Abstract
A wave energy converter (WEC) 10 has a body portion 18 with a face 20 and at least one flexible membrane 16 bounding at least part of a volume of a fluid to form a variable volume cell 22. The membrane is inclined from vertical providing a flow smoothed passage for wave energy from a wave 14 to travel over the WEC whilst deforming the at least one membrane towards the body to compress the fluid. The cell(s) can be submerged or floating. The inclination of the at least one membrane assists conversion of potential and kinetic energy of the wave to pressure within the fluid. Fluid pressure within the WEC cell(s) and/or system can be optimised to suit wave and/or performance conditions.
Claims
1. A wave energy converter (WEC) for use submerged below a surface of a body of water, the WEC comprising: at least one body portion; and at least two cells, each of the cells including a flexible membrane, wherein each of said cell bounds at least part of a volume of a fluid within the respective cell, the flexible membranes being fully submerged to a depth in a body of water when in use, and wherein a portion of the at least one membrane is inclined from vertical and inclined from horizontal providing a flow smoothed way for wave energy to travel over the submerged said at least one membrane whilst a pressure differential between a wave pressure external to the respective cell and an internal pressure of the respective cell deforms each of the flexible membranes towards the body to compress the volume of the fluid, wherein the inclination of the substantial portion of the at least one membrane from vertical and horizontal assists coupling conversion of potential and kinetic energy of the wave to pressure within the fluid as the wave energy passes over the submerged WEC, and wherein at least two of the cells supplies pressure into a pressure supply conduit or manifold through a respective at least one supply port of each of those cells.
2. The WEC according to claim 1, further comprising the at least two cells arranged in at least one array forming a multiple cell said wave energy convertor.
3. The WEC according to claim 1, wherein the WEC includes the at least two cells within one said body portion.
4. The WEC according to claim 1, wherein the at least one flexible membrane is inclined between 20° and 70° from horizontal.
5. The WEC according to claim 1, wherein a substantial portion of one or more of the at least two cells incline from horizontal with respect to a said wave passing over the WEC or declines from horizontal with respect to said wave passing over the WEC.
6. The WEC according to claim 1, wherein the submerged wave energy converter comprises the at least two cells tethered, anchored or attached to a seabed or otherwise restrained to restrict the vertical movement of the submerged WEC as the wave passes over the WEC.
7. The WEC according to claim 6, wherein the at least two cells are spaced above the seabed and tethered, anchored or attached thereto or otherwise restrained to restrict the vertical movement of the WEC as the wave passes over the submerged WEC.
8. The WEC according to claim 6, wherein the at least two cells of the WEC are submerged at between 2.5 m and 15 m of water depth on average.
9. The WEC according to claim 1, further comprising a rear of the WEC including an exterior wave flow control having a straight, curved or rounded portion.
10. The WEC according to claim 2, wherein the at least two cells are arranged as one or more linear, curved or circular arrays of said cells.
11. The WEC according to claim 2, wherein at least two cells of the WEC are arranged horizontally with respect to one another.
12. The WEC according to claim 2, deployed as multiple linear or curved arrays of said cells arranged in at least one V or chevron orientated, in use, towards or to face the direction of the oncoming waves or the open sea/ocean and the linear or curved arrays of the V or chevron extend from the apex towards the shore such that the waves approach the apex first and the V or chevron and each array obliquely, or deployed such that an apex of the V or chevron arrangement points towards the shore and away from the waves, such that the linear or curved arrays of the V protect away from the apex towards open water.
13. The WEC according to claim 2, wherein, for the at least one array of said cells, the flexible membranes are spaced so as to couple to different parts of a wavelength of the wave.
14. The WEC according to claim 13, wherein the flexible membrane of at least one said cell is exposed to higher wave pressure, and the flexible membrane of at least another said cell is exposed to lower wave pressure as one or more waves pass over the cell.
15. The WEC according to claim 14, wherein the array is arranged such that when at least one said cell is exposed to the higher wave pressure and pumping fluid out from the cell via at least one outlet port, at least one other of the cells is exposed to the lower wave pressure and accepting return fluid from a reservoir or low pressure manifold via at least one inlet port.
