U.S. patent application number 11/800399 was filed with the patent office on 2007-11-22 for wind turbine and support structure and method of controlling the rotational speed of such wind turbine.
Invention is credited to Raymond Browning.
Application Number | 20070269311 11/800399 |
Document ID | / |
Family ID | 38668346 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070269311 |
Kind Code |
A1 |
Browning; Raymond |
November 22, 2007 |
Wind turbine and support structure and method of controlling the
rotational speed of such wind turbine
Abstract
A wind turbine system and a method for controlling a rotational
speed of a rotor of such wind turbine system are provided. The
system included a wind turbine having a rotor having airfoils
having an orientation relative to wind and a rotational axis. The
system further includes a structure supporting the wind turbine
above ground. The support structure is coupled to the ground. The
structure has first portion closer to the wind turbine and a second
portion farther from the wind turbine. The first portion will move
farther in response to the wind acting across the structure than
said second portion causing the turbine rotational axis to tilt.
The method includes tilting the rotor rotational axis about an
angle, and varying the angle in response to changes of the wind
force.
Inventors: |
Browning; Raymond; (San
Carlos, CA) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
PO BOX 7068
PASADENA
CA
91109-7068
US
|
Family ID: |
38668346 |
Appl. No.: |
11/800399 |
Filed: |
May 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60797332 |
May 3, 2006 |
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Current U.S.
Class: |
416/132B |
Current CPC
Class: |
B63H 9/065 20200201 |
Class at
Publication: |
416/132.00B |
International
Class: |
B63H 1/06 20060101
B63H001/06 |
Claims
1. A wind turbine system comprising: a wind turbine having a rotor
having airfoils and a rotational axis; and a structure supporting
the wind turbine above ground, said structure being coupled to the
ground, wherein said structure has first portion closer to the wind
turbine and a second portion farther from the wind turbine, wherein
said first portion will move farther in response to a wind acting
across said structure than said second portion causing said turbine
rotational axis to tilt.
2. The wind turbine system as recited in claim 1 wherein said
structure is a flexible structure comprising a flexibility allowing
for said first portion to move farther than said second portion in
response to said wind.
3. The wind turbine system as recited in claim 1 wherein said
structure is coupled to a base with a flexible member, said base
being coupled to the ground.
4. The wind turbine system as recited in claim 3 wherein said
flexible member is a spring.
5. The wind turbine system as recited in claim 1 wherein said wind
turbine is a vertical wind turbine and wherein the rotation axis
when not tilted is generally vertical.
6. The wind turbine system as recited in claim 5 wherein said
structure comprises a flexible shaft, wherein said shaft flexes in
response to said wind whereby said first portion moves father than
said second portion.
7. The wind turbine system as recited in claim 6 further comprising
a shadowing structure coupled the turbine for blocking a portion of
the wind from reaching said wind turbine rotor when said rotational
axis is tilted.
8. The wind turbine system as recited in claim 7 wherein said
portion of the wind being blocked increases as the flexing of said
shaft increases.
9. The wind turbine system as recited in claim 7 wherein said
shadowing structure defines a base of said rotor on which said
airfoils are mounted.
10. The wind turbine system as recited in claim 1 further
comprising a shadowing means for blocking a portion of the wind
from reaching said wind turbine rotor when said rotational axis is
tilted.
11. The wind turbine system as recited in claim 10 wherein said
shadowing means will block larger portion of the wind as the wind
speed increases.
12. The wind turbine system as recited in claim 1 wherein said
structure comprises a flexible shaft formed from a glass fiber
composite, wherein said shaft flexes in response to said wind
whereby said first portion moves father than said second
portion.
13. The wind turbine system as recited in claim 12 wherein said
shaft is pultruded.
14. The wind turbine as system as recited in claim 1 wherein said
structure is pivotably coupled to a member coupled to the
ground.
15. A method for controlling a rotational speed of a vertical wind
turbine rotor mounted on a support structure and rotating about a
generally vertical rotational axis by being exposed to wind having
a force, said rotor comprising airfoils exposed to the wind, the
method comprising: tilting said rotor rotational axis about an
angle; and varying said angle in response to changes of said wind
force.
