WO2021177948A1

WO2021177948A1 - Systems and methods for wind turbine blade configurations

Info

Publication number: WO2021177948A1
Application number: PCT/US2020/020806
Authority: WO
Inventors: Ganesh SESHADRI; Vitali Victor Lissianski
Original assignee: General Electric Company
Priority date: 2020-03-03
Filing date: 2020-03-03
Publication date: 2021-09-10

Abstract

A wind turbine includes a tower defining a vertical axis and including a rotatable portion that is rotatable about the vertical axis. A blade is coupled to the rotatable portion at a first span end and includes a second span end opposite the first span end. The blade further includes a leading edge and a trailing edge opposite the leading edge each extending between the first span end and the second span end. The blade defines a chord extending between the leading edge and the trailing edge. A body of the blade extends downward and radially outward from the first span end to the second span end. The body is twisted such that the orientation of the chord relative to the vertical axis varies along the body between the first span end and the second span end and the blade has a conical helix shape.

Description

SYSTEMS AND METHODS FOR WIND TURBINE BLADE CONFIGURATIONS

BACKGROUND

[0001] The field of the disclosure relates to wind turbines, and more particularly to blades for vertical axis wind turbines.

[0002] At least some known wind turbines include a tower having multiple blades. These wind turbines are generally supported by mounting the tower to a foundation. At least some known utility grade wind turbines, i.e., wind turbines designed to provide electrical power to a utility grid, have rotor blades having predetermined shapes and dimensions. The rotor blades transform kinetic wind energy into blade aerodynamic forces that induce a mechanical rotational torque to drive one or more generators, subsequently generating electric power.

[0003] Wind turbines are exposed to large variations in wind inflow, which exert varying loads on the wind turbine structure, particularly the wind turbine tower. For example, some known horizontal axis turbines include blades generally protruding radially outward from a rotor positioned on top of a tower. However, such blade configurations generally result in the wind turbines having a relatively high center of gravity, which can result in a large overturning moment applied to the wind turbines during operation.

[0004] Some known wind turbine systems include relatively large foundations to counteract overturning moments applied to the tower during operation of the wind turbines. However, such foundations are generally expensive and/or difficult to install. Moreover, such foundations generally require stable terrain sufficient to anchor the foundations. As a result, installation of such wind turbines generally requires the construction and support of relatively robust foundations.

[0005] Accordingly, it is desirable to provide a wind turbine that is capable of efficient energy collection without experiencing large overturning moments. BRIEF DESCRIPTION

[0006] In one aspect a wind turbine is provided. The wind turbine includes a tower defining a vertical axis. The tower includes a rotatable portion that is rotatable about the vertical axis. The wind turbine further includes a blade having a first span end coupled to the rotatable portion and a second span end opposite the first span end. A leading edge of the blade extends between the first span end and the second span end and a trailing edge of the blade extends between the first span end and the second span end opposite the leading edge. The blade defines a chord extending between the leading edge and the trailing edge. A body of the blade extends downward and radially outward, relative to the vertical axis, from the first span end to the second span end. The body is twisted betw een the first span end and the second span end such that the orientation of the chord relative to the vertical axis varies along the body between the first span end and the second span end and the blade has a conical helix shape.

[0007] In another aspect, a blade for use in a vertical axis wind turbine is provided. The blade includes a first span end configured to be coupled to a rotatable portion of a tower of the vertical axis wind turbine, and a second span end opposite the first span end. A leading edge of the blade extends between the first span end and the second span end and a trailing edge of the blade extends between the first span end and the second span end opposite the leading edge. The blade defines a chord extending between the leading edge and the trailing edge. A body of the blade extends downward and radially outward, relative to the vertical axis, from the first span end to the second span end when the first span end is coupled to the rotatable portion. The body is twisted between the first span end and the second span end such that the orientation of the chord relative to the vertical axis varies along the body between the first span end and the second span end and the blade has a conical helix shape when the first span end is coupled to the rotatable portion.

