Wave Energy Converter

FIELD OF THE INVENTION

This invention relates to apparatus for converting wave energy in a body of water into a form which can perform useful work.

The invention has been devised particularly, although not necessarily solely, for harnessing wave energy and converting the harnessed energy to pressurised fluid for use in any appropriate way. The fluid may comprise water drawn from the body of water itself. Where the body of water comprises an ocean, seawater drawn from the ocean may be piped under high-pressure to shore and fed to a reverse osmosis desalination unit to yield fresh water. The salt water concentrate exiting the desalination unit, which is still at high-pressure, may be fed to a turbine and the shaft power used to generate electricity.

BACKGROUND ART

There have been many proposals for devices that seek to harness ocean wave energy but only a few of such devices are actually under sustained commercial development. All of the commercial devices, whether shore based, ashore or offshore, have their energy conversion to electricity with the necessary equipment located in situ. This means the critical components such as turbines, alternator/generators and electrical distribution infrastructure must be able to withstand the marine environment including such factors as: the force of storms, prolonged exposure to seawater, and accidental immersion in seawater. In the case of offshore devices, there is also the need for extensive undersea power cabling to bring electricity to shore. The net result is increased capital cost and decreased reliability.

With a view to addressing the problems and deficiencies associated with the proposals referred to above, the applicant had previously proposed a wave energy converter the subject of International Application PCT/AU03/00813. One aspect of the applicant's previous proposal was directed to apparatus for capturing wave energy in a body of water such as the sea. The apparatus rests on the seabed and comprises a body structure having a diaphragm adapted to deflect in response to wave action. A reciprocating pump is connected to the diaphragm, with a pumping chamber of the pump undergoing volume expansion and contraction in response to deflection of the diaphragm. The pumping chamber has an inlet communicating with the seawater and an outlet, whereby seawater is drawn into the pumping chamber upon volume expansion thereof and is discharged upon volume reduction thereof through the outlet. The reciprocating pump is connected directly to the diaphragm, so that the stroke length of the pump corresponds to the amplitude of displacement of the diaphragm at the point at which it is connected to the pump. This can require the reciprocating pump to have a relatively long stroke in order to accommodate the amplitude of displacement of the diaphragm. However, a pump with a relatively long stroke is not particularly conducive to compact design which may possibly be a requirement in certain applications.

It is against this background that the present invention has been developed.

The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge in Australia as at the priority date of the application.

DISCLOSURE OF THE INVENTION

According to one aspect of the invention there is provided apparatus for capturing wave energy in a body of water, the apparatus comprising a body structure having a portion thereof adapted to deflect in response to wave action, a reciprocating pump defining a pumping chamber adapted to undergo expansion and contraction in response to deflection of said portion of the body structure, the pumping chamber having an inlet communicating with a fluid source and an outlet, whereby fluid from the fluid source is drawn into the pumping chamber upon volume expansion thereof and is discharged from the pumping chamber upon volume reduction thereof through the outlet, the pump being operably connected to said portion by a mechanism providing a velocity ratio of less than 1.0.

With this arrangement, the stroke length of the pump is less than the amplitude of displacement of said portion undergoing movement in response to wave action.

Preferably, the mechanism comprises a lever, with the pump being operably connected to the lever at a location closer to the fulcrum of the lever than the location at which said portion is connected to the lever.

The lever increases the force acting on the pump by a given ratio and reduces the stroke by the same ratio so that the net work transferred to the pump is substantially unchanged (if mechanical losses are low).

One reason for utilising the lever mechanism and hence a shorter pump stroke is that the overall height of the apparatus can be reduced, thus lowering overall cost. A further reason is that a shorter stroke length may be advantageous in terms of pump design, particularly in relation to sealing issues, where high-pressure fluids are involved.

In one arrangement, the lever mechanism may comprise a single lever operably connected to one or more pumps. There may, for example, be two pumps disposed one to each side of the lever fulcrum, whereby the pumps operate in opposition (in the sense that the pumping chamber of one pump undergoes volume expansion while the pumping chamber of the other pump undergoes volume reduction, and vice versa). Where there are a plurality of pumps, there can be more than one pump disclosed to either side of the fulcrum.

In another arrangement, there may be a plurality of lever mechanisms operably connected to said portion, with each lever mechanism operating one or more pumps. One such arrangement may involve three levers arranged in somewhat of a delta formation, with each lever being operably connected to said portion. Where there are a plurality of pumps, an accumulator may be incorporated in a common fluid line along which discharged fluid is pumped, for the purpose of achieving a more steady fluid flow.

Pumps acting in opposition may serve to provide hydraulic resistance to movement of the diaphragm in both directions, thereby dampening fluctuations in such movement.

The or each lever may be of framed construction, which provides both vertical and lateral rigidity under load.

The portion of the body structure adapted to deflect in response to wave action may comprise a diaphragm exposed to a body of water incorporating wave action. The diaphragm may comprise a substantially rigid portion and a flexible portion. Preferably, the flexible portion surrounds the rigid portion. Typically, the lever mechanism is operably connected to the rigid portion.

The body structure may include a working chamber which is disposed below the diaphragm and which is adapted to contain a compressible fluid such as air. The or each lever may be accommodated in, or at least extend into, the working chamber for connection to the diaphragm.

The or each working chamber may have a cylindrical chamber wall, with the outer periphery of the diaphragm being sealingly connected thereto.

The lever or levers may be pivotally supported on the base of the body structure, the peripheral wall of the working chamber, or on a support structure accommodated within the body structure.

The or each lever may be guided as it undergoes reciprocating movement in response to movement of the diaphragm under the influence of wave action. Each lever may be guided by a guide mechanism comprising a guide structure moveable along a guide. The guide may be provided on the inner surface of the chamber wall. Indeed, the inner surface of the chamber wall may itself provide the guide. The guide structure may comprise one or more rollers in rolling engagement with the chamber wall surface which provides the guide.

The or each lever may be provided with a counter-weight. The counter-weight may be set to provide some assistance for the return stroke of the diaphragm following completion of a power stroke thereof in response to wave action.

The body structure may further include a ballast chamber for accommodating ballast material such as sand. Typically, the ballast material is saturated with water. The ballast chamber may surround the working chamber.

