SYSTEMS AND METHODS FOR PITCHING OF
ROTOR BLADES
BACKGROUND
[0001] The field of the disclosure relates to wind turbines, and more
particularly to systems for pitching rotor blades of wind turbines.
[0002] At least some known wind turbines include a rotor having
5 multiple blades. The rotor is sometimes coupled to a housing, or nacelle, that is
positioned on top of a base, for example, a tubular tower. 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
10 rotational torque to drive one or more generators, subsequently generating electric
power.
[0003] Wind turbines are exposed to large variations in wind inflow,
which exerts varying loads to the wind turbine structure, particularly the wind turbine
rotor and shaft. Some known wind turbines include pitch mechanisms designed to
15 pitch the rotor blades relative to the housing based on a variety of factors such as wind
speed and the rotational speed of the rotor. Pitching a rotor blade refers to rotating the
blade to change the angle of attack of the wind on the blade. In at least some wind
turbine systems, pitching the rotor blades to a desired angle of attack can induce stress
and fatigue on components of the wind turbine system, such as, for example, pitch
20 bearings located at the root of the blades. In addition, at least some rotor blades are
generally formed as a single piece blade. As a result, shipping of such rotor blades
generally requires that the rotor blades are transported in a container capable of
containing the entire length of the rotor blade.
3
[0004] Accordingly, it is desirable to provide a wind turbine system
that reduces the stress and fatigue on components of the wind turbine system during
operation. In addition, it is desirable to provide a rotor blade that allows for more
compact, and thereby less costly, transportation of the rotor blade.
5 BRIEF DESCRIPTION
[0005] In one aspect, a wind turbine is provided. The wind turbine
includes a hub rotatable about an axis and a blade coupled to the hub. The blade
includes an inner blade portion having a first end and a second end. The inner blade
portion is coupled to the hub at the first end and extends radially outward from the hub
10 to the second end. The blade further includes an outer blade portion having a first end
and a second end. The first end of the outer blade portion is pivotably coupled to the
second end of the inner blade portion.
[0006] In another aspect, a blade for use in a wind turbine system is
provided. The blade includes an inner blade portion, an outer blade portion, and a
15 rotatable element. The inner blade portion has a first end and a second end. The outer
blade portion includes a first end and a second end. The first end of the outer blade
portion is coupled to the second end of the inner blade portion. The rotatable element
extends between the inner blade portion and the outer blade portion. The rotatable
element includes a first end coupled to the inner blade portion and a second end coupled
20 to the outer blade portion. The rotatable element second end is rotatable relative to the
rotatable element first end to facilitate rotating the outer blade portion relative to the
inner blade portion.
[0007] In yet another aspect, a method of assembling a blade for use in
a wind turbine system is provided. The blade includes an inner blade portion having a
25 first and second end. The blade also includes an outer blade portion having a first and
second end. The method includes coupling the first end of the outer blade portion to
the second end of the inner blade portion. The method also includes providing a
4
rotatable element having a first and second end, the second end of the rotatable element
being rotatable relative to the first end of the rotatable element. The method further
includes coupling the first end of the rotatable element to the inner blade portion. The
method also includes coupling the second end of the rotatable element to the outer
5 blade portion such that the outer blade portion is rotatable relative to the inner blade
portion.
DRAWINGS
[0008] These and other features, aspects, and advantages of the
present disclosure will become better understood when the following detailed
10 description is read with reference to the accompanying drawings in which like
characters represent like parts throughout the drawings, wherein:
[0009] FIG. 1 is a perspective view of an exemplary wind turbine;
[0010] FIG. 2 is a schematic sectional view of an exemplary rotor
blade for use in the wind turbine shown in FIG. 1;
15 [0011] FIG. 3 is an enlarged schematic sectional view of an
alternative rotor blade for use in the wind turbine shown in FIG. 1;
[0012] FIG. 4 is a schematic end view of a portion of the alternative
rotor blade shown in FIG. 3;
[0013] FIG. 5 is a schematic sectional view of a further alternative
20 rotor blade for use in the wind turbine shown in FIG. 1;
[0014] FIG. 6 is a schematic sectional view of a yet further alternative
rotor blade for use in the wind turbine shown in FIG. 1; and
5
[0015] FIG. 7 is a flow chart of an exemplary method of assembling
a rotor blade for use in the wind turbine shown in FIG. 1.
[0016] Unless otherwise indicated, the drawings provided herein are
meant to illustrate features of embodiments of this disclosure. These features are
5 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
10 [0017] 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.
[0018] The singular forms “a”, “an”, and “the” include plural
references unless the context clearly dictates otherwise.
[0019] As used herein, the term "blade" is intended to be
15 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 energy of wind into mechanical energy.
[0020] “Optional” or “optionally” means that the subsequently
20 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.
