Abstract:
An apparatus and system for counteracting wind gusts and other high load situations in a wind turbine includes the use of one or more gust counteracting devices configured to extend an air deflector outwardly from a surface of a turbine rotor blade. The air deflector may subsequently be retracted into the rotor blade once the wind gust has subsided or once the load falls below a certain threshold. Mechanisms for extending and retracting the air deflector may include pneumatic or hydraulic systems and/or electromechanical devices. Air deflectors are generally configured to normalize air flow around the rotor blade so that the risk of potential damage to components of the wind turbine is minimized. In one arrangement, the gust counteracting device may be located at a leading section of the turbine blade. Additionally or alternatively, the device may be modular in nature to facilitate the removal and replacement of the device.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to the design and control of a wind turbine. More specifically, the invention relates to modifying the aerodynamics of a wind turbine blade. 
       BACKGROUND 
       [0002]    Wind turbines create power proportional to the swept area of their blades. The choice of rotor attributes for a wind turbine, such as its diameter, is a design trade-off between longer blades for more energy production in low winds and shorter blades for load limitation in high winds. Thus, wind turbine having longer blades will increase the swept area, which in turn produces more power. However, at high wind speeds, a wind turbine having longer blades places greater demands on the components and creates more situations where the turbine must be shut down to avoid damaging components. Even in situations where the average wind speed is not high enough to cause damage, periodic wind gusts which change both the speed and direction of the wind, apply forces that may be strong enough to damage equipment. 
         [0003]    Approaches with varying levels of success have been attempted in achieving higher power, fewer shut downs, and less instances of damage to components. For example, pitch control has been used to vary the pitch of the blade (i.e., the angle of the blade). On a pitch controlled wind turbine, an electronic controller on the turbine checks the power output of the turbine. When the power output exceeds a certain threshold, the blade pitch mechanism turns the rotor blades to reduce the loads on the rotor blades. The blades are later turned back when the wind drops again. However, pitch control can be fairly slow to respond to changes in the wind and is relatively ineffective to loads imparted by sudden wind gusts. 
         [0004]    Stall control is another approach that has been used in an attempt to achieve higher power, and to reduce shut downs and damage to components. In passive-type stall controlled wind turbines, the rotor blades are mounted to the hub at a fixed angular orientation. The stall control is achieved passively by the shape of the blade being such that the blade goes into aerodynamic stall (destroying lift) when the wind speed exceeds a certain threshold. Active-type stall controlled wind turbines exist. In such systems, the rotor blades are adjusted in order to create stall along the blade. However, both types of stall control systems can be difficult to optimize and slow to respond, and may suffer from lower predictability of results than desired. These drawbacks are magnified in conditions with erratic winds and wind gusts. 
         [0005]    Variable length rotor blade systems have also been used as an attempt to achieve higher power, and experience fewer shut downs and less damage to components. In such systems, the wind turbine rotor blades are telescopic so that their length can be adjusted based on the wind speed. Such provides advantages in that the rotor blades can be extended to provide higher output in low wind conditions and retracted to lower loads in high wind conditions. U.S. Pat. No. 6,902,370 discloses a wind turbine system having telescoping wind turbine rotor blades. While variable length rotor blade systems have certain advantages, they may suffer drawbacks in erratic wind conditions or may be too slow to respond when experiencing a wind gust. 
         [0006]    As electricity continues to become a more valuable commodity, and as wind turbines present an environmentally-friendly solution to solve electricity shortage problems, a wind turbine design that overcomes the aforementioned drawbacks and provide increased power and decreased turbine shut downs and damage to components is thus desirable. 
       BRIEF SUMMARY 
       [0007]    The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to the more detailed description provided below. 
         [0008]    To overcome limitations in the prior art described above, and to overcome other limitations that will be apparent upon reading and understanding the present specification, the present invention is directed to a device and system for counteracting sudden increases in load or changes in operating environment such as when a gust suddenly increases the magnitude of the wind or changes the direction of the wind experienced by a wind turbine rotor. 
