WO2012075607A1

WO2012075607A1 - Methods and systems for assembling wind turbine tower

Info

Publication number: WO2012075607A1
Application number: PCT/CN2010/001996
Authority: WO
Inventors: Huaming Yao; Wenguan Fu
Original assignee: General Electric Company
Priority date: 2010-12-09
Filing date: 2010-12-09
Publication date: 2012-06-14

Abstract

A method for assembling a wind turbine tower includes providing a first tower section (116) and a second tower section (114), extending a guide line (322, 330) between the first tower section and the second tower section, and hoisting the first tower section above the second tower section. The method further includes vertically aligning the first tower section and the second tower section using the guide line and lowering the first tower section onto the second tower section along the guide line.

Description

METHODS AND SYSTEMS FOR ASSEMBLING

WIND TURBINE TOWER

BACKGROUND OF THE INVENTION

[0001] The subject matter described herein relates generally to towers and, more particularly, to methods and systems for assembling a wind turbine tower.

[0002] Many known wind turbines include a tower and a rotor mounted on the tower via a nacelle. The rotor includes a number of blades that facilitate converting wind energy into rotational energy. The rotor drives a generator through a gearbox via a rotor shaft, and the gearbox steps up the inherently low rotational speed of the rotor shaft such that the generator can convert the mechanical energy to electrical energy.

[0003] Many known wind turbine towers are erected by stacking a plurality of tubular tower sections. A base section is first installed on a foundation, and all remaining sections are sequentially stacked atop of the base section. Typically, each section is circumferentially aligned with the section upon which it is stacked. To obtain this circumferential alignment, it is common for installation personnel to stand near the top of a previously installed section in order to guide a subsequent section into circumferential alignment with the previously installed section as the subsequent section is being lowered. However, this practice of aligning tower sections can be relatively imprecise. As such, it would be useful to provide methods and systems for assembling a wind turbine tower in a more precise manner.

BRIEF DESCRIPTION OF THE INVENTION

[0004] In one aspect, a method for assembling a wind turbine tower is provided. The method includes providing a first tower section and a second tower section, extending a guide line between the first tower section and the second tower section, and hoisting the first tower section above the second tower section. The method further includes vertically aligning the first tower section and the second tower section using the guide line and lowering the first tower section onto the second tower section along the guide line.

[0005] In another aspect, a system for assembling a wind turbine tower having a first tower section and a second tower section is provided. The system includes a lifting assembly configured to hoist the first tower section above the second tower section and at least one alignment assembly including a guide line. The alignment assembly is configured to vertically align the first tower section and the second tower section using the guide line when the guide line extends between the first tower section and the second tower section. The lifting assembly is configured to lower the first tower section onto the second tower section along the guide line.

[0006] In a further aspect, a method for assembling a wind turbine tower is provided. The method includes providing a first tower section having a first upper end and a first lower end, wherein a first annular flange defining a first pair of diametrically opposed apertures is coupled to the first lower end. The method also includes providing a second tower section having a second upper end and a second lower end, wherein a second annular flange defining a second pair of diametrically opposed apertures is coupled to the second upper end. The method further includes extending a first guide line through a first aperture of the first pair of diametrically opposed apertures and through a first aperture of the second pair of diametrically opposed apertures. The method further includes extending a second guide line through a second aperture of the first pair of diametrically opposed apertures and through a second aperture of the second pair of diametrically opposed apertures. The method also includes fastening each of the first guide line and the second guide line to one of the first tower section and the second tower section, hoisting the first tower section above the second tower section, and tensioning at least one of the first guide line and the second guide line to facilitate vertically aligning the first tower section and the second tower section. The method further includes lowering, along the guide lines, the first tower section onto the second tower section such that the first flange is seated on the second flange with the first pair of diametrically opposed apertures substantially aligned with the second pair of diametrically opposed apertures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a schematic illustration of an exemplary wind turbine;

[0008] Fig. 2 is a top view of a flange for use in tower sections of the wind turbine shown in Fig. 1 ;

[0009] Fig. 3 is a schematic illustration of a system for assembling the tower of the wind turbine shown in Fig. 1 ;