[0008] In yet another aspect, a method of assembling a wind turbine is provided. The method includes forming a tower defining a vertical axis, the tower including a rotatable portion that is rotatable about the vertical axis. The method further includes forming a blade including a body extending between a first span end and a second span end. The blade further includes a leading edge and a trailing edge opposite the leading edge each extending between the first span end and the second span end. The blade defines a chord extending between the leading edge and the trailing edge. The method further includes coupling the first span end of the blade to the rotatable portion of the tower such that the body extends downward and radially outward, relative to the vertical axis, from the first span end to the second span end. The body is twisted between the first span end and the second span end such that the orientation of the chord relative to the vertical axis varies along the body between the first span end and the second span end and the blade has a conical helix shape.

DRAWINGS

[0009] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0010] FIG. 1 is a schematic side view of an exemplary wind turbine system;

[0011] FIG. 2 is a schematic side view of an exemplary wind turbine for use in the wind turbine system shown in FIG. 1;

[0012] FIG. 3 is a schematic top view of a first blade for use in the wind turbine shown in FIG. 2;

[0013] FIG. 4 is a schematic sectional view of the first blade of FIG. 3, taken along the line 4-4, shown in FIG. 3;

[0014] FIG. 5 is a schematic top view of the wind turbine shown in FIG.

2;

[0015] FIG. 6 is an enlarged schematic side view of a portion of the wind turbine shown in FIG. 2;

[0016] FIG. 7 is a schematic top view of an alternative first blade for use in the wind turbine shown in FIG. 2; [0017] FIG. 8 is a schematic side view of an alternative wind turbine for use in the wind turbine system shown in FIG. 1; and

[0018] FIG. 9 is a flow chart of an exemplary method of assembling the wind turbine shown in FIG. 2.

[0019] Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of this disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of this disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.

DETAILED DESCRIPTION

[0020] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.

[0021] The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

[0022] As used herein, the term "blade" is intended to be representative of any device that provides reactive force when in motion relative to a surrounding fluid. As used herein, the term "wind turbine" is intended to be representative of any device that generates rotational energy from wind energy, and more specifically, converts kinetic energ of wind into mechanical energy.

[0023] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0024] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

[0025] Embodiments described herein relate to wind turbines and blades for wind turbines. The wind turbine includes a tower defining a vertical axis and including a rotatable portion that is rotatable about the vertical axis. A blade includes a first span end coupled to the rotatable portion and a second span end opposite the first span end. The blade further includes a body extending downward and radially outward, relative to the vertical axis, from the first span end to the second span end. Thus, at least in part due to the radially outward and downward extension of the blade between the first span end and the second span end, the wind turbines and blades described herein have a generally low center of gravity. As a result, the wind turbines and blades described herein reduce the overturning moment applied to the tower during operation of the wind turbines, thereby reducing the size and/or cost of foundations necessary to support the wind turbines.

[0026] FIG. 1 is a schematic perspective view' of an exemplary wind turbine system 100. In the exemplary embodiment, wind turbine system 100 includes a wind turbine 102 coupled to a foundation 104. More specifically, in the exemplary embodiment, wind turbine 100 is a vertical axis wind turbine. Wind turbine 100 includes a tower 106 and a plurality of blades 108, 110 coupled to tow er 106. Tower 106 extends along a vertical axis 112 between a root end 114 coupled to foundation 104 and a tip end 116 opposite root end 114.

[0027] In the exemplary embodiment, blades 108, 110 are each fixedly coupled to a rotatable portion (e.g., a rotor, not shown ) of tower 106 proximate tip end 116 and are configured to drive rotation of the rotatable portion of tower 106 about vertical axis 112. More specifically, in the exemplary embodiment, wind turbine 102 includes a first blade 108 and a second blade 110. In alternative embodiments, wind turbine 102 has any number of blades 108, 110 that enables wind turbine 102 to function as described herein. In the exemplary embodiment, tower 106 is fabricated from tubular steel and has a cavity (not shown in FIG. 1) extending between root end 114 and tip end 116. In alternative embodiments, wind turbine 100 includes any tower 106 that enables wind turbine 100 to operate as described herein.