         [0009]    A first aspect of the invention provides a wind turbine including an airfoil rotor blade having an air deflector. The air deflector may be configured to extend from an exterior surface of the airfoil rotor blade when a change in load or wind gust magnitude or angle is detected. In this way, the air deflector acts to counteract such changes. In one arrangement, the air deflector may be located on a leading side of the airfoil rotor blade as defined by a leading edge and a trailing edge of the blade. For example, the leading edge and surface may correspond to an edge or surface of the airfoil rotor blade closest to an origin of the wind. The air deflector may further be moved to a retracted position in normal operating conditions (e.g., when a load is not excessive) such that the air deflector does not extend outwardly from the surface of the airfoil rotor blade. 
         [0010]    A second aspect of the invention provides a wind turbine including an airfoil rotor blade that is telescopically extendable and having at least one air deflector. To counteract excessive loads and other environmental factors, the airfoil rotor blade may be extended or retracted in conjunction with the extension or retraction of at least one air deflector. For example, when a sudden change occurs, the air deflector may be activated since the air deflector may be extended very quickly. For more gradual changes, extension or retraction of the blade may be used since quick compensation is not as critical. In other arrangements, the air deflector may be extended to further reduce loads in cases where the airfoil rotor blade has been retracted as much as possible. 
         [0011]    A third aspect of the invention provides a wind gust or load counteracting module connected to an airfoil blade. The counteracting module may include an air deflector, a controller for controlling the extension and retraction of the air deflector and a sensor configured to sense various conditions. In one or more configurations, an airfoil blade may include multiple counteracting modules, each including an air deflector, a controller and a sensor. Use of modules may facilitate the removal, insertion or replacement of air deflectors or other components associated therewith without having to modify the entire airfoil blade. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
           [0013]      FIG. 1  is a perspective view of a wind turbine according to a first embodiment of the invention. 
           [0014]      FIG. 2  is a cross-section through the rotor blade depicting a first wind gust counteracting device with the air deflector in an extended position. 
           [0015]      FIG. 3  is a cross-section through the rotor blade depicting a second wind gust counteracting device with the air deflector in an extended position. 
           [0016]      FIGS. 4 and 5  are an isometric sectional views through the rotor blade depicting the wind gust counteracting device of  FIG. 2  with the air deflector in a retracted position ( FIG. 4 ) and in an extended position ( FIG. 5 ). 
           [0017]      FIGS. 6 and 7  depict isometric views of an illustrative embodiment of a gust counteracting device, in isolation, with the air deflector shown in a retracted position ( FIG. 6 ) and in an extended position ( FIG. 7 ). 
           [0018]      FIG. 8  is a schematic cross section of a rotor blade showing an illustrative spacing arrangement for a series of gust counteracting devices. 
           [0019]      FIG. 9  is a schematic cross section of a longitudinally-telescopic rotor blade showing an illustrative spacing arrangement for a series of gust counteracting devices. 
           [0020]      FIG. 10  is a schematic sectional view of a rotor blade representing airflow under normal wind conditions. 
           [0021]      FIG. 11  is a schematic sectional view of a rotor blade representing airflow under a first gust condition. 
           [0022]      FIG. 12  is a schematic sectional view of a rotor blade representing airflow under a first gust condition schematically depicting a low pressure side air deflector in an extended position and the effect on air flow. 
           [0023]      FIG. 13  is a schematic sectional view of a rotor blade representing airflow under an alternative gust condition schematically depicting a high pressure side air deflector in an extended position and the effect on air flow. 
           [0024]      FIG. 14  is a graph depicting the lift and the drag on the rotor blades as a function of the angle of attack of the wind and the operational effects of the position of the air deflectors (deployed or retracted) on the high and low pressure sides of the rotor blades. 
           [0025]      FIG. 15  is a schematic control diagram depicting a locally-controlled embodiment of the gust counteracting device. 
           [0026]      FIG. 16  is a schematic control diagram depicting a centrally-controlled embodiment of the gust counteracting device. 
           [0027]      FIG. 17  is a schematic control diagram depicting a distributed control embodiment of the gust counteracting device. 
