GB2464315A

GB2464315A - Wind turbine speed control

Info

Publication number: GB2464315A
Application number: GB0818646A
Authority: GB
Inventors: Matthias Luethi
Original assignee: LUETHI ENTPR Ltd
Current assignee: LUETHI ENTPR Ltd
Priority date: 2008-10-10
Filing date: 2008-10-10
Publication date: 2010-04-14
Also published as: GB0818646D0

Abstract

A vertical axis wind turbine comprises a plurality of turbine blades 20 mounted on upper and lower support elements 24a, 24b about a central axis, each blade 20 being pivotally mounted towards an outer region of the support elements 24a, 24b at a position proximate an outer edge of the blade 20 such that each blade 20 can pivot about an axis substantially parallel to the central axis, an inner edge of each blade 20 being coupled to a weight 34 which biases it towards the central axis such that when the rotation of the blades 20 about the central axis increases the blades pivot against the weight 34 thereby reducing the speed of rotation. The support elements 24a, 24b may be mounted on a central support tube 26, with a shaft 30 located within the central support tube 26 and attached by axial bearings 28a, 28b which support the support elements 24a, 24b, and the weight 34 being movably mounted with respect to the central support tube 26 such that the blades 20 rotate with the support elements 24a, 24b and the central support tube 26 about the shaft 30. Either or both of the support elements 24a, 24b may include, for each blade 20, a stop projection to engage the blade 20 against the biasing force of the weight 34 when the blades 20 are in a closed position. The inner edge of each blade 20 may be substantially straight and the outer edge curving outwardly from an upper edge of the blade 20 to a central region and inwardly from the central region to a lower edge.

Description

VERTICAL WIND TURBINE

Field of Invention

The present invention relates to wind turbines which are arranged to be mounted in use with an axis of rotation which is substantially vertical (vertical wind turbines) and more particularly to wind turbines comprising a plurality of turbine blades pivotally mounted on upper and lower supporting elements about the rotation axis so that the turbine blades rotate in a substantially horizontal plane.

Background of the Invention

Vertical axis wind turbines can provide a number of advantages with respect to horizontal axis wind turbines. For example, vertical axis wind turbines do not need to be arranged to face into the wind. Furthermore, a volume of space occupied by a vertical wind turbine can be much less than that of an equivalent horizontal axis wind turbine thereby making vertical axis wind turbines more suitable for areas where there is a restricted amount of space, such as domestic environments.

In our UK patent GB 2420597, a vertical axis wind turbine is described in which an effective regulation of the speed of the turbine blade is achieved by a centrifugal governor. Turbine blades are pivotally mounted such that an increase in wind and/or a centrifugal force causes the turbine blades to pivot about their mountings so that the turbine blades swing outwards thereby reducing the surface area of the blades which is exposed to the wind and thus regulating the speed of rotation of the turbine. The inventor of the vertical wind turbine disclosed in GB 2420597 has sought to make improvements to the wind turbine disclosed in this UK patent application.

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Sum mary of Invention According to the present invention there is provided a wind turbine for mounting in operation substantially vertically, the wind turbine comprising a plurality of turbine blades mounted on upper and lower supporting elements about a central axis. The upper and lower supporting elements may be in any form such as to provide structural support to the blades in a plane perpendicular to the central axis, such as for examples discs of any shape. Each turbine blade is pivotally mounted towards an outer region of the upper and lower supporting elements at a position proximate to an outer edge of the turbine blade, such that each blade can pivot about an axis substantially parallel to the central axis. An inner edge of each blade is coupled to a weight which is arranged to bias the inner edge of the turbine blade towards the central axis such that when the turbine blades are placed in a fluid flow they rotate together about the central axis and, as their speed of rotation increases, the turbine blades pivot about their mountings against the weight, thereby tending to reduce the speed of rotation. The upper and lower support elements are mounted on a central support tube, which provides a central axial space and maintains the upper and lower supporting elements in a spaced apart relationship. The central support tube may have any cross-sectional shape, which may not necessarily be continuous. A mounting shaft passes through the central axial space of the central support tube and is attached to a first axial bearing located to support the upper support element and is attached to a second axial bearing located to support the lower support element, and the weight is movably mounted with respect to the central support tube, such that the turbine blades rotate with the upper and lower support elements and the central support tube about the mounting shaft, whilst being supported by the first and second bearings.

