Patent Publication Number: US-2012045321-A1

Title: Wind turbine nacelle

Description:
FIELD OF THE INVENTION 
     The present invention relates to a nacelle for a wind turbine, the nacelle having a first height in its installed position and a second height in its transported position, the first height being higher than the second height, comprising a bottom part having a bottom face and two opposite side faces defining a space and a width of the bottom part and a top part. 
     BACKGROUND ART 
     Transportation of large elements on a truck requires special transport equipment in order to adjust the truck to suit the particular element to be transported. Furthermore, national regulations of a country or a state may require that the transport does not exceed a certain height or a certain weight. 
     In many countries in Europe and in USA, a certain overall height has been specified which a truck including an element may not exceed. In order to comply with these regulations, special transport equipment enabling the element to be transported on a platform lowered down between a front part of a truck and a rear part of a truck may be required. 
     Even though the transport equipment is designed to minimise the overall height, the overall height of the element and the transport equipment may for some elements, such as a large wind turbine nacelle, still be too high. In such cases, the element has to be transported in two or more parts and, thus, assembled when arriving at its destination. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is, at least partly, to overcome the above disadvantages and drawbacks of the prior art and to provide an improved nacelle for a wind turbine which is easier to transport, even if the nacelle is a large nacelle. 
     The above object, together with numerous other objects, advantages, and features, which will become evident from the below description, is accomplished by a solution in accordance with the present invention by a nacelle for a wind turbine having a first height in its installed position and a second height in its transported position, the first height being higher than the second height, comprising a main frame structure, a bottom part connected to the main frame structure and having a bottom face and two opposite side faces defining a space and a width of the bottom part and a top part, wherein the top part in the transported position extends inside the width or outside the width in order to cover at least part of the space. 
     In this way, the top part can be used to cover the bottom part during transport so as to prevent dirt etc. from entering the bottom part from above. In addition, no separate vehicle is needed to transport the top part, as both the top part and the bottom part can be transported on one vehicle when the height of the nacelle is adjustable. 
     In one embodiment, the top part may comprise two parts which in the transported position of the nacelle are separated from each other in order for the top part to extend outside the width of the nacelle or overlap each other in order for the top part to extend inside the width of the nacelle. 
     It is thus not necessary to press the side faces towards or away from each other in order to minimise the height of the nacelle during transport. Furthermore, the top part does not get scratched during insertion of the top part between the side faces. 
     The top part may moreover comprise a top face and two intermediate parts intermediate the side faces and the top face, which two intermediate parts are dismounted in the transported position. 
     In an alternative solution according to the invention, the nacelle may have a first height in its installed position and a second height in its transported position, the first height being higher than the second height, the nacelle comprising a main frame structure, a bottom part connected to the main frame structure and having a bottom face and two opposite side faces defining a space and a width of the bottom part and a top part. In this solution, the top part may comprise a top face and two intermediate parts intermediate the side faces and the top face, the intermediate parts being dismounted in the transported position and the top face being arranged on the side faces of the bottom part in order to cover at least part of the space. 
     Thus, the top face can easily be arranged inside the width of the bottom part, and the intermediate parts can be placed within or outside the nacelle during transport. 
     The transportation height of the nacelle may be equal to or lower than 4 metres, preferably 3.9 metres, more preferably 3.3 metres. 
     Thus, the maximum height of the nacelle during transport complies with the maximum height for passing under bridges and through tunnels etc. specified by a number of European countries and in USA. 
     Moreover, the nacelle may further comprise a main frame structure arranged so that at least part of the top part can be supported by the main frame structure during transport. 
     The main frame structure may thus support the top part of the nacelle when the top part extends inside the width of the bottom part of the nacelle. 
     In one embodiment, the main frame structure may comprise at least two support beams arranged along each side face. 
     Thus, the top part of the nacelle may be supported along its longitudinal extension, preferably along its entire longitudinal extension. 
     In addition, the nacelle may comprise at least one connection part for connecting the top part to the bottom part, the connection part being substantially inside the nacelle in its installed position. 
     The connection part may be a detachable part so that it can be removed and used as support for at least part of the top part in the transported position. 
     The nacelle may moreover comprise a transport kit having transportation parts for enabling a cover of the space during transport. 
     In one embodiment, the transportation parts may be arranged partly inside the nacelle during transport to provide a support of at least part of the top part. 