The body structure may include a plurality of working chambers surrounded by the ballast chamber.

Ballast material such as saturated sand may be utilised as a filtering medium for the water being pumped.

Typically, the fluid being pumped comprises water drawn from the body of water from which wave energy is to be captured.

There may be provision to selectively flood each working chamber with seawater in circumstances where it is necessary to bring operation to a rapid cessation, for example in an overload situation in extremely heavy sea conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which:

FIG. 1 is a schematic sectional perspective view of an apparatus for capturing wave energy according to a first embodiment;

FIG. 2 is a schematic sectional side view of the first embodiment;

FIG. 3 is a fragmentary side view of the first embodiment;

FIG. 4 is a schematic sectional perspective view of an apparatus for capturing wave energy according to a second embodiment;

FIG. 5 is a schematic sectional side view of the second embodiment;

FIG. 6 is a schematic perspective view of an apparatus for capturing wave energy according to a third embodiment;

FIG. 7 is a schematic plan view of the third embodiment;

FIG. 8 is a schematic sectional view of the third embodiment;

FIG. 9 is a fragmentary sectional side view of the third embodiment;

FIG. 10 is a schematic plan view of apparatus for capturing wave energy according to a fourth embodiment;

FIG. 11 is a schematic side view of the fourth embodiment;

FIG. 12 is a schematic perspective view of a support structure forming part of the fourth embodiment;

FIG. 13 is a schematic side view of the support structure illustrated in FIG. 12;

FIG. 14 is a perspective view of part of the support structure illustrated in FIG. 12;

FIG. 15 is a plan view of FIG. 14;

FIG. 16 is a schematic side elevational view of a pump and lever mechanism utilised in the apparatus according to the fourth embodiment;

FIG. 17 is a further side view of the pump and lever mechanism illustrated in FIG. 16;

FIG. 18 is a schematic plan view of the fourth embodiment, illustrating in particular a seawater pumping circuit incorporated therein;

FIG. 19 is a side view of FIG. 18;

FIG. 20 is a fragmentary perspective view of the seawater pumping circuit, illustrating in particular a filtration system for intake seawater;

FIG. 21 is a schematic plan view of the filtration system;

FIG. 22 is a schematic plan view of a removable component of the filtration system;

FIG. 23 is a fragmentary elevational view of the fourth embodiment, illustrating in particular the deflectable diaphragm;

FIG. 24 is a view illustrating the diaphragm in three possible operating positions;

FIG. 25 is a fragmentary side elevational view illustrating in particular the connection between the flexible and rigid portions of the diaphragm;

FIG. 26 is a schematic side view illustrating the connection between the flexible diaphragm and the surrounding structure of the apparatus;

FIG. 27 is a fragmentary perspective view illustrating another form of construction of the flexible diaphragm;

FIG. 28 is a fragmentary plan view of apparatus according to a fifth embodiment;

FIG. 29 is a schematic plan view of apparatus according to a sixth embodiment;

FIG. 30 is a schematic plan view of apparatus for capturing wave energy according to a seventh embodiment;

FIG. 31 is a schematic side elevational view of apparatus for capturing wave energy according to an eighth embodiment;

FIG. 32 is a schematic perspective view of apparatus for capturing wave energy according to a ninth embodiment;

FIG. 33 is a schematic side elevational view of the apparatus of FIG. 32;

FIG. 34 is a schematic end elevational view of the apparatus of FIG. 32;

FIG. 35 is a schematic plan view of the apparatus of FIG. 32;

FIG. 36 is a schematic side view of the apparatus of FIG. 32, illustrating in particular the deflectable diaphragm and the lever mechanism to which it is connected, with the diaphragm being shown in an uppermost condition;

FIG. 37 is a view similar to FIG. 36, with the exception that the diaphragm is shown in a mid condition;

FIG. 38 is also a view similar to FIG. 36, with the exception that the diaphragm is shown in a lower condition;

FIG. 39 is a schematic plan view showing the relationship between two cells which cooperate to provide a working chamber, and a lever mechanism incorporated therein;

FIG. 40 is a schematic side elevational view illustrating the lever mechanism;

FIG. 41 is a plan view of a pumping circuit incorporated in the apparatus of FIG. 32;

FIG. 42 is a side elevational view of the pumping circuit;

FIG. 43 is a schematic view showing the intake end of the pumping circuit;

FIG. 44 is a fragmentary elevational view of the apparatus of FIG. 32, illustrating in particular the outlet end of the pumping circuit and also matting for mitigating scouring of the seabed on which the apparatus is installed;

FIG. 45 is a schematic perspective view of apparatus for capturing wave energy according to a tenth embodiment;

FIG. 46 is a plan view of the apparatus of FIG. 45; and

FIG. 47 is a schematic perspective view of a wave energy conversion system utilising an array of apparatus for capturing wave energy.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

The embodiments shown in the drawings are each directed to an apparatus for harnessing ocean wave energy and for converting the harnessed energy to high-pressure seawater, typically to about 6.89 Mpa (1000 psi). The apparatus is designed to rest on the seabed in relatively shallow waters and create minimal environmental impact. High-pressure seawater generated by the apparatus can be piped to shore for use in any appropriate purpose. In one application, the high-pressure seawater may be used as a motive fluid to drive a turbine, with the shaft power therefrom being used to generate electricity. In another application, the high-pressure seawater may be fed to a reverse osmosis desalination unit from which fresh water can be generated. The saltwater concentrate from the desalination unit, which is still at high-pressure, may then be fed to a turbine for extraction of mechanical energy. The spent saltwater concentrate can then be returned to the ocean, if desired.

Referring to FIGS. 1, 2 and 3, there is shown apparatus 10 according to a first embodiment. The apparatus 10 comprises a body structure 11 comprising a base 13 which rests on the seabed, and two walls 15, 17 upstanding from the base. Typically, the base 13 and the two upstanding walls 15, 17 are of integral construction and formed of concrete. Wall 15 is of generally cylindrical construction and provides an outer peripheral wall for the body structure. Wall 17 is also of generally cylindrical construction and is spaced inwardly of wall 15 to provide an inner wall within the body structure.