According to the present invention a wind turbine for mounting substantially vertically in use, which uses a weight or mass to bias pivotally mounted turbine blades against a centrifugal force and a pressure caused by the wind, so as to regulate the speed of the turbine, includes upper and lower support elements and a central support tube is connected between the upper and lower support elements to separate the position of the upper and lower support elements. A mounting shift, which in use is mounted substantially vertically and is fixed to a supporting body such as a building or the ground passes through a central void or space provided by the central support tube and connects to the upper and lower supporting elements or the central support tube proximate the upper and lower support elements by first and second bearings. As such, an improvement can be provided in the mounting of the wind turbine in a more stable or reliable way.

According to another aspect of the invention there is provided a wind turbine according to the pre-characterising portion of claim 1, wherein either or both of the upper and lower support elements include for each turbine blade a stop projection, which project beyond a plane of the upper or lower support elements to engage the blade against the biasing force of the weight, when the turbine blades are in a closed position, so that a minimum gap is provided between the inner edge of the turbine blade and the central support tube through which fluid air can pass.

According to this aspect of the invention, stop projections are provided to ensure that there is a minimum gap between the inner edge of the blades and the central support tube, such that even at relatively low wind speeds, an air flow is provided across the turbine thereby causing a driving force to rotate the turbine. Thus the wind turbine is provided with a lower start-up wind speed. For example, for a blade width from the inner edge to the outer edge at the central region of 750mm the minimum gap could be 100mm to 140mm, thus providing a ratio of 6.25:1.

According to another aspect of the invention there is provide a wind turbine according to the pre-characterising portion of claim 1, wherein the inner edge of each turbine blade is substantially straight, and the outer edge of each turbine blade curves outwardly with respect to the inner edge from an upper edge of the blade to a central region and inwardly from the central region to a lower edge. In one example, the profile of each of the turbine blades in an aspect view has a first flat portion and a second curved portion, the flat portion being separated by the curved portion by a virtual line, the virtual lines curving from a point on the upper edge outwardly with respect to the inner edge to the central region and inwardly to the lower edge with respect to the inner edge, the virtual line being at a maximum distance from the inner edge at a central point along a vertical axis of the turbine blade.

According to this aspect of the invention, the inventor has found that an improvement is provided in the torque generated by the wind turbine for a given wind speed for turbine blades arranged with the above profile.

In another embodiment of the invention each turbine blade has a substantially straight vertical inner edge, an upper edge and a lower edge, and an outer edge curving outwardly with respect to the inner edge from a virtual line between the upper edge and lower edge, the virtual line being at a maximum distance from the inner edge at a central point along a vertical axis of the turbine blade. In a further embodiment a rate of change in gradient of a horizontal cross-section of the curving outer edge of each turbine blade decreases from a first point on the upper edge of the turbine blade to a minimum at second point between the upper top edge and lower edge, and then increases to a third point on the lower edge.

In another embodiment of the invention, the vertical wind turbine comprises at least groups of turbine blades. Each group of turbine blades are arranged to rotate together around the fixed shaft, the groups of turbine blades arranged such that a first group of turbine blades rotate in an opposite direction to a second group of turbine blades.

in one embodiment of the invention, the number of turbine blades in the plurality of turbine blades is three. The inventors have discovered that an improved efficiency of the vertical wind turbine can be achieved if three turbine blades are used.

According to a further embodiment of the invention, an electrical generator for the vertical wind turbine is provided which comprises a magnet bearing stator mounted around a first shaft and a coil bearing rotor mounted around a second shaft, the first shaft and second shaft positioned on the central axis. One of the stator or rotor comprises a void of into which at least a part of the other of the stator or rotor is received such that when the first and second shaft rotate relative to each other, the one of the stator or rotor rotates within the void of the other of the stator or rotor and are thereby operable to generate electricity.

Various further aspects and features of the invention are defined in the appended claims.

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Brief Description of Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings where like parts are provided with corresponding reference numerals and in which: Figure 1 provides an example illustration of a vertical wind turbine as disclosed in our UK patent GB 2420597; Figure 2 provides a schematic diagram of an aspect view of a wind turbine in accordance with the present technique; Figure 3 shows the vertical wind turbine in Figure 2 as a plan view; Figure 4 shows a three dimensional view of the wind turbine shown in Figures 2 and 3; Figures 5 shows examples of the wind turbine shown in Figures 2, 3 and 4 in which the turbine blades are closed with respect to the flow of air; Figures 6 shows examples of the wind turbine shown in Figures 2, 3 and 4 in which the turbine blades are opened with respect to the flow of air; Figure 7 shows a schematic representation of an arrangement of a dynamo or generator which is vertically mounted with respect to the wind turbine; Figure 8 shows a schematic diagram of an example of a stator of the generator; Figure 9a and 9b provide an illustrative representation of an example stator of the example generator; Figure 10 provides an illustrative representation of an example rotor of the

example generator;