     Thus, if it is not possible to place the top part so that it covers the space within the bottom part of the nacelle, the transportation parts can be used to prolong the top part to the sides and at the front and back ends, thus sealing off the space. 
     In a further embodiment, the transportation parts may comprise sealing means. 
     Thus, the transportation parts may facilitate a waterproof connection between the top part and the main frame structure within the bottom part of the nacelle. 
     The nacelle may further comprise a plurality of rafters. 
     In one embodiment, some of the rafters may be adjustable in height. 
     When the height of the rafters is adjustable, the rafters can be used to support the top part during transport by lowering the height of the rafters, thus also lowering the height of the nacelle. 
     In addition, the nacelle may further comprise detachable end faces. 
     When the end faces are detachable, they may be manufactured in one piece, thus making them more rigid and adding greater stability to the nacelle. During transport, the detachable end faces may be placed inside the nacelle, end to end with the nacelle, or askew so as to comply with the requirements concerning maximum transportation height. 
     However, the detachable end faces may also be a part of the front or back ends of the nacelle. 
     In one embodiment, part of the intermediate part may overlap a predetermined part of the top face in the installed position whereas, in the transported position, the intermediate part overlaps a lesser part of the top face than the predetermined part. 
     Thus, the top part can be prolonged to the sides during transport while still having sealing ability as the intermediate part and the top face still overlap. 
     The invention also relates to a transport method for transporting a nacelle as described above, the method comprising the step of placing at least part of the top part in a transported position in which part of the top part overlaps part of the side faces of the bottom part. 
     In addition, the transport method may further comprise the step of placing intermediate parts and/or connection parts inside the space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings which, for the purpose of illustration, show some non-limiting embodiments and in which 
         FIG. 1  shows a wind turbine nacelle according to the invention in its installed position, 
         FIG. 2  shows the nacelle of  FIG. 1  where the top part of the nacelle cover has been dismounted, 
         FIG. 3  shows the nacelle of  FIG. 1  in its transported position, 
         FIG. 4  shows a transportation kit, 
         FIG. 5  shows a cross-sectional view of the wind turbine nacelle in its transported position, 
         FIG. 6  shows a sectional view of  FIG. 5 , 
         FIG. 7  shows a cross-sectional view of the wind turbine nacelle in its installed position, 
         FIG. 8  shows a sectional view of  FIG. 7 , 
         FIG. 9  shows a sectional view of another embodiment of the wind turbine nacelle in its transported position, 
         FIG. 10  shows a sectional view of yet another embodiment of the wind turbine nacelle in its installed position, 
         FIG. 11  shows a cross-sectional view of the wind turbine nacelle of  FIG. 10  in its transported position, 
         FIG. 12  shows a partly sectional view of the wind turbine nacelle, 
         FIG. 13  shows a cross-sectional view of yet another embodiment of the wind turbine nacelle in its installed position, 
         FIG. 14  shows a sectional view of the wind turbine nacelle of  FIG. 13  in its transported position, 
         FIG. 15   a  shows another embodiment of the nacelle in its alternative transported position, 
         FIG. 15   b  shows yet another embodiment of the nacelle in its alternative transported position, 
         FIG. 16  shows a cross-sectional view of  FIG. 15   a  or  15   b  through the middle section of the nacelle in its installed position, 
         FIG. 17  shows a cross-sectional view of  FIG. 15   b  through the middle section of the nacelle in its alternative transported position, 
         FIG. 18  shows another embodiment of the wind turbine nacelle in its transported position, 
         FIG. 19  shows a cross-sectional view of  FIG. 18  through the middle section of the nacelle in its transported position, 
         FIG. 20  shows a cross-sectional view of  FIG. 18 , 
         FIG. 21  shows a sectional view of the main frame structure of the invention, 
         FIG. 22  shows the structure of  FIG. 21  in its folded position, 
         FIG. 23  shows another embodiment of the wind turbine nacelle in its transported position, 
         FIG. 24  shows a cross-sectional view of  FIG. 23 , 
         FIG. 25  shows another embodiment of the wind turbine nacelle in perspective, 
         FIG. 26  shows the nacelle of  FIG. 25  in its transported position, 
         FIG. 27  shows a cross-sectional view of the nacelle of  FIG. 25  in its installed position, 
         FIG. 28  shows a cross-sectional view of the nacelle of  FIG. 25  in its transported position, 
         FIG. 29  shows a cross-sectional view of another embodiment of the nacelle in its installed position, 
         FIG. 30  shows a cross-sectional view of the nacelle of  FIG. 29  in its transported position, and 
         FIGS. 31 and 32  show how the rafters can be minimised during transport. 
