WO2011039717A2

WO2011039717A2 - A wind turbine

Info

Publication number: WO2011039717A2
Application number: PCT/IB2010/054402
Authority: WO
Inventors: Reginald Friedenthal
Original assignee: RURAL PROPERTY GENERATION SERVICES Pty Ltd
Current assignee: RURAL PROPERTY GENERATION SERVICES Pty Ltd
Priority date: 2009-09-29
Filing date: 2010-09-29
Publication date: 2011-04-07
Anticipated expiration: 2012-03-29
Also published as: WO2011039717A3

Abstract

The invention relates to a wind turbine. The turbine includes a rotor, having an operatively vertical rotor axis, and a plurality of vanes circumferentially spaced about the rotor axis and pivotally mounted to the rotor to pivot about a pivot axis parallel to the rotor axis, each between a closed position and a fully open position. The wind turbine includes displacement means for pivotally displacing the vanes into their closed positions above a threshold rotational speed of the wind turbine. Each vane defines two opposite ends at spaced apart positions on its pivot axis and arches outwardly between the ends to define a convex inner surface. In the closed position, the vanes, in combination, define a peripheral shell. Through pivotal displacement of the vanes towards their fully open positions, their inner surfaces are exposed for receiving wind thrust for exerting torque on the rotor for rotating it.

Description

A WIND TURBINE

THIS INVENTION relates to a wind turbine. According to a first aspect of the invention there is provided a wind turbine having a forward rotational direction and including:

a rotor for mounting with its rotor axis vertical;

a plurality of vanes circumferentially spaced about the rotor axis and pivotally mounted to the rotor to pivot about a pivot axis parallel to the rotor axis between a closed position and a fully open position relative to the rotor; and

displacement means for pivotally displacing the vanes into their closed positions above a threshold rotational speed of the wind turbine;

in which:

each vane defines two opposite ends at spaced apart positions on its pivot axis, the vane arching outwardly between the opposite ends to define a convex inner surface, for receiving wind thrust, and an opposite outer surface;

with each vane in its closed position, a trailing edge of the vane is disposed alongside a leading edge of the following vane so that the vanes, in combination, define a peripheral shell; and

through pivotal displacement of the vanes towards their fully open positions, their inner surfaces are exposed for receiving wind thrust for exerting torque on the rotor for rotating it.

The shell formed by the vanes, when in their closed positions, may define an outer surface which is roughly spheroidal in shape.

Alternatively, the outer surface of each vane may be shaped over at least a major portion of the operative height of the vane, including a mid-height portion, to intersect a plane perpendicular to the rotor axis along a straight line. The wind turbine may include an outwardly projecting lip along at least a part of the trailing edge of each vane for receiving wind thrust for exerting torque for rotating the rotor.

In a particular embodiment of the wind turbine of the invention, the displacement means may include at least one weight for effecting the pivotal displacement of the vanes into their closed positions under centrifugal effect. The said particular embodiment of the wind turbine may include, for each vane, a shaft to which the opposite ends of the vane are rotationally fixed, the shaft being pivotally displaceable with respect to the rotor to provide for the pivotal displacement of the vane between its closed and fully open positions. The at least one weight may include a weight for each vane and the displacement means may include, for each vane, a cantilever arm mounted to the corresponding shaft and carrying the corresponding weight at an end thereof remote from the shaft. In this case, with all the vanes in their fully open positions, the cantilever arm of each vane may overlap vertically with that of the previous cantilever arm for the sake of compactness of the cantilever arms and weights.

The displacement means may be positioned to be peripherally enclosed by the vanes when in their closed positions. As such, they will be shielded from potential damage by flying objects in high wind speed conditions. The pivotal axes of the respective vanes may be angularly equispaced about the rotor axis and equidistant from the rotor axis.

The wind turbine may include synchronization means for synchronizing pivotal displacement of the vanes.

The wind turbine may include biasing means biasing the vanes towards their fully open positions, the displacement means being configured operatively to progressively overcome the bias of the biasing means with increasing rotational speed to cause progressive pivotal displacement of the vanes towards their closed positions.

