GB2480325A

GB2480325A - Water motion energy conversion apparatus

Info

Publication number: GB2480325A
Application number: GB1008130A
Authority: GB
Inventors: Brian Richard Ferrier
Original assignee: FERRIER PUMPS Ltd
Current assignee: FERRIER PUMPS Ltd
Priority date: 2010-05-14
Filing date: 2010-05-14
Publication date: 2011-11-16
Also published as: GB201008130D0

Abstract

Water motion energy conversion apparatus 10 comprises a flap 16 pivotally connected to a base portion for oscillation to and fro about in dependence on eg waves acting on a face of the flap. Energy is extracted, eg by a hydraulic motor, a flywheel energy store and an electrical generator. The flap 16 comprises a support portion 50 and at least one flap portion 54 which is movable in relation to the support portion 50 between a first disposition when flap is being driven towards the bed of the body of water and a second disposition when the flap is returning such that the surface area of a face of the flap that is acted upon by the water motion is larger in the first disposition than in the second disposition. The flap may comprise three fixed cylindrical buoyant chambers 52 and three rotatable comma-shaped buoyant flap portions 54 spaced alternately apart on a frame 50. Flap setting arrangements 56, 66 move the flap portions 54 between their first and second dispositions, figs. 2A, 2B, respectively. In a modification, six comma-shaped buoyant flap portions 54 are provided without cylindrical chambers.

Description

Water motion energy conversion apparatus

Field of the invention

The present invention relates to water motion energy conversion apparatus configured, in particular but not exclusively, to convert wave motion into electricity.

Background to the invention

There are various known approaches to harnessing energy from wave movement. One such approach is described in WO 2006/1 00436, which relates to apparatus for generating power from wave movement. The apparatus of WO 2006/100436 has a base portion that sits on the sea bed in comparatively shallow water and an upstanding flap portion that is pivotally connected to the base portion. The flap portion is biased to the vertical and oscillates to and fro about the vertical in dependence upon wave motion acting on its faces. Oscillation of the flap portion is coupled by a linkage to a hydraulic ram that reciprocates in a cylinder that forms part of a hydraulic circuit. The hydraulic circuit further comprises a variable hydraulic motor, which is typically located on dry land to thereby provide for ease of maintenance and recovery of electrical energy from the hydraulic motor and associated components. In use, oscillation of the flap * ** portion causes a corresponding one way flow of fluid in the hydraulic circuit to thereby drive the hydraulic motor, which in turn drives a flywheel that stores energy from the hydraulic motor until it is converted into electricity by an induction generator connected to the flywheel. S. S

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The present inventors have appreciated that wave energy conversion apparatus, such as that described in WO 2006/100436, have shortcomings.

It is therefore an object for the present invention to provide improved water motion energy conversion apparatus comprising a flap portion, the water motion energy conversion apparatus being configured such that the flap portion oscillates to and fro in dependence on water motion acting on its surfaces.

Statement of invention

According to a first aspect of the present invention there is provided water motion energy conversion apparatus comprising: a base portion configured to be anchored to the bed of a body of water; a flap arrangement pivotally connected to the base portion and configured to, in use, oscillate to and fro about its pivotal connection in dependence on water motion acting on a face of the flap arrangement; and energy extraction apparatus operative to extract energy from movement of the flap arrangement, in which the flap arrangement comprises a support portion and at least a first flap portion, the first flap portion being movable in relation to the support portion between a first disposition when the flap arrangement is being driven towards the bed of the body of water by water motion and a second disposition when the flap arrangement is rising from the bed of the body of ::.::; water, a surface area of a face of the flap arrangement that is acted upon by the water motion being larger in the first disposition than in the second disposition.

In use, the base portion is anchored to the bed of a body of water, such as the sea bed, and the flap arrangement is driven by water motion, such as wave motion, acting on its face towards the bed of the body of water.

During this first phase of movement, the flap arrangement is in the first disposition such that it presents a large surface area to the water motion.

When the flap arrangement is rising from the bed of the body of water, the flap arrangement is in the second disposition, in which the face of the flap arrangement presents a smaller surface area to the body of water. Hence, the flap arrangement is able to comptete this second phase of movement more quickly than if the surface area of the flap arrangement were the same as in the first disposition, e.g. according to the arrangement described by WO 2006/100436. Thus, it can be appreciated that reducing the surface area of the face of the flap arrangement when the flap arrangement is rising from the bed of the body of water can provide for an increase in energy conversion efficiency of the energy conversion apparatus.

More specifically, the flap arrangement may be biased to the vertical when in use. Hence, the flap arrangement may oscillate to and fro about the vertical. The flap arrangement may be configured to be positively buoyant in water, e.g. sea water, to thereby provide for biasing of the flap arrangement to the vertical. In the first disposition, water motion may drive the flap arrangement towards the bed of the body of water against the positive buoyancy. In the second disposition, the positive buoyancy may raise the flap arrangement towards the vertical before the cycle : * recommences. More specifically, the flap arrangement may define at least one chamber configured to be filled with a positively buoyant material, such as air.

Alternatively or in addition, the flap arrangement may be configured such that respective surface areas of opposing faces of the flap arrangement that are acted upon by water motion are smaller in the first disposition than in the second disposition.

Alternatively or in addition, the flap arrangement may comprise a plurality of flap portions, each of the flap portions being movable in relation to the support portion between the first and second dispositions. The energy conversion apparatus may be configured such that the plurality of flap portions all move together between the first and second dispositions. The plurality of flap portions may be spaced apart from each other in a particular direction. The flap arrangement may comprise at least one buoyancy portion, the buoyancy portion being disposed between neighbouring flap portions. Hence, flap arrangement may comprise a plurality of buoyancy portions, each buoyancy portion being disposed between different pairs of neighbouring flap portions.

Alternatively or in addition, the first flap portion may comprise an elongate member that extends longitudinally in a direction generally perpendicular to a direction of water motion that drives the flap arrangement when in the first disposition.

