WATER POWERED ENERGY GENERATOR

The present invention relates to the provision of a wave powered device for extracting energy from waves, particularly but not exclusively in relatively shallow water to generate electricity from waves approaching a shore. The device may also be used to extract energy from tidal or river flow.

A very large number of wave powered devices have been proposed to provide electricity from waves. Similarly a large number of devices have been proposed to provide electricity from tidal flow or river flow (water currents) . These water powered devices are the subject of much ongoing research. However, few such devices have been successful to date, for a number of reasons including cost, robustness and efficiency of energy conversion.

It is an object of the invention to provide a water powered energy generator that avoids or minimises at least one of the aforementioned disadvantages of known devices. It is a further object of the present invention to provide a wave powered energy generator that avoids or minimises at least one of the aforementioned disadvantages of known devices .

According to a first aspect the present invention provides a water powered energy generator comprising a water energy capture device and power extraction means for extracting energy from the motion of the capture device; said capture device comprising a flexible, endless, flap carrier running along a path about horizontally spaced apart rotating support members mounted on a base; said rotating support members having substantially horizontally disposed rotation axes, in use; wherein said flap carrier carries an array of buoyant flaps, each flap being transverse to the path of the flap carrier, attached by a pivot at a pivot end to the flap carrier and moveable from a first, water motion engaging position, where the flap projects away from the path of the flap carrier, to a second position where the body of the flap is closer to the flap carrier and said flap projects from the pivot end in the direction opposite the direction of travel of the flap carrier; whereby in use when the water powered energy generator is mounted in water with the path of the flap carrier substantially coincident with the direction of water motion, the action of the water motion on the flaps, when in their first, water motion engaging position, drives the flap carrier along its path.

The water energy capture device operates in accordance with water motion. The water motion may be the flow of a river

or of a tide. The generator is placed in a selected location, at a selected depth to interact effectively with the water flow.

Alternatively, the water motion may be wave motion. Thus according to a second aspect the present invention provides a wave powered energy generator comprising a wave energy capture device and power extraction means for extracting energy from the motion of the capture device; said capture device comprising a flexible, endless, flap carrier running along a path about horizontally spaced apart rotating support members mounted on a base; said rotating support members having substantially horizontally disposed rotation axes, in use; wherein said flap carrier carries an array of buoyant flaps, each flap being transverse to the path of the flap carrier, attached by a pivot at a pivot end to the flap carrier and moveable from a first, wave engaging position, where the flap projects away from the path of the flap carrier, to a second position where the body of the flap is closer to the flap carrier and said flap projects from the pivot end in the direction opposite the direction of travel of the flap carrier; whereby in use when the wave powered energy generator is mounted near the surface in shallow water with the path of the flap carrier substantially coincident with the direction of waves running towards the shore, the

action of the waves or wind on the flaps, when in their first, wave engaging position, drives the flap carrier along its path.

The flap carrier may be any endless flexible member that has the required strength and flexibility to carry the array of flaps along the path. It may be for example a belt, toothed belt or chain. Preferably the flap carrier does not have a continuous surface but has spaces or holes provided in it to reduce resistance to the motion of the water, for example wavesand their interaction with the flaps. For example, if the flap carrier takes the form of a belt, as in a conveyor belt, it is preferred that the belt is provided with holes or is of an open mesh material. More preferably the flap carrier comprises two parallel spaced apart endless wires interconnected by an array of transverse wires. This arrangement of transverse 'conveyor wires,' which can carry the flaps, ensures minimal interaction between the waves and the flap carrier avoiding power losses. Alternatively the flap carrier comprises two parallel spaced apart belts interconnected by the array of transverse wires .

The flap carrier runs on a path about horizontally spaced apart rotating support members . The rotating support members may be, for example, wheels, cogged wheels, or

rollers, which are formed to be driven by the motion of the flap carrier. For example, if the flap carrier is a conveyor wire arrangement as described above the rotating support members may be cogged wheels whose cogs engage with the transverse wires and are driven by their motion. Rotating support members are only required at each end (horizontal extremity) of the flap carrier path. However further support members can be provided at one or more intermediate points along the path if desired, for example, to strengthen the device.

