GB2594947A

GB2594947A - Turbine

Info

Publication number: GB2594947A
Application number: GB2006971.2A
Authority: GB
Inventors: Richard Charlton Gretton John; Charlton Gretton Robert
Original assignee: North Sea Winches Ltd
Current assignee: North Sea Winches Ltd
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2021-11-17
Also published as: GB2595774A; GB202006971D0

Abstract

A wind or water turbine, eg a vertical-axis wind turbine (VAWT), comprises a first member which is rotatable about a first axis of rotation, and one or more vanes 601, 602 … each of which is (i) mounted on the first member; (ii) rotatable with respect to the first member; and wherein (iii) the mounting point of each vane is radially spaced away from the first axis of rotation. The axis of rotation of each vane may be parallel to that of the main member. The rotational position of each vane 601, 602… is defined by the rotational position of the first rotating member, eg using planetary gearing (figs. 7,8), such that such that as the first member rotates in a first direction each vane 601, 602… rotates in proportion to this movement in the opposite direction. Electricity may be generated, eg using magnets and coils. The turbine may be controlled by a weathercock or anemometer.

Description

TURBINE

This invention relates to rotatable apparatus for mounting partially or completely in a flow of liquid. The flow of liquid is preferably air, wherein the movement of the air is due to the wind. The apparatus operates with its axis of rotation substantially at right angles to the wind direction.

By way of background, for over a century, wind turbines have been utilized in converting wind-driven kinetic energy into electricity. In recent years, wind turbines have become an increasingly important source of renewable energy and are being used by many countries as part of a strategy to reduce reliance on fossil fuels. While most wind turbines are configured for rotating about a horizontal axis, a relatively newer type of wind turbine -known as a vertical-axis wind turbine (11/AVVT") -is configured for rotating about a vertical axis.

One advantage of this arrangement is that the generator and gearbox are able to be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, which improves accessibility for maintenance purposes.

CN102418664, CN104533718, US6840738 and GB191018278 describe turbines driven by wind and/or water wherein the vanes of the turbine are adjusted or feathered to reduce the resistance of the vane as the rotation of the turbine moves the vane against the flow of the wind or water.

The object of the present invention is to provide a more efficient design of vertical axis turbine that is intended to be driven by a flow of liquid, such as air (e.g. wind) or water. The invention provides an apparatus for mounting in a flow of liquid comprising: a) a first member, which is rotatable about a first axis of rotation, and b) one or more vanes, wherein the vane or each of the vanes for contacting the liquid is (i) mounted on the first member, and (ii) rotatable with respect to the first member, and wherein (iii) the mounting point of the or each vane is radially spaced away from the first axis of rotation; wherein the or each vane mounted on the first member rotates relative to the first rotating member and the rotational position of the vane is defined by the rotational -2 -position of the first rotating member such that such that as the first member rotates in a first direction the vane or vanes each rotate in proportion to this movement in the opposite direction.

The vane or vanes may each rotate in direct proportion to the rotation of the first member in the opposite direction.

The vane or vanes may extract energy from the flow of liquid by virtue of the drag forces acting on the vanes as the flow of liquid impinges thereon rather than the vanes generating hydrodynamic lift from the flow of liquid.

Accordingly, the first member may rotate with a period of 720 degrees (4 pi radians) and as it does so the vane or vanes each rotate through 360 degrees (2 pi radians). Preferably this relative movement is defined by a linear relationship.

In this way the vanes can be directed to catch the flow of liquid when they are moving in the downstream/downwind direction and to be edge-on or feathered to the flow of liquid when they are moving in the upstream/upwind direction. Advantageously this reduces drag on the portion of the turbine moving in the 'upstream' direction and thus increases the efficiency of the turbine.

Contacting is defined as the vane being contacted being able to accept and translate all or a portion of the force of the moving liquid as the liquid flows on, at, or past the vane surface impinged on by the liquid.

Rotation may imply a full or partial revolution.

The liquid may be air, preferably atmospheric air, most preferably wind.

The liquid may be water, preferably in a watercourse or tidal waterway.

The rotation of the vanes may be continuous and in one direction. This has the advantage of simplifying the pattern of movement required to yield the greater -3 -efficiency. Accordingly, the gearing or other arrangements required for this movement are correspondingly simplified.

Thus the rotation of the vanes may be opposite to that of the first member. For example when the rotation of the first member is clockwise, the rotation of the vanes is anticlockwise (counter clockwise) and vice versa.

The axis of rotation of the vane may be parallel to the first axis of rotation. Such an arrangement has the advantage that a gear train linking the first member and the vanes can be substantially at right angles to the axis of rotation and therefore lessen or minimise mechanical losses, while simplifying both manufacturing of subcomponents and the overall construction process.

The first axis of rotation may be substantially vertical. The first axis of rotation may be substantially horizontal. Preferably, the first axis of rotation is substantially vertical. The first member may described as having two faces, one proximal to the primary mounting point of the turbine and one distal to the primary mounting point. Preferably, when the turbine is rotating, each face of the first member describes a plane that is orthogonal to the first axis of rotation.

