WO2008053134A1

WO2008053134A1 - Wind generator

Info

Publication number: WO2008053134A1
Application number: PCT/GB2007/003139
Authority: WO
Inventors: Peter Frederick Wilde
Original assignee: Claire Alice Imogen Price
Priority date: 2006-11-02
Filing date: 2007-08-17
Publication date: 2008-05-08
Also published as: GB0622409D0

Abstract

A vertical axis wind generator (10) comprising at least two sails (12a,b) mounted on opposite sides of a support column (22) or (26) for rotation about a vertical axis (16) by wind blowing in a wind direction perpendicular to said axis. The sails (12a,b) each have a windward side and a leeward side and are each rotatable about a sail axis inclined to said vertical axis (16) between stops (20, 259 or (34) and (34') on said column (22) or (26) defining for each sail (12a,b) a driving position, in which the windward side is substantially parallel said vertical axis (16), and a low-resistance position, in which said windward side is substantially parallel said wind direction. When the wind impacts the windward side of a said sail (12a,b) it tends to rotate the sail (12a,b) towards said driving position whereas when the wind impacts the leeward side it tends to rotate the sail (12a,b) towards said low-resistance position. The generator (10) has two sides with respect to the wind separated by said vertical axis (16), said sides being a driven side on which the sails are urged towards their driving position and in which they offer maximum resistance to the wind and a return side on which the sails are urged towards their low-resistance position and in which they offer minimum resistance to the wind. The sails (12a,b) are inter-connected so that, when a said sail (12a) is rotated into its driving position, the other sail (12b) is correspondingly rotated into its low-resistance position.

Description

Wind Generator

This invention relates to a wind generator, and in particular to a vertical axis Savonius- type wind generator, especially used for the conversion of wind energy into electricity.

BACKGROUND

Wind generators are devices that convert the kinetic energy of the wind into mechanical energy, which is then generally converted into electricity. Wind generators can be divided into two categories: horizontal axis wind generators (HAWGs) with horizontal main rotor shafts, and vertical axis wind generators (VAWGs) with vertical main rotor shafts. Typically, HAWGs require an additional degree of freedom so that the main rotor shaft can be oriented to point into the wind. VAWGs however, can generally operate independent of wind direction without the need to be reoriented, thus allowing them to be constructed with fewer bearings compared to HAWGs. The electricity generator of a horizontal axis unit is generally located close to the main rotor shaft, which is usually high above the ground supported by a tower or pole. Servicing or adjusting generators of this kind can therefore prove difficult. VAWGs have a distinct advantage over HAWGs in that the electricity generator can be located on the ground at the base of the main rotor shaft, allowing easy access for servicing and adjusting. Furthermore, locating the heavy generator on the ground means that it does not need to be supported by any tower or pole employed, which thus allows for longer, thinner supporting structures for the rotor mechanism.

In its basic form, a VAWG comprises large sail blades that rotate, converting the kinetic energy of the wind into a torque about the main rotor shaft. In this scenario, more torque will be produced by blades with a large surface area. However a resistive force, proportional to the blade area, will also be experienced by the blade returning into the wind. A Savonius wind generator is a type of VAWG^' that comprises scooped blades where a concave blade is pushed downwind due to the force applied by the wind, causing a convex blade on the opposite side to move upwind.

US 2004/0018087 discloses a VAWG in which flexible sails change position reducing the wind resistance of their return into the wind. DE 10032674 discloses a VAWG in which rotor blades are turned into the wind to reduce resistance. The turning is effected by a track and rollers following the track. RU 2013648 discloses a VAWG in which vertically draped sails are connected to one another by springs whereby, in one direction the springs prevent the sails from rotating out of the wind whereas in the other direction they do not. RU 2006668 discloses a VAWG in which sails are either vertical or flap to a horizontal position against the wind, stops being employed to prevent rotation when it is not desired.