[0028] In the exemplary embodiment, blades 108, 110 are positioned about tower 106 to facilitate rotating the rotatable portion (not shown) of tower 106 when wind flows through wind turbine 100. As the rotatable portion (not shown) of tower 106 rotates, kinetic energy from the wind is transferred into usable mechanical energy, and subsequently, electrical energy. More specifically, in the exemplary embodiment, blades 108, 110 are configured to generate lift and drag when wind acts upon blades 108, 110. The generated lift and drag produce a net torque through the rotation of the rotatable portion (not shown) of tower 106. The produced torque may be transferred to an electrical generator to derive electrical energy from rotation of the rotatable portion (not shown) of tower 106.

[0029] In the exemplary embodiment, wind turbine 102 is an offshore wind turbine. More specifically, in the exemplary embodiment, foundation 104 is buoyant and is configured to be held in place by a plurality of anchoring cables 118 extending from foundation 104 to a sea bed surface 120. In alternative embodiments, foundation 104 is maintained in place in any manner that enables wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, foundation 104 includes an anchoring frame (not shown) extending between tower 106 and sea bed surface 120. In further alternative embodiments, wind turbine 102 is a land based wind turbine.

[0030] FIG. 2 is a schematic side view of an exemplary wind turbine 102 for use in wind turbine system 100 (show n in FIG. 1). In the exemplary embodiment, first blade 108 and second blade 110 are substantially identical. Blades 108, 110 each extend generally vertically between a first span end 122 and a second span end 124. First span ends 122 are each coupled to tower 106 proximate tip end 116 of tower 106. More specifically, in the exemplary embodiment, first span end 122 of first blade 108 is positioned circumferentially opposite first span end 122 of second blade 110. In the exemplary embodiment, first blade 108 and second blade 110 are positioned to extend generally symmetrically about tower 106. In alternative embodiments, first blade 108 and second blade 110 are coupled to tower 106 in any manner that enables wind turbine 102 to function as described herein. In the exemplary embodiment, blades 108, 110 each extend, at least partially, downwards relative to vertical axis 112 such that second span ends 124 of first blade 108 and second blade 110 are each positioned in substantial horizontal alignment with root end 114 of tower 106. In alternative embodiments, blades 108, 110 extend any vertical distance that enables wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, second span ends 124 of blades 108, 110 are each positioned vertically above root end 114 of tower 106.

[0031] In the exemplary embodiment, blades 108, 110 are each shaped as a conical helix. More specifically, and as described in greater detail below with respect to FIGS. 5 and 6, in the exemplary embodiment, blades 108, 110 are each curved relative to the vertical axis 112 and are twisted between first span end 122 and second span end 124. In alternative embodiments, blades 108, 110 are shaped in any manner that enables wind turbine 102 to function as described herein. In the exemplary embodiment, second span ends 124 of first blade 108 and second blade 110 are each located a radial distance, Ri from tower 106. More specifically, in the exemplary embodiment, at least in part due to the spiral curvature of first blade 108 and second blade 110, the radial distance Ri of blades 108, 110 from tower 106 increases along the extension of blades 108, 110 between first span end 122 and second span end 124. In other words, in the exemplary embodiment, the radial distance Ri between blades 108, 110 and tower 106 is greatest at second span ends 124 of blades 108, 110. In the exemplary embodiment, the radial distance Ri increases substantially constantly between first span end 122 and second span end 124. In alternative embodiments, as shown in FIG. 6, for example, the radial distance Ri is constant along at least of a portion of blades 108, 110 between first span end 122 and second span end 124.

