GB2450902A

GB2450902A - Controlled wing for power generation from flowing fluid

Info

Publication number: GB2450902A
Application number: GB0713437A
Authority: GB
Inventors: Brian Trim
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-07-11
Filing date: 2007-07-11
Publication date: 2009-01-14
Anticipated expiration: 2027-07-11
Also published as: GB0713437D0; GB2450902B

Abstract

A vane 106 for generating electricity from flowing fluid (water or wind) comprises a wing 108, spaced from the vane 106 for interacting with the fluid flow stream and generating thrust. A hydraulic actuator 110 orientates the wing relative to the vane to optimize the thrust generated by the wing 108. The vane 106 is connected, via a support body, to an endless cable which drives the generator.

Description

ELECTRICITY GENERATING INSTALLATION

The generation of electricity from the flow of water or tides has been known for a long time. The simplest generating system for tidal plants involves a dam, known as a barrage across an estuary. Sluice gates on the barrage allow the tidal basin to fill on the incoming high tides and to exit through the turbine system on the outgoing tide.

Alternatively, flood-generating systems, which generate power from the incoming tide are possible.

Several different turbine configurations are possible. In systems with a bulb turbine, water flows around the turbine. Consequently, maintenance of the turbine is difficult, as the water must be prevented from flowing past the turbine to enable access thereto.

Tidal fences represent another example of an installation for generating electricity from the flow of water. Tidal fences are composed of individual, vertical axis turbines which are mounted within the fence structure, known as a caisson, and they can be thought of as giant turn-styles which completely block a channel, forcing all of the water through them. Unlike barrage tidal power stations, tidal fences can also be used in unconfined basins, such as in the channel between the mainland and a nearby offshore island, or between two islands. As a result, tidal fences have much less impact on the environment than barrages, as they do not require flooding of the basin and are significantly cheaper to install. Tidal fences also have the advantage of being able to generate electricity once the initial modules are installed, rather than after complete installation as in the case of barrage technologies. However, tidal fences are also difficult to maintain as the electricity generating equipment is located underwater.

It is therefore desirable to provide an alternative means for generating electricity which has lower impact on the environment and provides simple, accessible maintenance.

According to one aspect, the present invention provides a vane for driving electricity generating means, the vane comprising: a vane body for receiving a support means which is coupled to electricity generating means; a wing, spaced from the vane body, for interacting with a fluid flow stream in which the vane is located and generating thrust therefrom; and an orientation means connected between the wing and the vane body, for interacting with the fluid flow stream and thereby orientating the vane about the support means to optimise thrust generation by the wing.

By providing a vane having an orientation means contained therein, an adaptable, wieldy installation for generating electricity from a fluid flow stream can be achieved.

Generation of electricity can occur at any time when a current is present in the fluid flow stream, irrespective of the incident direction of that flow stream. No additional directing means is required to maintain the aspect of the vane with respect to the fluid flow stream as the orientation means achieves this, dependant on the local fluid flow characteristics. Consequently, obstruction within the fluid flow stream is minimised and any variation in current direction is automatically tracked by the vane such that the maximum impact of the fluid on the wing of the vane is maintained.

The orientation means may be a rigid pylon which may be connected to the vane body and the wing and located therebetween for orientating the vane substantially orthogonally to the fluid flow stream. The wing may be pivotally connected at a leading edge thereof to the pylon to enable relative rotational movement between the wing and the pylon. The vane may further comprise an extendable member (e.g. a hydraulic rod), fixed between a trailing portion of the wing and the pylon to adjust the degree of rotational movement between the pylon and the wing.

The vane may comprise a controller for controlling the degree of rotational movement between the pylon and the wing together with an internal power supply, such as a rechargeable battery, for powering the controller and/or any hydraulics relating to the extendable member. The vane may comprise a sensor for detecting a parameter relating to the fluid flow stream, such as flow rate and/or flow direction. The controller may be configured to receive a signal, indicative of the detected parameter, from the sensor and to adjust the degree of rotational movement between the pylon and the wing dependent upon this detected parameter.

The pylon may be pivotally connected to the vane body to enable relative rotational movement therebetween. The pylon may comprise a clamping member which protrudes through an aperture in the vane body, whereby the clamping member may engage with a flexible support means located within the vane body when the wing experiences a loading condition.

The wing may have an aerofoil cross section or it may have a parallel cross section and it may be of dihedral form. The wing and/or the pylon may comprise a sealed cavity to increase the buoyancy of the vane. The vane may comprise a rudder for adjusting the vertical location of the vane.