A single or, preferably, a multiplicity of vanes may be mounted on the first member. Where a single vane is defined herein as being mounted on the first member the invention also encompasses 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15,16, 17, 18, 19, 20, 21, 22, 23, or 24 vanes being mounted on the first member. Preferably, 6 or 8 vanes are mounted on the first member. The vanes may be mounted on both faces of the first member. This has the advantage of increasing the surface area of the turbine on which the flow of liquid impinges and thus increasing the amount of energy that may be obtained from the flow of liquid.

The axis of rotation of vanes mounted on each face of the first member may be parallel with the first axis of rotation. Preferably, the vanes are mounted in pairs projecting from the opposite faces of the first member. Such an arrangement has the advantage of rotationally balancing the moving turbine and thus preventing or ameliorating undue -4 -movement or vibration. In this way the efficiency and service life of the turbine is improved.

Most preferably the pairs of vanes are mounted so that their axes of rotation are co-linear or parallel. Such an arrangement has the advantage of allowing the use of a gear train directly controlling the rotation of a single vane, e.g. projecting distally from the first member, to be used to directly control the rotation of a further vane. Thus one gear train may be used to control the rotation of more than one vane and thus increase the efficiency of use of the gear train, e.g. in terms of mechanical losses, over using separate, independent gear trains for each vane. Thus a pair of vanes may rotate in concert with greater efficiency than a single vane.

In addition, a pair of vanes projecting proximally and distally from the first member may be mounted on a common axle that is parallel to the first axis of rotation. Preferably such a common axle projects proximally and distally from the first member and has vanes mounted on both the proximal and distal portions. Such an arrangement has the benefit of simplifying the gearing controlling rotation of a pair of vanes.

The mounting points of the vanes may be equally spaced from the first axis of rotation. In addition, the mounting points of the vanes may be equally angularly spaced with respect to the first member. A multiplicity of vanes has the advantage of extracting additional energy from the flow of liquid. Furthermore, multiple vanes contribute to the rotational stability of the turbine in that symmetrically mounted vanes/blades will reduce the vibrational or asymmetric loads on a bearings supporting the first member and thus prolong the working life of the first member.

In the choice of the number of blades there exists a balance between a greater number of blades yielding better efficiency of extraction of energy from a flowing liquid versus a greater number of blades causing screening of other blades from the flow of liquid. Fewer than less than 6 blades has been found to be less efficient and must be an even number due to gearing. -5 -

Thus, turbines with 6 or 8 vanes/blades yields the advantage of efficient energy extraction without excessive screening of blades from the fluid flow.

Preferably, there are an even number of blades/vanes as this yields the advantage of less complex and more simply balanced gearing being required to linking the first member and the gears controlling the positions of the vanes.

Each of the vanes has a first face and a second face. Preferably the first and second faces are substantially parallel. Preferably the first and second faces are substantially identical.

The vanes may be flat or have a shaped profile. Preferably the vane is shaped to have a substantially sinusoidal longitudinal profile.

The axis of rotation of the vane may substantially coincide with the central longitudinal axis of the vane. The vanes may be arranged to have their axis or axes of rotation substantially parallel to the axis of rotation of the first member Vanes shaped with a non-planar profile, preferably a longitudinal profile, have been found to be more rigid. Thus larger vanes can be employed for a given weight of material comprised in the vane. Also, and unexpectedly vanes with such profiles are more efficient at capturing energy from the flow of liquid.

The vanes may be made of metal, plastics or composite material. The vanes may be produced by moulding, bending, extruding or other shaping processes.

The apparatus may be manufactured or produced in varying sizes. The amount of energy extracted from the moving liquid may be dependent on the size or scale of the apparatus. In general, a larger scale embodiment of apparatus will capture kinetic energy from the flow of liquid more efficiently and thus may yield a greater amount of electrical energy and/or mechanical work. In addition, this amount of electrical energy and/or mechanical work may be yielded more efficiently. Thus an apparatus of the invention may be produced to a scale to accommodate the application for which the apparatus is intended. For example, a large scale apparatus of the invention may be -6 -suitable for industrial use in a wind farm or hydro power installation. Similarly, a smaller or intermediate scale apparatus of the invention may be suitable for domestic and/or light industrial use.

The apparatus may comprise means for changing the rotational period of the vane so that at the start of the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is substantially perpendicular (90 degrees; orthogonal) to the direction of the flow of liquid.

The apparatus may comprise means for changing the rotational period of the vane so that halfway through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is substantially perpendicular (90 degrees; orthogonal) to the direction of the flow of liquid.

The apparatus may comprise means for changing the rotational period of the apparatus so that one quarter way through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is substantially parallel (0 degrees) to the direction of the flow of liquid.

The apparatus may comprise means for changing the rotational period of the apparatus so that one half way through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is substantially perpendicular (90 degrees; orthogonal) to the direction of the flow of liquid.

