GB2509201A

GB2509201A - Wave powered pump with flexible diaphragms facing in opposite directions

Info

Publication number: GB2509201A
Application number: GB1315306.9A
Authority: GB
Inventors: Simon Grey; Fraser Johnson
Original assignee: AWS Ocean Energy Ltd
Current assignee: AWS Ocean Energy Ltd
Priority date: 2012-10-12
Filing date: 2013-08-28
Publication date: 2014-06-25
Also published as: GB201218394D0; GB201315306D0

Abstract

A wave energy conversion device 5 has first and second parallel support structures 10, 15 joined by joining sections 20 with at least one energy absorber 25 having a flexible working surface 35 which at least partially defines a chamber for receiving a working fluid e.g. air. The working surface 35 is displaced by pressure or force of wave action to drive the working fluid. The working surfaces 35 of the two support structures 10, 15 face in opposite directions. The support structure 10 facing the prevailing waves may be longer than the second support 15, and may have more wave energy absorbers 25. The energy conversion device may include a removable cassette comprising the working surface 35, a frame and/or clamp and/or saddle or limiting apparatus (figure 7).

Description

ENERGY CONVERSION DEVICE

FIELD OF THE INVENTION

The present invention relates to an energy conversion device, and particularly a wave energy conversion device.

BACKGROUND TO THE INVENTION

Various forms of energy conversion device are known in the art for the extraction of energy from renewable resources. One species of energy conversion device involves the extraction of energy from natural fluid motion, such as from wind, water currents, waves, tides, cascading fluids and the like. Such energy conversion devices typically operate by using fluid motion to drive a turbine to produce mechanical shaft work, which may then be used directly as an output, or to drive a generator to produce electricity.

Devices are known which arc arranged to use natural fluid motion to directly drive a turbine. That is, a reaction surface of a turbine may be arranged to be directly exposed to natural fluid motion, such as in wind turbines. However, in some cases natural fluid motion may be relatively slow requiring gearing arrangements and the like to achieve a useable output. Also, where energy is to be extracted from liquids, such as tidal streams and wave motion, energy losses may become significant due to higher densities and inertial forces and the like. To address such issues it is known in the art to utilise an intermediary medium which itself is caused to flow along a controlled path by natural fluid motion in a separate fluid body. For example, liquid motion, such as wave motion, may be used to act on and displace a working surface which in turn drives air through a duct to drive a turbine. In such arrangements a large working surface may be provided to maximise energy extraction from the liquid, and the air duct may be formed with a relatively small cross-sectional area such that the energy from the liquid may be manifested as kinetic energy in the air stream, thus permitting relatively high speed operation of the turbine.

In some known designs a diaphragm is used as a working surface, wherein one side of the diaphragm is exposed to fluid motion, such as wave motion, and an opposite side is exposed to an intermediary medium, such as air. One such design is know as the floating CLAM device, as described in The Clam Wave energy converter", F.P. Lockett, Wave Energy Seminar, Institute of Mechanical Engineers, London, Nov. 1991, ppl9-23. In this device a number of interconnected air cells each include a flexible diaphragm which separates an internal closed air system from the sea environment, wherein wave motion displaces the diaphragm to cause air flow between the cells and through Wells turbines which are coupled to generators.

The present invention seeks to provide an improved wave energy conversion device and/or solve or mitigate at least one problem with the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an energy conversion device comprising: at least one support structure; at least one of the support structure(s) comprising or supporting at least one energy absorber.

The at least one energy absorber may comprise at least one working surface.

The at least one energy absorber or working surface may at least partially define at least one chamber for receiving a working fluid.

At least part of at least one and preferably each energy absorber or working surface is displaceable responsive to a change in pressure or force exerted on the working surface to thereby drive the working fluid.

The at least one support structure may comprise a common structure. At least one and preferably each of the support structures may comprise one or more hull sections. The at least one support structure, energy absorber and/or the energy conversion device may comprise, be comprised in, fixable to or arranged to be mounted on a hull, an oil rig, a harbour wall, a side of a barge or other vessel, a breakwater, a sea bed or other geological or natural or man-made structure or other in-water structure or craft. The energy device, at least one support structure and/or at least one energy absorber may be releasably mounted or mountable, for example, to the hull, oil rig, harbour wall, side of a barge or other vessel, breakwater, a sea bed or other geological or natural or man-made structure, or other in-water structure or craft.

The energy conversion device may be or comprise a wave energy conversion device. The wave energy device may be configured to be at least partially immersed in a body of fluid, such as a sea or lake or other body of water. For example, the energy conversion device may comprise a floating or floatable, submerged or submergible or partially submerged or submergible device. The energy absorber(s) may be configured to be displaced by the body of fluid in which the device is at least partially immersed, for example, by wave or tidal motion or any other suitable action of the body of water that results in a variable pressure or force being applied to the energy absorber.

The energy conversion device and/or support structure may comprise a permanent or temporary structure.

Preferably and advantageously, the energy conversion device comprises two or more support structures. Preferably and advantageously, at least two and preferably each support structure comprises at least one and preferably a plurality of energy absorbers. It will be appreciated that, depending on the application, the number of energy absorbers/working surfaces and the area of each energy absorber/working surface may vary depending on the application. For example, the energy conversion device may comprise any number between one and a very large number of energy absorbers/working surfaces.

It will be appreciated that the size of the energy conversion device may vary depending on the size of the working surface/energy absorber and the number of working surfaces/energy absorbers and on the configuration and shape of the energy conversion device and/or support structures.

The energy absorber or working surface(s) may comprise at least one of a flexible surface, an elastic surface, an inelastic surface, a non-straining material, a bendable surface, a compliant surface, an accommodating surface and/or the like.

The energy absorber or working surface(s) may comprise a diaphragm or membrane.

The energy absorber or working surface may comprise or be configured to drive a piston or other movable, pressurising or pumping member or apparatus.

The chambers may be comprised in the respective support structures.

