GB2475405A

GB2475405A - Wave energy generator for harvesting kinetic energy of waves and tidal flow

Info

Publication number: GB2475405A
Application number: GB1019037A
Authority: GB
Inventors: David Bowerman
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-11-11
Filing date: 2010-11-11
Publication date: 2011-05-18
Anticipated expiration: 2030-11-11
Also published as: GB0919701D0; GB201019037D0; GB2475405B

Abstract

A wave powered generator comprises a buoyant housing (12, fig.2) having an entrance for receiving water from a portion of a wave and an outlet permitting the water to exhaust from the housing. In use the generator is tethered so that the entrance faces oncoming wave fronts. A float 20a, 20b is supported on the generator by a rigid arm 22 connected to the housing at a pivot 24, whereby an incident wave displaces the float, with respect to the structure. Energy is extracted from the wave by way of a flap 50 located between the entrance and outlet. A dog-leg connection is provided on the arm 22 and arranged to disengage in high seas and very strong winds, so as to avoid damage to the generator.

Description

WAVE ENERGY POWERED GENERATOR

Field of the Invention

The present invention relates to a wave powered generator for harvesting kinetic energy of waves and tidal flow, in particular the generator is arranged to convert the movement of waves into electrical energy by means of transforming kinetic energy from waves into electrical motive force (EMF) by way of a pressurised hydraulic drive for powering a dynamo.

Background to the Invention

There is an increasing need and demand for renewable energy, as the world moves away from carbon based and carbon-dioxide producing energy sources. Renewable energy sources include such things as wind, hydro, solar and tidal. Another source is the energy source that waves provide.

There are problems associated with generation of electricity from waves amongst them the high total cost of providing reliable and robust generating equipment as well as power converters, power takeoff systems and mooring systems.

Prior Art

Despite the considerable amounts of kinetic and potential energy available from ocean wave energy, wave power generation is not currently a widely employed commercial technology although there have been attempts to harness this for many years.

Existing wave energy conversion systems include use of piezoelectric materials and hydrodynamic embedded shoreline devices with energy converters utilising pressure differentials. Many have failed to be commercially viable due to high set up costs and maintenance requirements, as well as excessive wear due to the extreme forces that can be encountered in high seas and storms.

International Patent Application Number WO-A3-2008/122867 (Navtek) discloses a wave energy system, typically mounted on a barge, for deriving energy from waves.

Energy is derived form marine wave motion as a wave breaks over one or more hulls. Pistons in cylinders are actuated by the mass of the wave so as to drive an hydraulic motor.

US Patent Number US 5 405 250 (Vowles et al) discloses an apparatus for converting the motion of waves into useful energy. The apparatus includes a wave energy follower which has a buoyant upper body portion and which is fixed at one end and pivots in response to incident waves. Funnelling panels act to direct waves towards the wave follower to amplify them.

International Patent Application Number WO-A1-2009/064237 (Frame Energy AB) discloses a system with buoyant members arranged so as rise and fall relative to one another under the influence of impinging waves.

Another example of an arrangement for extracting energy from a waves is described in US Patent US 4 454 429 (Buonome) in which is depicted an arrangement with floats which reciprocate in response to incident waves and are connected to a cylinder that in turn transmits hydraulic pressure to a turbine in order to generate electricity.

As the environments such systems are designed to operate in are harsh, prior systems have often been complicated and expensive to manufacture and maintain.

The present system overcomes these problems by providing a simple, efficient modular system with failsafe mechanisms and minimal maintenance requirements, a centralised electrical generation stage and fit-and-forget mechanics.

What is notable is that, in very high wind conditions with resultant high sea swell, existing systems were prone to storm damage.

An object of the invention is therefore to provide a wave energy generator that is able to withstand unusually high forces that can be encountered in very strong winds and extreme sea conditions.