The spacing between the outer and inner walls 15, 17 defines a ballast chamber 21 for receiving ballast material. Typically, the ballast material comprises saturated sand taken from the seabed. In this embodiment, the upper end of the ballast chamber 21 is open to receive the ballast material. A closure (not shown) may be provided for closing the ballast chamber 21 if desired.

The inner cylindrical wall 17 surrounds an interior space 23, the top end of which is closed by a diaphragm 25. With this arrangement, the base 13, the cylindrical inner wall 17 and the diaphragm 25 cooperate to form a cell 26 having a working chamber 27.

The diaphragm 25 is exposed to seawater above the cell 26 and is deflectable in response to wave activity therein.

The diaphragm 25 comprises a rigid central portion 28 and a flexible outer portion 29 surrounding the central portion 28. The rigid central portion 28 comprises a reinforced circular plate and the outer portion 29 is membrane formed of an elastomeric material such as rubber. The elastomeric material may be reinforced with laminating materials to enhance strength and tear resistance. The outer periphery of the diaphragm 25 is sealingly connected at 31 to the upper end of the inner cylindrical inner wall 17.

The working chamber 27 is disposed immediately below the diaphragm 25 and contains a compressible fluid, which conveniently is air in this embodiment. The compressible fluid is under pressure to provide a lifting force to counterbalance the weight of the diaphragm 25 and any attachments thereto, as well as the seawater above the diaphragm. The fluid pressure within the working chamber 27 may be adjusted so as to maintain the diaphragm 25 at a predetermined position in calm sea conditions.

The apparatus 10 further includes a pumping circuit 41 having an intake (not shown) for receiving seawater from the water environment about the apparatus, and an outlet (also not shown) through which seawater is discharged under high-pressure. Typically, the seawater under high-pressure is piped to shore, as alluded to previously.

The pumping circuit 41 comprises a pump system 43, which in this embodiment comprises two reciprocating pumps 45, 47 operating in opposition (in the sense that one pump performs a discharge stroke while the other performs an intake stroke and vice versa). Each pump 45, 47 comprises a piston and cylinder assembly 51 in which a piston (not shown) cooperates with a cylinder 53 to define a pumping chamber (not shown). A piston rod 55 is connected to the piston for imparting reciprocating motion to the piston. In this embodiment, the cylinder 53 incorporates an elastomeric sheath which defines a deformable boundary surface of the pumping chamber, and which cooperates with the piston whereby reciprocating movement of a piston causes expansion and contraction of the elastomeric sheath to change the volume of the pumping chamber. Expansion of the elastomeric sheath corresponds to a volume reduction of the pumping chamber, and contraction of the elastomeric sheath corresponds to a volume expansion of the pumping chamber. A typical example of such a pump is described in the aforementioned PCT application with reference to FIGS. 51 and 52 of the drawings thereof.

The pumps 45, 47 are connected to a common delivery line (not shown) along which the pressurised seawater is piped to shore. An accumulator may be associated with the delivery line for achieving a more steady fluid flow (i.e. smaller fluctuations in the flow).

The pumps 45, 47 are operably connected to the diaphragm 25 through a lever mechanism 61.

The lever mechanism 61 comprises a lever 63 defined by two interconnected lever elements 64 disposed in laterally spaced relation.

One end of the lever 63 is pivotally connected at fulcrum 65 to a support structure 66 mounted on the chamber inner wall 17, and the other end of the lever 63 is connected to the diaphragm 25 through connecting rod 67.

The connecting rod 67 is pivotally connected to the rigid portion 28 of the diaphragm 25 by way of pivotal joint 69. The connecting rod 67 is also pivotally connected to the adjacent end of the lever 63 by way of pivotal joint 71.

The pumps 45, 47 are operably connected to the lever 63 at a location intermediate the ends of the lever 63. Specifically, the pumps 45, 47 are positioned on opposed sides of the lever 63, and the cylinders 53 carried on the support structure 66. The piston rods 55 are connected to the lever 63 through a connecting frame 73 mounted on the lever. The connecting frame 73 has two longitudinal frame elements 75 connected one to each lever element 64, with cross elements 77 supported between the longitudinal frame elements 75. Each piston rod 55 is connected to a respective one of the cross elements 77. With this arrangement, angular movement of the lever 63 causes the piston rods 55 to undergo reciprocatory movement in opposition, with one rod undergoing extension while the other undergoes retraction, and vice versa.

Because of the geometry of the lever 63, the velocity ratio of the pumping system 43 with respect to the deflecting diaphragm 25 is less than 1.0. In other words, the stroke length of each pump 45, 47 is less than the amplitude of displacement of the diaphragm 25 as it moves in response to wave action. The lever 63 increases the force acting on each pump 45, 47 by a given ratio and reduces the stroke by the same ratio. The reduction in stroke length provides for compact construction so that the pumps 45, 47 can be readily accommodated within the working chamber 27.

Seawater taken into the pumping circuit 41 is filtered. The filtering function is performed by a sand filtration system (not shown) which utilises the saturated sand contained within the ballast chamber 21.

Operation of the apparatus 10 according to the first embodiment will now be described. In conditions where the sea is calm, the apparatus 10 is submerged and there is a constant head of seawater above the diaphragm 25. The diaphragm 25 is maintained at a predetermined position by appropriate air pressure within the working chamber 27 so as to balance downward forces on the diaphragm 25 arising from various factors including the weight of the diaphragm and equipment attached thereto, the restoring force of the elastomeric outer portion 29 of the diaphragm, and the hydrostatic pressure of the calm water and ambient atmosphere pressure.

The passage of a wave over the apparatus 10 causes a time varying force to be exerted on the diaphragm 25, so causing the latter to move downwardly in response to this increasing force. The force is transmitted to the lever 63 through the connecting rod 67, causing angular movement of the lever 63 about its fulcrum 65. The force is transmitted through the lever to the piston rods 55, causing pump 47 to undergo an intake stroke taking in a charge of seawater, and also pump 45 to undergo a discharge stroke expelling a charge of seawater under pressure.