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Alternatively or in addition, the first flap portion may be pivotally mounted * on the support portion. Thus, the first flap portion may move between the first and second dispositions by pivoting in relation to the support portion.

:. Alternatively or in addition, the first flap portion may define first and second :**:; opposing surfaces, the first surface being acted upon by water motion * during movement of the flap arrangement towards the bed of the body of water. More specifically, at least one of the first and second surfaces may define an arcuate surface. The first surface may define a convex surface.

In use, the water motion may act against the convex surface. The second surface may define a concave surface. In use, water may pass the concave surface when the flap arrangement is rising from the bed of the body of water. The flap portion may be of comma shaped cross section.

Alternatively or in addition, the flap arrangement may define an enclosed space filled with a positively buoyant material, such as air.

Alternatively or in addition, the energy conversion apparatus may comprise a flap setting arrangement that is operative to move the flap portion to the second disposition. The flap setting arrangement may be operative when the flap arrangement is nearest the sea bed during its to and fro oscillation. Hence, the flap setting arrangement may be operative such that the surface area of the face of the flap arrangement is reduced when the flap arrangement is rising from the sea bed. The flap setting arrangement may be operative to move the flap portion to the first disposition when the flap arrangement is at or near the vertical. The flap setting arrangement may comprise a first protrusion on the base portion and a first mechanical linkage arrangement on the flap arrangement that is operative to move the flap portion. The first protrusion and first mechanical linkage arrangement may be disposed on the energy conversion apparatus such that the first protrusion bears against a part of * the mechanical linkage arrangement to thereby move the mechanical :.: 25 linkage arrangement, which in turn moves the flap portion. The first protrusion and first mechanical linkage arrangement may be configured to :. move the flap portion to the second disposition. The flap setting :**:; arrangement may comprise a second protrusion on the base portion and a * second mechanical linkage arrangement on the flap arrangement that are configured to operate in the same fashion as the first protrusion and first mechanical linkage arrangement but with the second protrusion and the second mechanical linkage arrangement being disposed on the base portion and the flap arrangement respectively so as to effect movement of the flap portion to the first disposition.

Alternatively or in addition, the flap arrangement may define a generally rectangular footprint.

Alternatively or in addition, the energy conversion apparatus may be configured such that, in use, the base portion and the flap arrangement extend vertically through at least the entire depth of the body of water.

Hence, the flap arrangement may present a substantially continuous surface to the water movement throughout the entire depth of water from the surface of the body of water to the sea bed.

Alternatively or in addition, the energy extraction apparatus comprises: a hydraulic motor driven by hydraulic fluid, the hydraulic fluid being driven by movement of the flap arrangement; a flywheel energy store mechanically coupled to the hydraulic motor; and an electrical generator driven by the flywheel.

The water motion energy conversion apparatus may further comprise a pressure line, a return line and a hydraulic motor in fluid communication with each of the pressure and return lines, water present in the pressure and return lines being operative, in use of the energy conversion apparatus, to drive the hydraulic motor, the energy conversion apparatus : * further comprising at least one non return valve, which comprises a valve disc and a seat, in one of the pressure and return lines, in which the non * return valve comprises first and second biasing devices, the first biasing device being operative to hold the valve disc against the seat and the second biasing device becoming operative to bias the valve disc towards the seat when the valve is at least 50 percent open. The second biasing device may have a spring constant at least twice as great as a spring constant of the first biasing device. The second biasing device may have a spring constant substantially five times a spring constant of the first biasing device.

More specifically, a first valve is disposed in the pressure line and a second valve is disposed in the return line. Where a non return valve comprising a single biasing device is used in each of the pressure and return lines, an insufficiently short valve closing time can cause rams in fluidic communication with the pressure and return lines to work against each other, thereby giving rise to a further source of water hammer.

Alternatively or in addition, the biasing device may comprise a coil spring.

Alternatively or in addition, the valve may be configured such that the second biasing device becomes operative to bias the valve disc towards the seat when the valve is at least 75 percent open. More specifically, the second biasing device may become operative to bias the valve disc towards the seat when the valve is substantially 85 percent open.

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Alternatively or in addition, the valve may comprise a valve shaft attached * to the valve disc, the valve shaft being configured such that only the first :.: 25 biasing device of the first and second biasing devices exerts a bias on the valve shaft when the valve is no more than 50 per cent open and such that :. both the second biasing device exerts a bias on the valve shaft when the valve is at least 50 per cent open. More specifically, the valve may comprise a first shaft portion and a second shaft portion, the first and second portions engaging with each other and being movable in relation to each other in a direction of opening and closing of the valve. The first shaft portion may be attached to the valve disc and the second shaft portion may be spaced apart from the valve disc. The first biasing device may bear between the first shaft portion and the second shaft portion and the second biasing device may bear between the second shaft portion and a body of the valve. Hence, the first shaft portion bears against the bias exerted by the first biasing device such that the valve disc bears against the bias exerted by the first biasing device as the valve disc moves during a first phase of opening, e.g. between 0 percent and 85 percent open.

Then the first shaft portion bears against the second shaft portion such that the second shaft portion bears against the bias exerted by the second biasing device such that the valve disc bears against the bias exerted by the second biasing device as the valve disc moves during a second phase of opening, e.g. between 85 percent and 100 percent open.

Alternatively or in addition, the non return valve may define an aperture portion, which in use receives a flow of fluid from the pressure or return line, the aperture portion defining an aperture surface extending towards the valve seat, the aperture surface having a profile that is operative to provide for a Venturi effect when the valve is at least 50 percent open.