16. The WEC according to claim 1, further comprising one or more cell lower pressure inlet ports, one or more cell higher pressure outlet ports, one or more manifolds for combining or splitting fluid flow respectively to or from said cell(s), and/or one or more turbines driven by the pressure flow from the cell(s).
17. The WEC according to claim 10, wherein, when multiple said cells are arranged in at least one array, with at least one turbine and/or at least one electrical generator mounted toward or at the end of the array or of each said array or anywhere along a length of a said array, or wherein, when multiple said cells are arranged in a V or chevron of multiple arrays of the cells, the turbine or turbines and/or electrical generator or generators is/are mounted adjacent to or in an apex of the V or chevron and airflow streams from each array are combined.
18. The WEC according to claim 16, further comprising a fluid flow control system having at least one check valve or at least one turbine, or a combination of at least one check valve and at least one turbine, provided at or adjacent a port of a respective cell, or provided in one or more conduits, optionally in either or both a low pressure and a high pressure conduit.
19. The WEC according to claim 2, wherein at least one of the at least two cells is on each of opposing sides of the WEC, at least one said cell on a first side. with respect to the wave to extract energy from the wave, and at least. one other said cell to extract energy from the same wave and/or from a returning said wave.
20. The WEC according to claim 2, wherein at least one said array includes a longitudinal array of the cells arranged such that an angle. that the waves impinge on the array is between 10° and 80°.
21. The WEC according to claim 1, wherein the geometric shape of the at least one end of the. at least one membrane of the WEC is geometrically shaped to control elastomeric strain or stress or stress and strain.
22. The WEC according to claim 21, wherein the geometric shape of the at least one end of the flexible membrane is a curve, semicircle, arc or spline.
23. The WEC according to claim 1, wherein, at least one said flexible membrane has chord dimensions allowing the respective membrane to conform to a face of the respective cell when deflated.
24. The WEC according to claim 4, wherein each of the multiple flexible membranes is inclined between 20° and 70° from horizontal.
25. The WEC according to claim 5, wherein each of the cells of the WEC inclines from horizontal with respect to a said wave passing over the WEC or declines from horizontal with respect to said wave passing over the WEC.
26. The WEC according to claim 2, Wherein the cells of the WEC are deployed at between 2.5 m and 15 m of water depth on average.
27. The WEC according to claim 2, further comprising one or more cell lower pressure inlet ports, one or more cell higher pressure outlet ports, one or more manifolds for combining or splitting fluid flow respectively to or from said cells, and/or one or more turbines driven by the pressure flow from the cells.
28. The WEC according to claim 27, further comprising a fluid flow control system having at least one check valve or at least one turbine, or a combination of at least one check valve and at least one turbine, provided at or adjacent a port of a respective cell, or provided in one or more conduits, optionally in either or both a low pressure and a high pressure conduit.
29. The WEC according to claim 1, Wherein the flexible membrane of a respective said cell is multi-layered or laminated.
30. The WEC according to claim 1, Wherein the flexible membrane of a respective said cell incorporates reinforcement.
31. A method of controlling or optimising fluid pressure within a submerged wave energy convertor (WEC) according to claim 1, the WEC having a control system, the method comprising: increasing or decreasing fluid pressure within the cells of the submerged WEC and/or within at least one low pressure or high pressure conduit and/or within at least one manifold of the system to maintain a desired pressure.
32. The method according to claim 31, further comprising operating the control system, wherein operating the control system comprises increasing or decreasing the fluid pressure within at least one low pressure or high pressure conduit and/or within at least one manifold of the WEC relative to at least one reference pressure value.
33. The method according to claim 32, whereby the fluid pressure or each fluid pressure is an average of fluid pressure determined within each respective said cell.
34. The method according to claim 33, whereby the average pressure is determined, at least in part, by averaging various pressures within a cell or across a number of cells of the WEC at a particular time or across one or more said cells over time.
35. The method according to claims 31, further comprising controlling or optimising fluid pressure within the cells to maintain optimum fluid pressure within the cells as a function of water depth changes with tidal or other effects.