The downward deflection of the diaphragm 25 causes a reduction in the volume of the working chamber 27 and a corresponding increase in the pressure of air confined therein. The air pressure continues to rise as the diaphragm 25 is deflected until an equilibrium condition is established between the force applied by the passing wave on the diaphragm 25 and the sum of the reaction forces exerted on the diaphragm 25 by the air pressure and the net restoring forces of the elastomeric outer portion of the diaphragm. At this point, the diaphragm 25 will momentarily come to rest at its maximum deflection. Thereafter, the pressure on the diaphragm 25 will be unbalanced, so causing the diaphragm to reverse its motion as the force due to the air is reasserted. Meanwhile, the head of water diminishes as the wave passes over the apparatus 10. The diaphragm 25 then returns to its equilibrium position, awaiting the next wave. During the return movement of the diaphragm 25, the lever 63 is caused to undergo angular movement in the return direction, so causing pump 47 to undergo a discharge stroke and pump 45 to undergo an intake stroke.

Because the pumps 45, 47 act in opposition, fluid pressure generated in the discharge stroke of each pump provides hydraulic resistance which assists in regulating the rate of displacement of the diaphragm 25 in both downward and upward directions. This may assist in dampening fluctuations in the rate and extent of movement of the diaphragm.

The dynamic response of the apparatus 10 can be adjusted over a wide range through judicious manipulation of key parameters, including the total mass of the diaphragm 25 and attached equipment, as well as the total air volume and air pressure within the working chamber 27.

During normal operation, variations in the tidal conditions may be compensated for by adjusting the fluid pressure within the working chamber 27 to vary the steady state height of the diaphragm 25 within certain limits. As alluded to early the fluid within the working chamber 27 is typically air. The air pressure can be adjusted via an airline extending to a control station (e.g. onshore) from which compressed air can be delivered to and extracted from, the airline for adjusting the air pressure.

Referring now to FIGS. 4 and 5 of the drawings, there is shown apparatus 90 according to a second embodiment. The apparatus 90 is similar in many respects to apparatus 10 according to the first embodiment and so corresponding reference numerals are used to identify corresponding parts.

In the apparatus 90 according to the second embodiment, the lever mechanism 61 is guided as it undergoes reciprocating movement in response to movement of the diaphragm 25 under the influence of wave action. The guided movement is provided by way of a guide mechanism 91 comprising a guide structure 93 moveable along a guide 95. In this embodiment, the guide 95 is provided by the inner surface 97 of the cylindrical inner wall 17.

The guide structure 93 comprises a guide frame 101 attached to the underside of the rigid portion 28 of the diaphragm 25. The guide frame 101 supports guide rollers 103 in rolling engagement with the wall surface 97. The guide frame 101 includes a plurality of circumferentially spaced longitudinal elements 105, each of which carries two of the guide rollers 103 spaced along the longitudinal element.

Cooperation between the guide structure 93 and the wall surface 97 guides movement of the diaphragm 25 in response to the wave action, ensuring that the diaphragm does not deflect angularly (tilt) during its movement.

Referring now to FIGS. 6 to 9, there is shown apparatus 110 according to a third embodiment. The apparatus 110 comprises a body structure 111 of generally rectangular construction, having a base 113 which rests on the seabed, two opposed side walls 115, two opposed end walls 117, and a top wall 119.

Two cylindrical inner walls 121, 122 are provided within the body structure 111 between the base 113 and the top wall 119.

Each cylindrical inner wall 121, 122 is closed at the bottom by the base 113 and opens onto the top wall 119 to define an opening 127 which is closed by a respective diaphragm 129. With this arrangement, the base 113, the inner walls 121, 122 and the diaphragms 129 cooperate to form two cells 130 each defining a working chamber 123.

Each diaphragm 129 comprises a rigid central portion 131 and a flexible outer portion 133 surrounding the central portion. The outer periphery of each diaphragm 129 is sealingly connected to the upper periphery of its respective inner cylindrical wall 121, 122.

A stabilising support 134 is provided around the perimeter of the rigid central position 131, connecting the central portion 131 to the upper periphery of the respective inner cylindrical wall 121, 122. This is for the purpose of preventing over-stretching of the flexible outer portion 133, as well as excessive tilt and excessive vertical and horizontal displacement of the diaphragm 129 in response to wave action.

In this embodiment, the stabilising support 134 comprises a cable 136 laced back and forth between the central portion 131 and the wall 121, 122.

The working chambers 123 disposed below the diaphragms 129 are interconnected by way of a passage 135 extending between the cylindrical inner walls 121, 122.

The working chambers 123, as well as the interconnecting passage 135, contained a compressible fluid, which conveniently is air in this embodiment. The passage 135 has sufficient cross-sectional flow area to allow free passage of the compressible fluid between the working chambers.

The two cells 130 are spaced apart in a direction which typically corresponds to the direction of wave travel, with the spacing being such that the diaphragms 129 move in anti-phase. This is typically achieved by having the spacing between the centres of the diaphragms 129 corresponding to half the wave length of a typical wave in the locality of use of the apparatus 110.

The region within the body structure 111 surrounding each cell 130 defines a ballast chamber 141 for receiving ballast material which in this embodiment comprises saturated sand. The ballast material is introduced into the ballast chamber 141 through ports 143 incorporated in the top wall 119.

The apparatus 110 further includes a pumping circuit 145 having an intake for receiving seawater from the water environment about the apparatus and an outlet through which the seawater is discharged under pressure.

The pumping circuit 145 comprises a pump system 147 comprising two reciprocating pumps 151, 152 operating in opposition, in the sense that one pump performs a discharge stroke while the other performs an intake stroke and vice versa. Operation of the pumps 151, 152 in opposition allows a more uniform delivery of high-pressure seawater from the apparatus 110, as the pumps sequentially perform pumping strokes.

The pumps 151, 152 are each disposed in a respective one of the working chambers 123.

Each pump 151, 152 comprises a housing 153 fixed to the base 113 and a piston 155 cooperating with the housing 153 to define a pumping chamber 157. The housing 153 incorporates an elastomeric sheath 159 which cooperates with the piston, whereby reciprocating movement of the piston causes expansion and contraction of the elastomeric sheath. Expansion of the elastomeric sheath 159 corresponds to a volume reduction of the pumping chamber 157 and contraction of the elastomeric sheath corresponds to a volume expansion of the pumping chamber. Each pumping chamber 157 has an associated valve system (not shown), comprising an inlet valve adapted to open upon volume expansion of the pumping chamber and adapted to close upon volume reduction of the pumping chamber, and an outlet valve adapted to close upon volume expansion of the pumping chamber and to open upon volume reduction but only after seawater contained within the pumping chamber has attained a prescribed pressure. With this arrangement, seawater is discharged from each pumping changer at a higher pressure than that at which it is induced into the pumping chamber.