An installation for generating electricity from a fluid flow stream may be provided, the installation comprising: a flexible support means, driveably connected to a generator; and a vane as previously described, mounted on the flexible support means and configured to interact with the fluid flow stream and be driven therethrough by fluid forces exerted on the vane, whereby the vane displaces the support means and thus causes the generator to generate electricity.

The vane is configured to be driven through the flow stream any time that fluid forces are exerted thereon. The consequential displacement of the support means causes the generator to generate electricity whenever fluid forces are exerted on the vane.

The presence of vanes mounted on a flexible support means rather than unmoving solid structures represented by the prior art results in a significantly more environmentally friendly installation that has minimal impact on the underwater environment including the sea or river bed. Furthermore, minimal obstruction is presented to shipping or other vessels which use the body of water.

The flexible support means may be made of metal, for example stainless steel, alternatively it may be made of a plastics material. The flexible support means may be a cable or it may be a chain.

The vane may be removably mounted on the flexible support means. Thus, maintenance of the vane can occur remotely from the installation whilst the installation continues to operate. This is particularly beneficial when the installation is located in a body of water as the accessibility of the vane becomes more difficult in these circumstances.

The installation may comprise a plurality of vanes and each vane may be mounted on the support means substantially equidistant from one another.

The installation may comprise two end stations, each end station may comprise a pulley arrangement for suspending the flexible support means between respective end stations. Each pulley arrangement may comprise a guide means for guiding the flexible support means in to and out of the end station and a feed pulley for redirecting the flexible support means from one side of the end station to the other.

The guide means may be provided by a single guide pulley or it may be provided by a plurality of guide pulleys located within a housing component.

At least one of the pulley arrangements may comprise a tensioning pulley for raising or lowering the flexible support means by adjusting the tension therein. Each pulley arrangement may comprise a generating pulley coupled to a generator for generating electricity from any displacement of the flexible support means. The generating pulley may also be a driving pulley for driving the flexible support means around the installation.

One or more stops may be provided, attached to the flexible support means to restrict movement of the, or each, vane along the support means. The, or each, stop may comprise a shock absorber. The, or each, vane body may comprise a shock absorber.

The fluid flow stream may be a body of water, for example, a river, an estuary, coastal waters or offshore waters. Alternatively, the fluid flow stream may be an air flow stream.

According to a second aspect, the present invention provides a method of generating electricity from a fluid flow stream comprising the steps of: suspending a single cable within the fluid flow stream; mounting a vane on the cable such that it interacts with the fluid flow stream and is driven therethrough by fluid forces exerted on the vane; and driveably connecting the cable to a generator, whereby the vane displaces the cable and thus causes the generator to generate electricity.

The method may further comprise the steps of: sensing fluid flow parameters to determine the current fluid flow conditions; calculating the cumulative loading on the installation; determining the number of vanes that can be supported by the installation; and mounting this number of vanes on the cable to generate a maximum quantity of energy for the current fluid flow conditions.

The method may comprise the following steps: sensing fluid flow parameters local to the vane to determine the local current fluid flow conditions; calculating an optimum pitch angle for a wing of the vane; and adjusting the pitch angle of the wing accordingly.

The invention will now be disclosed with respect to the accompanying drawings in which: Figure 1 is a schematic plan view of an installation for generating electricity; Figure 2 is a side view of the installation shown in Figure 1; Figure 3 is an isometric view of a vane used in the installation of Figure 1; Figure 4 is an end view of the vane of Figure 3; Figure 5 is a side view of the vane of Figures 3 and 4; Figure 6 is side view of an alternative vane; Figure 7 is a detailed plan view of the end station shown in the installation of Figure 1; Figure 8 is a side view of a receiving portion of the station shown in Figure 6; Figure 9 is a side view of a dispatching portion of the station shown in Figure 6; Figure 10 is a side view of an alternative dispatch portion of an end station; Figure 11 is a plan view of a second example of an installation for generating electricity; Figure 12 is a plan view of a third example of an installation for generating electricity; Figure 13 is a plan view of a fourth example of an installation for generating electricity; and Figure 14 is a plan view of a fifth example of an installation for generating electricity.

Figure 1 illustrates an installation for harnessing kinetic energy from a fluid flow stream and for converting that energy into a more usable form such as electricity. As illustrated, the installation comprises a single continuous loop of cable 10, supported at end stations 20 across a span of a fluid flow stream, in this example a river, 30. A plurality of vanes 40 are mounted upon the cable 10, which acts as a support means thereto, and are each configured so that they interact with the fluid flow stream and are driven thereby. In particular, the vanes 40 are so configured that, whatever the predominant direction of fluid flow 50 the net force on the vanes is such that the cable 10 is always driven in the same direction (here shown by arrows 60).

