Method for retrofitting a wind turbine rotor blade with a replacement blade tip section

Abstract

A method for retrofitting a wind turbine blade (28) with a replacement blade tip segment (30) includes producing a replacement blade tip segment (30) having an internal beam receiver section (54); and producing a beam structure (40). An existing blade tip segment (29) is cut off from the wind turbine blade, wherein the cut defines a chordal connection line (34) at the remaining blade root section (32) of the wind turbine blade. The beam structure (40) is secured into the spar structure (42) of the blade root section. The replacement blade tip segment is aligned and connected to the blade root section in the spanwise direction to move the beam structure into the beam receiver section. A finishing surface may be provided to the blade shell members (31, 33) of the blade root section and the replacement tip segment at the connection line.

Description

Technical Field

[0001] The present subject matter generally relates to wind turbine rotor blades, and more particularly, to a method for in-field retrofit of an existing blade tip section with a replacement blade tip section. Background Art

[0002] Wind power is considered to be one of the cleanest and most environmentally friendly energy sources currently available, and wind turbines have received increased attention in this regard. Modern wind turbines typically include a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from the wind using known airfoil principles and transfer the kinetic energy through rotation to cause a shaft to rotate, which shaft couples the rotor blades to the gearbox or, if no gearbox is used, directly to the generator. The generator then converts the mechanical energy into electrical energy that can be deployed to the public power grid.

[0003] Wind turbine rotor blades generally include a body shell that is formed from two shell halves of composite laminate material. The shell halves are generally manufactured using a molding process and are then joined together along corresponding ends of the rotor blade. Generally, the body shell is relatively lightweight and has structural properties (e.g., stiffness, buckling resistance, and strength) that are not configured to withstand the bending moments and other loads imposed on the rotor blade during operation.

[0004] In some instances, it may be desirable to modify the rotor blades on a wind turbine in the field during operation. For example, it may be desirable to change the physical characteristics of the blade for noise reduction benefits or to change the power characteristics of the blade. Such modifications may require replacement of an existing blade tip with a different blade tip section. However, retrofit of an existing blade tip is a difficult and challenging process, particularly if the process is performed in the field (at a wind turbine site). Additionally, the connection between the replacement blade tip section and the existing blade root section typically indicates the maximum load limit of the blade. Therefore, the retrofit blade tip section is limited to a relatively short length.

[0005] As the size of wind turbine rotor blades has increased significantly in recent years, difficulties have arisen in overall manufacturing as well as the transportation and shipping of the blades to the site. In response, the industry has developed segmented wind turbine rotor blades, where individual blade segments are manufactured and transported to the site for assembly into a complete blade ("joined" blade). In some configurations, the blade segments are joined together by a beam structure that extends spanwise from one blade segment into a receiving section of another blade segment. For example, referring to U.S. Patent Publication No. 2015 / 0369211, which describes a first blade segment having a longitudinally extending beam structure that is structurally connected to a second blade segment at a receiving section. The beam structure forms part of the internal spar structure for the blade and includes a shear web connected to a suction side spar cap and a pressure side spar cap. A plurality of bolt joints are provided on the beam structure for connection to the receiving section in the second blade segment, and the plurality of bolt joints are positioned at a chordwise joint between the blade segments.

[0006] Similarly, U.S. Patent Publication No. 2011 / 0091326 describes a joined blade where a first blade portion and a second blade portion extend in opposite directions from a joint. Each blade portion includes a spar section that forms a structural component of the blade and extends longitudinally, where the first blade portion and the second blade portion are structurally connected by a spar bridge that joins the spar sections. The spar bridge can be an extension of one of the spar sections that is received in a receiving spar section of the other blade portion. When the extending spar section can be received in the receiving spar section, the extending spar cap and the receiving spar cap can overlap each other along at least a portion of the length of the extending spar section. To limit the material thickness of the overlapping spar caps, the reference describes that the thickness of the receiving spar cap can taper down towards the joint (i.e., along at least a portion of the length of the receiving spar section).

[0007] However, the joined blade structure has not been implemented in a manner suitable for retrofitting existing blades. Thus, a feasible method of using a joined blade structure to retrofit blades in the field to allow the use of longer blade tip segments would be an advantageous improvement in the art. SUMMARY OF THE INVENTION

[0008] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned by practice of the invention.

