There is an increase in demand for alternate and renewable energy sources. Wind powered energy generators are becoming increasingly popular, since they harness the power of a renewable and freely available resource, the wind.
However, the wind is not a constant phenomenon. The wind may be light at times, even in areas that average heavy winds. Light winds may be insufficient to turn a wind turbine fast enough to generate a desired power output. Conversely, the wind may gust heavily at times in areas that average moderate or light winds. Heavy winds may turn a wind turbine too fast, causing mechanical damage to the turbine, or heavy winds may damage the wind turbine components (bend or break blades, push down the support tower, etc.). Additionally, the wind may vary from day to day or even hour to hour in some geographical areas, making wind inconsistent as a power source.
An electrical generator, for example, generally requires a constant speed of operation to produce electrical power that is safe and reliable. Since the wind can fluctuate between light, moderate, and heavy winds, often unpredictably, a generator that is driven by a wind turbine may not have a constant rotational speed. This may adversely affect the generator's ability to produce safe, reliable power at the desired output level. Fluctuating winds may produce power that is inconsistent in amplitude and/or phase, or tainted with surges or spikes. Such power may be unfit for most applications, or require extensive conditioning to be usable. Further, fluctuations in the rotational speed of a turbine may also damage mechanical or electrical components of the generator (such as with a sudden gust of high wind).
Many wind turbine implementations also depend upon a load being connected to an attached generator as a breaking force. When in moderate or higher winds, the turbine rotates with the power of the wind against the breaking force of the load (electrical and mechanical) from the generator. In lower winds, this type of turbine may not rotate because of the breaking force. Also, this type of wind turbine may run too fast if the load is suddenly diminished or disconnected (due to grid failure, mechanical failure, etc.), possibly destroying the wind turbine and/or the generator.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
Implementations of a self regulating wind turbine are described. Specifically, wind turbines that employ an automatic blade pitch adjustment and/or an automatic blade folding adjustment are disclosed.
In one aspect, a wind turbine is described as having a plurality of blades coupled to a hub, such that each blade has at least three degrees of freedom with respect to the hub. Each blade may be configured to rotate about a central axis of the hub, and may be extendable along an axis parallel to the length of the blade. In a further embodiment, each blade may also be configured to rotate about the axis parallel to the length of the blade.
In another aspect, a wind turbine is described as having a plurality of blades and an automatic blade folding adjustment. The automatic blade folding adjustment is configured to regulate a speed of the wind turbine such that the speed is substantially constant. The automatic blade folding adjustment is operative to fold the plurality of blades in unison in response to oncoming wind exceeding a threshold wind speed. In an embodiment of the aspect, the wind turbine also includes an automatic blade pitch adjustment.
In yet another aspect, a wind turbine is described as having a plurality of blades, a pitch control stage, and a blade folding stage. The pitch control stage and the blade folding stage may operate concurrently to regulate a speed of the wind turbine, such that the speed is substantially constant. The blades are configured to extend outward along an axis parallel to the blade and to rotate about the axis parallel to the blade. The pitch control stage is configured to automatically adjust a pitch angle of each blade based on centrifugal force. The pitch control stage is configured to adjust the pitch of each blade such that the surface of each blade exposed to oncoming wind increases with an increase in the oncoming wind.
The blade folding stage is configured to automatically fold each blade in unison, using at least three mechanical pivot points, based on having a tie rod coupled to each blade. The blade folding stage is configured to automatically fold the blades in response to a wind force applied to one or more of the blades. The blade folding stage may include magnets configured to control the folding of the blades.
While described individually, the foregoing aspects are not mutually exclusive and any number of the aspects may be present in combination in a given implementation.
The Detailed Description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like and/or corresponding aspects, features, and components.
An example wind turbine 100 is disclosed, as illustrated in
As illustrated in
In an example embodiment of the wind turbine 100, blades 106 are coupled to the hub 104, such that: (1) they fold with respect to the hub 104 and the shaft 102, and (2) each blade 106 rotates axially with respect to its attachment point to the hub 104, in addition to rotating as a group around the shaft 102 or the hub 104. In alternate embodiments, the blades 106 may be attached to another component (e.g., the shaft, an additional component, etc.). In a further embodiment, the blades 106 may fold with respect to another component (e.g., the tower support, the housing, the generator, etc.) or the blades 109 may rotate in another configuration (e.g., oblique rotation about another component such as a point on the hub.). In alternate embodiments, the blades 106 may either fold without rotation, or rotate without folding.