The apparatus may comprise means for changing the rotational period of the apparatus so that at three quarters through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is substantially parallel (0 degrees) to the direction of the flow of liquid.

The apparatus may comprise means for changing the rotational period of the apparatus so that at the one eighth point through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is 45 degrees to the direction of the flow of liquid. Thus the force transferred to the vane by the liquid impinging thereon will be directed substantially perpendicularly to the plane -7 -of the vane. Thus this force has radial and circumferential components with respect to the movement of the turbine. Preferably the circumferential component is in the direction of rotation of the turbine and contributes to the turning moment of the turbine.

The apparatus may comprise means for changing the rotational period of the apparatus so that at the three eighths point through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is 45 degrees to the direction of the flow of liquid. Thus the force transferred to the vane by the liquid impinging thereon will be directed substantially perpendicularly to the plane of the vane. Thus this force has radial and circumferential components with respect to the movement of the turbine. Preferably the circumferential component is in the direction of rotation of the turbine and contributes to the turning moment of the turbine.

The apparatus may comprise means for changing the rotational period of the apparatus so that at the five eighths point through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is 45 degrees to the direction of the flow of liquid. Thus the force transferred to the vane by the liquid impinging thereon will be directed substantially perpendicularly to the plane of the vane. Thus this force has radial and circumferential components with respect to the movement of the turbine. Preferably the circumferential component is in the direction of rotation of the turbine and contributes to the turning moment of the turbine.

The apparatus may comprise means for changing the rotational period of the apparatus so that at the seven eighths point through the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is 45 degrees to the direction of the flow of liquid. Thus the force transferred to the vane by the liquid impinging thereon will be directed substantially perpendicularly to the plane of the vane. Thus this force has radial and circumferential components with respect to the movement of the turbine. Preferably the circumferential component is in the direction of rotation of the turbine and contributes to the turning moment of the turbine.

The change to the initial position for the rotational period of the vane with respect to the period of rotation of the first member may be applied while the first member is rotating. This has the advantage of meaning that when the direction of the flow of -8 -liquid changes the period of rotation of the vanes can be adjusted to present the desired profile of the vanes to the flow of liquid. Preferably this adjustment is so that at least one vane is perpendicular to the flow of liquid as the turbine rotates and thus most efficiently receives energy from the flowing liquid.

Thus the vanes of the vertical axis turbine can be adjusted to modulate the amount of energy extracted from the flow of liquid impinging on the blades/vanes. Preferably the vanes of the vertical axis turbine are optimised to maximise the amount of energy extracted from the flow of liquid impinging on the vanes.

The changing of the initial position for the rotational period of the first member may be achieved in a number of ways, including but not limited to a weathervane (weathercock) that moves a gear or gear train according to the position of the weathercock and thus the direction of the wind. The flow of any liquid may be ascertained and used to adjust the rotational period of the first member in this way.

Alternatively, external means of measuring the direction of the flow of liquid can be used and the information on the wind direction can be used to move the gear or gear train according to the direction of the flow of liquid. Thus an electronic wind detection system that outputs a digital or analogue signal describing the wind direction can be used to set the position of the gear train. Preferably setting the position of the gear or gear train is achieved using an electric motor. More preferably, this electric motor is a stepper motor, which is, most preferably, controlled or driven by a microcontroller.

The movement of the gear or gear train may be used to set or adjust the position of a central gear (steering hub") from which the rotation of the vanes is controlled and thus adjust the start position of the rotational period of the first member and/or vane. The steering gear controls the rotational position of the steering hub and may be linked to an external input such as a weathervane or electronic wind detection system. Preferably movement of the steering gear is linked to the external input by way of a shaft with pinion gears on each end, one end of which preferably meshes with the steering gear. Preferably the steering gear has 24 teeth and the pinon gears have 12 teeth. -9 -

Preferably the central gear is a sun gear that shares its axis of rotation with the axis of rotation of the first member. More preferably, planetary gears meshing with the central sun gear transfer the rotational movement and position of the first member to the vanes of the turbine. Most preferably, the gear train between central sun gear and the vane comprises three gears: the first, central sun gearwheel; a planetary gearwheel; and a further gearwheel meshing with the planetary gearwheel that rotates with the blade/vane.

The gear ratios of the components of the gear train may be chosen to achieve the relative rotation rates of first member and vanes set out herein. Preferably the gear ratios of the sun gear (steering hub), planetary gearwheel (idler gear) and vane gearwheel are: - Steering Hub = 24T - Idler Gear = 100T - Vane gear = 48T.

In this way rotation of the first member leads, via the gear train, to rotation of the vane in the opposite direction, e.g. the first member rotates clockwise and the blades/vanes rotate anti-clockwise.

Preferably the central sun gear remains substantially stationary and movement of the position of the sun gear defines the initial point of the rotational period of the first member. This has the advantage of the turbine being directional and thus the amount of energy extracted from the flow of liquid can, advantageously, be modulated by directing the turbine 'into' or out of' the flow of liquid. Thus, the first member rotates around the sun gear (steering hub) which remains substantially static until a change in flow direction of the liquid occurs).

