WO2006123951A1

WO2006123951A1 - A wind turbine

Info

Publication number: WO2006123951A1
Application number: PCT/NZ2006/000118
Authority: WO
Inventors: Leonard Charles Wicks
Original assignee: Leonard Charles Wicks
Priority date: 2005-05-18
Filing date: 2006-05-16
Publication date: 2006-11-23

Abstract

A wind turbine having a rotor (22) mounted within a housing (21), the rotor having blades (23) profiled and arranged so as to utilise both lift and drag effects during operation. The housing also includes airflow directing means (24, 25) to create a desired airflow within the housing (21), and is suitable for installation in residential or commercial buildings and may be mounted on roofs (29).

Description

A WIND TURBINE

Technical Field

This invention relates to the field of energy generation by a wind turbine.

Background

A wide range of wind turbine designs have been proposed. The earliest designs were drag type designs (i.e. the blade is pushed by the wind and creates resistance when advanced into the wind). The rotor of such designs rotates slowly and the blades slow the rotor as it advances into the wind.

Most modern designs utilise lift instead of drag. Whilst numerous wind turbine designs have been devised most commercial wind turbines are three blade horizontal axis wind turbines. The trend is towards larger turbines each capable of producing megawatts of power. Such turbines are expensive and require sophisticated engineering and power distribution systems. Accordingly, the trend is towards highly efficient, large and sophisticated wind turbines.

Some of the main issues affecting traditional wind power systems are:

• The high capital cost and maintenance costs of large wind turbines.

• The need to install electricity transmission lines from the place of generation to the place of power use.

• Lengthy and difficult resource management consent processes.

• Large turbines can adversely affect the visual amenity of landscapes.

• Wind turbines can affect the safety of air navigation.

• Traditional wind turbines can create adverse noise signatures. • Open bladed systems adversely affect birds and in the event of a blade separation, endanger people and nearby animals.

• Rotating blades and sunshine create an effect such as flicker vertigo, which can cause an adverse psychological reaction in people and livestock.

Notwithstanding the above problems, the main focus for reducing reliance on fossil fuels using wind energy has been on the creation of 'wind farms'. These normally have several large turbines on vertical towers, rotating about a horizontal axis to supply electricity users once the rotor blades are turned towards the prevailing wind.

Various designs for vertical axis wind turbines, such as Darrieus wind turbines, have been proposed. These turbines have vertically oriented elongate blades rotating about a vertical axis. The aerofoil cross-section of each blade is generally oriented tangentially to the cylinder of rotation.

JP 2002021705 discloses a roof mounted generator in which a plurality of drums drive a generator. The blades in the form of half drums are designed to be driven by drag. As there is no central void the generator is purely drag driven and lift effects are not possible.

US 4,174,923 discloses a dual paddle wheel type structure. The blades are relatively short and again utilise drag rather than lift effects. WO03091569 discloses are similar configuration.

US 5,332,354 discloses an arrangement utilising a large number of relatively short blades with a rather complex airflow guiding arrangement. The tight circular channel creates blockages and the turbine is drag driven within the channels. The whole assembly is rotatable, increasing costs and complexity. The blades have a thin chord providing limited lift. The turbine is a vertical axis machine and must yaw toward the prevailing wind direction.

Summary of Invention

It would be desirable to provide a wind turbine having the following features: • simple and robust design

• quiet operation

• capable of operating over a wide range of wind speeds

• economic power generation

• scalable design enabling the turbine to be used in small or large applications

• unobtrusive deployment allowing use of the turbine in urban areas

It is an object of invention to provide a wind turbine that provides at least some of the aforesaid features or at least provides the public with a useful choice.

According to one aspect of invention there is provided a wind turbine including:

a housing having an inlet and an outlet and an intermediate region allowing the passage of a fluid therebetween; and

an elongate rotor located within the intermediate region including a plurality of elongate blades rotatable about an axis of rotation transverse to the direction of fluid flow, each blade having an aerofoil cross-section wherein the major axis of each aerofoil is disposed generally radially with respect to the axis of rotation such as to utilise both lift and drag effects.