The example wind turbine 100 is also illustrated in
The wind turbine 100 maintains a substantially constant speed in various wind conditions primarily because the blade pitch may change and the blades 106 may fold in a progressive combination, operating together, under progressively changing wind conditions. In some instances, the pitch of the blades 106 may vary with changes in wind speed without the blades 106 folding, such as with a gradual or slight change in wind. In other instances, the blades 106 may fold independent of a blade pitch change, such as with a sudden gust of high wind. In example embodiments (as shown in
A self regulating wind turbine 100 according to this disclosure may include a number of additional or alternative features that contribute to the wind turbine's performance, such as, for example: (1) blades 106 that are linked together, so that they fold in unison, maintaining balance of the wind turbine 100; (2) multiple mechanical pivot points per blade assembly, designed for a predictable and reliable folding action; (3) linear bearings for smooth operation with minimal play; (4) blades 106 that pitch so that the flat portion of the blades 106 turn to face into the wind with an increase in wind speed, such that the surface area of the blades 106 exposed to the oncoming wind increases with an increase in wind speed; and/or (5) magnets employed to provide additional control to the folding action.
The following description refers to the drawings shown in
Referring to
In one example, composite or fiberglass blades 106 may be used. In other embodiments, the blades 106 may be constructed of other materials with desired weight and strength characteristics (e.g., aluminum, steel, fiberglass, composites, etc.). Three blades 106 may be used for a wind turbine 100, for example, as shown in the illustrations of
In one embodiment, as shown in the illustration of
In one example, as illustrated in
In one embodiment, as illustrated in
In one example, the blade pitch spring 202 governs the blade pitch by pulling on the rotating blade 106 through the blade pitch control shaft 212. The blade pitch spring 202 is illustrated as one or more coil springs; however, other devices may be employed as a blade pitch spring 202 (e.g., Belleville washers, torsion springs, etc.) including various combinations of the same. The blade pitch control shaft 212 is otherwise free to move linearly (a predetermined extent) back and forth through the blade support housing 206 (along an axis parallel to the length of the blade 106), and to rotate (a predetermined extent) within the blade support housing 206 (about the axis parallel to the length of the blade 106). As the rotating blades 106 increase in speed, each blade 106 has a tendency to move outward from the hub 104 (as shown in
Depending on the spring characteristics of the blade pitch spring 202, the blade pitch spring 202 may compress, allowing the blade pitch control shaft 212 to move linearly outward (away from the hub 104) through the blade support housing 206, as the blade 106 increases in speed. In one example, the blade pitch guide 204 and the blade pitch and RPM control slot 210 provide control to the movement of the blade pitch control shaft 212, and thus, the movement of the blade 106.
In an embodiment, the pitch of the blade 106 changes as the blade 106 moves outward away from the hub 104. This is due to the blade pitch control shaft 212 rotating within the blade support housing 206 as guided by the blade pitch guide 204 and the blade pitch and RPM control slot 210. As shown in
The shape of the blade pitch guide 204 and the blade pitch and RPM control slot 210 may vary in alternate embodiments, determining the pitching action of the blade as it extends and retracts with the blade pitch control shaft 212. In one embodiment, the shape of the blade pitch and RPM control slot 210 is generally “backslash-shaped.” In alternate embodiments, the shape of the blade pitch and RPM control slot 210 is generally “C-shaped,” “S-shaped,” or “L-shaped.” Further, other shapes of the blade pitch and RPM control slot 210 are contemplated, with each providing a different pitch control dynamic in conjunction with the blade pitch guide 204 and the blade pitch spring 202. Use of different blade pitch and RPM control slot 210 shapes to control pitch dynamics may enhance application of the wind turbine 100 in different climates or geographical areas. For example, one shape of blade pitch and RPM control slot 210 may provide a quicker pitch transition than another, or a more linear pitch transition than another.
The blade pitch and RPM control slot 210 determines a limit whereby each blade 106 may extend along the axis parallel to the length of the blade 106 and a limit whereby each blade 106 may rotate about the axis parallel to the length of the blade 106. The blade pitch guide 204 controls the pitch angle of each blade 106 based on the blade pitch control slot 210. The blade pitch guide 204 and the blade pitch and RPM control slot 210 may be constructed of hardened materials, for example hardened steel, for longevity and precise operation. In alternate embodiments, the blade pitch guide 204 and/or the blade pitch and RPM control slot 210 may incorporate bearings to facilitate smooth operation. The location or position of the blade pitch guide 204 and the blade pitch and RPM control slot 210 may vary with respect to the blade support housing 206 with alternate embodiments, while maintaining the overall pitch control and folding actions.