16. The method as recited in claim 15 wherein varying comprises
increasing said angle when said wind force increases.
17. The method as recited in claim 15 wherein said tilting
comprises decreasing a rotational efficiency of said rotor for a
given wind speed.
18. The method as recited in claim 15 father comprising blocking a
portion of the wind from acting on said rotor as the angle
increases for controlling the amount of force exerted on said rotor
by said wind.
19. The method as recited in claim 17 further comprising increasing
said wind portion being blocked as said wind force increases.
20. The method as recited in claim 15 wherein titling said
rotational axis comprises pivoting said support structure relative
to the ground for tilting said rotational axis.
21. The method as recited in claim 15 wherein said tilting
comprises flexing said structure for tilting said rotational axis.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims priority of a U.S.
Provisional Application, Ser. No. 60/797,332 filed on May 3, 2006,
the contents of which are fully incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to vertical wind
turbines, and more particularly to a vertical wind turbine with a
support capable of flexing and/or pivoting. Wind turbines of
various designs are in use in converting wind energy to electrical
energy. Designs variations include wind turbines with horizontal
axes, vertical axes, drag propulsion, aerodynamic lift, turbines,
and sails. Horizontal axis wind turbines typically include a tall
tower and a propeller or fan-like rotor mounted at the top of the
tower for rotation about an axis substantially parallel to the
earth's surface. Vertical wind turbines are more varied with cups,
half cylinders, eggbeater like blades, flat blades, paddles, or
airfoils (individually or collectively referred to herein as
"airfoils") rotating around a vertical axis. A vertical wind
turbine may have a rotor with airfoils which may be fixed or
movable and rotating about a central shaft. A plurality of airfoils
mounted on stationary rings may surround the rotor and serve to
direct and compress air from the wind before is directed at the
rotor airfoils. Vertical axis wind turbines are divided generally
into lift- and drag-types.
[0003] The advantage of the horizontal wind turbine is in the
design of the propeller like turbine. The blades of the horizontal
wind turbine are typically airfoils which provide lift. The lifting
blades can spin faster than the air flow, and indeed may be
supersonic at the tips, thus providing high efficiency and high
rotation speed for generating electricity. A disadvantage of the
horizontal axis wind turbine lies in the fact that the rotor must
face either into or away from the direction of the wind and a yaw
mechanism is required to rotate the rotor about the vertical axis
of the tower to keep the rotor in proper alignment with the wind
flow. Since a mechanical means of delivering power to the ground
could cause the rotor to yaw out of alignment with the wind, energy
conversion devices, such as generators; power transmission
equipment; and related equipment are typically also mounted atop
the tower. A structurally robust and costly tower is required to
support the weight of the elevated equipment. Maintenance of
horizontal axis turbines can be complex and costly because the
equipment is located at the top of the tower. While horizontal axis
wind turbine installations are relatively complex and expensive,
they are the most common wind turbine configurations in current
use.
[0004] The advantage of the vertical axis wind turbine is that its
exposure remains constant regardless of the wind direction. A great
deal of the cost of wind turbines results from high strength
materials that are used to withstand high stresses, which result
from the high speed at which they operate. Wind turbines are also
subject to very high amplitude and high frequency vibrations, which
result in fatigue to the various components of the wind turbines.
To minimize these vibrations, the airfoils and other rotational
components of these systems must be perfectly balanced.
Additionally, wind turbines are exposed to adverse weather
conditions such as high winds, snow, ice, and ultraviolet
radiation. Substantial engineering and maintenance resources have
to be devoted to the design and operation of these wind turbines so
that they can withstand the multitude of forces, as well as the
adverse conditions, to which they will be subjected. Wind turbines
are often severely damaged by high wind conditions.
[0005] Wind turbines have a relatively small range of wind speeds
within which they will operate efficiently, typically 20 to 40
miles per hour. At lower speeds the electricity generation is
inefficient and at higher speeds the rotor is exceeding its safe
operating limit and must be damped electrically to prevent damage.