The speed at which a wind turbine -both horizontal-axis and vertical-axis -rotates must be controlled for efficient power generation and to keep the turbine components within design speed and torque limits. All wind turbines are designed for a maximum wind speed -often referred to as the "survival speed" -above which they will suffer mechanical damage. With respect to VAVVT's, electrical or mechanical brakes are -10 -often employed and used for slowing down the blade rotation as needed to prevent the turbine from exceeding its survival speed.

However, vertical axis wind turbines are normally omnidirectional. Thus the advantage of not needing to be set at the correct angle to the flow of liquid driving the turbine becomes a disadvantage when the turbine cannot shed the excess force of the flow of liquid that causes the turbine to exceed its survival speed.

Thus means for measuring the speed of the flow of liquid may be used to adjust the initial position of the rotational period of the first member. An anemometer is one such means.

Therefore for the directional turbines of the present invention exceeding the survival speed can be prevented and/or ameliorated by reducing the force brought to bear on the turbine blades or vanes by changing the initial position of the period of rotation of the first member so that the force of the liquid flowing past the blades/vanes is controlled. In this way, adjusting the position of the turbine so that its ability to extract energy from the moving flow of liquid is sub-optimal allows the turbine to be prevented from exceeding its survival speed.

Preferably, such an adjustment to prevent exceeding the survival speed is automatic. Most preferably this is achieved by supplying a further input of information, positional or electronic, to change the positions of the gear train defining the position of the blades/vanes.

The invention also provides a method for manufacturing a turbine of the invention.

The invention also provides for use of apparatus of the invention in generating electricity using a turbine of the invention wherein the kinetic energy of the movement of the turbine is used to drive an electrical generator. Preferably magnets mounted on the moving turbine move past stationary generator coils to yield an electrical current. Alternatively, the movement of the turbine may be transferred to separate electricity generating apparatus.

Examples and Description of the Drawings

The invention is now illustrated in the following specific embodiments with reference to the accompanying drawings showing:-Fig. 1 Shows a fixed-blade vertical axis wind turbine that extracts kinetic energy from wind by the wind impinging on the blades to generate a force that in turn generates a turning moment such that the turbine rotates with respect to the shaft on which it is mounted.

Fig. 2 Figure 2A is a diagram showing that the forces on the blade of a wind turbine are due to drag and/or lift. Figure 23 is a graph showing that for a given wind and blade area, the lift force is approximately 5x the drag force.

Fig. 3 Shows photographs of perspective views of a wind turbine of the invention with viewpoints above (Fig. 3A) and below (Fig. 3B) the horizontal plane of the blade carrier 104. Figs 3C and 3D show isometric diagrams from a viewpoint above the horizontal plane of the blade carrier 104. Fig. 3E shows a side view of the turbine. Fig. 3F shows an isometric diagram of a wind turbine of the invention from a viewpoint above the horizontal plane of the blade carrier 104 having two sets of blades: a first set of blades mounted above the blade carrier 104 and a second set below the blade carrier.

Fig. 4 Shows a photograph of a perspective views of a wind turbine of the invention from a viewpoint below the horizontal plane of the blade carrier 201.

Fig. 5 Shows an isometric view of a vane and mountings for use with the turbine of Fig. 4.

Fig. 6 Fig. 6A, 6B, 6C and Fig 6D show a schematic illustrations of the turbine rotating clockwise and the vanes rotating anticlockwise. The clockwise period of the rotation of the cover is 720 degrees (4 7 radians) and the period of the linked anticlockwise rotation of the blades is 360 degrees (2 rr radians). Figs 6A and 63 show a turbine with 8 vanes and Figs 6C and 6D show a turbine with 6 vanes. Figs 6A and 6C show the first revolution of the period and Figs 6B and 6D show the second revolution. The vanes are flat and identical on either face but are shown here with different shading only to illustrate the relative rate of rotation of the vanes as the body of turbine rotates. The dotted line marks the transition between revolutions.

-12 -Fig. 7 Shows a plan view of the layout and gearing of the central sun gear 701, meshing planetary gears 702 and further planetary gears 703 that move the vanes of the turbine.

Fig. 8 Fig. 8A shows a diagram of the lower portion of an assembled turbine including means for steering the direction of the turbine. The reference numerals referring to the components of the assembly are set out in the Table 1, below. Fig. 8B shows an isometric diagram of a wind turbine of the invention from a viewpoint above the horizontal plane of the blade carrier 104, which, for the purposes of clarity, is shown as being transparent in this diagram. Fig. 8B also shows an exploded view of the mounting of a blade 107 to the turbine including the positioning of gearwheel 703 that defines the rotation of the blade 107... Fig. 8C shows an isometric diagram of a wind turbine of the invention similar to that shown in Fig. 8B but having two sets of blades: a first set of blades mounted above the blade carrier 104 and a second set below the blade carrier.