[0032] In the exemplary embodiment, tower 106 extends a height Hi between root end 114 and tip end 116. More specifically, in the exemplary embodiment, height Hi of tower 106 is approximately twice the maximum radial extension Ri of first blade 108 and second blade 110. Moreover, as described above, first blade 108 and second blade 110 each extend the height Hi of tower 106. In other words, in the exemplary embodiment, first blade 108 and second blade 110 are each sized to extend a vertical height Hi between first span ends 122 and second span ends 124 that is approximately twice the radial extension Ri of first blade 108 and second blade 110. In alternative embodiments, blades 108, 110 are sized to extend any height that enables blades 108, 110 to function as described herein.

[0033] In the exemplary embodiment, wind turbine 102 includes arms 126 fixedly coupled to tower 106 and extending, at least in part, radially therefrom to blades 108, 110. In the exemplary embodiment, arms 126 include rigid bodies each configured to provide mechanical support for blades 108, 110 during operation of wind turbine 102. More specifically, in the exemplary embodiment, arms 126 are fixedly coupled to a portion of blades 108, 110 proximate second ends 124 to prevent outward deflection of second ends 124 caused by wind forces and/or other forces acting on blades 108, 110 during operation. In alternative embodiments, arms 126 are coupled to any portion of blades 108, 110 that enables wind turbine 102 to function as described herein. In further alternative embodiments, arms 126 have any configuration that enable wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, arms 126 include cables (not shown) extending between blades 108, 110 and tower 106. In the exemplary embodiment, wind turbine 102 includes two arms 126 each corresponding to one of first blade 108 and second blade 110. In alternative embodiments, wind turbine 102 includes any number of arms 126 that enables wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, wind turbine 102 includes a plurality of arms 126 coupled to each blade 108, 110 of wind turbine 102.

[0034] In the exemplary embodiment, arms 126 are coupled to tower 106 approximately midway between root end 114 and tip end 116 of tower 106. Arms each 126 extend obliquely and downwards from tower 106 at a first angle qi between 15 degrees and 75 degrees. More specifically, in the exemplary embodiment, arms 126 extend obliquely and downwards from tower 106 such that first angle qi is approximately 45 degrees. In alternative embodiments, arms 126 extend from tower 106 in any manner that enables wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, arms 126 extend upwards from tower 106 to blades 108, 110. [0035] In the exemplary embodiment, arms 126 are aerodynamically shaped to facilitate rotation of arms 126 with blades 108, 110 and reduction of energy losses during operation of wind turbine 102. More specifically, in the exemplary embodiment, arms 126 are each shaped as an airfoil and extend between a leading edge 128 and a trailing edge 130. In alternative embodiments, arms 126 are shaped in any manner that enables wind turbine 102 to function as described herein.

[0036] FIG. 3 is a top view of first blade 108, shown in FIG. 2. FIG. 4 is a sectional view of first blade 108 taken along the line 4-4, shown in FIG. 3. As illustrated in FIG. 3, first blade 108 is shown elongated (i.e., not curved) for clarity. In the exemplary embodiment, first blade 108 includes a body 132 extending between first span end 122 and second span end 124. First blade includes a leading edge 134 and a trailing edge 136 opposite leading edge 134. Leading edge 134 and trailing edge 136 each extend between first span end 122 and second span end 124. Referring to FIG. 4, in the exemplary embodiment, body 132 has an airfoil cross section and extends along a chord line 138 between leading edge 134 and trailing edge 136. In alternative embodiments, first blade 108 has any shape that enables first blade 108 to function as described herein.

[0037] Referring back to FIG. 3, in the exemplary embodiment, body 132 of first blade 108 is tapered between first span end 122 and second span end 124 such that leading edge 134 and trailing edge 136 generally diverge as they approach second span end 124 from first span end 122. In other words, in the exemplary embodiment, the length of chord 138 of first blade 108 increases between first span end 122 and second span end 124. More specifically, in the exemplar}' embodiment, a first chord distance Ci at first span end 122 is approximately half of a second chord distance C2 at second span end 124. In alternative embodiments, first span end 122 and second span end 124 are sized to have any sized chord distances Ci, C2 that enable first blade 108 to function as described herein. For example, and without limitation, in some alternative embodiments, first blade 108 is not tapered and first chord line Ci at first span end 122 is approximately equal to second chord line C2 at second span end 124.