Figure 11 provides a three dimensional representation of a profile of one of the turbine blades which can be used with the vertical axis wind turbine shown in Figures 2tolO; Figure 12 provides another three dimensional representation of the profile of the turbine blade shown In Figure 11; Figure 1 3a shows in plan view a profile of a turbine blade through a section a-a; Figure 13b shows in plan view a profile of the turbine blade through a section b-b; Figure 13c shows a profile of the turbine blade through a section cc; Figure 14a provides an elevation view of the turbine blade;

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Figures 14b provides an elevation view of the turbine blade; Figure 14c provides a plan view of the turbine blade; Figure 15 shows a schematic representation of a further example of the vertical wind turbine shown in Figures 2 to 6; Figure 16 shows schematic representation of the wind turbine shown in Figure 16 mounted on a pitched roof, Figure 17 provides a schematic representation of a cowl appearing in Figure 17, shown in an expanded view; Figure 18 shows a schematic representation of an example embodiment in which two turbines are mounted one above the other; and Figure 1 9a provides schematic diagram of an orientation of the turbine blades in the embodiment shown in Figure 18; and Figure 1 9b provides schematic diagram of an orientation of the turbine blades in the embodiment shown in Figure 18.

Description of Example Embodiments

Figure 1 provides an example illustration of a vertical wind turbine as disclosed in our UK patent GB 2420597. In Figure 1 a frame I is shown to support a vertical shaft 8, which is arranged with bearings 2 to rotate about a central vertical axis. A S lower blade support I Ia in combination with an upper blade support 1 lb supports wind turbine blades 6 which rotate about a pivot points 12. An inside edge of each of the turbine blades 7 is connected to a weight 9 via link elements 10. The main shaft 8 which is rotatably mounted via bearings 2 drives a gearing arrangement 4 which is connected to a generator/alternator 3 for generating electricity.

As explained in our UK patent GB 2420597, a driving force generated by the turbine blades 6 causes the upper and lower blade support frames 11 a, 11 b to rotate with the turbine blades about the support bearings 2. As disclosed in our UK patent GB 2420597, an effective regulation of the speed of the turbine blade is achieved by the arrangement of connecting the turbine blades 6 to the weight 9 via the link elements 10. The link elements 10 are connected via universal joints 14 which allow movement in both vertical and horizontal planes. As the speed of the turbine blades increases as a result of an increase in wind speed, a centrifugal force, which is experienced by the turbine blades, andlor a pressure of the wind, causes the turbine blades to pivot about the pivot mountings 12 so that the turbine blades swing outwards thereby reducing the surface area of the blades which is exposed to the wind. Thus UK patent GB 2420597 provides a simple and effective way of regulating the speed of rotation of a wind turbine by reducing an amount of surface area of the turbine blades 6 which are exposed to the wind as the force of the wind increases and as the rotation of the vertical turbine increases about the vertical shaft 8. This is achieved by a movement of the weight or mass 9 along the vertical shaft 8 as the turbine blades 6 pivot about their pivot mountings 12.

The inventor of the vertical wind turbine disclosed in GB 2420597 has sought to make improvements to the wind turbine disclosed in this UK Patent and has now devised an improved wind turbine which seeks to increase an effective wind range in which the turbine can operate and therefore for example generate electricity. Although wind turbines have been devised for domestic application, it has been observed by the inventor that these wind turbines, which are typically of a horizontal rotation axis type, have been developed within a wind tunnel in which the wind is produced from a single source and is therefore flowing in one direction. However, in practice when such turbines are mounted in a domestic or practical environment, the wind is very rarely produced from a single direction but is disturbed by surrounding buildings and structures which for example causes the wind to engage the wind turbine not only from different horizontal directions but also in a vertical or rising direction with the effect that the wind engages the wind turbine from below to above or from above to below.

The inventor of the wind turbine which will now be described and which embodies the present invention has been devised in order to increase the wind range of the turbine so that the turbine can generate electricity in an even wider range of wind speeds and directions.