Table 1: Reference numeral key for Fig. 8.

Reference Numeral Component 1 Mainshaft 2 Rotor hub 3 Cap Washer 4 Cover Cap Bearing Spacer 6 Bearing 20 x 47 x 14 7 Circlip 47 x 1.75 8 Socket CSK Screw M8 x 20 9 Bearing Spacer Hub Pinion 11 Bearing Spacer 12 Socket CSK Screw M5 x 12 13 Top plate 14 Idler gear Bearing 10 x 26 x 8 16 Idler shaft -13 -Reference Numeral Component 17 Bearing cover 18 Pillar 19 Bearing cover Blade shaft 21 Blade gear 22 Lower plate 23 Blade hub 24 Steering Pinon Steering shaft 26 Steering bearing housing 27 Key 10 x 8 x25LG 28 Alternator Mounting Plate 29 Alternator Mounting Hub Steering gear hub 31 SKT cap screw M6 x 10 32 Key 3sq x 9 LG 33 Washer 05 34 SKT cap screw M5 x 10 Blade assembly 36 Steering vane 37 Socket cap screw M4 x 10 38 Washer 05 39 V ring seal 020 Fig. 9 Figs 9A-9H show power curves for eight datasets obtained from the turbine of Example 1.

Fig. 10 Figs 10A-10D show power curves for 4 datasets obtained from the turbine of Example 2.

Fig. 11 Diagram of a Wheatstone bridge.

The invention is now demonstrated in the following specific examples.

-14 -

Examples

Example 1

Figure 3 shows a vertical axis wind turbine comprising the components listed below: - A substantially vertical mounting pole 101.

- A weathervane 102 rotates around the mounting pole comprising a substantially straight rod or tube extending radially from the longitudinal axis of the mounting pole and having a substantially flat vane mounted on the distal end of the rod or tube that also extends radially from the longitudinal axis of the mounting pole.

- Above the weathervane assembly is a white plastic block 103 which remains stationary with respect to the pole. It is from this part that the cable carrying the electricity generated issues from.

- 104 is a lozenge shaped circular cover on which the bearings for the turbine vanes are mounted.

- The outer underside of the circular cover 105 on which the turbine vanes are mounted houses 50 generator magnets. In addition, there are generator coils fixed to the hub to provide a stator portion 108 of an electrical generator, which is mounted on the mounting pole. The cover 105 rotates with respect to the generator magnets and hub. This wind turbine has 36 magnets and a single generator coil but up to 36 coils may be installed.

- The six identical blades or vanes 107 are mounted perpendicular to the plane of the circular cover, equally radially offset from the centre of rotation of the circular cover and evenly spaced are mounted six vanes 107 which are able to rotate about an axis parallel to the longitudinal axis of the mounting pole. The vane/blade 107 is substantially rectangular with rounded corners. The vane/blade 107 is flat and thus does not have an aerofoil cross section and thus does not be generate any lift force.

- The assembly is supported on bearings that allow it to rotate as shown in Fig 8. Similarly the vanes are supported by bearings as shown in Fig. B. In operation the flow of wind impinging on the surfaces of the vanes 107 causes the assembly to rotate. Viewed from above, the apparatus rotates in a clockwise direction.

-15 -During each rotation caused by the wind flowing past the vanes of the turbine the blades are subjected to lift and drag forces as illustrated in Fig. 2. These forces vary with each rotation according to the position of the vane with respect to the wind direction as it rotates.

As the apparatus is made to rotate, a gear train linking the vanes to the rotational position of the assembly on which they are mounted causes the blades to rotate along with and relative to the cover.

When viewed from above the cover rotates clockwise and the vanes rotate anticlockwise. This is shown schematically in Fig. 6A and Fig 6B. The clockwise period of the rotation of the cover is 720 degrees (4-rr radians) and the period of the linked anticlockwise rotation of the blades is 360 degrees (2-rr radians). Fig.6A shows the first revolution of the period and Fig. 63 shows the second revolution. The vanes are flat and identical on either face but are shown here with different shading only to illustrate the relative rate of rotation of the vanes as the body of turbine rotates. The dotted line marks the transition between revolutions.

Thus, the blade/vane 601, is flat to the direction of the wind and creates a turning moment. In contrast the blade/vane 603 is at a different stage of the cycle and is edge on to the wind to minimise drag and turning moment counter to that being simultaneously generated by the wind impinging on 601. The blades/vanes at positions 602 and 604 are in positions intermediate between positions 601 and 603. The blades/vanes of 602 and 604 are at 45 degrees (0.5-rr radians) to the wind direction. However the moment generated by the wind impinging on 602 and 604 is perpendicular to the plane of the blade/vane and will thus have a rotational component being the cosine of the angle of the vane to the wind. For both vanes in positions 602 and 604 this moment will be in the direction of rotation of the apparatus.

