Abstract:
A rotor hub for a wind turbine, comprising a first device for lifting and/or transporting being arranged in a first interior of the rotor hub is provided. Further a wind turbine comprising the rotor hub is suggested. The rotor hub is applicable for all kinds of wind turbines.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to EP Application No. EP14170286.0, having a filing date of May 28, 2014, the entire contents of which are hereby incorporated by reference. 
       FIELD OF TECHNOLOGY 
       [0002]    The following relates to a rotor hub and a wind turbine comprising a rotor hub. 
       BACKGROUND 
       [0003]    Alternative energy sources have become much more necessary as fossil fuels are depleted and pollute the environment. Wind energy is one of the most cost effective of all types of renewable energy. However, to make wind a viable source of energy or electricity in particular careful design of wind-capturing machines is necessary. A variety of principles of physics are used to create wind turbines that can efficiently capture energy from the wind. Wind turbines can be onshore or offshore. 
         [0004]    With the increasing significance of wind power the size and dimension of the wind turbines is also increasing. As a consequence, huge effort, logistically and economically, is necessary, e.g., for service and maintenance of such wind turbines. Heavy components in a wind turbine such as yaw motors, hydraulic or brake components in a wind turbine, etc. are typically handled or replaced due to, e.g., mal-function or age. Therefore, external cranes and hoist mechanisms are used when a wind turbine is undergoing a service inspection or repair. 
         [0005]    EP 2 363 598 A1 relates to a wind turbine comprising a nacelle being rotatable disposed on a tower with the nacelle having a first cavity, a generator housing portion disposed upstream to the nacelle having a second cavity, a hub disposed upstream to the generator housing portion with attached rotor blades at it having a third cavity, whereby the first, second and third cavities communicate with one another. Further, the wind turbine comprises a railway system comprising at least one rail-element having a means for lifting and/or transporting being movable along the rail-system, wherein the rail-system at least partially extends through at least two adjacent cavities. 
         [0006]    Due to their large size and/or bulky properties, the use of aforementioned cranes and hoist mechanism is complicated and not efficient. 
       SUMMARY 
       [0007]    An aspect relates to improving the approach for a wind turbine to ensure effective maintenance and serviceability. 
         [0008]    This problem is solved according to the features of the independent claims. Further embodiments result from the depending claims. 
         [0009]    In order to overcome this problem, a rotor hub for a wind turbine is provided, comprising first means for lifting and/or transporting being arranged in a first interior of the rotor hub. 
         [0010]    The proposed solution takes the advantage of the increasing dimensions of the wind turbines by using available space for serviceability, maintenance, rework and/or re-furbishment of any parts of the wind turbine where replacement and renewal is possible. Advantageously, the proposed solution allows a technician handling the parts of the wind turbine, in particular parts of the rotor hub, without lifting heavy weights, by fixing the parts during, e.g., service or maintenance activities to the means for lifting and/or transporting, enabling freely handling of the parts within the interior or the rotor hub. 
         [0011]    In an embodiment, the rotor hub comprises a rotatable part and the means for lifting and/or transporting being attached to the rotatable part. 
         [0012]    The rotatable part may be a shell or housing of the rotor hub or parts of the shell or housing. Preferable, the means for lifting and/or transporting is attached or mounted at the inner surface of the rotatable part. 
         [0013]    Turning the rotor hub, i.e. the rotatable part of the rotor hub together with the means for lifting and/or transporting in a proper angular position allows a comfortable handling of parts within the interior of the rotor hub. 
         [0014]    In another embodiment, the means for lifting and/or transporting comprises at least one hoist beam. The hoist beam can be any kind of hoist mechanism, enabling lifting or lowering of parts or weights. 
         [0015]    In a further embodiment, the means for lifting and/or transporting comprises a rail-system being attached to the rotatable part. The rail-system allows a bigger freedom, i.e. more flexibility for handling parts within the interior of the rotor hub. 
         [0016]    In a next embodiment, the at least one hoist beam is moveably attached to the rail-system. The hoist beam may be detachably attached to the rail-system. 