The wind turbine may include an upper disc at the top ends of the respective vanes and in this wind turbine, with the vanes in their closed positions, an aperture may be defined in between the top ends, the aperture being closed off by the upper disc. The upper disc thus serves to improve the aerodynamic properties of the wind turbine when the rotors are in their closed positions by closing off the aperture.

Similarly, the wind turbine may include a lower disc at the bottom ends of the respective vanes and in this wind turbine, with the vanes in their closed positions, an aperture may be defined in between the bottom ends, the aperture being closed off by the lower disc.

According to a second aspect of the invention there is provided a wind turbine apparatus including:

a wind turbine, in accordance with the first aspect of the invention; and a human operable override mechanism operable to displace the vanes into their closed positions irrespective of the rotational speed of the wind turbine.

The human operable override mechanism may be human powered.

The Applicant believes that the wind turbine of the invention may provide a number of benefits compared to at least some other types of wind turbines. These include low complexity of manufacture, low cost of manufacture, and low maintenance. The wind turbine is highly scalable according to requirements. The peripheral shell defined by the blades in their closed positions in high wind speed conditions provides certain benefits. The shell protects the internal mechanism of the wind turbine against flying objects. The shape of the shell is relatively aerodynamic so that lateral wind loads on the wind turbine and a support structure thereof are maintained relatively low in high wind speed conditions. The wind turbine further limits its own rotational speed to a safe value. Further features of the invention will become apparent from the description below of an example embodiment of a wind turbine apparatus, in accordance with the second aspect of the invention, including an embodiment of a wind turbine, in accordance with the first aspect of the invention, with reference to and as illustrated in the accompanying diagrammatic figures. In the figures:

Figure 1 shows a three-dimensional view of an embodiment of a wind turbine apparatus, in accordance with the second aspect of the invention, including a wind turbine, in accordance with the first aspect of the invention, in a first operative configuration thereof, with vanes of the wind turbine being shown in broken outline and inner parts of the wind turbine shown;

Figure 2 shows the same view as Figure 1 , but with the vanes being shown more clearly, in solid lines;

Figure 3 shows a three-dimensional view of the apparatus of Figure 1 , in a second operative configuration thereof;

Figure 4 shows a top view of the wind turbine of Figure 1 , in the second operative configuration;

Figure 5 shows a top view of the wind turbine of Figure 1 , in the second operative configuration;

Figure 6 shows a side/bottom three-dimensional view of the wind turbine apparatus of Figure 1 , particularly to show parts of a human operable override mechanism thereof; and

Figure 7 shows a top view of a further embodiment of a wind turbine, in accordance with the first aspect of the invention. In Figures 1 to 6, an embodiment of a wind turbine apparatus, in accordance with the second aspect of the invention, is designated generally by the reference numeral 10. The wind turbine apparatus 10 includes a wind turbine, in accordance with the first aspect of the invention, designated generally by the reference numeral 12.

The wind turbine 12 has a forward rotational direction 13. With reference initially to Figure 1 , the wind turbine 12 includes a rotor 14, in this example made predominantly of stainless steel, but which may be made of any suitable material or combination of materials. The rotor 14 includes:

a rotor shaft 16 defining a vertical rotor axis 18; and

an upper disc 20 and a lower disc 22, the discs being coaxial with and welded to the rotor shaft 16 at vertically spaced locations on the shaft 16.

The wind turbine 12 will typically serve to extract energy from wind for driving an apparatus, for example an electricity generator or a water pump. Such an apparatus may be driven from the shaft 16.

The wind turbine 12 further includes six vanes 24, shown in broken lines for clarity of the figure, and a shaft 26 for each vane, via which the vane is mounted to the upper disc 20 and the lower disc 22. The shafts 26 are parallel to the rotor axis 18 and each shaft 26 defines a pivot axis 28 for the corresponding vane 24. The shafts 26 are angularly equispaced about the rotor axis 18 and equidistant from the rotor axis 18.