As the tide ebbs and flows, the cable 10 assumes a different curved path within the water. As illustrated, the cable 10 is carried with the bulk flow of the water, the extent to which the cable 10 is carried downstream being determined by the strength of the current at that time. During a stand at high or low water there is very little water movement and the cable 10 simply hangs in a line (when viewed from above) between the end stations 20.

The cable 10, carrying vanes 40, is guided under the free surface of the river 30 and is conveyed at an appropriate height determined by the level of tension in the cable 10. This tension, and therefore the height, can be modified to suit any environmental parameters. For example, it may be desirable to minimise any interaction with the river bed to minimise any environmental impact that the installation may have thereon, alternatively it may be necessary to lower the cable 10, either permanently or temporarily, to permit vessels to pass along the surface of the river 30 without becoming entangled with the cable 10.

As shown in Figures 3, 4 and 5, each vane 40 comprises a wing 100 which is pivotally mounted about pivot point 102 at a mid-span portion of a leading edge 104 thereof to a rigid pylon 106. A central portion of the trailing edge 108 is connected to the pylon 106 using a hydraulic rod 110. Actuation of the hydraulic rod 110 enables a pitch a of the wing 100 to be altered to enable the aerodynamic and loading characteristics of the vane 40 to be modified. The hydraulic rod 110 is attached to the wing 100 using a shear bolt 111. If the loading of the wing 100 becomes excessive the shear bolt 111 fails, the pitch a of the wing 100 rapidly increases and the vane 40 de-powers so that the loads are dissipated. If the installation is used within a body of water having weak currents the shear bolt 111 may not be necessary. Furthermore, the shear bolt 111 may be replaced by a releasable connection device which simply releases the wing 100 when excessive loading thereof is experienced. The releasable connection may then be reconnected or reset without the need for replacement of any components as may be required subsequent to the failure of a shear bolt 111.

The wing 100 may have an aerofoil cross section as illustrated or alternatively may be represented by a flat plate. In the illustrated example, the wing 100 has a dihedral form to enhance stability of the rolling motion (i.e. motion around a longitudinal axis) of the vane 40.

The rigid pylon 106 is substantially two-dimensional and is connected to the wing 100 at a mid-span thereof. The pylon 106 is mounted orthogonally to the mid-span portion of the wing 100 and provides an orthogonal surface upon which the prevailing current can act thus assisting in positioning of the vane 40 during operation of the installation. The pylon 106 is connected to a vane body 112. The vane body 112 comprises a substantially tubular sheath 114 having a rigid fin 116 connected thereto. The pylon 106 is pivotally mounted, as illustrated, via pivot point 118 to the fin 116.

The vane body 112 is configured to be removeably connected to cable 10 and enables forces exerted on the wing 100 to be transmitted from the vane 40 to the cable 10. Two sets of needle bearings 120, 122 are mounted within the sheath 114 and provide contact with the cable 10. Each set of needle bearings are mounted longitudinally as shown in Figure 5 to enable rotational freedom of the vane 40 about a central longitudinal axis 124 of the cable 10. However, relative longitudinal displacement between the vane body 112 and the cable 10 is inhibited due to friction between the cable 10 and the needle bearings 120, 122.

Tubular sheath 114 is formed from two sheath components 126, 128. As illustrated in Figure 4, a hinge 130 is provided between these two sheath components 126, 128 to enable the vane body 112 to be opened to receive cable 10 and be clamped thereto. Once the cable 10 has been received by the first sheath component 126, the second sheath component 128 is rotated towards the first sheath component 126 to substantially enclose the cable 10. Sheath component 128 is then locked in this rotated position in order to secure the vane body 112 to the cable 10 located therewithin.

An additional clamping mechanism 132 is provided to further inhibit any relative longitudinal movement between the vane 40 and the cable 10 when the vane 40 is in a loaded condition. A portion of pylon 106 protrudes through an aperture in the first sheath component 126 and comes into contact with cable 10. A clamping member 134 is provided on pylon 106 adjacent to the cable 10. When the wing 100 is loaded, the pylon 106 rotates about pivot point 118 relative to fin 116, and clamping member 134 is urged into cable 10 to increase the friction therebetween. As the loading on the wing 100 increases, so does the level of friction between the clamping member 134 and the cable 10 so that the transmission of loading from the vane 40 to the cable 10 is enhanced.