The chamber(s) may be in fluid communication with at least one conduit. The working fluid may comprise a gas, such as air. The working fluid may be pressurised. The energy conversion device may comprise means of controlling the pressure of the working fluid, such as a compressor, throttle valve or the like.

The energy conversion device may comprise at least one drivable apparatus that is drivable by the working fluid. The drivable apparatus may comprise a turbine and/or a generator, for example.

The driving of the working fluid may comprise forcing the working fluid into and/or out of the chamber. The driving of the working fluid may comprise forcing the working fluid through the at least one conduit. The driving of the working fluid may comprise pressurising and/or depressuring the working fluid. The action of driving the working fluid may in turn drive the drivable apparatus. The working fluid may be the same or different to the fluid of the body of fluid that acts to displace the energy absorber(s) or working surface(s).

The energy conversion device may comprise a saddle or other limiting apparatus for limiting motion of the energy absorber or working surface.

At least one and preferably each of the energy absorbers or working surfaces may be fixed to the rest of the respective chamber by a frame, clamp, or the like. At least the energy absorber and/or working surface and frame and/or clamp and/or saddle or limiting apparatus may comprise or be comprised in a corresponding cassette, which may preferably be a removable / interchangeable cassette. The cassettes may be recessed in to the associated support structure. This may improve energy capture, reduce structural loads and/or make the system more hydronomically efficient.

At least one and optionally each support structure may comprise one or more floor sections that extend at least partially and optionally entirely below at least one and preferably each cassette, e.g. so as to at least partially and optionally completely cover the bottom surface of at least one and preferably each cassette. In this way, unwanted forces, such as upward forces on the cassettes may be reduced. The cassettes and/or energy absorbers may be provided substantially vertically. The cassettes and/or energy absorbers may be raked, for example, between 5 and 200, preferably substantially ±15° from horizontal, optionally to be angled to face upwardly or downwardly. The angle of the cassettes and/or energy absorbers may be selected, selectable, variable and/or adjustable. For example, the cassettes, energy absorbers and/or support structure may comprise a plurality of attachment points for attaching the cassette(s) to the support structure or for attaching the energy absorbers to the rest of the cassette components or to the support structures. The cassette and/or energy absorber may be mountable using different attachment points in order to vary to the angle of the cassette and/or energy absorber. However, it will be appreciated that other angle setting or adjustment means would be apparent to a person skilled in the art, such as pivots, slides or other tilting or rotating mechanisms.

At least one and optionally each support structure may comprise or be provided or providable with a plurality of energy absorbers.

Each support structure may comprise at least one and optionally a plurality of cells. Each cell may comprise at least one energy absorber or working surface and/or cassette, the chamber(s) at least partially defined by the respective energy absorber or working surface(s) and optionally the associated conduit in fluid communication with the chamber(s).

The cell may be configured such that at least one and optionally each cell reacts with at least one and optionally each other cell.

At least one and optionally each cell may be connected to at least one working fluid main, such as a ring main, for example, via the at least one conduit.

The working fluid main may be in communication with the cells in at least one, preferably at least two and optionally each support structure.

At least one and optionally each cell may be individually isolatable and/or isolatable in groups. For example each conduit may comprise a valve, shutter, or other closing mechanism, which may be usable to isolate the associated cell.

A drivable apparatus may be provided in communication with at least one and optionally each conduit and/or chamber and/or cell. At least one and optionally each cell may be provided with an associated drivable apparatus. For example, the associated drivable apparatus may be provided in or connected to the conduit and/or chamber of the cell.

The drivable apparatus may be provided in series or parallel. The drivable apparatus may be linked, e.g. a drivable apparatus experiencing a high load may be configured to transfer some of the load to another drivable apparatus.

Each drivable apparatus may comprise a turbine that may drive a generator, such as a double-fed induction generator. The speed and voltage of the drivable apparatus may be controlled by an associated power converter, such as an AC/DC/AC power converter. The drivable apparatus may be adapted, configured or configurable to optimise the damping of one or more of the associated cells, e.g. by controlling airflow to and/or from the cell.

The turbine may be bi-directional, i.e. rotating in the same direction regardless of the direction of airflow. However, it will be appreciated that other suitable turbine arrangements exist and may be used.

When the drivable apparatus comprises an electrical generator, electrical output of at least two and optionally each generator may be aggregated, preferably at a lower voltage and may be transformed to a higher voltage for transmission ashore.

The or each support structure may comprise a machinery module. The machinery module may comprise at least one of: at least a portion of the working fluid main, at least a portion of the ring main, ducting and/or conduit for receiving the working fluid, the electrical generator, the drivable apparatus, any associated cables or electrical connections, the control system, and/or the like. The machinery module may be removable and/or interchangeable, e.g. by being provided with releasable connectors and/or fixing mechanism.

At least one of the cells may be configured such that it does not drive, e.g. it is not connected or connectable to, a drivable apparatus, e.g. it is a dummy cell.

Such dummy cells may be provided, for example, to provide compliance in the working fluid main and/or active or passive control of properties of the energy conversion device.

At least one drivable apparatus may be drivable by motion of working fluid in the working fluid main.

Two or more of the support structures may be integral. Two or more of the support structures may be separate, e.g. two or more of the support structures may not be directly joined to, and/or spaced apart from, each other. For example, two or more support structures may be arranged such that fluid from the body of fluid in which the device is immersed or immersable may pass between them. The two or more support structures may be configured to be buoyant in use.

The two or more support structures may be joined, for example by at least one joining section or member, such as a bracing section or member or strut. The two or more support structures may be spaced apart or separated with the at least one joining section or member provided therebetween. The joining sections or members may be oriented differently to at least one and optionally each support structure, e.g. obliquely oriented with respect to the support structure(s). The joining sections or members may be sections or members that do not have any energy absorbers, working surfaces and/or cells. It will be appreciated that the joining section or member may be provided only to hold and/or fix the support structures at required separations and orientations. Although some services may run through the joining section(s) or member(s), such as the working fluid main and/or electrical connections, the function of the joining sections or members may be primarily as spacers and/or structural members and optionally do not in themselves comprise energy absorbers or working surfaces.