Summary of the Invention

According to a first aspect of the invention there is provided a wave powered generator comprising: a buoyant housing having an entrance for receiving water from a wave and an outlet permitting the water to exhaust from the housing, said housing, in use, is tethered so that the entrance faces oncoming wave fronts and a float is supported on the generator by a rigid arm connected to the housing at a pivot, whereby an incident wave displaces the float, with respect to the structure, so as to establish a turning moment about the pivot; and an energy extractor is connected to the arm for extracting energy from the wave, characterised in that a dog-leg connection, located on the arm intermediate the float and the pivot, is arranged to disengage in high seas, so as to reduce the effective length of the pivot.

The wave travels from entrance to exit through a channel. The float and rigid arm are mounted in the channel. In combination the float and rigid arm form a paddle.

The paddle is subject to the force of the wave as it moves through the channel.

An advantage of this is that when waves become so large as to potentially damage the wave powered generator the pivot disengages from its operational state and adopts a passive or neutral state in which less surface area is presented to a wave and effectively acts as a hedgehog', curling itself into a safe, passive condition.

The wave powered generator does this automatically, without the need for expensive sensing equipment or complex control and actuating devices, simply by way of its self regulating structure.

The flap may be arranged so that is at least partially submerged, whereby in use, a portion of it is arranged to extract energy from the incident wave from below the water surface.

Ideally the wave powered generator extracts energy by way of a piston-in-cylinder arrangement that pressurises a fluid which is subsequently transmitted to do work.

The hydraulic cylinder(s) include a cylinder barrel, in which a piston connected to a piston rod moves back and forth. The barrel is closed at each end by the cylinder bottom (the cap end) and by the cylinder head where the piston rod comes out of the cylinder. The piston has sliding rings and seals. The piston divides the inside of the cylinder in two chambers, the bottom chamber (cap end) and the piston rod side chamber (rod end).

The cap end is ideally attached to the channel and the rod end to the paddle arm.

The movement of the waves is transmitted through the movement of the paddle into movement of the piston rod into forced movement of the fluid or air used as the hydraulic medium.

Under action and in use the hydraulic fluid or air utilised in the generator is able to exit from the channel through a hollow centred pipe, hose or tube. The hose is capable of withstanding great pressure and may combine with a non-return valve and accumulator.

Preferably the pressurised fluid turns a dynamo and generates electricity which is transmitted to one or more sub-sea sub-stations from where it is transmitted via high voltage sub-sea cables to a land based sub-station and either onto the national grid or a locally where it may be used.

According to a second aspect of the invention there is provided a wave powered generator comprising: a buoyant housing having an entrance for receiving water from a wave and an outlet permitting the water to exhaust from the housing, said housing, in use, is tethered so that the entrance faces oncoming wave fronts and a float is supported on the generator by a rigid arm connected to the housing at a pivot, whereby an incident wave displaces the float, with respect to the structure, so as to establish a turning moment about the pivot; and an energy extractor is connected to the arm for extracting energy from the wave, characterised in that a flap located between the entrance and outlet which, during a first interval presents relatively high impedance to the wave and during a subsequent interval presents relatively low impedance to the wave so as to optimise energy extraction.

In one embodiment the flap is at least partially submerged so that a portion of it is arranged to extract energy from the incident wave from below the water surface.

A hydraulic cylinder in a preferred embodiment is attached to the channel and to the rigid arm of the paddle arm. In this way as the paddle moves relative to the channel the piston is forced into the cylinder this being the power stroke forcing high pressure water via a non return valve and accumulator to the high pressure water outlet and onwards to an electricity generator which envisaged onshore. On the return of the paddle to the lower position -which may be promoted by the use of springs, but the weight of the paddle should be sufficient -the piston drawn from the cylinder, thereby forcing low pressure air into another accumulator. This air is released at intervals via a pipe mounted around the base of a ring of large tanks to lift them slightly to allow the top section to re adjust to the flow of the waves. It may be that the preferred orientation of the hydraulic cylinder is reversed and double-acting with both strokes forcing high pressure fluid out to be used for work. In this instance a separate air line would be used to trim the machine In the preferred embodiment the flap comprises two portions, hinged centrally to form an upside down V', wherein the paddle when under directed water flow pressure predicates the angle of the V to become enlarged up to 180 degrees, opening and becoming largely flat relative to the water surface, under the correct application of pressure. The void between the faces is occupied by air and this evacuates as the flap opens.

