WO2013059860A1

WO2013059860A1 - Wind turbine system

Info

Publication number: WO2013059860A1
Application number: PCT/AU2012/001288
Authority: WO
Inventors: Graeme Scott Attey
Original assignee: Design Licensing International Pty Ltd
Priority date: 2011-10-24
Filing date: 2012-10-23
Publication date: 2013-05-02

Abstract

A wind turbine system including a pair of wind turbines carried by a frame, wherein the frame is configured to be able to freely rotate about a central axis passing between the turbines. With this arrangement, the wind turbines are able to freely rotate about the central axis so as to automatically orient themselves to face the prevailing wind direction. To assist this response, the turbines may be configured to counter-rotate, and may be the same distance form the central axis. In a preferred form, the central axis is vertical and the two turbines are vertical axis wind turbines.

Description

WIND TURBINE SYSTEM

FIELD OF THE INVENTION

[0001 ] The present invention relates generally to wind turbines and in particular to small scale wind turbine systems suitable for use in urban environments.

BACKGROUND TO THE INVENTION

[0002] With increasing public awareness of climate change issues, generation of electricity from renewable resources, such as sun and wind energy, is increasing. However, widespread deployment of large scale, grid-connected wind turbines (generating electricity in the megawatt range) has met with a degree of public resistance in some countries, predominantly because of the visual impact on the environment of these inherently large structures. For this reason they are typically located away from urban environments, and often along coastal regions which experience favourable wind conditions. Various forms of small scale wind turbines (generating electricity in the hundreds of watts to several kilowatt range) have therefore been developed to enable smaller structures to be distributed in urban environments such as on individual buildings, factories or residential properties.

[0003] The present inventor has in the past developed small scale wind turbines suitable for use in urban environments and these turbines are sold under the brand Windpods™. The technology involved in those turbines is described in International Patent Application No. PCT/AU2007/001865 published as

WO2008/067593, as well as in International Patent Application No.

PCT/AU2009/000567 published as WO2009/135261 . The entire content of these PCT publications is incorporated herein by cross reference and form part of this disclosure. [0004] Broadly, these PCT publications disclose a vertical axis wind turbine apparatus comprising a rotor with a plurality of elongated turbine blades rotatably mounted about an axis. Each turbine blade extends generally parallel to the axis and has an aerofoil shaped profile. The apparatus also includes a pair of diametrically opposed wind barriers positioned adjacent a diameter of the rotor such that, when the prevailing wind direction is perpendicular to that diameter, the turbine blades and wind barriers are exposed to an open, unobstructed wind flow.

SUMMARY OF THE INVENTION

[0005] The inventor has discovered that if a pair of Windpods™ turbines is mounted on a frame which is able to freely rotate about a central axis passing between the turbines, the turbines tend to automatically orient themselves so as to face the prevailing wind direction. The present invention is based on this discovery. However, the invention is not limited to the use of Windpods™ turbines - other types of turbines could instead be used. For example, the individual turbines could be vertical axis wind turbines (VAWTs), as in the case of Windpods™ turbines, or could be horizontal axis wind turbines (HAWTs).

[0006] Accordingly, one aspect the present invention provides a wind turbine system including a pair of wind turbines carried by a frame, wherein the frame is configured to be able to freely rotate about a central axis passing between the turbines.

[0007] With this arrangement, the wind turbines are able to freely rotate about the central axis so as to automatically orient themselves to face the prevailing wind direction. To assist this response, the two wind turbines are preferably configured to counter-rotate. In other words, if one wind turbine spins clockwise then its partner turbine should spin anti-clockwise. This manner of operation serves to balance the wind turbine system and may achieve a more rapid and predictable response to changes in wind direction. [0008] For similar reasons, each wind turbine is preferably the same distance from the central axis. While it is not essential, a symmetrical arrangement produces a more balanced and uniform response to changes in wind direction.

[0009] In one embodiment, the central axis wind turbine system is vertical and each wind turbine is a vertical axis wind turbine (VAWT) arranged to rotate about a respective turbine axis parallel to the central axis. The VAWTs may be

Windpods™ turbines, as described above, but this is not essential.