Another aspect of the invention provides a wind turbine including:

a. a housing having an inlet and an outlet and an intermediate region allowing the passage of a fluid therebetween;

b. a rotor located within the intermediate region including a plurality of blades rotatable about an axis of rotation transverse to the direction of fluid flow, each blade having an aerofoil cross-section wherein the major axis of each aerofoil is disposed generally radially with respect to the axis of rotation such as to utilise both lift and drag effects; and

c. adjustable airflow directing means for directing an incident airflow towards regions where the blades generate greatest lift. The enclosure may include a restricted region to accelerate airflow therethrough. The enclosure may include airflow directing devices to direct air into and out of the enclosure. Inlet louvers may be provided to direct incoming air from the retreating blade side of the rotor to the advancing blade side of the rotor. Inlet slats may be provided to reduce turbulence of airflow entering the housing. Outlet louvers may be provided to allow bidirectional operation.

Any desired number of blades may be utilised although between 3 to 8 blades is preferred. The blades may have a generally thick chord with one convex face and one slightly concave face.

Drawings

The invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a wind turbine according to a first embodiment;

Figure 2 shows a cross-sectional view of the wind turbine shown in figure 1 along the rotor shaft;

Figure 3 shows the various power zones of the blades of the turbine shown in figures 1 and 2;

Figure 4 shows the cross-section of a blade according to one embodiment;

Figures 5a to 5d show the wind flow over the blades in the various power zones;

Figure 6 shows a schematic cross-sectional view of a wind turbine according to a second embodiment;

Figure 7 shows a front view of the wind turbine shown in figure 6;

Figure 8 shows the wind turbine of figure 6 in use with the wind flow in a first direction; Figure 9 shows the wind turbine of figure 6 in use with the wind flow in the opposite direction to that shown in figure 8;

Figure 10 shows the wind turbine shown in figure 6 in a closed configuration;

Figure 11 shows a modified form of the wind turbine shown in figures 6 to 10 including constrictions near the inlet and outlet illustrating airflow in a first direction;

Figure 12 shows the wind turbine of figure 11 with the airflow in the opposition direction;

Figure 13 shows a perspective illustrative view of the wind turbine of figure 6 with the outer shroud removed; and

Figure 14 shows a perspective illustrative view of the wind turbine of figure 6 with the shroud and louvers.

Detailed Description

Referring to figures 1 and 2, a wind turbine according to one embodiment is seen to include a rotor 1 rotatably mounted about the axis of rotor shaft 2 within housing 3. The upper and lower walls 4 and 5 of housing 3 are seen to be convex so as to provide an intermediate region 6 having a restriction to accelerate airflow from an inlet 7 to an outlet 8. End walls are provided at each axial end (one of which is shown spaced apart from the housing in dashed line as 19) so that airflow is through inlet 7 and outlet 8 only.

Rotor 1 is located within intermediate region 6 and includes a plurality of elongate blades 9, which rotate rotor shaft 2. As shown in figure 4 a blade according to this embodiment has a relatively thick chord having a convex upper surface 10 and a concave lower surface 11. This allows the turbine to overcome inertial resistance in light winds, as with a Savonius Turbine. Although this profile has been found to work effectively it will be appreciated that other profiles may be employed depending upon the operational environment and turbine design parameters. It will be noted that blades 9 are spaced apart from rotor shaft 2 by shafts 12 so as to create a void region adjacent to the rotor shaft. This prevents blockage of air, which can prevent rotation at low wind speeds. Although four blades are shown in this embodiment other blade numbers may be successfully employed. Useful results have been achieved with between three and eight blades. The blades may be formed from a wide range of materials and processes including extrusion and moulding from metal, plastics, composites (e.g. fibre glass, carbon fibre) etc. The blades could also be arranged to spiral along the length of rotor 1 to provide improved balance.

At the inlet end 7 vertical slats 13 may be provided. Corresponding slats 14 are provided at the opposite end. These vertical slats minimise turbulence and assist airflow through the turbine.