[0021] 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
25 is related. Accordingly, a value modified by a term or terms, such as “about”,
6
“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
5 ranges are identified and include all the sub-ranges contained therein unless context or
language indicates otherwise.
[0022] Embodiments described herein relate to wind turbines and
rotor blades for wind turbines. The wind turbine includes a hub rotatable about an axis
and a rotor blade coupled to the hub. The rotor blade includes an inner blade portion
10 having a first end and a second end. The inner blade portion is coupled to the hub at
the first end and extends radially outward from the hub to the second end. The rotor
blade further includes an outer blade portion having a first end and a second end. The
first end of the outer blade portion is pivotably coupled to the second end of the inner
blade portion. Thus, the wind turbines and rotor blades for wind turbines described
15 herein facilitate pitching the outer blade portion of the rotor blade relative to the inner
blade portion of the rotor blade. As a result, the wind turbines and rotor blades
described herein reduce the load on pitch bearings located in the rotor blade root during
pitching of the outer blade portion, thereby increasing the life span of the pitch bearings
located in the root and reducing servicing costs for the wind turbines and rotor blades.
20 In addition, the inner blade portion and outer blade portion of the rotor blades described
herein may be disassembled for transportation, allowing for more compact shipping of
rotor blades and thereby reducing the costs associated with transporting rotor blades.
[0023] FIG. 1 is a schematic perspective view of an exemplary wind
turbine 100. In the exemplary embodiment, wind turbine 100 is a horizontal axis wind
25 turbine. Wind turbine 100 includes a tower 102 extending from a supporting surface
(not shown), a nacelle 106 coupled to tower 102, and a rotor 108 coupled to nacelle
106. Rotor 108 has a rotatable hub 110 and a plurality of rotor blades 112 coupled to
7
rotatable hub 110. In the exemplary embodiment, rotor 108 has three rotor blades 112.
In alternative embodiments, rotor 108 has any number of rotor blades 112 that enables
wind turbine 100 to function as described herein. In the exemplary embodiment, tower
102 is fabricated from tubular steel and has a cavity (not shown in FIG. 1) extending
5 between the supporting surface and nacelle 106. In alternative embodiments, wind
turbine 100 includes any tower 102 that enables wind turbine 100 to operate as
described herein. For example, in some embodiments, tower 102 is any one of a lattice
steel tower, guyed tower, concrete tower and hybrid tower.
[0024] In the exemplary embodiment, blades 112 are positioned about
10 rotatable hub 110 to facilitate rotating rotor 108 when wind flows through wind turbine
100. When rotor 108 rotates, kinetic energy from the wind is transferred into usable
mechanical energy, and subsequently, electrical energy. During operation, rotor 108
rotates about a horizontal axis 116 that is substantially parallel to the supporting
surface. In addition, in some embodiments, rotor 108 and nacelle 106 are rotated about
15 tower 102 on a yaw axis 118 to control the orientation of blades 112 with respect to the
direction of wind. In alternative embodiments, wind turbine 100 includes any rotor
108 that enables wind turbine 100 to operate as described herein.
[0025] FIG. 2 is a schematic sectional view of an exemplary rotor
blade 112 for use in wind turbine 100 (shown in FIG. 1). In the exemplary embodiment,
20 rotor blade 112 is configured to be coupled to rotatable hub 110 (shown in FIG. 1) at a
hub end 120 and extend radially outward from rotatable hub 110 to a distal end 122.
Rotor blade 112 defines a longitudinal axis 124 extending between hub end 120 and
distal end 122 of rotor blade 112. In the exemplary embodiment, hub end 120 includes
a hub pitching mechanism 126 for coupling rotor blade 112 to rotatable hub 110 (shown
25 in FIG. 1). Hub pitching mechanism 126 facilitates rotating rotor blade 112 about
longitudinal axis 124 (i.e., pitching rotatable blade 112) relative to rotatable hub 110
when rotor blade 112 is coupled to rotatable hub (shown in FIG. 1). In the exemplary
8
embodiment, hub pitching mechanism 126 includes a hub actuation mechanism, such
as, for example and without limitation, a hub bearing (not shown) and a gear and pinion
actuation mechanism. In alternative embodiments, rotor blade 112 includes any means
for connecting rotor blade 112 to rotatable hub 110 that enables wind turbine 100
5 (shown in FIG. 1) to function as described herein. For example, and without limitation,
in some alternative embodiments, rotor blade 112 does not include a hub pitching
mechanism 126.
[0026] Rotor blade 112 includes an inner blade portion 128 and an
outer blade portion 130. In the exemplary embodiment, inner blade portion 128 and
10 outer blade portion 130 are independently formed from one another. When coupled
together, inner blade portion 128 and outer blade portion 130 collectively define a
length, indicated generally at L1, of rotor blade 112 from hub end 120 to distal end 122.