In one embodiment, as shown in
In one embodiment, as shown in
In one embodiment, as shown in
In one example, the tie rod 216 is coupled to the collar assembly 222 on one end, and the blade support housing 206 on the other end. The collar assembly 222 moves linearly inward (toward the hub 104) during folding of the blades 106. In one example, all blades 106 are coupled to the folding mechanism 214 through a tie rod 216, such that each of the blades 106 folds in unison. The shaft spring 218 compresses between the collar assembly 222 and the hub 104 during blade folding, resisting the folding action and attempting to move the blade folding mechanism 214 (including the collar assembly 222) to the unfolded rest position.
In an embodiment, as shown in
During folding, each blade assembly pivots at least in three places: (A) a collar assembly 222/tie rod 216 joint, (B) a blade support housing 206/tie rod 216 joint, and (C) a flange bearing 402 joint (as can be seen in
In one embodiment, as illustrated in
Additionally, as shown in
When the wind turbine 100 is at rest, or functioning under light or moderate winds (i.e., approximately 0 to 25 mph), the blades 106 are generally perpendicular to the shaft 102, as illustrated in
Based on the shape and size of the blades 106, the blades 106 rotate slowly with light wind, and rotate faster as the wind increases. For example, the blades 106 may begin to rotate with about 5 mph wind in some embodiments. In other embodiments, the blades 106 may begin to rotate with lesser or greater wind speeds. With moderate winds, the blades 106 will rotate with a substantially constant speed. In one example embodiment of a self regulating wind turbine 100, the blades 106 will rotate at a substantially constant speed of about 140-145 RPM with blades 106 that are about 12 feet long, are about 16 inches wide at their widest point, and have a pitch change of about 18 degrees from the widest part of the blade to the tip of the blade, when a wind of about 25 mph is present. In other examples, different substantially constant speeds and larger or smaller ranges of speeds may be used, depending on local wind speed averages, power generation requirements, blade configuration and materials, and the like. In other examples, blades 106 with a greater surface area may be used to generate more torque from less wind, which may result in rotation startup and/or faster rotation at lower wind speeds. A person having skill in the art will appreciate the effects of various wind conditions on start-up rotation, steady-state rotation speed, and the like, when one or more properties of the blades 106 is changed (e.g., materials, length, width, pitch change, etc.). Wind turbines having blades 106 with such various properties remain within the scope of the present disclosure.
Once the blades 106 are rotating at a substantially constant speed (again, based on their size and shape, etc.) they will continue to rotate at that speed with varying wind conditions, unless the wind drops below a sustainable level for more than a brief period of time. One embodiment of a self regulating wind turbine 100 is configured to maintain the substantially constant speed even in high wind conditions. For example, the blades 106 of the wind turbine 100 may rotate at a nearly constant 140-145 RPM in wind of about 25 to 100 mph wind or greater. This is due to the pitch control and folding actions described below. In alternate embodiments, the blades 106 may rotate at nearly constant speeds with lower or higher wind speeds.
When the velocity of blade rotation increases, generally due to an increase in wind, the mass of the blades 106 causes the blades 106 to tend to move outward (as shown in
In one embodiment, as the blade's pitch changes relative to the wind, the blade 106 becomes less efficient. In one example, the blade 106 may pitch up to about 26 degrees during its pitch change with increasing wind speed. This has the effect, for example, of positioning the widest portion of the blade at up to about zero degrees (or flat) into the oncoming wind.
To control pitch change, some blade pitch may be designed to occur with little outward travel of the blade 106. In one example, the linear travel of the blade pitch control shaft 212 within the blade support housing 206 during pitch change movement may be about ⅜ inch. In other embodiments, blade pitch may be designed to occur more gradually, using a longer linear travel of the blade 106, or designed to occur more rapidly, using a shorter linear travel.
In one example, the inner surface of the blade support housing 206 and the outer surface of the blade pitch control shaft 212 may be smooth. Further, as illustrated in the example of
In an alternate embodiment, the inner surface of the blade support housing 206 and the outer surface of the blade pitch control shaft 212 may be rifled to control the motion of the blade pitch control shaft 212 within the blade support housing 206. In a further embodiment, a torsion spring may be employed, where the torsion spring applies pressure to the blade pitch guide 204. For example, the torsion spring may control the operating point of the pitch control action. In alternate embodiments, as discussed above, the blade pitch and RPM control slot 210 may be generally “backslash-shaped,” “L-shaped,” “C-shaped,” “S-shaped,” or the like, creating other techniques of controlling the dynamic of the pitch control action (i.e., controlling the operating point, the pitch change transition action, delay, etc.).