One or more directional louver 15 may be provided to shield blades 9 as they advance towards louvers 15 and concentrate airflow towards blades 9 rotating away from louvers 15 and maintain non-turbulent airflow. Louvers 15 are pivotable about points 16, typically between a range of about 30 to 60° to the incident airflow, so that the incident airflow may be optimally directed as the incident wind speed changes. Control may be either by electronic or mechanical means. Electronic sensors may sense the direction and speed of the incident airflow and supply this information to a controller, which controls the angle of the louvers 15 via electromechanical means. Alternatively, an airflow surface may be connected to the louvers 15 via a suitable mechanical linkage to control their angle.

Louvers 17 are pivotable about points 18 and may be controlled in the same manner as louvers 15. When airflow through the turbine is from right to left louvers 17 are preferably maintained at an angle close to 0° (as shown) to ensure minimal resistance with the exiting airflow. When airflow through the turbine changes direction, louvers 15 and 17 exchange function (i.e. louvers 17 are typically at an angle of 30-60° and louvers 15 are at an angle close to or equal to 0°).

The general operation of the wind turbine will now be described with respect to figure 3 and figures 5a to 5d. From figure 3 it will be seen that the rotor has a windward power quarter (aerofoil lift up) where the rotor is predominantly driven by lift forces, a drag power quarter where the rotor is predominantly pushed by the incident wind, a leeward power quarter (aerofoil lift down) where the rotor is predominantly driven by lift forces and a non-power quarter where the rotor predominantly produces drag.

Figure 5a illustrates operation in the drag power quarter where the incident airflow is applied against the concave under surface of the blade to push it about the axis of rotor shaft 2. Figure 5b shows airflow in the windward power quarter where upwards lift is created by the airflow over the blade. Figure 5c shows airflow in the leeward power quarter where downwards lift is created by the airflow over the blade. Figure 5d shows airflow in the non-power quarter where the blade generates drag as it advances through the incident airflow.

It will be appreciated that directional louvers 15 reduce the incident airflow in the non-power quarter and enhance it in the other quarters. This enhances the venturi effect of the incident airflow for power generation and reduces drag. Vertical slats 13 and 14 reduce turbulence and improve utilisation of the incident airflow.

Rotor shaft 2 may drive any connected generator, pump etc 20 either directly or via a suitable transmission. Generators having a high number of poles may be directly driven to simplify the design and reduce frictional losses. Generators employing permanent magnet rotors or stators may be particularly suitable.

Referring now to figures 6 and 7 a second embodiment is shown. In this embodiment the housing or shroud 21 has a curved form which is larger at the left hand side than the right hand side adapted for mounting to a roof 29. The rotor 22 includes four blades 23 and inlet louvers 24 and outlet louvers 25. Blades 23 are secured via arms 30 to shaft 26. Shaft 26 has a bearing 27 at one end and a generator 28 at the other end.

Figure 8 illustrates louver positions and airflow within housing 21 when the incident airflow flows from right to left. It will be seen that the lower inlet louvers 24 direct incident airflow towards the centre of housing 21 whilst the upper louvers direct the incident airflow to a lesser extent. On the outlet side louvers 25 allow the airflow to follow its natural path substantially without direction by louver 25. As in the previous embodiments the louvers may be controlled via a mechanical control arrangement to a control surface or via an electromechanical control arrangement. Figure 9 shows airflow in the opposing direction in which the upper outlet louvers 25 direct the incident airflow towards the centre of housing 21 whilst the lower outlet louvers 25 allow the incident airflow to pass substantially without redirection. The inlet louvers 24 now allow the exiting airflow to pass substantially without redirection.

During high incident airflows or otherwise when it is desired to cease generation louvers 24 and 25 may be closed as shown in figure 10. This allows the turbine to be protected in extreme conditions.

Figure 11 shows a modified version of the turbine shown in figures 6 to 10 in which constrictions are formed in the inlet and outlet in the form of intruding walls 31 and 32. These walls perform the function of the louvers 24 and 25 in concentrating airflow towards the central region of enclosure 21 where the greatest lift effects can be obtained. It will be appreciated that louvers could be used in conjunction with this embodiment also. Figure 12 shows the embodiment of figure 11 when the incident wind flow is reversed.