In particular, in the exemplary embodiment, inner blade portion 128 includes an inner
blade body 132 extending longitudinally from hub end 120, or more broadly, a first end
15 of inner blade portion 128 to a connection end 134, or more broadly, a second end of
inner blade portion 128. Outer blade portion 130 includes an outer blade body 136
extending longitudinally from a pivot end 138, or more broadly, a first end of outer
blade portion, to distal end 122, or more broadly, a second end of outer blade portion
130. In alternative embodiments, outer blade portion 130 extends, at least in part,
20 obliquely relative to inner blade portion 128. For example, and without limitation, in
at least some alternative embodiments, outer blade portion 130 is coupled to inner blade
portion 128 in a tilted sail-like configuration. In further alternative embodiments, outer
blade portion 130 includes a folded tip (not shown) extending obliquely relative to the
longitudinal axis 123. In yet further alternative embodiment, outer blade portion 130
25 is oriented relative to inner blade portion 128 in any manner that enables rotor blade
112 to function as described herein.
9
[0027] In the exemplary embodiment, inner blade portion 128 and
outer blade portion 130 are generally hollowed within inner blade body 132 and outer
blade body 136 respectively. In alternative embodiments, inner blade body 132 and
outer blade body 136 each include a plurality of blade support structures (not shown)
5 such as, for example and without limitation, sparcap and sparweb supports. In such
embodiments, the blade support structures extend within and support inner blade body
132 and outer blade body 136 respectively. In further alternative embodiments, inner
blade body 132 and outer blade body 136 include an internal filler material (e.g., a
polyurethane foam) located within at least one of inner blade body 132 and outer blade
10 body 136. In yet further alternative embodiments, at least one of inner blade portion
128 and outer blade portion 130 is non-hollow. In yet further alternative embodiments,
inner blade portion 128 and outer blade portion 130 include any internal structure that
enables rotor blade 112 to function as described herein.
[0028] In the exemplary embodiment, inner blade portion 128 defines
15 a length, indicated generally at L2, between hub end 120 and connection end 134. Outer
blade portion 130 defines a length, indicated generally at L3, between pivot end 138
and distal end 122. In the exemplary embodiment, the length L2 of inner blade portion
128 is greater than the length L3 of outer blade portion 130. More specifically, in the
exemplary embodiment, the length L1 of rotor blade 112 is approximately 65 meters,
20 the length L2 of inner blade portion 128 is approximately 40 meters, and the length L3
of outer blade portion 130 is approximately 25 meters. In alternative embodiments,
inner blade portion 128 and outer blade portion 130 have any lengths L2, L3 that enable
rotor blade 112 to function as described herein. In the exemplary embodiment, inner
blade portion 128 and outer blade portion 130 lengths L2, L3 collectively define the
25 length L1 of rotor blade 112. In alternative embodiments, rotor blade 112 includes at
least one or more additional blade portions (not shown) extending along the length L1
of rotor blade 112 in addition to inner blade portion 128 and outer blade portion 130.
10
[0029] In the exemplary embodiment, outer blade portion 130 is
pivotably coupled to inner blade portion 128. In other words, in the exemplary
embodiment, outer blade portion 130 is coupled to inner blade portion 128 such that
outer blade portion 130 is rotatable with respect to inner blade portion 128. In
5 particular, outer blade portion 130 is configured for bi-directional (e.g., clockwise and
counter clockwise) rotation relative to inner blade portion 128. In alternative
embodiments outer blade portion 130 is configured for multidirectional (e.g., tilt and
yaw) pivoting relative to inner blade portion 128. In the exemplary embodiment, outer
blade portion 130 is configured to rotate between +/- one degree and +/- three degrees
10 about longitudinal axis 124 relative to inner blade portion 128 during operation of wind
turbine 100 (shown in FIG. 1). In alternative embodiments, outer blade portion 130 is
configured to rotate at least +/- five degrees about longitudinal axis 124 relative to inner
blade portion 128. In alternative embodiments, outer blade portion 130 is configured
to rotate any angle about longitudinal axis 124 relative to inner blade portion 128 that
15 enables rotor blade 112 to function as described herein.
[0030] In the exemplary embodiment, pivotably coupling outer blade
portion 130 to inner blade portion 128 facilitates rotating (i.e., pitching) of outer blade
portion 130 about longitudinal axis 124 while inner blade portion 128 is maintained in
position (i.e., not rotated) with respect to longitudinal axis 124. Pivotably coupling
20 outer blade portion 130 to inner blade portion 128 further facilitates rotating outer blade
portion 130 relative to inner blade portion 128 while inner blade portion 128 and outer
blade portion 130 are each rotated about longitudinal axis 124 by hub pitching
mechanism 126. In other words, in the exemplary embodiment, hub pitching
mechanism 126 is configured to rotate entire rotor blade 112 (i.e., rotate inner blade
25 portion 128 and outer portion 130 in synchronous rotation with one another) about
longitudinal axis 124 and outer blade portion 130 is further controllable to rotate about
longitudinal axis 124 relative to inner blade portion 128. In alternative embodiments
where outer blade portion 130 extends, at least in part, obliquely from inner blade
11
portion 128, pivotably coupling outer blade portion 130 to inner blade portion 128
facilitates rotating outer blade portion 130 about a longitudinal axis (not shown) of
outer blade portion 130.