Obviously, the necessity for such a high minimum wind speed greatly
reduce the geographical areas where wind turbines can be used
economically. Additionally, the necessity for providing the highest
average wind speeds over the time of operation requires the wind
turbines being set high above the ground on very tall masts. Tall
masts further increase the cost of installation and maintenance.
Consequently, a wind generating power source that operates over a
wide range of wind speeds, with low capital, installation, and
maintenance costs is desirable.
SUMMARY OF THE INVENTION
[0006] The present invention relates generally to vertical wind
turbines, and more particularly to a vertical wind turbine with a
support assembly, and more particularly to a support assembly that
minimizes damage in high gusting winds, and more particularly to a
support structure that is a monopole, and more particularly to a
monopole that is formed from a glass fiber composite, and more
particularly a pultruded glass fiber composite. In another
exemplary embodiment of the invention the vertical wind turbine is
supported by an elevating support structure that flexes or pivots
during wind gusts. In yet another exemplary embodiment of the
invention the flexing of the support assembly under a high wind
load reduces the efficiency of the vertical wind turbine and thus
regulates the rotational speed of the wind turbine. In a further
exemplary embodiment of the invention the design of the wind
turbine rotor and the wind resistance of the rotor base plate are
tuned to regulate the rotational speed of the wind turbine under
differing wind conditions.
[0007] In an exemplary embodiment a wind turbine system is
provided. The system included a wind turbine having a rotor having
airfoils and a rotational axis. The system further includes a
structure supporting the wind turbine above ground. The support
structure is coupled to the ground. The structure has first portion
closer to the wind turbine and a second portion farther from the
wind turbine. The first portion will move farther in response to a
wind acting across the structure than the second portion causing
the turbine rotational axis to tilt. In another exemplary
embodiment, the structure is a flexible structure and has a
flexibility allowing for the first portion to move farther than the
second portion in response to the wind. In yet another exemplary
embodiment, the structure is coupled to a base with a flexible
member and the base is coupled to the ground. In one exemplary
embodiment, the flexible member is a spring. In yet another
exemplary embodiment, the wind turbine is a vertical wind turbine
and the rotational axis when not tilted is generally vertical. In
yet a further exemplary embodiment, the structure includes a
flexible shaft which flexes in response to the wind whereby the
first portion moves father than the second portion. In another
exemplary embodiment, the shaft formed from a glass fiber
composite. In another exemplary embodiment, the shaft if
pultruded.
[0008] In yet another exemplary embodiment, the system further
includes a shadowing structure, or a means, coupled the turbine for
blocking a portion of the wind from reaching the wind turbine rotor
when the rotational axis is tilted. In another exemplary
embodiment, the portion of the wind being blocked increases as the
flexing of the shaft increases. In a further exemplary embodiment,
the shadowing structure defines a base of the rotor on which the
airfoils are mounted. In yet a further exemplary embodiment, the
structure is pivotably coupled to a member coupled to the
ground.