Additional means for preventing relative longitudinal displacement between the vane 40 and the cable 10 may be provided. For example, stops (not shown) could be fixed to the cable 10 either side of the vane 40 to limit any longitudinal movement that may occur. The stops may comprise shock absorbers to dampen any impulse loading experienced thereby, alternatively, the shock absorbers may be located at either end (or both ends) of the tubular sheath 114. The stops also serve to retain vanes 40 on the cable 10 if a failure of the cable 10 occurs.

As discussed above, the pitch a of the wing 100 can be altered using the hydraulic rod 110. The main benefit of this variation in profile, and therefore aerodynamic characteristics, of the vane 40 is to harness the greatest level of energy from the fluid flow stream 30. In a small, low-cost installation it is desirable to reduce the complexity of the vanes 40. The wing 100 may, therefore, be fixedly connected to the pylon 106, preferably using a shear bolt to avoid damage of the vane 40 and the rest of the installation if increased loading conditions occur. Such a configuration is particularly suitable for an installation located in a river or a stream.

If the vane 40 comprises a hydraulic rod 110, the pitch angle a of the wing 100 may be set at a single value across the entire span of the installation dependent on the prevailing fluid flow conditions at that time. Adjustment of the pitch angle a may be carried out when the vane 40 passes through an end station 20. This embodiment is particularly suitable for tidal installations such as coastal or estuary locations.

In a more sophisticated installation, a controller may be located within the pylon 106 of the vane 40 together with a rechargeable battery. The controller can be used to change the pitch angle a of the wing 100 across the span of the installation using an algorithm which depends on the distance the vane 40 has travelled across the span of the installation. In this way changes in orientation experienced by the vane 40 due to the curved path of the cable 10 across the span of the installation can be accommodated and the quantity of energy harnessed from the flow stream can be optimised. This embodiment is particularly suitable for predictable flows, for example those found in coastal or estuary locations.

Furthermore, sensors (for example strain gauges) may be provided on surfaces of the vane 40 so that local variations in parameters relating to local flow conditions can be detected. Signals indicative of these parameters can be passed to the on-board controller located in the pylon 106 and used by the controller to determine the most appropriate pitch angle a for the wing 100 at that instant. This angle a is then effected by actuation of the hydraulic rod 110. This configuration is particularly useful to optimise energy harnessing in offshore locations where the span of the installation (i.e. the distance between the end stations 20) may be of the order one mile and many local variations in flow conditions may be experienced.

Additional directional control of the vane 40 may be achieved to maintain a particular depth of the vane 40 by including a rudder 140 as illustrated in Figure 6. Rudder 140 is pivotally connected to the pylon 106 and may comprise a weighted mechanical lever, operated by gravity and therefore determined by the overall orientation of the vane 40. Alternatively, the angle of the rudder 140 could be continuously controlled by the internal controller of the vane 40 dependent on the present depth of the vane 40. In order to determine the present depth, depth gauges 142 are provided on the vane 40, here located on the pylon 106. Depth gauges 142 send signals indicative of the current depth below the surface of the water and/or distance to the river or sea bed to the controller. The controller then determines an appropriate angle for the rudder 140 and makes the appropriate adjustment.

Turning now to Figures 7, 8 and 9, further details of the end stations 20 are illustrated. Cable 10 enters the end station 20 in a receiving portion of the station (represented in Figure 8). The cable 10 is conveyed around the station and leaves the end station 20 from a dispatching portion of the station (represented in Figure 9).

Each end station 20 comprises a number of pulleys which serve to direct and tension the cable 10. Receiving and dispatching guide pulleys 200, 202 lie in a vertical plane and are provided to receive cable 10 from the fluid flow stream into the end station 20 and to dispatch cable 10 from the end station 20 into the fluid flow stream. The guide pulleys 200, 202 are cantilevered from the end station 20 so that they may each pivot freely around a vertical axis as the direction of the fluid flow stream 50 changes. In this way, the cable 10 may be smoothly received by and dispatched from the end station 20 irrespective of the direction of receipt or dispatch. Receiving and dispatching feed pulleys 204, 206 are located directly above their respective guide pulleys 200, 202 and serve to redirect cable 10 between a horizontal conveyor plane within the end station 20 and a vertical plane through the respective pivoting axes of the guide pulleys 200, 202.

Further pulleys 208, 210 are provided in the horizontal conveyor plane to redirect cable 10 from the receiving portion of the end station 20 to the dispatching portion of the end station 20. In addition, a tensioning pulley 212 is provided between the horizontal pulleys 208, 210 to enable the cable 10 to be tightened or slackened accordingly.