[0038] FIG. 5 is a top view of wind turbine 102 shown in FIG. 2. In the exemplary embodiment, bodies 132 of first blade 108 and second blade 110 are each curved relative to the vertical axis 112 (shown in FIG. 2). In particular, in the exemplary embodiment, bodies 132 each spiral radially outward from the vertical axis 112 (shown in FIG. 2). In other words, bodies 132 each spiral radially outwards from tower 106. In the exemplary embodiment, blades 108, 110 each extend through approximately a 180 degree arc between first span end 122 and second span end 124. In alternative embodiments, blades 108, 110 are curved relative to the vertical axis 112 (shown in FIG. 2) in any manner that enables wind turbine 102 to function as described herein. For example, and without limitation, in some embodiments, blades 108, 110 are curved in approximately a 90 degree arc between first span end 122 and second span end 124.

[0039] FIG. 6 is an enlarged, side view of a portion of wind turbine 102 shown in FIG. 2. A coordinate system 140 includes an X-axis, a Y-axis, and a Z axis.

[0040] In the exemplary embodiment, first blade 108 is twisted between first span end 122 and second span end 124 such that the orientation of a first chord 142 of first blade 108 relative to the vertical axis 112 varies along body 132 between first span end 122 and second span end 124. More specifically, in the exemplary embodiment, first blade 108 is twisted between first span end 122 and second span end 124 such that first chord line 142 at first span end 122 and a second chord line (not shown) at second span end 124 are both generally oriented perpendicular to the vertical axis 112. In particular, in the exemplary embodiment, first chord line 142 extends in a direction substantially parallel to the X-axis and second chord line (not shown) extends in a direction substantially parallel to the Y-axis (i.e., into the page). In alternative embodiments, first blade 108 is shaped in any manner that enables wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, first blade 108 is not twisted between first span end 122 and second span end 124 and first chord line 142 is oriented generally parallel to second chord line (not shown).

[0041] In the exemplary embodiment, first blade 108 is generally continuously twisted along body 132 between first span end 122 and second span end 124. For example, in the exemplary embodiment a third chord line 144 is located generally midway between first span end 122 and second span end 124. In the exemplary embodiment, third chord line 144 is oriented relative to the Z-axis (i.e., relative to the vertical axis 112) at a second oblique angle Q2. More specifically, in the exemplary embodiment, second oblique angle Q2 is approximately 45 degrees. In alternative embodiments, first blade 108 is shaped in any manner that enables wind turbine 102 to function as described herein. For example, and without limitation, in some alternative embodiments, first blade 108 is twisted only along a portion of the length of first blade 108 between first span end 122 and second span end 124.

[0042] FIG. 7 is a schematic top view of an alternative first blade 208 for use in wind turbine 100 shown in FIG. 2. In the exemplary embodiment, first blade 208 is substantially the same as first blade 108, described above with respect to FIGS. 2-6, except as described below. As illustrated in FIG 7, first blade 208 is shown elongated (i.e., not curved) for clarity. In the exemplar}' embodiment, first blade 208 is configured to be curved and twisted in substantially the same manner as first blade 108 (shown in FIG. 5).

[0043] In the exemplary embodiment, first blade 208 includes a body 232 extending between a first span end 222 and a second span end 224. First blade 208 includes a leading edge 234 and a trailing edge 236 opposite leading edge 234. Leading edge 234 and trailing edge 236 each extend between first span end 222 and second span end 224. In the exemplary embodiment, body 232 has an airfoil cross section and extends along a chord line 238 between leading edge 234 and trailing edge 236. In alternative embodiments, first blade 208 has any shape that enables first blade 208 to function as described herein.