         [0017]    It is also an embodiment that the means for lifting and/or transporting comprises at least one crane. The at least one crane may be attached to the rail-system wherein the crane may be detachably attached to the rail-system. The at least one crane may be attached to the rail-system in addition to the at least one hoist beam. 
         [0018]    The at least one crane may be arranged within the interior of the rotor hub without any rail-system, e.g., being mounted on a fixed part (like a stationary shaft) of the wind turbine. 
         [0019]    The problem stated above is also solved by a wind turbine comprising a rotor hub as described herein. 
         [0020]    Pursuant to another embodiment, the rotor hub is rotatable mounted at a frame of the wind turbine, the frame comprises a second interior and the first means for lifting and transporting is communicating with the second interior via at least one manhole being part of the frame. 
         [0021]    According to an embodiment, a second means for lifting and/or transporting is arranged in the second interior, the first means for lifting and/or transporting and the second means for lifting and/or transporting are communicating with each other via the at least one manhole. 
         [0022]    According to another embodiment, the second means for lifting and/or transporting comprises a second rail-system. 
         [0023]    In yet another embodiment, the second means for lifting and/or transporting comprises at least one hoist beam being attached to the second rail-system. 
         [0024]    According to a next embodiment, the second means for lifting and/or transportation comprises at least one cart being moveable along the second rail-system. 
         [0025]    The at least one cart maybe used without the second rail system, thereby, e.g., being directly moved on a bottom within the interior of the frame. 
         [0026]    The at least one cart can be any kind of vehicle which allows the loading of one or serveral parts or objects and which supports the transfer or transport of the parts along the rail system within the second interior. 
         [0027]    Pursuant to yet an embodiment, the frame comprises a hollow shaft, the second interior is part of the hollow shaft. 
         [0028]    According to a further embodiment, the rotor hub is rotatably mounted on the frame via at least one bearing, the at least one bearing is a fluid bearing or a tapered bearing comprising at least one sliding surface. 
         [0029]    Pursuant to a next embodiment, the wind turbine comprises a positioning means allowing a stepwise positioning of the rotor hub in order to achieve an appropriate positioning of the first means for lifting and/or transporting within the first interior of the rotor hub. 
     
    
     
       BRIEF DESCRIPTION 
         [0030]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0031]      FIG. 1  shows an exemplarily schematic overview of a wind turbine; 
           [0032]      FIG. 2  illustrates a more detailed schematic view of a section at the upwind side of the wind turbine according to  FIG. 1 ; 
           [0033]      FIG. 3  shows a schematic view of an example of a small crane; and 
           [0034]      FIG. 4  shows in a schematic view an example of turner equipment allowing a stepwise positioning of the rotor hub. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    With reference to  FIG. 1  an exemplary schematic overview of a wind turbine  100  is shown by a longitudinal cut. The wind turbine  100  comprises a tower  110  and a frame  120  which is rotatable mounted on top of the tower  110 . An exemplary embodiment of the frame  120 , defining an interior  121 , is a stationary hollow shaft. A rotor hub  140  is rotatably mounted on the upwind side of the shaft  120  through a front bearing  150  and a back bearing  151 . The rotor hub  140  is adapted to be connected to a plurality of rotor blades  143 . 
         [0036]    The rotor hub  140  comprises a housing or shell  141  defining an interior  142 . Further, a generator  130  is mounted on the shaft  120  via the back bearing  151  and a support bearing  152 . A rotatable part  131  of the generator  130 , which is also referred to as generator rotor, is connected to the shell  141  of the rotor hub  140  via the back bearing  151 . 
         [0037]    The wind turbine  100  can be, e.g., a direct drive wind turbine. 
         [0038]    According to conventional wind turbine designs the front bearing  150  and the back bearing  151  is a roller bearing or ball bearing which requires external crane capacity if such a bearing  150 ,  151  needs replacement. This type of service is associated with costs, especially for wind turbines located offshore. 