Each pulley relies on friction between the cable 10 and a receiving surface of the respective pulley to maintain contact therebetween and enable one to be driven by the other. If the aforementioned stops are included in the installation, attached to cable 10, these stops may be used to interact with the receiving surface of the respective pulleys to improve the interaction (and prevent slippage) between the pulley and the cable 10.

The receiving surface of each of the guide pulleys 200, 202 preferably comprises a cross sectional profile which cooperates with the vane body 112 to orientate the vane 40 upon receipt or dispatch thereof. It is generally preferable for the vane 40 to assume a wing 100 downwards orientation upon entry to and exit from the end station 20.

Sealed cavities may be provided within the pylon 106 and/or within the wing 100 of the vane 40. This enhances the buoyancy of the vane 40, indeed the volume of these cavities may be chosen so that the weight of the cable 10 is, at least partially, overcome. Preferably, the buoyancy of the combination of the cable 10 and the vanes 40 mounted thereon approaches neutral buoyancy, so that the loading on the pulleys within the end station 20 is minimised. In particular, altering the tension of the cable to raise and lower the vanes to permit passage of vessels along the surface of the water can be achieved more readily if neutral buoyancy is achieved, so that a minimal level of loading is transferred to the structure and the pulleys of the end stations 20.

A means for driving a generator (not shown) must also be coupled to and driven by the cable 10 in order to extract energy from the installation. In this example pulley 210 is, in fact, a generating pulley which is directly connected to a generator for generating electricity. Generating pulley 210 is preferably provided in line with the dispatching feed pulley 206, at a point of significant loading within the installation, so that the maximum level of power can be extracted from the installation. Alternatively, a separate generating pulley could be included within the installation to extract energy therefrom.

When the current in the fluid flow stream is particularly strong or unpredictable, for example during a storm surge, it may be desirable to remove some or all of the vanes 40 from the cable 10 to avoid excessive loading on the structure of the end stations 20. Consequently, it may become necessary for the cable 10 to be driven round the installation as the vanes 40 are removed. In other words, the vanes 40 may not be contributing to the force required to displace the cable 10 to enable the remaining vanes 40 to be returned to an end station 20 for removal. In these circumstances the generating pulley 210 becomes a drive pulley and uses electricity to drive the cable 10 around the installation. De-powering of the vanes 40 may be required when the generator located at one of the end stations 20 fails or is otherwise taken out of commission (e.g. for maintenance). In these circumstances the pitch angle a of each wing 100 of the respective vanes 40 downstream of the idle generator can be increased by extension of hydraulic rod 110 so that each wing 100 contributes minimal loading to the installation.

In normal operation, each vane 40 may be disconnected from the cable 10 within the end station 20 to enable maintenance to be carried out on the vanes 40. Once disconnected from the cable 10 the vanes 40 can be maintained and the distribution of vanes 40 on the cable 10 can be altered. Figure 8 illustrates a disconnection point 214 downstream of the receiving guide pulley 200 but upstream of the receiving feed pulley 204. Vanes 40 are disconnected from cable 10 at disconnection point 214 by releasing the second sheath component 128 of the vane body 112 and the vanes 40 are then transferred onto a conveyor rail 220. Vanes 40 are shunted around the conveyor rail 220 from the receiving portion of the end station to the dispatching portion of the end station 20 during which time, the internal battery of the vane 40 if present can be recharged. In addition, the hydraulic rod 110 of the vane 40, and therefore the pitch angle a of the wing 100, can be manually or automatically reset and/or the internal controller of the vane 40 can be reprogrammed to accommodate temporal shifts in conditions of the fluid flow stream.

Furthermore, whilst the vane 40 resides in a queue within the end station 20 it can be readily accessed for any maintenance that must be carried out. In particular, an additional loop 222 of the conveyor rail 220 is provided whereby vanes 40 can be taken out of service. Rail spur 224 is provided for introducing new vanes 40 to the installation or removing vanes 40 therefrom. As discussed above, the tubular component 114 of vane body 112 may comprise a shock absorber at one or both ends thereof to enable the vanes 40 to butt up against one another without causing damage as they are shunted around the conveyor.

Figure 9 illustrates a re-connection point 216 downstream of dispatching feed pulley 206 and upstream of dispatching guide pulley 202. The vanes 40 are re-connected to cable 10 at the re-connection point 216, prior to launch into the fluid flow stream, in this example the body of water, via the dispatching guide pulley 202.