[0044] In the exemplary embodiment, body 232 of first blade 208 includes a midsection 244 approximately midway between first span end 222 and second span end 224. Body 232 is tapered between first span end 222, second span end 224, and midsection 244. More specifically, in the exemplary embodiment, body 232 tapers inward towards midsection 244 such that leading edge 234 and trailing edge 236 are arranged to generally converge (i.e., extend inwardly of body 232) as body 232 extends from first span end 222 to midsection 244. Further, leading edge 234 and trailing edge 236 are arranged to generally diverge (i.e., extend outwardly of body 232) from one another as body 232 extends from midsection 244 to second span end 224. In other words, in the exemplary embodiment, the length of chord 238 of first blade 208 decreases as body 232 extends from first span end 222 to midsection 244 and the length of chord 238 increases as body 232 extends from midsection 244 to second span end 224. In alternative embodiments, body 232 is tapered to any point along blade 208 between first span end 222 and second span end 224 that enables blade 208 to function as described herein. For example, and without limitation, in some alternative embodiments, body 232 is tapered inward toward a portion of blade 208 located approximately midway between midsection 244 and at least one of first span end 222 and second span end 224.

[0045] In the exemplary embodiment, blade 208 is sized such that a first chord distance C₃ at first span end 222 is approximately equal to a second chord distance C₄ at second span end 224. A third chord distance C, at midsection 244 is approximately three-quarters of the first chord distance C3 and second chord distance C4. In alternative embodiments, third chord distance C₅ at midsection 244 is sized in any manner relative to first chord distance C3 and second chord distance C4 that enables first blade to operate as described herein. For example, and without limitation, in some alternative embodiments, third chord distance C₅ at midsection 244 is between 50% and 90% of at least one of first chord distance C₃ and second chord distance C₄. In further alternative embodiments, blade 208 is tapered in any manner that enables first blade 208 to function as described herein.

[0046] FIG. 8 is a schematic side view of an alternative wind turbine 302 for use in wind turbine system 100 shown in FIG. 1. In the exemplary embodiment, wind turbine 302 is substantially the same as wind turbine 102, described above with respect to FIG. 2, except as described below.

[0047] In the exemplary embodiment, wind turbine 302 includes a first blade 308 and a second blade 310 each sized to be substantially identical. Blades 308, 310 each extend generally vertically between a first span end 322 and a second span end 324. First span ends 322 are each coupled to a tower 306 proximate a tip end 316 of tower 306. More specifically, in the exemplary embodiment, first span end 322 of first blade 308 is positioned at circumferentially opposite first span end 322 of second blade 310. In the exemplary embodiment, first blade 308 and second blade 310 are positioned to extend generally symmetrically about tower 306. In alternative embodiments, first blade 308 and second blade 310 are coupled to tower 306 in any manner that enables wind turbine 302 to function as described herein. In the exemplary embodiment, blades 308, 310 each extend, at least partially, downwards relative to a vertical axis 312 of wind turbine 302, such that second span ends 324 of first blade 308 and second blade 310 are each positioned in substantial horizontal alignment with root end 314 of tower 306. In alternative embodiments, blades 308, 310 extend any vertical distance that enables wind turbine 302 to function as described herein. For example, and without limitation, in some alternative embodiments, second span ends 324 of blades 308, 310 are each positioned vertically above root end 314 of tower 306.

[0048] In the exemplar embodiment, blades 308, 310 each include a tail section 350. In the exemplary embodiment, tail sections 350 extend substantially parallel to the vertical axis 312 to second span ends 324. Further, tail sections have a length that is approximately one quarter of the total span of blades 308, 310. In alternative embodiments, tail sections 350 have any configuration that enables blades 308, 310 to function as described herein.