[0031] In the exemplary embodiment, rotor blade 112 includes a
5 bearing 140, or more broadly, a rotatable element. As used herein throughout the
specification and claims, the terms “rotatable element” and “bearing element” are
understood to have substantially the same meaning. Bearing 140 includes a first end
142 coupled to inner blade portion 128 and a second end 144 coupled to outer blade
portion 130. Bearing element 140 includes a bearing body 146 extending longitudinally
10 between bearing first end 142 and bearing second end 144. Bearing second end 144 is
rotatable about longitudinal axis 124 relative to bearing first end 142 to facilitate
rotating, tilting, or other similar movements of outer blade portion 130 relative to inner
blade portion 128. In particular, in the exemplary embodiment, bearing body 146 is
configured for elastic deformation about longitudinal axis 124 (i.e., twist about the
15 length of bearing body 146 between bearing first end 142 and bearing second end 144)
to facilitate rotating bearing second end 144 relative to bearing first end 142. More
specifically, in the exemplary embodiment, bearing element 140 is an elastic flexure
bearing and is composed of an elastic material capable of repeatable rotational flexing
without damaging or disintegrating bearing body 146. In the exemplary embodiment,
20 bearing body 146 is formed of a composite material. In alternative embodiments,
bearing body 146 is formed of any material that enables bearing element 140 to
function as described herein. For example, and without limitation, in some alternative
embodiments, bearing element 140 is formed of at least one of a metallic, non-metallic,
polymeric composite, and metal composite material.
25 [0032] In the exemplary embodiment, bearing element 140 is
configured for low torsional resistance (i.e., low resistance to rotational deformation
about longitudinal axis 124) and relatively high resistance to bending (i.e., high
12
resistance to oblique deformation with respect to longitudinal axis 124). As a result,
in the exemplary embodiment, bearing element 140 provides structural support to outer
blade portion 130 with respect to various forces (e.g., wind loads and centrifugal loads)
acting on outer blade portion 130 during use of wind turbine 100 (shown in FIG. 1). In
5 addition, bearing element 140 facilitates pitching outer blade portion 130 relative to
inner blade portion 128 during use of wind turbine 100 (shown in FIG. 1).
[0033] In the exemplary embodiment, outer blade portion 130 is
coupled to inner blade portion 128 via bearing element 140 such that a gap 141 (shown
in FIG. 3) is defined between connection end 134 of inner blade portion 128 and pivot
10 end 138 of outer blade portion 130. Gap 141 allows for reduced static and kinetic
friction between inner blade portion 128 and outer blade portion 130 to facilitate
pitching outer blade portion 130. In alternative embodiments, gap 141 is sealed by a
flexible membrane (not shown). In further alternative embodiments, inner blade
portion 128 is coupled to outer blade portion 130 in any manner that enables rotor blade
15 112 to function as described herein.
[0034] In the exemplary embodiment, inner blade portion 128
includes a support structure 148 extending within inner blade body 132. Support
structure 148 is coupled to inner blade body 132 at least two points of contact with
inner blade body 132. Support structure 148 is coupled to inner blade body 132 at a
20 point longitudinally between hub pitching mechanism 126 and connection end 134.
Thus, in the exemplary embodiment, the pivotable coupling between inner blade
portion 128 and outer blade portion 130 via bearing element 140 does not interfere with
hub pitching mechanism 126. In alternative embodiments, support structure 148 is
coupled to inner blade body 132 in any manner that enables rotor blade 112 to function
25 as described herein. In the exemplary embodiment, support structure 148 is shaped
complementary to inner blade body 132. More specifically, in the exemplary
embodiment, support structure 148 defines an outer perimeter that corresponds to an
13
inner surface 150 of inner blade body 132 at the point of inner blade body 132 at which
support structure 148 is coupled. In other words, in the exemplary embodiment,
support structure 148 is sized to be in contact with inner blade body 132 along the entire
perimeter of support structure 148. In alternative embodiments, support structure 148
5 is embedded in inner blade body 132. In further alternative embodiments, support
structure 148 is shaped and sized in any manner that enables rotor blade 112 to function
as described herein. In the exemplary embodiment, support structure 148 is formed of
a polymer based composite material. In alternative embodiments, support structure
148 is formed of any material that enables support structure 148 to function as
10 described herein. For example, and without limitation, in some alternative
embodiments, support structure 148 is formed of at least one of a polymer, metal and/or
metal alloy, and metallic composite material.