Preferably, the transition of the vanes 40 from the end station 20 into the water is smooth and stable. To enhance the stability of this transition, the guide pulleys 200, 202 are configured so that they receive vanes 40 from and dispatch vanes 40 to the water directly. In particular, when a vane 40 is dispatched into the water, the point at which the cable 10 leaves the pulley 202 should be submerged in the water so that the vane 40 is engulfed by water. This enhances stability of the vane 40 especially when the pulley 202 is sheltered from the prevailing current, for example using shields 226, so that the vane 40 is released into substantially still water.

As the vane 40 travels further from the pulley 202 the forces of the fluid flow stream gradually build up and act on the surfaces of the vane 40, in particular the pylon 106, to reorient the vane 40 and cause thewing 100 to take up a position roughly orthogonal to the fluid flow stream and downstream of the cable 10.

In operation, as the cable 10 passes into the dispatch guide pulley 202 a vane 40 is connected to the cable 10 at connection point 216. The vane 40 is conveyed around the dispatch guide pulley 202 and is submerged into substantially still water at the edge of the river 30. As the vane 40 passes out into the moving current of the river 30 the fluid forces act upon rigid pylon 106 and urge the pylon to align with the fluid flow stream. The vane 40 is thus reorientated so that the wing 100 becomes substantially vertical on the downstream side of the cable 10. Fluid forces acting on the wing 100 cause the vane 40 to be transported through the water towards the receiving side of the next end station 20. The cable 10, being connected to the vane 40, is drawn along with the vane 40 and is thus transported around the installation.

Vanes 40 are mounted on cable 10 at discrete intervals. Preferably these intervals are evenly spaced along the span of the cable 10. The magnitude of the interval can be altered in dependence on the conditions of the fluid flow stream at any particular instant, If the currents are particularly strong and the vanes 40 are highly loaded, a significant load is placed on the end stations 20. There are structural limits that the end stations 20 can withstand and so, in particularly strong currents, it may be necessary to increase the interval (increase the spacing) between vanes 40 so that fewer vanes 40 are present across the span of the cable 10 and hence the loading of the pulleys of the end stations 20 is reduced.

Variations in interval between the vanes 40, changes in pitch angle a of each wing 100 of respective vanes 40, recharging of internal batteries and reprogramming of any internal controllers located within the vanes 40 may be carried out manually or may be governed by an end station control system. The control system receives input signals relating to fluid conditions within the fluid flow stream and determines control instructions dependent thereon.

The cable 10 is received by the receiving guide pulley 200 of the next end station and conveyed around the receiving feed pulleys 204, 208 and the tension pulley 212 to the generating pulley 210. As the corner is turned around the generating pulley 210 the greatest level of tension is experienced by the cable 10 as it comes into line with the cumulative loading effect of the vanes 40 mounted on the next suspended section of cable 10. This cumulative force is transferred to the generating pulley 210 which, in turn, drives a generator.

In order to keep the receiving and dispatching of the vanes 40 submerged as discussed above, the guide pulleys 200, 202 must be sized to accommodate the typical fluctuations in water level. In river flows, that do not experience tidal variation, the guide pulleys 200, 202 may be reasonably small. However, in estuary, coastal or off shore waters the amplitude of the tide may be more significant, leading to increases in the diameter of guide pulleys 200, 202. In these circumstances, an alternative guide mechanism, such as that shown in Figure 10, could be provided to keep the mechanism compact and stable.

The guide means 300 illustrated in Figure 10 can accommodate any required amplitude of the tide without requiring a guide pulley of excessive diameter. Guide means 300 comprises a number of smaller pulleys 302 mounted to freely rotate within a housing component 304. The housing component 304 is mounted pivotally about a vertical axis directly beneath the feed pulley 306. The smaller diameter pulleys 302 thus enable the structure that supports the guide means 300 to be more compact and therefore more robust than when a single, large diameter pulley is cantilevered from the same pivoting axis as in the previous embodiment. The cable 10 is guided into the end station 20 along a receiving surface of respective smaller diameter pulleys 302. Preferably, the cross sectional profile of each receiving surface is shaped to accommodate the body 112 of the vane 40.

The installation described thus far, represents apparatus that may be extended across a river or other similar narrow body of water. The span of the river and therefore the installation may, for example be in the region of 50 to 150m and the vanes 40 included in this installation preferably have a wing span of 2 to 5m.