Each support structure may be between 1 0m and 80m apart, preferably between 30 and GUm apart and most preferably between 40 and 50m apart. The energy conversion device may comprise adjustment apparatus for varying the separation of the support structures.

At least one support structure may be between 20 and 300m long. At least one support structure may be between 80 and 140m long.

At least one and optionally each of the support structures may comprise non-circular or non-arcuate support structures, e.g. linear support structures. At least one and optionally each support structure may be an elongated support structure.

At least one support structure may be provided parallel to at least one other support structure. At least one support structure may be longer than at least one other support structure. At least one support structure may be substantially the same length as at least one other support structure.

At least one support structure may be angled or obliquely oriented relative to at least one other support structure. At least one support structure may be oriented at an acute angle relative to at least one other support structure, for example between 300 and 600, most preferably between 40° and 500. At least one support structure may be oriented at an obtuse angle relative to at least one other support structure, for example, between 130° and 185° and most preferably between 150° and 165°. For example, two or more support structures may be arranged in a V-shaped or wedge shaped arrangement.

In a preferable arrangement, two primary support structures may be joined together and/or oriented at an acute angle relative to each other. At least one secondary support structure may be connected and/or oriented to at least one and preferably each of the primary support structures at an obtuse angle, for example, such that the secondary support structures are parallel to each other. Further support structures may be attached to each of the secondary support structures.

As another example, four or more support structures may be arranged so as to form at least part of a rhombus, diamond, kite, deltoid or the like.

It will be appreciated that a single energy absorber and/or support structure could also be used.

The energy conversion device may comprise a unitary and/or integral support structure. The energy conversion device may comprise a plurality of support structures joined or joinable together to form at least one hull, e.g. in modular fashion. One or more of the plurality of support structures may be oriented at the same and/or different angles to at least one and optionally each other support structure.

The support structure(s) may be arranged in a generally ring or loop or round or oval configuration. The support structure(s) may collectively define a closed or open shape. The support structures may be arranged so as to form a polygon configuration, such as a digon, triangle, quadrilateral, pentagon, hexagon, heptagon, octagon, nonagon, decagon, hendecagon, dodecagon, tridecagon, tetradecagon and/or the like. At least two and optionally each of the support structures may be arranged in parallel, e.g. to form a proa or catamaran or trimaran or quadmaran or pentamaran or the like type configuration.

At least one and optionally each support structure may be provided with a linearly extending array of energy absorbers.

At least one and optionally each energy absorber of at least one and optionally each support structure may be substantially oriented or face in the same direction as at least one and optionally each other energy absorber of the same support structure. At least one and optionally each energy absorber of at least one support structure may be configured to face in a different, e.g. opposite, direction to at least one and optionally each energy absorber of at least one other support structure.

At least one support structure may comprise a different number of energy absorbers and/or a different total energy absorber area, e.g. by comprising a different number of cells, to at least one other support structure. Each support structure may comprise one, two, three, four, five, six, seven, eight, nine, ton or more energy absorbers, for example. For example, one or more support structures may comprise three times as many energy absorbers and/or cells and/or three times as much total energy absorber area to at least one other support structure. The energy conversion device may be configured such that a number of energy absorbers and/or a total energy absorber area is provided or providable facing a first direction that is different to the number of energy absorbers and/or total energy absorber area provided facing a second direction, which is different to, e.g. opposite, the first direction.

At least one support structure may comprise the same number of energy absorbers and/or cells and/or total energy absorber area as at least one other support structure.

At least one and preferably each energy absorber on at least one and preferably each support structure may be arranged to face away from at least one other support structure, e.g. at least one and optionally each energy absorber of the energy conversion device may be outwardly or externally facing (with respect to the energy conversion device).

Optionally, at least one and preferably each energy absorber on at least one and optionally each support structure may be configured to face toward at least one other support structure, e.g. at least one and optionally each energy absorber of the energy conversion device may be inwardly facing.

At least one support structure may be provided with cells and/or energy absorbers only on one side or face of the support structure.

At least one support structure may be provided with cells and/or energy absorbers on opposing sides of the support structure. The number and/or spacing of cells and/or energy absorbers on one side of the support structure may be the same or different to the number and/or spacing of cells and/or energy absorbers on the opposite side of the support structure.

The energy absorbers and/or cells on at least one and optionally each support structure may be regularly spaced or irregularly spaced. At least one and optionally each support structure may comprise a plurality of energy absorber and/or cell spacings.

The energy conversion device may be configured or configurable such that wave fronts are incident on the longer or longest support structure(s) and/or the support structure(s) having more or most cells before one or more and optionally each shorter support structure(s) and/or support structure(s) having fewer cells. The energy conversion device may be configured or configurable such that such that the wave direction is obliquely oriented to the energy absorbers of at least one support structure, such as the longer or longest support structure(s) and/or the support structure(s) having more or most energy absorbers and/or cells.

The energy conversion apparatus may comprise one or more spacers provided between at least two and optionally each energy absorber and/or cell of at least one and optionally each support structure.

The support structures and/or joining members may comprise and/or be formed from steel, concrete, stone, plastic, polymeric material, rubber, elastomeric material, fibre reinforced material, composite materials and/or the like. The support structures and/or joining members may be formed from flat plate, space frame construction and/or the like.

At least one parameter, property or response of the energy conversion device may be selected, selectable, controllable and/or adjustable. The parameter(s), properties and/or response(s) may be actively and/or passively controllable. The energy conversion device may comprise or be configured to receive commands from a control system. The energy conversion device may comprise at least one mechanism or device for varying the property or parameter of the energy conversion device, e.g. responsive to the control system. The parameter, property or response of the energy conversion device may be selected, selectable, controllable and/or adjustable in order to control or determine the stability, orientation, wave response or other operational parameter of the energy conversion device.