More specifically, the aperture surface may have a profile that is operative *:*. to provide for a Venturi effect when the valve is at least 75 percent open, such as at least substantially 85 percent open. Thus, the Venturi effect : may contribute to the reduction in water hammer. 25

Alternatively or in addition, the non return valve may comprise a diffuser :. that defines an outwardly facing surface, the outwardly facing surface defining an uneven surface. More specifically, the uneven surface may be formed by at least one recess. For example, the at least one recess may be defined by a plurality of ridges that might form a regular pattern. The ridges may extend substantially in a direction of fluid flow through the valve. The ridges may be substantially evenly spaced. Thus, the ridges may define spokes extending from a centre of the valve. Hence, the ridges may provide for robustness whilst allowing for the diffuser to be formed from less material to thereby reduce the weight of the diffuser and hence the valve. Also, providing ridges that extend substantially in the direction of fluid flow through the valve may provide for a reduction in resistance presented to fluid flowing through the valve.

Alternatively or in addition, parts of a valve that move in relation to each other and bear against each other may comprise a coating that is operative to provide for a lower coefficient of friction than un-coated surfaces of the parts. More specifically, the coating may comprise Teflon.

Alternatively or in addition, the water motion energy conversion apparatus may further comprise a support arrangement that is configured to engage with a bed of the body of water and to support the flap arrangement, the water motion energy conversion apparatus being configured such that the flap arrangement is movable in relation to the support arrangement between a first disposition in which the flap arrangement is close to the bed of the body of water and a second disposition in which the flap arrangement is spaced apart from the bed of the body of water. * a

Alternatively or in addition, the water motion energy conversion apparatus may further comprise a pressure line, a return line and a hydraulic motor in fluid communication with each of the pressure and return lines, fluid present in the pressure and return lines being operative, in use of the energy conversion apparatus, to drive the hydraulic motor, in which the * energy conversion apparatus is configured such that in use the pressure and return lines are located in a body of salt water and the fluid present in the pressure and return lines consists of at least one of: a non-polar fluid; and a fluid of substantially the same electro potential as the body of salt water.

Alternatively or in addition, the energy extraction apparatus may comprise electrical energy conversion apparatus comprising; a hydraulic motor driven by a hydraulic circuit; a flywheel driven by the hydraulic motor and operative to store energy from the hydraulic motor; and an induction generator mechanically coupled to the flywheel, in which the hydraulic motor and the induction generator are coupled to the flywheel by respective magnetic couplings that are operative to be selectively engaged to charge or discharge energy from the flywheel.

Alternatively or in addition, the flap arrangement and the energy extraction apparatus may be located proximate each other. The energy extraction apparatus may comprise electrical energy conversion apparatus.

Alternatively or in addition, the flap arrangement may comprise at least one hydrofoil disposed so as to engage with the body of water though which the flap arrangement moves when in use. The hydrofoil may be configured and disposed on the flap arrangement to impart a force on the flap arrangement that is either directed towards the surface of the body of *:*.* water or directed away from the surface of the body of water. Hence, the * at least one hydrofoil may be operative to increase the speed of :.: * 25 movement of the flap arrangement when at least one of rising and falling in the body of water.

More specifically, the flap arrangement may be configured to change an * angle of disposition of the hydrofoil in relation to the flap arrangement.

Hence1 the hydrofoil may be pivotably mounted on the flap arrangement.

The flap arrangement may comprise a mechanical arrangement, e.g. in the form of a motor driven linkage arrangement, that is operative to move the hydrofoil.

According to a second aspect of the present invention, there is provided a water motion conversion system comprising a plurality of water motion energy conversion apparatus according to the first aspect of the present invention, the plurality of water motion conversion apparatus being connected to each other.

Embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention.

The present inventors have appreciated that the feature of the at least one non return valve may be of wider application than hitherto described.

Therefore and according to a third aspect of the present invention, there is provided energy conversion apparatus comprising: a pressure line, a return line and a hydraulic motor in fluid communication with each of the pressure and return lines, water present in the pressure and return lines being operative, in use of the energy conversion apparatus, to drive the hydraulic motor, the energy conversion *:*.* apparatus further comprising at least one non return valve, which comprises a valve disc and a seat, in one of the pressure and return lines, in which the non return valve comprises first and second biasing device, the first biasing device being operative to hold the valve disc against the seat and the second biasing device becoming operative to bias the valve disc towards the seat when the valve is at least 50 percent open.

* In use, the combination of first and second biasing devices can provide a powerful valve closing force to thereby provide for closing of the valve just before a return flow of water in the pressure and return lines. Thus, the valve can provide for improved non-slam closure. This can be advantageous in energy conversion apparatus according to the present invention, in which water hammer is liable to occur when each opening and closing cycle of the valve starts and stops. The incompressibility of the water and a water pressure of up to about 60 bar contribute to the likelihood of water hammer arising. Furthermore the combination of first and second biasing devices can provide for a reduction in the time taken for the valve to close compared, for example, with valves that rely on a single biasing device. When the energy conversion apparatus is applied in water motion energy conversion apparatus, the non return valve tends to suffer from wear and tear on account of the typically arduous operating conditions under which a valve may undergo twenty-five million opening and closing cycles over a five year period.

Embodiments of the third aspect of the present invention may comprise one or more features of the first aspect or second aspect of the present invention.

The present inventors have appreciated that the feature of the support arrangement may be of wider application than hitherto described. Hence and according to a fourth aspect of the present invention, there is provided a water motion energy conversion apparatus comprising: water motion engaging apparatus that is configured such that, in * *.

:.: * 25 use, it is operative to engage with a body of water and to convert water movement to confined movement of a body; and electrical energy conversion apparatus that is operative to convert the confined movement of the body into electrical energy, * * the water motion engaging apparatus comprising a support arrangement that is configured to engage with a bed of the body of water and to support an operative part of the water motion engaging apparatus, the water motion engaging apparatus being configured such that the operative part is movable in relation to the support arrangement between a first disposition in which the operative part is close to the bed of the body of water and a second disposition in which the operative part is spaced apart from the bed of the body of water.