NL 9201771 discloses a VAWG in which a gear mechanism is employed to turn the sails so that they offer little resistance when against the wind.

NL 9001343 discloses a VAWG consisting of flat sails each having a roller that follows a track, turning the sails out of the wind when against the wind. DE 3714478 discloses a VAWG whereby a track causes a multi-array of sails to turn out of the wind.

Like the prior art cited above, the objective of the present invention is to improve on the basic design of the VAWG to maximize wind energy-to-torque conversion whilst minimizing the effects of drag on the returning blades.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with the present invention there is provided a vertical axis wind generator comprising at least two sails mounted on opposite sides of a support column for rotation about a vertical axis by wind blowing in a wind direction perpendicular to said axis, wherein said sails each have a windward side and a leeward side and are each rotatable about a sail axis inclined to said vertical axis between stops on said column defining for each sail a driving position, in which the windward side is substantially parallel said vertical axis, and a low-resistance position, in which said windward side is substantially parallel said wind direction, wherein, when the wind impacts the windward side of a said sail it tends to rotate the sail towards said driving position whereas when the wind impacts the leeward side it tends to rotate the sail towards said low-resistance position, whereby the generator has two sides with respect to the wind separated by said vertical axis, said sides being a driven side on which the sails are urged towards their driving position and in which they offer maximum resistance to the wind and a return side on which the sails are urged towards their low-resistance position and in which they offer minimum resistance to the wind, characterised in that the sails are inter-connected so that, when a said sail is rotated into its driving position, the other sail is correspondingly rotated into its low-resistance position. Preferably said inclination is perpendicular. Said wind generator may comprise multiple pairs of sails. In a preferred embodiment, the sails of each said pair are oriented perpendicularly with respect to one another, where preferably the sails of each said pairs are attached by a single sail axle each sharing the same sail axis. In one preferred embodiment said sails are disposed in slots in said sail axle allowing for the mounting of sails to axles without the necessity of welding. In such case, it is preferable that said sails are fixed with respect to said slots by screws and bolts.

Preferably, said sail axle passes through apertures in said column comprising a central rod concentric with said vertical axis. In another preferable embodiment said column further comprises a rotating case in which said central rod is housed and comprising apertures through which said sail axles project. It preferable for said case to comprise cylindrical segments each having a pair of apertures through which one sail axle projects. Said case may preferably comprise a top section and a base section.

In yet another embodiment, said column preferably has a transverse sleeve in which said axle is journalled for rotation.

Preferably, said sails are prevented from rotating more than 90 degrees about their sail axes by said stops and are preferably prevented from rotating more than 90 degrees in any one direction by contact of said stops with at least one stud affixed to said sail axles. In one embodiment pairs of said studs preferably project from said sail axles perpendicularly from one another and said stops preferably comprise a pair of pegs projecting from said central rod or said case parallel to said sail axle. In another embodiment, said stops preferably comprise an absent circumferential section of the sleeve through which a single stud of the axle protrudes. It this case, it is preferable to have a locking screw passing through a hole in said central rod and a circumferential slot in said sail axle prevents said sail axle from moving in a direction parallel said sail axis.

In yet another embodiment, said stops preferably prevent rotation of said sail axles exceeding 90 degrees in any one direction by contacting with said sails, said stops preferably projecting from said sleeve. Preferably, said stops comprise rigid bars having two end sections that are parallel to one another and are connected by an intermediate section to space said end sections, one end section being connected to said sleeve. Preferably, the rotation of said sails about said vertical axis causes rotation of said column which drives a mechanical system, said mechanical system preferably comprising an electricity generator.