Linking the rotation of the body of the turbine to the rotation of the vanes is achieved by the use of a substantially stationary sun gear 701 concentric with the central axis of rotation. About the sun gear rotate three planetary gears 702 that are attached to the body of the turbine. Rotation of the turbine causes the planetary gears 702 meshed with the stationary sun gear to rotate. Further gears arranged radially out from the -16 -central axis and meshing with the planetary gears 703 are linked to the vanes and cause them to rotate in concert with the body of the turbine, but in the opposite direction.

Thus the 'direction' of the wind turbine can be defined by movement of the central sun gear. The weathercock is linked to a gear train that changes the position of the central sun gear 701 to achieve this.

Electrical energy is generated by movement of the magnets in the rotating cover section moving relative to the generator coils in the stationary part of the assembly.

Example 2

Figure 4 shows a vertical axis wind turbine comprising the components listed below: - A substantially vertical mounting pole 201.

- A weathervane 202 rotates around the mounting pole comprising a substantially straight rod or tube extending radially from the longitudinal axis of the mounting pole and having a substantially flat vane mounted on the distal end of the rod or tube that also extends radially from the longitudinal axis of the mounting pole.

- a circular base plate 204 on which the bearings for the lower ends of the turbine vanes are mounted.

- an annular top plate 209 on which the bearings for the upper ends of the turbine vanes are mounted.

- The outer underside of the circular cover 204 on which the turbine vanes are mounted houses 50 generator magnets. In addition, there are coils fixed to the hub 204 that is mounted on the mounting pole. The base plate 204 rotates with respect to the generator magnets and hub. This wind turbine has 36 magnets and a single generator coil but up to 36 coils may be installed.

- The six identical blades or vanes 207 are mounted perpendicular to the plane of the circular cover, equally radially offset from the centre of rotation of the circular cover and evenly spaced are mounted six vanes 207 which are able to rotate about an axis parallel to the longitudinal axis of the mounting pole. The vane/blade 207 is substantially rectangular with a substantially sinusoidal longitudinal profile 208 as shown in Fig. 5. Thus the 'front' and 'back' faces of the vane are identical. The vanes are arranged so that at the start of the rotational period a 'trough' of the -17 -sinusoidal is located both at the outermost on the apparatus and facing into the wind in order to catch the wind. The vane/blade 107 is does not have an aerofoil cross section and thus does not be generate any lift force.

-The assembly is supported on bearings that allow it to rotate as shown in Fig B. Similarly the vanes are supported by bearings as shown in Fig. B. In operation the flow of wind impinging on the surfaces of the vanes 207 causes the assembly to rotate. Viewed from above, the apparatus rotates in a clockwise direction.

During each rotation caused by the wind flowing past the vanes of the turbine the blades are subjected to lift and drag forces as illustrated in Fig. 2. These forces vary with each rotation according to the position of the vane with respect to the wind direction as it rotates.

When viewed from above the cover rotates clockwise and the vanes rotate anticlockwise. This is shown schematically in Fig. 6A and Fig 6B. The clockwise period of the rotation of the cover is 720 degrees (4-rr radians) and the period of the linked anticlockwise rotation of the blades is 360 degrees (27 radians). Fig.6A shows the first revolution of the period and Fig. 6B shows the second revolution. The vanes are flat and identical on either face but are shown here with different shading only to illustrate the relative rate of rotation of the vanes as the body of turbine rotates. The dotted line marks the transition between revolutions.

Thus, the blade/vane 601, is flat to the direction of the wind and creates a turning moment. In contrast the blade/vane 603 is at a different stage of the cycle and is edge on to the wind to minimise drag and turning moment counter to that being simultaneously generated by the wind impinging on 601. The blades/vanes at positions 602 and 604 are in positions intermediate between positions 601 and 603. The blades/vanes of 602 and 604 are at 45 degrees (0.57 radians) to the wind direction. However the moment generated by the wind impinging on 602 and 604 is -18 -perpendicular to the plane of the blade/vane and will thus have a rotational component being the cosine of the angle of the vane to the wind. For both vanes in positions 602 and 604 this moment will be in the direction of rotation of the apparatus.

Linking the rotation of the body of the turbine to the rotation of the vanes is achieved by the use of a substantially stationary sun gear 701 concentric with the central axis of rotation. About the sun gear rotate three planetary gears 702 that are attached to the body of the turbine. Rotation of the turbine causes the planetary gears 702 meshed with the stationary sun gear to rotate. Further gears arranged radially out from the central axis and meshing with the planetary gears 703 are linked to the vanes and cause them to rotate in concert with the body of the turbine, but in the opposite direction.

Example 3

The efficiency of the wind turbines discussed in Examples 1 and 2 calculated by recording the amount of electricity generated using a picologger and its associated software in terms of a quantity of fluid (wind or water) Q m3 passing through a cross section area A m2 at a velocity U m/s. The values for the amount or electricity generated were saved in electronic format at a sample rate of 1 per minute as a comma-separated value and then linear correlation analysis was used to characterize the data.