           [0028]      FIGS. 18   a  and  18   b  are schematic diagrams depicting a piston/cylinder arrangement for extending and retracting an air deflector according to one or more aspects described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    In the following description of the various embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. 
         [0030]    Aspects of the present invention are directed to a deployable device and combinations of its attributes that may be mounted to a rotor blade in various applications to quickly assist in counteracting wind gusts. In addition, aspects of the present invention are directed to a rotor blade having the deployable device, and to a wind turbine with a rotor blade having the deployable device. 
         [0031]      FIG. 1  shows a wind turbine  2  on a foundation  4  with a tower  6  supporting a nacelle  8 . One or more blades  10  are attached to a hub  12  via a bolt flange  14 . In the depicted embodiment, the wind turbine includes three blades  10 . The hub  12  is connected to a gear box, a generator, and other components within the nacelle  8 . The blades  10  may have a fixed length or may be of the variable length-type, i.e., telescopic, such as shown in  FIG. 1 . As shown in  FIG. 1 , each variable length blade  10  includes a root or base portion  16  and a tip portion  18 . The tip portion  18  is movable with respect to the root portion  16  so as to controllably increase and decrease the length of the rotor blade  10 , and in turn, respectively increase and decrease the swept area of the rotor blades  10 . Any desirable drive system, such as a screw drive, a piston/cylinder, or a pulley/winch arrangement may be used to move the tip portion  18  with respect to the root portion  16 . Such drive systems are described in U.S. Pat. No. 6,902,370, which is hereby incorporated by reference. The wind turbine  2  further includes a yaw drive and a yaw motor, not shown. 
         [0032]      FIGS. 2-5  show a cross section of a wind turbine blade  10  containing at least one gust counteracting device  30 . The blade  10  has a leading edge  20 , a trailing edge  22 , a high pressure side  24  and a low pressure side  26 . A chord line c can be defined as a line between the leading edge  20  and trailing edge  22  of the blade  10 . It is recognized that the leading side of the rotor blade  10  corresponds to the leading half of the rotor blade  10  and the trailing side of the rotor blade  10  to the trailing half of the rotor blade  10 . 
         [0033]    The blade  10  depicted in the figures is merely one illustrative cross-sectional design and it is recognized that infinite cross-sectional variations can be used as part of the present invention. The airfoil rotor blade may be made of any suitable construction and materials, such as fiberglass and/or carbon fiber. 
         [0034]    As can be seen in cross sections of  FIGS. 2 and 3 , the rotor blade  10  further includes at least one gust counteracting device, generically referenced to as reference number  30 , but specifically referred to as reference number  30   a  and  30   b  with reference to a specific side of the rotor blade  10 .  FIG. 2  depicts a placement of a first wind gust counteracting device  30   a  to affect the airflow on the low pressure side  26  of the rotor blade  10 .  FIG. 3  depicts a placement of a second wind gust counteracting device  30   b  to affect the airflow on the high pressure side  24  of the rotor blade  10 . It is recognized that in use, the more curved surface  26   a  and the opposing less curved surface  24   a  create the dynamics of the low pressure side  26  and the high pressure side  24  due to well known principles of aerodynamics. This, in combination with the airflow over the rotor blade  10 , creates an effect known as “lift” that assists in the rotation of the rotor. 
         [0035]    In one embodiment, each rotor blade  10  includes at least one first wind gust counteracting device  30   a  to affect the airflow on the low pressure side  26  and at least one second wind gust counteracting device  30   b  to affect the airflow on the high pressure side  24 . That is, it includes wind gust counteracting devices  30   a  and  30   b , and these devices  30   a ,  30   b  may be longitudinally spaced along the rotor blade  10 . Any desired number of these devices  30   a ,  30   b  may be used. In another embodiment, each rotor blade  10  includes at least one wind gust counteracting device  30   a  to affect the airflow on the low pressure side  26  and no wind gust counteracting devices on the high pressure side  24 . Any desired number of the devices  30   a  may be used on the low pressure side  26 . In yet another embodiment, each rotor blade  10  includes at least one wind gust counteracting device  30   b  on the high pressure side  24  and no wind gust counteracting devices on the low pressure side  26 . Any desired number of the devices  30   b  may be used on the high pressure side  24 . 