In use, the operative part is moved to the first disposition when it is desired to extract electrical energy from water motion and is moved to the second disposition when it is desired to gain more ready access to the operative part, e.g. for maintenance operations. For example, the second disposition may be such that the operative part is raised to the surface of the body of water or even raised above the surface to allow a surface vessel to pass underneath for maintenance or replacement of the operative part.

More specifically, the water motion engaging apparatus may be configured such that the operative part can move progressively away from and towards the bed of the body of water. Thus, where the water motion engaging apparatus is configured to engage with waves to extract energy therefrom, the operative part may move progressively with a rising and falling tide. Hence, the location of the operative part in the body of water may be changed to provide for improved engagement with the waves.

More specifically, the water motion engaging apparatus may further comprise a sensor arrangement that is operative to determine a location of the surface of the body of water. The water motion engaging apparatus may be further configured to move the operative part in relation to the * support arrangement in dependence on an output from the sensor arrangement. The water motion engaging apparatus may comprise at least one hydraulic jack that is operative to move the operative part in relation to the support arrangement in dependence on the sensor arrangement output.

Alternatively or in addition, the support arrangement may complise a plurality of spaced apart elongate support members, each support member having a bed engaging surface and being configured to movably engage with a different location on the operative part. The water motion engaging apparatus may be configured such that, in use, each support member extends from the bed of the body of water to at least a surface of the body of water. For example, the operative part may comprise a platform supporting a flap arrangement that moves in dependence on water movement and each of four support arrangements may be located at a different corner of the plafform.

Embodiments of the fourth aspect of the present invention may comprise one or more features of any previous aspect of the present invention.

According to a fifth aspect of the present invention, there is provided energy conversion apparatus comprising: a pressure line, a return line and a hydraulic motor in fluid communication with each of the pressure and return lines, fluid present in the pressure and return lines being operative, in use of the energy conversion apparatus, to drive the hydraulic motor, in which the energy conversion apparatus is configured such that in use the pressure and return lines are located in a body of salt water and the fluid present in the pressure and return lines consists of at least one of: a non-polar fluid; and a fluid of substantially the same electro potential as the body of salt water.

In use, the presence of at least one of a non-polar fluid and a fluid of substantially the same electro potential as the body of salt water in the pressure and return lines can avoid an electro potential difference between fluid in the pressure and return lines and fluid surrounding the pressure and return lines. Such an electro potential difference is liable to give rise to a battery effect which slowly corrodes susceptible metal components of the energy conversion apparatus. Known energy conversion apparatus uses fresh water in the pressure and return lines and the electro potential difference between the fresh water and the surrounding salt water causes corrosion.

More specifically, the fluid present in the pressure and return lines may comprise hydraulic oil. Use of hydraulic oil may allow the pressure and return lines to be operated at higher pressure, which thereby allows for smaller diameter pressure and return lines and associated components.

The hydraulic oil may comprise bio-degradable hydraulic oil. Hence, environmental damage in the event of a leak may be minimised.

Further embodiments of the fifth aspect of the present invention may comprise one or more features of any one of the previous aspects of the present invention. * * *

According to a sixth aspect of the present invention, there is provided electrical energy conversion apparatus configured for use with water motion energy conversion apparatus, the electrical energy conversion apparatus comprising: a hydraulic motor driven by a hydraulic circuit; a flywheel driven by the hydraulic motor and operative to store energy from the hydraulic motor; and an induction generator mechanically coupled to the flywheel, in which the hydraulic motor and the induction generator are coupled to the flywheel by respective magnetic couplings that are operative to be selectively engaged to charge or discharge energy from the flywheel.

In use, the flywheel can provide for a reduction in pulsing of the water motion energy conversion apparatus that arises from the rise and fall in fluid pressure in the hydraulic circuit by storing and releasing energy at the peaks and troughs of fluid pressure cycles. The magnetic couplings provide for effective engagement that can further reduce the pulsing of the water motion energy conversion apparatus.

More specifically, the flywheel may be mounted in an isolation chamber, e.g. a vacuum chamber, in which at least one magnetic coupling is operative through a wall of the chamber.

Further embodiments of the sixth aspect of the present invention may comprise one or more features of any one of the previous aspects of the present invention.

According to a seventh aspect of the present invention, there is provided a water motion energy conversion apparatus comprising: * * water motion engaging apparatus that is configured such that, in use, it is operative to engage with a body of water and to convert water movement to confined movement of a body; and electrical energy conversion apparatus that is operative to convert the confined movement of the body into electrical energy, in which the water motion engaging apparatus and the electrical energy conversion apparatus are located proximate each other.

Hence, the water movement is converted to confined movement of a body, e.g. fluid in a hydraulic circuit, and electricity is generated at the same location, e.g. in an off-shore wave or tidal energy generation installation.

Therefore, there is no need for a hydraulic circuit between a water motion engaging apparatus and an electrical energy conversion apparatus that are spaced apart from each other, e.g. where the electrical energy conversion apparatus is located on-shore. Instead, electricity generated by the electrical energy conversion apparatus may be conveyed, e.g. to an on-shore installation, by electricity cables. Replacement of a hydraulic circuit with electricity cables can be expected to afford a significant reduction in cost and to reduce maintenance requirements.

More specifically, the water motion engaging apparatus may comprise hydraulic rams that are operative to pump hydraulic oil and the water motion energy conversion apparatus may further comprise a hydraulic motor that is driven by the pumped hydraulic oil. The water motion energy conversion apparatus may further comprise an electricity generator, e.g. an 1P68 generator, which is driven by the hydraulic motor.

Further embodiments of the seventh aspect of the present invention may comprise one or more features of any one of the previous aspects of the present invention.

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Brief description of drawins * S. S. S

*.. . 25 Further features and advantages of the present invention will become apparent from the following specific description, which is given by way of example only and with reference to the accompanying drawings, in which: * Figure 1 is a representation of wave motion energy conversion apparatus according to the present invention; Figures 2A and 28 provide detailed representations of the flap arrangement of Figure 1; Figure 2C provides a detailed representation of an alternative embodiment of the flap arrangement of Figure 1; Figure 3 is a representation of a non-return valve used in the apparatus of Figure 1; Figure 4 is a representation of a flywheel used in the apparatus of Figure 1; and Figure 5 illustrates a further embodiment of the wave motion energy conversion apparatus shown in Figure 1.