Examples of suitable properties, parameters or responses that may be selected, selectable, controlled and/or adjustable include damping (which may be active and/or passive), buoyancy, mass of the energy conversion device, pressure in each or selected chambers and/or conduits and/or working fluid main, a spring constant or tension of the diaphragm, water plane area, draught, displacement, a flow resistance of the working fluid, e.g. in one or more conduits or the working fluid main, a resistance to flow of the working fluid provided by the drivable apparatus, external springs and/or tension or other configuration or parameter the mooring, and/or the like. It will be appreciated that the above list is not intended to be exhaustive and that a skilled person could readily determine alternative or additional controlled properties.

Examples of mechanisms or devices for varying the controlled property, parameter or response include variable ballast (e.g. ballast tanks that can be selectively filled and emptied, for example with water, such as by using a pump) or inflated/inflatable chambers whose inflation can be varied, variation of gearing of the drivable apparatus, active driving of the drivable apparatus by means other than the working fluid (e.g. by applying electrical current to the generator). Another example includes variation of the force applied by anchoring apparatus on the energy conversion device or vice versa. Other examples include tensioners or actuators that can act on the diaphragm and/or provision of property varying materials in the diaphragm, such as electro active polymer. Other examples include provision of valves, dampers, throttles or the like for controlling flow of the working fluid in the conduit or mains, provision of variable, movable or configurable hydrodynamic surfaces, motors or other propulsion or force generating devices and/or the like.

Again, it will be appreciated that the above list is not intended to be exhaustive and that a skilled person could determine other means for varying one or more properties, parameters or responses of the system.

The at least one property, parameter or response of the system may be controllable responsive to determined or predicted wave environments, sea state, system response or output or state, or the like. For example, the energy conversion device may store and/or to be configured to receive data from at least one sensor, such as a wave height sensor, a diaphragm strain or displacement sensor, a pressure or flow sensor for measuring the pressure or flow of the working fluid, a sensor for measuring an output of the drivable apparatus such as an electrical meter (e.g. a voltmeter, ammeter or the like), and/or the like. The control system may be configured to receive the data from the at least one sensor and/or at least one sensor of at least one other energy conversion devices and/or remote external sensors such as buoy based sensors for measuring wave height, and determined or predicted data supplied from other sources, such as from a data feed over a communication network from a remote computer system and the like.

For example, the pressure of working fluid in the working fluid main and/or individual cell chambers and/or conduits may be controllable, e.g. depending on sea state, such as increasing the pressure with increasing sea state and reducing the pressure with a reducing sea state. The control system may be configured to reduce the pressure in or deflate the chambers of at least one and optionally each cell chamber if the sea state is determined to be too high, e.g. if it exceeds a threshold, which may protect the energy absorber from damage. The pressure in a given chamber of a cell may be controllable by controlling a flow resistance imparted by a drivable apparatus associated with the respective cell.

The cells and/or energy absorbers may be positioned (e.g. spaced) for optimum phasing. The relative spacing of the cells and/or energy absorbers may be selected so that cell phasing is not destructive for a given wave length, direction and/or hull motion, for example, corresponding to expected or prevalent wave lengths, directions and hull motions. In this way, a wave hitting the energy conversion device obliquely may sequentially interact with the cells / energy absorbers on a given support structure of the energy conversion device and the cells may be positioned such that the energy absorbers are operated constructively rather than destructively.

The cross section of at least one and optionally each support structure may comprise a variable water plane area with depth, which may comprise, for example, wedge shape buoyancy.

The energy conversion device may have means for reorienting or repositioning the energy conversion device. For example, the energy conversion device may be provided with apparatus for exerting a force on the mooring or propulsion devices or the like.

The ballast and/or inflation of buoyancy or the working fluid main and/or cell chambers of the energy conversion device may be controllable. The energy conversion device may be configured such that it is deballastable and/or inflatable for transport.

The energy conversion device may be provided with transverse and/or longitudinal watertight bulkheads.

The energy conversion apparatus may comprise a mooring system. The mooring system may comprise at least one and preferably a plurality of mooring lines, for example, a six line mooring system. The mooring system may comprise suitable anchors, chain catenary and/or synthetic risers and/or the like.

The energy conversion device may be provided with one or more wind turbines, for example, at joining points between joining members and other joining members and/or a support structure and/or at joining points between support structures.

According to a second aspect of the present invention is a method of converting wave energy, the method comprising exposing an energy conversion apparatus according to the first aspect to wave or tidal motion or any other suitable action of a body of water that results in a variable pressure or force being applied to the energy absorber.

According to a third aspect of the present invention is a method of installing an energy conversion device, the method comprising immersing the energy conversion device according to the first aspect in a body of fluid.

The body of fluid may comprise a sea or lake or other body of water, for

example.

According to a fourth aspect of the present invention is a method of constructing, repairing or servicing an energy conversion device according to the first aspect, the method comprising attaching and/or removing a cassette to a support structure.

According to a fifth aspect of the present invention is a cassette. The cassette may comprise one or more of: at least one energy absorber and/or working surface; a frame and/or clamp; and/or a saddle or limiting apparatus. The cassette may comprise a removable / interchangeable cassette. The cassette may be configured for use with the energy conversion device of the first aspect or may comprise at least one feature described above in relation to the cassette in the first aspect.