Figure 2 provides an aspect view of a wind turbine in accordance with the present technique. In Figure 2 the wind turbine is shown to be comprised of three turbine blades 20 which are pivotally mounted about pivot shafts 22 on upper and lower supporting elements which in one example may be disc shaped 24a 24b. The supporting discs 24a and 24b are mounted on a central support tube or shaft 26 which is connected to the upper and lower supporting discs 24a 24b by support bearings 28a and 28b. The central support tube 26 rotates with the supporting discs 24a, 24b about a fixed mounting shaft 30 on which the turbine is mounted on support bearings 28a 28b.

The vertical wind turbine shown in Figure 2 is also shown in Figure 3 as a plan view.

As with the vertical wind turbine disclosed in GB 2420597, the speed of rotation of the wind turbine is regulated by a weight or mass 34 which can move up and down the support shaft 26 as the turbine blades 20 pivot about their pivot axis 22 which causes an inner edge of the blades 36 to swing out therefore drawing up the weight 34 which is connected to the inner edge via a plurality of linking arms 38a 38b to the weight 34.

The central support tube 26 may be of any cross-sectional shape but preferably the weight 34 and the support tube 26 have a complementary shape. For example the central support tube may be cylindrical 26 and the weight 34 may be in the form of a collar.

The improvements which the inventors have devised to increase the wind range of the vertical wind turbine also includes stop projections 40 about which the inner edge of each of the turbine blades impinge when the turbine blades are closed and are biased against the stops 40 by the weight 34 on the central support tube 26 which is pulled and applies a biasing force to the inner edge of the turbine blades via the linking arms 38a 38b. The position of stops 40 and the profile of the turbine blades is adapted to provide a gap 42 between the edge of turbine blades 20 and the central support tube 26. The gap 42 has an effect of allowing wind to pass through the wind turbine therefore and thereby causing an air flow across the turbine blades which therefore generates a driving force substantially perpendicular to a rear surface of the turbine blades 20 therefore driving the wind turbine about the bearings 28a, 28b.

In one example, the dimensions of the turbine blade as shown in Figure 2 are blade height 33 = 1500mm, the gap 42 = 120 mm, the width of the turbine blades 31 750mm, and a gap between the upper and lower edges of the blade and the upper and lower supporting discs is 50mm. Thus a ratio of the span or width of the blade 31 to the size of the gap 42 is approximately in a proportion of 6.25:1. It will be appreciated that in other examples the gap 42 may be in a ratio with respect to the blade width of 8:lor5:1.

in addition to the gap 42, a gap may be provided between the upper and lower edges of the blade and the upper and lower supporting discs in order to improve the air flow.

A three dimensional view of the wind turbine shown in Figures 2 and 3 is shown in Figure 4 where reference numerals shown in Figure 4 are the same as those shown in Figures 2 and 3.

Figures 5 and 6 show examples of the wind turbine shown in Figures 2, 3 and 4 in which the turbine blades are closed and opened to the fluid flow of the air respectively. Thus as shown in Figure 5 the turbine blades have been arranged to pivot about their pivot points 22 outwards as a result of a force of the wind on the turbine blades thus drawing the weight 34 along the central support tube 26. Figure 6 provides an illustration of the turbine blades in an opened position in which a maximum amount of the active area of the turbine blades is exposed to the wind such as would be the case if the turbine blades were stationary with the weight 34 at a lower position and the edge of the turbine blades 20 resting against the stops 40. Thus, as can be seen m Figure 6 an air gap 42 is provided in order to allow wind to pass through the turbine thus generating an air flow across the turbine blades as explained above.

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Returning to Figure 5, further explanation will now be provided with regard to the mounting of the vertical turbine. As explained above with reference to Figures 2 to 6, in use the turbine is mounted on a vertical mounting shaft 30, which passes through the central support tube 26 and is connected to the upper supporting disc 24a via the bearing 28a and the lower support disc 24b by the lower bearing 28b. Thus one advantage of the wind turbine shown in Figures 2 to 6 is that the central support tube 26 is stationary with respect to the weight 34, which is therefore free to move up and down the central support tube 26 without any rotational movement, therefore reducing any potential friction on or between the weight 34 and the central support tube 26.

Thus the upper and lower support discs 24a 42b, the central support tube 26 and the collar 34 which forms the weight all rotate with the vertical wind turbine on a vertical axis. Furthermore, in order to improve a mounting of the vertical wind turbine on a supporting shaft 30, the upper and lower support bearings 28a, 28b are provided so that the mounting shaft 30, which is fixed, can pass through the central support tube 26 thereby fully supporting the wind turbine throughout its length in a vertical direction.