36. The method according to claim 35, Whereby fluid pressure within each respective cell of the cells is increased with an increase in water depth to balance the increased external pressure from the water, and as water depth decreases, fluid pressure within the respective cell of the cells is decreased to balance the decreased pressure from the water.
37. The method according to claim 35, further comprising, in the event of actual or predicted deterioration in sea conditions, reducing the fluid pressure within the cell to prevent damage to the membrane of the respective cell.
38. A WEC according to claim 1, wherein, at least one said flexible membrane has dimensions allowing the respective membrane to conform to a face of the respective cell when deflated or to deflate without pinches or folds in the flexible membrane.
39. The WEC according to claim 1, wherein the WEC includes each cell of the at least two cells within a single body portion separate from the body portion of each the other ones of the at least two cells.
40. The WEC according to claim 39, wherein the body portion of each of the at least two cells is spaced from the body portion of each of the other of the at least two cells.
41. The method of claim 32, whereby the fluid pressure or each fluid pressure is an average of fluid pressure determined within the at least one low pressure conduit and/or within the at least one high pressure conduit and/or manifold of the system.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIGS. 1a to 1k show, in sequential steps, wave action on the membrane for a fully swept cell volume over a complete wave sequence for a WEC according to an embodiment of the present invention.
(2) FIGS. 1m to 1w show, in sequential steps, wave action on the membrane for a fully swept cell volume over a complete wave sequence for a WEC, and showing representations of wave flow lines, according to an embodiment of the present invention.
(3) FIGS. 1l and 1x show a WEC according to an embodiment of the present invention with the membrane completely deflated.
(4) FIGS. 2a to 2k show in sequential steps wave action on the membrane for a half swept cell volume over a complete wave sequence for a WEC according to an embodiment of the present invention.
(5) FIG. 2l shows a membrane of a WEC according to an embodiment of the present invention, the membrane completely deflated.
(6) FIGS. 3 and 4 show alternative mounting arrangements of wave energy converters (WECs) according to embodiments of the present invention.
(7) FIG. 5 shows a cross section through a WEC with a single radius curvature cell face according to an embodiment of the present invention.
(8) FIGS. 6a to 6d show various arrangements for a dual radius curvature cell face according to alternative embodiments of the present invention.
(9) FIGS. 7a to 7c show various arrangements for a triple radius curvature cell face according to alternative embodiments of the present invention.
(10) FIGS. 8a to 8d show alternative arrangements of WEC with different chord angle alignments in respect of oncoming waves, according to alternative embodiments of the present invention.
(11) FIGS. 9a to 9d show alternative mooring/anchoring arrangements according to embodiments of the present invention.
(12) FIGS. 10a to 10c show sections through alternative forms of WEC according to embodiments of the present invention.
(13) FIGS. 11a to 11d show sections through alternative forms of WEC and including at least one valving or porting option according to embodiments of the present invention.
(14) FIGS. 12a and 12b show an alternative valving or porting option for a WEC according to an embodiment of the present invention and a close coupled turbine adjacent the cell according to an embodiment of the present invention.
(15) FIGS. 13a and 13b show a multi cell WEC and membrane positions according to an embodiment of the present invention.
(16) FIGS. 14a to 14c show a single cell longitudinal bank form of WEC according to an embodiment of the present invention.
(17) FIGS. 15a to 15c show a multi cell longitudinal bank form of WEC with integrated flexible divider walls according to an embodiment of the present invention.
(18) FIGS. 16a to 16c show a multi cell longitudinal bank form of WEC with diaphragm cell dividers according to an embodiment of the present invention.
(19) FIGS. 17a to 17c show a multi cell longitudinal bank form of WEC with fixed divider walls between adjacent discrete cells according to an embodiment of the present invention and consistent with FIGS. 13a and 13b.
(20) FIG. 18 shows a section through a WEC showing a valving arrangement according to an embodiment of the present invention.
(21) FIG. 19 shows a V or chevron configuration of two linear arrays or banks of multi cells forming a combined WEC arrangement according to an embodiment of the present invention.