Such an arrangement allows flow to be channelled forwards acting in one direction wherein the flap is forced into a flat position relative to the water surface, therewith extending the hydraulic piston, and pressurising the fluid contained in the connected pipe. The eddies and overflow also act to push down the flap into a largely flat position relative to the water surface, by pushing against the flap, which by the angled face of its upside down V formation accepts lateral pressure and converts it to vertical pressure.

Ideally the flap is hinged and formed of two faces and is situated inside the channel.

Therefore all flow of a wave through the channel is directed over one or both of the faces to act in a downwards pressure. This necessitates that the flap occupies the majority of the width of the channel. In the preferred embodiment the flap is 5 m wide.

Means is ideally provided to enable the flap to be opened with minimal resistance.

This may involve one-way perforations in the flap faces, in the hinge, elsewhere on the paddle, to allow air or water to escape quickly and with minimal resistance from beneath the flap as it is forced down by the movement of the paddle.

In an alternative embodiment the sides of the channel may be striated or cellular in format to provide sideways exits of water or air from beneath the flap faces as they are opened.

Paddle has a break point in the preferred embodiment, which enables the paddle to alter the amount of surface area that is presented to waves. In the event that waves are excessively large, and so likely to damage the paddle and/or generator, a folding occurs as is explained in greater detail below.

This break point or fold point is provided by a hinge situate on the arms connecting the rigid arm with the float (or counterweight) and apron to the end with the flap. The hinge is held in a position by the provision of a spring. The spring combines with flexible hooks seated in catch holes near the float, at the same end of the paddle.

These hooks unseat or release from the catch holes allowing a release of the float end of the paddle from the connection to hydraulic cylinder(s) or piston(s) if the force of the water acting on the paddle reaches a predetermined excessive level. Ancillary locking devices may be provided or other configurations such as a leaf spring, sprung hook or flexible arm.

The hooks slip from their seating on the float end and the paddle folds, with the float end of the paddle being released free to pivot away from the pressure of the water flow.

The float end of the paddle in the preferred embodiment folds onto the roof of the channel of the device. In this manner the wave flow continues through the paddle. It passes between a space between the arms that connect an apron to the flap, and exerting no pressure on the hydraulic piston(s).

In the preferred embodiment the paddle is formed with arms connecting the float and apron and the flap with a gap between the arms, and between the flap and the apron -with the float and angled surface facing the flap. This latter float is formed with small drain holes on the top edge and in two sections, with a hermetically sealed horizontal part (when viewed in the lowered position) and a largely open bottom edge. This allows a small amount of water to enter the float, but not enough to impede the movement of the float upwards, and hence of the flap downwards, corresponding to extension of the cylinder, and corresponding pressurisation of the cylinder fluid.

In a storm situation, when the float end folds onto the roof of the channel, the largely open bottom edge has now turned upside down, so it is at the top of the float allowing it to become immediately and repeatedly inundated with seawater.

When the storm has passed the drain holes allow water to drain from the float which has acted as a reservoir when the paddle is in a folded position after excessive flow power has unseated the hooks and released the float end.

There is at least one spring provided to tend the float to a return and reformation of the paddle, said return spring(s) being calibrated to return the paddle to a generating configuration when the gravity acting on the float provides a lesser counter force.

In this manner as water drains from the float, the return springs act on the float end of the paddle and return it to the paddle's active situation where the flow of water may be used to extend the piston(s). In conditions of excessive water flow, the float will continue to be filled by the flow over the top of the channel. The float in turn when the paddle is in an active situation performs as a spoiler to the flow.

The generator also includes a ballast. This ballast is adjustable to enable trimming of the height and angle of attack of the generating section in relation to wave direction, tidal direction, water surface level and preferably is capable of self-trimming.