[0009] In one aspect, the present disclosure relates to a method for retrofitting a wind turbine blade with a replacement blade tip section. The method includes providing a replacement blade tip section having an internal beam receiver section (such as an end - opening box - beam configuration). A complementary beam structure (such as a box - beam structure) is also provided, having a size to slide within the receiver section. The existing blade tip section is cut off from the wind turbine blade, where the cut defines a chordal connection line at the remaining blade root section of the blade. The beam structure is then fitted into and fixed to the existing spar structure of the blade root section. The replacement blade tip section is then aligned in the spanwise orientation and connected to the blade root section such that the beam structure is moved into the beam receiver section. Once the replacement blade tip section is fixed to the blade root section (e.g., by using bolts or pins at various locations to connect the beam structure within the receiver section), the blade shell member can be repaired or finished at the connection line, e.g., by a fiberglass, epoxy, or other repair - type finishing process.

[0010] In certain embodiments, the wind turbine blade is operated on the wind turbine at the site location, where the retrofit process is performed with the wind turbine blade in the up - tower position on the wind turbine rotor hub. Alternatively, the wind turbine blade can be removed from the hub and lowered using any suitable process, and the retrofit process is performed with the wind turbine blade in the down - tower position relative to the rotor hub. In still other embodiments, the retrofit process can be performed at any suitable off - site location.

[0011] The beam receiver section can be formed separately from the replacement blade tip section and a spar structure is incorporated within the replacement blade tip section. Alternatively, the beam receiver section can be formed as an integral part or member of the spar structure.

[0012] The replacement blade tip section can be pre - manufactured and transported to the site location for the retrofit process. In certain embodiments, it may be desirable to produce and maintain an inventory of replacement blade tip sections, where for the retrofit process, one of the replacement blade tip sections is selected from the inventory and transported to the site location.

[0013] Certain embodiments can include modifying the spar structure in the blade root section to accept the beam structure. These modifications can include, for example, the removal of a spanwise section of the shear web adjacent to the connection line, where the tapered end of the beam structure is then fitted between the remaining shear webs such that the opposing ends of the beam structure extend from the shear webs and become extensions of the spar structure.

[0014] In addition, some embodiments may include modifying the blade root section by tapering a section of the housing member of the blade root section toward the attachment line to receive the beam structure. This tapered section allows for an overlap with a portion of the housing member that replaces the blade tip section and accommodates the insertion of the beam structure into the spar structure in the blade root section.

[0015] To secure the beam structure to the spar structure in the blade root section of the blade, one embodiment of the method includes drilling a spanwise pattern of holes through the blade housing member of the blade root section to provide an internal passage to the beam structure and the spar structure, and then sequentially injecting an adhesive into the holes. The pattern of holes may be defined to allow the adhesive to flow along a portion of the beam structure between the tapered end of the beam structure and the shear web, and around the beam structure, where a section of the shear web adjacent to the attachment line is removed. During this sequential injection process, the first of the injection holes or a plurality thereof are injected until the adhesive flows from an adjacent one or more holes. Then, the injected holes are plugged or sealed, and adjacent holes are injected. This process proceeds along the pattern of holes to ensure complete injection with no internal voids or with minimal internal voids between the beam structure and the existing spar structure and the housing member.

[0016] The finishing process on the blade housing member may include any conventional repair or finishing technique to provide a relatively smooth and aerodynamic surface at the attachment line between the housing members of the replacement blade tip section and the root end blade section. The finishing may include the application of a sealing tape wrapped around the blade housing member at the attachment line.

[0017] The present invention also encompasses a method for manufacturing a wind turbine blade that is preparatory for subsequent retrofit with a replacement blade tip section. Embodiments of the method include providing a continuous spar structure to the wind turbine blade from the root end section to the tip section of the blade. The spar structure may include, for example, opposing shear webs and opposing spar caps that define a box beam spar structure. At a pre-defined spanwise location, one of a spanwise extending beam structure or a spanwise extending receiver section is incorporated with respect to the spar structure by securing the root end of the spar structure or the receiver section to the spar structure. The tip end of the beam structure or the receiver section does not have a spar structure. If used, the beam structure has a size for insertion into a mating receiver section within the replacement blade tip section at a later time. Similarly, if used, the receiver section is sized to receive a mating beam structure extending from the replacement blade tip section. In embodiments where the spar structure includes opposing shear webs, the root end of the beam structure or the receiver section may be secured, for example, using an adhesive between the shear webs.