     
    
    
     All the drawings are schematic and not necessarily to scale, and they show only those parts necessary to elucidate the invention, other parts being omitted or merely suggested. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A wind turbine nacelle is shown in  FIG. 1 . When a wind turbine nacelle  1  is installed, the nacelle is positioned on a tower (not shown) and connected to three rotor blades through a hub (not shown) in a front end  8  of the nacelle. The hub with rotor blades is always turned to face the wind and the turning movement is performed in a yaw of the bottom of the wind turbine nacelle  1  in the connection with the tower. The nacelle  1  is usually constructed having a main frame structure  12  comprising a bottom frame extending from the yaw, which bottom frame supports the nacelle, the hub, and the rotor blades. The nacelle  1  has a cover  9  in order to protect the interior parts of the nacelle, such as the generator, the gear, etc., which parts together is called the drive train  26 . In this way, the weight of the nacelle, the hub, and the rotor blades is distributed by the bottom structure to the tower. 
     The cover  9  is fastened to the frame, typically to the bottom of the frame, and the cover is a self-supporting construction carrying its own weight. When the nacelle  1  is assembled, it has a first height h 1  which is also its installation height h 1 . When transporting the nacelle  1  on a vehicle, such as a truck bed  27 , the maximum height of the nacelle must not exceed 3.3 metres in many of the European countries and in the USA. However, the nacelle may have a height of up to 4 metres if loaded onto a special transportation system where the nacelle is lowered down between a rear truck bed and a front truck bed on a separate transportation frame. 
     In order to comply with these restrictions, a prior art nacelle is separated into a bottom and a top part when it is to be transported, and each part is transported on a separate truck bed. Each part is covered by a tarpaulin so that rain and dirt whirled around during transport does not enter the interior of the nacelle. 
     When transporting the wind turbine nacelle, the drive train may be transported separately or mounted within the nacelle. If the nacelle weighs too much, the drive train is transported separately. 
     In the solution of the present invention, the nacelle  1  has a bottom part  2 , an end part, and a top part  6 . The bottom part  2  has two opposing side faces  4  and during transport the top part  6  and the end part are separated from the bottom part and the top part is arranged inside or outside the bottom part. The top part  6  may thus be positioned in a second position inside the bottom part  2  so that the overall height of the nacelle is reduced to comply with the transport restrictions in e.g. Europe and USA. In addition, the top part  6  also at least partly covers the bottom part  2  during transport, thus making a tarpaulin expendable. 
     In one embodiment of the invention, the side faces  4  of the bottom part  2  are bent somewhat outwards in order to receive the top part  6  between the side faces. In another embodiment, the side faces  4  of the bottom part  2  are bent somewhat inwards so that the top part  6  extends on the outside of the two side faces. In both embodiments, the top part  6  is used as a roof part during transport, covering the space  5  within the wind turbine nacelle  1 . Furthermore, due to the fact that the top part  6  in this way at least partly overlaps or extends within the bottom part  2 , the overall height of the nacelle  1  is reduced. Moreover, a second truck bed  27  is no longer needed. 
     The wind turbine nacelle  1  of  FIG. 1  can be separated into a front part  8 , a back part  30 , a bottom part  2 , and a top part  6 . The top part  6  comprises a top face  7  and two intermediate parts  10 . Before transport, the separated front part  8 , back part, and intermediate parts  10  are positioned inside the interior space  5  of the nacelle  1 . Subsequently, the top face  7  is arranged on an internal main frame structure  12  so as to form the roof of the nacelle  1  and thus close off the interior of the nacelle as shown in  FIG. 2 . In another embodiment, the top face  7  is supported directly on the side faces  4  of the bottom part  2  instead of on the main frame structure  12 . 
     By dividing the top part  6  into several parts, the overall height of the nacelle  1  can be reduced during transport without reducing the installation height h 1 . As wind turbines are constructed still larger, the need for such a separable wind turbine nacelle  1  is increasing. The height h 1  of the installed wind turbine nacelle  1  is determined by the drive train  26  and the travelling crane operating above the drive train, which is used for maintenance and repair work. The travelling crane moves back and forth on wheels rolling on rails or a support beam, such as an I-profile, on top of the main frame structure  12 . 