Each pump 151, 152 is operably connected to the diaphragm 129 associated with its respective cell 130 through a lever mechanism 161. The lever mechanism 161 comprises a lever 163 one end of which is pivotally connected at fulcrum 165 to a support structure 167. The other end of the lever 163 is connected to the respective diaphragm 129 through a connecting rod 169. The connecting rod 169 is connected to the rigid portion of the diaphragm 129 by way of connection 171 which in this embodiment is a rigid connection, although in certain applications a pivotal connection may be contemplated. The connecting rod 169 is also connected to the adjacent end of the lever 163 by way of connection 173 in the form of a spherical connection to accommodate universal angular movement between the lever 163 and the connecting rod 169.

The pumps 151, 152 are each connected to its respective lever 163 at a location intermediate the ends of the lever. With this arrangement, the stroke length of each pump 151, 152 is less than the amplitude of displacement of the respective diaphragm 129 to which it is connected through the lever mechanism 161, as was the case with the earlier embodiments.

Seawater taken into the pumping circuit 145 is filtered. The filtering function is performed by a sand filtration system which utilises the saturated sand contained within the ballast chamber 141 as a filtering medium. Seawater can enter the ballast chamber 140 through an inlet 175 incorporated in the body structure 111.

In operation, the diaphragms 129 of the two cells 130 operate in anti-phase owing to their spacing in relation to the wave lengths of waves to which they are typically exposed in the environment of use. With such an arrangement, the pump in one cell performs a pumping stroke while the pump in the other cell performs an intake stroke, and vice versa.

Referring now to FIGS. 10 to 26, there is shown apparatus 200 according to a fourth embodiment. The apparatus 200 comprises a body structure 201 of generally rectangular construction, having a base 203 which rests on the seabed, two opposed side walls 205, two opposed end walls 207, and a top wall 209.

Two cylindrical inner walls 211, 212 are provided within the body structure 201 between the base 203 and the top wall 209.

Each cylindrical interior wall 211, 212 is closed at the bottom by the base 203 and opens onto the top wall 209 to define an opening 213 which is closed by a diaphragm 215. With this arrangement, the base 203, the walls 211, 212 and the diaphragms 215 cooperate to form two cells 217 each defining a working chamber 219.

Each diaphragm 215 is of similar construction to the diaphragm of the previous embodiment, involving a rigid central portion 221 and a flexible outer portion 223 surrounding the central portion. The outer periphery of each diaphragm 215 is sealingly connected to the upper periphery of its respective inner cylindrical wall 211, 212.

The working chambers 219 disposed below the diaphragms 215 are interconnected by way of a passage 225 extending between the cylindrical inner walls 211, 212.

The working chambers 219, as well as the interconnecting passage 225, contain a compressible fluid, which conveniently is air in this embodiment. The passage 225 has sufficient cross-sectional flow area to allow free passage of the compressible fluid between the working chambers.

The two cells 217 are spaced apart in a direction which typically corresponds to the direction of wave travel, with the spacing being such that the diaphragms 215 move in anti-phase. This is typically achieved by having the spacing between the centres of the diaphragms corresponding to half the wave length of a typical wave in the locality of use of the apparatus 200.

The region within the body structure 201 surrounding the cells 217 defines a ballast chamber 227 for receiving ballast material which in this embodiment comprises saturated sand. The ballast material is introduced into the ballast chamber 227 through ports 229 incorporated in the top wall 209.

The apparatus 200 includes a pumping circuit 231 through which seawater from the water environment about the apparatus is taken and from which seawater is discharged under pressure.

The pumping circuit 231 comprises a plurality of pumps 233 in each cell 217, there being three pumps in each cell in this embodiment. The three pumps 233 in each cell 217 are arranged in a triangular formation, as best seen in FIG. 18 of the drawings, so as to be at 120 degree spacings. Each pump 223 has an intake port 235 and a discharge port 237, with the intake port 235 communicating with a respective collection tank 239 which receives seawater at a pressure determined by the hydrostatic pressure of seawater at the depth at which the tank is located. The seawater contained within each tank 239 is filtered, as will be explained in more detail later. The discharge port 237 of each pump 233 communicates with a manifold 241 via a discharge line 243. The manifolds 241 of the two cells 217 communicate with piping 245 along which seawater can be pumped under pressure to a remote location such as ashore.

The pumps 233 in each cell 217 are operably connected to the respective diaphragm 215 of the cell.

Each pump 233 comprises a reciprocating pump of similar construction to the pumps of the previous embodiment, in the sense that it involves a housing 251 and a piston 253 cooperating to define a pumping chamber 255.

In this embodiment, a guide structure 257 is provided for guiding movement of the piston 253 with respect to the housing 251. The guide structure 257 comprises a yolk 259 pivotally mounted at 260 on a connecting rod 261 attached to the piston 253. The yolk 259 carries guide rollers 263 which are in rolling engagement with the outer surface of the housing 251, as best seen in FIG. 16 of the drawings. With this arrangement, cooperation between the yolk 259 and the housing 251 serves to provide axial guidance for the piston 253 as it reciprocates with respect to the housing 251.

Each pump 233 is operably connected to the diaphragm 215 of its respective cell 217 through a respective lever mechanism 271. Thus, each cell 213 incorporates three lever mechanisms 217, one corresponding to each pump 233.

Each lever mechanism 271 comprises a lever 273 pivotally connected at fulcrum 275 to a support 277 accommodated within the respective cell 217. The support 277 within each cell 217 forms part of a common support structure 279 which is accommodated in the two cells and the passage 225 extending therebetween. This provides for a robust support arrangement for the levers 273.

As best seen in FIG. 14, each support 277 is of framed construction and of generally triangular configuration. Adjacent each apex of the triangular support 277 there is provided a mount 291 configured as a yolk for pivotally supporting a respective one of the levers 273. Each lever 273 is pivotally connected to its respective mount 291 at the fulcrum 275. For sake of clarity in the drawings, only one lever 273 is shown in FIGS. 14 and 15.