In its simplest form, the present invention provides a vertical axis wind generator comprising one or more pairs of sails mounted for rotation about a vertical axis by wind blowing in a wind direction perpendicular to said axis, wherein said sails each have a windward side and are each rotatable about a sail axis perpendicular to said vertical axis between stops defining a driving position in which the windward side is substantially parallel said vertical axis and a low-resistance position of each sail in which said windward side is substantially parallel said wind direction, characterised in that the sails of a pair are linked to one another so that both rotate together about their respective sail axis between said positions.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1a is a perspective view of a vertical axis wind generator ir\ accordance with the present invention, Figure 1 b being a detailed side view, partly in section; Figure 2 is a section across the column of the wind generator of Figure 1 ;

Figure 3 is a partial perspective view of a central rod assembly of an alternative arrangement of generator in accordance with the present invention; Figure 4 is a perspective view of a sleeve comprising stops; Figure 5 is a sectional side view of a vertical axis wind generator including the sleeve and stops of Figure 4;

Figure 6a is a perspective view of one particular embodiment of a sail axle, and Figure 6b is a perspective view of one particular embodiment of a sail for use with the sail axle of Figure 6a; and

Figure 7 is a sectional side view of the wind generator of Figure 1.

DETAILED DESCRIPTION

Referring to the particular embodiment of the present invention shown in Figures 1a and b, a wind generator 10 comprises four arrays of sails 12a to d fixed to axles 14a,b perpendicular to and intersecting a central axis 16 which is arranged to be substantially vertical in use. The sails 12a to d are arranged such that arrays 12a and b share common axles 14a. Similarly, arrays 12c and d share the common axles 14b which are perpendicular to the set of axles 14a. The sails of arrays 12a to d on opposite ends of axles 14a,b are oriented perpendicularly with respect to one another and are fixed such that if the planes of the sails 12a are oriented horizontally, the planes of the opposite sails 12b will be vertical. The ends of the sails 12a to d are curved into the wind to maximise wind capture of the driving sails and curved away from the wind direction to minimise drag forces of the sails returning into the wind.

The axles 14a,b are able to rotate about their long (sail) axes 15, influencing the orientation of the sails 12a to d to the wind (for example blowing in the direction of the Arrow A in Figure 1 ). However, the sails are restricted from rotating more than about 90 degrees in any one direction by studs 18 fixed to the axles 14a,b and stops 20 fixed to casing 22. Each axle 14a, b has two fixed studs 18 on opposite sides of the casing 22. However, as shown more clearly in Figure 2, a single stud 18' can protrude from the axle 14a,b on each side of the casing 22, perpendicularly with respect to one another. Each stud 18 projects perpendicularly from the plane of the particular sail 12a to d on the corresponding end of the axle 14a,b. Likewise, a single stop 20' can extend parallel to the axles 14a, b from each side of the casing, and are of sufficient length to make contact with the studs 18' when the axles 14a,b are rotated preventing further rotation.

As seen in Figure 2, the each pair of stops 20' is arranged off-axis, either side of the axles 14a,b such that one stop 20' prevents further clockwise rotation of the axles while the other stop 20' prevents further anticlockwise rotation. In principle any system of studs and stops can be employed to restrict the rotation of axles 14a,b to about 90 degrees.

Figure 3 discloses one such alternative system whereby the rotation axle 14a comprises only one stud 18b which is restricted to a 90 degree range of rotation by a tubular bearing sleeve 19 attached to an aperture 28 on the central rod 26. The axle 14a is prevented from sliding along the direction of its long axis 15 through the aperture 28 by a locking screw 21 threaded through a hole 23 in the central rod 26 and engaging a circumferential slot (not shown) in the axle 14a. The tubular bearing 19 comprises a cylindrical tube with a quarter section 25 of its circumference absent, permitting the stud 18b to protrude from the axle 14a through the missing section, and defining two stops 20a, b at each end of the section. Rotation of the axle 14a is then restricted to a range of about 90 degrees by contact of the stud 18b with the stops 20a,b. To allow rotation of the axle 14a, the circumferential slot (not shown) through which the locking screw 21 passes must extend at least a quarter of the way around the circumference of the axle 14a.

