GB2512110A

GB2512110A - A wave energy conversion system

Info

Publication number: GB2512110A
Application number: GB1305162.8A
Authority: GB
Inventors: O Elogab; H Elogab
Original assignee: Individual
Current assignee: O ELOGAB
Priority date: 2013-03-21
Filing date: 2013-03-21
Publication date: 2014-09-24
Anticipated expiration: 2033-03-21
Also published as: GB2512110B; GB201305162D0

Abstract

A wave energy conversion system 100 has an aerofoil shaped paddle 130 which is driven by wave movements. Waves push the concave face of the paddle 130, which drives a generator 200 via gearing 250, 260. The paddle may be biased to return to its starting position substantially perpendicular to the direction of wave propagation. A flap valve 150, 160 in the paddle allows water to flow in the reverse direction through the paddle with reduced obstruction. The paddle may be mounted close to the surface, and may follow variations in water level e.g. tidal changes. The paddle shape can reduce unwanted turbulence, and the convex face may include a ridge (510, figures 7 and 8)

Description

A WAVE ENERGY CONVERSION SYSTEM

The present invention relates generally to a system and method for capturing energy from waves propagating on the surface of water and finds particular, although not exclusive, utility in terminator wave energy conversion systems.

It is known to cxtract energy from waves propagating across the surface of a body of water such as a lake, sea or ocean. Wave energy conversion systems are categorised by the method used to capture energy from waves: (a) point absorber or buoy systems, in which the motion of a single (usually lO fioatin point rdative to a fixed structure is used; (b) surfacing following or attenuator systems, in which the motion of an elongate body (usually floating) and oriented paralld to the direction of wave propagation is used; (c) terminator systems, in which the motion of a body having an impingement surface is oriented substantially at right angles (i.e. substantially perpendicular to the direction of wave propagation; (d) oscillating water co'umn systems, in which rising and falling of water in a col turin, due to wave action, is used (for instance, to drive a turbine); arid (e) overtopping systems, in which water overtopping a structure, due to wave action, is used (for instance, in a similar manner to hydro-clectric power generation).

For instance, a known terminator wave energy conversion device for use in reEtively shallow water includes a base portion for anchoring to the bed of a body of water and an upstanding paddle portion pivotallv connected to the base portion. The paddle portion oscillates, backwards and forwards about the vertical in response to wave motion acting on its faces. Power extraction means extract energy from the movement of the paddle portion. \Vhen the base portion is anchored to the bed of a hotly of water with the paddle portion facing the wave motion, the base portion and the paddle portion extend vertically through at kast the entire depth of the water, to present a substantially continuous surface to the wave motion throughout the full depth of water from the wave crest to the sea bed.

The force acting on a fiat paddle due to a passing wave is based exclusively on the resistance offered by the \vater against relative movement of the paddle therethrough. Eddy currents, turbulence and vortices are created around the peripheral

I

edges of a paddle as water moves past it. Such eddy currents, turbulence and vortices naturally result in loss of power.

According to a first aspect of the present invention, there is provided a energy conversion system for capturing energy from waves propagating on the surface of water, the system comprising: a support structure, securable in a fixed position relative to land; a paddle pivotally mounted on the support structure about a first axis, the paddle having a first face, a second face and a substantially aerofoil shape cross section in a plane substantially at right angles to the first axis, the first face and the second face; and an energy transfer system coupled to the paddle, the energy transfer i0 system for conveying oscillatory motion of the paddle to an electrical energy generation unit; wherein in use the paddle is at least partially arranged in the water such that waves propagating on the surface of the water impinge the first face of the paddle, the first face oriented substantially at right angles to the direction of wave propagation, such that the paddle is caused to oscillate about the first axis.

As a wave propagates across the surface of a body of water, water is carried with it. As the wave impinges the first face of the paddle, the paddle is pushed by the water from its initial position, in which the £11-st face is oriented substantially right angles to the direction of wave propagation. Passage of the wave causes the Paddle to rotate about the first axis. Water carried by the wave flows around the edges of the paddle.