The flaps may be of any shape and may be curved or substantially flat. Advantageously the flaps are substantially square or rectangular in form. The flaps may be made of any material of sufficient strength and stiffness to drive the flap carrier when being pushed by water motion such as waves tidal flow or river flow. For example the flaps may comprise metal sheeting. The flaps are buoyant, buoyancy may be provided by making the flaps of a buoyant material, for example wood. Alternatively the flaps may comprise a combination of buoyant and non-buoyant materials to provide the desired combination of buoyancy and strength. For example the flaps may comprise an outer metal sheet with an inner buoyant core of wood or plastic or a foamed plastic. Alternatively the flaps may have one or more chambers within the body of the flap. The chambers

are sealed and filled with a gas, for example, air to provide the required buoyancy.

The buoyant flaps act automatically in the operation of the device, they pivot about their pivot ends between their fist and second positions and back again as the flap carrier runs along its path as described below, with respect to a generator powered by wave motion. The energy capture device operates in a similar fashion when powered by a river or tidal flow, with the flaps in their first position being pushed by the flowing water. Therefore it will be understood that expressions such as "wave energy capture device" used in the following description can be interchanged with expressions such as "water energy capture device", as appropriate, when the generator is powered by river or tidal flow.

The flap carrier moves along a path about horizontally spaced apart rotating support members, such as cogged wheels, which rotate about horizontal axes. Therefore the path followed by the flap carrier has an upper side where the flap carrier is above the rotating support members and nearest the water surface. After turning round horizontal support members at one end (horizontal extremity) of the path the flap carrier then runs along the lower side of its path, below the rotating support members, before turning round the horizontal support members at the other end of

the path, back onto the upper side again. When the flap carrier is on the upper side of its path i.e. when nearest the surface of the water, the flaps on the flap carrier will tend to move about their pivot ends, on account of their buoyancy, upwards to the first position where the flap projects more from the path of the flap carrier. Having moved to their first position, the face of each flap facing the incoming waves is pushed by those waves thus moving the flap carrier, on the upper side of its path, in a direction towards the shore. Where the flaps project above the surface of the waves the wind may also act on the flaps to move the flap carrier along.

The flaps may be prevented, when pushed by the waves from rotating past their first position, about their pivots, by a stop or limiter on the pivot mechanism. Alternatively, the connection between the flaps and the flap carrier may be formed and arranged to allow the flap to be deflected, past its normal first (operating) position when subjected to excessive pressure. For example during extreme weather conditions. For example, the connection between the flaps may be fitted with a resilient biasing means, such as a spring, which acts to prevent the flap moving past its first position except when the flap is subjected to excessive pressure. Alternatively the flap may be provided with a connection that allows it to pivot, when under

excessive pressure, so as to no longer be fully transverse to the direction of travel of the flap carrier as described hereafter with respect to a particular embodiment. Arrangements that allow deflection (movement) of the flaps past the first position or away from the transverse position, so as to reduce the pressure of the water on the flaps, reduce the risk of damage to the flaps or other components of the generator.

Preferably when in the first position the flaps are at right angles to the flap carrier. This provides good interaction with the waves and wind as the flaps present the largest surface area to the waves . When the flap carrier reaches the end of its path nearest the shore, the carrier then turns round a rotating support member onto its (lower) return path, back out from the shore towards the sea, where the buoyancy of the flaps now acts to move them to the second position.

When the flap carrier is on the lower side of its path, i.e. returning back out from the shore, the flaps will tend to move about their pivots on account of their buoyancy so that the body of each flap moves up towards the flap carrier. In other words the flaps, when the flap carrier is on the lower side of its path, tend to move to the second position. In this position they present less resistance in

the water to the movement of the flap carrier as they are projecting from their pivot ends in the direction opposite the direction of travel. Preferably in the second position the bodies of the flaps are adjacent to or touch the flap carrier. In this position they cause the least resistance to the movement of the flap carrier along its path through the water, as the flaps are end on to the direction of travel .

In addition to providing automatic pivoting, the buoyancy of the flaps provides an upwards acting force on the flap carrier, tending to keep it appropriately tensioned on the rotating support members .