A further alternative system of stops is shown in Figure 4. A tubular sleeve 36 is arranged to pass through the central rod (not shown in Figure 4) and journal a central section of the sail axle 14a,b along the sail axis 15 though bearings 32 (see Figure 6a). Identical stops 34,34' extend from opposite ends of a tube 36. Each stop 34 comprises a rigid bar bent at two points producing two end sections 34a, c and a middle section 34b. The two end sections 34a,c are parallel to one another and are joined by the middle section 34b which is perpendicular to both. The end sections 34a,a' of each stop 34,34' are attached to the outer surface of the tube 36 (for example by welding) such that the other end sections 34c,c' extend beyond the axial length of the tube 36, radially spaced from the axis 15. The two stops 34,34' are positioned on the tube 36 parallel to one another and both lie in a plane parallel to the sail axle 14a or b.

The sleeve 36 is incorporated into the central rod as shown in Figure 5, such that it passes through the apertures 28 perpendicularly to the vertical axis 16. The stops 34,34' are fixed to sections of the tube 36 that are located outside of the central rod 26. Bearings 32 allow the sail axle 14a to rotate about the sail axis 15 within the sleeve 32 whilst the sleeve 32 remains stationary with respect to the central rod 26.

Sails 12a,b disposed perpendicularly to one another at opposite ends of the sail axle 14a are then prevented from rotating more than 90 degrees in any one direction about the sail axis. The sails 12a,b are prevented from rotating about the sail axis when one sail 12b abuts a stop 34. The sails 12a,b can then rotate 90 degrees about the sail axis 15 in the opposite direction until the opposite sail 12a abuts the second stop opposite 34'.

Further bearings 38 permit the rotation of the central rod 26 about the vertical axis 16 within a supportive base 40.

One method of attaching the sails 12a to d to the sail axles 14a or b ensuring that they are perpendicular to one another is to use the modified sail axle 14c disclosed in Figure 6. In this embodiment, the sail axle 14c comprises slots 42 at either end, into which sections of the sails 12a to d can slot. The slots 42 pass through the diameter of the sail axle 14c and extend from either end along the length of the sail axle 14c. Each slot 42 is oriented perpendicularly with respect to the other. The sail axle 14c also comprises screws 44 at either end that penetrate the sail axle 14c, traverse each slot 42 and thread onto bolts 46. This system allows a defined section of each sail 12a to d to slot into the slots 42 by an amount determined by the length of the slots 42. The screws 44 can then be fastened, threading through holes 48 in the sail axle 46 and holes 50 in the sails 12a to d. Undesired rotation of the sails 12a to d about the axes of the screws 44 can be minimised by ensuring that the sails 12a to d are slotted into the slots 46 to the maximum extent allowed, such that the slots 46 restrict such movement.

Referring again to Figure 1 , the casing 22 forms a central column parallel to and centred on the vertical axis 16 and can comprise several segments 24a to c. Each segment 24a is a cylindrical section having apertures through which the axles 14a,b pass. The bottom

24b and top 24c segments are not penetrated by the axles 14a,b, and respectively serve as the base and 'cap' of the column casing 22. The bottom segment 24b is flanged at its lower end to provide a wide base for supporting the column casing 22, axles 14a,b and sails 12a to d. The top segment 24c is conical in shape and has a closed upper part to cover and protect the cavity of the column casing 22.

As shown in Figure 7, one embodiment comprises a central rod 26 centred along axis 16 within casing 22. Axles 14a,b intersect the central rod 26 through apertures 28 and protrude from the casing segments 24a at opposite sides. When the plane of a sail 12a to d is vertical, it is pushed by the wind exerting a torque about the central axis 16. The sail 12a to d and its corresponding axle 14a or b then rotate about the central axis 16 forcing the casing segment 24a and central rod 26 to rotate also. Segments 24a can be fixed to one another ensuring that the arrays of sails 12a to d, their corresponding axes 14a,b and segments 24a and the central rod 26 rotate simultaneously at the same rate. The central rod 26 runs the length of the casing column 22 and continues below the bottom segment 24b where it is connected to a driving cog 30. The driving cog is fixed to the central rod 26 such that rotation of the central rod 26 causes simultaneous rotation of the cog 30. The driving cog can then be used to rotate a generator (not shown) to generate electricity. Alternatively, the driving cog 30 or the central rod 26 itself can provide mechanical energy to any system.