[0010] Fig. 4 is a schematic illustration of the system shown in Fig. 3 during a step of assembling the tower of the wind turbine shown in Fig. 1 ;

[0011] Fig. 5 is a schematic illustration of the system shown in Fig. 3 during a subsequent step of assembling the tower of the wind turbine shown in Fig. l ;

[0012] Fig. 6 is an enlarged sectional view of a portion of the system shown in Fig. 3 during the subsequent step shown in Fig. 5;

[0013] Fig. 7 is a top view of another portion of the system shown in Fig. 3 during the subsequent step shown in Fig. 5;

[0014] Fig. 8 is a schematic illustration of another system for assembling the tower of the wind turbine shown in Fig. 1 ; and

[0015] Fig. 9 is a flow chart of a method for assembling a wind turbine tower. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following detailed description describes methods and systems for assembling a wind turbine tower by way of example and not by way of limitation. The description enables one of ordinary skill in the art to make and use the disclosure, and the description describes several embodiments of the disclosure, including what is presently believed to be the best mode of carrying out the disclosure. The disclosure is described herein as being applied to an exemplary embodiment, namely, a wind turbine tower. However, it is contemplated that this disclosure has general application to towers in a broad range of systems and in a variety of applications other than wind turbines.

[0017] Fig. 1 is a schematic illustration of a wind turbine 100. In the exemplary embodiment, wind turbine 100 is a horizontal axis wind turbine. In other embodiments, wind turbine 100 may be a vertical axis wind turbine. Wind turbine 100 includes a tower 102 erected from a foundation 104, a nacelle assembly 106 mounted on tower 102, and a rotor 108 rotatably coupled to nacelle assembly 106. Rotor 108 includes a rotatable hub 1 10 and a plurality of blades 1 12 coupled to and extending outwardly from hub 1 10 to facilitate enabling kinetic energy of the wind to be converted into rotational energy and, subsequently, into electrical energy. In the exemplary embodiment, tower 102 has a plurality of sections including a base section 1 14, at least one intermediate section 116, and a top section 118. Each section 114, 1 16, 1 18 has an upper end 120 and a lower end 122 having any suitable shape (e.g., in the exemplary embodiment, base section 1 14 has an annular upper end 120, while intermediate and top sections 116, 1 18 have annular upper and lower ends 120, 122).

[0018] Fig. 2 is a top view of a flange 200 for use in tower sections 114, 116, 1 18. In the exemplary embodiment, flange 200 is annular and has a diameter 201 and a plurality of circumferentially spaced apertures 202 (e.g., apertures 202 include at least one pair of diametrically opposed apertures 204). An embodiment of flange 200 is coupled to upper end 120 of base section 1 14, upper and lower ends 120, 122 of each intermediate section 1 16, and upper and lower ends 120, 122 of top section 1 18 (e.g., each flange 200 of intermediate section 1 16 and top section 118 is arranged such that opposed apertures 204 of upper end 120 are substantially aligned with correspondingly opposed apertures 204 of lower end 122). Alternatively, flanges 200 may be arranged in any suitable manner that enables sections 1 14, 116, 1 18 to be stacked as described herein. Because each section 1 14, 116, 1 18 of tower 102 may be configured differently (e.g., each section 1 14, 116, 1 18 may be shaped differently), each flange 200 of tower 102 may also be configured differently (e.g., each flange 200 may have a different shape with a different size, number, and/or spacing of apertures 202). In other embodiments, flanges 200 may have any suitable configuration that facilitates enabling sections 114, 1 16, 1 18 of tower 102 to be stacked in the manner described herein. In the exemplary embodiment, intermediate section 1 16 is stacked on base section 1 14 by seating flange 200 of lower end 122 of intermediate section 1 16 on flange 200 of upper end 120 of base section 1 14, as described in more detail below.

