a nacelle of a wind turbine, including disconnecting a second skeleton member from first skeleton members, removing the second skeleton member from a path of removal of the component, and removing the component along the path.

TECHNICAL FIELD

The invention relates to a wind turbine, in particular a horizontal axis wind turbine, comprising a nacelle, mounted on a tower, the nacelle housing components including a generator connected to a rotor, the nacelle comprising a cover and a skeleton, the skeleton comprising a plurality of connected elongated skeleton members. The invention also relates to a method for removing a component housed in a nacelle of a wind turbine.

BACKGROUND OF THE INVENTION

In the trend of wind turbine models growing in size, the design of the nacelles can creates challenges. In particular, the nacelle needs to be provided with a structure suited for carrying large loads, and also for facilitating service of parts in the nacelle.

WO2008000267A1 discloses a handling system for a wind turbine nacelle in connection with self-loading or self-unloading of the nacelle to or from a vehicle.

SUMMARY

It is an object of the invention to improve the structure of wind turbine nacelles. It is also an object of the invention to provide for a wind turbine nacelle to effectively carry loads, while also facilitating service of parts in the nacelle.

These objects are solved by a wind turbine comprising a nacelle, mounted on a tower, the nacelle housing components including a generator connected to a rotor of the wind turbine, the nacelle comprising a cover and a skeleton to which the cover is attached, the skeleton comprising a plurality of connected elongated skeleton members, the skeleton members comprising a first skeleton member and a second skeleton member being non-parallel to the first skeleton member, a bolt extending in parallel with the second skeleton member being provided for a connection between the second skeleton member and the first skeleton member. Preferably, the skeleton members are straight.

Thus, the second skeleton member can be connected to the first skeleton member with at least one bolt extending in parallel with the second skeleton member. The bolt connection provides for removal of the second skeleton member, e.g. for clearing the path for a component to be removed from the nacelle during a service operation. Also, the bolt extending in parallel with the skeleton member gives the possibility to provide pre-tension in the second skeleton member when mounting it to the first skeleton member, which is beneficial from a structural point of view.

Preferably, the bolt extends coaxially with the second skeleton member. Thereby, a pre-tension load provided by the bolt will be aligned with the second skeleton member, avoiding bending moments in the latter.

Preferably, the first skeleton member presents a contour with a concavity, the bolt, preferably the pin of the bolt, extending through the concavity. The contour with the concavity can for example be provided by a protruding ear of the first skeleton member. Thereby, the second skeleton member can be easily disassembled from the first skeleton member by loosening the bolt and moving the second skeleton member laterally so that the bolt pin leaves the concavity.

Preferably, the skeleton members comprise two parallel first skeleton members connected by at least one second skeleton member, the second skeleton member forming an angle to the first skeleton members which angle is larger than zero degrees and smaller than 90 degrees, preferably between 20 and 70 degrees, preferably between 30 and 60 degrees, preferably 45 degrees. Where the skeleton members comprise two parallel first skeleton members, these could be connected by at least two second skeleton members arranged in an X-shaped configuration. The two parallel first skeleton members could extend substantially in parallel to a rotational axis of the rotor, and preferably, as seen from above, on opposite sides of the rotational axis of the rotor.

The invention also provides a method for removing a component housed in a nacelle of a wind turbine, the nacelle being mounted on a tower, the nacelle comprising a cover and a skeleton to which the cover is attached, the skeleton comprising a plurality of connected elongated skeleton members, the skeleton members comprising a first skeleton member and a second skeleton member, the second skeleton member being connected to the first skeleton member, the second skeleton member being in a path of removal of the component, the method comprising disconnecting the second skeleton member from the first skeleton members, removing the second skeleton member from said path, and removing the component along said path. Thereby, a high degree of optimisation of the load carrying capacity of the nacelle structure can be obtained, while at the same time providing for good service solutions in relation to components in the nacelle.

Where the second skeleton member is, before being removed from said path, located above the component, removing the component along said path may comprise lifting the component by means of a crane. The first skeleton members could extend in parallel to each other and substantially in parallel to a rotational axis of a rotor of the wind turbine, and, as seen from above, on opposite sides of the rotational axis of the rotor. Thereby the component could be removed along said path between the first skeleton members.