[0010] In one embodiment, each turbine axis (of a pair of VAWTs) and the central axis lie in the same vertical plane. This is desirable so that the frame carrying the VAWTs balances the weight of the turbines about the central axis, and hence on any supporting structure. The two VAWTs may, however, instead be set back from the central axis such that, relative to a prevailing wind direction, the VAWTs are positioned slightly down wind from the central axis. This would then help to reorient the turbines with changes in wind direction.

[001 1 ] In one embodiment, each VAWT includes a rotor with a plurality of elongated turbine blades rotatably mounted about its turbine axis. Each turbine blade may extend generally parallel to the turbine axis and have an aerofoil shaped profile.

[0012] Each VAWT may also include a wind barrier positioned adjacent its rotor, in a manner similar to the wind barriers provided in Windpods™ turbines. The wind barrier may have an inner edge facing the rotor. This inner edge preferably lies within the vertical plane defined by the turbine axes and the central axis. Further, each VAWT may include a pair of diametrically opposed wind barriers positioned adjacent its rotor, once again in a manner similar to

Windpods™ turbines. The wind barriers may both have inner edges facing the rotor, and both inner edges may lie within the same vertical plane defined by the turbine axes and the central axis. [0013] Preferably the, or each, wind barrier includes a flat plate disposed within the vertical plane. The flat plate may be fixed to, or formed integrally with, the frame which supports the VAWTs. Preferably, each flat plate wind barrier extends the full length of the associated VAWT.

[0014] In one application of the wind turbine system, the frame is configured for mounting on a pole such that the central axis is coaxial with an axis of the pole. One example is a lighting pole, as might be used for street lighting. In this application, the wind turbine system may further include a collar shaped and sized to be fitted around the pole. A bearing system, possibly of a 'lazy Susan' style bearing system, may be provided to rotatably support the frame with respect to the collar.

[0015] In use, with the wind turbine system mounted on a pole, the turbine blades and wind barriers are exposed to an open, unobstructed wind flow. The wind turbine system is therefore free to rotate in response to changes in wind direction.

[0016] In an alternative embodiment, each wind turbine is a horizontal axis wind turbine (HAWT) which is arranged to rotate about a respective horizontal turbine axis perpendicular to a central vertical axis. Once again, the turbines are preferably arranged to counter-rotate and are preferably the same distance from the central axis. This arrangement produces a balanced operation and uniform response to changes in wind direction.

[0017] It will be convenient to hereinafter describe the invention with reference to the accompanying drawings which illustrate preferred embodiments thereof. Other embodiments of the invention are possible and, consequently, the particularity of the accompanying drawings is not to be understood as

superseding the generality of the preceding description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 shows a perspective view of the wind turbine system, in accordance with a preferred embodiment of the present invention, mounted upon a light pole.

[0019] Figure 2 shows a closer perspective view of the wind turbine system shown in Figure 1 .

[0020] Figure 3 shows another closer perspective view of the wind turbine system shown in Figures 1 and 2.

[0021 ] Figure 4 shows a top view of the wind turbine system shown in Figures 1 to 3.

[0022] Figures 5 and 6 show top views of the wind turbine system shown in Figure 4 with the wind approaching from alternative directions.

[0023] Figure 7 shows a front view of a portion of the wind turbine system shown in Figures 1 to 6.

[0024] Figure 8 shows a front view of a wind turbine system in accordance with an alternative embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Referring firstly to Figure 1 of the accompanying drawings, there is shown a wind turbine system 1 0 in accordance with a preferred embodiment of the present invention. In this embodiment, the wind turbine system 10 is mounted on a street lighting pole 12 of the type which is often seen along an urban roadway or a motorway. [0026] This is a primary example of a market application where the wind turbine system of the present invention is well suited. Street lighting in Australia consumes approximately 1 ,100 GWhr per year (1 ,100,000,000 kWhr/yr or 3,013,700 kWhr/day) resulting in emissions of approximately 880,000 tonnes of carbon dioxide, given that 78% of Australian electricity is presently generated by coal fired power stations (Source: Australian Institute of Traffic Planning

Management). Based on an average lighting power consumption of 1 kWhr/day this equates to approximately 3 million lighting poles in Australia alone in the height range of 10-14m. The wind turbine system of the invention can be made very low weight and have a minimal structural load on the pole so there is great potential to harvest energy from this market.

[0027] It should be understood however that the wind turbine system of the present invention is not limited to this example application and may instead be installed on other type of pole, or indeed any other type of structure.