Referring again to Figure 1, each sail has a windward side 121 and a leeward side 122, defined essentially by the curvature of the ends. When the wind blows in the direction of the Arrow A, because the curvature of the leeward side of the sails offer less resistance than the windward side, the sails 12d are in a driving position where their surfaces are all in line and essentially planar in a plane parallel the axis 16. In adopting this position, each sail 12d has twisted the sails 12c on opposite side so that the sails 12c are in a low resistance position. Consequently, the force of the wind drives sails 12d, rotating the entire generator in the direction of the Arrow B, while the sails 12c are able to traverse through the wind without retarding unduly the rotation of the generator.

The sails 12a,b in the position shown in Figure 1 experience little wind effect and consequently have any orientation that they care to adopt (for example, the top and bottom sails are arbitrarily shown in Figure 1 at slightly different rotational positions to the two sails in between). However, once the tips 123 of the sails 12a catch the wind A, they snap into their maximum resistance position, since this offers greater resistance than the downwind sails 12b whose curved ends face away from the wind. Quickly, therefore, the sails 12a takeover primary driving of the generator, with the sails 12b, as they come into the wind, being in their low-resistance position. At the same time, the departing sails 12d are soon minimally impacted by the wind so that they can adopt arbitrary positions before sails 12 c turn into the wind. This procedure ensures that the up-wind movement of the sails is with minimum resistance, enhancing the efficiency of the generator.

While the above described embodiments suggest a rigid connection between driving and up-wind sails, other embodiments of the present invention may be conceivable. For example, there is no fundamental reason why the axles 14a,b need be perpendicular to the axis 16. They could be inclined at some other angle. Indeed, they may be in a V- shaped formation with respective pairs of sails joined through a universal joint or the like in the column 22. Moreover, the sails need not necessarily be in two pairs with a cross formation as described above. Indeed, they may not even be in pairs at all. They could comprise groups of three or more sails arranged about a mechanical system centred on the vertical axis, whereby the rotation of one sail to its vertical driving position causes a rotation of the remaining sails in the group about their sail axes, such that when sails are moving upwind, they are in their low resistance horizontal positions. In one particular embodiment, three sails have independent sail axes that interact with a mechanical system comprising a series of cogs, thus allowing the orientation of one sail to influence the orientation of the remaining two sails. The rotation of sails from horizontal low resistance orientations to driving vertical positions may occur gradually over the course of their rotation about the vertical axis, but preferably occurs abruptly when making the transition from rotating downwind to upwind. Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A vertical axis wind generator comprising at least two sails mounted on opposite sides of a support column for rotation about a vertical axis by wind blowing in a wind direction perpendicular to said axis, wherein said sails each have a windward side and a leeward side and are each rotatable about a sail axis inclined to said vertical axis between stops on said column defining for each sail a driving position, in which the windward side is substantially parallel said vertical axis, and a low-resistance position, in which said windward side is substantially parallel said wind direction, wherein, when the wind impacts the windward side of a said sail it tends to rotate the sail towards said driving position whereas when the wind impacts the leeward side it tends to rotate the sail towards said low-resistance position, whereby the generator has two sides with respect to the wind separated by said vertical axis, said sides being a driven side on which the sails are urged towards their driving position and in which they offer maximum resistance to the wind and a return side on which the sails are urged towards their low-resistance position and in which they offer minimum resistance to the wind, characterised in that the sails are interconnected so that, when a said sail is rotated into its driving position, the other sail is correspondingly rotated into its low-resistance position.