[0019] Fig. 3 is a schematic illustration of a system 300 for assembling tower 102. In the exemplary embodiment, system 300 includes a lifting assembly 302, a first alignment assembly 304, and a second alignment assembly 306. Lifting assembly 302 includes at least one crane 308 having a boom 310, a lifting pulley 312 mounted on boom 310, a cable 314 extending along pulley 312, and a suitable mechanism for winding and unwinding cable 314 to facilitate lifting objects (e.g., sections 1 14, 1 16, 118 of tower 102). First alignment assembly 304 includes a first winding device 316 (e.g., a winch) mounted on a first base 318 (e.g., a concrete foundation or the ground), a first pulley 320 mounted on lifting assembly 302 (e.g., on boom 310), and a first guide line 322 (e.g., a rope) coupled to first winding device 316 and extending along first pulley 320. Similarly, second alignment assembly 306 includes a second winding device 324 (e.g., a winch) mounted on a second base 326 (e.g., a concrete foundation or the ground), a second pulley 328 mounted on lifting assembly 302 (e.g., on boom 310), and a second guide line 330 (e.g., a rope) coupled to second winding device 324 and extending along second pulley 328. First guide line 322 has a first free end 332, and second guide line 330 has a second free end 334. In some embodiments, winding devices 316, 324 and/or pulleys 320, 328 may be mounted on any suitable structures that facilitate enabling system 300 to function as described herein. Additionally, other embodiments of lifting assembly 302 may include any suitable device(s) that facilitate lifting objects in a manner that enables system 300 to function as described herein.

[0020] Figs. 4-7 are schematic illustrations of system 300 during assembly of tower 102. It should be noted that, while Figs. 4-7 illustrate stacking one intermediate section 116 on base section 1 14 using system 300, any suitable sections of tower 102 may be stacked in a similar manner using system 300. Prior to hoisting intermediate section 116, as described below, base section 1 14 is installed (e.g., on a foundation), and a pair of connectors 336 are mounted within (e.g., welded to an internal surface 338 of) base section 1 14 in a spaced apart relationship with flange 200, which is coupled to upper end 120 of base section 1 14, such that each connector 336 is below one of opposed apertures 204. Each connector 336 is configured for attaching one of guide lines 322, 330 to base section 1 14 (e.g., each connector 336 may be configured with an opening 340 sized to receive one of guide lines 322, 330, as described in more detail below).

[0021] With base section 114 installed and connectors 336 mounted within base section 1 14, first free end 332 is inserted through one opposed aperture 204 of flange 200 of upper end 120 of intermediate section 1 16 and through a correspondingly aligned opposed aperture 204 of flange 200 of lower end 122 of intermediate section 1 16. Second free end 334 is similarly inserted through the other opposed aperture 204 of flange 200 of upper end 120 of intermediate section 116 and through the correspondingly aligned other opposed aperture 204 of flange 200 of lower end 122 of intermediate section 1 16. Free ends 332, 334 are then inserted through correspondingly opposed apertures 204 of flange 200 of upper end 120 of base section 1 14.

[0022] Then, free ends 332, 334 are attached to connectors 336 (e.g., by inserting free ends 332, 334 through openings 340 of connectors 336 and by connecting stoppers 342 to free ends 332, 334 to prevent withdrawal of guide lines 322, 330 from opposed apertures 204 of flanges 200, thereby preventing detachment of guide lines 322, 330 from base section 114 while intermediate section 116 is being stacked on base section 1 14). Also, as shown in Figs. 4 and 5, pulleys 320, 328 are aligned with opposed apertures 204 of flange 200 on upper end 120 of base section 1 14 such that, when guide lines 322, 330 are tensioned using winding devices 316, 324, pulleys 320, 328 redirect the tension force in a longitudinal direction (e.g., a vertical direction 323) to orient segments of guide lines 322, 330, as described in more detail below. In some embodiments, any suitable number of connectors 336 may be mounted at any suitable location on base section 1 14, and any suitable number of guide lines 322, 330 may be attached to any number of connectors 336 in any suitable manner that enables stacking tower sections 1 14, 1 16, 1 18 as described herein. In other embodiments, guide lines 322, 330 may be connected to any suitable structure (e.g., to a platform within base section 1 14 or to an anchor in the foundation) in any suitable manner. Alternatively, guide lines 322, 330 may be extended between sections 1 14, 116, 1 18 in any suitable manner, and sections 1 14, 1 16, 1 18 may be aligned using any suitable devices that facilitate enabling system 300 to function as described herein.