Thus, unlike for example would be the case if the wind turbine was mounted at its lower end on a rotational bearing and ranged to rotate about that lower bearing, the wind turbine is fully supported throughout its vertical length thereby providing a more stable arrangement for mounting.

Annular Generator In order to improve further the stability of the mounting of the wind turbine and the coupling of the wind turbine to a generator, the inventor has provided an arrangement in which a "doughnut" like generator is provided which combines with a stable arrangement for mounting the wind turbine on the vertical support shaft or axel 30. As shown in Figure 5 a stator 54 of an example generator is supported on the vertical support axel 30 by mounting brackets 52. Thus the stator 54 of the generator is provided in the form of a circular or annular shape which allows a rotor 56 to be disposed in a central area of the stator 54 coaxially with the support shaft 30 so that as the wind turbine rotates on the mounting bearing 54 the rotor causes the necessary change in the magnetic field to generate electricity.

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The arrangement of the dynamo or generator which is co-axially mounted with respect to the wind turbine is shown in more detail in Figure 7. As shown in Figure 7 the support brackets 52 which are fixed to the vertical mounting shaft 30 are attached with bolts 53 to the stator 54. The rotor 56 therefore rotates within a central area of the stator 54 co-axially with the central support tube 26, as the wind turbine including the lower support disc 24 rotates about the mounting bearing 28b, which are fixed by bolts to the rotor 72. A lower bearing of the wind turbine 28a allows the turbine to rotate about the vertical mounting shaft 30 and is arranged to cause the rotor 56 to rotate within the stator 54.

Although in the embodiment shown in Figure 7, the dynamo is positioned towards the bottom of the turbine below the blades, in some embodiments the dynamo can be placed on the top of the turbine above the blades, so that the stator is attached to the top of the vertical mounting shaft and the rotor is attached to the upper support disc 24a.

An example of the stator of the generator is shown in Figure 8. As shown in Figure 8, coil elements 80 are arranged around a circumferential region 82 of the stator whereas a void area 84 is provided for mounting the rotor 56. Schematic drawings of an example stator are shown in Figure 9a and Figure 9b. Schematic drawings of an example of the rotor 56 is shown in Figure 10 which in the present example includes permanent magnets which when rotated causes the necessary change in the magnetic field which induces current in the coils 80 of the stator.

Turbine Profile A further example embodiment of the present invention provides a wind turbine in which the profile of the turbine blades 20 is adapted in order to increase as far as possible a driving force generated by the turbine blades as air flows over the active surface of the turbine blades 20 and also causes a rotational driving force produced by a centre of effort of the turbine blades substantially perpendicular to the surface therefore driving the turbine blade and the wind turbine more efficiently.

Examples illustrating the profile of the wind turbine blade is shown in Figures 11, 12, 13 and 14.

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Figures 11 and 12 provide a three dimensional representation of a profile of the turbine blades 20 which can be used with the wind turbine explained and described above with reference to Figures 2 to 10. In Figures 11 and 12 the turbine blade 20 has a substantially straight and usually vertical edge 100 and a profiled area 120. As shown in Figure 11 lines a-a, b-b, c-c are shown drawn with respective to an upper, a middle and a lower section of the three dimensional representation of the turbine blade. Figure I 3a shows in plan view a profile of the blade through section a-a, Figure 1 3b shows a profile of the blade in plan view with respect to section b-b, and Figure 1 3c and 12 show a profile of the blade through the section c-c. As illustrated in Figure 11 the upper and lower top and bottom edges of the turbine blade are shown to curve towards an outer edge whilst the outer edge 120 is shown to curve outwardly with respect to the inner edge 100. Thus as shown in Figure 1 3b, the central section of the profile of the blade shows that the outer edge b-b is longer than the outer edge at sections a-a and c-c. Furthermore, in order to improve the driving force provided by the turbine blades, a rear surface plane of the outer or rear side of the turbine blades 122 curves outwardly with respect to the inner edge 100. Thus the rear outer portion edge 122 is shown to curve outwardly with respect to the inner edge 100. The profile of the blade 20 can also be seen from elevation views A and B in Figures 14a and 14b whilst the plan view is provided from a view C is provided in Figure 14c. As shown in Figures 14a which provides a rear view of the turbine blade 20 the turbine blade can be described as having a first portion 130 which is flat and a second portion 132 which is curved.