However, an equivalent installation may be located in an estuary, having an end station 20 located on each side of the river mouth. Alternatively the installation could be located in a coastal region, having one end station 20 located on dry land and a second end station 20 located on a tower built away from the shore. An offshore installation requires each end station 20 to be mounted on towers, preferably these towers stand on the sea bed. The distance between these towers, and therefore the span of the installation may be in the region of 1 to 2km and the vanes 40 included in this installation may have a wing span in the region of 15 to 25m.

The examples illustrated, consider a single span between two fixed points, however, a number of installations could be implemented using a number of free standing towers as shown in Figures 11 to 14. Each adjacent pair of towers supports an installation as previously described. Each tower may then act as a support mechanism for two or more end stations 20 as illustrated by the central tower in Figure 11 or the "apex" stations in the triangular configuration illustrated in Figure 12.

Figure 13 illustrates an alternative triangular configuration, whereby a single installation is supported using three end stations 20, each mounted on a respective free standing tower. In this example there are three spans of the continuous loop of cable 10, each having a number of vanes 40 suspended thereon.

Figure 14 shows a spoke configuration, wherein a main central hub station 400 may be provided together with a number of satellite stations 402, here four are illustrated.

All of the vane maintenance, reprogramming and recharging facilities may be provided on the main central hub station 400. Each of the satellite stations 402 may simply comprise a number of feed pulleys for guiding the cable 10 from an outward portion of the installation to an inward portion of the installation and a generating pulley for extracting energy from the outward portion of the installation.

The end stations 20, 400, 402 could alternatively be provided on a floating platform or vessel rather than a rigid structure mounted on the sea or river bed. Preferably, such a floating platform would be tethered or anchored to the sea or river bed.

The installation described above may also be used in an air flow stream, for example across a valley with an end station 20 mounted on opposing hill sides, up the side of a hill or mountain, or between two free standing towers in a windy location either on land or out to sea. A smaller version of the installation may even be located on the side of a building or between buildings so long as the site experiences bulk air flow which can interact with the surfaces of the wing 100 and thereby drive the cable 10.

The span of such an installation may be in the region of 5 to lOm, having vanes with a wing span in the region of 20 to 30cm.

Cable 10 IL preferably made from stainless steel, however for smaller scale installations, especially those located in an air flow stream, the cable 10 may be provided by a chain instead. The chain may be made from plastic to provide a lighter flexible support means.

The components of the vane 40, including the wing 100 and the pylon 106 are preferably made from carbon. In air flow streams, it may be preferable to form the vane components from a lighter material such as glass fibre or plastic.

Advantageously the present invention provides a method and an installation for generating energy and in particular electricity from fluid flow and particular water flow which is easy to install and maintain. Furthermore, the installation is environmentally friendly in that it has little, or no, effect on the sea, river, or estuary nor on the river bed or sea bed whilst maintaining almost unrestricted access to the body of water for vessels that pass along the surface thereof. Energy can be harnessed and electricity generated irrespective of the direction of the fluid flow stream, thus the choice of site for the installation is particularly flexible.

Claims

1. A vane for driving electricity generating means, the vane comprising: a vane body for receiving a support means which is coupled to electricity generating means; a wing, spaced from the vane body, for interacting with a fluid flow stream in which the vane is located and for generating thrust therefrom; and an orientation means connected between the vane body and the wing, for interacting with the fluid flow stream and thereby orientating the vane about the support means to optimise thrust generation by the wing.

2. A vane according to Claim 1, wherein the orientation means is a rigid pylon connected to the vane body and the wing and located therebetween for orientating the vane substantially orthogonally to the fluid flow stream.

3. A vane according to Claim 1 or Claim 2, wherein the wing is a variable profile wing.

4. A vane according to Claim 3, wherein the wing is pivotally connected at a leading edge thereof to the pylon to enable relative rotational movement there between.

5. A vane according to Claim 4, comprising an extendable member fixed between a trailing portion of the wing and the pylon to adjust the degree of rotational movement between the pylon and the wing.

6. A vane according to Claim 5, wherein the extendable member is a hydraulic rod.

7. A vane according to Claim 5 or Claim 6, comprising a controller for controlling the degree of rotational movement between the pylon and the wing.

8. A vane according to Claim 7, comprising an internal power supply for powering the controller.

9. A vane according to Claim 8, wherein the power supply is a rechargeable battery.

10. A vane according to any of Claims 7 to 9, comprising a sensor for detecting a parameter relating to the fluid flow stream.