(22) FIG. 20 is a perspective of V or chevron configuration of two linear arrays or banks of multi cells forming a combined WEC arrangement according to an embodiment of the present invention.
(23) FIGS. 21 to 23 show cell membrane displacement sequences with respect to an impinging wave according to embodiments of the present invention.
(24) FIGS. 24 to 26 show various arrangements of linear array or bank configurations of WEC for near shore application according to embodiments of the present invention.
(25) FIGS. 27 to 29 show various linear array or bank forms corresponding to the respective arrangements shown in FIGS. 24 to 26.
(26) FIGS. 30 and 31 show deep water applications of the WEC according to embodiments of the present invention, with FIGS. 30s and 31s showing respective cross sections.
(27) FIGS. 30a, 30b, 30c and 30d show alternative deep water applications of WECs according to embodiments of the present invention. FIG. 30a shows a wind turbine mounted on a floating WEC. FIG. 30b shows a seabed/seafloor mounted submerged version with wind turbine tower projecting upwards therefrom. FIGS. 30c and 30d show an alternative embodiment of a WEC and wind turbine combination according to a further embodiment of the present invention.
(28) FIGS. 32 to 34 show breakwater and oscillating water column (OWC) applications of WECs according to embodiments of the present invention.
(29) FIGS. 35 and 36 show an alternative embodiment of the breakwater WEC of FIGS. 32 and 33.
(30) FIG. 37 shows a coffer dam type breakwater application incorporating a WEC according to an embodiment of the present invention.
(31) FIGS. 38 to 42 show alternative forms of a WEC according to embodiments of the present invention.
(32) FIGS. 43 to 46 show various arrangements of process, piping and instrumentation of systems for controlling flow of a secondary fluid from one or more cells of WECs through one or more turbines to convert wave energy to harnessed energy according to embodiments of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
(33) FIGS. 1a to 1k show a wave energy converter (WEC) 10 on a seabed or sea floor 12, resting on the seabed under its own weight. The sequential steps show the action of a wave 14 on a flexible membrane 16 of the WEC over a complete wave sequence for a WEC according to an embodiment of the present invention. The wave has a peak 14a and trough 14b. The WEC has a body 18 with an integral face 20. It will be appreciated that the face can be separately applied to the body, such as a discrete face member. The face member and membrane may be pre attached to each before mounting to the body. Alternatively, the membrane may be connected to the body by other attachment means. The membrane and face are sealed watertight with respect to the exterior wave such that they define a variable volume cell 22 therebetween. The volume of that cell is increased by a pressurised supply of a fluid within the WEC sufficient to resist pressure of the wave at a trough 14b in the wave form so that the membrane inflates and is under tension. As the wave peak 14a approaches and passes over the WEC (FIGS. 1a to 1f), surge and heave pressure within the wave increases and the membrane is compressed towards the face, normally from a lower forward portion, such that the cell volume is compressed and fluid within the cell is squeezed upwards gradually progressing rearward and upward with respect to the cell's rearward and upward inclination.
(34) FIGS. 1m to 1w show the same operation of the WEC 10 as shown in FIGS. 1a to 1k, though including wave flow lines. These wave flow lines represent the general flow and movement of the wave over the WEC 10. It will be appreciated that the membrane 16 begins deforming before the peak 14a of the wave 14 is directly above the WEC 10. This is due to the pressure front leading the wave as the wave peak 14a approaches the WEC.
(35) It will be appreciated that the cell in this embodiment is inclined or angled rearward with a lower portion forward of its upper portion such that the lower portion encounters the force of the wave first and the wave pressure progresses rearward thereby forcing the cell volume to constrict from the lower portion towards to upper portion.
(36) It will also be appreciated that due to the fluid nature of the energy in the wave and the flexible nature of the membrane, the membrane may not be compressed evenly and orderly, yet the volume within will still be generally compressed from the lower portion to the upper portion. The face 20 is generally the same length and width as the membrane and a length, curvature or shape generally matching but opposite to the length, curvature or shape of the membrane when the membrane is at a fully inflated state (see FIG. 1a). When the membrane is fully compressed to the face, as in FIG. 1f, the membrane lies flat against the face. As the wave continues to pass over the WEC (see FIGS. 1g to 1k) and pressure decreases on the membrane (i.e. the peak of the wave 14a has passed), return pressure re-inflates the membrane from the upper rearward portion progressing down to the lower forward portion ready for the next wave.