According to a sixth aspect of the present invention is a support structure for supporting an energy absorber of an energy conversion device. The support structure may comprise a hull structure. The support structure may comprise or be configured to receive one or more energy absorbers. The support structure may be configured for use with the energy conversion device of the first aspect or may comprise at least one feature described above in relation to the hull structure in the first aspect Features described in relation to any of the above aspects may also be applicable to any of the other above aspects. Features described in combination in relation to any of the above aspects may be jointly or individually and seperably applicable to any other of the above aspects. Apparatus features corresponding to those described above in relation to a method and also method features corresponding to the use and fabrication of any apparatus features described above are also intended as falling within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspect of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of an energy conversion device, specifically a wave energy conversion device, in accordance with an embodiment of the present invention; Figure 2 is a plan view schematic of the wave energy conversion device of Figure 1, in use; Figure 3 is a plan cross-sectional view of the wave energy conversion device of Figure 1; Figure 4 is a plan view schematic of the wave energy conversion device of Figure 1; Figure 5a is a plan view schematic selectively showing the relative arrangements of the hull sections of an energy conversion device; Figure 5b is a perspective view schematic selectively showing the relative arrangements of the hull sections shown in Figure 5a; Figure 5c is a front elevation view of hull sections of the energy conversion device of Figure 1, without diaphragms in place; Figure Sd is a partial side cross sectional view through the section A-A shown in Figure 5b; Figure be is a side cross sectional view through the section B-B shown in Figure 5b; Figure 6 is a cross sectional view of a cell of a wave energy conversion device showing a range of motion of a diaphragm; Figure 7 is a perspective view of a cross section of a cell for use in an energy conversion device; Figure 8 is a front elevation view of a saddle for use in a cell of an energy conversion device; Figure 9a is a planar view selectively showing the relative hull arrangement in an alternative energy conversion device; Figure 9b is a perspective view selectively showing the relative hull arrangement shown in Figure 9a; Figure Yc is a front elevation view of a hull arrangement shown in Figure Ya; Figure 9d is a perspective view selectively showing the relative hull arrangement of an alternative energy conversion device; Figure 9e is a perspective view selectively showing the relative hull arrangement of an alternative energy conversion device; Figure ba is a planar view selectively showing the relative hull arrangement in an alternative energy conversion device; Figure lOb is a perspective view selectively showing the relative hull arrangement also shown in Figure 1 Oa; Figure bc is a front elevation view of a hull arrangement also shown in Figure ba; Figure lOd is a side elevation view of a hull arrangement also shown in Figure ba; Figure 11 is a planar view selectively showing the relative hull arrangement in an alternative energy conversion device; Figure 12a is a planar view selectively showing the relative hull arrangement in an alternative energy conversion device; Figure 12b is a planar view selectively showing the relative hull arrangement in an alternative energy conversion device; and Figure 13 is a perspective view showing the hull arrangement of an alternative energy conversion device.

DETAILED DESCRIPTION OF THE DRAWINGS

Figures 1 to 5 show a wave energy conversion device 5 comprising first and second linearly extending support structures 10, 15 arranged in parallel. In this embodiment, the support structures advantageously comprise hull sections.

However, it will be appreciated that other support structures could be used, such as scaffolding, harbour walls, breakwaters, parts of a vessel, etc. The hull sections 10, are joined by a plurality of joining or bracing sections 20. Each hull section 10, 15 is provided with a plurality of cells 25.

Each cell 25 comprises an air chamber 30 (see Figures Sb, Sc and Sd), wherein a side of the chamber 30 is at least partially defined by an energy absorber such as a working surface, in this case in the form of a flexible diaphragm or membrane 35. The diaphragm is sealingly held in place by a frame and clamp S arrangement 40 (see Figures Sb, Sc, 6 and 7). Each cell 25 further comprises a saddle 45 or limit apparatus (as shown in Figure7 and 8) for controlling a limit of motion of the diaphragm 35 and at least one conduit SO running between the chamber 30 and an air main 55 (see Figure 3). A drivable apparatus 60 (see Figure 3), such as a turbine driven electrical generator is provided in or attached to the conduit 50.

The air main 55 is provided in the form of a ring main that extends along and within each of the hull sections 10, 15 and through one or more of the joining or bracing sections 20 so that the parts of the air main 55 in both hull sections 10, 15 is joined and in fluid communication. However, it will be appreciated that other suitable air main arrangements can be used.

In this embodiment, the hull sections 10, 15 differ in length; with the first hull section 10 being longer and having more energy conversion cells 25 than the second hull section 15. In particular the ratio of energy conversion cells 25 and/or total diaphragm 35 surface area in the first hull section 10 to that of the second hull section 15 is advantageously substantially 3:1. However, it will be appreciated that this ratio can be selected depending on the expected conditions and performance requirements. In a specific example, six cells 25 are provided on the first hull section and two cells 25 on the second hull section 15 (i.e. a 3:1 ratio). In another possible example for use in other wave conditions, a 2:1 ratio, e.g. six cells on the first hull section and three cells on the second hull section may be used.

Although the first hull section 10 is preferably an integral hull section, it will be appreciated that the hull sections 10 and/or 15 can optionally be formed from smaller hull sections or modules 65 fixed together, as shown in Figures Sa and Sb. In this case, each of the hull section modules 65 comprises at least one cell 25 (three cells in the particular example of Figures 5a and Sb) and the hull section modules 65 are fixed together in a linearly extending arrangement to form the relevant hull section 10 and/or 15.

The diaphragms 35 on each hull section 10, 15 are provided on respective sides 70, 75 (see e.g. Figure 1) of the respective hull section 10, 15 that faces away from the other section 15, 10, i.e. the diaphragms 35 are outwardly facing with respect to the energy conversion device 5. In addition, each diaphragm 35 on a given hull section 10, iSis configured to face in the same direction or orientation.

The diaphragm 35 and the frame and clamp arrangement 40 that holds the diaphragm 35 in place (and optionally also the saddle 45) are comprised in a cassette 80 that is selectively removable and attachable to walls of the cell chamber 30. It will be appreciated that suitable seals (not shown) are provided between the cassette 80 (see e.g. Figure 1) and the cell chamber walls so as to provide a substantially air tight seal and substantially prevent or minimise water ingress. In this way, the diaphragms 35 may be quickly and easily replaced in situ by replacing the corresponding cassette 80.

Each cassette 80 is recessed into the hull 10, 15 when mounted. In particular, a floor portion 85 (see e.g. Figures 1, Sc, Sd and Se) of the chamber 30 wall extends below the frame 40 upon which the diaphragm 35 is mounted. This arrangement has been found to improve energy capture, reduce structural loads and to make the energy conversion device 5 more hydronomically efficient.