[0023] With guide lines 322, 330 attached to connectors 336 of base section 1 14, intermediate section 116 is hoisted (Fig. 4) in the following manner. Cable 314 is connected to upper end 120 of intermediate section 1 16 (e.g., via an arrangement of straps 346 coupled to a plurality of metal rings 348 fastened to flange 200 of upper end 120 of intermediate section 1 16). Because crane 308 is oriented horizontally above base section 1 14 with pulley 312 positioned substantially centrally over base section 114, cable 314 extends through pulley 312 to redirect horizontal forces associated with cable 314 in vertical direction 323. In some embodiments, lifting assembly 302 may be configured to hoist intermediate section 116 using only cable 314, which is coupled to upper end 120 of intermediate section 1 16 (e.g., lifting assembly 302 may include only a single crane 308, as shown in Fig. 3). In other embodiments, lifting assembly 302 may be configured to hoist intermediate section 116 using one cable 314 coupled to upper end 120 of intermediate section 116 and another cable 314 coupled to lower end 122 of intermediate section 116 (e.g., lifting assembly 302 may include a pair of cranes 308, as shown in Fig. 4). Alternatively, intermediate section 116 may be hoisted by lifting assembly 302 in any suitable manner using any suitable devices that facilitate stacking sections 1 14, 1 16, 1 18 of tower 102 as described herein.

[0024] After intermediate section 1 16 is hoisted above base section 1 14, first winding device 316 and second winding device 324 are operated to tension (i.e., wind) at least one of guide lines 322, 330 (Fig. 5), thereby maneuvering intermediate section 1 16 into substantially vertical alignment with base section 114 (e.g., maneuvering intermediate section 1 16 such that opposed apertures 204 of flange 200 of lower end 122 of intermediate section 1 16 are substantially aligned with opposed apertures 204 of flange 200 of upper end 120 of base section 1 14). While intermediate section 1 16 is being maneuvered into alignment, intermediate section 1 16 is held at a substantially unchanged vertical position relative to base section 114 (i.e., intermediate section 116 is not lowered by lifting assembly 302). However, if lifting assembly 302 includes one or more cables 314 coupled to lower end 122 of intermediate section 1 16 (e.g., if intermediate section 1 16 is initially hoisted from the ground in a generally horizontal orientation), cable(s) 314 connected to lower end 122 may be loosened as guide lines 322, 330 are tensioned, thereby allowing lower end 122 of intermediate section 1 16 to be lowered in a controlled manner until intermediate section 1 16 is suspended in a vertical orientation above base section 1 14, at which point cable(s) 314 can be uncoupled from lower end 122. In other embodiments, intermediate section 116 may be hoisted above base section 1 14 in any suitable manner that facilitates stacking sections 1 14, 1 16, 118 as described herein.

[0025] With intermediate section 1 16 suspended in a substantially vertical orientation above base section 1 14 and with guide lines 322, 330 tensioned as shown in Fig. 5, intermediate section 1 16 is gradually lowered toward base section 114 until flange 200 of lower end 122 of intermediate section 1 16 is seated on flange 200 of upper end 120 of base section 1 14 (i.e., such that lower end 122 of intermediate section 116 and upper end 120 of base section 1 14 are substantially circumferentially aligned). In some embodiments, to facilitate assuring proper vertical alignment of sections 114, 1 16 prior to lowering intermediate section 116, a theodolite instrument 350 may be used to gauge an orientation of guide lines 322, 330 (e.g., a pair of theodolite instruments 350 may be arranged at an angle of about 90° relative each guide line 322, 330 to gauge an orientation of guide lines 322, 330 and, therefore, an alignment of intermediate section 1 16 and base section 1 14 prior to lowering intermediate section 116). In other embodiments, any number of any suitable instrument(s) may be used to gauge an orientation of guide lines 322, 330 and/or an alignment of sections 114, 1 16 prior to and/or during the lowering of intermediate section 116. Alternatively, system 300 may not include instruments for gauging an orientation of guide lines 322, 330.