The aerofoil shape cross section helps avoid the formation of turbulence, vortices or eddy currents around the paddle. In particular, the aerofoil shape cross section enables laminar flow of water around the paddle. Accordingly, an increase in power transfer from the wave to the paddle may be achieved. As the wave peak passes, and the paddle encounters a trough, the paddle is pushed by the water back to its initial position, in which the first face is oriented substantially at right angles to the direction of wave propagation.

The wave energy conversion system may he a tertninator system. In this way, the fotprint of the system on the water surface may he rninimised.

The support structure may be securable in a fixed position relative to land in that it may he securable in a fixed position on the sea/ocean/lake bed and/or securable in a fixed position on an island, headland, cliff, beach, wall, pier, groyne, or other coastal land region.

The first face tnay be substantially concave. In this way, water carried by the may he scooped by the paddle to enable a high proportion of energy conversion.

The concave face may be a first wall that is curved about a second axis spaced from, and parallel to, the first axis. The first wall may have uniform curvature, or may have varying curvature.

The second face may be substantially convex. In use, the second face may be arrangcd behind the first face relative to the direction of wave propagation. Thc second face may he oriented substantially at right angles to the direction of wave propagation such that incident waves do not impinge the second face. In this way, flow of water in a reverse direction may be deflected around the paddle, and movement of the paddle may push water adjacent the second face around the paddle, to ease rotation of the paddle about the first axis. The convex face may he a second wall that is curved about a third axis spaced from, and parallel to, the first axis and/or the second axis.

The aerofoil cross section of the paddle may have a thickness at an end adjacent the first axis greater than a thickness at an opposing end. In this way, the paddle may he supported about the first axis at a more rigid and/or robust end.

The aerofoil cross section may have a rounded cnd that tapers to a point at an opposing end.

The aerofoil cross section of the paddle may he uniform along the first axis. For instance, the paddle may be substantially prismatic in cross section such that the paddle has the same cross section independent of where the cross section substantially at right angles to the first axis, the first face and the second face is taken. Alternattvely, the profile of the paddle may vary along the first axis. In this way, the aerofoll cross section may he matched to the expected size, power and/or speed of incident waves. In particular, in embodiments in which the first axis is arranged vertically, the aerofoil cross section may vary with depth. Alternatively or additionally, the proportion of the paddle submerged in the water may he varied to expose different aerofoil cross section profiles to incident waves of varying size, power and/or spced.

The paddle may further comprise a passage for allowing the flow of water thercthrough between the first face and die second face. In this way, water by die paddle, for instance in the concave facc of die paddle, is allowed to escape through die passage, thereby reducing rcsistance to movement of the paddle.

The paddle may further comprise a valve disposed within the passage that is configured to selectively allow water to flow thnrngh the passage. In this way, selecth)n of when \vater is alh)wed to escape through the passage is enabled.

The valve may he configured to he actuated in response to a lressure applied to the valve exceeding a predetermiied threshold. Tn this way, water may he allowed to escape through the passage only when it has been caught by the paddle, for instance in the concave face of the paddle.

The valve may he configured to he actuated in response to an amount of rotation of the paddle about the first axis. In this way, whcn the valve opens may be, at lO least partially, pre-dctcrmincd such that it does not open in inappropriate circumstances.

The valve may be a one-way valve. In this way, only water caught on one side of the paddle may he allowed to escape.

The valve may he a hinged flap. In this way, minimal moving parts may he used to perform the function of a valve. This is desirable where failure of the valve would he difficult to repair, such as where the valve is underwater, or where failure of a complex valve is likely, such as where the valve is in constant use and/or in extreme Physical conditions, for instance when exposed to corrosive salt water. For example, the hinged flap may come to rest on a face of the 1tddle adjacent the passage, such that it may only open away from the face.