[0009] In another exemplary embodiment a method is provided for
controlling a rotational speed of a vertical wind turbine rotor
mounted on a support structure and rotating about a generally
vertical rotational axis by being exposed to wind having a force,
the rotor having airfoils exposed to the wind. The method includes
tilting the rotor rotational axis about an angle, and varying the
angle in response to changes of the wind force. In another
exemplary embodiment, varying includes increasing the angle when
the wind force increases. In a further exemplary embodiment, the
method also includes blocking a portion of the wind from acting on
the rotor as the angle increases for controlling the amount of
force exerted on the rotor by the wind. In yet another exemplary
embodiment, the method further includes increasing the wind portion
being blocked as the wind force increases. In yet a further
exemplary embodiment, tilting the rotational axis includes pivoting
the support structure relative to the ground for tilting the
rotational axis. In another exemplary embodiment, tilting included
flexing the support structure for tilting the rotational axis. In
yet another exemplary embodiment, tilting includes decreasing a
rotational efficiency of the rotor for a given wind speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will be better understood and the objects and
advantages of the present invention will become apparent when
consideration is given to the following detailed description
thereof. Such description makes reference to the annexed drawings
wherein:
[0011] FIG. 1 is a illustration of the wind turbine assembly;
[0012] FIG. 2 illustrates in top view of a vertical wind turbine
rotor with the upper base plate removed;
[0013] FIG. 3 illustrates schematically a rotor in perspective view
having a plurality of airfoils attached to bottom and top base
plates;
[0014] FIG. 4 illustrates schematically the tilting action of the
wind turbine assembly under low and high wind conditions;
[0015] FIG. 5 illustrates schematically the wind shadowing during
the tilting action of the wind turbine assembly under high wind
conditions; and
[0016] FIG. 6 illustrates in plan view an alternative arrangement
of a plurality of airfoils on a base plate of a vertical wind
turbine.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring to FIGS. 1 through 6, wherein like reference
numerals refer to like components in the various views, there is
illustrated therein a new and improved vertical wind turbine
assembly. In an exemplary embodiment, a wind turbine assembly
generating electricity with lower capital, installation, and
maintenance costs is provided. In one exemplary embodiment, a
vertical wind turbine elevated on a supporting structure that has a
high compliancy is provided. In an exemplary embodiment, the
supporting structure is a monopole that is capable of elastically
bending. In another exemplary embodiment, the monopole is a
lightweight composite pole, and may be formed as a glass/resin
pultruded composite. In another exemplary embodiment of the
invention, a vertical turbine rotor is provided that has
attachments that provide wind shadowing on the rotor airfoils when
the supporting structure is bending under wind load.
[0018] It should be noted that the terms "upper," "lower," "above"
and "below" as used herein are relative terms to describe the
relative location of parts and not the exact locations of such
parts. For example, an "upper" part may be lower than a "lower"
part.
[0019] FIG. 1 illustrates an exemplary embodiment vertical wind
turbine assembly 100. The assembly includes a vertical wind turbine
101 having a vertical wind turbine rotor 115 including a plurality
of airfoils 102 a, b, c, an upper base plate 103 and a lower base
plate 104. The upper base plate 103 and the lower base plate 104
support the airfoils 102 a, b, c and hold them in the correct
orientation. The turbine is mounted on a supporting structure such
as a monopole 107. The upper base plate 103 has an upper central
cylindrical bearing 105 and the lower base plate 104 has lower
central cylindrical bearing 106 that allows the vertical wind
turbine rotor 115 to rotate relative to the monopole 107. In the
shown exemplary embodiment, the vertical turbine is mounted on the
monopole 107 via the lower central cylindrical bearing 106. The
lower central bearing 106 may incorporate an electrical generating
device which when rotated by the rotor generates electric energy.
Other types of bearings may also be used. A wind shadowing
structure 108, such as a plate is attached underneath the airfoils
102 a, b, c. In an exemplary embodiment the shadowing structure is
attached below the lower base plate. The wind turbine assembly 100
may incorporates a plinth 109 coupled to the monopole that is used
to anchor the assembly to the ground. In the arrangement shown in
FIG. 1 the plinth 109 allows the monopole 107 to be raised and
lowered by pivotable connecting the monopole to the plinth at pivot
point 110. A member 111 may be used to pivotably couple the
monopole to the plinth. It alternate exemplary embodiments, a
simple hole in a base or other arrangement for mounting the
monopole can be substituted for the plinth 109.
[0020] FIG. 2 illustrates in plan how a plurality of symmetric
airfoils 201 a, b, c, d can be arranged on a rotor base of an
exemplary embodiment rotor of a vertical wind turbine. The
plurality of symmetric airfoils 201 a, b, c, d in an exemplary
embodiment have the same size and shape and are equidistantly
spaced around a rotor base support such as the rotor lower base
plate 104. The lower base plate is coupled to the lower cylindrical
bearing 106 by means of axial spokes 204 a, b, c, d. The axial
spokes 204 a, b, c, d also act as devices to shadow the symmetric
airfoils 201 a, b, c, d when the rotor is tilted with respect to
the wind direction. While four symmetric airfoils 201 a, b, c, d
are illustrated in FIG. 2 it can be appreciated that numerous
alternative arrangements of airfoils and number of airfoils are
possible. It should be noted that the upper and lower base plates
may be solid or ring-like annular plates.