Figure 1 shows wave motion energy conversion apparatus 10. The apparatus 10 comprises wave motion engaging apparatus 12 that, in use, is submerged in a body of water, such as in sea water at an off-shore location. The wave motion engaging apparatus 12 comprises a base portion 14, which rests on the bed of the body of water, such as on the sea bed, and a flap arrangement 16, which is pivotally connected to the base portion 14, such that the flap arrangement is capable of moving in a to and fro manner between a first disposition in which the flap arrangement extends away from the base portion towards the surface of the body of water and a second disposition in which the distal portion of the flap * 1 arrangement is closer to the bed of the body of water. The flap arrangement is driven from the first disposition by wave motion acting on * ** the upper end of the flap arrangement. First 18 and second hydraulic *** 25 rams 20 are mechanically coupled to the base portion 14 and the flap arrangement 16 such that the to and fro movement of the flap :. arrangement compresses the first hydraulic ram 18 and extends the second hydraulic ram 20 during a first half of a to and fro cycle and compresses the second hydraulic ram 20 and extends the first hydraulic ram 18 during a second half of the to and fro cycle. The hydraulic rams are either single or double acting. In an alternative (un-illustrated) configuration, both the first and second hydraulic rams are located on a same side of the flap arrangement, i.e. either on the same side as the first hydraulic ram of Figure 1 or on the same side as the second hydraulic ram of Figure 1. Again, the hydraulic rams are either single or double acting.

Actuation of the first and second hydraulic rams 18, 20 drives a hydraulic circuit comprising a pressure line 22 and a return line 24, which contain biodegradable hydraulic oil. The hydraulic circuit extends from the wave motion engaging apparatus 12 to an on-shore location where a hydraulic motor 26 is installed along with the remaining component parts of the wave motion energy conversion apparatus. The hydraulic motor 26 is driven by the rise and fall in pressure of the hydraulic oil in the hydraulic circuit. A first non-return valve 28 is located in the pressure line 22 and a second non-return valve 30 is located in the return line 24. Each of the first and second non-return valves 28, 30 is operative to prevent reversal of flow of hydraulic fluid that would otherwise occur as a consequence of the to and fro movement of the flap arrangement 16. Mechanical energy from the hydraulic motor 26 is stored in a flywheel arrangement 32 with energy being coupled from the flywheel arrangement to an induction generator 34 via a gearbox 36. Electrical energy from the induction generator 34 is then operated upon by an inverter and a line rectifier 38 to produce an electrical output suitable for connection to an electrical grid (not shown). In accordance with known practice, several wave motion * ** engaging apparatus 12 may be coupled together such that they share a S.: * 25 common hydraulic circuit that extends from the offshore location to the onshore location. *. * . * **.

A side view of the flap arrangement 16 when in a first disposition is shown in Figure 2A and a side view of the flap arrangement 16 when in a second disposition is shown in Figure 2B. Components in common in Figures 2A and 2B are indicated by common reference numerals. The flap arrangement comprises a support frame 50 of generally rectangular footprint when viewed from the front or the rear (i.e. at ninety degrees to the views shown in Figures 2A and 2B). The flap arrangement also comprises three buoyancy chambers 52 attached between two upwardly extending and spaced apart members of the support frame 50. Each buoyancy chamber 52 is of cylindrical form and defines a sealed, air filled chamber. The three buoyancy chambers 52 are spaced apart from each other on the support frame 50. In use, the positive buoyancy of the buoyancy chambers 52 biases the flap arrangement 16 such that it extends towards the surface of the body of water in which the flap arrangement is located, i.e. towards the first disposition shown in Figure 2A. The flap arrangement 16 further comprises three flap portions 54 attached in the same fashion as the buoyancy chambers 52 between the two upwardly extending and spaced apart members of the support frame 50. Each flap portion 54 is of comma shaped cross section. Also, each flap portion 54 defines a sealed, air filled chamber; hence each flap portion 54 contributes to the positive buoyancy of the flap arrangement.

Furthermore each flap portion 54 is rotatably mounted on the support frame 50 with the axis of rotation present at the centre of the circular portion of the comma shaped cross section shape of the flap portion.

Hence, rotation of each flap portion moves the distal end of the flap portion towards or away from the support frame depending on the direction of * *. rotation. Rotation of the flap portions in a first direction moves the distal end of each flap portion such that it is proximate the upper end of the neighbouring buoyancy chamber 52 such that the flap arrangement is in the first disposition shown in Figure 2A. Rotation of the flap portions in a second, opposite direction moves the distal end of each flap portion such that it is oriented away from the support frame and spaced apart from the upper end of the neighbouring buoyancy chamber 52 such that the flap arrangement is in the second disposition shown in Figure 2B. As can be appreciated from Figures 2A and 2B, the flap arrangement presents a larger surface area in a direction orthogonal to the side views shown in Figures 2A and 2B in the first disposition than in the second disposition.

Hence, the flap arrangement presents a large surface area to waves in the body of water in which the flap arrangement is located when being driven by wave action from the first disposition to the second disposition and a smaller surface area and hence resistance when being returned by the positive buoyancy from the second disposition to the upright first disposition.