The rows with no data in the power channel were removed from the data file and then a U versus V graph was drawn, and axes and labels added. The data were then subjected to regression analyses using a power function and an exponential function as shown in Figure 6.5 The resulting coefficients, powers and R2 were recorded and tabulated. Linear correlation analysis was used to characterize the data -19 -The resulting power curves for eight datasets for the turbine of Example 1 are shown in Figs 9A-9H. The analysis of these data are set out in Table 2, below.

Exponential, Power and Linear correlation equations were determined for each data set of the form: Exponential P=AeBu PowerP=CUD LinearP=E U+F Where A, B, C, D, E and F are the empirical calibration coefficients for the turbine, P is the power output and U is the corresponding wind speed. The results are summarised in the Table below and lead to the uncalibrated power curves. Although the correlation coefficients are similar across the three analyses, favourable R2 values are obtained for the linear correlations of datasets 1, 2 and 3. For mean values the following parameters are calculated: Linear P = 4921 and U -35.33.

Table 2 -Analysis of the Power Output of the Turbine of Example 1.

Dataset Data points A e e2 c D fe E F fe 01 SOO 7x10-'24 38560 0.4098 2x10308 281.11 0.4094 5781 -42.00 0.3968 02 500 2x10-m5 32761 0.3899 2x10308 238.66 0.3895 5395 -39.15 0.3816 03 300 4x10-32 9754 0.2527 6x10144 67.966 0.2442 3589 -25.47 0.3203 04 SOO 2x10-°8 2189 0.0675 4x1035 16.957 0.0708 1112 -7.66 0.1740 500 3x10-°9 2456 0.065 2x1039 18.721 0.0672 1082 -7.532 0.1537 06 500 1x10-°9 2566 0.0684 1x1041 19.594 0.0709 1084 -7.851 0.1520 07 500 2x10-°9 2472 0.0674 2x1039 18.769 0.0696 1043 -7.251 0.1498 08 SOO 2x10-°9 2474 0.0674 2x1039 18.783 0.0696 1045 -7.265 0.1501 Mean 01 -03 4921 -35.33 0.3662 Four observations are made with respect to these data There is a distinct difference between datasets 1-3 and 4-8.

H. The R2 values are reasonable in 1-3 but very low in 4-8.

There is a large difference in A, B, C and Din 1-3, but little difference in 3-8 -20 -The values for A are very small and the values for C are very large. This is thought to be a factor of the mV scale. Therefore datasets 1 to 3 are taken forward for further analysis Thus the linear equation above for the Turbine of Example 1 was then used with wind speeds of 4 m/s and 8 m/s giving (uncalibrated) outputs of 19,468 and 39,332 respectively.

The power curves for datasets for the turbine of Example 2 are shown in Figs 10A-10D. The analysis of these data are set out in Table 3, below. Linear correlation analysis was used to characterize the data by the method given above.

Table 3 -Analysis of the Power Output of the Turbine of Example 2.

Dataset Pts A B R2 C D R2 E F R2 500 540-98 31.396 0.339 9x10-196 228.47 0.3384 8378 -61 0.4615 11 500 0.0401 1.8763 0.061 0.1988 0.858 0.3895 0.406 -0.009 0.0809 Where A, B, C, D, E and F are the empirical calibration coefficients for the turbine, P is the power output and U is the corresponding wind speed. The results are summarised in the Table above and lead to the uncalibrated power curves. For mean values the following parameters are calculated: Linear P = 8378 U-61.

Four observations are made with respect to these data: There is a distinct difference between datasets 10 and 11.

H. The R2 values are reasonable in 10 but low in 11 Hi. The values for A and C are very small in 10. The final analysis only used the dataset 10 data The linear calibration equations above were then run with wind speeds of 4 m/s and 8 m/s giving (uncalibrated) outputs for the Turbine of Example 2 of: at wind speed 4 m/s, output is 33,451 and at 8 m/s is 66,963 Since the two calibration equations for the turbines of Examples 1 and 2 are linear, then the two values of coefficient E can be expressed as a percentage increase from -21 -about 4921 to about 8378 which is equivalent to about 70% improvement in power generated with the "Example 2" turbine in comparison with the "Example 1" turbine.

The wind speed measuring anemometer was calibrated by noting wind speed on a separate anemometer in comparison with the anemometer output voltage. Logging voltage in mV versus the wind speed in m/s yielded the calibration equation where U is the wind speed (m/s) and Vu is the anemometer voltage (mV). The resulting calibration equation is: U = 0.006 Vu -042 The power output was calibrated using a two-stage process. Firstly, the logged voltage is increased to the input voltage of the picologger (maximum 5V) using a Wheatstone bridge resulting in the calibration equation: Vp = 0.1708 VI Where Vp is the voltage used in the output power calculation (Po = Vp / I) where Vi is the input voltage and VP is the Picologger voltage. Thus, logged voltages were divided by 0.1708.

Secondly, the logged power voltage was then corrected according to the configuration of the Wheatstone bridge (Fig. 11) used to determine the current and then utilise P0 = Vp I, where I is the bridge current.