     As can be seen from  FIG. 2 , only a top part of the end of the nacelle  1  is separated from the bottom part  2  during transport. In this way, the stability of the wind turbine nacelle  1  is maintained. 
     The top face  7  covers part of the nacelle  1 . However, in order to close or seal off the rest of the interior of the nacelle  1 , a transportation kit  11  comprising different transportation parts  13  are arranged to close or seal off the rest of the nacelle  1 , as shown in  FIG. 3 . To seal off the interior of the nacelle  1 , the transportation parts  13  may be equipped with sealing means arranged along the edges of each transportation part. 
     In the embodiment of  FIGS. 3 and 4 , the transportation kit  11  comprises five transportation parts  13 , i.e. a back portion  14 , a front portion  15 , two side portions  16 , and a top portion  17 . These portions are shown in an exploded view in  FIG. 4 . The transportation parts  13  may also be made of a sealing material so that separate sealing means is unnecessary, or the portions may be arranged so that water flows from one transportation part onto another and away from the nacelle  1 . 
     As can be seen in  FIG. 4 , the transportation kit parts  13  are made from a substantially rigid material so that each part can carry its own weight. Due to the fact that the transportation parts  13  are substantially rigid compared to a prior art cover solution, such as a tarpaulin, the transportation parts can be reused several times for transport of several wind turbine nacelles. When one wind turbine has been installed, the transportation kit  11  is sent back to the manufacturing plant and is mounted on a new wind turbine nacelle for transportation of the new wind turbine nacelle. 
     The prior art tarpaulins could not be reused since they always suffered too much damage during transport. Deploying the transportation kit  11  instead, the kit can be reused and when the kit parts  13  are too damaged, they may be granulated and remoulded into new kit parts. In this way, the material of the transportation parts  13  can be reused over and over again. The transportation parts  13  may be moulded or vacuum formed from any kind of plastic, such as PE, PUR, PET, ABS, etc. 
     In  FIG. 5 , the top face  7  is arranged in a supported position on a set of support beams  18 , such as an I-profile. As can be seen from  FIG. 6 , the side portion  16  of the transportation kit  11  overlaps the side faces  4  of the bottom part  2  at its outside. Also, the side portion  16  overlaps the top face  7  at the underside of the top face  7 . In order to support the top face  7 , the transportation kit  11  may further comprise a connection portion  19  serving as a prolongation of the support beam. 
       FIG. 7  shows the assembled top part  6  from within the space  5  of the nacelle  1 . The top face  7  is supported on a connection part  20  which again is supported by rafters  21 . The rafters  21  are arranged in supportive connection with the support beam  18  which is supported by the main frame structure  12 . Thus, the connection part  20  and the rafters  21  are placed in the inside of the wind turbine nacelle cover  9  and thus not visible from outside the cover. 
     As can be seen from  FIG. 8 , which is a sectional view of  FIG. 7 , the intermediate part  10  overlaps the side face  4  and the top face  7  so that water can run from the top face along the outside of the intermediate part and further onto the outside of the side face. 
     When the nacelle  1  of  FIG. 7  has been prepared for transport, the rafters  21  and the connection parts  20  are separated from the support beam  18  and placed inside the nacelle. The intermediate parts  10  are also placed inside the space  5  of the nacelle, and the space is closed by arranging the top face  7  as a lid on the support beams  18  as shown in  FIG. 6 . As can be seen from  FIG. 6 , the connection part  20  is reused for supporting the side portion  16  of the transportation kit  11  and the top face  7 . 
     Another way of supporting a top face  7  is shown in  FIG. 9 , in which the connection part  20  is also reused. However, no additional connection portions  19  are needed since the connection part  20  is supported directly on the support beam  18  for supporting the side face  16  of the transportation kit  11  and the top face  7 . 
     In one embodiment, the installation height h 1  of the wind turbine nacelle  1  of  FIG. 7  may be 3.9 metres whereas the height h 2  of the nacelle in the corresponding transported position, shown in  FIG. 5 , is approximately 3.3 metres. In this way, the height of the nacelle  1  can be reduced 60 centimetres, which is enough for it to be allowed to be transported on one truck bed  27  instead of two. Hereby, the transportation cost is reduced since two separate trucks are no longer needed. Furthermore, by reusing the transportation parts  13 , the present invention becomes even more cost-saving and environment-friendly. 