In use, the first axis may be substantially at right angles to the water surface. In this way, natural motion of the paddle may be harnessed. In particular, a free body will arrange itself at right angles to the direction of the incident waves (i.e. with its length parallel to the wave front), and will move forward and backwards as the wave passes. If the body is coupled at one end to a vertical shaft, then wave motion will cause the body to rotate about the shaft.

Tn use, the first axis may he substantially parallel to the water surface. In this way, the first axis may he securahle in a fixed position relative to land without a need for contact with the bed of the sea, hilcc or ocean.

The paddle may he self-orienting. In particular, the paddle may be configured to face the direction from which incident wavcs arc propagating. Alternatively or additionally, the system may include an orientation mechanism for orienting the paddle to face the direction from which incident waves arc propagating. For instance, the orientation mechanism may comprise a weather vane, such that the paddle is oriented with respect to wind direction. This is because wind direction approximates the direction of incident short wavelength waves. The orientation mechanirn may he nunually controllable.

Tn use the paddle may he arranged at the water surface. In particular, the paddle may he disposed just below the water surface and/or extending across the water surface such that a substantial portion of the paddle is arranged beneath the water. In this way, the greatest amount of energy can be captured by the paddle. In particular, energy present in a surface wave decreases with the depth of the water in which it travels. In one embodiment, the paddle extends from an axis, which is horizontally disposed above lO the water surface, into the water. Alternatively or additionally the paddle may be arranged entirely beneath the water surface. The paddle may be spaced from the water surface.

The paddk may he configured to he surface-following. In this way, the paddle may track the surface of the water to enable the greatest amount of energy to he captured by the system, irrespective of any variation in the height of waves, tidal movement, and/or flood/drought conditions.

The paddle may be configured to be substantially buoyant. In this way, automatic surface-following is enabled. The ptiddle may he substantially neutrally buoyant. Alternatively or additionally, the system may comprise a water sensor and a actuator unit for enabling the paddle to be surface-following.

The paddle may be configured to rotate about the first axis from a first position to a second position having an angular separation of between approximately 10 degrees and 90 degrees. In particular, the paddle may he configured to rotate about the first axis from a first position to a second position having an angular separation of between approximately 20 degrees and 60 degrees or, more particularly, between approximately degrees and 45 degrees.

The paddle may he rotationally biased about the first axis. In particular, the paddle may be configured to return to the first position subsequent to deflection to the second position by an incident wave. In this way, die paddle may be in an optimal initial position prior to the arrival of each incident wave. The rotational biasing of the paddle about the first axis may be by any conventional means, such as spring or riser hinge, and niay he adjustalale. In particular, the biasing niay he adjustable in response to variation in incoming waves.

The paddle may further comprise a deflector located on the second face, for channelling water across the second face. The deflector may emphasize the effect of the convex face on the flow of water around the paddle.

The deflector may he a ridge. In particular, the ridge may he cusp like. For instance, in the aerofoil cross section, the ridge may he described as a line that on one side of a singularity has positive gradient and positive rate of change of gradient, and that on thc other side of the singularity has negative gradient and negative rate of change of gradient.

The system may be configured to be matchablc to a variety of waves and or swell sizes. The system may be matched to waves having a period of between approximately Is and 30s, more particularly between approximately 3s and lOs, and in particular approximately Bs. Movement of the paddle may he synchronised with incident waves.

The first face may have a length (substantially at right angles to the first axis) between approximately Im and 30m, more particularly between approximately 2m and 15m, in particular between approximately 3m and 5m. The first face may have a width (substantially parallel to the first axis) bctwccn approximately O.5m and lOm, more ptrtit:ul an y between approximately 1111 at it] 3m, in trticuiar between approximate1 y 2m11 and 3m. The system may comprise alloy, high carbon steel alloy, carbon fibre, fibre glass, composite materials, plastics materials and/or any other suitabkt material.

The energy transfer system may comprise any suitable energy transfer system, for instance a hydraulic ram, elastomeric hose pump, pump-to-shore, rotary gear, rack and pinion gear, straight or chain gear, mechanical transfer system, hydraulic transfer system and/or air pump.