VOUT = VC -VD VC = (R2 Vs) / (Ri + R2) VD = (R4 Vs) / (R3 + R4) Referring to Fig. 11, in the present system R1=240 0; R2=25 0; R3=320 0; and R4=120 0.

Thus Vs = (25 Vs) / 245 = 0.1020 Vs and VD = (120 Vs) / 440 = 0.272 Vs Thus: calculated Output Voltage = 0.1708 Input Voltage.

Furthermore, from the empirical data the correction factor is 0.17839, which is an acceptable difference.

-22 -These three calibration equations were applied to the data giving, for example, power outputs of 1.715 W and 2.915 W respectively for the turbines of Examples 1 and 2, respectively.

Thus, for Vo = 3V, and with reference to the power curves for the turbine of Example 1, the power output is: Po = V x I = 16.82 x 0.1 02 = 1.715 Watts Similarly, for the turbine of Example 2 using the 70% improvement discussed earlier, the power output is approximately: Po = 1.7 x 1.715 = 2.915 Watts.

These results can be compared with a theoretical determination using the cubic power law Po = Cp 1/2 pA U3 Where Po is the power output in W, Co is the non-dimensional wind power coefficient (taken as about 0.1 and 0.17), p is the density of the air (taken as 2 kg/m3), A is the device cross sectional area (taken as 0.5 m2) and U is the wind speed (4 m/s). With these values, the theoretical power for the turbines of Examples 1 and 2 are respectively approximately 3.2 W and 5.4 W, which is in line with the empirical results above.

Thus the apparatus is in the form of an improved turbine for extracting kinetic energy from flowing liquid.

Claims

-23 -Claims 1 An apparatus for mounting in a flow of liquid comprising: a) a first member, which is rotatable about a first axis of rotation; and b) one or more vanes, wherein the vane or each of the vanes for contacting the liquid is: (i) mounted on the first member; and (H) rotatable with respect to the first member; and wherein (Hi) the mounting point of the vane is radially spaced away from the first axis of rotation, wherein the vane mounted on the first member rotates relative to the first rotating member and the rotational position of the vane is defined by the rotational position of the first rotating member such that such that as the first member rotates in a first direction the vane or vanes each rotate in proportion to this movement in the opposite direction.
2. An apparatus according to claim 1, wherein the vane or vanes each rotate in direct proportion to the rotation of the first member in the opposite direction.
3 An apparatus according to claim 1 or claim 2, wherein the first member rotates with a period of 720 degrees (4-rr radians) and as it does so the vane or vanes each rotate through 360 degrees (2-rr radians).
4. An apparatus according to any preceding claim, wherein the vane or vanes are subject to drag forces with respect to the flow of liquid as the flow of liquid impinges thereon.
5. An apparatus according to any preceding claim, wherein the vane or vanes do not generate hydrodynamic lift from the flow of liquid.
6. An apparatus according to any preceding claim, wherein the moving liquid is air, preferably wind.
7. An apparatus according to any of claims 1 to 5, wherein the moving liquid is water, preferably in a watercourse or tidal waterway.
-24 - 8. An apparatus according to any preceding claim, wherein the rotation of the vanes is continuous and in one direction.
9. An apparatus according to any preceding claim, wherein the axis of rotation of the vane is parallel to the first axis of rotation.
An apparatus according to any preceding claim, wherein a multiplicity of vanes is mounted on the first member, preferably, six or eight vanes are mounted on the first member.
11. An apparatus according to any preceding claim, wherein the vane has a first face and a second face that are substantially identical.
12. An apparatus according to any preceding claim, wherein the vane has a shaped profile
13.An apparatus according to any preceding claim, wherein the vane has a substantially sinusoidal longitudinal profile.
14. An apparatus according to any preceding claim, wherein the apparatus comprises means for changing the rotational period of the vane so that at the start of the rotational period of the first member the vane is at a defined angle to the flow of liquid, preferably this angle is substantially perpendicular to the direction of the flow of liquid.
15. An apparatus according to claim 14, wherein the change to the initial position for the rotational period of the vane with respect to the period of rotation of the first member is made while the first member is rotating.
16. An apparatus according to claim 14 or claim 15, wherein the initial position for the rotational period of the vane with respect to the period of rotation of the first member is defined by the position of a sun gear.-25 -
17. An apparatus according to claim 16, wherein the means for changing the rotational period of the vane is a weathercock causing rotation of the sun gear according to the direction of the flow of liquid
18. An apparatus according to claim 16 or claim 17, wherein the sun gear meshes with one or more planetary gears that also mesh with the gearwheels defining the rotation of the vanes.
19. An apparatus according to claim 17 or claim 18, wherein the means for changing the rotational period of the vane is an anemometer causing rotation of the sun gear according to the speed of the flow of liquid.
20.A method for manufacturing the apparatus of claims 1 to 19.
21. Use of the apparatus of claims 1 to 19 for generating electricity.