         [0036]    Each wind gust counteracting device  30   a ,  30   b  includes an air deflector  32 . The air deflector  32  is movable between an extended position in which the air deflector  32  extends from an exterior surface of the airfoil rotor blade  10  and a retracted position in which the air deflector  32  is substantially flush with, recessed, or otherwise does not materially extend from the exterior surface of the airfoil rotor blade  10 .  FIGS. 2 and 3  both show the air deflector  32  in an extended position wherein the air deflector  32  extends from the exterior surface of the rotor blade  10 .  FIG. 4  is an isometric sectional view through the rotor blade  10  depicting the wind gust counteracting device  30   a.    
         [0037]    In a first arrangement, the location of the air deflectors  32  with respect to the leading edge  20  and the trailing edge  22  of the airfoil rotor blade  26  is in the leading half, i.e., is between 0%-50% of the length of the chord c when measured perpendicularly thereto from the leading edge  20  to the trailing edge  22 . In another arrangement, the location of the air deflectors  32  with respect to the leading edge  20  and the trailing edge  22  of the airfoil rotor blade  26  is between 5%-25% of the length of the chord c when measured perpendicularly thereto from the leading edge  20  to the trailing edge  22 . In yet another arrangement, the location of the air deflectors  32  with respect to the leading edge  20  and the trailing edge  22  of the airfoil rotor blade  26  is between 5%-15% of the length of the chord c when measured perpendicularly thereto from the leading edge  20  to the trailing edge  22 . 
         [0038]    The air deflector  32  may be sized based on the desired wind turbine condition parameter and further in view of the number of gust counteracting devices used. The air deflector may be made from any suitable material, such as fiberglass, carbon fiber, stainless steel, and/or aluminum. The air deflector  32  may be of any desired width, for example from a few inches to a foot. Additionally, air deflector  32  may extend from the airfoil surface to any desired height, e.g., from less than a percent to a few percent of the chord c ( FIG. 3 ), and they may have any suitable thickness based on the material chosen, typically less than one inch. 
         [0039]      FIGS. 4 and 5  are isometric sectional views through the rotor blade  10  depicting the low pressure side wind gust counteracting device  30  with the air deflector  32  in a retracted position ( FIG. 4 ) and in an extended position ( FIG. 5 ). The wind gust counteracting device  30  is suitably mounted by an interface to substantially maintain the surface contour the rotor blade  10 . This may be accomplished by the use of one or more contoured cover plates  34  that fixedly attach to both the gust counteracting device  30  and the blade structure. Alternatively, the leading face of the wind gust counteracting device  30  may be suitably contoured and fixed to the blade structure. In another arrangement, the leading face of the wind gust counteracting device  30  may be mounted to the underside of the blade. Suitable fastening arrangements such as hardware and adhesives may be used. 
         [0040]      FIGS. 6 and 7  depict isometric views of an illustrative embodiment of a gust counteracting device  30 , in isolation, with the air deflector  32  shown in a retracted position ( FIG. 6 ) and in an extended position ( FIG. 7 ). In a first arrangement, the gust counteracting device  30  includes frame  33  made from first and second portions  34   a  and  34   b . The portions  34   a  and  34   b  interface so as to define a slot  35  in which the air deflector  32  travels. If desired, the facing edges of the first and second portions  34   a  and  34   b  include air exhausts  36 . Air exhausts  36  are generally used in pneumatic configurations (i.e., where the air deflector  32  is actuated by pressurized air) to release retained pressurized air, thereby allowing the air deflector  32  to return to an alternate position (e.g., retracted or extended). The operation of air exhausts like air exhausts  36  is discussed in further detail below with respect to  FIGS. 18   a  and  18   b.    