The system may further comprise an electrical energy generation unit for receiving oscillatory motion from the energy transfer system and converting it into electricity.

The system may further comprise a reflecting wail arranged such that incoming waves are reflected toward the second face. In this way, reflected waves may be used to assist moving the paddk from its displaced position hack to its initial position. The reflecting wall may he spaced from the paddk by a distance that is matched to the wavelength of the incident waves. In particular, this spacing may he variable dependent on prexailing s\xrell The reflecting wall may be substaruiially concave, parabolic and/or polygonal in plan. In particular, the wall may be shaped to focus incident waves onto the second face of the paddle.

The system may he arranged on a shoreline, near shore or offshore.

The system may further comprise a plurality of paddles pivotally mounted on the support structure about the first axis. In this way, more paddles may be used by ganging them together one atop the other. This is of use in deep water, where energy conveyed in a surface waves decreases less with depth than in shallow water.

According to a second aspect of the present invention, there is provided a method of capturing energy from waves propagating on the surface of water, the method comprising: providing a wave energy conversion system according to any preceding claim; securing the support structure in a fixed position relative to the land; arranging the paddle at least partially in the water such that waves propagating on the surface of the water impinge the first face of the paddle, the first face oriented substantially at right angles to the direction of wave propagation, such that the paddle is caused to oscillate about the first axis; conveying oscillatory motion of the paddle to an electrical energy generation unit.

The above arid other characteristics, features and advantages of the presett invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

Figure 1 shows 15 different cross sectional profiles of known aerofoils.

Figure 2 shows 14 further different cross sectional profiles of known aerofoils.

Figure 3 shows a first wave energy conversion system in accordance with the preseirt mention.

Figure 4 shows a second wave energy conversion system in accordance with the preseirt mention.

Figure 5 shows a cross sectional profile of a first paddle in accordance with the present invention.

Figure 6 shows a perspective view of the first paddle of figure 5.

Figure 7 shows a cross sectional profile of a second paddle in accordance with the present invention.

Figure 3 shows a perspective view of the second paddle of figure 7.

The present invention will he described vitl respect to paiticular embodiments and with reference to certain drawings hut the invention is not limited thereto hut only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may bc exaggerated and not drawn to scale for ill ustrative purposes. The dimensions and the relative dimensions (10 not correspond to actual reductions to practice of thc invention.

lO Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to he understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims arc used for descriptive purposes and not necessarily for describing relative p005 It is to he understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to he interpreted as specifying the presence of the stated features, integers, steps or components as referred to, hut does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not he limited to devices consisting only of components A and B. It means that with respect to the prescnt invention, the only relevant components of the device are A and B. Similarly, it is to be noticed that the tcrm "connected", used in the description, should not he interpreted as being restricted to direct connections only. Thus, thc scope of the expression "a device A connected to a device B" should not bc limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. "(nnected" may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other hut yet still co-operate or interact with each other.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an i0 embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may refer to different embodiments.

Furthermore, the particular features, structures or characteristics of any embodiment or aspect of the invention may he combined in any suitable manner, as would he apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly, it should he appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure arid aiding iii the understanding of uric or more of the various inventive aspects. This method of disclosure, however, is not to he interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects he in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some enibodinnents described herein include sonic features included in other embodiments, combinations of features of different ennhodinients are meant to he within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can he used in any combination.

In the description provided herein, numerous specific details are set forth.

Hoxvever, it is understood that embodiments of the invention may he practised without these specific details. In other instnnces, well-known methods, structures and techniques have not been shown in detail iii order not to obscure an understanding of

this description.

In the discussion of the invention, unless stated to the contrary, the dischmure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parveter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

i0 The use of the term "at least one" may, in some embodiments, mean only one.

The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can he configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching of the invention, the invention being limited only by the terms of the appended claims.