[0018] The method may also include, at a time after manufacturing a wind turbine blade, retrofitting the wind turbine blade by utilizing a replacement blade tip segment by: cutting an existing blade tip segment from the wind turbine blade at a chordwise connection line such that the end end of the spar structure extends spanwise beyond the chordwise connection line from the remaining blade root segment, or the receiver segment is exposed at the chordwise connection line. The spar structure in the blade root segment extending along the end end of the spar structure or the receiver segment may also be removed such that only the spar structure extends from the blade root segment, or the receiver segment is exposed at the chordwise connection line. Next, the replacement blade tip segment is aligned and connected to the blade root segment in the spanwise direction such that the spar structure is moved into the receiver segment of the replacement blade tip segment, or the spar structure extending from the replacement tip segment slides into the receiver segment. Next, a finishing surface may be provided at the connection line to the blade shell members of the blade root segment and the replacement tip segment.

[0019] As discussed above, the spar structure may include opposing shear webs, and the root end of the spar structure or the receiver segment is between the shear webs and fixed to the shear webs, and wherein removal of the spar structure includes cutting off the shear webs along the end end of the spar structure or the end end of the receiver segment.

[0020] Other aspects of the retrofit process discussed above apply to blade manufacturing and subsequent retrofit methods.

[0021] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A complete and open disclosure of the invention, including the best mode thereof for those skilled in the art, is set forth in the specification, which makes reference to the accompanying drawings, in which:

[0023] Figure 1 A perspective view of an embodiment of a wind turbine having a blade that can be retrofitted is shown in accordance with the present disclosure;

[0024] Figure 2 The retrofit of a wind turbine rotor blade utilizing a replacement tip blade segment is conceptually depicted in accordance with the present disclosure;

[0025] Figure 3 A view of an embodiment of a root end blade segment having a spar structure fixed therein;

[0026] Figure 4 A view of an embodiment of a replacement tip blade segment having a receiver segment fixed or formed therein;

[0027] Figure 5 Partial cross-sectional view of a retrofitted wind turbine blade according to an embodiment of the present disclosure;

[0028] Figures 6a to 6h Sequential conceptual view of an embodiment of a retrofit process according to an aspect of the present disclosure;

[0029] Figures 7a to 7c Sequential conceptual view of an embodiment for the manufacture and subsequent retrofit of a wind turbine blade according to an aspect of the present disclosure; and

[0030] Figures 8a to 8c Sequential conceptual view of an alternative embodiment for the manufacture and subsequent retrofit of a wind turbine blade according to an aspect of the present disclosure. Detailed Description

[0031] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention and not limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features shown or described as part of one embodiment can be used with another embodiment to yield yet another embodiment. Accordingly, it is intended that the present invention cover such modifications and variations that come within the scope of the appended claims and their equivalents.

[0032] Generally, the subject matter relates to methods for retrofitting existing wind turbine rotor blades, including in - service blades in the field, by replacing blade tip segments.

[0033] Now referring to the drawings, Figure 1 Side view of an exemplary wind turbine 10 having a plurality of rotor blades 28 that can be retrofitted according to aspects of the present disclosure. The illustrated wind turbine 10 is a horizontal axis wind turbine. Alternatively, the wind turbine 10 can be a vertical axis wind turbine. The wind turbine 10 includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, a generator 18 positioned within the nacelle 16, a gearbox 20 coupled to the generator 18, and a rotor 22 rotatably coupled to the gearbox 20 by a rotor shaft 24. The rotor 22 includes a rotatable hub 26 to which the rotor blades 28 are coupled and extend outwardly from the rotatable hub 26. Each rotor blade 28 includes a blade tip 17 and a blade root 19, as well as corresponding root end blade segments 32 and tip end blade segments 29.

[0034] Figure 2Schematic plan view of a retrofit process according to aspects of the present disclosure, in which an existing rotor blade 28 is made into a connected rotor blade by cutting out an existing blade tip segment 29 and fitting a replacement blade tip segment 30 to a root end blade segment 32 (indicated by arrow 38). Also refer to Figure 5 , in the resulting retrofitted connected blade 70, the root end blade segment 32 and the replacement blade tip segment 30 extend in opposite directions from a chordal connection 34. Each of the blade segments 30, 32 includes a pressure side housing member 31 and a suction side housing member 33. The blade segments 30, 32 are connected by an internal connection structure 36 that extends into both blade segments 30, 32 to facilitate the connection of the blade segments 30, 32, as described in more detail below. The blade 70 includes a leading edge 74 and a trailing edge 76, as well as a root portion 19 and a tip portion 17. The blade 28 extends in a longitudinal spanwise direction, and as is well known in the art, the upper housing member 31 and the lower housing member 33 are joined together at the leading edge 74 and the trailing edge 76. The blade 70 includes an internal cavity in which various structural components, such as spar caps 46 and shear webs 44, are constructed. The construction and function of the internal structural members of the blade 70 are well known to those skilled in the art and, for the understanding and appreciation of the present invention, do not need to be described in detail herein.