[0026] Once flange 200 of lower end 122 of intermediate section 1 16 is seated on flange 200 of upper end 120 of base section 1 14 with apertures 202 substantially aligned, bolts are inserted through apertures 202 of flanges 200 (e.g., through the junction of intermediate section 1 16 and base section 1 14) to fasten intermediate section 1 16 to base section 1 14. Then, guide lines 322, 330 may be slackened, detached from connectors 336 (e.g., by disconnecting stoppers 342 from free ends 332, 334), and withdrawn from sections 114, 1 16 through opposed apertures 204 of flanges 200. Similarly, cable 314, arrangement of straps 346, and rings 348 may be detached from flange 200 of upper end 120 of intermediate section 1 16. Subsequently, other sections of tower 102 may be stacked atop intermediate section 1 16 in a similar manner. Additionally, it should be noted that, while flanges 200 are shown as extending radially inward in these embodiments, flanges 200 may suitably extend radially outward in other embodiments.

[0027] Fig. 8 is a schematic illustration of another system 400 for assembling tower 102. At least some of the components of system 400 are similar to the components of system 300 and will be referenced using like reference numerals. Again, while system 400 is described in the context of stacking an intermediate section 1 16 on base section 1 14, it should be noted that other sections of tower 102 may be stacked in a similar manner using system 400. In system 400, winding devices 316, 324 are mounted within base section 1 14 below flange 200, and connectors 336 are mounted within intermediate section 1 16 above flange 200. Free ends 332, 334 of guide lines 322, 330 are then inserted through opposed apertures 204 of flanges 200 and are attached to connectors 336 via stoppers 342, as described above. Intermediate section 116 may be hoisted and lowered in any suitable manner (e.g., using lifting assembly 302, as described above). Any suitable instruments (e.g., theodolite instruments 350) may be used to gauge an orientation of guide lines 322, 330 prior to lowering intermediate section 116 onto base section 1 14.

[0028] In this embodiment, while intermediate section 1 16 is being lowered, winding devices 316, 324 maintain tension in guide lines 322, 330 (i.e., wind guide lines 322, 330) and, therefore, maintain proper alignment of sections 114, 1 16 as intermediate section 1 16 is lowered (i.e., proper vertical alignment of intermediate section 1 16 and base section 1 14 may be compromised if guide lines 322, 330 are permitted to slacken while intermediate section 1 16 is lowered). After intermediate section 1 16 has been lowered onto base section 1 14 such that flange 200 of lower end 122 of intermediate section 116 is seated on flange 200 of upper end 120 of base section 1 14 with opposed apertures 204 substantially aligned, guide lines 322, 330 may be detached from connectors 336 and withdrawn from opposed apertures 204. Connectors 336 and winding devices 316, 324 may also be dismounted and used to stack subsequent sections 1 16, 1 18 of tower 102 in a similar manner. In alternative embodiments, winding devices 316, 324 and/or connectors 336 may be mounted at any suitable location inside or outside of base section 1 14 and intermediate section 1 16 using any suitable mounting configuration. Furthermore, while the methods and systems described herein are useful when assembling the tower of a wind turbine, the methods and systems described herein may also be useful when assembling any other suitable component of the wind turbine (e.g., a winding device may be mounted within the hub of the rotor and a free end of a guide line may be connected to a blade of the rotor to facilitate aligning a flange of the blade with a flange of the hub when coupling the blade to the hub while assembling the rotor).

[0029] Fig. 9 is a flow chart of a method 500 for assembling a wind turbine tower. Method 500 includes providing 502 a first tower section and a second tower section, extending 504 a guide line between the first tower section and the second tower section, and hoisting 506 the first tower section above the second tower section. The method further includes vertically aligning 508 the first tower section and the second tower section using the guide line and lowering 510 the first tower section onto the second tower section along the guide line.