Preferably, especially in order to adjust to tidal movement the capture device is moveable up or down on its base to an optimal depth in the water. This up or down movement can also be used to adjust the position of the capture device depending on wave height, to optimise power generation. An adjustable height capture device is also useful when the device is powered by river or tidal water flow. The height of the device can be adjusted to account for the tide, and/or when in a river for the volume of water flowing down the river. Thus the device can be positioned to most effectively extract energy from the water movement. For example the device may be positioned on a base comprising

telescopic legs anchored to the seabed. Sensors may be provided to detect tidal and wave conditions and provide data to a control system which operates the telescopic legs automatically. Feedback to the control system from the electricity generating means can be used to optimise power output .

Where the energy generator is located particularly close to shore some additional power may be generated by waves running back from the beach acting to push the flaps at the start of their journey along the return path as described hereafter with reference to a specific embodiment.

Wind moving onshore with the waves can also act to generate more power. Any portion of a flap that projects out of the water will be pushed by wind acting on its face.

The power extraction means extracts energy from the motion of the wave energy capture device. Preferably the energy is extracted from the rotational motion of at least one of the rotating support members . Advantageously the wave energy generator has a plurality of spaced apart rotating support members, and energy is extracted from each. The simple rotational motion of the rotating support members is conveniently converted into power. For example, the rotation of a rotating member such as a cogged wheel may be

used to drive a pump to produce hydraulic power.

Preferably the rotation is used to drive an electricity- generating device, such as an alternator or dynamo. The electricity generated can then be connected by suitable cabling to facilities on shore.

Advantageously the wave powered energy generator is portable. For example, it may be constructed of readily assembled and disassembled component parts. This allows the energy generator to be easily placed at a suitable location to generate power from the waves whenever a power supply is required, even for a temporary use.

Advantageously and according to a third aspect the present invention provides an energy generating system comprising a plurality of wave energy generator devices according to the invention. A number of devices placed along a shoreline at suitable intervals can have their electrical output combined to produce a substantial power output, extracting energy along a stretch of coastline. The energy generating system may also be operated by means of river flow or tidal flow, with water energy generating devices located along the length of a river or in a tidal flow.

According to a fourth aspect the present invention provides a method of extracting energy from waves water motion comprising the steps of: - a) providing a water powered energy generator device according to the invention; b) locating the water energy capture device in a body of water with the path of the flap carrier substantially coincident with the direction of travel of water motion in the said body of water; c) extracting energy from the water motion in the said body of water and converting it to electricity. The water motion employed in the method may of any form, for example waves, river flow or tidal flow. The generators of the invention are located with the path of the flap carrier substantially coincident with the direction of travel of the water motion. However this may not always be the case since waves and tides will change direction and river currents can vary depending on the volume of flow. It may also be advantageous to site the flap carrier at a skewed angle to the oncoming water motion (say by 10° to 20°) to aid water flow through the device. This arrangement provides a component of water flow across the surface of each flap and can improve performance.

Further preferred features and advantages of the present invention will appear from the following detailed description of an embodiment illustrated with reference to the accompanying drawings in which: Fig. 1 shows in schematic elevation a wave powered energy generator device of the invention;

Figs.2 (a to d) show the operation of a flap in use of a wave powered energy generator device of the invention; Fig.3 shows in plan view the wave powered energy generator of figure 1.

Figs.4 (a, b) show in schematic elevation and plan a water powered energy generator of the invention; and Figs .5 (a,b,c) show the operation of a deflecting flap arrangement .

Figure 1 shows in elevation a wave powered energy generator 1 of the invention located in shallow water 2 near a shore 4. The generator 1 has a wave energy capture device 6 mounted on a base of four telescopic legs 8 anchored 10 to the seabed 12 in a body of water.

The wave energy capture device 6 has cogged wheels 14 as rotating support members 15, about which a flap carrier 16 consisting of spaced apart wires (see Fig. 3) runs with the direction of travel indicated by the arrows T. The flap carrier has an array of buoyant flaps 18 each attached by a

pivot 20 running across the flap carrier 16. Electrical generators 22 are enclosed within the cogged wheels 14 nearer the shore 4 and connect by a cable 24 to a grid distribution network (not shown) .

The capture device 6 is mounted so that the upper side 26 of the path of the flap carrier 16 is near the water surface so as to allow interaction of the flaps 18 with the wave crests 28 travelling towards the shore 4 in the direction shown by the arrow W.