Each shaft 26 is journalled near a top end thereof in a bearing assembly (not shown) mounted to the upper disc 20, with the top end extending through a hole defined through the upper disc 20 and projecting slightly above the upper disc 20. Similarly, each shaft 26 is journalled at or near a bottom end thereof in a bearing assembly 30 mounted to the lower disc 22. Each of the vanes 24 has a top end 32 which is fixedly mounted to the top end of the corresponding shaft 26 slightly above the upper disc 20 and a bottom end which is fixedly mounted to the shaft 26 slightly above the lower disc 22.

Each vane 24 is symmetrically about an equatorial plane of the wind turbine 12 and its top end 32 and bottom end are mirror images of each other. The bottom ends are not shown, but the location of one bottom end is indicated in Figure 3 by an arrow 34. The bottom ends will henceforth be referred to by the reference numeral 34. Each vane 24 arches outwardly between its top end 32 and its bottom end 34 to define a concave inner surface 36 and a convex outer surface 38. Each vane 24 defines along a middle portion of the trailing edge 40 thereof a lip 42, which projects slightly outwardly and in the trailing direction from the edge 40.

Each of the vanes 24 is pivotable relative to the rotor 14 between a closed position, shown in Figures 3 and 4, and a fully open position, as shown in Figures 1 , 2, and 5, through intermediate positions. The fully open positions are defined by suitable stop means 41 (see Figure 6), which may be essentially conventional and which prevents pivoting of the vanes 24 beyond that position.

With reference particularly to Figure 4, in the configuration of the wind turbine 12 in which all the vanes 24 are in their closed positions, an aperture 43 is defined between the top ends 32 of the respective vanes 24. This aperture is closed off by the upper disc 20. Similarly, the lower disc 22 closes an aperture defined between the bottom ends 34 of the respective vanes 24. The upper disc 20 and the lower disc 22 thereby enhance the aerodynamic properties of the wind turbine 12 in this configuration. With reference again particularly to Figure 1 , the wind turbine 12 includes synchronization means including a pulley 44 mounted on each shaft 26 and a cable 46 engaged with and extending around all the pulleys 44. The cable 46 is secured to each pulley 44 by means of a suitable fastener 47, for example a bolt screwed into a screw threaded passage in the pulley and clamping the cable against the pulley. The synchronization means ensures that pivotal displacement of the vanes 24 relative to the rotor 14 is synchronized, i.e. that the relative pivotal positions of the respective vanes 24 are always the same.

The wind turbine 12 includes also displacement means including a cantilever arm 48 mounted to the shaft 26 of each vane 24 and a weight 50 mounted to a free end of each cantilever arm 48. The cantilever arm 48 of each vane 24 is vertically overlapped with the cantilever arm 48 of the previous vane 48 so that the weight 50 carried by the former cantilever arm is partially above the latter cantilever arm. This arrangement of the cantilever arms 48 and weights 50 has the benefit of being particularly compact.

During rotation of the wind turbine 12, each weight 50 is urged outwardly under centrifugal effect and urges the cantilever arm 48 to which it is mounted to pivot outwardly relative to the rotor 14 in the direction opposite to the forward rotational direction 13. The cantilever arm 48 therefore exerts torque on the shaft 26 to which it is mounted. This torque is in a direction corresponding to pivoting of the corresponding vane 24 towards its closed position.

With reference particularly to Figure 6, the wind turbine 12 includes also two levers 52 mounted to respective extended bottom ends of two of the shafts 26 in a T- configuration and a coil spring 54 for each lever, interconnecting one end of the lever 52 to the lower disc 22. As will now be described, the coil springs 54 serve as biasing means for biasing the vanes 24 towards their fully open positions.

Each spring 54 acts on the corresponding lever 52 to bias it to pivot in the forward rotational direction 13 relative to the rotor 14. The lever 52 therefore exerts torque on the shaft 26 to which it is mounted. Such torque on the two shafts 26 to which the levers 52 are mounted is distributed roughly evenly to all the shafts 26 by the pulleys 44 and the cable 46. This torque is in a direction corresponding to pivoting of the vanes 24 towards their fully open position.

In summary, the springs 54 bias the vanes 24 towards their fully open positions, whereas, during rotation of the wind turbine 12, the weights 50 bias them towards their closed positions.

The operation of the wind turbine 12 will now be described for different wind conditions, with reference to Figures 1 to 6 generally.