         [0041]    According to one aspect, gust counteracting device  30  may include guide notches (not shown) that act as a track for the air deflector  32 . For example, the lower portion of the air deflector  32  may include projections (not shown) that are sized, spaced, and shaped complimentary to the guide notches. The projections may then follow the track corresponding to the notches when the air deflector  32  is extended or retracted. Such an arrangement provides increased alignment and additional structural support. Any desired arrangement, such as screws and other hardware  38 , may be used to affix the first and second portions  34   a  and  34   b  of the gust counteracting device  30  together. If openings in the rotor blade  10  are accommodated to be the same size, the air deflector  30  and its separate modular characteristic, facilitate easy replacement from potential damage, such as if hit by lightning, or selected replacement for customization purposes. Additionally or alternatively, port  40  may be provided as a fluid conduit coupling, e.g., to connect to a pressurized air source via an air tube or the like. 
         [0042]    As described above, if more than one gust counteracting device  30  is used on each rotor blade  10 , they may be longitudinally spaced along the length of the rotor blade  10  as desired.  FIG. 8  depicts an illustrative spacing arrangement for a series of gust counteracting devices  30  with the air deflectors  32 .  FIG. 9  depicts a longitudinally-telescopic rotor blade  10  showing a series of longitudinally-spaced gust counteracting devices  30  with air deflectors  32  on both the base portion  16  of the rotor  10  and the tip portion  18  of the rotor  10 . For each arrangement, and based on space constraints within the rotor blade  10 , it may be desirable to longitudinally space the gust counteracting devices  30  at wider intervals so that they may alternate between locations on the high pressure side  24  ( FIG. 2 ) and the low pressure side  26  ( FIG. 2 ). 
         [0043]    The functionality of the gust counteracting device  30   a  and  30   b  is generally described herein with respect to  FIGS. 10-14 .  FIG. 10  shows a rotor blade  10  being subjected to airflow under normal wind conditions where the angle of attack of the wind, i.e., the angle between the chord line c and the direction of the relative wind, is within normal desired operating conditions. Such conditions are reflected in the graph of  FIG. 14  where the angle of attack is between the lines represented by α 1  and α 2 . In this range, the air deflectors would preferably remain in a retracted position as the wind conditions are achieving the desired lift with low drag. The boundary layer of the air flow on the low pressure side  26  is completely attached. Such may achieve desired operating results under normal wind conditions. 
         [0044]      FIG. 11  shows the rotor blade  10  being subjected to airflow under a gust condition that quickly increases the angle of attack of the wind in excess of α 1 . This creates increased lift and may exceed desired loads. As described above, this can damage components and force a shut down. The lift and drag characteristics on the rotor blade  10  under these conditions are shown on the graph in  FIG. 14  by the line segments to the right of α 1  containing point G 1 . 
         [0045]    Operation of the gust counteracting device  30   a  on the low pressure side  26  under these conditions counteracts the negative effects of such a gust. Such effects are shown in  FIG. 12 .  FIG. 12  depicts similar wind conditions relative to the rotor blade as shown in  FIG. 11 . In  FIG. 12 , the gust counteracting device  30   a  (e.g., the load control device) is deployed to move the air deflector  32  to the extended position. This induces upper flow separation adjacent or at a minimum closer to the leading edge  20 . This creates a significant increase in drag and a large reduction in lift. Since the gust counteracting device  30   a  can move the air deflector  32  from the retracted position to the extended position in a fraction of a second, the load on the rotor blade and the other components can likewise be reduced in a fraction of a second to better preserve the equipment and prevent failures. 
         [0046]    The lift and drag characteristics on the rotor blade  10  under these conditions are shown on the graph in  FIG. 14  by the line segments to the right of α 1  containing point G 2 . Specifically, the decrease in lift with the extended air deflector  32  is represented by the difference between the line segments to the right of α 1  containing point G 1  and G 2 , respectively. Additionally, the increase in drag with the extended air deflector  32  is represented by the difference between the line segments to the right of α 1  containing point G 2  and G 1 , respectively. When the angle of attack moves back into normal conditions, the air deflector  32  may be moved back into its retracted position. 
         [0047]      FIG. 13  is a schematic sectional view of a rotor blade representing airflow under an alternative gust or wind turbine rotor emergency stop conditions and schematically depicting a high pressure side air deflector  32  in an extended position and the effect on air flow. In the conditions as depicted in  FIG. 13 , the angle of attack has fallen below α 2  (see  FIG. 14 ). Without the deployment of the high pressure side air deflector  32 , the lift would continue to decrease as depicted in  FIG. 14 . 