Figure 1 shows 15 different cross sectional prohles of known aerofoils. Each aerofoil includes a rounded leading edge, shown to the left in the figure, tapering to a poited trailing edge, shown to the right iii the figure. Shown are cross sections through wings of: 1. an ultra-lightweight aviation aircraft; 2. an Airbus (1CM) A321; 3. a propeller blade; 4. a Lockheed (RTM) F-l04 Starfighter; 5. a Zhukovsky (orJowkowski aerofoil centred at -O.25+i; 6. a Zhukovsky (orjowkowski) aerofoil centred at -0.25+0.5i; 7. a Zhukovsky (orjowkowski) aerofoil centred at -0.25; 8. a blackbird; 9. a turbofan fan blade; 10. a Clark Y aerofoil; 11. a NACA 6409 aerofoil; 12. a Gdttingen 549 aerofoil; 13. a turbine blade; 14. a dolphin flipper fin; and 15. a mainsail.

Similarly, figure 2 shows 14 different cross sectional profiles of known aerofoils.

Each aerofoil includes a rounded leading edge, shown to the left in the figure, tapering to a pointed trailing edge, shown to the right in the figure. Shown are cross sections through wings of: 16. a RC park flyer; 17. aRC pylon racer; 18. a propeller aircraft; 19. a jet airliner; lO 20. a.flyingwing; 21. an aft loaded aerofoil; 22. a transonic aircraft; 23. a supersonic aircraft; and 24-29. designs by lloratio Phillips in 1884.

Various modifications and adaptations of the above aerofoil cross sections are envisaged in the working of the present invention.

Figure 3 shows a first wave energy conversion system 100 in accordance with the present invention. The s stern 100 comprises a base support 110 sunk into a sea bed, and a vertical axle!20 rotatably mounted in the base support!10. Connected to the axle 120 is a paddle 130. The paddle 130 has an aerofoil cross section and is arranged to rotate with the axle 120 in response to a force on a front face (not shown) or a back face 140 of the paddle 130. The paddle 130 includes a hole 150 therethrough, extending from the front face to the back face 140. A flap 160 is disposed within the hole 150 and secured by hinges 170 along its upper edge. In the absence of water flow around the paddle 120, the flap 160 will hang down front the hinges 170 and seal the hole 150. In the presence of water flow toward the front face of the paddle, the flap will be urged into the hole 150 to seal the hole 150 securely. In the presence of water flow toward the back face 140 of the paddle 120, the flap 160 is urged to an open position (shown in figure 3) in which water nnay flow through the hole 150.

Continuation of the hole 150 and the flap iôü on the far side of the flap are shown in dotted lines, for clarity.

An upper end of the axle 120 leads into a conversion module 180 within which rotational motion of the axle 120 is converted into electricity that is transferred away via a cable 190 for use external to the system 100. In particular, the conversion module 180 includes an electrical energy generatton unit 200 and an energy transfer system 210 for conveying oscillatory motion of the axle 120 to the electrical energy generation unit 200.

The conversion module 180 is shown cut away for clarity. Axle 120 is held in place by an anti-friction hearing 220. Adjacent the anti-friction hearing is a fly energy storage unit 230 and a safety break system 240. Energy transfer system 210 is preferably a one-direction gearbox that transfers rotational motion of the axle 120, in one rotational direction only, to the electrical energy generation unit 200. Tlowever, in figure 3, the energy transfer system 210 is shown as a pair of co-operating gears, for the purpose of clarity: a large gear 250 directly coupled to the axle 120 and a small gear 260 directly coupled to the electrical energy generation unit 200. In this way, low rotational speeds of the axle 120 are converted into high rotational speeds within the electrical energy generation unit 200.

The electrical energy generation unit 200 is also shown cut away for clarity, and comprises a conventional electric motor of the type having a rotor and a stator, rotation of the rotor within the stator inducing an electrical current in the cable 190.

