Abstract:
A method of replacing a wind turbine blade includes suspending the wind turbine blade from support hub of a wind turbine, connecting one or more cable climbing members between the support hub and the wind turbine blade, and lowering the one or more cable climbing members and the wind turbine blade from the support hub.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to the art of wind turbines and, more particularly, to a method and system for replacing a wind turbine blade. 
         [0002]    Wind generators convert energy provided by air currents into electricity. The air currents rotate large rotor blades or propellers that are mounted in nacelles at the top of a tower. The blades spin a rotor relative to a stator to generate an electrical current. The rate of rotation is controlled by varying blade pitch as well as through the use of various braking systems. During high wind conditions, the blade pitch is adjusted to spill wind energy in order to limit rotational speed. Occasionally, the braking system is employed to further prevent the blades from achieving high rotational speeds. During low wind conditions, the blade pitch is adjusted in order to capture as much wind energy as possible. 
         [0003]    Over time, the wind generators require maintenance. Debris, hailstones and the like oftentimes impact the blades and cause damage. Replacing a worn or damaged blade generally requires the presence of one or more large ground or sea based cranes. The large cranes are used to retain and lower the blade to a surface such as the ground or a ships deck. In some cases, replacing a blade necessitates that others of the blades be moved to an off balance position. That is, a brake system is activated to position the blade being replaced in a position that is horizontal to ground. In such a case, the others of the blades are off-balance imparting forces to the braking system. In other cases, the blade is placed in a position perpendicular to ground and lowered. In such cases, multiple crews are required to rotate the blade to prevent contact between the surface and a tip portion of the blade that may result in damage. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of an exemplary embodiment, a method of replacing a wind turbine blade includes suspending the wind turbine blade from support hub of a wind turbine, connecting one or more cable climbing members between the support hub and the wind turbine blade, and lowering the one or more cable climbing members and the wind turbine blade from the support hub. 
         [0005]    According to another aspect of an exemplary embodiment, a system for lowering a wind turbine blade mounted to a support hub includes one or more support members extending between the wind turbine blade and the support hub, one or more jacking members operatively coupled to corresponding ones of the one or more support members, and one or more cable climbing members operatively connected between the support hub and the wind turbine blade. The one or more jacking members are configured and disposed to transfer support of the wind turbine blade from the one or more support members to the one or more cable climbing members. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  is a partial perspective view of a wind turbine support hub having a system for effecting replacement of a single wind turbine blade in accordance with an exemplary embodiment; 
           [0009]      FIG. 2  is a partial perspective view a wind turbine blade of  FIG. 1  suspended a first distance from the wind turbine support hub by a plurality of support members; 
           [0010]      FIG. 3  depicts a support member and hydraulic jack cylinder in an extended configuration in accordance with an exemplary embodiment; 
           [0011]      FIG. 4  depicts the hydraulic jack cylinder of  FIG. 3  in a retracted configuration; 
           [0012]      FIG. 5  is a partial perspective view of a plurality of bracket members secured to the wind turbine support hub and a plurality of bracket elements secured to the wind turbine blade; 
           [0013]      FIG. 6  depicts a plurality of cable climbing members and a plurality of support members supporting the wind turbine blade from the wind turbine support hub; 
           [0014]      FIG. 7  depicts one of the plurality of cable climbing members supporting the wind turbine blade from the wind turbine support hub; 
           [0015]      FIG. 8  depicts the wind turbine blade of  FIG. 1 , supported from the wind turbine support hub through only the plurality of cable climbing members; and 
           [0016]      FIG. 9  depicts the wind turbine blade being lowered toward ground. 
       
    
    
       [0017]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    A wind turbine is indicated generally at  2  in  FIG. 1 . Wind turbine  2  includes a support hub  4  having attached thereto a first wind turbine blade  7 , a second wind turbine blade  8 , and a third wind turbine blade  9 . Third wind turbine blade  9  includes an end or root portion  11 . Of course, first and second wind turbine blades  7  and  8  also include end or root portions (not separately labeled). End portion  11  includes an array of mechanical fasteners, indicated generally at  14 , that extend through a corresponding plurality of openings, one of which is shown at  16  ( FIG. 3 ) provided on a blade receiving portion  18  of support hub  4 . In accordance with an exemplary embodiment, a blade replacement system, a portion of which is indicated at  20 , is provided within support hub  4 . 