         [0048]    However, when the air deflector  32  on the high pressure side is moved to an extended position, lower surface flow separation is immediately induced. This in turn, increases the drag, but has the effect of reducing the unwanted negative lift. The lift and drag characteristics on the rotor blade  10  under these conditions are shown on the graph in  FIG. 14  by the line segments to the left of α 2  containing point G 3 . This offset of the unwanted negative lift reduces the aerodynamic loads on the wind turbine during undesirable wind gust conditions or wind turbine rotor emergency stop conditions. When the angle of attack moves back into normal conditions, the air deflector  32  may be moved back into its retracted position. 
         [0049]    The air deflector  32  is beneficial under other gust conditions, such as a sudden increase in wind speed without a change in the angle of attack. By quickly moving the air deflector  32  from the retracted position to the extended position, on either or both the low pressure side  26  (as shown in  FIG. 2 ) or on the high pressure side  24 , it alters the shape of the rotor blade  10  around or near the leading edge  20 . This in turn drastically changes the lift and drag properties of the blade  10 . Thus, a strong wind gust that increases wind velocity and imparts an increased load on the equipment, can be counteracted in a fraction of a second by the deployment of one or more air deflectors  32 . Thus, it effectively acts as instantaneous increase of drag, akin to functioning as an air brake. 
         [0050]    Any desired drive may be used to move the wind gust counteracting devices  30  can move their respective the air deflector  32  between its extended and retracted position. In an illustrative arrangement in which a fluid such as air is used to control the movement of the air deflectors  32 , a centralized source of pressurized air is operatively coupled to a port of the wind gust counteracting devices  30  (e.g., port  40  of  FIGS. 6 and 7 ) via a conduit (e.g., conduit  58  of  FIG. 15 ). Within the wind gust counteracting devices  30 , an air pressure actuated solenoid or piston/cylinder and a valve is used to drive the air deflector  32  between its extended and retracted positions. A valve for controlling the flow of pressurized air, e.g., valve  73  of  FIGS. 18   a  and  18   b , may be electronically controlled if desired. In one arrangement, the signal to operate the valve and move the air deflector  32  travels via an optical fiber. If desired, a spring may be used to bias the air deflector  32  into either position as a fail safe. While some small amount of electricity may be needed to operate this system, and the power may be from a local source such as a battery or remotely from a conductive wire, this arrangement has advantageous attributes in that it minimizes power consumption and minimizes the likelihood of a lightning strike. It is recognized that alternative drive systems may be used. For example, a spring may be used to bias air deflector  32  into an extended position. To subsequently retract the air deflector  32 , a motor may be used. Other electromechanical mechanisms and systems may also be used. 
         [0051]      FIGS. 18   a  and  18   b  illustrate a piston/cylinder arrangement  76 / 78 , a valve  73  and a controller for extending and retracting an air deflector  79 . In the extended position shown in  FIG. 18   a , air deflector  79  (i.e., a top portion of piston  76 ) extends past a surface of the gust counteracting module in which the piston/cylinder arrangement  76 / 78  is housed and an exterior surface  81  of a corresponding airfoil rotor blade (not shown). Stoppers  77  are configured and placed to prevent air deflector  79  and piston  76  from extending past a certain point, thereby controlling an amount by which air deflector  79  may protrude from surface  81 . In  FIG. 18   b , the air deflector  79  is in a retracted position and stoppers  77  prevent piston  76  and deflector  79  from retracting past a certain point. In the retracted position, the top of air deflector  79  may be flush with an exterior surface  81  of the airfoil rotor blade. 