Separating the flat and the curved portions 130, 132 is the outer rear edge 122 which can be viewed as a virtual line of the profile of the blade. As shown in Figure 14a, the outer edge 122 which defines a boundary between the flat portion 130 and the curved portion 132 curves outwardly from the upper edge 124 to the centre and then back towards the edge 100 from the centre to the lower edge 126. Similarly, when viewed from position B shown in Figure 11 the profile of the blade elevation view shown in Figure 14b has a flat portion 140 and an inner curved portion 142. A dividing virtual line 144 which divides the flat portion 140 from the curved portion 142 curves outwards from the upper edge 124 towards the centre and back towards the inner edge as it curves from the centre to the lower edge 126.

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As indicated above in one example a span of the blade 31 is approximately 730mm, a circumferential length 101 is 900mm, the flat portion 130, 140 is 400mm the curved portion is 35mm and the upper and lower edge widths are 400mm.

Furthermore, in order to increase the drive of the turbine blade and move the centre of effort of the driving force provided by the turbine blade towards the centre and perpendicular to the blade, a curved portion in the upper half of the blade 146 and the lower half of the turbine blade 148 curves more with a greater gradient than an inner portion towards the centre of the turbine blade 150. Thus as can be seen from the plan view in Figure 1 4c a part of the outer edge of the blade 149 can be seen as the upper portion 146 curves more than the centre portion 150 which is also illustrated in part by the section profiles 1 3a, I 3b, 1 3c.

Further example embodiments Figures 15, 16 and 17 show further examples of the wind turbines according to the present technique and described above, which utilize the features which improve the wind range of the turbine. As shown in Figure 15 the wind turbine corresponds to that in shown in Figures 2 to 6 except that the profile of the blades is adapted so that a lower edge 152 of each of the turbine blades has a smaller flatter portion than that of an upper edge 154 of an upper edge of the turbine blades 153. As such, as shown in Figures 16 and 17 the wind turbine shown in Figure 15 can be mounted on a pitched roof for example at the apex 160 so that a greater amount of wind will be caught by the turbine as it rises up when traveling along the profile of the pitched roof to engage the wind turbine with the effect that a greater amount of an active area of the turbine blades will receive air flow as a result of the wind directed along the pitched roof thereby increasing a driving force on the turbine blades and therefore a speed of rotation of the wind turbine.

Furthermore, the turbine may also include a cowl 160 on its upper edge in order to provide a further improvement in utilization of wind which flows from a lower part of the turbine to an upper part such as that directed along the edge of the pitched roof. Moreover, the blades can be arranged in a "V" shape with the bottom edges of a reduced length compared to the upper edges. Such an arrangement can optimise the use of an upward draft created, for example, by the pitched roof. This

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arrangement can be more effective at harnessing upward drafting winds than blades with bottom and top edges of equal length.

A further example of the wind turbine utilizing the features described above is shown in Figure 1 8. 1-lowever, as shown in Figure 18, two turbines are mounted one above the other and are arranged to contra rotate so that for example the lower turbine would rotate anticlockwise and the upper turbine would rotate clockwise. The different directions of rotation produced from the wind which is likely to be engaging the turbine in the same direction is achieved by mounting the turbine blades in different directions so that on one the blades would curve one way in plan view and the other the blades would curve the other way in plan view. This different orientation of the blades is shown in Figures 1 9a and 1 9b for the turbine mounted as shown in Figure 18.

As illustrated by the example shown in Figure 18 the dynamo or generator 180 which is mounted midway between the upper and lower wind turbines 182 184 is arranged such that the stator part is rotating with the lower turbine 184 and the rotator part is rotating with the upper turbine 182 so that the relative speed of rotation and therefore the amount of electricity generated by the turbine is increased approximately by a factor of two. Thus the dynamo or generator 186 could be implemented using the generator described above with reference to the wind turbines here and before described.

Various further aspects and features of the present invention are defined in the appended claims. Other embodiments falling within the scope of the appended claims are also envisaged. For example the turbine blades 20 of any of the wind turbines described above could be manufactured from a biodegradable or reusable material such as laminated woven bamboo. Alternatively or additionally, glass reinforced plastic (GRP) material, fibre glass or carbon fibre material could be used. Furthermore, the weight or mass which is used to bias the turbine blades to the closed position could include a cylindrical layer in the inside edge so as to reduce friction as the mass moves up and down the central support tube 26. It will also be appreciated that the wind turbines could be used for other functions besides generating electricity and other blade profiles are envisaged. For example, in one embodiment, the wind turbine may be used to power a water pump. In this embodiment, rather than being connected to a dynamo, the rotating parts of the wind turbine may be connected to a gearbox which is then connected to a pump which can pump water. This embodiment may find particular application in environments where other power sources, such as electricity or diesel which might otherwise be used to power conventional water pumps, are not available.