(37) FIGS. 1l and 1x show the membrane fully retracted or pressed back onto the face. This allows the membrane to be kept safe in the event of rough sea conditions, tidal surges or large waves that might otherwise over pressure the cells or cause damage to the membrane, or even potentially shift the WEC from its anchorage. This feature allows the WEC to be de-energised from the wave resource in the event of a WEC component failure to prevent further damage to the faulted component or associated components. This feature allows the WEC to be de-energised to enables maintenance activities to be undertaken safely.
(38) FIGS. 2a to 2k show in sequential steps wave action on the membrane for a half swept cell volume (c/w FIGS. 1a to 1k and 1m to 1w) over a complete wave sequence for a WEC according to an embodiment of the present invention.
(39) FIGS. 3 and 4 show a WEC 10 and some alternative mounting and configuration arrangements therefore according to embodiments of the present invention. The WEC 10 has a body 18. A cell volume 22 is formed by a membrane 16 and a cell face 20. The WEC forms a generally wedge shaped or streamlined aerofoil shape. In cross section, the WEC is lower in height at the front 24 than at the rear 26 with respect to impinging waves in direction W.
(40) In FIG. 3, the WEC is anchored in sand or concrete 28 to the seabed 12. The WEC has supply (outlet) 30 and return 32 conduits each connected by respective supply (outlet) 34 and return (inlet) 36 ports communicating with the cell volume 22.
(41) Valving can be provided to control flow into the supply conduit and out of the return conduit with respect to the cell. A single port may be provided with fluid flow from the cell to the supply conduit and return from the return conduit into the cell. A pair of one way valves may be provided. Alternatively a bi-directional turbine may be provided to harness the fluid flow in both directions. In this configuration, a rear face 38 of the WEC and an upper rear corbel 40 help to control return wave RW flow back over the WEC. It will be appreciated that the curve of the membrane 16 when fully inflated and the curve of the face 20 can share a common length 42 such that the membrane lies comfortably over the face when fully deflated.
(42) FIG. 4 shows the WEC 10 mounted on piers 42 raising the WEC from the seabed bathymetry conditions so that the device is levelled and closer to the mean still water level. The piers help the WEC to sit at the correct depth in the water to meet with required specification and performance criteria from the WEC in relation to the depth of water and general wave conditions.
(43) FIG. 5 shows a cross section through a WEC 10 of the present invention with a single radius curvature cell face 20. A chord 42 is common to the membrane 16 and face 20 such that the membrane can lie flat against the face when fully deflated or pressed back onto the face. Thus, each of the sections 16a, 16b, 20a,20b are of the same general length.
(44) FIGS. 6a to 6d show various arrangements for a dual radius curvature cell face 20 according to alternative embodiments of the present invention. The cell face has a first curved portion 44 and a second curved portion 46. The membrane has a section length equivalent to the length of the combined first and second curved portions.
(45) FIGS. 7a to 7c show various arrangements for a triple radius curvature 44, 46, 48 cell face 20 according to alternative embodiments of the present invention.
(46) FIGS. 8a to 8d show alternative arrangements of WEC with different chord angle 42 alignments at 90°, 45°, 30° and 0° in respect of oncoming waves W, according to alternative embodiments of the present invention. It will be appreciated that other angle alignments can be used, which can be selected based on the style of WEC deployed and prevailing location (direction, water depth etc) and wave conditions.
(47) FIGS. 9a to 9d show alternative mooring/anchoring arrangements according to embodiments of the WEC 10 of the present invention.
(48) FIG. 9a shows seabed anchored 50 version, for example, using concrete, sand, geotextile bags or rocks, or combinations thereof. FIG. 9b shows a footing or pile 52 mounted version.