Figure 13 shows an exposed view of the turbine with enclosure 21 removed. Figure 14 shows a perspective view of the turbine mounted to a roof with the enclosure and inlet louvers.

It is preferred that the blades have a relatively thick cord and that the trailing profile is concave and the leading profile of the blades is convex. Preferably the ratio of the inner radius of the trailing surface of each blade to the outer radius of the leading surface of each blade is between 120% to 400%, most preferably about 200%. The blades are also preferably rather elongate, such that the ratio of the length of each blade to its width is between 500% to 2000% and most preferably about 1200%. The width being the maximum blade width.

By providing a void in the middle of the rotor significant lift effects can be utilised. Providing sufficient spacing between the blades and the enclosure allows airflow which can prevent blocking.

Where the wind turbine drives an electrical generator it may be connected to the local electricity supply network so that the local generation may be injected into the grid when surplus power is generated. Alternatively, the generator may be connected to an alternative power supply. The wind turbine of the invention is thus a hybrid utilising both drag and lift techniques. The design allows a wind turbine to be provided in a compact, simple and environmentally acceptable enclosure. This will enable it to be utilised in locations where wind generation would not otherwise be feasible due to regulatory requirements etc.

The design is simple, economical and scalable (either by varying the size of each unit or using arrays of units) enabling it to be applied in both small-scale and large applications. The design has few moving parts and due to the rotor design the blades do not have to be produced to such exacting standards or use such expensive materials. The housing protects the rotor from weathering and ensures that the rotor is safely contained so as not to cause damage to humans or animals. The housing also mitigates visual and noise issues of the prior art.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept.

Claims

1. A wind turbine including:

a. a housing having an inlet and an outlet and an intermediate region allowing the passage of a fluid therebetween; and

b. an elongate rotor located within the intermediate region including a plurality of elongate blades rotatable about an axis of rotation transverse to the direction of fluid flow, each blade having an aerofoil cross-section wherein the major axis of each aerofoil is disposed generally radially with respect to the axis of rotation such as to utilise both lift and drag effects.

2. A turbine as claimed in claim 1 wherein the ratio of the length of each blade to its width is between 500% to 2000%.

3. A turbine as claimed in claim 1 wherein the ratio of the length of each blade to its width is about 1200%.

4. A turbine as claimed in any one of the preceding claims wherein the blades are generally symmetrical.

5. A turbine as claimed in any one of the preceding claims wherein the blades have a thick cord.

6. A turbine as claimed in any one of the preceding claims wherein the blades have a convex leading face and a concave trailing face.

7. A turbine as claimed in claim 6 wherein the ratio of the inner radius of the trailing surface of each blade to the outer radius of the leading surface of each blade is between 120% to 400%.

8. A turbine as claimed in claim 6 wherein the ratio of the inner radius of the trailing surface of each blade to the outer radius of the leading surface of each blade is about 200%.

9. A turbine as claimed in any preceding claim wherein the enclosure includes a restricted region to accelerate airflow.

10. A turbine as claimed in claim 9 wherein walls of the enclosure adjacent distal edges of the rotor blades are convex so as to form a restricted region within which the rotor rotates.

11. A turbine as claimed in any preceding claim wherein the enclosure is configured to concentrate airflow in regions where the blades utilise lift effects.

12. A turbine as claimed in claim 11 wherein the enclosure includes constrictions near the inlet and outlet to concentrate airflow.

13. A turbine as claimed in claim 12 wherein one constriction is provided at the top of the enclosure and the other is provided at the bottom of the enclosure.

14. A turbine as claimed in any one of the preceding claims wherein the enclosure is configured to be fixedly attached to a support structure.

15. A turbine as claimed in any one of the preceding claims including one or more airflow directing means at the inlet of the housing to direct the incoming air stream from the advancing blade side of the rotor to the retreating blade side of the rotor.