In windless conditions, the wind turbine 12 will be in the configuration as shown in Figures 1 , 2, and 5, in which all the vanes 24 are in their fully open positions under bias of the coil springs 54. As a wind arises, acting on the wind turbine 12 from any side, it will initially effect thrust on the inner surface 36 of at least one of the vanes 24 and some of the outer surfaces 38. Due to the configuration of the vanes 24, such thrust will be unbalanced so that a torque will be exerted on the wind turbine 12, in the forward rotational direction 13. If the wind is sufficiently strong to overcome resistance, the wind turbine 12 will be caused to rotate in the forward rotational direction 13. Wind thrust will act on the inner surface 36 of each vane 24 whilst the vane sweeps through a particular angular range during each rotation of the wind turbine 12.

During rotation of the wind turbine 12, each of the vanes 24 will experience a number of effects which will bias it to pivot relative to the rotor 14. These include the bias of the springs 54, biasing it to pivot towards the fully open position, centrifugal effect of the weight of the vane itself, wind action, and the bias of the associated weight 50, biasing it to pivot towards the closed position.

With increasing rotational speed of the wind turbine 12 due to increasing wind speed, the bias of the weights 50 will progressively overcome the other effects and cause progressive pivotal displacement of the vanes 24 towards their closed positions.

Above a certain threshold rotational speed of the wind turbine 12, the vanes 24 will be pivotally displaced into their closed positions, as shown in Figures 3 and 4. In this configuration, the torque effect of the wind on the wind turbine 12 is substantially limited to torque resulting from thrust of the wind on the lips 42 of the respective vanes 24. As such, the maximum rotational speed of the wind turbine 12 is limited to a predetermined, safe speed.

With the vanes 24 in their closed positions, as shown in Figures 3 and 4, the trailing edge 40 of each vane 24 is alongside the leading edge of the following vane 24. More particularly, the trailing edge 40 of each vane 24 is overlapped (see Figure 4) with the leading edge of the following vane 24. As such, the vanes 24 define a peripheral shell 57 of the wind turbine 12. All internal parts of the wind turbine 12 are shielded by the shell 57 from damage by any flying objects. The lip 42 of each vane 24 projects outwardly from the shell 57.

The shell 57 has an outer surface which is substantially spheroidal in shape and is therefore relatively aerodynamic. As such, winds of high speed do not impose excessive lateral loads on the wind turbine 12 and any supporting structure. It will be noted that the vanes 24 are essentially segments of a spheroid.

In designing and constructing the wind turbine 10, a major aim would be to obtain a proper balance between the bias of the weight 50 and the springs 54 to optimize the speed and torque characteristics of the wind turbine 12 for different wind conditions whilst limiting the rotational speed to a safe value. Similar considerations will apply in designing and constructing other wind turbines, in accordance with the first aspect of the invention.

With reference to Figure 6, the wind turbine assembly 10 includes, in addition to the wind turbine 12, also a human operable override mechanism for displacing the vanes 24 into their closed positions irrespective of the rotational speed of the wind turbine 10. The override mechanism includes:

cables 58 attached to respective ends of the levers 52, in each case the end opposite to that to which the corresponding coil spring 54 is attached;

a pulley 60 for each cable 58, over which the cable is bent downwardly;

a bearing assembly 62, which is slidable along a square cross-sectioned part of the shaft 16;

two cables 66 connected to and extending downwardly from the bearing assembly 62; and

a manually operated winch (not shown) to which bottom ends of the respective cables 66 are connected and by means of which the cables 66 can be partially winched in.

The bearing assembly 62 includes an inner bearing part 68, which turns with the shaft 16, and a rotationally stationary outer bearing part 70, to which the cables 66 are connected. By manually operating the winch to winch in bottom lengths of the cables 66, the levers 52 are pivotally displaced by the respective cables 58 acting on them to pivotally displace the respective shafts 26 on which the levers 52 are mounted against the bias of the springs 54. Such pivotal displacement is transferred to the other shafts 26 via the pulleys 44 and cable 46. Accordingly, by such winching, all of the vanes 24 may be displaced into their closed positions, as shown in Figures 3 and 4, irrespective of the rotational speed of the wind turbine 12. The effect of wind on the wind turbine 12 is thus minimized, facilitating braking of the wind turbine 12, for example by applying a braking force to the shaft 16 by conventional braking means. Such conventional braking means may, for example, include a disc brake (not shown) mounted to the shaft 16.