[0021] FIG. 3 is a simplified illustration of how the base plates
and airfoils are arranged to form a rotor 300 of an exemplary
embodiment vertical wind turbine. Only three conventional airfoils
301 a, b, c are shown attached at their ends to the upper base
plate 103 and to the lower base plate 104. The two base plates 103,
104 shown are annular, i.e., they have central circular holes 304
a, b to allow for the attachment of bearings, such the upper
bearing 105 and the lower bearing 106, around a central shaft (not
shown) along the axis 305. Wind blowing against the conventional
airfoils 301 a, b, c from the side in the direction 306 will cause
the rotor 300 to rotate around the central axis 305. As the wind
speed increases greater force will be applied both to the rotation
around the axis 305 and to the side of the rotor assembly in the
wind direction 306.
[0022] FIG. 4 schematically illustrates the action of a wind
turbine 401 supported by an exemplary embodiment flexible monopole
402 in a high wind. The original position of the wind turbine 401
supported by a schematic monopole 402 is illustrated for low wind
conditions. At higher wind conditions the new position of the wind
turbine 401 with a flexed monopole 402 is shown in dashed. As the
monopole flexes (i.e., bends, in relation to the ground, a
rotational axis 403 of the rotor tilts at an angle 404. The tilted
angle 404 of the rotational axis places the wind turbine 403 in a
new position such that it is at an angle to the wind direction 405
and thus is not driven so efficiently. In other words, as the
rotational axis tilts, the rotational efficiency of the rotor for a
given wind speed decreases. In this regard, the rotational speed of
the rotor is controlled when the wind speed increases. The angle of
tilt 404 increases as the wind force increases. The angle may also
be controlled by controlling the flexibility of the supporting
structure or monopole 402.
[0023] FIG. 5 illustrates an exemplary embodiment wind shadowing
during the tilting action of the wind turbine assembly under high
wind conditions. A windward airfoil 501 and a lee airfoil 502 are
partly shadowed from the wind 503 by the shadowing structure 106.
This reduces the wind force acting on the windward airfoil 501 and
the lee airfoil 502. The speed of rotation of the rotor is thereby
reduced. It will be apparent to those ordinarily skilled in the art
that a large number of arrangements of shadowing structures are
possible.
[0024] FIG. 6 illustrates in plan an alternative exemplary
arrangement of a plurality of non radial airfoils 601 a, b, c, d on
the lower extended base plate 602 in a vertical wind turbine rotor
assembly. The extended base plate extends radially outward beyond
the airfoils. The extended base plate 602 acts to shadow the non
radial airfoils 601 a, b, c, d from the wind when the rotor is
tilted. In this regard, the lowered extended base plate may be used
to shadow the wind and reduce the wind force acting on the rotor as
the rotor is tilted.
[0025] An exemplary material for the monopole 107 is pultruded
glass fiber/resin composite. Glass fiber composite has the
advantage of being considerably more elastic than steel but with a
similar strength and much lower weight. As the modulus of
elasticity of a composite can be modulated by the use of different
types of glass fibers an appropriate flexibility for the monopole
can be obtained for different wind turbine designs. Further glass
fiber also does not work harden when it is flexed thus leading to
an extended lifetime. Also the geometry of the monopole may be
varied as necessary for obtaining a desired flexibility.
[0026] A very lightweight rotor assembly is desired and an
exemplary material for the airfoils is also pultruded glass fiber,
both for high strength and low weight. It would be expected that a
glass fiber composite would also be used for the base plates and
other parts, again reducing the weight of the entire wind turbine
assembly.