[0035] Aspects of the method include separately manufacturing a replacement blade tip segment 30 having an internal beam receiver section 54, as Figure 2 , Figure 4 and Figure 5 shown, the internal beam receiver section 54 is intended to receive a beam structure 40 fixed in the blade root segment 32. The internal connection structure 36 associated with the receiver section includes a spar structure member 42 that extends spanwise for connection to the beam structure 40 along the length of the receiver section 54. The spar structure member 42 may include a shear web 56 and a spar cap 58 constructed as a box beam having an open end adjacent to the chordal connection 34. The receiver section 54 may include a wall 57, as explained in more detail below.

[0036] As particularly seen in Figure 4 and Figure 5 , the receiver section 54 may be integrally formed with the spar structure 42 in the replacement blade tip segment, where the receiver section 54 is substantially bounded by the wall 57. In an alternative embodiment, the receiver section 54 may be a separately manufactured box beam member that is fitted into and fixed to the existing spar structure 42 in the replacement blade tip segment 30.

[0037] The receiving section 54 may include any combination of bolts or pins 53 and associated slots 50 for interconnecting with corresponding pins or slots of the beam structure 40. For example, the slots 50 may be provided in the wall 57 of the receiving section 54 for receiving a pin 52 fixed to the end face of the end end 43 of the beam structure 40. The beam structure 40 may also include opposing slots 50 that are proximal to the chordal connection 34 and oriented in the chordal direction. A bushing may be present within each slot 50, and the bushing is arranged to be in a tight interference fit with a chordally extending pin 53 that extends through the shear web 56 in the receiving section 54 and the beam structure 40 to fix the beam structure 40 within the receiving section 54.

[0038] The replacement blade tip segment 30 may be pre-produced and transported to the site for the retrofit process. Desirably, an inventory 60 ( Figure 6g ) of replacement blade tip segments 30 is produced and maintained, from which one of the replacement blade tip segments 30 is selected and transported to the site for the retrofit process.

[0039] Referring Figure 3 and Figure 5 , the beam structure 40 is also a separately formed member of the connection structure 36 and is configured to mate with and be fixed within an existing spar structure 42 in the blade root segment 32. In a particular embodiment, the beam structure 40 includes a root end 41 and an end end 43 and may be configured as a box beam structure having opposing spar caps and interconnected shear webs. Other configurations are possible (including solid components). For easier insertion and fixation between the shear webs 44 in the blade root segment 32, the root end 41 may be tapered in the spanwise direction. An inventory of beam structures 40 may be produced and stored for use on a "as-needed" basis.

[0040] Referring Figure 3 , the method may include modifying the existing spar structure 42 in the blade root segment 32 to receive the root end 41 of the beam structure 40. These modifications may include, for example, removal of the spanwise section 62 of the shear web 44 adjacent to the connection line 34. The spar cap 46 may also be removed along this section 62. The blade shell members 31, 33 may also be tapered towards the connection line 34 along the section 62. This tapered section allows for partial overlap with the shell members 31, 33 of the replacement blade tip segment 30 and accommodates the insertion of the beam structure 40 into the spar structure 42 in the blade root segment 32.

[0041] After these modifications, the tapered end 41 of the beam structure 40 then mates between the remaining shear webs 44 such that the opposing end ends 43 of the beam structure 40 extend spanwise from the shear webs 44 beyond the chordal connection line 34. The beam structure 40 thus becomes an extension of the spar structure 42 of the blade root segment 32.

[0042] A variety of methods can be used to fix the beam structure 40 to the spar structure 42 in the blade root segment 32. In Figure 3 the specific embodiment depicted, the method includes drilling a spanwise pattern of holes 64 through the blade shell member 33 to provide internal access to the beam structure 40 and the remaining spar structure 42. The pattern of holes 64 can be relatively widely defined in the region 62, where a portion of the spar structure 42 is removed so that the adhesive injected through these holes 64 will substantially fill the internal region between the shells 31, 33. The pattern of holes 64 can narrow towards the spar structure 42 until the holes 64 are positioned between the shear webs 44 so that the adhesive injected in these holes 64 substantially fills any space between the beam structure 40 and the spar structure 42 along the section 66. Starting from the connection line 34 (which is blocked for this process), the adhesive is injected sequentially, where the first or more of the holes 64 are injected until the adhesive flows from an adjacent one or more holes 64. Then, the injected holes 64 are blocked or sealed, and the adjacent holes 64 are injected until the adhesive flows from the next downstream hole 64. This injection process proceeds along the pattern of holes 64 to ensure complete injection with no internal voids or with minimal internal voids between the beam structure 40 and the existing spar structure 42 and the shell members 31, 33.