In the preferred embodiment this ballast is typically formed of a conical shape extending towards the sea-bed although cylinders may be equally appropriate. The tip of the cone may be formed of a concrete or other heavyweight compound, whilst the majority of the cone contains varying levels of water and air, which combination may be trimmed or adjusted to ensure the generator sits at the wave trough level or optimum level in the water for wave harvesting (delivery of pressurised water).

There may also be one or more horizontal or close to horizontal plates or skirts fixed around the ballast to help prevent unwarranted movement or bobbing.

The weight of the ballast prevents unwarranted movement and/or bobbing with the inertia it provides meaning energy is harvested under flow movement rather than utilised to move the ballast / generator.

A number of large tanks may be welded between the ballast and the generating section(s) in a ring. These may be filled with air or water and also trimmed to provide the maximum efficiency presentation to the waves.

Ideally therefore the optimum presentation of the generating devices to the water flow is a combination of the number and situation of the generating sections, the rotatable nature of the generating section(s) in respect to the fixed nature of the ballast, and the trimmed depth of the ballast, and the trimmed presentation of the generating section(s).

The combination of these factors is adjustable by simple mechanical means.

Ideally a plurality of the generators are connected together with pipes, cables or hawsers. Ideally this is in a hexagonal arrangement allowing the generators to attack the water flow over a larger area in combination, being anchored with enough slack to allow for tidal range, potentially being combined with buoys and anchor points in the hexagon. This arrangement or another, perhaps a square or rectangular shaped array, may be used to harvest the maximum potential energy over an area. Generators ideally are connectable in a plurality of combinations, and detachable individually for maintenance work.

Ideally the pipes and hoses that connect the generators in addition connect the generators to a remote, preferably onshore electricity generation facility. The pipes and hoses may be used to carry pressurised air, or fluid. In this facility the pressurised fluid or air is used to power turbines or otherwise produce an electrical current.

Preferred embodiments of the invention will now be described, by way of example only, and with reference to the Figures in which:

Brief Description of the Figures

Figure 1 shows an overhead outline view of an array of generators in use; Figure 2 shows a plan view of an embodiment of a single generator; Figure 3 shows a side elevation view of the generator of Figure 2; Figures 4 and 4a show overall view of alternative embodiments of the wave energy generator and shows a float connected to a body of the wave energy generator; Figures 5a, 5b and 5c illustrate diagrammatically, in conditions of large waves, how disengagement of the dog-leg connection acts to switch the float from its operational state to adopt a passive state; Figures 6a and 6b show diagrammatical views of a trimming system to modify buoyancy conditions of the wave energy generator; Figures 7a and 7b show plan views illustrating diagrammatical overviews of alternative arrangements of arrays of wave energy generators; and Figure 8a and 8b show alternative arrangements for sinking buoyant flaps.

Detailed Description of the Embodiments

Figure 1 shows an overhead outline view arrangement of wave energy converters arranged in an efficient energy capturing grid. The converters are interconnected to make sound structure as the triangle is a simple form that is inherently stable.

Figures 7a shows a similar triangular arrangement of converters the difference being that the triangle vertices are solely connection points. Figure 7b shows the converters in linear array to optimally convert the energy of waves oncoming from a single direction.

Ideally therefore the optimum presentation of the generating devices to the water flow is a combination of the number and situation of the generating sections, the rotatable nature of the generating section(s) in respect to the fixed nature of the ballast 58, and the trimmed depth of the ballast, and the trimmed presentation of the generating section(s).

The combination of these factors is adjustable by simple mechanical means. See for example the trimming valve 68.

Ideally a plurality of the generators 10 are connected together with pipes, cables or hawsers 11. Ideally this is in a hexagonal arrangement allowing the generators 10 to attack the water flow over a larger area in combination, being anchored with enough slack to allow for tidal range, potentially being combined with buoys and anchor points in the hexagon. This arrangement or another may be used to harvest the maximum potential energy over an area. Generators 10 ideally are connectable in a plurality of combinations, and detachable individually for maintenance work.