Referring to Figure 2A, the flap arrangement comprises a first flap setting arrangement 56, which is operative to move the flap portions 54 from the second disposition to the first disposition. More specifically, the first flap setting arrangement 56 comprises a first setting member 58 that extends from the lowest flap portion towards the base portion 60 and is attached to a location on the circular portion of the flap portion on the side of the axis of rotation opposing the tail shaped portion of the flap portion. The flap setting arrangement 56 also comprises a first mechanical linkage 62 that connects like locations on the other two flap portions to the location on the lowest flap portion at which the first setting member is attached. As the flap arrangement 16 rises on account of the positive buoyancy towards the upright position the distal end of the first setting member 58 bears against * ** a first protrusion 64 extending upwards from the base portion 60 such that the first setting member is pushed upwards to rotate the flap portion such that distal end of the flap portion is forced downwards. Likewise upward : * movement of the first mechanical linkage 62 rotates the other two flap :**:; portions such that their distal ends are forced downwards. Referring now to Figure 2B, the flap arrangement comprises a second flap setting arrangement 66, which is operative to move the flap portions 54 from the first disposition to the second disposition. More specifically, the second flap setting arrangement 66 comprises a second setting member 68 that extends from the lowest flap portion towards the base portion 60 and is attached to a location on the circular portion of the flap portion on the same side of the axis of rotation as the tail shaped portion of the flap portion. The second flap setting arrangement 66 also comprises a second mechanical linkage 70 that connects like locations on the other two flap portions to the location on the lowest flap portion at which the second setting member is attached. As the flap arrangement 16 is driven downwards by wave action the distal end of the second setting member 68 bears against a second protrusion 72 extending upwards from the base portion 60 such that the second setting member is pushed upwards to rotate the flap portion such that distal end of the flap portion is forced upwards. Likewise upward movement of the second mechanical linkage 70 rotates the other two flap portions such that their distal ends are forced upwards. Although not shown in Figures 2A and 2B, the flap arrangement 16 also comprises first and second hydrofoils attached to and extending from the side of the support frame 50. Each hydrofoil is pivotally attached to the support frame with pivotal movement of the hydrofoil being motor driven to set the angle of the hydrofoil to achieve improved speed of movement of the flap arrangement as it moves to and fro in the water.

A detailed representation of an alternative embodiment of the flap arrangement shown in Figures 2A and 2B is provided in Figure 2G. The flap arrangement of Figure 2C has the same form and function as the flap arrangement of Figures 2A and 2B except as described as follows.

Hence, components common to the embodiment of Figures 2A and 2B *:*. and the embodiment of Figure 2C are designated with common reference numerals and the reader's attention is directed to the foregoing description for details of their form and function. As can be seen from Figure 2C, the flap arrangement comprises six flap portions 54 instead of the three flap portions of the arrangement of Figures 2A and 2B and lacks the buoyancy chambers 52. Each of the six flap portions 54 of Figure 2C defines an air filled space that provides the positive buoyancy required to return the flap arrangement to the upright disposition. Also, the flap arrangement of Figure 2C comprises hydraulic rams 76 that are operative to move the flap portions between the raised and lowered positions during the two different parts of the operating cycle. Although the flap arrangement of Figure 2C shows a hydraulic ram driving each flap portion, the mechanical linkage arrangement of Figures 2A and 2B may be combined with the arrangement of Figure 2C. More specifically, a single hydraulic ram is employed instead of the first and second setting members 58, 68 and the first and second protrusions 64, 72 of the arrangement of Figures 2A and 2B and one of the first and second flap setting arrangements 56, 66 is retained to couple the hydraulically actuated movement to all the flap portions. The valve body is configured for connection of its ports with Graylock or SMX connectors.

A detailed representation of the non-return valve of the apparatus of Figure 1 is shown in Figure 3. The non-return valve 80 of Figure 3 comprises a valve body 82, a valve seat 84 and a valve disc 86. The valve disc 86 is attached to a valve shaft 88, which defines a blind bore that extends from the distal end of the valve shaft. The valve shaft 88 is * ** slidably received in a shaft guide 90, which forms part of the valve body.

Linear bearings 92 provide for ease of movement of the valve shaft 88 in the shaft guide 90. A spring guide 94 comprises a main body with an elongate spring guide member 96 extending therefrom. A first coil spring 98 is received over the elongate spring guide member 96. The main body of the spring guide 94 is slidably received in a blind bore defined by the valve body. The blind bore defined by the valve shaft 88, slidably receives the elongate spring guide member 96 such that the first coil spring 98 bears between the end of the blind bore of the valve shaft 88 and the base of spring guide member defined by the main body of the spring guide. The main body of the spring guide defines a blind bore extending in an opposite direction to the elongate spring guide member 96 from the end of the blind bore towards the end of the blind bore defined by the valve body.

A second coil spring 100 is received in the blind bore defined by the main body of the spring guide such that the second coil spring bears between the end of the blind bore defined by the main body and the end of the blind bore defined by the valve body. The second coil spring 100 has a spring constant substantially five times the spring constant of the first coil spring 98. The first coil spring 98 is operative to bias the valve disc 86 against the valve seat 84. When the hydraulic circuit of the wave motion energy conversion apparatus 10 of Figure 1 is pressurised upon operation of the flap arrangement, the increased pressure of the hydraulic fluid in the hydraulic circuit forces the valve disc away from the valve seat against the bias of the first coil spring. As the valve disc 86 is forced progressively further away from the valve seat 84, the valve shaft 88 travels in the shaft guide 90 until the distal end of the valve shaft bears against the shoulder defined between the main body and the spring guide member of the spring guide 94. The distal end of the valve shaft bears against the shoulder * when the valve is substantially 85 percent open. When the valve shaft ****** . . . * * bears against the shoulder, the spring guide is forced into the bore defined by the valve body against the bias of the second coil spring 100. The force required to act against the bias of the second coil spring 100 is provided by the Venturi effect which is operative when the valve is at least substantially 85 percent open. The design of the shape of the valve *:*. opening to provide for such a Venturi effect is within the ordinary design skill of the person of ordinary skill in the art. When the pressure in the hydraulic circuit falls, the combined action of the first and second coil springs 98, 100 provides for rapid and secure closing of the valve, to thereby reduce the effect of water hammer. The surface of the first and second coil springs 98, 100 and the surfaces of the valve against which they bear are coated with Teflon to thereby reduce the coefficient of friction. The operative parts of the valve are attached to and supported by a diffuser 102 that is slidably received in the valve body 82 to thereby provide for ease of manufacture of the operative parts prior to their being located in and attached to the valve body. The diffuser 102 defines a plurality of evenly spaced ridges that extend in the direction of fluid flow through the valve. Hence, the ridges define spokes extending away from the centre of the valve.