[0043] Figures 6a to 6h Embodiments of current methods in the art are depicted sequentially, where an existing rotor blade 28 remains attached to the rotor hub 26 and the retrofit process is performed with the blade 28 in the up-tower position while remaining on the hub 26. Alternatively, an existing wind turbine blade 28 can be removed from the hub 26 and lowered using any suitable process, and the retrofit process is performed with the wind turbine blade 28 in the down-tower position relative to the rotor hub 26.

[0044] Figure 6a An existing rotor blade 28 on the rotor hub 26 at the six o'clock position is depicted, the blade 28 including a root end blade segment 32 and an integrated blade tip segment 29.

[0045] Figure 6b A chordwise cut made in the blade 28 at the location defining the chordwise connection line 34 is depicted. The cut is made completely through the blade 28, where the existing blade tip segment 29 is removed, as Figure 6c depicted. The remaining spar structure 42 is depicted in the blade root segment 32.

[0046] Figure 6d Modifications to the blade root segment 32 adjacent to the connection line 34 are depicted, including the removal of a section of the spar structure 42 along the section 62 and a possible taper of the shell members 31, 33, as discussed above.

[0047] Figure 6e Depicts the spanwise insertion of a separately formed beam structure 40 into a modified spar structure 42, where the tapered root end 41 is inserted between shear webs 44 in the blade root section 32.

[0048] Figure 6f Depicts the process of securing the beam structure 40 to the spar structure 42 using the adhesive injection process discussed above.

[0049] Figure 6g Depicts the selection of one of the preformed replacement blade tip segments 30 from inventory 60 and the spanwise connection of segment 30 to the blade root section 32. Specifically, as the replacement blade tip segment 30 is moved in the spanwise direction, the receiving section 54 within segment 30 slides onto the portion of the beam structure 40 that extends beyond the connection line 34. To secure the beam structure 40 to the receiving section 54, the end pins 52 on the root end 43 of the beam structure 40 extend through slots in the wall 37 of the receiving section 54, and the chordwise-oriented slots 50 in the receiving section 54 are aligned with corresponding slots 50. The chordwise pins 53 are then inserted through the aligned slots 50, as Figure 5 specifically seen in.

[0050] Figure 6h Depicts the replacement blade tip segment 30 secured to the blade root section 32 and the blade shell members with a finish (e.g., fiberglass, epoxy, or other repair-type finish that provides a relatively smooth and aerodynamic surface at the connection line 34 between the replacement blade tip segment 30 and the root end blade section 32) provided at the connection line 34. The finish may include a sealing strip 68 that wraps around the blade shell members 31, 33 at the connection line 34. Thus, Figure 6h the blade in Figure 5 is a complete retrofit blade 70, as also depicted in

[0051] As generally depicted in Figures 7a-7c and Figures 8a-8c The present invention also encompasses a method for manufacturing a wind turbine blade 28 that is preparatory for subsequent retrofit using a replacement blade tip segment. A specific embodiment of the method is in Figures 7a-7cDepicted. Like any number of conventional wind turbine blade designs, the wind turbine blade 28 is provided with a continuous spar structure 42 extending from the root section 19 to the tip section 17 of the blade. The spar structure 42 can include, for example, opposing shear webs 44 and opposing spar caps 46, which define a box beam spar structure 42. At a predefined spanwise location, the root end 41 of the beam structure 40 is fixed to the spar structure 42 and the tip end 43 of the beam structure 40 is substantially unattached to the spar structure 42, and the beam structure 40 extending in the spanwise direction is incorporated with respect to the spar structure 42 during the fabrication of the blade 28. As discussed in detail above, the beam structure 40 has a size for insertion into a receiver section 54 ( Figure 5 ) within a replacement blade tip segment 30 at a later time. In embodiments where the spar structure 42 includes opposing shear webs 44, the root end 41 of the beam structure 40 can be fixed, for example, using an adhesive between the shear webs 44.