In the embodiment shown, the cassette 80 is provided substantially vertically.

However, the cassette 80 can optionally be raked, for example, at an angle up to ±20°, such as substantially ±150 from vertical.

The diaphragm 35 can be formed of any suitable material. For example, in the prior art CLAM device referenced on page 2, an elastic rubber diaphragm reinforced with steel cords was used. However, a skilled person would appreciate that other materials could be used for the diaphragm 35.

The saddle 45 is formed from welded steel, for example, but could alternatively be formed using other constructions, such as composite or polymeric material.

The hull sections 10, 15 and/or joining sections 20 could be constructed using any suitable marine structure construction technique known in the art and could comprise, for example, steel, concrete, composite materials, polymeric materials and/or the like. Suitable construction arrangements include space frame, panel construction and/or the like.

In this particular embodiment, the first hull section 10 is 11 8m long and the beam (e.g. the hull separation) is 45m. However, it will be appreciated that the energy conversion device 5 is readily scalable and that the invention is not necessarily limited to any particular dimensions. Furthermore, the aspect ratio and proportions of the energy conversion device 5 can be varied depending on the expected prevalent wave conditions to provide optimal operation of the device.

In a particular exemplary embodiment, the hulls 10, 15 are constructed from a welded steel fabrication with internal decks, transverse and longitudinal watertight bulkheads and all stiffened with primary and secondary stiffeners.

The shape and dimensions of each hull 10, 15 can be optimised for the predominant sea states with which it is to be utilised. For example, the passive hull cross-section influences the pitch response of the energy conversion device 5. In this way, suitable selection of passive hull cross-section can be used to influence the relative wave elevation at each cell 25. Optionally, the hull 10, 15 can be configured such that water plane is variable with depth or draught, e.g. through the provision of wedge shaped or tapered buoyancy (not shown). Alternatively, the hull 10, 15 can be configured to have a constant water plane with depth or draught.

The energy conversion device 5 also provides any necessary mounting and support structures for equipment, services, mooring line attachments and docking facilities of vessels and the like.

In use, the energy conversion device 5 is oriented or orientable relative to the predominant wave direction 90 in a way that is optimal for a particular site.

Specifically, the energy conversion device 5 is oriented such that incoming waves obliquely impact the diaphragms 35 of the first hull section 10 and strike the first hull section 10 before they impact the second hull section 15.

Each cell 25 in each hull section 10, 15 is spaced from the other cells 25 by a spacer 95 (see Figures 1, 3, Sb, 5c and 5e). The spacing between cells 25 can be selected such that the phasing of wave action on the cells 25 associated with the predominant wave conditions is optimised. In other words, the cells 25 can be spaced such that the cells 25 are operated constructively and not destructively for the predominant wave conditions, e.g. wave lengths and directions, and/or expected hull motions.

Each cell 25 is isolatable from the air main 55. For example, each cell 25 may be isolatable via blanking plates, valves, shutters or the like (not shown). In this way, cells 25 and cassettes 80 can be switched out in use, potentially without shutting down the energy conversion device 5, for example, for routine maintenance, in response to a diaphragm 35 or other leak or failure or simply in order to control the power and/or response of the device 5.

In the present embodiment, each cell 25 is provided with its own drivable apparatus 60 (e.g. a turbine driven generator). The device 5 can optionally be configured such that the drivable apparatus' 60 are arranged in series or parallel.

Optionally each cell 25 is arranged to react along with the other cells 25. Optionally, the drivable apparatus' 60 are also linked, for example, such that a drivable apparatus 60 experiencing a high load may pass part of the load onto a drivable apparatus 60 that is experiencing less load.

In one example, the wave energy conversion device 5 comprises eight identical drivable apparatus 60 (one for each energy conversion cell 25). The turbines of the drivable apparatus 60 are bi-directional, thereby rotating in the same direction regardless of the direction of airflow. An example of a suitable turbine is a Wells turbine, but a skilled person would appreciate that other turbines could be used. Each turbine drives an associated induction generator, such as a double-fed induction generator, the speed and voltage of which is controllable by an associated AC/DC/AC power converter. The power from each of the generators is aggregated at a lower voltage before being stepped up via a suitable step-up transformer for transmission out from the energy conversion device 5. For example, the transformer is connected to a cable to shore provided via an umbilical (not shown).

The energy conversion device 5 is also advantageously provided with appropriate balance of plant to ensure operation, such as bilge and ballast pumps, ventilation systems, air charging systems for the cell chambers, navigation aids and/or domestic services.

The energy conversion device 5 is provided with docking facilities (not shown) allowing the docking and mooring of service vessels to the energy conversion device 5. Furthermore, the energy conversion device 5 is optionally provided with wind turbines (not shown) at the strong points of the structure, such as the joints between the hull sections 10, 15 and joining members 20 and/or at junctions between joining members 20.

The wave energy conversion device 5 has both natural and variable buoyancy, provided by buoyant structures built into the energy conversion device 5 and through the buoyancy provided by the air main 55, conduits 50 and cell chambers 30. In this way, the device 5 can be floated so as to be partially immersed in a body of water 100 (see e.g. Figure 3), typically at sea, and moored via a suitable mooring system 105. Advantageously, as shown in Figure 2, the energy conversion device 5 comprises a six line mooring system 105 that comprises suitable anchors, chain catenary and synthetic risers, although it will be appreciated that other mooring arrangements could also be used.

The mooring system 105 is optionally provided with a mechanism for rotating or otherwise reorienting the energy conversion device 5, in order to provide optimal alignment to the incident waves 90.

In particular, each of the diaphragms 35 are partially immersed in the water such that changes in water pressure due to incident waves cause the diaphragm 35 to move, thereby driving/forcing air from the cell chambers 30 and/or air main 55 through the conduit(s) 50 and thereby driving the drivable apparatus 60. An example of a range of motion of a diaphragm is shown in Figure 6.