As mentioned above, the combined effects of blade pitch change may consequently slow the rotation of the hub 104. As the velocity of rotation decreases, the centrifugal force on the blades 106 decreases, the blade pitch control shaft 212 is pulled back inward (toward the hub 104) by the blade pitch spring 202, and the pitch of the blade 106 reverses according to the blade pitch guide 204 as it follows the blade pitch and RPM control slot 210.
In addition to the pitch change action described above, the wind turbine 100 may include a blade folding action (as shown in
Referring to
In one example, as shown in
While less fold may be effective to maintain constant speed, in one example, the blades 106 may fold up to about 30 degrees from their rest position in high wind conditions. In other embodiments, the blades 106 may fold up to greater or lesser degrees in high wind conditions.
Referring to
In an alternate embodiment (not shown), the magnets 1002 are electromagnets. For example, the magnets 1002 may be controllable (e.g., to regulate energy generated, to avoid spikes to the grid, etc.) by a manually or automatically operated controller, to attract the collar assembly 222 to the outer collar assembly 1004 (extending the blades 106), to repel the collar assembly 222 from the outer collar assembly 1004 (folding the blades 106), or to be in a non-magnetic state (where extending/folding the blades 106 is a function of the shaft spring 218). In alternate embodiments, a controller for the magnets 1002 may be remotely located (e.g., at a remote utility site), or located locally for on-site control of blade folding and extension.
The two functional actions of blade pitch change and blade folding work together to govern the overall function of the wind turbine 100, and to allow it to operate at a substantially constant speed in varying wind conditions. At varying wind speeds, a measure of pitch change may occur and a measure of blade folding may occur, both acting concurrently, such that a substantially constant rotational velocity is maintained. The blade pitch and blade folding automatically adjust with changes in wind speed, as described above, to maintain the substantially constant speed under a wide range of wind conditions.
One benefit of the blade pitch change and blade folding actions is that it allows for a wider blade 106 to be used. A wider blade 106 is beneficial for lower start up speed, and more torque at lower speeds. The pitch and fold functions also allow the turbine 100 to function safely in high winds by changing the blade pitch to control RPMs and folding to decease wind load. Not only is the wind turbine 100 more efficient in low and high winds but its folding action also may extend the life of the generation system, as the blades 106, the tower 110, and the tower foundation may experience decreased stress by allowing the wind to be deflected off the folded blades 106. This may be the case when a sudden gust of wind blows the blades 106 into a folded position momentarily. During a sudden wind gust such as that, the blades 106 may fold without the blades 106 changing pitch. Such a sudden gust of wind may cause damage to blades (wider blades particularly) if they are used on a system without folding capability.
Further, since the wind turbine 100 is configured such that all of the blades 106 fold in unison, the balance of the turbine 100 may be greatly improved. A system where each blade may fold individually could produce an unbalanced rotation of the hub, causing premature wear or damage to the hub, shaft, generator, tower and/or foundation. A balanced rotation as is achieved by the wind turbine 100 may improve the top speed of rotation, and may also extend the life of the components.
The wind turbine 100 disclosed herein need not rely on a load to be connected to the generator device for a breaking force. The mechanical actions of the pitch control action and the blade folding action as described above allow the wind turbine 100 to maintain a constant safe speed, even without a load. In alternate embodiments, the pitch control action may operate independently of the folding action, the folding action may operate independently of the pitch control action, or the pitch control action and the folding action may act concurrently. Should the rotation of the wind turbine 100 rapidly increase for any reason, including grid failure, load failure, high winds, and the like, the pitch control action and/or the folding action will operate as discussed above to slow the rotation. This comprises an additional safety feature that may prevent the wind turbine 100 from self-destructing in the event of a grid failure, a load failure, high winds, or the like.
While various discreet embodiments have been described throughout, the individual features of the various embodiments may be combined to form other embodiments not specifically described. The embodiments formed by combining the features of described embodiments are also self regulating wind turbines 100.
This application claims the benefit under 35 U.S.C. §119(e)(1) of U.S. Provisional Application No. 61/308,683, filed Feb. 26, 2010, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61308683 | Feb 2010 | US |