[0028] Figure 2 of the drawings shows a closer view of the wind turbine system 10 and an upper portion of the street lighting pole 12. Figure 3 shows another closer view again, so that details of the wind turbine system 10 can more clearly be seen.

[0029] For convenience, the inventor has coined the phrase 'rotating wind turbine system', and hence the acronym 'RWTS', to refer to the concept embodied in the present invention. This acronym will therefore be used throughout the remainder of this description but it should be understood that the concept is not limited to the particular embodiments described or shown.

[0030] For example, Figures 1 -3 of the drawings, as well as Figures 4-7, show a particular implementation of the concept using Windpods™ vertical axis wind turbines, as disclosed in the abovementioned PCT publications WO2008/067593 and WO20091 35261 incorporated herein by reference. However, other types of vertical axis wind turbines (VAWTs) could be used, or horizontal axis wind turbines (HAWTs) could instead be used, for example as can be seen in the alternative embodiment shown in Figure 8.

[0031 ] Referring now to the embodiment shown in Figures 1 -3, the RWTS 10 includes a pair of Windpods™ turbines 14, having rotors 16, carried by a frame 18. The frame 18 is configured to be able to freely rotate about a central axis which is coaxial with a vertical pole section 20 of the street lighting pole 12. The street lighting pole 1 2 also includes an upper curved pole section 22 and a light 24.

[0032] In Figure 3 the wind direction is depicted by arrows 26 and the possible rotation path of the frame 18, and hence the RWTS 10, around the pole 20 is depicted by arrow 28. In use, the RWTS 10 is free to rotate in any direction about the pole 20.

[0033] To enable this free rotation of the RWTS 10 about the pole 20 a 'lazy Susan' style bearing system is positioned around the pole 20. One possible embodiment of such a bearing system is shown in Figure 7, this figure being a side view of the upper portion of the RWTS of Figures 1 -3. In this embodiment, a collar 30 is fixed to the pole 20 and a lazy Susan style bearing system 32 rotatably supports horizontal cross members 19 of the frame 18 on the collar 30. The cross members 1 9 of the frame 18, as well as the collar 30, generally need to encircle the vertical pole section 20 so as to assist in easy installation of the RWTS 10 on the street lighting pole 12. The collar 30 may be of a split design that consists of two halves which can be secured together around the pole 20. Likewise, the horizontal cross members 19 of the frame 18 may utilise a similar split-half principle. Alternatively, the cross members may be just half circle designs with alternating halves for each horizontal cross member 19. In the latter regard, it can be seen in the embodiment shown (see Figure 3 for example) that the frame 18 has three horizontal cross members 19. It is considered that there are many different ways to engineer the detail and alternative constructions would be readily apparent to a person skilled in the art. The important aspect, at least in this embodiment, is that the collars are secured to the poles such that the cross members of the frame can rotate around the static collars by means of simple, low cost bearings between the collars and the cross members.

[0034] In the detailed view shown in Figure 7, one can see that each of the Windpods™ turbines 14 includes a pair of diametrically opposed wind barriers 38 positioned adjacent its respective rotor 16. The wind barriers 38 take the form of flat plates which have inner edges facing the rotor 16 and outer edges fixed to inside surfaces of vertical frame members 17 of the frame 18. The plates may however be integrally formed as part of the vertical members 17. In any event, the plates lie in a vertical plane formed by the central axis of the pole 20 and the turbine axes of the Windpods™ turbines 14. These wind barriers 38 serve to improve the efficiency of the Windpods™ turbines 14, in the manner described in the above referenced PCT publications.

[0035] The inventor has discovered that a beneficial layout and operation of VAWTs, such as Windpods™ turbines, is to incorporate two identical units connected together around a central pole or axis as described above and shown in Figures 1 -7. The dual units 14 are free to rotate in unison via the lazy Susan style bearing system 32 positioned around the vertical pole section 20. Intuitively, it would be presumed that when the wind blows, the two turbines 14 would align with the wind direction 26 to minimise drag, in the same way a flag aligns with the wind. However, the RWTS design results in an unintuitive response. The pair of turbines 14 actually rotate in unison around the pole 20 so as to automatically face the wind direction 26, as can be seen in Figures 4-6. In other words, the turbines 14 self-align to maximise the energy return from the wind. Further, the higher the wind speed the faster the turbines spin, which in turn results in higher gyroscopic stability of the turbines, making for increasing stability of the RWTS in higher winds.