The performance of the energy conversion device 5 can be controlled, wherein such control can be active and/or passive and can be provided on a cell by cell and/or device wide basis. In an embodiment, each device 5 is controllable by a control system (not shown) that is arranged to vary the response of the energy conversion device S according to factors such as sea state, wave environments at or around the energy conversion device 5, energy demand, and the like.

For example, the drivable apparatus 60 may be controllable responsive to the control system so as to vary the damping experienced by air travelling through the associated conduit 50 caused by the drivable apparatus 60. However, it will be appreciated that other mechanisms for varying at least one response of the energy conversion device 5 may be used. For example, the cells 25 and/or air main 55 could be provided with valves, throttles, baffles or other mechanisms (not shown) for varying damping of air flow into and/or out of the cell chambers 30 and/or through the air main 55 and/or varying the air pressure in the cell chambers 30 and/or air main 55. Another example of a possible performance control mechanism comprises varying the response of the diaphragm 35, for example by providing actuators for varying the tension in the diaphragm 35 or by providing electro active material in the diaphragm 35.

Other examples of potentially controllable properties that may be used include variation of mass or spring terms of the device 5, for example, by changing the draught or displacement and/or water plane area and/or orientation of the device 5.

This can comprise, for example, provision of variable ballast, e.g. ballast tanks provided with pumps for filling/emptying or transferring a ballasting medium such as water. Additionally or alternatively, adjustable buoyancy could be used, for example, by providing selectively inflatable / deflatable buoyancy or by simply varying the pressure in the air main 55 and/or one or more cell chambers 30.

Another option for controllably varying a property of the device 5 is by providing a mechanism for adjusting the relative separation of the hulls 10, 15.

Other possible options for controlling the response of the energy conversion device 5 include movable or variable hydrodynamic surfaces, motors or other propulsion or thrust applying means and mooring based systems for selectively applying or varying a force on or from the mooring 105, in order to vary the water plane area and/or draught or displacement and/or orientation of the energy conversion device 5.

The control system may be operative responsive to the output of sensors provided within the device 5, such as inclinometers, accelerometers, pressure gauges in the cell chambers and/or air mains, flow meters in the conduits 50 and/or air mains 55, immersion depth gauges, or the like. The control system is optionally configured to receive data from external sources, such as sensors provided remotely from the energy conversion device 5, for example on buoys or other vessels or on other energy conversion devices in order to allow for predictive control based on expected or predicted sea or wave states. The control system may be configured to access remotely provided data such as from a remote server over a network, for example, from meteorological data servers, sea state data servers and the like. This data may be usable in predicting sea states.

It will be appreciated that the operation and energy production of the energy conversion apparatus may be controlled according to sea state. For example, the working pressure range of selected ones, or optionally all, of the cell chambers and/or the air main may be increased with increasing sea state and decreased with decreasing sea state. The exception to this is when the sea state is determined to be approaching an excessive or potentially damaging level, in which case, the control system may be configured to depressurise or reduce pressure in the cell chambers in order to avoid damage.

The control mechanisms may also be operable to optimise the energy conversion device 5 for certain operations. For example, the energy conversion device 5 can be deballasted and/or the buoyancy inflation pressure increased to allow for easier transportation.

The energy conversion device 5 described above can potentially realise many benefits over prior art systems. For example, it provides a number of variables that can be optimised. It will be appreciated that some parameters, such as damping, controls, ballast, trim and cell/conduit/air main pressure, can be optimised for a given design or operational condition. The energy conversion device can also me refined or modified for a given site, cross section of the hull or cell arrangement.

For instance, the number, spacing and distribution of energy conversion cells 25 can be varied to suit the expected predominant wave conditions. Similarly, the number and relative location, orientation and dimensions of the hull sections 10, 15 can be selected to suit the expected prevailing wave climates.

However, the above energy conversion device 5, having parallel spaced apart hull sections 10, 15 with differing numbers of cells 25 on each hull section 10, 15, can efficiently absorb both short crested and long crested waves from different directions.

Furthermore beneficial the power distribution amongst cells 25can be achieved, particularly for short crested seas.

This energy conversion device 5 can provide efficient energy capture across a 1800 arc. Whilst other arrangements, such as circular or dodecahedral energy conversion devices have been found to produce power over a greater arc angle, the per cell efficiency and power distribution of such systems is generally lower. It has been found that for wave energy sites exposed to large seas but close to seaboard (e.g. for proximity to grid connections and population), a high percentage of the wave energy resource falls within a 1800 arc, such that the benefits of the above energy conversion device 5 outweigh those of a circular device in such situations.

Furthermore, by providing the hull sections 10, 15 in parallel, a stable energy conversion device 5 can be produced. Providing cells 25 in both of the parallel hull sections 10, 15 has been found to improve compliance within the air system (i.e. the air main 55, conduits 50 and cell chambers 30), thereby significantly improving performance. Providing dissimilar numbers of energy conversion cells 25 or differing total diaphragm surface area between the parallel hull sections 10, 15 has been found to result in an optimal balance of energy conversion efficiency and compliance, most particularly when the relative number of energy conversion cells 25 and/or relative total diaphragm surface area is in a substantially 3:1 ratio.

Furthermore, the above energy conversion devices that has hull sections 10, that comprise linearly extending arrays of energy conversion cells 25 has been found to be more easily scalable and adaptable, and in particular is easier to optimise the device 5 for a given set of expected prevailing wave conditions at any given location.

Although the above energy conversion device 5 provides many advantages, as detailed above, it will be appreciated that the optimal configuration of energy conversion device can depend on the sea state and conditions associated with any given location as well as user operating requirements. As such, it will be appreciated that variations to the above arrangement can be made, e.g. to suit specific locations, conditions and/or requirements.

For example, although the example described above is provided with a drivable apparatus 60 for each cell 25, this need not be the case. Instead, drivable apparatus 60 may be shared between cells 25, for example by being provided centrally and/or attached to the air main 55. In addition, optionally, only selected cells 25 can be provided with drivable apparatus 60. For example, the cells 25 in the hull section that is oriented toward the prevalent wave direction, i.e. the hull section with the most cells 25 (in this case the first hull section 10), may be provided with drivable apparatus 60 but at least one and optionally each cell 25 of the leeward hull, e.g. the second hull 15, may be without drivable apparatus 60, i.e. they are dummy cells. These dummy cells can be provided mainly for compliance in the air system 30, 50, 55 and in the energy conversion device 5 as a whole.