         [0019]    Blade replacement system  20  includes a first support member  25 , a second support member  26 , and a third support member  27 . Support members  25 - 27  take the form of threaded rods (not separately labeled) that extend through openings  16  in blade receiving portion  18  and engage with threaded openings (not separately labeled) previously provided with fasteners  14  as shown in  FIG. 2 . Once installed, a hydraulic jacking cylinder  34 , illustrated in  FIG. 3 , is guided over each support member  25 - 27 . Hydraulic jacking cylinder  34  includes a base section  36  that rests on an inner surface (not separately labeled) of blade receiving portion  18  and a plurality of telescoping sections  38 - 40 . Base section  36  and telescoping sections  38 - 40  include a central passage  42  that receives a corresponding one of support members  25 - 27 . 
         [0020]    In  FIG. 3 , hydraulic jacking cylinder  34  is shown mounted over a free end (not separately labeled) of support member  25 . Once in position, telescoping sections  38 - 40  are extended and a retaining nut  49  is threaded onto first support member  25 . Once additional hydraulic jacking cylinders (not shown) are provided on first and second support members  26  and  27 , retaining nuts  49  are removed from fasteners  14 . At this point, telescoping sections  38 - 40  are shifted into base section  36  ( FIG. 4 ) separating third wind turbine blade  9  from support hub  4  a first distance. Once separated the first distance, one at a time, retaining nuts  49  are moved away from base section  36  and telescoping sections  38 - 40  are again extended in preparation for further separation of third wind turbine blade  9  from support hub  4 . 
         [0021]    Blade replacement system  20  also includes a plurality of bracket members, one of which is indicated at  54  and a plurality of bracket elements, one of which is indicated at  57 . When separated the first distance, bracket members  54 , are mounted to blade receiving portion  18  and bracket elements  57  are mounted to select ones of fasteners  14  on third wind turbine blade  9 , as shown in  FIG. 5 . Each bracket member  54  and bracket element  57  includes mounting structure, shown in the form of openings (not separately labeled). A number of cables  64 ,  65 , and  66 , are connected to corresponding ones of bracket members  54 . Specifically, one end (not separately labeled) of each cable  64 ,  65 , and  66  is mounted to a corresponding bracket member  54  which another, free end of each cable  64 ,  65 , and  66  is allowed to fall toward ground. By “ground” it should be understood that the free end of each cable  64 ,  65  and  66  may fall towards ground, a ship&#39;s deck, or a body of water depending upon the location of wind turbine  2 . Once bracket members  54  and bracket elements  57  are installed, telescoping sections  38 - 40  of hydraulic jacking cylinders  34  are lowered creating further separation between third wind turbine blade  9  and support hub  4 . 
         [0022]    The additional separation allows for the mounting of cable climbing members. More specifically, blade replacement system  20  further includes a plurality of cable climbing members  80 ,  81 , and  82 . Cable climbing members are connected to corresponding ones of cables  64 ,  65 , and  66 . Cable climbing members  80 ,  81 , and  82  are controlled so as to climb from the free ends of each cable  64 - 66  toward bracket members  54 , as shown in  FIG. 6 . As each winch  80 ,  81 , and  82  is similarly formed, a detailed description will follow to  FIG. 7  in describing winch  80  with an understanding that cable climbing members  81  and  82  include corresponding structure. Winch  80  includes a housing  85  that supports a motor  88 , a cable climbing portion  90  and a shackle  93 . Shackle  93  is connected to bracket element  57  through a coupler  96 . Once all cable climbing members  80 - 82  are connected to corresponding bracket elements  57 , telescoping sections  38 - 40  of hydraulic jacking cylinders  34  are further lowered transferring support of third wind turbine blade  9  from support members  25 - 27  to cable climbing members  80 - 82  as shown in  FIG. 8 . At this point, support members  25 - 27  may be removed, and cable climbing members  80 - 82  shifted or climbed down cables  64 - 66  to lower third wind turbine blade  9  from support hub  4  as shown in  FIG. 9 . The above steps may be revised to raise and install a new wind turbine blade. 
         [0023]    At this point it should be understood that the exemplary embodiments describe a system for lowering and raising wind turbine blades without the need for ground-based cranes. The exemplary embodiments employ cable climbing members that are controlled to climb up cables suspended from the support hub and subsequently climb down the cables with the wind turbine blade. It should also be understood that while the support members are described as threaded rods, other structures may be employed. Further, while the wind turbine blade is described as being stepped down through the support members using multiple, successive operations, a single step down may also be employed. Further, it should be understood that a new blade can be raised and secured to the hub by reversing the process described above. 
         [0024]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.