16. A turbine as claimed in claim 15 wherein the airflow directing means is one or more inlet louver.

17. A turbine as claimed in claim 16 wherein the airflow directing means includes multiple inlet louvers.

18. A turbine as claimed in claim 17 wherein the louvers are generally parallel to the axis of rotation of the rotor.

19. A turbine as claimed in any one of claims 16 to 18 wherein each inlet louver is adjustable between a position in which the airflow is substantially undirected to a position in which the inlet is closed by the louvers.

20. A turbine as claimed in any one of claims 16 to 18 wherein the one or more inlet louver is adjustable to an angle between 30 degrees to 60 degrees with respect to the axis of the airflow through the housing when the wind is incident at a speed sufficient to turn the turbine blades.

21. A turbine as claimed in any one of claims 16 to 20 wherein the angle of the one or more inlet louver is controlled via an air surface linked to the one or more inlet louver via a mechanical control arrangement.

22. A turbine as claimed in any one of claims 16 to 20 wherein the angle of the one or more inlet louver is controlled via an electromechanical control arrangement in response to inputs from one or more sensor for monitoring airflow.

23. A turbine as claimed in any one of the preceding claims including one or more airflow directing means at the outlet of the housing to direct the incoming air stream from the advancing blade side of the rotor to the retreating blade side of the rotor when the incident airflow enters through it.

24. A turbine as claimed in claim 23 wherein the airflow directing means is one or more outlet louver.

25. A turbine as claimed in claim 24 wherein the airflow directing means includes multiple outlet louvers.

26. A turbine as claimed in claim 25 wherein the louvers are generally parallel to the axis of rotation of the rotor.

27. A turbine as claimed in any one of claims 24 to 26 wherein each outlet louver is adjustable between a position in which the airflow is substantially undirected to a position in which the outlet is closed by the louvers.

28. A turbine as claimed in claim 24 wherein the one or more outlet louver is adjustable to an angle between 30 degrees to 60 degrees with respect to the axis of the airflow through the housing when the wind is incident at a speed sufficient to turn the turbine blades.

29. A turbine as claimed in any one of claims 24 to 28 wherein the angle of the one or more outlet louver is controlled via an air surface linked to the one or more louver via a mechanical control arrangement.

30. A turbine as claimed in any one of claims 24 to 28 wherein the angle of the one or more outlet louver is controlled via an electromechanical control arrangement in response to inputs from one or more sensor for monitoring airflow.

31. A turbine as claimed in any one of the preceding claims including a plurality of spaced apart slats at the inlet to reduce turbulent airflow.

32. A turbine as claimed in any one of the preceding claims including a plurality of spaced apart slats at the outlet to reduce turbulent airflow.

33. A turbine as claimed in any one of the preceding claims wherein the rotor has 8 blades or less.

34. A turbine as claimed in any one of the preceding claims wherein the rotor has three or more blades.

35. A turbine as claimed in any one of the preceding claims wherein the rotor has 4 blades.

36. A turbine as claimed in any one of the preceding claims wherein the blades are substantially parallel to the rotor axis of rotation.

37. A turbine as claimed in any one of the preceding claims wherein the aerofoil profile of the blades extends substantially radially from the axis of rotation of the rotor.

38. A turbine as claimed in any one of the preceding claims wherein the blades are spaced apart from the centre of the rotor to provide a fluid flow path through the centre of the rotor.

39. A turbine as claimed in any one of the preceding claims wherein the blades are spaced apart from the walls of the housing to provide a fluid flow path through therebetween.

40. A turbine as claimed in any one of the preceding claims including a generator driven by the rotor.

41. A wind turbine including: a. a housing having an inlet and an outlet and an intermediate region allowing the passage of a fluid therebetween; b. a rotor located within the intermediate region including a plurality of blades rotatable about an axis of rotation transverse to the direction of fluid flow, each blade having an aerofoil cross-section wherein the major axis of each aerofoil is disposed generally radially with respect to the axis of rotation such as to utilise both lift and drag effects; and

c. adjustable airflow directing means for directing an incident airflow towards regions where the blades generate greatest lift.