Furthermore, although the energy conversion device 5 described above has parallel hull sections 10, 15 of differing lengths and with differing numbers of energy conversion cells 25 and/or having differing total diaphragm areas, it will be appreciated that parallel hulls 10', 15' of substantially the same length and/or having the same number of energy conversion cells 25 and/or the same total diaphragm area can be provided, as shown in Figures 9a, 9b and 9c. These figures show the relative hull arrangements 10', 15' usable in an energy conversion device 5' according to an alternative embodiment of the present invention wherein the remaining components of the wave energy conversion device 5' are substantially similar to those of the embodiment described above and have been omitted from the drawings for clarity. As can be seen from Figures 9a and 9b, it is also possible to provide one or more cells 25 on the side of 70, 75 at least one of the hulls 10', 15' that faces the other hull 15', 10', i.e. inwardly facing energy conversion cells 25'. In this case, more outwardly facing energy conversion cells 25 (in this case five) are provided on each hull section 10', 15' than inwardly facing energy conversion cells 25' (in this case one).

However, the number of inwardly facing cells 25' need not differ from the number of outwardly facing cells 20, as illustrated in Figure 9d, in which each hull section comprises 10", 15" comprises identical numbers of inwardly and outwardly facing cells 25, 25' (in this case three inwardly facing cells 25' and three outwardly facing cells 25).

Furthermore, in the examples described above, the cells 25 are evenly spaced apart. However, this need not be the case, as illustrated in Figure Ye. In this case, cells 25 are clustered together, with some cells 25 being provided immediately adjacent and some cells 25 being spaced apart, e.g. by spacers 95'. In this case, an uneven clustering of cells 25 is provided, with two spaced apart groups of cells 25 of three and two cells 25 respectively, wherein the cells 25 in each group are provided adjacent at least one other cell 25 in the group. However, it will be appreciated that even clustering of cells 25 or other variations of cell 25 spacing may also be used.

In addition, the hull sections ba, 15a need not be parallel or indeed be spaced apart. An example of this is shown in Figures lOa,lOb, bc and lOd. In this case, two linear hull sections ba, iSa are acutely oriented to each other and joined together at proximate ends to form an apex 110. The apex 110 is provided with a protective bow section. In this particular example, the acutely angled linear hull sections ba, isa are provided at 45° to each other but it will be appreciated that other acutely angled relative orientations are possible.

A further hull section lOb, 15b is attached to the distal ends of each of the obliquely angled hull sections ba, isa. These further hull sections lOb, 15b are provided parallel to each other. In this case, each of the further hull sections lOb, 15b are provided at 157.5° to the respective hull sections bOa, isa to which they are attached.

In addition, although in the above examples, each of the hull sections 10, 10', 10", bOa, lOb, 15, 15', 15", iSa, 15b are arranged to form open structured energy conversion devices 5, 5', this need not be the case. In the example shown in Figure 11, four hull sections lOw, lOx, by and lOz are connected together end to end in order to form a rhomboid configuration. It will also be appreciated that other closed form arrangements can be formed.

Another option for arranging hull sections together is shown in Figure 12a. In this case, similarly to the hull section arrangement shown in Figures 1 Oa to 1 Od, two hull sections ba', iSa' are joined together at one end to form a V-shaped configuration. Each hull section ba', iSa' is provided with outwardly facing cells 25.

In this case, the energy conversion device 5", in use, is oriented such that the apex 110' of the V points toward the prevailing wave direction 90 such that the waves impact obliquely on the diaphragms 35 of the energy conversion cells 25.

In an alternate arrangement, as shown in Figure 12b, two hull sections ba", iSa" are joined together at one end to form a V-shaped configuration but in this case, at least some, and optionally each, of the diaphragms 35 on each hull section bOa", 15a" are provided inwardly facing. In this case, in use, the apex 110" of the V is advantageously pointed away from the prevailing wave direction 90.

It will be appreciated that the hull sections need not be linear. It will also be appreciated that only one integral hull section may optionally be provided. For example, an embodiment of the present invention optionally comprises one or more of the features described previously herein but applied to a energy conversion devices having curved, arcuate, oval, round, polygon or V-shaped hull sections and/or only having a single hull section, such as a polygon arrangement of energy conversion device as shown in Figure 13 (in this case a dodecahral device). Non-limiting examples of the above features that could be jointly or individually and separably applied to these device include features relating to the cassette or diaphragm, the control systems or methods, the construction, the ballasting, inflation and/or mooring arrangements, the operating features and methods, the cell arrangement, structure and components and power take of arrangement and the arrangement of devices such as turbines, the isolation apparatus, configuration and methods, the orientation and positioning of the energy conversion device and/or the like.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the present invention. For example, although the examples described above advantageously describe a working surface in the form of a diaphragm or membrane 35, it will be appreciated that other working surfaces may also be used, such as a piston face, bellows or the like. Further, where multiple cells are used these may be arranged in any suitable form, such as linearly or on a curved surface. Also, although examples are given having specific numbers of cells 25, it will be appreciated that other numbers of cells 25 may be provided. In addition, features described in relation to any of the above embodiments may also be applicable to other embodiments. For example, embodiments having only outwardly or inwardly facing cells 25, 25' may be provided with both outwardly and inwardly facing cells 25, 25' and vice-versa. Furthermore, although various dimensions and constructional material examples are given, it will be appreciated that these are given by way of example only and the invention need not be limited to these examples. In addition, although drivable apparatus 60 that comprises a turbine and/or generator is described above, it will be appreciated that other apparatus can be driven, such as a turbine based pump or simply a body of fluid that is pumped by the motion of the membranes, and/or the like.