(49) FIG. 9c shows a footing or pile mounted version whereby the WEC is pivotably attached 54 to the pile/footing towards the front of the WEC. This allows the WEC to be hinged forward to adapt to changes in prevailing wave conditions by altering the angle β to tilt the WEC forward. Variable ballast may be employed to control lift or lowering of the WEC about the pivot 54. The ballast can be water, such as seawater pumped into or evacuated out of a chamber or conduit through the WEC.
(50) An alternative version shown in FIG. 9d has a tethered mooring using a tether 58 attached to a tether point 60 at one end and a mooring 62 at the other. In such an arrangement, the WEC can be ballasted so as to be buoyant within the water, preferably neutrally buoyant at a preferred depth. This can be achieved by controlling the variable ballast 56.
(51) FIGS. 10a to 10c show sections through alternative forms of WEC according to embodiments of the present invention. FIG. 10a shows a convex curved rear version, FIG. 10b shows a sloping rear version and 10c a concave or corbelled version, FIG. 10d a convex version. The different versions of rear are provided for different wave and location requirements. The various rear options act to modify return wave flow and thereby can be used to maximise WEC efficiency for a given application and location.
(52) FIGS. 11a to 11d show sections through alternative forms of WEC and including at least one valving option according to embodiments of the present invention.
(53) FIG. 11a shows dual or twin ports or ducts. An outlet or supply conduit 64 and an inlet or return conduit 66 are provided. The cell volume 22 communicates with the conduits via one or more ports to/from the cell volume and valving 68. The valving shown in figure 11b has alternate one way valves 70,72. The uppermost valves 70 supply fluid from the cell volume to the supply conduit. The lower valves 72 return fluid to the cell volume from the return conduit. Sections A-A and B-B are shown respectively in FIGS. 11c and 11d. These show the outlet port(s) 74 from the cell and the inlet port(s) 76 to the cell volume.
(54) FIGS. 12a and 12b show an alternative valving option for a WEC according to an embodiment of the present invention. A bi-directional turbine 80 is provided in a single port 82.
(55) FIG. 12b shows a view into the port and the turbine from the cell volume.
(56) FIGS. 13a and 13b show a multi cell WEC and membrane positions according to an embodiment of the present invention. A bank or array of WEC cells is provided as a single unit. A single body 18 houses multiple cells. It will be appreciated that each cell may be formed or cast in the single body, or discrete cell body portions may be formed and then connected together to form the single body. The supply and return conduits 64, 66 may be integral to the body portion(s) or may run externally of the WEC in individual conduits in the form of pipes.
(57) FIG. 13b shows part of the section A-A of FIG. 13a, with the left-hand membrane partially compressed, the centre membrane fully inflated and the right-hand membrane completely deflated.
(58) FIGS. 14a to 14c show a single cell longitudinal bank form of WEC according to an embodiment of the present invention. The single cell clearly has no divider walls.
(59) FIGS. 15a to 15c show a multi cell longitudinal bank form of WEC with integrated flexible divider walls 84 according to an embodiment of the present invention. The divider walls between cells are shared between adjacent cells i.e. one cell wall between each adjacent pair of cells.
(60) FIGS. 16a to 16c show a multi cell longitudinal bank form of WEC with diaphragm cell dividers according to an embodiment of the present invention. Thus, each cell is a discrete thing having its own walls and membrane. FIGS. 17a to 17c show a multi cell longitudinal bank form of WEC with fixed, preferably rigid, divider walls between adjacent discrete cells, each with its own membrane, according to an embodiment of the present invention.
(61) FIG. 18 shows a section through a WEC showing a porting and valving arrangement according to an embodiment of the present invention. The WEC 10 includes a body portion 18 with integral conduits 64, 66 for respective supply and return flow of fluid. Flow from the cell volume 22 is through an outlet port 74 through the valving 68 into the supply conduit 64. return flow is from the return conduit 66 via the valving 68 into the cell volume 22. The valving includes separate outlet valves and return one way valves. The valving can be provided as a cartridge component that is replaceable. Preferably the valving is accessible by removing an access port cover at a rear of the WEC 10 and preferably in-line with the axis of the valving 68. The valving 68 is released and then withdrawn rearward and upward. The replacement valving is then is inserted in a downward and forward motion, then locked in location and the access port cover reinstated. The face and/or the membrane may seal to the body in a watertight or near watertight manner sufficient to allow efficient operation of the WEC with minimal leakage into or out of the conduits.