A representation of flywheel apparatus used in the apparatus of Figure 1 is shown in Figure 4. The flywheel apparatus 120 comprises a flywheel 122 that is operative to rotate on a first axle 124. First 126 and second 128 discs are attached to the first axle 124 such that they rotate with the flywheel 122. The flywheel 122, first axle 124 and first and second discs 126, 128 are held within an enclosure 130 that defines a vacuum. A third disc is mounted for rotation on a second axle 134 such that the third disc 132 is coaxially disposed in relation to the first disc 126. Permanent magnets 140 of opposing polarity are mounted on opposing faces of the * first and third discs, whereby the first and third discs rotate with each other by virtue of the magnetic forces acting between the first and third disc through the enclosure 130. A linear actuator 136, such as a hydraulic piston, is operative to move the second axle 134 and third disc 132 towards a splined coupling 138 so as to bring about engagement of the second axle 134 with an input shaft to the flywheel arrangement (i.e. a *:*. shaft from the hydraulic motor 26 of Figure 1). A fourth disc 142 is mounted for rotation on a third axle 144 such that the fourth disc is coaxially disposed in relation to the second disc 128. Permanent magnets 146 of opposing polarity are mounted on opposing faces of the second and fourth discs, whereby the second and fourth discs rotate with each other by virtue of the magnetic forces acting between the second and fourth discs through the enclosure 130. A further linear actuator 148, such as a hydraulic piston, is operative to move the third axle 144 and fourth disc 142 towards a further splined coupling 150 so as to bring about engagement of the third axle 144 with an output shaft from the flywheel arrangement (i.e. a shaft to the gearbox 36 of Figure 1). The two linear actuators 136, 148 are controlled, e.g. by computer, to engage and disengage and thereby provide for selective coupling of energy to the flywheel 122 and selective coupling of energy from the flywheel. The flywheel arrangement may be of the kind described in WO 2008/1 25860.

An alternative embodiment of wave motion energy conversion apparatus is shown in Figure 5. The wave motion energy conversion apparatus 170 comprises the wave motion engaging apparatus 12 of Figure 1 and the part 172 of the hydraulic circuit of Figure 1 that is located at the wave motion engaging apparatus 12. The wave motion engaging apparatus 12 and its associated hydraulic circuit are located on a square platform 174, which is movably supported by four legs 176 that are disposed at different corners of the square plafform. Each leg 176 has a seabed engaging end * : and extends up from the seabed such that its opposite end extends S..... . . . . * * beyond the water surface even at high tide. A hydraulic jack 180 is provided on each leg 176. Each hydraulic jack is operative to move its respective corner of the platform 174 in relation to its leg 176. Hence, when the four hydraulic jacks are operated together the platform moves up or down the legs. A sensor 178 is provided at the top of one of the legs 176. The sensor 178 is operative to determine a distance between the top of the leg and the surface 182 of the body of water in which the wave motion energy conversion apparatus 170 is situated. An optical reflectance sensor, laser Doppler distance sensor or the like is employed.

Alternatively, a pressure sensor is provided at the foot of one of the legs to sense a depth of water at the leg. The sensor 178 is operative to determine the height of the tide and the hydraulic jacks are operative in dependence on the sensor output to raise or lower the platform 174 such that the top of the wave motion engaging apparatus 12 is at or near the water surface so as to provide for optimal engagement with waves at or near the surface.

In another (un-illustrated) embodiment, all the components shown in Figure 1 are located at the offshore location. Hence, the entire hydraulic circuit, the hydraulic to electricity conversion apparatus and the electricity regulation apparatus are located with the wave motion engaging apparatus 12. * S *

S..... * * * S. * * . S. * S * .*.