[0035] In the exemplary embodiment, bearing first end 142 is
coupled to support structure 148. In particular, bearing element 140 is fixedly coupled
15 to support structure 148 such that bearing first end 142 is not rotatable with respect to
support structure 148. Bearing body 146 extends away from support structure 148
along longitudinal axis 124 towards to outer blade portion 130. Bearing body 146
defines a width, indicated generally at W1, and a height (e.g., extending into the page
and out of the page). In alternative embodiments, bearing body 146 includes a tubular
20 or polygonal cross-section. In the exemplary embodiment, the height of bearing body
146 (not shown) is greater than the width W1 of bearing body 146 such that bearing
body 146 has a generally rectangular cross section. Bearing body 146 defines a length,
indicated generally at L4, extending between bearing first end 142 and bearing second
end 144. In the exemplary embodiment, bearing element 140 is positioned within inner
25 blade portion 128 and outer blade portion 130 such that bearing body length L4 is
substantially parallel to longitudinal axis 124 of rotor blade 112. In alternative
embodiments, bearing body 146 has any shape that enables rotor blade 112 to function
14
as described herein. For example, and without limitation, in some alternative
embodiments, bearing body 146 is curved along the length L4 of bearing body 146.
[0036] In the exemplary embodiment, rotor blade 112 includes a
pitching device 152 coupled to outer blade portion 130 and an inner hub 154 coupled
5 to inner blade portion 128. Bearing body 146 extends through inner hub 154 and is
integrally formed with pitching device 152 at bearing second end 144. In alternative
embodiments, bearing element 140 is removably attached to pitching device 152. An
actuation mechanism (not shown) is configured to impart relative motion on outer
blade portion 130 relative to inner blade portion 128. More specifically, the actuation
10 mechanism is configured to drive rotation of pitching device 152 relative to inner hub
154 to drive rotation of bearing second end 144 relative to bearing first end 142. In the
exemplary embodiment, the actuation mechanism includes a gear and pinion (not
shown), anchored to the inner hub, for driving rotation of pitching device 152 relative
to inner hub 154. In alternative embodiments, the actuation mechanism may be any
15 one of a motor drive, hydraulic actuator, and pneumatic actuator. In yet further
alternative embodiments, rotor blade 112 includes any actuation mechanism that
enables rotor blade 112 to function as described herein. For example, as described in
greater detail below with respect to FIGS. 5 and 6, in some alternative embodiments,
the actuation mechanism may include a motorized cable system.
20 [0037] In the exemplary embodiment, during operation of wind
turbine 100 (shown in FIG. 1), hub pitching mechanism 126 may be controlled to pitch
the entire rotor blade 112 (e.g., pitch inner blade portion 128 and outer blade portion
130 relative to rotatable hub 110). In addition, the actuation mechanism (not shown)
may be controlled to pitch only outer blade portion 130 of rotor blade 112.
25 [0038] FIG. 3 is an enlarged schematic sectional view of an
alternative rotor blade 112 for use in wind turbine 100 (shown in FIG. 1). FIG. 4 is a
schematic end view of a portion of alternative rotor blade 112 shown in FIG. 3.
15
Alternative rotor blade 112 shown in FIGS. 3 and 4 is substantially similar to rotor
blade 112 described above with respect to FIG. 2, except as described below.
[0039] In the exemplary embodiment, rotor blade 112 includes a pivot
structure 156 coupled to outer blade portion 130. Pivot structure 156 is shaped in
5 correspondence with outer blade body 136. More specifically, in the exemplary
embodiment, pivot structure 156 defines an outer perimeter that corresponds to an inner
surface 158 of outer blade body 136 at the point of outer blade body 136 at which pivot
structure 156 is coupled (e.g., pivot end 138). In other words, in the exemplary
embodiment, support structure 148 is sized to be in contact with inner blade body 132
10 along the entire perimeter of support structure 148. In alternative embodiments, pivot
structure 156 is coupled to outer blade body 136 at least two points of contact with
outer blade body 136. In yet further embodiments, pivot structure 156 is coupled to
outer blade body 136 in any manner that enables rotor blade 112 to function as
described herein.