         [0052]    Controller  71  is configured to control valve  73  (e.g., a five way valve) to allow the flow of pressurized air into an upper chamber (i.e., a region above the base of the piston  76 ) or a lower chamber (i.e., a region below the base of the piston  76 ) of the cylinder  78 . By injecting pressurized air into the upper chamber, for example, the piston  76  may be forced down into a retracted position (as shown in  FIG. 18   b ). Injecting air into the lower chamber, on the other hand, forces the deflector  79  and piston  76  upward into an extended position (as shown in  FIG. 18   a ). In one arrangement, pressurized air may be retained in either the lower or the upper chamber to hold deflector  79  and piston  76  in a corresponding position. Accordingly, pressurized air does not need to be continuously injected into a particular chamber to hold the deflector  79  in a particular position in such an arrangement. To subsequently move deflector  79  and piston  76  from an extended to a retracted position, or vice versa, the pressurized air currently retained in either the lower or upper chamber may be evacuated from cylinder  78  through one or more air release valves  75  (or other air release mechanism) and further released from the gust counteracting module through exhaust channel  85 . According to one aspect, exhaust channel  85  may allow air to escape into the atmosphere. The air release valves  75  may be electronically controlled, e.g., by controller  71  and/or include mechanical control systems. 
         [0053]    The wind gust counteracting devices such as devices  30  may be activated based on readings from one or more of various sensors and/or controller that used sense values to determine whether predetermined thresholds have been exceeded or when an air deflector should be moved based on an algorithm. Such sensors can include one or more of the following: accelerometers, strain gauges, absolute and differential pressure gauges, wind vanes, and wind speed detectors. 
         [0054]    As can be seen in  FIG. 15 , the gust counteracting devices  30  may each be locally-controlled. According to this arrangement, each of gust counteracting devices  30  would have a controller  50  and one or more sensors  52  coupled to the controller  50 . Upon determining that a predetermined threshold has been exceeded (e.g., based on a reading from sensor  52 ), the controller  50  would send a signal to operate the valve  54  to control the flow of pressurized air and move the air deflector  32 . According to this arrangement, each of gust counteracting devices  30  may be coupled to a common pressurized air source  56  via a fluid conduit  58 . 
         [0055]    As can be seen in  FIG. 16 , the gust counteracting devices  30  may also be centrally-controlled. According to this arrangement, each gust counteracting device  30  would be functionally coupled to a common controller  60 . Controller  60  could send signals to individually or commonly control the gust counteracting devices  30 . Signals may be sent by controller  60  to each gust counteracting device  30  via an optical fiber  62  and/or other wired or wireless signaling mechanisms. Similar to the embodiment of  FIG. 15 , each of gust counteracting devices  30  may be coupled to a common pressurized air source  56  via a fluid conduit  58 . In this centrally-controlled embodiment, there is more flexibility to use additional sensors  52  such as sensors spaced from the gust counteracting device  30 . Additionally, the controller  60  may be coupled to the blade rotor drive system  64  to telescopically control the effective length of the rotor blades  10 . 
         [0056]    Additionally, in another arrangement, the gust counteracting devices  30  are controlled according to a system containing substantially the details of  FIGS. 15 and 16 . As illustrated in  FIG. 17 , the gust counteracting devices  30  may each be controlled in a distributed manner. According to this arrangement, each of gust counteracting devices  30  would have a local controller  50  and one or more sensors  52  coupled to the local controller  50 . Thus, each local controller  50  may independently control the extension and retraction of its corresponding deflector  32  based on detected conditions local to each controller  50 . Additionally, the local controllers  50  are coupled to a central controller  60 . Central controller  60  may send signals to the local controllers  50  to individually or commonly control the gust counteracting devices  30 . Each local controller  50  may further send signals to the central controller  60  to inform the central controller  60  of a status of each of the gust counteracting devices  30 . The collected status information may then be used by central controller  60  to determine an overall manner or scheme in which to control the local controllers  50  and deflectors  32  (e.g., to reduce load and/or optimize power capture). In this distributed control embodiment, there may also be flexibility to use additional sensors  52  such as sensors spaced from the gust counteracting device  30 . Additionally, the controller  60  may be coupled to the blade rotor drive system  64  to telescopically control the effective length of the rotor blades  10 . Such a distributed system may also provide redundancy. In each control arrangement, the controllers  50 ,  60  may be any desired or known control circuitry including but not limited to microprocessors. 
         [0057]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.