Abstract:
A method of replacing a wind turbine blade includes connecting a plurality of first hoisting devices between a wind turbine support hub and the wind turbine blade, suspending the wind turbine blade from the wind turbine support hub through the plurality of first hoisting devices, connecting a plurality of second hoisting devices between the wind turbine support hub and the wind turbine blade, supporting the wind turbine support blade with the plurality of second hoisting devices, disconnecting the plurality of first hoisting devices from the wind turbine blade, and lowering the wind turbine blade to the ground.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Continuation-in-Part of U.S. application Ser. No. 13/658,359 filed Oct. 23, 2012, the disclosure of which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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. 
         [0004]    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 
       [0005]    According to one aspect of an exemplary embodiment, a method of replacing a wind turbine blade includes connecting a plurality of first hoisting devices between a wind turbine support hub and the wind turbine blade, suspending the wind turbine blade from the wind turbine support hub through the plurality of first hoisting devices, connecting a plurality of second hoisting devices between the wind turbine support hub and the wind turbine blade, supporting the wind turbine blade with the plurality of second hoisting devices, disconnecting the plurality of first hoisting devices from the wind turbine blade, and lowering the wind turbine blade to the ground. 
         [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; 
           [0016]      FIG. 9  depicts the wind turbine blade being lowered toward ground; 
           [0017]      FIG. 10  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 another exemplary embodiment 
           [0018]      FIG. 11  is a partial perspective view the wind turbine blade of  FIG. 10  suspended a first distance from the wind turbine support hub by plurality of first hoisting devices in accordance with an aspect of an exemplary embodiment; 
           [0019]      FIG. 12  is a partial perspective view of the wind turbine blade of  FIG. 11  depicting attachment of a plurality of hook elements, in accordance with an aspect of an exemplary embodiment; 
           [0020]      FIG. 13  is a partial perspective view of the wind turbine blade of  FIG. 12  suspended from the wind turbine support hub through the plurality of first hoisting devices and a plurality of second hoisting devices; 
           [0021]      FIG. 14  is a partial perspective view of the wind turbine blade of  FIG. 13  supported from the wind turbine support hub by the plurality of second hoisting devices following completion of a handshake maneuver; 
           [0022]      FIG. 15  depicts the wind turbine blade of  FIG. 14  being lowered from the wind turbine support hub without the use of a crane by the plurality of second lifting members; and 
           [0023]      FIG. 16  depicts the wind turbine blade of  FIG. 15  resting on the ground. 
       
    
    
       [0024]    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 
       [0025]    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 a first end or root portion  11  and a second end or tip portion  12 . Of course, first and second wind turbine blades  7  and  8  also include first end or root portions (not separately labeled) as well as second end or tip portions (also 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 . 
         [0026]    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 . 
         [0027]    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 . 
         [0028]    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 . 
         [0029]    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. 
         [0030]    Reference will now follow to  FIGS. 10-16 , wherein like reference numbers represent corresponding parts in the respective views, in describing another exemplary embodiment of the present invention. Root portion  11  of wind turbine blade  9  includes an inner surface  194 . A plurality of hook members, one of which is indicated at  200 , is attached to inner surface  194  of root portion  11 . Prior to lowering wind turbine blade  9  to the ground, a tip rigging bracket  201  ( FIG. 15 ) is secured to adjacent to tip portion  12 . A ground based tip rigging line or tether  202  may be secured or connected to tip rigging bracket  201 . As will be detailed more fully below, tether  202  allows personnel to shift tip portion  12  as wind turbine blade  9  is lowered to the ground. 
         [0031]    A plurality of first hoisting devices, one of which is indicated at  204 , is secured between support hub  4  and wind turbine blade  9 . Each of the plurality of first hoisting devices  204  may take the form of a chain hoist  206  having a first end  208  supported in support hub  4  and a second end  209  including a shackle  210  that is coupled to hook member  200 . One or more chains (not separately labeled) may extend between first and second ends  208  and  209 . Once connected, wind turbine blade  9  may be disconnected from blade receiving portion  18 . After freeing array of mechanical fasteners  14 , wind turbine blade  9  may be lowered a first distance from wind turbine support hub  4  by plurality of first hoisting devices  204 , as shown in  FIG. 11 . 
         [0032]    A plurality of hook elements, one of which is indicated at  219 , may be secured to array of mechanical fasteners  14 , as shown in  FIG. 12 . Each hook element  219  includes a base portion  221  and a hook eye portion  222 . Base portion  221  may include one or more passages (not separately labeled) receptive to a corresponding one of array of mechanical fasteners  14 . After connecting hook elements  219  to root portion  11 , a plurality of second hoisting devices, one of which is indicated at  230 , is connected between wind turbine support hub  4  and wind turbine blade  9 , as shown in  FIG. 13 . Each of the plurality of second hoisting devices  230  may take the form of a block and tackle  232  that may be lifted up to personnel in wind turbine support hub  4 . Each block and tackle  232  includes a first end portion  234  fixedly supported within wind turbine support hub  4  and a second end portion  235  coupled to hook eye portion  222 . A cable or rope  238  is threaded through pulleys (not separately labeled) carried by first and second end portions  234  and  235 . Rope  238  includes a tag end  240  that extends to the ground. 
         [0033]    A handshake maneuver is performed after attaching the plurality of second hoisting devices  230 . During the handshake maneuver, the plurality of first hoisting devices  204  are operated such that wind turbine blade  9  is supported by the plurality of second hoisting devices  230 . Once wind turbine blade  9  is supported by the plurality of second hoisting devices  230 , the plurality of first hoisting devices  204  may be disconnected and removed, such as shown in  FIG. 14 . The plurality of second hoisting devices  230  may be operated to lower wind turbine blade  9  toward the ground, as shown in  FIG. 15 . While lowering, tension may be applied to tether  202  to gradually move wind turbine blade  9  from a generally vertical orientation to a generally horizontal position. Wind turbine blade  9  may then be landed, as shown in  FIG. 16 . Tension in tether  202  may be applied through ground based winches or by a small mobile crane. 
         [0034]    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 multiple hoisting devices that are used to lower the wind turbine blade to the ground without the need for large, ground based cranes. It should also be understood that the number and type of hoisting devices may vary. Further, it should be understood that a new blade can be raised and secured to the hub by reversing the process described above. 
         [0035]    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.