     The rafters  21  may have all sorts of designs depending on the complexity and the design of the nacelle  1 . In  FIG. 10 , the rafter  21  is shown having an indentation  24  in one end where it rests on the support beam  18 . When having such an indentation  24 , no additional fittings  22 , such as those shown in  FIG. 8 , are needed. In addition, the rafter  21  may, in its other end, have an indention for supporting the connection part  20 , making the construction more reliable. In this embodiment, the support beam  18  rests directly on the main frame structure  12 . 
     In  FIG. 11 , yet another embodiment of the nacelle  1  is shown in its transported position. In this embodiment, the top face  7  rests on the side portions  16  of the kit  11 . To support the side portion  16 , a connection part  20  is connected to the support beam  18  through a bracket  23 . The support beam  18  is arranged on top of the main frame structure  12 . Furthermore, the top face  7  has a cross-sectional profile enabling the top face to be dismounted both from the outside and the inside of the wind turbine nacelle  1 . 
     The transportation parts  13  may have sealing means. However, if the top face  7  overlaps the transportation parts  13 , which again overlap the side faces  4  or other transportation parts, and so forth as shown in  FIG. 11 , a sealing connection is provided since water runs from the top face down onto the transportation part and further onto the side face or an additional transportation part. 
     When the wind turbine nacelle  1  is in its installed position, the connection part  20  for supporting the top face  7  may hinder parts of the drive train  26  from being removed in order to perform repair or maintenance work. Thus, the connection part  20  may be provided with indentations or made as separate parts along the length of the top face  7 , thus making it possible to take out either parts of the drive train or the entire drive train  26 . This is illustrated in  FIG. 12 , in which mountings  25  of the drive train can easily pass through the indentation of the connection part  20 . 
     In  FIG. 13 , the top part  6  is dividable into three parts, i.e. a top face  7  and two intermediate parts  10 . The intermediate parts  10  abut the side faces  4  of the bottom part  2  and are held in place between the top face  7  and a connection part  20  which may be some kind of profile, such as an H-profile, I-profile, etc. The connection part  20  is supported by rafters  21 . In its transported position, as shown in  FIG. 14 , a transportation part  13 ,  16  is supported directly on the support beam  18  for supporting the top face  7  and overlapping the side face  4  of the bottom part  2 . In this embodiment of the nacelle  1  in its transported position, the connection part  20  is not reused as a support part, but is merely positioned inside the space  5  of the nacelle. 
     The top part  6  may be separated into three parts when transported, as shown in  FIGS. 15   a  and  15   b . The intermediate parts  10  are either placed either outside the top face  7  and are also supported by the support beam  18  as shown in  FIG. 15   a , or the parts may be placed inside the nacelle  1  as shown in  FIG. 15   b . The intermediate parts  10  may have a variety of designs. In  FIG. 16 , the intermediate part  10  is shown as a frame structure made of elongated sheets. The top face  7  is connected with a connection part  20 , which is a fixed part of the top face and may be made from a sealing and/or flexible material. Thus, the top face  7  has a sealing connection to the support beam  18  when the top face is supported by the support beam, as shown in  FIG. 17 . Thus, rain and other precipitation will flow from the outside of the top face  7  and along the support beam  18  to the ends of the support beams. If a transportation kit  11  is used, the top face  7  may make a sealing connection to the transportation parts  13  of the kit. 
     In order to uphold the intermediate parts  10  and thus the top face  7 , the nacelle  1  comprises a connection part  20  in the form of rafters  21  or beams  18 . The rafters  21  or beams  18  have indentations to provide a reliable connection to the intermediate parts  10 . 
     As mentioned and as is illustrated in  FIGS. 18 and 20 , the top face  7  may also be one part which is placed in between the side faces  4  of the bottom part  2 , squeezing the top part in between the side faces and thus somewhat increasing the width of the bottom part. 
     In the installed position of the wind turbine nacelle  1 , rafters  21  or connection parts  20  are placed intermediate the support beam  18  and the top part  6  in order to support the top part as shown in  FIG. 19 . In the transported position of the nacelle  1 , the top face  7  is supported directly on the support beam  18  as illustrated in  FIG. 20 . 