         [0039]    According to an advanced design of the wind turbine, enabling an appropriate use of the proposed solution, suitable fluid bearings may be employed, particularly hydro-dynamic, hydrostatic or hybrid bearings, based on the hydrodynamic and/or hydrostatic principal for generating a pressure build-up, lifting and separating rotating components from a stationary part of a wind turbine structure. Exemplary components of the bearings are tilting pads and/or fixed profile pads or/and pads supported by other means allowing geometry change/adaption (like, e.g., hydraulic support, spring beds or flexure support). 
         [0040]    Each of the bearings  150 ,  151  is capable of handling radial loads as well as thrust emerging towards both axial directions. 
         [0041]    The support bearing  152  is adapted to carry limited loads compared to the loads carried by the bearings  150 ,  151 . The support bearing  152  ensures maintenance of a permanent air gap between the generator rotor  131  and a stationary part  132  of the generator  130  which is also referred to as generator stator. 
         [0042]    A flexible housing or shell of the generator rotor  131  may avoid the development of significant internal forces due to possible over constraints of the arrangement of the bearings  150 ,  151 ,  152 . 
         [0043]      FIG. 2  illustrates a more detailed schematically view of a section at the upwind side of the frame or shaft  120  according to  FIG. 1  thereby showing an exemplary embodiment of the proposed solution. 
         [0044]    A shell  241  of a rotatable part of a rotor hub  240  is mounted at the upwind side of a frame  220  of a wind turbine via a front bearing  250  and a back bearing  251 . The frame  220 , like, e.g., a stationary hollow shaft, comprises a manhole  225  for maintenance and service activities. The shell  241 , defining an interior  242  of the rotor hub  240 , is connected to a housing of a generator  230  via the back bearing  251 . The housing of the generator  230  can be, e.g., a part of a generator rotor. 
         [0045]    According to the exemplary embodiment as shown in  FIG. 2 , the front bearing  250  and the back bearing  251  are designed as fluid bearings or tapered bearings, comprising a least one conical shaped sliding surface. The benefit of using fluid or tapered bearings is that at least one part of the bearing (also referred to as bearing part) like, e.g., at least one part of a sliding pair can be taken out or can be extracted and replaced, e.g., during maintenance and service activities without disassembling a drive train and/or a complete rotor-plane (i.e. the rotor hub  240  together with the rotor blades  243 ). 
         [0046]      FIG. 2  exemplarily shows a section of a direct-drive wind turbine having a direct mechanical coupling between the rotor hub  240  and the generator  230 . Consequently, rotor blades  243  mounted at the rotor hub  240  and the generator rotor are driven by the wind as a unit. 
         [0047]    According to a first embodiment of the proposed solution, a rail-system  260  is adjusted in the interior  242  of the rotor hub  240  in such a way that the rail-system  260  is a fixed component of the rotatable part of the rotor hub  240 . 
         [0048]    Several ways may be possible mounting the rail-system  260  within the interior  242  of the rotor hub  240  to be a fixed component or an element of the rotatable part of the rotor hub  240 . Alternatively, the rail-system  260  may also be detachably mounted to the rotatable part of the rotor hub  240 . 
         [0049]    Further, a means for lifting and/or transporting is detachably attached to the rail-system  260 . One embodiment of the means for lifting and/or transporting comprises a rotatable hoist beam  265  being moveable along the rail-system  260  within the interior  242  of the rotor hub  240  in both directions. The hoist beam  265  and the rail-system  260 , defining together a functional unit, may be also referred to as the means for lifting and/or transporting. 
         [0050]    Usually, the hoist beam  265  comprises a special fixture  267  for mounting parts to be transferred (i.e. to be lifted, lowered and/or transported) to the hoist beam  265  and for handling the parts within the interior  242  of the rotor hub  240 . 
         [0051]    According to an alternative embodiment the means for lifting and/or transporting comprises a small crane, e.g., with a properly dimensioned arm enabling several degrees of freedom to operate within the interior  242  of the rotor hub  240 . Thereby, the crane may be attached to the rail-system  260  being moveable with the interior  242 . 
         [0052]    Alternatively, the crane may be directly mounted to the rotatable part of the rotor hub  240 , thereby defining a fixed component or element of the rotatable part of the rotor hub  240 . 