(62) The wedge shaped profile of the WEC 10 encourages the wave to ramp up on approach to the WEC and then ride over the WEC with minimal disturbance whilst maximising wave surge to wave heave conversion and thereby maximising wave energy conversion as the membrane compresses.
(63) FIG. 19 shows a V or chevron configuration of two linear arrays or banks of multi cells forming a combined WEC arrangement according to an embodiment of the present invention. Angle γ between the two limbs (arms/legs) 10a,10b of the WEC can be set at a desired value such that the arms/legs are angled with respect to each other to suit prevailing location and wave needs. The angle may be variable, such as by powered or manual adjustment between the two limbs. Power generation and/or pumping equipment and/or angle adjustment equipment may be provided at the juncture 90 between the two limbs.
(64) FIG. 20 is a perspective of V or chevron configuration of two linear arrays or banks of multi cells forming a combined WEC arrangement according to an embodiment of the present invention.
(65) FIGS. 21 to 22 show cell membrane displacement sequences with respect to an impinging wave according to embodiments of the present invention. The upper graph A for each figure represents wave height and pressure. The lower graph B for each figure represents cell vertical displacement of the membrane of each cell. Each figure also shows a representation of the pattern of actual cell membrane displacement for each sequence across the WEC limb 10a.
(66) FIGS. 24 to 26 show various arrangements of linear array or bank configurations of WEC for near shore application according to embodiments of the present invention.
(67) FIG. 24 shows a near shore ocean facing apex with the limbs pointing towards the shore. FIG. 25 shows a near shore, shore facing apex with the limbs of the WEC pointing towards open water.
(68) FIG. 26 shows a single limb or spine version of the WEC near shore.
(69) FIGS. 27 to 29 show various linear and non linear array or bank forms corresponding to the respective arrangements shown in FIGS. 24 to 26.
(70) FIGS. 30 and 31 show deep water applications of the WEC 10 according to embodiments of the present invention. In FIG. 30, the annular array 90 of cells 22 of the WEC 10 allows for efficient conversion of wave energy from any direction. Thus, wave energy conversion over a period for different wave directions over a period of time can be averaged. Section A-A (FIG. 30s—‘s’ for section) of FIG. 30 shows a cross section of a general arrangement of the cells.
(71) FIG. 31 shows an alternative embodiment of the deep water version of WEC with some cells internal to the opening through the annulus and other cells external to the opening. Section B-B (FIG. 31s—‘s’ for section) shows a cross section of a general arrangement of the cells.
(72) The WEC embodiments in FIGS. 30 and 31 extract energy from waves first impinging on one side of the annulus to also extract energy from the wave as it passes across the annuls and impinges on the inside face of the annulus. Such deep water applications may be tethered floating applications either on the surface of the waves or neutrally buoyant below the surface of the waves, or rigidly mounted on a pylon, offshore wind turbine tower, oil or gas rig or other similar ocean or deep water device.
(73) FIGS. 30a and 30b show alternative deep water applications of WECs according to embodiments of the present invention. FIG. 30a shows a wind turbine 114 integrated with a floating WEC similar to that shown in FIG. 30, though with a central (cruciform) support 110 for the mast 112 of a wind turbine 114. Other forms of support for the wind turbine, or other device, can be provided, such as a central single spar, a solid or mesh platform, or a framework. The WEC is tethered 116 to the seabed, allowing the WEC to float but not drift away. Electricity generated by the wind turbine may be used to power electrical equipment, such as pumps and control systems and safety systems relating to the WEC.