The interaction of flaps 18 with water will now be illustrated with reference to Figures 2a to 2d.

Figure 2a shows a flap 18 on the upper side 26 of the path of a flap carrier 16. The flap 18 lies on the carrier 16 (i.e. the flap is in its second position) as there is no water to move it. Figure 26 shows a flap 18 moved from its second position by the arrival of a wave crest 28. The flap 18 has moved about its pivot 20 because of its buoyancy. In Figure 2c the flap 18 has been moved fully to its first position, which in this example is vertically upright, by the wave crest 28. A stop or limiter (not shown) on the pivot 20 prevents the flap 18 moving past the desired vertical position. In this position the wave crest 28 can no longer pivot the flap and so the force of the

wave acting on the flap 18 will tend to move the flap carrier 16 along its path as shown by the arrow T. As an alternative to a stop or limiter the pivot 20 may be fitted with a biasing means such as a spring (not shown) arranged to prevent the flap 18 pivoting past the first position shown in figure 2c, when subjected to normal wave pressures. When the flap 18 is subject to excessive wave pressure the flap 18 pivots further than the position shown in Figure 2c thereby presenting a smaller surface area to the waves so as to avoid damage to the apparatus in extreme weather conditions .

Figure 2d shows the flap carrier 16 on its underneath return path. The flap lies against the structure 30 of the flap carrier 16 i.e. the flap is in its second position, by virtue of its buoyancy shown by the arrow B. In this position the flap is ^λ end on' to the direction of travel T, with its pivot edge leading. The flap 18 therefore provides minimum resistance (drag) to the movement of the flap carrier 16.

Referring back to Figure 1 the flaps 18 operate automatically as discussed above as the wave crests 28 travel towards the shore 4 resulting in the flap carrier 16 being driven round the cogged wheels 14. The turning cogged wheels operate the electrical generators 22

producing electricity that is fed by the cable 24 to a distribution network. Extra energy can be derived from wind moving in the same direction as the wave crests and acting on the top portion of raised flaps 18. Similarly water returning from the shore 4 back towards open water, indicated by arrows R on Figure 1 can also act to drive the flaps 18 at least at the start of their return path out towards the cogged wheels 14 furthest from the shore.

Figure 3 shows in plan view the device 1 of Figure 1. The spaced apart transverse wires 32 are connected at each end to spaced apart parallel endless wires 34 and engage the cogged wheels 14 (cogging not shown for clarity) which are connected in pairs by axles 36. The flaps 18 (also not shown for clarity in this view) are attached to transverse wires 32 about which they pivot as discussed above.

Figure 4a shows in elevation an energy generator of the invention of the same form as the generator of Figure 1 located in a river 38 to extract energy from the flow of river water indicated by the arrow F 40. The generator 1 has the same form as that of figure 1 and operates in similar fashion. The buoyancy of the flaps 18 moves them to the first position when on the upper side 26 of the flap carrier 16, where they are driven by the flow F 40. When on the underside of the flap carrier 16 the buoyancy of the

flaps 18 causes them to rest against the flap carrier 16, minimising their interaction with the flow F 40. In this illustration as shown in the plan view of figure 4b the flow F 40 is shown skewed or offset from the direction of travel of the flap carrier 16. Each flap 18 is then struck directly by a portion of the flow as indicated by the arrows f 46 providing a component of water flow across the surface of each flap 18.

Figure 5a shows schematically a flap 18, in its first position, which has a joint 42 formed in its connection to the flap carrier 16. In use the flap 18 pivots up and down as a consequence of its buoyancy in the same fashion as the flaps shown in the previous figures. The joint 42 includes a spring loaded mechanism 44 which, when the flap 18 is subjected to excessive force caused by extreme weather or high water flow allows the flap to deflect sideways i.e. move in the horizontal plane, as shown in Figure 5b, so that the flap is no longer at right angles (fully transverse) to the flow F 40. This mechanism reduces the pressure on the flap 18 reducing the risk of damage to the flap 18 or other parts of a generator. Pairs 44 of flaps 18 may be mounted to either side of a flap carrier 16 as indicated in the schematic plan view of Figure 5c, which illustrates the deflection of the flaps when the flow F 40 is excessive.