[0049] In the exemplary embodiment, blades 308, 310 each include first sections 352 extending between first span ends 322 and tail sections 350. First sections 352 of blades 308, 310 are each curved and twisted in substantially the same manner as described above with respect to blades 108, 110 (shown in FIG. 2). In the exemplary embodiment, at least in part due to the spiral curvature of first sections 352 of first blade 308 and second blade 310, the radial distance of blades 308, 310 from tower 306 increases along the span of blades 308, 310 between first span end 322 and tail sections 350. In the exemplary embodiment, tail sections 350 are each located a constant radial distance, Ri from tower 306 along the span of tail sections 350. In other words, in the exemplary embodiment, the radial distance Ri between blades 308, 310 and tower 306 is greatest along tail sections 350.

[0050] In the exemplary embodiment, tail sections 350 of blades 308, 310 extend generally vertically from second span ends 324. In particular, in the exemplary embodiment the orientation of respective chords (similar to chord 138 shown in FIG. 4) of tail sections 350 relative to the vertical axis 112 remains constant along the span of tail sections 350. In other words, in the exemplary embodiment, tail sections 350 are not twisted along the span of tail sections 350. More specifically, in the exemplary embodiment, a chord line (not shown) of tail section 350 is oriented in a circumferential direction (i.e., into the page) relative to the vertical axis 112, along the entire span of tail section 350. In alternative embodiments, blades 308, 310 are shaped in any manner that enables wind turbine 302 to function as described herein. [0051] FIG. 9 is a flow diagram of an exemplary method 400 of assembling a wind turbine (e.g., wind turbine 102 shown in FIG. 1). Method 400 includes forming 402 a tower (e.g., tower 106 shown in FIG. 2) defining a vertical axis, the tower including a rotatable portion that is rotatable about the vertical axis. Method 400 further includes forming 404 a blade (e.g., first blade 108 shown in FIG. 2) including a body (e.g., body 132 shown in FIG. 1) extending between a first span end (e.g., first span end 122 shown in FIG. 2) and a second span end (e.g., second span end 124 shown in FIG. 2). The blade further includes a leading edge (e.g., leading edge 134 shown in FIG. 4) and a trailing edge (e.g., trailing edge 136 shown in FIG. 4) opposite the leading edge each extending between the first span end and the second span end. The blade defines a chord (e.g., chord 138 shown in FIG. 4) extending between the leading edge and the trailing edge. Method 400 also includes coupling 404 the first span end of the blade to the rotatable portion of the tower such that the body extends downward and radially outward, relative to the vertical axis, from the first span end to the second span end. The body is twisted between the first span end and the second span end such that the orientation of the chord relative to the vertical axis varies along the body between the first span end and the second span end and the blade has a conical helix shape.

[0052] An exemplary technical effect of the methods, systems, and apparatus described herein includes at least one of: (a) reduced construction materials and labor costs for installing wind turbines; (b) improved lifespan of wind turbines; (c) reduced maintenance and servicing for wind turbines; and (d) improved energy collection of wind turbines.

[0053] Exemplary embodiments of wind turbines, blades for use in wind turbine, and methods for assembling wind turbines are described above in detail. The methods and systems are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the method may also be used in combination with other turbine components, and are not limited to practice only with the wind turbine as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other wind turbine applications. [0054] Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

[0055] This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure 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 wind turbine comprising: a tower defining a vertical axis, said tower comprising a rotatable portion that is rotatable about the vertical axis; and a blade comprising: a first span end coupled to said rotatable portion; a second span end opposite said first span end; a leading edge extending between said first span end and said second span end; a trailing edge extending between said first span end and said second span end opposite said leading edge, said blade defining a chord extending between said leading edge and said trailing edge; and a body extending downward and radially outward, relative to the vertical axis, from said first span end to said second span end, wherein said body is twisted between said first span end and said second span end such that the orientation of the chord relative to the vertical axis varies along said body between said first span end and said second span end, and wherein said blade has a conical helix shape.