In another embodiment the wave energy converter 10 may alternatively be supported by a large main tank 54. A boss 56 is the connection means between the support and the wave energy converter 10. The converter is free to swivel on the boss 56 and is mounted so that it swings into the direction that gathers the most wave energy.

Ideally the pipes and hoses 40 that connect the generators 10 in addition connect the generators 10 to a remote, preferably onshore electricity generation facility. The pipes and hoses 40 may be used to carry the pressurised air, or fluid. In this facility the pressurised fluid or air is used to power turbines or otherwise produce an electrical current.

Figure 2 shows a top plan view of the wave energy converter while Figure 3 shows a side elevation view, Illustrated are a wave powered generator 10 comprising: a buoyant housing 12 having an entrance region 14 for receiving a wave and an outlet region 16 permitting water to exhaust from the housing 10. The housing 12 in use, is connected by way of tethers 18 so that the entrance 14 faces oncoming wave fronts.

A float 20 is supported on the generator 10 by a rigid arm 22 connected to the housing 12 at a pivot 24, whereby an incident wave displaces the float 20, with respect to the housing 12, so as to establish a turning moment about the pivot 24; and an energy extractor 26 is connected to the arm 22 for extracting energy from the wave.

An example of an energy extractor 26 is one or more hydraulic cylinder(s) having cylinder barrels 28, in which a piston 30, connected to a piston rod moves back and forth. Cylinder barrels 28 are closed at each and are ideally sealed and designed to withstand the effects of seawater. The piston ideally has sliding rings 34 and seals 36. The piston 30 divides the inside of the cylinder 28 in two chambers, the bottom chamber 28a (cap end) and the piston rod side chamber 28b (rod end).

The cap end 28a is ideally attached to channel portion 38 and the rod end 28b is connected to the rigid arm 22. Under wave action, and in use, hydraulic fluid or water, utilised in the cylinder 28, exhausts from the channel portion 38, through a hollow centred high pressure pipe or hose 40 to a generator. The hose 40 is capable of withstanding high pressures and may be utilised in combination with a non-return valve 42 and accumulator 44. Therefore the movement of the waves is transmitted through the movement of the float 20, also referred to as a paddle 23, into movement of the piston 30 into forced movement of the fluid.

The hydraulic cylinder 28 in a preferred embodiment is attached to the channel 38 and to the paddle arm 22. In this way as the paddle 23 moves relative to the channel 38 the piston 30 is drawn from the cylinder this being the power stroke forcing high pressure water via a non return valve 42 and accumulator 44 to the high pressure water outlet and onwards to an electricity generator which is envisaged either central to the array or onshore.

On the return of the paddle 23 to the lower position, which may be promoted by the use of springs 48, but the weight of the paddle 23 should be sufficient the piston retracts into the cylinder, thereby forcing low pressure air into another accumulator 44. This air is released at intervals via a pipe 40 mounted around the base of the ring of large tanks 52 to lift them slightly to allow the top section to re adjust to the flow of the waves. It may be that the preferred orientation of the hydraulic cylinder is reversed. A large main tank 54 may support the entire wave energy converter.

In the preferred embodiment the flap 50 comprises two portions, hinged centrally to form an upside down V', wherein the paddle 23 when under directed water flow pressure predicates the angle of the V to become enlarged up to 180 degrees, opening and becoming largely flat relative to the water surface, under the correct application of pressure. The void between the faces is occupied by air or water and this evacuates as the flap 50 opens through the large aperture in the cranked baseplate at 100 on fig 4a Figure 8a and 8b show alternative arrangements for sinking buoyant flaps. The arrangement allows water flow to be channelled forwards acting in one direction wherein the flap 50 is forced into a flat position relative to the water surface, therewith extending the hydraulic piston 30, and pressurising the fluid contained in the connected pipe 40. The eddies and overflow also act to push down the flap 50 into a largely flat position relative to the water surface, by pushing against the flap 50, which by the angled face of its upside down V formation accepts lateral pressure and converts it to vertical pressure.

The flap 50 is hinged and formed of two faces and is situate inside the channel 38.