Each lever 273 is of framed construction to provide both lateral and vertical rigidity, as was the case with the previous embodiment. The fulcrum 275 is located intermediate the ends of the lever 273 but close to one end at which a counterweight 295 is provided. The other end of each lever 273 is connected to the respective diaphragm 215 through a connecting rod 297. The connecting rod 297 is connected to the rigid portion 221 of the diaphragm 215 by way of a connection 299 which in this embodiment is a rigid connection. The connecting rod 297 is also connected to the adjacent end of the lever by way of a pivotal connection 301 having a pivot axis substantially parallel to the axis of angular movement of the lever 273 about the fulcrum 275. The three connecting rods 297 attached to the rigid portion 221 of the diaphragm 215 serve to provide relatively stable support for the diaphragm as it deflects in response to wave action.

Each pump 233 is pivotally connected to its respective lever 273 at pivot 305 which is intermediate the fulcrum 275 and the end of the lever onto which the connecting rod 297 is connected. As with previous embodiments, this arrangement provides that the stroke length of each pump 233 is less than the amplitude of displacement of the diaphragm 215 to which it is connected through the respective lever mechanism 271.

The counterweight 295 may be adjustably mounted on the lever 273 for the purposes of selectively varying the extent of counterbalancing force if so desired.

As previously mentioned, seawater taken into the pumping circuit 231, and in particular delivered to the tanks 239, is filtered. The filtering function is performed by a sand filtration system 310 which utilises the saturated sand contained within the ballast chamber 227. The filtering system 310 incorporates the storage tanks 239, one corresponding to each pump 233, as previously mentioned. Each storage tank 239 receives filtered seawater via filter pipe 311 which is extends into the ballast chamber 227 and which is provided with a plurality of inlet holes 313 along the length thereof. The portion of the filter pipe 311 accommodated within the ballast chamber 227 is surrounded by a secondary filter 315 comprising a filter medium 316 (such as washed gravel or other porous granular material) confined within a perforated filter housing 317. The perforated filter housing 317 is constructed as a removable unit which can be withdrawn from around the filter pipe 311 for cleaning and other regular maintenance procedures. The filter housing 317 is accessible exteriorly of the body structure 201 and handles 319 are provided on the outer side thereof to assist with installation and removal of the filter housing.

Seawater from the saturated ballast material will percolate under hydrostatic pressure through the porous filter housing 317 and the filter medium 316 contained therein, and then into the storage tank 239. Because of the large volume of sand ballast material within the structure, a high level of filtration of the seawater is achieved.

There is of course a facility for replenishment seawater to enter the ballast chamber 227 and maintain the sand ballast material in a saturated condition. This may be achieved in any appropriate way, such as allowing water to enter through the ports 229 incorporated in the top wall 209 of the body structure 201.

Details of the flexible outer portion 223 of the diaphragm 215 are illustrated in FIGS. 23 to 26. The flexible outer portion 223 comprises a membrane 224 formed of natural rubber, reinforced with fibre matting.

The stiffness and length of the diaphragm outer portion 223 is selected so that it bulges upwardly (as seen in FIG. 23) under the influence of the pressure difference between the air pressure within the working chamber 219 and the hydrostatic pressure of the seawater covering the diaphragm 215. It is believed that this is an important feature as it minimises the formation of concave troughs in the diaphragm outer portion 223 that might trap water during the upstroke of the diaphragm 215 and cause excess dynamic loading on the elastomeric material providing the outer portion.

The maximum height of the diaphragm 215 can be set during the design specification to be at any level relative to the top of the body structure 201; this can be either proud, flush or recess. This allows the apparatus to be tailored for specific sea conditions; for example, for light conditions it is likely that the rigid central portion 221 of the diaphragm 215 will be in a proud condition, and for heavier sea conditions it is likely that the rigid central portion 221 will be flush or recessed.

FIG. 24 illustrates various conditions that the flexible outer portion 223 can assume as the diaphragm 215 moves between its upper most condition and lower most condition, both of which are depicted in phantom lines. The three illustrated conditions are an uppermost condition A, a lowermost condition B, and an intermediate condition C which is depicted in solid lines.

Because of the extent to which the flexible outer portion 223 of the diaphragm 215 can flex during its excursions between the upper most and lower most conditions, it is desirable to have joints which accommodate such movement where the flexible outer portion 223 is connected at its inner periphery to the rigid central portion and also where the flexible outer portion is connected at its outer periphery to the respective inner cylindrical wall 211, 212.

The joint at the inner periphery is illustrated in FIG. 25 and comprises a rolling transition joint 341. The joint 341 incorporates two clamping rings 343, 344, each of circular cross-section. Clamping ring 343 is mounted on annular clamping plate 345 which is fixed to the rigid inner portion 221 of the diaphragm. Clamping ring 344 is mounted on a further annular clamping plate 347 which is connected to the fixed clamping plate 345 by way of a plurality of circumferentially spaced nut and bolt assemblies 349. Each nut and bolt assembly 349 incorporates a spacer 350 between the two clamping plates 345, 347.

Plate 347 incorporates a web 351 which bears on fixed plate 345 and also locates adjacent the inner periphery of the flexible outer portion 223 of the diaphragm 215.

With this arrangement, the membrane 224 is sandwiched between the clamping plates 345, 347, with the clamping rings 343 and 344 in pressing engagement therewith to define arcuate surfaces about which the membrane rolls during deflection of the diaphragm 215.

The membrane 224 incorporates a thickened section 353 at its inner periphery portion which is disposed beyond the clamping rings 343, 344 to enhance the robustness to the joint 341 and resist the membrane 224 being pulled through the bite region defined between the two clamping rings.

As can be seen in FIG. 26, a somewhat similar construction is employed at the other transition joint.

The joint at the outer of periphery of the diaphragm 215 is illustrated in FIG. 26 and comprises a rolling transition joint 361. The joint 361 incorporates two clamping rings 363, 364, each of circular cross-section. Clamping ring 363 is mounted on annular clamping plate 365 which is fixed to the cylinder wall 211. Clamping ring 364 is mounted on a further annular clamping plate 367 which is connected to the fixed clamping plate 365 by way of a plurality of circumferentially spaced nut and bolt assemblies 369. Each nut and bolt assembly 369 incorporates a spacer 371 between the two clamping plates 365, 367.