2. A vertical axis wind generator as claimed in claim 26, in which said inclination is perpendicular.

3. A vertical axis wind generator as claimed in claim 1 or 2, wherein said sails are in pairs and the sail axis of each said pair is in the same plane.

4. A vertical axis wind generator as claimed in claim 3, wherein each sail is oriented perpendicularly with respect to one another about their respective sail axis.

5. A vertical axis wind generator as claimed in claims 3 or 4, wherein the sails of each said pairs are connected by a single sail axle each sharing the same sail axis.

6. A vertical axis wind generator as claimed in any preceding claim, wherein said sails are disposed in slots in said sail axle.

7. A vertical axis wind generator as claimed in claim 6, wherein said sails are fixed with respect to said slots by screws and bolts.

8. A vertical axis wind generator as claimed in claim 5, 6 or 7, wherein said sail axle passes through apertures in said column comprising a central rod concentric with said vertical axis.

9. A vertical axis wind generator as claimed in claim 8, wherein said column further comprises a rotating case in which said central rod is housed and comprising apertures through which said sail axles project.

10. A vertical axis wind generator as claimed in claim 9, wherein said case comprises cylindrical segments each having a pair of apertures through which one sail axle projects.

11. A vertical axis wind generator as claimed in claims 9 or 10, wherein said case comprises a top section and a base section.

12. A vertical axis wind generator as claimed in any of claims 8 to 11 , wherein said column has a transverse sleeve in which said axle is joumalled for rotation.

13. A vertical axis wind generator as claimed in any preceding claim, wherein said sails are prevented from rotating more than 90 degrees about their sail axes by said stops.

14. A vertical axis wind generator as claimed in claim 13, wherein said stops prevent rotation of said sail axes exceeding 90 degrees in any one direction by contacting with at least one stud affixed to said sail axles.

15. A vertical axis wind generator as claimed in claim 14, wherein pairs of said studs project from said sail axles perpendicularly from one another.

16. A vertical axis wind generator as claimed in claim 13, 14 or 15, when dependent on claim 9 or 10 wherein said stops comprise a pair of pegs projecting from said central rod or said case parallel to said sail axle.

17. A vertical axis wind generator as claimed in claim 13, 14 or 15, when dependent on claim 12, wherein said stops comprise an absent circumferential section through which a single stud of the axle protrudes.

18. A vertical axis wind generator as claimed in claim 17, wherein a locking screw passing through a hole in said central rod and a circumferential slot in said sail axle prevents said sail axle from moving in a direction parallel said sail axis.

19. A vertical axis wind generator as claimed in claim 13, wherein said stops prevent rotation of said sail axles exceeding 90 degrees in any one direction by contacting with said sails.

20. A vertical axis wind generator as claimed in claims 12 and,19 wherein said stops project from said sleeve.

21. A vertical axis wind generator as claimed in claim 19 or 20, wherein said stops comprise rigid bars having two end sections that are parallel to one another and are connected by an intermediate section to space said end sections, one end section being connected to said sleeve.

22. A vertical axis wind generator as claimed in any preceding claim, wherein the rotation of said sails about said vertical axis causes rotation of said column which drives a mechanical system.

23. A vertical axis wind generator as claimed in claim 22, wherein said mechanical system comprises an electrical generator.

24. A vertical axis wind generator comprising one or more pairs of sails mounted for rotation about a vertical axis by wind blowing in a wind direction perpendicular to said axis, wherein said sails each have a windward side and are each rotatable about a sail axis perpendicular to said vertical axis between stops defining a driving position in which the windward side is substantially parallel said vertical axis and a low-resistance position of each sail in which said windward side is substantially parallel said wind direction, characterised in that the sails of a pair are linked to one another so that both rotate together about their respective sail axis between said positions.

25. A vertical axis wind generator as claimed in claim 24, having the features of any of claims 4 to 22.

26. A vertical axis wind generator substantially as hereinbefore described with reference to the accompanying drawings.