[0036] Traditionally, small scale wind turbines rely on tail fins to align with the wind. The RWTS of the present invention does not require tail fins. [0037] To ensure the system is balanced, the wind turbines 14 on each side of the pole 20 preferably rotate in opposite directions (that is, they are counter- rotating) as depicted by the arrows 36 in the top view of the RWTS 10 shown in Figure 4. It can be seen that the left hand turbine in this figure rotates clockwise whereas right hand turbine rotates anti-clockwise. This counter-rotation of the wind turbines 14 helps the RWTS 10 to automatically reorient itself with changes in wind direction. No tail fins are required.

[0038] In the latter regard, Figures 4-6 together show the manner in which the RWTS 10 naturally rotates around the pole 20 to automatically face the prevailing wind direction 26. For example, in Figure 5 the wind direction 26 has moved 30 degrees anti-clockwise from that shown in Figure 4. The RWTS 10 has accordingly also rotated 30 degrees anti-clockwise in natural orientation to the new wind direction. Similarly, Figure 6 shows the wind direction 26 having moved 45 degrees clockwise from that shown in Figure 4. In this instance, the RWTS 10 has accordingly also rotated 45 degrees clockwise in natural orientation to that new wind direction.

[0039] Finally, Figure 8 of the drawings shows an alternative embodiment of an RWTS in which horizontal axis wind turbines are used. In this embodiment, two horizontal axis wind turbines 40 are mounted either side of the pole 20 by a cross frame 18. These are held by two static pole mounting collars 30 with lazy Susan style circular bearing systems 32. The wind turbines 40 are configured to counter-rotate as shown by direction arrows 42.

[0040] Although preferred embodiments of the invention have been described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

CLAIMS:

1 . A wind turbine system including a pair of wind turbines carried by a frame, wherein the frame is configured to be able to freely rotate about a central axis passing between the turbines.

2. The wind turbine system of claim 1 wherein the wind turbines are configured to counter-rotate.

3. The wind turbine system of claim 2 wherein each wind turbine is the same distance from the central axis.

4. The wind turbine system of claim 3 wherein the central axis is vertical and each wind turbine is a vertical axis wind turbine (VAWT) arranged to rotate about a respective turbine axis parallel to the central axis.

5. The wind turbine system of claim 4 wherein each turbine axis and the central axis lie in the same vertical plane.

6. The wind turbine system of claim 5 wherein each VAWT includes a rotor with a plurality of elongated turbine blades rotatably mounted about its turbine axis.

7. The wind turbine system of claim 6 wherein each turbine blade extends generally parallel to the turbine axis and has an aerofoil shaped profile.

8. The wind turbine system of any one of claims 5 to 7 wherein each VAWT includes a wind barrier positioned adjacent its rotor, the wind barrier having an inner edge facing the rotor, with the inner edge lying within said vertical plane.

9. The wind turbine system of claim 8 wherein each VAWT includes a pair of diametrically opposed wind barriers positioned adjacent its rotor, the wind barriers having inner edges facing the rotor, with both inner edges lying within said vertical plane.

10. The wind turbine system of claim 8 or claim 9 wherein each wind barrier includes a flat plate disposed within said vertical plane, the flat plate being mounted to said frame.

1 1 . The wind turbine system of claim 8 or claim 9 wherein each wind barrier includes a flat plate disposed within said vertical plane, the flat plate being formed integrally with said frame.

12. The wind turbine system of any one of the preceding claims wherein the frame is configured for mounting on a pole such that said central axis is coaxial with an axis of the pole.

13. The wind turbine system of claim 12, further including: a collar shaped and sized to be fitted around the pole; and a bearing system adapted to rotatably support the frame with respect to the collar.

14. The wind turbine system of any one of claims 8 to 1 1 , or claim 12 or claim 13 when appended to any one of claims 8 to 1 1 , wherein, in use, the turbine blades and wind barriers are exposed to an open, unobstructed wind flow.

15. The wind turbine system of claim 3 wherein the central axis is vertical and each wind turbine is a horizontal axis wind turbine (HAWT) arranged to rotate about a respective horizontal turbine axis perpendicular to the central axis.