Plate 367 incorporates a web 373 which bears on fixed plate 365 and also locates adjacent the outer periphery of the flexible outer portion 221 of the diaphragm 215.

With this arrangement, the membrane 224 is sandwiched between the clamping plates 365, 367, with the clamping rings 363 and 364 in pressing engagement therewith to define arcuate surfaces about which the membrane rolls during deflection of the diaphragm 215.

The membrane 224 incorporates a thickened section 373 functioning in a similar fashion to thickened section 353.

FIG. 27 schematically illustrates a variation in the construction of the diaphragm and the manner of its attachment in position. In the arrangement shown in FIG. 27, there is a membrane 291 which extends entirely across the rigid central portion 221 and beyond the periphery thereof to provide the outer flexible portion 223. The rigid central portion 221 has a tube 293 at its periphery around which the membrane 291 can roll as the diaphragm undergoes displacement. The membrane 291 passes around a further tube 295 at the outer periphery thereof for attachment to the cylinder wall 211. It should be noted that FIG. 27 illustrates the diaphragm 215 in two extreme conditions, one being an upper-most condition and the other being a lower-most condition.

In FIG. 28 there is illustrated apparatus 400 according to a still further embodiment. The apparatus 400 according to this embodiment is substantially the same as the previous embodiment and so corresponding reference numerals are employed to identify like parts. The apparatus 400 incorporates an anchoring system 401 for anchoring the body structure 201 to the seabed. The anchoring system 401 employs suction for anchoring purposes. The suction effect is established by a suction chamber on the underside of the body structure 201, the suction chamber being sealed apart from an open bottom thereof. The suction chamber is defined by a rigid skirt provided around the periphery of the body structure 201, depending from the base 203. The skirt may typically extend about one metre downwards beyond the base, so that when the apparatus is deployed on the seabed, the skirt will be submerged to its full depth. The skirt is in effect defined by downward extensions of the two side walls 205 and two end walls 207, thereby enclosing a volume below the base to define the open-bottomed suction chamber.

Piping means (not shown) are provided for communicating with the enclosed volume within the suction chamber once in position on the seabed for extracting air therefrom for the purposes of achieving suction anchoring. The piping can also be employed for delivery of air into the enclosed volume in the event that the device is to be subsequently released from the suction anchoring effect.

Scouring of sand on the seabed around the anchored apparatus may be mitigated by the use of gabions and/or matting 407 attached around the perimeter of the apparatus and held firmly down on the seabed.

A variation to the arrangement disclosed is that the underside area of the body structure 201 can be constructed in a segmented fashion to define a suction zone comprising a plurality of discrete suction chambers. Such a construction will prevent total loss of suction in the event of the apparatus 400 tilting, in which case only segments rising above the seabed will lose suction while the remaining segments will remain buried to preserve the suction anchoring effect.

In the embodiments illustrated previously, lever mechanisms were confined to individual cells, and so the lever ratio effect was limited by the lateral dimensions of each particular cell.

One way in which the lever ratios can be increased would be to arrange the levers so that they can extend between the two cells, passing through the passage therebetween. With such an arrangement, the lever could be connected at one end to the diaphragm of one cell with the fulcrum of the lever being provided in the other cell. One such arrangement is illustrated in the embodiment shown in FIG. 29 wherein the two levers 411, 412 are positioned in side-by-side relationship, with one lever 411 being operably connected to the diaphragm of the first cell 413 and attached to a support structure (not shown) providing the fulcrum in the second cell 415. Likewise, the other lever 412 is attached to the diaphragm of the second cell 415 and attached to a support structure defining the fulcrum in the first cell 413.

In the embodiment shown in FIG. 29, the two levers 411, 412 were positioned in a side-by-side disposition. Other arrangement are of course possible. One such other arrangement is illustrated in the embodiment shown in FIG. 30 where the levers 411, 412 are interleaved.

Referring now to FIG. 31 of the drawings, there is shown a further embodiment 420 which involves two cells 421, 422 interconnected by a passage 423 for fluid communication therebetween, but with only cell 422 incorporating diaphragm 425. Cell 421 incorporates a rigid top rather than a diaphragm; accordingly, it is a fixed volume. With such an arrangement, the volume of the two cells 421, 422, as well as the passage 423 therebetween, provides a working chamber. This arrangement permits a lever 427 of extended length, with the lever 427 being connected to the diaphragm 425 of cell 422 and pivotally supported at fulcrum 429 in cell 421.

In this embodiment, the lever 427 operates two pumps 431, 432 disposed on opposed sides of the fulcrum 429, whereby the pumps operate in opposition. In this way, one pump can perform a pumping stroke while the other performs a suction stroke, and vice versa.

In this embodiment, dampening employed to decelerate the lever 427 and diaphragm 425 at the end of downward motion. The final stage of the diaphragm downward motion corresponds to high diaphragm velocities, so a soft dampening is required. This may be achieved by dampener structures 437 such as elastomer air springs or simply a soft elastomer material such as stacks of automobile tyres laid flat. Alternatively, the dampening process may utilise a damping fluid in which case the dampener structure may comprise a pump be used and some of this end stroke energy can be harnessed. The dampening fluid may comprise seawater, in which case the dampening pump may form part of the seawater pumping system along with the pumps at the other end of the lever.

Referring now to FIGS. 32 to 44, there is shown apparatus 450 according to a still further embodiment. The apparatus 450 comprises a body structure 451 of generally rectangular construction, having a base 453 which rests on the seabed 454, two opposed side walls 455, two opposed end walls 457, and a top wall 459.

The body structure 451 incorporates two cells 461, 462 interconnected by a passage 463 for fluid communication therebetween,

Cell 461 is of a fixed volume and is defined between an inner cylindrical wall 465 which is closed at the bottom end by the base 453 and closed at the upper end by top wall 459. Cell 462 is of a variable volume and is defined between an inner cylindrical wall 467 which is closed at the bottom end by base 453 and which opens onto the top wall 459 to define an opening 469. The opening 469 is closed by a diaphragm 471. With such an arrangement, the volume of the two cells 461, 462, as well as the passage 463 therebetween, provides a working chamber 473.