In Figure 7, a second embodiment of a wind turbine, in accordance with the invention, is designated generally by the reference numeral 74.

The wind turbine 74 includes many features that are similar or identical to features of the wind turbine 10 of Figures 1 to 6. Where corresponding features are designated, they are again designated by the same reference numerals as before and a description of these features is not repeated here.

More particularly, the wind turbine 74 differs from the wind turbine 10 only in respect of the shape of the vanes 24, the difference being that in the wind turbine 74 the outer surface 38 of each vane 24 is shaped over substantially its entire height to intersect a plane perpendicular to the rotor axis along a straight line. The lips 42 of the respective vanes 24 project slightly inwardly and in the trailing direction so as to reduce wind trust on a trailing edge of each of the vanes 24 which projects past the leading edge of the following vane 24 when the vanes 24 are in their closed positions.

Claims

1 . A wind turbine having a forward rotational direction and including:

a rotor for mounting with its rotor axis vertical;

in which:

2. A wind turbine as claimed in claim 1 , in which the shell formed by the vanes, when in their closed positions, defines an outer surface which is roughly spheroidal in shape.

3. A wind turbine as claimed in claim 1 , in which the outer surface of each vane is shaped over at least a major portion of the operative height of the vane, including a mid-height portion, to intersect a plane perpendicular to the rotor axis along a straight line.

4. A wind turbine as claimed in any of the preceding claims, which includes an outwardly projecting lip along at least a part of the trailing edge of each vane for receiving wind thrust for exerting torque for rotating the rotor.

5. A wind turbine as claimed in any of the preceding claims, in which the displacement means includes at least one weight for effecting the pivotal displacement of the vanes into their closed positions under centrifugal effect.

6. A wind turbine as claimed in claim 5, which includes, for each vane, a shaft to which the opposite ends of the vane are rotationally fixed, the shaft being pivotally displaceable with respect to the rotor to provide for the pivotal displacement of the vane between its closed and fully open positions, and in which:

the at least one weight includes a weight for each vane; and the displacement means includes, for each vane, a cantilever arm mounted to the corresponding shaft and carrying the corresponding weight at an end thereof remote from the shaft.

7. A wind turbine as claimed in claim 6, in which, with all the vanes in their fully open positions, the cantilever arm of each vane overlaps vertically with that of the previous cantilever arm.

8. A wind turbine as claimed in any of the preceding claims, in which the displacement means is positioned to be peripherally enclosed by the vanes when in their closed positions.

9. A wind turbine as claimed in any of the preceding claims, in which the pivotal axes of the respective vanes are angularly equispaced about the rotor axis and equidistant from the rotor axis.

10. A wind turbine as claimed in any of the preceding claims, which includes synchronization means for synchronizing pivotal displacement of the vanes.

1 1 . A wind turbine as claimed in any of the preceding claims, which includes biasing means biasing the vanes towards their fully open positions, the displacement means being configured operatively to progressively overcome the bias of the biasing means with increasing rotational speed to cause progressive pivotal displacement of the vanes towards their closed positions.

A wind turbine as claimed in any of the preceding claims, which includes an upper disc at the top ends of the respective vanes and in which, with the vanes in their closed positions, an aperture is defined in between the top ends, the aperture being closed off by the upper disc.

A wind turbine as claimed in any of the preceding claims, which includes a lower disc at the bottom ends of the respective vanes and in which, with the vanes in their closed positions, an aperture is defined in between the bottom ends, the aperture being closed off by the lower disc.

A wind turbine apparatus including:

a wind turbine as claimed in any of the preceding claims; and

a human operable override mechanism operable to displace the vanes into their closed positions irrespective of the rotational speed of the wind turbine.

15. A wind turbine apparatus as claimed in claim 14, in which the human operable override mechanism is human powered.