It is further envisaged that the particular shape and profile of the blades as exemplified in the described embodiments may also be employed in blades used in applications other than wind driven turbines. For example, turbines comprising the blades as described above may be driven by the motion of substances with fluid like characteristics for example gases, liquids or powder. More specifically the turbine blades could be driven by the movement of water or steam.

Claims

CLAIMS1. A wind turbine for mounting in operation substantially vertically, the wind turbine comprising a plurality of turbine blades mounted on upper and lower supporting elements about a central axis, each turbine blade being pivotally mounted towards an outer region of the upper and lower supporting elements at a position proximate an outer edge of the turbine blade, such that each blade can pivot about an axis substantially parallel to the central axis; and an inner edge of each blade is coupled to a weight which is arranged to bias the inner edge of the turbine blade towards the central axis such that when the turbine blades are placed in a fluid flow they rotate together about the central axis and, as their speed of rotation increases, the turbine blades pivot about their mountings against the weight, thereby tending to reduce the speed of rotation, wherein the upper and lower support elements are mounted on a central support tube, which provides a central axial space and maintains the upper and lower supporting elements in a spaced apart relationship, and a mounting shaft passes through the central axial space of the central support tube and is attached to a first axial bearing located to support the upper support element and is attached to a second axial bearing located to support the lower support element, and the weight is movably mounted with respect to the central support tube, such that the turbine blades rotate with the upper and lower support elements and the central support tube about the mounting shaft, whilst being supported by the first and second bearings.
2. A wind turbine as claimed in Claim 1, wherein the weight and the central support tube have a complementary shape such that the weight can move along the central support tube and do not axially rotate with respect to each other as the turbine rotates about the mounting shaft.
3. A wind turbine as claimed in Claim I or 2, wherein either or both of the upper and lower support elements include for each turbine blade a stop projection,Swhich project beyond a plane of the upper or lower support elements to engage the blade against the biasing force of the weight, when the turbine blades are in a closed position, so that a minimum gap is provided between the inner edge of the turbine blade and the central support tube through which fluid air can pass.
4. A wind turbine as claimed in Claim 1, 2 or 3, wherein the inner edge of each turbine blade is substantially straight, and the outer edge of each turbine blade curves outwardly with respect to the inner edge from an upper top edge of the blade to a central region and inwardly from the central region to a lower bottom edge.
5. A wind turbine as claimed in Claim 4, wherein the profile of each of the turbine blades in an aspect view has a first flat portion and a second curved portion, the flat portion being separated by the curved portion by a virtual line, the virtual lines curving from a point on the upper edge outwardly with respect to the inner edge to the central region and inwardly to the lower edge with respect to the inner edge, the virtual line being at a maximum distance from the inner edge at a central point along a vertical axis of the turbine blade.
6. A wind turbine according to claim 4 or 5, wherein a rate of change in gradient of a cross-section of a curving outer edge of each turbine blade in the curved portion decreases from a first point on the upper top edge of the turbine blade to a minimum at second point between the upper top edge and lower bottom edge, and then increases to a third point on the lower bottom edge.
7. A wind turbine as claimed in any preceding Claim, wherein a ratio of a length of the turbine blade from the inner edge to a point in the central region of the outer edge to the minimum gap provided by the stop projections is approximately 6.25:1.
8. A wind turbine as claimed in any preceding claim, including an electrical generator, the electrical generator include a stator and a rotor, the stator being formed in an annular shape with electromagnetic elements disposed around theSannular shape about a central void, and the rotor including electromagnetic elements being disposed to rotate within the central void such that as the rotor rotates within the void, the generator generates electricity, wherein the stator is coupled to the mounting shaft and rotor is coupled to the central support tube, such that a plane of the annular shape and the electromagnetic elements of the stator and the rotor are disposed in a plane which is substantially perpendicular to the central axis of the turbine.