A tower 475 extends upwardly from the body structure 451 to provide access to cell 461 when the apparatus 450 is installed in position on the seabed 454. The upper end of the tower 475 thus extends above sea level, as illustrated in FIGS. 36, 37 and 38 where the sea level is depicted by a line identified by reference numeral 476. While the tower 475 is particularly advantageous for the development and testing phase of the apparatus when regular access to the interior of the body structure may be necessary, it may not necessarily be required in any production version of the apparatus.

As with previous embodiments, the diaphragm 471 comprises a rigid central portion 481 and a flexible outer portion 483 surrounding the central portion. The outer periphery of the diaphragm 471 is sealingly connected to the upper periphery of the inner cylindrical wall 467.

The working chamber 473 contains a compressible fluid, which conveniently is air in this embodiment. The passage 463 has sufficient cross-sectional flow area to allow free passage of the compressible fluid between the two cells 461, 462. A delivery system, including supply line 484 extending from a control station based on shore, is provided for supplying, and regulating the pressure of, the compressible fluid within the working chamber 473.

The region within the body structure 451 surrounding each cell 461, 462 defines a ballast chamber 485 for receiving ballast material which in this embodiment comprises saturated sand. The ballast material is introduced into the ballast chamber 485 through ports (not shown) incorporated in the top wall 459.

The apparatus 450 further includes a pumping circuit 491 (as best seen in FIGS. 41 and 42) having an intake 493 for receiving seawater from the water environment about the apparatus and an outlet 495 through which the seawater is discharged under pressure.

The pumping circuit 491 comprises a pump system 500 comprising two reciprocating pumps 501, 502 operating in opposition, in the sense that one pump performs a discharge stroke while the other performs an intake stroke and vice versa. Operation of the pumps 501, 502 in opposition allows a more uniform delivery of high-pressure seawater from the apparatus 450, as the pumps sequentially perform pumping strokes.

Each pump 501, 502 comprises a reciprocating pump of similar construction to the pumps of previous embodiments, in the sense that it involves a housing and a piston cooperating to define a pumping chamber.

Each pump 501, 502 is operably connected to the diaphragm 471 through a lever mechanism 510.

The lever mechanism 510 comprises a lever 511 extending between the two cells 461, 462 via the passage 463. The lever 511 is pivotally connected at fulcrum 513 to a support 514 accommodated within cell 461.

The lever 511 is of framed construction to provide both lateral and vertical rigidity, as was the case with previous embodiments. The fulcrum 513 is located intermediate the ends of the lever but close to one end. The other end of the lever 511 is connected to the rigid central portion 481 of the diaphragm 471 through a rigid coupling frame 515. With this arrangement, the lever 511 provides relatively stable support for the diaphragm 471 as it deflects in response to wave action, as illustrated in FIGS. 36, 37 and 38. This is because the rigid portion 481 of the diaphragm 471 moves in unison with the lever 511 owing to the rigid connection therebetween provided by the coupling frame 515.

Each pump 501, 502 is pivotally connected to the lever 511 on opposed sides of the fulcrum 513.

The pumping circuit 491 includes the inlet 493 into which filtered seawater is drawn and the outlet 495 adapted for connection to a subsea pipeline for conveying high-pressure seawater generated by the apparatus to shore. As was the case with earlier embodiments, the inlet 493 incorporates a filtration system 521 which utilises saturated sand contained within the ballast chamber 485 as a filtering medium. There is also provision for back flushing the filtration medium.

The pumping circuit 491 includes a high-pressure line 525 extending between the outlets 526 of the pumps 501, 502 and the pumping circuit outlet 495 has provision for damping pulsations in the high-pressure flow for the purposes of achieving a more steady-state flow condition. This is achieved in this embodiment by the provision of a series of pulsation dampeners 527 at intervals along the line.

The inlet line 528 of the pumping circuit between the inlet 493 and the pumps 501, 502 incorporates a water accumulator 529.

There is also provision within the working chamber 473 for removal of any extraneous water that may accumulate within it. This is achieved in this embodiment by provision of a sump 531 into which the extraneous water can flow, and a bilge pump 533 for pumping water collected within the sump 531 into the water accumulator 529.

The apparatus 450 also has provision to prevent or at least mitigate scouring of sand on the seabed around the apparatus once it is in position. In this embodiment, this is achieved by the use of matting 531 around the periphery of the body structure 451. The matting is attached to the periphery of the body structure 451 and rests on the seabed. In this embodiment, the matting 531 comprises a plurality of rectangular mat sections 533 connected one to another. Each mat section 533 comprises a plurality of blocks 535 (typically concrete blocks) positioned in an array and connected one to another. With this arrangement, the blocks can articulate one with respect to another (to at least a limited degree) in order that the mat section 533 can conform to the profile of the seabed on which it rests.

In each of the embodiments described, the apparatus has been operating in isolation. It should be appreciated that apparatus according to any of the previous embodiments can be incorporated in an array.

One such array is illustrated in FIGS. 45 and 46, where a common housing structure 550 is employed for cost-effectiveness. The common housing structure 550 accommodates multiple cells 551.

A further arrangement is illustrated in FIG. 47 where there is a plurality of arrays 560 spaced across a wave front so as to avoid interaction with each other. The spacing is determined from the interaction length which scales as λ/2π, where λ is wavelength.

In the arrangement illustrated, each array 560 comprises a series of four cells 561, 562, 563 and 564.

Waves entering from the left of the figure and parallel to the longitudinal axes of the arrays will cause responses that are in phase across each of the arrays. In other words, the first cells 561 in the arrays 560 will operate in phase, as will be the second cells 562, the third cells 563 and the fourth cells 564. A wave entering at other angles may cause some de-phasing of the units. Analysis of the phase responses shows that there is an angle of acceptance that defines the direction of incoming waves that produce acceptable levels of energy output from such an arrangement. The angle is dependent upon many parameters but, for an optimised system may lie between 90 degrees and 120 degrees.

Modifications and improvement may be made without departing from the scope of the invention.

Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Wave Energy Converter

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CPC

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