Figure 4 shows a second wave energy conversion system 300 in accordance with the present invention. The system 300 comprises p1dles 130 substantially the same as the Paddle 130 shown in figure 3. The paddles 130 are arranged about the same axle 120, one atop the other, such that they arc configured to rotate together. The upper paddle 130 has a height greater than the lower paddle 130. In figure 4, large gcar 250 cooperates with a straight or chain gear 310, for instance in a rack and pinion arrangement. Rotation of the axle 120, as discussed above, is converted into linear reciprocal motion of the straight or chain gear 310.

The straight or chain gear 310 is in turn connected to a piston 320 within a cylinder 330. As the piston 320 is withdrawn from the cylinder 330, air is drawn into the cylinder 330 through air inlet 340 via the inlet valve 350. As the piston 320 is reinserted into the cylinder 330 (as shown by dottcd lines), the air within thc cylinder 330 is pushed out via outlet valve 360 into outlet pipe 370. The air then passes to an air drier 380 and on to an air filter 390 via a pressure sensor 400. After passing through the air filter, the prcssuriscd air is passed to a super charger 410 and then to a turbine assembly 420. The energy contained within the pressurised air is converted into rotational motion of the turbine, which can then he fed into a gearbox 430 that can convert the rotational motion to a speed appropriate for passing to an electrical energy generation unit 200 in the form of an electrical generator. An amplifier may be used prior to the electricity being passed to cable 190.

The previous embodiments are to he understood to he examples of the many arrangements that may he envisaged in the execution of the present invention.

An alternative arrangement for the energy transfer system sho\vn in figure 4-is also envisaged. In the alternative arrangement, the straight or chain gear 310 is connected at one end to a first piston 320 within a first cylinder 330, as in figure 4.

However, the straight or chain gear 310 is also connected at an opposing end to a lO second piston within a second cyhnder, which is a mirror image of the first piston and cylinder.

As the first piston 320 is withdrawn from the first cyhnder 330, air is drawn into the first cylinder 330 through the first air inlet 340 via the first inlet valve 350.

Withdrawal of the first piston 320 is caused by movement of the straight or chain gear 3! 0 to the right in figure 4, which also causes the second piston to he inserted into the second cylinder. The air within the second cylinder is pushed out via the second outlet valve, which also leads into common outlet pipe 370, such that it can then be passed to the air drier 380.

As the first piston 320 is reinserted into the first cylinder 330 (as shown by dotted lines), the air within the first cylinder 330 is pushed out via the first outlet valve 360 into the common outlet pipe 370, to then be passed to the air drier 380.

Reinsertion of the first piston 320 into the first cylinder 330 is caused by movement of the straight or chain gear 310 to the left in figure 4, which also causes the second piston to he withdrawn from the second cylinder. Air is thus drawn into the second cylinder through the second air inlet via the second inlet valve.

In this way, movement of the paddle in both directions can drive air into the turbine assembly 420 in order to generate power.

Figure 5 shows a cross sectional profile of the paddle 130 in accordance with the present invention. The paddle 130 comprises a concave face 4-40, a convex face 450, a rounded end 460 and a tapered end 470. The paddle 130 comprises a passageway 480 through which the axle 120 may he passed.

Figure 6 shows a perspective view of the paddle 130 of figure 5, in which the hole 150 can he seen extending therethrough from the concave face 440 to the convex face 450. The flap 160 partially obscures the hole 150. For clarity, obscured parts of the hole 150 and the passageway 480 have been shown in dotted lines.

Figure 7 shows a cross sectional profile of a second paddle 500 that differs from the paddle 130. The second pad lie 500 includes a concave face 4-40, a convex face 450, a rounded end 4-60 and a tapered end 470. The second paddle 500 comprises a passageway 480 through wlMch the axle 120 may be passed.

Figure 8 shows a perspective view of the second paddle 500 of figure 7.

The ridge 510 has an arête-like edge from which two concave wall portions extend, jonnng up with the convex face 450 to form a smooth and continuous surface.