Therefore all flow through the channel 38 is directed over one or both of the faces to act in a downwards pressure. This necessitates that the flap 50 occupies the majority of the width of the channel 38. In the preferred embodiment the flap 50 is 5 mwide.

Means is ideally provided to enable the flap 50 to be opened with minimal resistance.

This may involve one-way perforations in the flap faces, in the hinge, elsewhere on the paddle 23, to allow air or water to escape quickly and with minimal resistance from beneath the flap 50 through aperture 100 as it is forced down by the movement of the paddle 23.

In the alternative the sides of the channel 38 may be striated or cellular in format to provide sideways exits of water or air from beneath the flap 50 faces as they are opened.

Since the orientation of the paddle arm 22 to the hinged flap 50 is about 110 degrees, both turning in an anticlockwise direction as shown on Figure 4, the wear on the main pivot 24 point or bearing will be significantly reduced.

The paddle 23 has a break point in the preferred embodiment, said break point enabling the paddle 23 to alter its presentation to water flows that are excessive and likely to damage the paddle 23 and/or generator 10.

This break point or fold point is provided by a hinge situate on the arms connecting the end with the float 20 (or counterweight) and apron 46 to the end with the flap 50.

The hinge is held in a position by the provision of a spring 48 which combines with flexible hooks 64 seated in catch holes on the side face of float 20, at the same end of the paddle 23. These hooks unseat or release from the catch holes allowing a release of the float end 20 of the paddle 23 from the connection to hydraulic cylinder(s) or piston(s) if the force of the water acting on the paddle 23 reaches a predetermined excessive level.

Ancillary locking devices may be provided or other configurations such as a leaf spring, sprung hook or flexible arm 64. The hooks slip from their seating on the float end 20 and the paddle folds, with the float end 20 of the paddle 23 being released free to pivot away from the pressure of the water flow.

The float end 20 in the preferred embodiment folds onto the roof of the channel 38 of the device. In this manner the flow continues through the paddle 23, passing between the space between the arms that connect the apron 46 to the flap 50, and exerting no pressure on the hydraulic piston(s).

The float 20 may comprise fins 70. The fins 70 catch each wave as it advances.

Thus more energy is transferred from the wave to the float 20, and thereby to the energy converter.

In the preferred embodiment the paddle 23 is formed with arms connecting the float and apron 46 and the flap 50 with a gap between the arms, and between the flap and the apron 46 -with the float 20 and angled surface facing the flap 50. This latter float 20 is formed with small drain holes on the top edge and in two sections, with a hermetically sealed horizontal part 20a (when viewed in the lowered position) and a largely open bottom edge of 20b. This allows a small amount of water to enter the float 20b, but not enough to impeded the movement of the float 20 upwards, and hence of the flap 50 downwards, corresponding to extension of the cylinder, and corresponding pressurisation of the cylinder fluid.

In a violent wave situation, when the float end 20 folds onto the roof of the channel 38, the largely open bottom edge has now turned upside down, so is at the top of the float 20b allowing it to become immediately and repeatedly inundated with seawater.

If the duration of the violent waves is only a few minutes the drain holes allow water to drain from the float 20b which has acted as a reservoir when the paddle 23 is in a folded position after excessive flow power has unseated the hooks and released the float end 20.

There is at least one spring 48 provided to tend the float 20 to a return and reformation of the paddle 23, said return spring(s) 48 being calibrated to return the paddle 23 to a generating configuration when the gravity acting on the float 20 provides a lesser counter force.

In this manner as water drains from the float 20, the return springs 48 act on the float end 20 of the paddle 23 and return it to the paddle's active situation where the flow of water may be used to extend the piston(s). In conditions of excessive and continuous water flow, ie a storm, the float 20b will continue to be filled by the flow over the top of the channel 38. Float 20 will also have operated slide 72 which will open trimming valve 68. This allows air to escape from the main ballast tank 54, or other buoyancy vessel, which within an hour, or other preset time, will cause the entire device to sink to the seabed. Here it will ride out the storm with impunity until raised by command from shore by pumping compressed air through an undersea pipeline. Thus the volume of water in the float is controlled by controlling the internal air pressure in the float cavity with a controllable compressor. The compressed air may be supplied to the float via an underwater pipe from a shore base compressor.