11. A vane according to Claim 10, wherein the parameter is at least one of the group of flow rate and flow direction.

12. A vane according to Claim 10 or Claim 11, wherein the controller is configured to receive a signal, indicative of the detected parameter, from the sensor and to adjust the degree of rotational movement between the pylon and the wing dependent thereon.

13. A vane according to any preceding claim, wherein the pylon is pivotally connected to the vane body to enable relative rotational movement therebetween, the pylon comprising a clamping member which protrudes through an aperture in the vane body, the vane being configured such that the clamping member engages with a support means located within the vane body when the wing experiences a loading condition.

14. A vane according to any preceding claim, wherein the wing has an aerofoil cross section.

15. A vane according to any of Claims 1 to 13, wherein the wing has a parallel cross section.

16. A vane according to any preceding claim, wherein the wing is of dihedral form.

17. A vane according to any preceding claim, wherein the wing comprises a sealed cavity for increasing the buoyancy of the vane.

18. A vane according to any of Claims 2 to 17, wherein the pylon comprises a sealed cavity for increasing the buoyancy of the vane.

19. A vane according to any preceding claim, wherein the vane comprises a rudder for adjusting the vertical location of the vane.

20. An installation for generating electricity from a fluid flow stream, the installation comprising: a flexible support means, driveably connected to a generator; and a vane according to any preceding claim, mounted on the flexible support means and configured to interact with the fluid flow stream and be driven therethrough by fluid forces exerted on the vane, whereby the vane displaces the support means and thus causes the generator to generate electricity.

21. An installation according to Claim 20, wherein the flexible support means is made of metal.

22. An installation according to Claim 21, wherein the metal is stainless steel.

23. An installation according to Claim 20, wherein the flexible support means is made of a plastics material.

24. An installation according to of Claims 20 to 23, wherein the flexible support means is a cable.

25. An installation according to any of Claims 20 to 23, wherein the flexible support means is a chain.

26. An insta!lation according to any of Claims 20 to 25, wherein the vane is removably mounted on the flexible support means.

27. An installation according to any of Claims 20 to 26, wherein the installation comprises a plurality of vanes.

28. An installation according to Claim 27, wherein each vane is mounted on the support means substantially equidistant from one another.

29. An installation according to any of Claims 20 to 28, wherein the installation comprises two end stations, each end station comprising a pulley arrangement for suspending the flexible support means between respective end stations.

30. An installation according to Claim 29, wherein each pulley arrangement comprises: a guide means for guiding the flexible support means in to and out of the end station; and a feed pulley for redirecting the flexible support means from one side of the end station to the other.

31. An installation according to Claim 30, wherein the guide means is provided by a single guide pulley.

32. An installation according to Claim 30, wherein the guide means is provided by a plurality of guide pulleys located within a housing component.

33. An installation according to any of Claims 30 to 32, wherein at least one of the pulley arrangements comprises a tensioning pulley for raising or lowering the flexible support means by adjusting the tension therein.

34. An installation according to any of Claims 30 to 33, wherein each pulley arrangement comprises a generating pulley coupled to a generator for generating electricity from any displacement of the flexible support means.

35. An installation according to Claim 34, wherein the generating pulley is also a driving pulley for driving the flexible support means around the installation.

36. An installation according to any of Claims 20 to 35, wherein the installation comprises one or more stops attached to the flexible support means to restrict movement of the, or each, vane along the support means.

37. An installation according to Claim 36, wherein the, or each, stop comprises a shock absorber.

38. An installation according to any of Claims 20 to 37, wherein the fluid flow stream is a body of water.

39. An installation according to Claim 38, wherein the body of water is one of the group of a river, an estuary, a coastal region and an offshore region.

40. An installation according to any of Claims 20 to 37, wherein the fluid flow stream is an air stream.

41. A method of generating electricity from a fluid flow stream comprising the steps of: suspending a single cable within the fluid flow stream; mounting a vane on the cable such that the vane interacts with the fluid flow stream and is driven therethrough by fluid forces exerted thereon; and driveably connecting the cable to a generator, whereby the vane displaces the cable and thus causes the generator to generate electricity.

42. A method according to Claim 41, comprising the steps of: sensing fluid flow parameters to determine the current fluid flow conditions; calculating the cumulative loading on the installation; determining the number of vanes that can be supported by the installation; and mounting this number of vanes on the cable to generate a maximum quantity of energy for the current fluid flow conditions.

43. A method according to Claim 41 or Claim 42, comprising the steps of: sensing fluid flow parameters local to the vane to determine the local current fluid flow conditions; calculating an optimum pitch angle for a wing of the vane; and adjusting the pitch angle of the wing accordingly.