[0030] In one embodiment, method 500 may also include lowering the first tower section onto the second tower section such that the first tower section and the second tower section are substantially circumferentially aligned. In another embodiment, method 500 may further include tensioning the guide line to vertically align the first tower section with the second tower section. In some embodiments, method 500 may also include extending a pair of guide lines between the first tower section and the second tower section and vertically aligning the first tower section with the second tower section using the pair of guide lines. Method 500 may further include locating the guide lines on opposite sides of the tower sections. In other embodiments, method 500 may also include providing the first tower section with a first flange defining an aperture, providing the second tower section with a second flange defining an aperture, and extending the guide line through the aperture of the first flange and the aperture of the second flange. In one alternative embodiment, method 500 may also include coupling the guide line to a winding device, fastening a free end of the guide line to one of the first tower section and the second tower section, and tensioning the guide line using the winding device to vertically align the first tower section and the second tower section. In some alternative embodiments, method 500 may also include determining the vertical alignment of the first tower section and the second tower section by gauging an orientation of the guide line using a theodolite instrument. In other alternative embodiments, method 500 may also include determining the vertical alignment of the first tower section and the second tower section by gauging an orientation of the guide line using a pair of theodolite instruments, wherein the pair of theodolite instruments are positioned at an angle of about 90° relative to the guide line.

[0031] In another embodiment, a method for assembling a wind turbine tower may include providing a first tower section having a first upper end and a first lower end, wherein a first annular flange defining a first pair of diametrically opposed apertures is coupled to the first lower end. The method may also include providing a second tower section having a second upper end and a second lower end, wherein a second annular flange defining a second pair of diametrically opposed apertures is coupled to the second upper end. The method may further include extending a first guide line through a first aperture of the first pair of diametrically opposed apertures and through a first aperture of the second pair of diametrically opposed apertures. The method may further include extending a second guide line through a second aperture of the first pair of diametrically opposed apertures and through a second aperture of the second pair of diametrically opposed apertures. The method may also include fastening each of the first guide line and the second guide line to one of the first tower section and the second tower section, hoisting the first tower section above the second tower section, and tensioning at least one of the first guide line and the second guide line to facilitate vertically aligning the first tower section and the second tower section. The method may further include lowering, along the guide lines, the first tower section onto the second tower section such that the first flange is seated on the second flange with the first pair of diametrically opposed apertures substantially aligned with the second pair of diametrically opposed apertures.

[0032] The methods and systems described herein facilitate quickly and precisely aligning stacked sections of a wind turbine tower. The methods and systems described herein further facilitate reducing the need for installation personnel to manually align tower sections as the tower sections are stacked atop one another. As such, the methods and systems described herein facilitate reducing the time and cost associated with assembling a wind turbine tower.

[0033] Exemplary embodiments of methods and systems for assembling a wind turbine tower are described above in detail. The methods and systems described herein are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the methods and systems described herein may have other applications not limited to practice with wind turbines, as described herein. Rather, the methods and systems described herein can be implemented and utilized in connection with various other industries.

[0034] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

WHAT IS CLAIMED IS:

1. A method for assembling a wind turbine tower, said method comprising: providing a first tower section and a second tower section; extending a guide line between the first tower section and the second tower section; hoisting the first tower section above the second tower section; vertically aligning the first tower section and the second tower section using the guide line; and, lowering the first tower section onto the second tower section along the guide line.

2. A method in accordance with claim 1 , further comprising lowering the first tower section onto the second tower section such that an end of the first tower section and an end of the second tower section are substantially circumferentially aligned.

3. A method in accordance with claim 1, further comprising tensioning the guide line to vertically align the first tower section with the second tower section.

4. A method in accordance with claim 1, further comprising: extending a pair of guide lines between the first tower section and the second tower section; and, vertically aligning the first tower section with the second tower section using the pair of guide lines.

5. A method in accordance with claim 4, further comprising locating the guide lines on opposite sides of the tower sections.

6. A method in accordance with claim 1, further comprising: providing the first tower section with a first flange defining an aperture; providing the second tower section with a second flange defining an aperture; and, extending the guide line through the aperture of the first flange and the aperture of the second flange.

7. A method in accordance with claim 1, further comprising: coupling the guide line to a winding device; fastening a free end of the guide line to one of the first tower section and the second tower section; and, tensioning the guide line using the winding device to vertically align the first tower section and the second tower section.

8. A method in accordance with claim 1 , further comprising determining the vertical alignment of the first tower section and the second tower section by gauging an orientation of the guide line using a theodolite instrument.