S * * .*

Claims

CLAIMS: 1. Water motion energy conversion apparatus comprising: a base portion configured to be anchored to the bed of a body of water; a flap arrangement pivotally connected to the base portion and configured to, in use, oscillate to and fro about its pivotal connection in dependence on water motion acting on a face of the flap arrangement; and energy extraction apparatus operative to extract energy from movement of the flap arrangement, in which the flap arrangement comprises a support portion and at least a first flap portion, the first flap portion being movable in relation to the support portion between a first disposition when the flap arrangement is being driven towards the bed of the body of water by water motion and a second disposition when the flap arrangement is rising from the bed of the body of water, a surface area is of a face of the flap arrangement that is acted upon by the water motion being larger in the first disposition than in the second disposition.
2. Apparatus according to claim 1, in which the flap arrangement is biased to the vertical when in use.
3. Apparatus according to claim 2, in which the flap arrangement is configured to be positively buoyant in water to thereby provide for biasing of the flap arrangement to the vertical.
4. Apparatus according to any preceding claim, in which respective surface areas of opposing faces of the flap arrangement that are acted upon by water motion are smaller in the first disposition than in the second disposition.
5. Apparatus according to any preceding claim, in which the flap arrangement comprises a plurality of flap portions, each of the flap portions being movable in relation to the support portion between the first and second dispositions.
6. Apparatus according to claim 5, in which the water motion energy conversion apparatus is configured such that the plurality of flap portions all move together between the first and second dispositions.
7. Apparatus according to claim 5 or 6, in which the flap arrangement comprises at least one buoyancy portion, the buoyancy portion being disposed between neighbouring flap portions.
8. Apparatus according to any preceding claim, in which the first flap portion comprises an elongate member that extends longitudinally in a direction generally perpendicular to a direction of water motion that drives the flap arrangement when in the first disposition.
9. Apparatus according to any preceding claim, in which the first flap is portion is pivotally mounted on the support portion.
10. Apparatus according to any preceding claim, in which the first flap portion defines first and second opposing surfaces, the first surface being acted upon by water motion during movement of the flap arrangement towards the bed of the body of water, the first surface defines a convex surface and the second surface defines a convex surface.
11. Apparatus according to any preceding claim further comprising a flap setting arrangement which is operative to move the flap portion to the second disposition.
12. Apparatus according to claim 11, in which the flap setting arrangement comprises a first protrusion on the base portion and a first mechanical linkage arrangement on the flap arrangement, the first protrusion and the first mechanical linkage arrangement being disposed on the water motion energy conversion apparatus such that the first protrusion bears against a part of the first mechanical linkage arrangement to thereby move the first mechanical linkage arrangement, which in turn moves the flap portion to the second disposition.
13. Apparatus according to claim 12, in which the flap setting arrangement comprises a second protrusion on the base portion and a second mechanical linkage arrangement on the flap arrangement, the second protrusion and the second mechanical linkage arrangement being disposed on the water motion energy conversion apparatus such that the second protrusion bears against a part of the second mechanical linkage arrangement to thereby move the second mechanical linkage arrangement, which in turn moves the flap portion to the first disposition.
14. Apparatus according to any preceding claim configured such that, in use, the base portion and the flap arrangement extend vertically through at least the is entire depth of the body of water.
15. Apparatus according to any preceding claim, in which the energy extraction apparatus comprises: a hydraulic motor driven by hydraulic fluid, the hydraulic fluid being driven by movement of the flap arrangement; a flywheel energy store mechanically coupled to the hydraulic motor; and an electrical generator driven by the flywheel.
16. Apparatus according to claim 15 further comprising a pressure line, a return line and a hydraulic motor in fluid communication with each of the pressure and return lines, water present in the pressure and return lines being operative, in use of the apparatus, to drive the hydraulic motor, the water motion energy conversion apparatus further comprising at least one non return valve, which comprises a valve disc and seat in one of the pressure and return lines, in which the non return valve comprises first and second biasing devices, the first biasing device being operative to hold the valve disc against the seat and the second biasing device becoming operative to bias the valve disc towards the seat when the valve is at least 50 per cent open.
17. Apparatus according to claim 16, in which the second biasing device has a spring constant at least twice as great as a spring constant of the first biasing device.
18. Apparatus according to claim 16 or 17, in which a first non return valve is disposed in the pressure line and a second non return valve is disposed in the return line.
19. Apparatus according to any one of claims 16 to 18, in which the non io return valve comprises a valve shaft attached to the valve disc, the valve shaft being configured such that only the first biasing device of the first and second biasing devices exerts a bias on the valve shaft when the valve is no more than per cent open and such that the first and second biasing devices both exert a bias on the valve shaft when the valve is at least 50 per cent open. is
20. Apparatus according to any one of claims 16 to 19, in which the non return valve defines an aperture portion, which in use receives a flow of fluid from the pressure or return line, the aperture portion defining an aperture surface extending towards the valve seat, the aperture surface having a profile that is operative to provide for a Venturi effect when the valve is at least 50 per cent open.
21. Apparatus according to any one of claims 16 to 20, in which the non return valve comprises a diffuser that defines an outwardly facing surface of uneven profile.
22. Apparatus according to claim 21, in which the uneven profile is defined by a plurality of substantially evenly spaced apart ridges which extend substantially in a direction of fluid flow through the valve.
23. Apparatus according to any one of claims 16 to 22, in which parts of the non return valve that move in relation to each other and bear against each other comprise a coating which is operative to provide for a lower coefficient of friction than un-coated surfaces of the parts.
24. Apparatus according to any preceding claim further comprising a support arrangement which is configured to engage with a bed of the body of water and to support the flap arrangement, the water motion energy conversion apparatus being configured such that the flap arrangement is movable in relation to the support arrangement between a first disposition in which the flap arrangement is close to the bed of the body of water and a second disposition in which the io flap arrangement is spaced apart from the bed of the body of water.
25. Apparatus according to any preceding claim further comprising a pressure line, a return line and a hydraulic motor in fluid communication with each of the pressure and return lines, fluid present in the pressure and return is lines being operative, in use, to drive the hydraulic motor, in which the water motion energy conversion apparatus is configured such that in use the pressure and return lines are located in a body of salt water and the fluid present in the pressure and return lines consists of at least one of: a non-polar fluid; and a fluid of substantially the same electro potential as the body of salt water.
26. Apparatus according to any preceding claim, in which the energy extraction apparatus comprises electrical energy conversion apparatus comprising: a hydraulic motor driven by a hydraulic circuit; a flywheel driven by the hydraulic motor and operative to store energy from the hydraulic motor; and an induction generator mechanically coupled to the flywheel, in which the hydraulic motor and the induction generator are coupled to the flywheel by respective magnetic couplings that are operative to be selectively engaged to charge or discharge energy from the flywheel.
27. Apparatus according to any preceding claim, in which the flap arrangement and the energy extraction apparatus are located proximate each other.
28. Apparatus according to any preceding claim, in which the flap arrangement comprises at least one hydrofoil disposed so as to engage with the body of water through which the flap arrangement moves when in use.
29. Apparatus according to claim 28, in which the hydrofoil is configured and disposed on the flap arrangement to impart a force on the flap arrangement that is either directed towards the surface of the body of water or directed away from the surface of the body of water.io
30. Apparatus according to claim 28 or 29, in which the flap arrangement is configured to change an angle of disposition of the hydrofoil in relation to the flap arrangement.
31. Apparatus according to claim 30, in which the flap arrangement is comprises a mechanical arrangement that is operative to move the hydrofoil.
32. A water motion energy conversion system comprising a plurality of water motion energy conversion apparatus according to any one of the preceding claims, the plurality of water motion conversion apparatus being connected to each other to thereby pool the energy generated by each water motion energy conversion apparatus.