Claims

CLAIMS1. A wave energy conversi n system for capturing energy from waves propagating on the surface of water, the system comprising: a support structure, securable in a fixed position relative to land; a paddle pivotally mounted on the support structure about a first axis, the paddle having a first face, a second face and a substantially aerofoil shape cross section in a plane substantially at right angles to the first axis, the first face and the second face; and an energy transfer system coupled to the paddle, the energy transfer system for conveying oscillatory motion of the paddle to an electrical energy generation unit; wherein in use the paddle is at least partially arranged in the water such that waves propagating on the surface of the water impinge the first face of the paddle, the first face oriented substantially at right angles to the direction of wave propagation, such that the paddle is caused to oscillate about the first axis.
2. The wave energy conversion system of claim t, wherein the first face is substantially concave.
3. The wave energy conversion system of claim I or claim 2, wherein the second Lace is substantially convex and, in use, the second face is arranged behind the first face relative to the direction of wave propagation.
4. The wave energy conversion system of any preceding claim, wherein the aerofoil cross section of the paddle has a thickness at an end adjacent the first axis greater than a thickness at an opposing end.
5. The wave energy conversion system of claim 4, wherein the aerofoil cross section of the paddle is uniform along the first axis.
6. The wave energy conversion system of any preceding claim, wherein the paddle further comprises a passage Lot allowing a flow of water therethrough between the first face and the second face.
7. The wave energy conversion system of claim 6, wherein the paddle further comprises a valve disposed within the passage that is configured to selecfively allow water to flow through the passage.
8. The wave energy conversion system of claim 7, wherein the valve is configured lO to be actuated in response to a pressure applied to the valve exceeding a predetermined threshold.
9. The wave energy conversion system of claim 7 or daini 8, wherein the valve is configured to he actuated in response to an amount of rotation of the paddle about the first axis.
10. The wave energy conversion system of any one of claims 7 to 9, wherein the valve isa one-way valve.
II. The wave energy conversion system of any one of claims 7 to 10, wherein the valve is a hinged flap.
12. The wave energy conversion system of any preceding daim, wherein in use the first axis is substantially at right angles to the water surface.
13. The wave energy conversion system of any one of claims I to II, wherein in use the first axis is substantially parallel to the water surface.
14. The wave energy conversion system of any preceding claim, wherein in use the paddle is arranged at the water surface.
15. The wave energy conversion system of any preceding claim, wherein the paddle is configured to he surface-following.
16. The wave energy conversion system of claim 15, wherein the paddle is configured to be substantially buoyant.
17. The wave energy conversion system of any preceding claim, wherein the paddle is configured to rotate about the first axis from a first position to a second position having an angular separation of between approximately 10 degrees and degrees.
18. The wave energy conversion system of claim 17, wherein the paddle is rotationally biased about the first axis, such that the paddle is configured to return to the first position subsequent to deflection to the second position by an incident wave
19. The wave energy conversion system of any preceding claim, wherein the paddle further comprises a deflector located on the second face, for channelling water across the second face.
20. The wave energy conversion system ofclaini Ic, wherein the deflector is a ridge.
21. The wave energy conversion system of any preceding claim, further comprising an electrical energy generation unit for receiving oscillatory motion from the energy transfer system and converting it into electricity.
22. The wave energy conversion system of any preceding claim, further comprising a reflecting wall arranged such that incoming waves are reflected toward the second face.
23. The wave energy conversion system of claim 22, wherein the reflecting wall is substantially concave, parabolic and/or polygonal in plan.
24. The wave energy conversion system of any preceding claim, further comprising a plurality of paddles pivotally mounted on the support structure about the first axis.
25. A wave energy conversion system substantially as hereinhefore described with reference to any one or more of figures 3 to 8.
26. A method of capturing energy from waves propagating on the surface of water, the method comprising: lO providing a wave energy conversion system according to any preceding claim; securing the support structure in a fixed position relative to the land; arranging the paddle at least partially in the water such that waves propagating on the surface of the water impinge the first face of the paddle, the first face oriented substantially at right angles to the direction of wave propagation, such that the paddle is caused to oscillate about the flrst axis; conveying oscillatory motion of the paddle to an electrical energy generation unit.