15 [0040] In the exemplary embodiment, bearing element 140 includes
four bearing bars 160 (each shown in FIG. 4) each coupled to support structure 148 at
respective first ends 142 (shown in FIG. 3). More specifically, in the exemplary
embodiment, bearing bars 160 are each coupled to support structure 148 adjacent the
perimeter of support structure 148 (i.e., adjacent inner blade body 132). In alternative
20 embodiments, bearing element 140 includes any number of bearing bars 160 that
enables rotor blade 112 to function as described herein. For example, and without
limitation, in alternative embodiments, the number and placement of bearing bars 160
are based on a desired torsional stiffness and/or bending stiffness of bearing element
140. In particular, increasing the number of bearing bars 160 increases the torsional
25 stiffness of bearing element (i.e., increasing the drive power necessary to impart
rotational movement between outer blade portion 130 and inner blade portion 128)
while also increasing the bending stiffness of rotor blade 112 (i.e., providing increased
16
resistance against bending between inner blade portion 128 and outer blade portion
130). In the exemplary embodiment, bearing bars 160 are each coupled to pivot
structure 156 at respective second ends 144 and each extend obliquely relative to
longitudinal axis 124 between first ends 142 and second ends 144. In other words, in
5 the exemplary embodiment, bearing bars 160 generally converge at pivot structure 156.
In alternative embodiments, bearing bars 160 are coupled to inner blade portion 128
and outer blade portion 130 in any manner that enables rotor blade 112 to function as
described herein.
[0041] Referring to FIG. 4, in the exemplary embodiment, inner blade
10 portion 128 and pivot structure 156 of alternative rotor blade 112 are shown. In the
exemplary embodiment, pivot structure 156 is annular, defining an inner opening,
indicated generally at 162, through which support structure 148 is visible. More
specifically, pivot structure 156 is shaped as an annular oval or circular in
correspondence with the cross section of outer blade portion 130. Bearing bars 160 are
15 each coupled to pivot structure 156 at second ends 144 such that second ends 144 are
substantially circumferentially spaced about pivot structure 156. In alternative
embodiments, bearing bars 160 extend between support structure 148 and pivot
structure 156 in any manner that enables rotor blade 112 to function as described
herein.
20 [0042] Referring back to FIG. 3, in the exemplary embodiment,
pitching device 152 and inner hub 154 are shown in broken lines to reveal internal
connections between bearing bars 160 and pivot structure 156. More specifically, in
the exemplary embodiment, pitching device 152 is coupled to pivot structure 156.
Pitching drive 152 is configured to drive rotation of outer blade portion 130 relative to
25 inner blade portion 128 in substantially the same manner as described above with
respect to FIG. 2. In particular, an actuation mechanism (not shown) is coupled to
pitching device and is configured to drive rotation of pitching device 152 relative to
17
inner hub 154 to drive rotation of bearing second ends 144 relative to bearing first ends
142. In alternative embodiments, pitching device 152 and inner hub 154 are configured
in any manner that enables rotor blade 112 to function as described herein. In further
alternative embodiments, rotor blade 112 does not include at least one of pitching
5 device 152 and inner hub 154.
[0043] FIG. 5 is a schematic sectional view of a further alternative
rotor blade 112 for use in wind turbine 100 (shown in FIG. 1). Alternative rotor blade
112 shown in FIG. 5 is substantially similar to rotor blade 112 described above with
respect to FIG. 2, except as described below.
10 [0044] In the exemplary embodiment, rotor blade 112 includes a
plurality of cables 164. More specifically, in the exemplary embodiment, rotor blade
112 includes three cables 164 coupled at hub end 120 of inner blade portion 128 and
extending through inner blade body 132 to outer blade portion 130. In alternative
embodiments, rotor blade 112 includes any number of cables that enable rotor blade to
15 function as described herein.
[0045] In the exemplary embodiment, bearing element 140 extends
between inner hub 154 and pitching device 152. More specifically, in the exemplary
embodiment, bearing first end 142 is coupled to inner hub 154 and bearing second end
144 is coupled to pitching device 152. In the exemplary embodiment, bearing element
20 140 is a pitch bearing, configured to facilitate rotating bearing second end 144 relative
to bearing first end 142. Pitching device 152 is coupled to outer blade portion 130. As
a result, rotation of bearing second end 144 relative to bearing first end 142 facilitates
rotation of outer blade portion 130 relative to inner blade portion 128 about longitudinal
axis 124.
25 [0046] In the exemplary embodiment, cables 164 are coupled to hub
end 120 of inner blade portion 128, and extend therefrom to pitching device 152. In the
18
exemplary embodiment, the actuation mechanism (not shown) is positioned coupled to
inner hub 154. In alternative embodiments, the actuation mechanism (not shown) is
located in any component of wind turbine 100 that enables actuation mechanism (not
shown) to function as described herein. For example, and without limitation, in some
5 alternative embodiments, the actuation mechanism is positioned adjacent pitching
device 152.