The method could further include, for example at the end of a service procedure, introducing the component or another component along said path, into the nacelle, and connecting the second skeleton member to the first skeleton members.

DETAILED DESCRIPTION

FIG. 1shows a horizontal axis wind turbine1comprising a nacelle2, mounted on a tower3. The nacelle2has a cover21and houses components including a generator connected to a rotor4, which in this example comprises three blades41.

FIG. 2shows a skeleton22of the nacelle2. The cover21inFIG. 1is mounted to the skeleton22, which comprises a plurality of connected elongated straight skeleton members. The skeleton members comprise first skeleton members221and second skeleton members222. The first skeleton members221are connected to each other, e.g. by bolting or welding.

FIG. 3shows how four second skeleton members222are mounted to two parallel first skeleton members221such that the second skeleton members222are non-parallel to the first skeleton members221. More particularly, the second skeleton members222form 45 degree angles A to the first skeleton members221. The four second skeleton members222are at respective ends thereof mounted by bolting or welding to a central bracket223. At opposite respective ends the second skeleton members222are mounted to the first skeleton members221. Thereby, the second skeleton members222are arranged in an X-shaped configuration. The two first skeleton members221extend in parallel to, and on opposite sides of, a rotational axis B, (indicated with a broken line), of the rotor4, (FIG. 1), of the wind turbine.

FIG. 4andFIG. 5show how each of the second skeleton members222are connected to one of the first skeleton members221with a bolt224extending in parallel with the respective second skeleton member222. The bolt224extends coaxially with the second skeleton member222. The first skeleton member221presents a protruding planar ear225, which is supported at its distal end by a support element226, such that the ear forms a 45 degree angle to the longitudinal direction of the first skeleton member221. As can be seen inFIG. 4, the ear225presents a contour with a concavity227, and the pin of the bolt224extends through the concavity227.

The head of the bolt rests against the ear225via an intermediate washer, and its threaded pin extends through the concavity227into a female thread in the second skeleton member222. The second skeleton members222are slightly shorter than what is needed to extend between the ears225of the first skeleton members221. By turning the bolts224, while holding the second skeleton members222with a suitable tool at flattened portions2221to prevent their rotation, the second skeleton members222can be pre-tensioned during their installation. This is beneficial from a structural point of view. Also, the fact that the bolts224extend coaxially with the second skeleton members222, the pre-tension load provided by the bolts224will be aligned with the second skeleton members222, avoiding bending moments in the latter.

FIG. 6shows an alternative embodiment of the invention, in which two second skeleton members222are mounted to two parallel first skeleton members221, thereby forming an X-shaped configuration. For this the ears225are arranged so that the two second skeleton members222are offset in a vertical direction.

FIG. 7shows a further alternative embodiment of the invention, in which only one second skeleton member222is mounted between two parallel first skeleton members221.

FIG. 8andFIG. 9illustrate an embodiment of a method for removing a component housed in the nacelle2of the wind turbine described above with reference toFIG. 1toFIG. 5. As can be seen inFIG. 8, the rotor4is connected to components in the nacelle2in the form of a main shaft51, a gear box52, and a generator53. It can be seen that the generator53is located under the second skeleton members222. Thereby, the second skeleton members222are in a path of removal of the generator53for service purposes.

As illustrated inFIG. 9, the method comprises opening a door23of a roof hatch of the nacelle, and disconnecting the second skeleton members222from the first skeleton members221. This disconnection is done by loosening the bolts224, (FIG. 4andFIG. 5), and lifting them out of the concavities227of the ears225of the first skeleton members221. Thereafter the second skeleton members222are removed with the central connecting bracket223, as illustrated with the arrow I inFIG. 9. Thereby said path is cleared for removing for service purposes the generator53. The generator53is removed from the nacelle2along said path by lifting with the aid of a crane6, as illustrated by the arrow II.

Thus, the connections with bolts224and ear concavities227provide for easy removal of the second skeleton members222, for clearing the path for a component53to be removed from the nacelle during a service operation. Thereby, a good service solution for components in the nacelle is provided by removing the second skeleton members, which nevertheless can form an essential part of the load carrying nacelle structure during normal wind turbine operation. At the end of a service procedure, the component53or a replacement component could be introduced along said path, back into the nacelle, and the second skeleton members222could be reconnected to the first skeleton members221.