[0027] As the wind turbine tilted at an angle to the wind, its
rotational speed will be reduced compared to a directly upright
vertical wind turbine at right angles to the wind. This change in
angle means that as the wind velocity increases and the flexing of
the monopole increases due to the sideways force then the speed of
the wind turbine can be regulated to a degree between limits. As
the force flexing the monopole has a component largely from the
size of the wind turbine a stiffer pole is needed for a larger wind
turbine. As this is a complex system experiments may be necessary
to design the most appropriate flexure of the monopole given the
design parameters of the wind turbine and the generator.
Furthermore, the flexure may be controlled by using a wind turbine
having a desired weight. For example, the weight of the turbine may
be reduced if necessary by forming components of the turbine rotor
such as the airfoils from composite materials such as fiberglass In
an exemplary embodiment, in extremely high winds an exemplary
monopole will be flexed until the wind turbine is no longer facing
the wind and the main force will be acting on the wind shadowing
devices.
[0028] The exemplary flexible elevating support structure has been
described herein by way of a monopole, the support structure can
have different geometries and can be made in a large variety of
desired sizes. A monopole has however the advantage of being
axially symmetric and therefore will have the same flexural
dynamics whatever the wind direction. In other exemplary
embodiments, a spring or other elastic or flexible structure may be
used which is coupled to the ground and to the support structure to
assist with the flexing. i.e., bending of the support structure
relative to the ground so as to control the rotational speed of the
wind turbine rotor. For example member 111 shown in FIG. 1 may be a
rotational spring. With this embodiment, the support structure
pivots relative to the ground when exposed to wind force. With this
embodiment, the support structure may be very stiff and not
flexible. Furthermore with this embodiment, the tilt angle 404 for
a given wind force may be controlled by using springs of different
stiffness. In other exemplary embodiments, the support structure
may be coupled to a plinth or other base that anchors the structure
to the ground using a ball bearing or other type of bearing that
would allow the support structure to pivot in any direction. One or
more springs or other flexible members may be used to resist such
pivoting. Furthermore, spring may be required when the support
structure is relatively short so as to aid in the bending of the
structure relative to the ground.
[0029] The wind turbine apparatus of the invention can be made in a
large variety of desired sizes with alternative embodiments of a
lightweight rotor assembly. While exemplary embodiment vertical
wind turbines illustrated in FIGS. 1, 2 and 3 for use in
combination with the exemplary embodiment supporting structure,
other alternative wind turbine types can be used with the principle
of tilt to regulate rotational speed.
[0030] As can be seen an exemplary embodiment support structure
flexes during wind gusts thus reducing the rotational efficiency of
the vertical wind turbine for a given wind speed and thus
regulating the rotational speed of the wind turbine. Furthermore,
the wind turbine rotor and the wind resistance of the rotor lower
base plate further regulate the rotational speed of the wind
turbine under differing wind conditions by blocking a portion of
the wind reaching the rotor. In addition, the wind shadowing
structure also blocks a portion of the wind reaching the rotor as
the wind speed increases, thus reducing the wind force acting on
the rotor and controlling the rotor speed. Moreover, the airfoils
may be attached to the wind turbine rotor to regulate the
rotational speed of the wind turbine under differing wind
conditions.
[0031] The apparatus of this invention is fully functional for
generating electrical energy even in very high wind conditions.
Yet, the apparatus is capable of generating electrical energy even
at low wind speeds.
[0032] The above disclosure is sufficient to enable one of ordinary
skill in the art to practice the invention, and provides the best
mode of practicing the invention presently contemplated by the
inventor. While there is provided herein a full and complete
disclosure of exemplary embodiments of this invention, it is not
desired to limit the invention to the exact construction,
dimensional relationships, and operation shown and described.
Various modifications, alternative constructions, changes and
equivalents will readily occur to those skilled in the art and may
be employed, as suitable, without departing from the true spirit
and scope of the invention. Such changes might involve alternative
materials, components, structural arrangements, sizes, shapes,
forms, functions, operational features or the like.
* * * * *