9. A method in accordance with claim 1, further comprising determining the vertical alignment of the first tower section and the second tower section by gauging an orientation of the guide line using a pair of theodolite instruments, wherein the pair of theodolite instruments are positioned at an angle of about 90° relative to the guide line.

10. A system for assembling a wind turbine tower having a first tower section and a second tower section, said system comprising: a lifting assembly configured to hoist the first tower section above the second tower section; and, at least one alignment assembly comprising a guide line, said alignment assembly configured to vertically align the first tower section and the second tower section using said guide line when said guide line extends between the first tower section and the second tower section, said lifting assembly configured to lower the first tower section onto the second tower section along said guide line.

1 1. A system in accordance with claim 10, wherein said alignment assembly comprises a winding device, said guide line comprising a free end, wherein said alignment assembly is configured to tension said guide line using said winding device when said free end of said guide line is coupled to one of the first tower section and the second tower section to facilitate vertically aligning the first tower section and the second tower section.

12. A system in accordance with claim 1 1 , further comprising a connector configured to be mounted within the one of the first tower section and the second tower section for coupling said free end of said guide line to the one of the first tower section and the second tower section.

13. A system in accordance with claim 10, wherein said alignment assembly comprises: a first alignment assembly comprising a first winding device and a first guide line coupled to said first winding device, said first guide line having a free end, wherein said first alignment assembly is configured to tension said first guide line using said first winding device when said free end of said first guide line is coupled to one of the first tower section and the first tower section; and, a second alignment assembly comprising a second winding device and a second guide line coupled to said second winding device, said second guide line having a free end, wherein said second alignment assembly is configured to tension said second guide line using said second winding device when said free end of said second guide line is coupled to the one of the first tower section and the second tower section.

14. A system in accordance with claim 13, wherein said first alignment assembly and said second alignment assembly are configured to locate said first guide line and said second guide line on opposite sides of the tower sections.

15. A system in accordance with claim 14, further comprising: a first connector configured to be mounted on the one of the first tower section and the second tower section for coupling said free end of said first guide line to the one of the first tower section and the second tower section; and, a second connector configured to be mounted opposite said first connector on the one of the first tower section and the second tower section for coupling said free end of said second guide line to the one of the first tower section and the second tower section.

16. A system in accordance with claim 15, wherein said first connector is configured to be mounted within the one of the first tower section and the second tower section and wherein said second connector configured to be mounted opposite said first connector within the one of the first tower section and the second tower section.

17. A system in accordance with claim 16, wherein said first connector defines a first opening sized to receive said first guide line and wherein said second connector defines a second opening sized to receive said second guide line.

18. A system in accordance with claim 10, further comprising at least one theodolite instrument configured to determine the vertical alignment of the first tower section and the second tower section by gauging an orientation of said guide line.

19. A system in accordance with claim 18, further comprising a pair of theodolite instruments positioned at an angle of about 90° relative to said guide line, said theodolite instruments configured to determine the vertical alignment of the first tower section and the second tower section by gauging an orientation of said guide line.

20. A method for assembling a wind turbine tower, said method comprising: providing a first tower section having a first upper end and a first lower end, wherein a first annular flange defining a first pair of diametrically opposed apertures is coupled to the first lower end; providing a second tower section having a second upper end and a second lower end, wherein a second annular flange defining a second pair of diametrically opposed apertures is coupled to the second upper end; extending a first guide line through a first aperture of the first pair of diametrically opposed apertures and through a first aperture of the second pair of diametrically opposed apertures; extending a second guide line through a second aperture of the first pair of diametrically opposed apertures and through a second aperture of the second pair of diametrically opposed apertures; fastening each of the first guide line and the second guide line to one of the first tower section and the second tower section; hoisting the first tower section above the second tower section; tensioning at least one of the first guide line and the second guide line to facilitate vertically aligning the first tower section and the second tower section; and, lowering, along the guide lines, the first tower section onto the second tower section such that the first flange is seated on the second flange with the first pair of diametrically opposed apertures substantially aligned with the second pair of diametrically opposed apertures.