     In one embodiment, part of the main frame structure  12  is foldable as shown in  FIGS. 21 and 22 . In this way, the height of nacelle  1  can be reduced even further if necessary. 
     In addition, the top part  6  may be dividable into two parts which is separated when preparing the nacelle  1  for transport. The top part  6  is separated along the middle of the top part in the longitudinal extension. The top part  6  may be separated along its centre line or along a line displaced from its centre line, thus either separating it into two equally sized parts or separating it into two parts of different sizes. The design of the top part  6  depends on the construction of the drive train  26  so that the two parts are supported directly or indirectly in a simple manner in relation to the drive train. 
     In  FIG. 23 , the top part  6  is separated into two equal parts and arranged in an overlapping position so that the parts can be placed easily within the space  5  of the bottom part  2 . In  FIG. 24 , the two top parts are supported by the main frame structure  12  using some kind of connection parts  20  (not shown) and the two parts overlap each other at the top. In the transported position, the top parts may be supported by the support beam  18 . 
     In  FIG. 25 , the top part  6  is separated into two differently sized parts. As can be seen in  FIG. 25 , the top part  6  is separated into two parts and arranged so as to extend outside of the width w of the bottom part  2  so that part of the top parts overlaps the side face  4 , as shown in  FIG. 26 . 
     In another embodiment, the intermediate parts  10  of the top part  6  overlap the top face  7  in the installed position as shown in  FIG. 27 . When the nacelle  1  is prepared for transport, the intermediate parts  10  are pulled outwards towards the side faces  4  so that the intermediate parts extend over and overlap the outside of the side faces  4 . In this overlapping position, the intermediate parts  10  still overlap the top face  7  and are supported on the support beam  18 . Thus, the overlap between the top face  7  and the intermediate part  10  in  FIG. 27  is larger than the overlap between the top face and the intermediate part in  FIG. 28 . The rafter  21  shown in  FIG. 27  is positioned inside the space  5  when the nacelle  1  is transported. Thus, one part may overlap a predetermined part of another part. 
     In  FIGS. 29 and 30 , the intermediate part  10  and the rafter  21  of  FIG. 27  have been constructed as one part so that the intermediate part  10  both has the strength of the rafter and also serves as the cover  9  of the wind turbine nacelle  1 . The intermediate part  10  overlaps a predetermined part of the top face  7  in  FIG. 29 , which predetermined part is decreased in the corresponding transported position of  FIG. 30 . The intermediate part  10  is supported by the support beam  18 , which also serves as rails for the travelling crane. When the top part  6  is divided into two overlapping parts as in  FIGS. 27-30 , a simple design of the nacelle  1  is provided since the construction does not have a lot of different additional supporting and/or connecting parts. In this way, no additional parts are needed for changing the nacelle  1  from its transported position to its installed position, and vice versa. The intermediate part  10  may constitute an additional expense; however, no expenses will be needed for any additional parts. 
     In another embodiment, the rafters  21  may be adjustable in height in order to minimise the height of the nacelle  1  during transport as shown in  FIGS. 31 and 32 . Some of the rafters  21  may have a telescopic construction, or one part of a rafter may be movable in relation to another part of the same rafter to be able to prolong or decrease the length of each rafter. 
     In one embodiment, four rafters  21 , two in each side, are made adjustable. When transporting the nacelle  1 , all rafters  21  other than the four adjustable rafters are positioned inside the nacelle, and the four adjustable rafters are reduced in height in order to comply with the height restrictions for transports on ground. 
     In the embodiments of  FIGS. 1-4 ,  15 ,  18 , and  23 , at least part of the front part  8  of the nacelle is removed in order to fold the nacelle into its transported position and thus decrease the height of the nacelle. 
     In the embodiments of  FIG. 25-30 , the nacelle  1  does not have a detachable front part  8 , but the back part still has to be removed. In another embodiment, it is the front part  8  which is removed when preparing the nacelle for transport, whereas the back part of the nacelle is not detachable. 
     By a front part  8  and a back part is meant any kinds of detachable end faces. 
     By a wind turbine is meant any kind of apparatus able to convert wind power into electricity, such as a wind generator, wind power unit (WPU), or wind energy converter (WEC). And by a wind turbine nacelle  1  is meant any kind of housing housing the drive train  26  of the wind turbine, e.g. the generator, the gear, etc. 
     Although the invention has been described above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.