[0052] Figure 7b and Figure 7c Depicted: The wind turbine blade 28 is prepared for subsequent modification using a replacement blade tip segment by cutting at least the shell member of the existing blade tip segment 29 from the wind turbine blade 28 at the chordwise connection line 34 such that the tip end 43 of the beam structure extends in the spanwise direction from the remaining blade root segment 32 beyond the chordwise connection line 34, as discussed above. The spar structure 42 in the blade root segment 32 extending along the tip end 43 of the beam structure 40 can be removed either simultaneously or after cutting off the blade shell member, so that only the beam structure 40 extends from the blade root segment 32, as Figure 7c depicted. Then, during the modification process discussed above, the replacement blade tip segment 30 can be aligned and connected to the blade root segment 32.

[0053] Figures 8a to 8c Embodiments of provide a prepared receiver section 54 to the wind turbine blade 28, the prepared receiver section 54 having a root end 55 fixed to the spar structure 42. The opposite end of the receiver section 54 extends at least to the location of the chordwise connection line 34 and can be fixed to the web 44 along the entire length of the receiver section 54. As Figure 8b and Figure 8c depicted, when the blade tip segment 29 is cut off from the blade 28, the spar structure including the web 44 is cut back to the connection line 34. If the receiver section 54 extends beyond the connection line 34 (as Figure 8b depicted), then the length of the receiver section 54 can also be trimmed to the connection line 34 such that the open end of the receiver section 54 is exposed at the connection line ([[]] Figure 8c ) for receiving the beam structure that will extend from the replacement blade tip segment.

[0054] The written description uses examples to disclose the invention (including the best mode), and also enables those skilled in the art to practice the invention (including making and using any device or system and performing any incorporated method). The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If these other examples include structural elements that do not differ from the literal language of the claims, or if these other examples include equivalent structural elements that do not differ significantly from the literal language of the claims, then these other examples are intended to be within the scope of the claims.

Claims

1. A method for retrofitting a wind turbine blade (28) using a replacement blade tip segment (30), which comprises: providing a replacement blade tip segment (30) having an internal beam receiver section (54); providing a beam structure (40); cutting an existing blade tip segment (29) from the wind turbine blade (28), wherein the cutting defines a chordal connection line (34) at the remaining blade root segment (32) of the wind turbine blade; fixing the beam structure (40) into the spar structure (42) of the blade root segment (32); aligning and connecting the replacement blade tip segment (30) with the blade root segment (32) in the spanwise direction so that the beam structure (40) moves into the beam receiver section (54); and providing a finish surface at the connection line (34) to the blade shell members (31, 33) of the blade root segment (32) and the replacement blade tip segment (30), wherein the method further comprises modifying the spar structure (42) in the blade root segment (32) to receive the beam structure (40) by removing a section (62) of a shear web (44) adjacent to the connection line (34), and moving a tapered end (43) of the beam structure (40) between the shear webs (44) such that opposite ends of the beam structure extend spanwise from the spar structure (42) and become extensions of the spar structure (42), and the fixing of the beam structure (40) into the spar structure (42) of the blade root segment (32) includes drilling a spanwise pattern of holes (64) through the blade shell members (31, 33) of the blade root segment (32) to provide access to the beam structure and the spar structure, and sequentially injecting an adhesive into the holes, wherein the pattern of holes allows the adhesive to be along a portion of the beam structure between the tapered end and the shear web of the beam structure, and around the injection of the beam structure, wherein the section (62) of the shear web (44) is removed adjacent to the connection line (34).

2. The method according to claim 1, wherein, the wind turbine blade (28) operates on a wind turbine (10) at a site (15), including performing the retrofit process with the wind turbine blade in an upper tower position on the rotor hub (26) of the wind turbine, removing and lowering the wind turbine blade from the rotor hub, and performing the retrofit process with the wind turbine blade in a lower tower position relative to the rotor hub.

3. The method according to claim 2, wherein, the internal beam receiver section (54) is formed separately from the replacement blade tip segment (30), and the spar structure (42) is incorporated in the replacement blade tip segment.

4. The method according to claim 3, wherein, The method further includes producing and maintaining an inventory (60) of the replacement blade tip segments (30), wherein for the retrofit process, one of the replacement blade tip segments is selected from the inventory and transported to the site location (15).

5. The method according to claim 1, wherein, the method further includes tapering a section of the housing members (31, 33) of the blade root segment (32) towards the connection line (34).

6. The method according to any one of claims 1 to 4, wherein, providing a finish surface to the connection line (34) includes winding a seal (68) around the wind turbine blade (28) at the connection line (34).

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