2. The wind turbine in accordance with Claim 1, wherein said body tapers between said first span end and said second span end.

3. The wind turbine in accordance with Claim 2, wherein a chord length of said blade at said second span end is greater than a chord length of said blade at said first span end.

4. The wind turbine in accordance with Claim 2, wherein said body further comprises a midsection located between said first span end and said second span end, and wherein a chord length of said blade at said first span end and said second span end is greater than a chord length of said blade at said midsection.

5. The wind turbine in accordance with Claim 1 further comprising an arm coupled to said tower and extending radially outward from said tower to said body, wherein said arm has an airfoil cross section.

6. The wind turbine in accordance with Claim 1, wherein said body is curved relative to the vertical axis along a first arc.

7. The wind turbine in accordance with Claim 6, wherein the first arc spans at least 180 degrees between said first span end and said second span end.

8. The wind turbine in accordance with Claim 1 further comprising an additional blade comprising: a third span end coupled to said rotatable portion of said tower; a fourth span end opposite said third span end; and an additional body extending downward and radially outward, relative to the vertical axis, from said third span end to said fourth span end.

9. The wind turbine in accordance with Claim 8, wherein said third span end is coupled to said rotatable portion circumferentially opposite said first span end.

10. The wind turbine in accordance with Claim 8, wherein said blade and said additional blade extend substantially symmetrically about said tower.

11. The wind turbine in accordance with Claim 1 , wherein said blade has an airfoil cross section, and wherein said second span end is a free end.

12. A blade for use in a vertical axis wind turbine, said blade comprising: a first span end configured to be coupled to a rotatable portion of a tower of said vertical axis wind turbine, the tower defining a vertical axis; a second span end opposite said first span end; a leading edge extending between said first span end and said second span end; a trailing edge extending between said first span end and said second span end opposite said leading edge, said blade defining a chord extending between said leading edge and said trailing edge; and a body configured to extend downward and radially outward, relative to the vertical axis, from said first span end to said second span end when said first span end is coupled to the rotatable portion, wherein said body is twisted between said first span end and said second span end such that the orientation of the chord relative to the vertical axis varies along said body between said first span end and said second span end, and wherein said blade has a conical helix shape when said first span end is coupled to the rotatable portion of the tower.

13. The blade in accordance with Claim 12, wherein said body tapers between said first span end and said second span end.

14. The blade in accordance with Claim 13, wherein a chord length of said blade at said second span end is greater than a chord length of said blade at said first span end.

15. The blade in accordance with Claim 13, wherein said body further comprises a midsection located between said first span end and said second span end, and wherein a chord length of said blade at said first span end and said second span end is greater than a chord length of said blade at said midsection.

16. The blade in accordance with Claim 12, wherein said blade has an airfoil cross section, and wherein said second span end is a free end when said first span end is coupled to the rotatable portion of the tower.

17. A method of assembling a wind turbine comprising: forming a tower defining a vertical axis, the tower including a rotatable portion that is rotatable about the vertical axis; forming a blade including a body extending between a first span end and a second span end, the blade further including a leading edge and a trailing edge opposite the leading edge each extending between the first span end and the second span end, the blade defining a chord extending between the leading edge and the trailing edge; and coupling the first span end of the blade to the rotatable portion of the tower such that the body extends downward and radially outward, relative to the vertical axis, from the first span end to the second span end, wherein the body is twisted between the first span end and the second span end such that the orientation of the chord relative to the vertical axis varies along the body between the first span end and the second span end and, and wherein the blade has a conical helix shape.

18. The method in accordance with Claim 17, wherein the body tapers between the first span end and the second span end.

19. The method in accordance with Claim 18, wherein a chord length of the blade at the second span end is greater than a chord length of the blade at the first span end.

20. The method in accordance with Claim 18, wherein the body further includes a midsection located between the first span end and the second span end, and wherein a chord length of the blade at the first span end and said second span end is greater than a chord length of the blade at the midsection.