The float 20 in turn when the paddle 23 is in an active situation performs as a spoiler to the flow.

The generator 10 also includes a ballast. This ballast is adjustable to enable trimming of the height and angle of attack of the generating section in relation to wave direction, tidal direction, water surface level and preferably is capable of self-trimming using one or more valves 68.

In the preferred embodiment this ballast is typically formed of a truncated conical shape with the base 58 extending towards the sea-bed to impede wave travel and magnify their vertical motion, although cylinders may be equally appropriate. The base of the cone may be formed of a concrete or other heavyweight compound, whilst the majority of the cone contains varying levels of water and air, which combination may be trimmed or adjusted to ensure the generator 10 sits at the wave trough level or optimum level in the water for wave harvesting (delivery of pressurised water). There may also be one or more horizontal or close to horizontal plates or skirts fixed around the ballast to help prevent unwarranted movement or bobbing.

The weight of the ballast prevents unwarranted movement and/or bobbing with the inertia it provides meaning energy is harvested under flow movement rather than utilised to move the ballast / generator 10.

The invention has been described by way of examples only and it will be appreciated that variation may be made to the above-mentioned embodiments without departing from the scope of invention. With respect to the above description then, it is to be realised that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

CLAIMS1. A wave powered generator comprises: a buoyant housing having an entrance for receiving water from a wave and an outlet permitting the water to exhaust from the housing, said housing, in use, is tethered so that the entrance faces oncoming wave fronts and a float is supported on the generator by a rigid arm connected to the housing at a pivot, whereby an incident wave displaces the float, with respect to the structure, so as to establish a turning moment about the pivot; and an energy extractor is connected to the arm for extracting energy from the wave, characterised in that a dog-leg connection, located on the arm intermediate the float and the pivot, is arranged to disengage in high seas, so as to reduce the effective length of the pivot.
2. A wave powered generator comprises: a buoyant housing having an entrance for receiving water from a wave and an outlet permitting the water to exhaust from the housing, said housing, in use, is tethered so that the entrance faces oncoming wave fronts and a float is supported on the generator by a rigid arm connected to the housing at a pivot, whereby an incident wave displaces the float, with respect to the structure, so as to establish a turning moment about the pivot; and an energy extractor is connected to the arm for extracting energy from the wave, characterised in that a flap located between the entrance and outlet which, during a first interval presents relatively high impedance to the wave and during a subsequent interval presents relatively low impedance to the wave so as to optimise energy extraction.
3. A wave powered generator according to claim 1 has a flap located between the entrance and outlet which, during a first interval presents relatively high impedance to a wave and during a subsequent interval presents relatively low impedance to the wave so as to optimise energy extraction.
4. A wave powered generator according to claim 2 has a dog-leg connection, located on the arm intermediate the float and the pivot, is arranged to disengage in high seas, so as to reduce the effective length of the pivot.
5. A wave powered generator according to any preceding claim wherein the energy extractor includes a piston-in-cylinder arranged to pressurise a fluid which is subsequently transmitted to do work.
6. A wave powered generator according to claim 5 wherein the pressurised fluid turns a dynamo and generates electricity.
7. A wave powered generator according to claim 2 or 3 wherein the flap is located between the entrance and outlet so that the duration of the first interval and the duration of the second interval is variable according to the wavelength and/or amplitude of a wave.
8. A wave powered generator according to claim 7 wherein the flap is pivotable.
9. A wave powered generator according to claim 7 wherein the pivoting flap includes first and second plates.
1O.A wave powered generator according to claim 9 wherein the first and second plates are hinged.
11.A wave powered generator according to claim 10 wherein the hinge is capable of subtending an angle between 300 and 180°.
12.A wave powered generator according to any of claims 9 to 11 includes a means for urging the first and second plates, one towards the other.
13. A wave powered generator according to claim 1, or any claim dependent thereon, wherein the float is dimensioned and arranged to lie atop the housing, upon disengagement of the dog-leg.