[0047] In the exemplary embodiment, cables 164 are coupled to
pitching device 152 such that cables are substantially equidistantly spaced about the
circumference of pitching device 152 to facilitate imparting rotational movement. More
10 specifically, in the exemplary embodiment, bearing element 140 is preloaded by cables
164. In other words, cables 164 apply an axial load on bearing element 140 to stabilize
positioning of outer blade portion 130 relative to inner blade portion 128 and to drive
pitching of outer blade portion 130. Cables 164 are maintained in substantially equal
tension to maintain rotational alignment of outer blade portion 130 relative to inner
15 blade portion 128. The actuation mechanism (not shown), is configured to impart
rotational movement to pitching device 152 relative to inner hub 154, thereby imparting
rotation in bearing second end 144 relative to bearing first end 142 to facilitate rotating
outer blade portion 130 relative to inner blade portion 128. In alternative embodiments,
cables 164 are coupled to pitching device 152 in any manner that enables rotor blade
20 112 to function as described herein.
[0048] FIG. 6 is a schematic sectional view of a yet further alternative
rotor blade 112 for use in wind turbine 100 (shown in FIG. 1). Alternative rotor blade
112 shown in FIG. 6 is substantially similar to rotor blade 112 described above with
respect to FIG. 5, except as described below.
25 [0049] In the exemplary embodiment, bearing element 140 is a roller
bearing. In particular, in the exemplary embodiment, bearing element 140 is a tapered
roller bearing. Bearing element 140 is configured to withstand large axial compressive
19
loads (i.e., compressive loads along longitudinal axis 124 of rotor blade 112) during
operation of wind turbine 100 (shown in FIG. 1). In particular, bearing element 140
includes an inner cup 166, an outer cup 168, and a plurality of tapered roller elements
170 coupled between inner cup 166 and outer cup 168. In the exemplary embodiment,
5 inner cup 166 defines bearing first end 142 and outer cup 168 defines bearing second
end 144.
[0050] In the exemplary embodiment, inner cup 166 is coupled to
inner blade portion 128 and outer cup 168 is coupled to outer blade portion 130. In
particular, in the exemplary embodiment, support structure 148 is coupled to inner
10 blade body 132 at connection end 134 of inner blade portion 128. Outer blade portion
130 includes pivot structure 156 coupled to outer blade body 136 at pivot end 138 of
outer blade portion 130. Inner cup 166 is fixedly coupled to support structure 148 and
outer cup 168 is fixedly coupled to pivot structure 156. Roller elements 170 are
configured to rotate between inner cup 166 and outer cup 168.
15 [0051] In the exemplary embodiment, inner cup 166 and outer cup
168 define a bearing bore, indicated generally at 172. Roller elements 170 each include
a bore end 174 and an outer end 176. For each of roller elements 170, bore end 174 is
located adjacent bearing bore 172 and roller elements 170 extend radially outward
therefrom to outer ends 176. In the exemplary embodiment, roller elements 170 are
20 tapered between bore end 174 and outer end 176. In alternative embodiments, bearing
element 140 is an angular contact bearing. In further alternative embodiments, bearing
element 140 is any rotatable element that enables rotor blade 112 to function as
described herein.
[0052] In the exemplary embodiment, rotor blade 112 includes three
25 cables 164 extending from hub end 120 (shown in FIG. 5) of rotor blade 112 to outer
cup 168. In alternative embodiments, rotor blade 112 includes any number of cables
164 that enable rotor blade 112 to function as described herein. Cables 164 are operable
20
to drive rotation of outer blade portion 130 relative to inner blade portion 128 in
substantially the same manner as described above with respect to FIG. 5. In particular,
in the exemplary embodiment, cables 164 are coupled to outer cup 168 at substantially
even tension. In particular, even tension is enabled by incorporating springs (not
5 shown) at one or both ends of cables 164. An actuation mechanism (not shown) may
also be used to adjust the tension of cables 164 relative to one another. In alternative
embodiments, actuation mechanism (not shown) is configured to drive rotation of outer
blade portion 130 relative to inner blade portion 128 in any manner that enables rotor
blade 112 to function as described herein.
10 [0053] FIG. 7 is a flow diagram of an exemplary method 200 of
assembling rotor blade 112 for use in wind turbine 100 (shown in FIG. 1). Blade 112
includes inner blade portion 128 having a first and second end 120, 134 (each shown
in FIG. 2). Blade 112 also includes outer blade portion 130 having a first and second
end 138, 122 (each shown in FIG. 2). Method 200 includes coupling 202 first end 138
15 of outer blade portion 130 to second end 134 of inner blade portion 128. Method 200
also includes coupling 204 first end 142 of rotatable element 140 to inner blade portion
128. Method 200 includes coupling 208 second end 144 of rotatable element 140 to
outer blade portion 130 such that outer blade portion 130 is rotatable relative to inner
blade portion 128.
20 [0054] An exemplary technical effect of the methods, systems, and
apparatus described herein includes at least one of: (a) improved lifespan of wind
turbine components; (b) reduced maintenance and servicing for wind turbine
components; (c) improved modularity of rotor blades; and (d) improved control over
pitching of rotor blades.