9. A wind turbine for mounting in operation substantially vertically, the turbine comprising at least two sets of turbine blades, each set of turbine blades comprising a plurality of turbine blades mounted on upper and lower supporting elements about a central axis, each turbine blade being pivotally mounted towards an outer region of the upper and lower supporting elements at a position proximate an outer edge of the turbine blade, such that each blade can pivot about an axis substantially parallel to the central axis; and an inner edge of each turbine blade is coupled to a weight which is arranged to bias the inner edge of the turbine blade towards the central axis such that when the turbine blades are placed in a fluid flow they rotate together about the central axis and, as their speed of rotation increases, the turbine blades pivot about their mountings against the weight, thereby tending to reduce the speed of rotation, wherein the upper and lower support elements are mounted on a central support tube, which provides a central axial space and maintains the upper and lower supporting elements in a spaced apart relationship, and a mounting shaft passes through the central axial space of the central support tube and is attached to a first axial bearing located to support the upper support element and is attached to a second axial bearing located to support the lower support element, and the weight is movably mounted with respect to the central support tube, such that the turbine blades rotate with the upper and lower support elements and the central support tube about the mounting shaft, whilst being supported by the first and second bearings, each of the sets of the turbine blades being mounted on the mounting shaft, and each set of turbine blades is arranged to rotate together around the fixed shaft, the sets of turbine blades being arranged such that a first group of turbine blades rotates in an opposite direction to a second group of turbine blades.
10. A wind turbine as claimed in any preceding claim, wherein the number of the plurality of turbine blades is three or three in each set.
11. A wind turbine for mounting in operation substantially vertically, the wind turbine comprising a plurality of turbine blades mounted on upper and lower supporting elements about a central axis, each turbine blade being pivotally mounted towards an outer region of the upper and lower supporting elements at a position proximate an outer edge of the turbine blade, such that each blade can pivot about an axis substantially parallel to the central axis; and an inner edge of each blade is coupled to a weight which is arranged to bias the inner edge of the turbine blade towards the central axis such that when the turbine blades are placed in a fluid flow they rotate together about the central axis and, as their speed of rotation increases, the turbine blades pivot about their mountings against the weight, thereby tending to reduce the speed of rotation, wherein either or both of the upper and lower support elements include for each turbine blade a stop projection, which project beyond a plane of the upper or lower support elements to engage the blade against the biasing force of the weight, when the turbine blades are in a closed position, so that a minimum gap is provided between the inner edge of the turbine blade and the central support tube through which fluid air can pass.
12. A wind turbine for mounting in operation substantially vertically, the wind turbine comprising a plurality of turbine blades mounted on upper and lower supporting elements about a central axis, each turbine blade being pivotally mounted towards an outer region of the upper and lower supporting elements at a position proximate an outer edge of the turbine blade, such that each blade can pivot about an axis substantially parallel to the central axis; and an inner edge of each blade is coupled to a weight which is arranged to bias the inner edge of the turbine blade towards the central axis such that when the turbine blades are placed in a fluid flow they rotate together about the central axis and, as their speed of rotation increases, the turbine blades pivot about their mountings against the weight, thereby tending to reduce the speed of rotation, wherein the inner edge of each turbine blade is substantially straight, and the outer edge of each turbine blade curves outwardly with respect to the inner edge from an upper top edge of the blade to a central region and inwardly from the central region to a lower bottom edge.
13. A wind turbine as claimed in Claim 12, wherein the profile of each of the turbine blades in an aspect view has a first flat portion and a second curved portion, the flat portion being separated by the curved portion by a virtual line, the virtual lines curving from a point on the upper edge outwardly with respect to the inner edge to the central region and inwardly to the lower edge with respect to the inner edge, the virtual line being at a maximum distance from the inner edge at a central point along a vertical axis of the turbine blade.
14. A wind turbine for mounting in operation substantially vertically, the wind turbine comprising a plurality of turbine blades mounted on upper and lower supporting elements about a central axis, each turbine blade being pivotally mounted towards an outer region of the upper and lower supporting elements at a position proximate an outer edge of the turbine blade, such that each blade can pivot about an axis substantially parallel to the central axis; and an inner edge of each blade is coupled to a weight which is arranged to bias the inner edge of the turbine blade towards the central axis such that when the turbine blades are placed in a fluid flow they rotate together about the central axis and, as their speed of rotation increases, the turbine blades pivot about their mountings against the weight, thereby tending to reduce the speed of rotation, wherein including an electrical generator, the electrical generator include a stator and a rotor, the stator being formed in an annular shape with electromagnetic elements disposed around the annular shape about a central void, and the rotor including electromagnetic elements being disposed to rotate within the central void such that as the rotor rotates within the void, the generator generates electricity, wherein the stator is coupled to the mounting shaft and rotor is coupled to the central support tube, such that a plane of the annular shape and the electromagnetic elements of the stator and the rotor are disposed in a plane which is substantially perpendicular to the central axis of the turbine.
15. A vertical wind turbine substantially as hereinbefore described with reference to Figures 1 to 20 of the drawings.