         [0053]    The rotatable part can be, e.g., the shell or housing of the rotor hub  240 . Also at least one reinforcement plate, e.g., of a blade bearing can be a fixed component or element of the rotatable part of the rotor hub  240 . 
         [0054]    According to a further possible embodiment, the crane may be directly mounted to a stationary part of the wind turbine, like, e.g., the stationary shaft  220  within the interior  242  of the rotor hub  240 . 
         [0055]      FIG. 3  shows a schematic view of an example of a crane  300 . A box  310  represents a special fixture enabling the mounting and handling of bearing parts (not shown) within the interior of a rotor hub. Accordingly, after turning the rotor hub into a proper position, the crane  300  can be positioned by a crane operator in such a way (not shown), that the relevant bearing part mounted onto the special fixture, can be transferred through the manhole  225  to the interior  221  of the shaft  220 . 
         [0056]    Applying the proposed solution as shown in  FIG. 2 , e.g., one part or several parts of the front and/or back bearing  250 ,  251  (also referred to as bearing parts) can be exchanged or replaced during maintenance or service activities. Thereby, after disassembling, the bearing parts (e.g. liner, sliding material, back pads, pivot points, etc.) to be replaced can be extracted and transported (by using e.g. special equipment or further cranes, not shown) to the possible range of activity of the hoist beam  265  in order to use the hoist beam  265  for further lifting or lowering and transport of the bearing parts. 
         [0057]      FIG. 2  exemplarily shows an extracted bearing part  266  mounted by the special fixture  267  to the hoist beam  265  being transferred through the manhole  225  into the interior  212  of the hollow shaft  220 . One or more appropriate (new) parts (not shown), replacing the extracted bearing part  266  will be handled according to the reverse direction, i.e. transferred towards the bearing  250 ,  251 . 
         [0058]    The proposed solution allows an advantageous, i.e. simplified, performance of service or maintenance activities, like, e.g., exchanging bearing parts by rotating the rotor hub  240  stepwise in such a way, that the respective bearing part to be exchanged, the rail-system  260  and the hoist beam  265  are in the correct position to communicate with each other and in particular to be aligned to enable proper hoisting of the bearing part. This can be applied sequentially to all parts of the bearings  250 ,  251 , to be exchanged or replaced. 
         [0059]    To allow stepwise positioning, the rotor plane, i.e. the rotor hub  240  together with the rotor blades  243 , can be rotated stepwise, e.g. by applying special equipment used during initial assembly of the rotor blades. Alternatively, other equipment, like, e.g., turner equipment, can be used allowing rotation of the rotor hub  240 . Stepwise positioning, e.g., can be applied for all single pads of the bearings  250 ,  251  until all bearing parts are replaced. 
         [0060]      FIG. 4  shows in a schematic view an exemplary embodiment of a component of a turner equipment  400  mounted, e.g., on a back end of a generator (not visible). The turner equipment  400  comprises two hydraulic turner cylinders  410 . A first side  415  of each of the turner cylinders  410  is attached to a stationary part  420  (like, e.g. a fixed shaft) of a wind turbine. A second side  416  of each of the turner cylinders  410  is attached, e.g., to a break disk of a wind turbine or a rotor disk  430  of the generator. The turner equipment  400  may be used for a stepwise rotation of the generator and a rotor hub during installation of single rotor blades and will be detached after finalization of the installation. The same equipment  400  may be reused at a later time, e.g., during maintenance and service activities. 
         [0061]    According to an advanced embodiment of the proposed solution, a further rail-system  270  is stationary adjusted in the interior  221  of the hollow shaft  220 . A further means for lifting and/or transporting  275  is detachable attached to the rail-system  270 . According to the embodiment of  FIG. 2 , the means for lifting and/or transporting  275  comprises a cart with, e.g., one or more pair of wheels enabling the movement of the cart  275  with-in the interior  221 , i.e. the movement of the cart  275  along the rail-system  270  in both directions between the upwind side and the downwind side of the shaft  220 . 