25 [0055] Exemplary embodiments of wind turbines, rotor blades for use
in wind turbine systems, and methods for assembling rotors for use in wind turbine
systems are described above in detail. The methods and systems are not limited to the
21
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
5 the wind turbine system as described herein. Rather, the exemplary embodiment can
be implemented and utilized in connection with many other wind turbine applications.
[0056] 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
10 be referenced and/or claimed in combination with any feature of any other drawing.
[0057] 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
15 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.

WE CLAIM:
1. A wind turbine (100) comprising:
a hub (110) rotatable about an axis; and
a blade (112) coupled to said hub (110) and comprising:
an inner blade portion (128) comprising a first end (120) and a
5 second end (134), said inner blade portion (128) coupled to said hub (110) at said first
end (120) and extending radially outward from said hub (110) to said second end;
and
an outer blade portion (130) comprising a first end (138) and a
second end (122), said first end (138) of said outer blade portion (130) pivotably
10 coupled to said second end (134) of said inner blade portion (128).
2. The wind turbine (100) of claim 1, wherein said blade (112)
defines a longitudinal axis (124) extending from said first end (120) of said inner
blade portion (128) to said second end (122) of said outer blade portion (130),
wherein said outer blade portion (130) is configured to rotate about the longitudinal
15 axis (124) relative to said inner blade portion (128).
3. The wind turbine (100) of claims 1-2, wherein said blade (112)
defines a longitudinal axis (124) extending from said first end (120) of said inner
blade portion (128) to said second end (122) of said outer blade portion (130),
wherein said first end (120) of said inner blade portion (128) is pivotably coupled to
20 said hub (110) such that said inner blade portion (128) is configured to rotate about
the longitudinal axis (124).
4. The wind turbine (100) of any of the preceding claims, wherein
said outer blade portion (130) extends obliquely relative to said inner blade portion
23
(128).
5. The wind turbine (100) of any of the preceding claims, further
comprising a rotatable element (140) extending between said inner blade portion
(128) and said outer blade portion (130), said rotatable element (140) comprising a
5 first end (142) coupled to said inner blade portion (128) and a second end (144)
coupled to said outer blade portion (130).
6. The wind turbine (100) of Claim 5, wherein said rotatable
element second end (144) is rotatable relative to said rotatable element first end (142)
to facilitate rotating said outer blade portion (130) relative to said inner blade portion
10 (128).
7. The wind turbine (100) of Claim 5, wherein said rotatable
element (140) is an elastic flexure bearing.
8. The wind turbine (100) of Claim 7, wherein said second end
(144) of said rotatable element (140) is rotatable at least +/- one degree relative to
15 said first end (142) of said rotatable element (140).
9. The wind turbine (100) of Claim 5, further comprising a
support structure (148) positioned within said inner blade portion (128), said rotatable
element (140) further comprising a body (146) extending a length from said support
structure (148) to said outer blade portion (130), wherein said body (146) is
20 configured for elastic deformation about the length of said body (146).
10. The wind turbine (100) of Claim 9, wherein said body (146)
comprises a plurality of bars (160) each extending from said support structure (148)
to said outer blade portion (130).
11. The wind turbine (100) of any of the preceding claims, further
24
comprising a plurality of cables (164) extending between said inner blade portion
(128) and said outer blade portion (130), said plurality of cables (164) configured to
stabilize positioning of said outer blade portion (130) relative to said inner blade
portion (128) and to drive pitching of said outer blade portion (130).
5 12. A blade (112) for use in a wind turbine (100) system
comprising:
an inner blade portion (128) comprising a first end (120) and a second
end (134);
an outer blade portion (130) comprising a first end (138) and a second
10 end (122), said first end (138) of said outer blade portion (130) coupled to said
second end (134) of said inner blade portion (128); and
a rotatable element (140) extending between said inner blade portion
(128) and said outer blade portion (130), said rotatable element (140) comprising a
first end (142) coupled to said inner blade portion (128) and a second end (144)
15 coupled to said outer blade portion (130), wherein said rotatable element second end
(144) is rotatable relative to said rotatable element first end (142) to facilitate rotating
said outer blade portion (130) relative to said inner blade portion (128).
13. The blade (112) of Claim 12, wherein said rotatable element
(140) is an elastic flexure bearing.
20 14. The blade (112) of Claim 13, wherein said second end (144) of
said rotatable element (140) is rotatable at least +/- one degree relative to said first
end (142) of said rotatable element (140).
15. The blade (112) of claims 12-14, further comprising a support
structure (148) positioned within said inner blade portion (128), said rotatable
25
element (140) further comprising a flexible support member (146) extending from
said support structure (148) to said outer blade portion (130).