14.A wave powered generator according to claim 2 or any claim dependent thereon, wherein the flap is adapted to open to an angle of substantially 180°, thereby minimising the impedance of the generator presented to an incident wave.
15.A wave powered generator according to claim I or any claim dependent thereon, wherein a first opening is defined in the float for permitting water to fill the float, whereby in use the float fills with water and is maintained in a non-deployed state until water drains therefrom via a second opening.
16.A float as in claim 15 comprising a means to control the volume of water in the float with compressed air supplied from a controllable compressor.
17.A means to supply compressed air to the float of claims 15 and 16 via an underwater pipe from a shore based compressor.
18.A wave powered generator according to any preceding claim includes vents formed in the housing, intermediate the flap and the outlet for permitting air to exhaust thereth rough.
19.A wave powered generator according to any preceding claim includes at least one buoyancy tank for trimming the generator with respect to a horizontal plane.
20.A wave powered generator according to claim 19 includes a filter for filtering sea water for use in the buoyancy tank.
21.A wave powered generator according to any preceding claim includes at least one aid for altering the angle of the generator with respect to an incident wavefront.
22.A wave powered generator according to any preceding claim includes at least one vane for altering an angle of incidence of the generator with respect to a wavefront.
23.A wave powered generator according to any preceding claim includes an accumulator which is arranged to be pressurised as a result of closing of the hinge.Amendments to the claims have been filed as followsCLAIMS1. A wave powered generator comprises: a housing having an entrance for receiving water from a wave and an outlet permitting the water to exhaust and a float that is supported on the generator by a rigid arm connected to the housing at a pivot, whereby an incident wave displaces the float, with respect to the housing, so as to establish a turning moment about the pivot; and an energy extractor is connected to the arm for extracting energy from the wave, characterised in that a connection, is arranged to disengage in high seas, so as to reduce the effective length of the rigid arm.2. A wave powered generator as in claim I wherein the connection is located intermediate the rigid arm and the float.3. A wave powered generator as in any preceding claim wherein the disengagement of the connection is characterised by the float and rigid arm * folding about the connection so as to adopt a safe passive condition.*.**.. * .S* S54*S * 4. A wave powered generator as in claim I wherein the connection is a hinge. 55..S S...5. A wave powered generator as in any preceding claim wherein the combination of the float and rigid arm form a paddle. * S. * . I S...6. A wave powered generator as in claim 5 comprising a spring arranged to return the paddle to the generating configuration from the safe passive condition.7. A wave powered generator as in any preceding claim wherein a first opening is defined in the float for permitting water to enter the float, whereby, in high seas, the float fills with water and is maintained in the safe passive condition until water drains from the float via a second opening after high seas have dissipated.8. A wave powered generator as in any preceding claim, wherein the float comprises a hermetically sealed section and a part that acts a reservoir incorporating openings and drain holes.9. A wave powered generator as in claim 8 wherein the part of the float that acts as reservoir is arranged to fill with water in high seas in order to maintain the paddle in the safe passive condition.10. A wave powered generator as in claims 8 and 9 wherein the part of the float that acts a reservoir is arranged to drain water after high seas have dissipated 11. A wave powered energy generator as in any preceding claim includes at least one ballast tank for trimming the generator with respect to a horizontal plane.12. A wave powered energy generator as in claim 11 includes a trimming valve to adjust the ballast to enable trimming the height of the generator in relation *:*** to water surface level. S...13.A wave powered generator as in any preceding claim wherein in use the housing is tethered so that the entrance faces oncoming wave fronts. * *.S... 14.A wave powered generator as in any preceding claim wherein the connection **I * is characterised as a dog-leg.15.A wave powered generator as in any preceding claim comprising a flap arranged between the entrance and the outlet so that during a first interval a high impedance is presented to the wave and during a subsequent interval a low impedance is presented to the wave.