         [0062]    Alternatively or in addition to that, the means for lifting and/or transporting  275  may comprise a rotatable hoist beam or a small crane (not shown). 
         [0063]    As illustrated in  FIG. 2 , the bearing part  266  being fixed to the hoist beam  265  can be hoisted or transferred through the manhole  225  of the shaft  220  to be unloaded on the cart  275 , which can be moved in a proper position on the rail-system  270  to enable proper unloading and further transport of the bearing part  266 . After unloading, the cart  275 , loaded with the bearing part  266 , can be moved along the rail-system  270  to one end of the hollow shaft  220  to allow further unloading of the bearing part  266  through an opening (not shown) onto an external crane outside of the wind turbine  100  hoisting the bearing part  266  to the bottom of the ground. 
         [0064]    According to a further embodiment, the rail-system  270  may be rotatable adjusted within the interior of the hollow shaft  220 . Turning the rail-system clockwise or counterclockwise around its longitudinal axis (illustrated by a double arrow  271  in  FIG. 2 ) allows an improved positioning, e.g., of the cart  275  and therefore allows a more comfortable loading or unloading of the bearing part  266 . 
         [0065]    The following steps describe an exemplary exchange procedure or method for bearing parts, mounted, e.g., on a non-rotatable part (like the fixed shaft  220 ) of the wind turbine  100 . As an advantage, the method is applicable for all parts of the bearing, i.e. at any angle or at any circumferential position of the relevant bearing part.
       Turning rotor hub  240  in such a way, that the hoist beam  265  is in the same angular position as the bearing part  266  to be exchanged.   Mounting the fixture  267  of the hoist beam  265  at the bearing part  266  and, after fixing, dismantling the bearing part  266  such that the weight of the bearing part  266  is carried by the hoist beam  265 .   Turning the rotor hub  240  in the same angular position as the manhole  225  located at the shaft  220 . By turning the rotor hub  240  also the hoist beam  265  together with the fixed bearing part  266  will be turned to the required position.   Transferring the bearing part  266  through the manhole  225  towards the cart  275  within the interior  221  of the shaft  220 . The transfer can be either   by lowering the bearing part  266  through the manhole  225  toward the cart  275  in case the actual position of the manhole  225  is upward to the cart  275 , or   by lifting the bearing part  266  through the manhole  225  towards the cart  275  in case the actual position of the manhole  225  is at the bottom of the shaft  220 .   Unloading the bearing part  266  to the cart  275  and moving the cart  275  together with the bearing part  266  along the rail-system  270 .   transferring the bearing part  266  to the bottom of the tower by using, e.g., an external crane, like a nacelle crane. The transfer may by external or inside of the tower.       
 
         [0074]    Usually, the bearing parts  266  do have significant weight, being too much than can be handled by hand by technicians during service or maintenance activities. Applying the proposed solution, all bearing parts, to be exchanged or replaced, can be proper handled by using the hoist beam  265  together with the special fixture  267  carrying the weight when dismounting the bearings  250 ,  251 . 
         [0075]    The proposed solution takes the advantage of the increasing dimensions of the wind turbines by using available space within the wind turbine for serviceability, maintenance, rework and/or refurbishment of any parts of the wind turbine where replacement and renewal is possible. 
         [0076]    As an advantage, all activities necessary for replacement and refurbishment can be executed inside of the wind turbine without using, e.g., an external crane for demounting the rotor plane and the fixed shaft. 
         [0077]    One or more sections, e.g., of the bearings or a bearing part may be under load when the turbine is stationary. Thus, a system may be required enabling the unloading of the relevant part during inspection, service or replacement activities. As an exemplary solution, jack up systems may be applied, partially lifting the weight of the rotor hub or a bearing support and allowing unloading of the particular bearing section or bearing part and/or optionally distributing the weight to neighboring sections. 
         [0078]    Although the invention is described in detail by the embodiments above, it is noted that the invention is not at all limited to such embodiments. In particular, alternatives can be derived by a person skilled in the art from the exemplary embodiments and the illustrations without exceeding the scope of this invention.