(74) FIG. 30b shows an alternative version providing a seabed/seafloor mounted submerged WEC 120 with a wind turbine mast 122 projecting upwards therefrom. The WEC is mounted on supports 124 into the seabed/seafloor 126. The WEC may move up and down with respect to the seabed/seafloor to cater for changes in water depth and sea conditions, which allows the WEC to be optimised for prevailing sea/weather conditions, or to be lowered to the seabed/seafloor in the event of rough sea/weather conditions. A cruciform support 110 supports the mast, which itself can be braced by lateral supports 126.
(75) FIGS. 30c and 30d show a deepwater application of a WEC according to an embodiment of the present invention. The WEC 10 is mounted to the mast 112a of the wind turbine 114a. In particular, FIG. 30d shows a vertical section E-E through the WEC 10 and mast 112a of the wind turbine 114a. The mast is embedded in the seabed/seafloor 12. The WEC is rotatable about the mast. Control of rotation can be effected by a winch 190 connected to each end of the WEC by one or more tethers 192,194. A single continuous tether (continuous tether 192+194) may pass around the winch pulley 190, or separate tethers may be provided 192, 194, each controlled to effectively lengthen or shorten to allow the WEC to rotate. This allows the WEC to be swung to face the prevailing oncoming waves to maximise wave energy conversion, or to be angled to control how much effect the waves have on the WEC i.e. to limit energy conversion, which can be especially useful in strong wave conditions when facing waves full on may be less than fully efficient due to the frequency, peak to trough height or forces from the waves. To allow for changes in water depth and/or wave height with respect to the mast, the WEC may travel up and down with respect to the mast. One or more guides, such as tracks, guide wheels, rollers etc. 198 may be provided on the mast, on the WEC or both. These allow the WEC to travel freely up and down or to be controlled to maintain a required position or depth.
(76) FIGS. 32 to 34 show breakwater applications of WECs according to embodiments of the present invention. The WEC 10 is provided as a linear array or bank of cells positioned close to shore and forming an edge of a jetty 96 extending out into the water 14. The jetty may be a solid or near solid breakwater.
(77) FIG. 33 shows cross section C-C through a breakwater and WEC 10.
(78) A WEC 10 adapted for harsh conditions may be provided, as shown in FIG. 34. The WEC includes one or multiple cells 22 with respective one or more membranes 16. A single port 98 leads to a bi-directional turbine 100 and into an upper single supply and return conduit or chamber 102. A lower chamber 104 can be filled with ballast, such as water or concrete or rubble for additional weight to prevent the WEC moving in rough sea or tidal surge conditions. It will be appreciated that separate supply and return conduits may be provided, with associated one way valving.
(79) As shown by way of example in FIGS. 38 to 40, the wave energy converter 10 may have alternative forms of rear wall arranged to direct return flow 142 of water. For example, FIG. 38 shows a double curved or ‘S’ shaped rear 130, whereas FIG. 39 shows a concave rear 132, and FIG. 40 a straight (or wedge or ‘triangular’ when referring to the general body shape of the WEC 10) shaped rear 134. These alternative forms of rear can be employed when a convex curved rear might result in eddy currents immediately at the base of the rear adjacent the seabed/seafloor. Such eddy currents 140 from the return flow 142 might potentially cause erosion of the seafloor 14 adjacent the rear of the WEC, as shown in FIG. 41.
(80) FIG. 42 gives an example of a WEC with a convex rear 136 and that is raised off the seafloor a distance ‘d’ to allow some of the return flow to pass under the WEC and thereby avoid such eroding eddy currents.
(81) FIGS. 43 to 46 show alternative arrangements of process and instrumentation diagrams (P&ID) of the circuits for directing the converted wave energy via a secondary fluid through one or more turbines. In particular, FIG. 43 shows a double diaphragm bank of cells 144,146 with common manifolds 148, 150 and a single (shared) turbine 152. This arrangement can be used in a V bank configuration with closed lop dual pneumatic circuit (rectified flow) and a single axial turbine coupled to an electric generator.
(82) FIG. 44 shows a double diaphragm bank of cells 154,156 but with cross flow manifolds 158, 160, each connected to a respective one of a pair of turbines 162, 164. This also relates to a V configuration of banks of cells, with closed loop dual pneumatic circuit (rectified flow) and dual axial turbines coupled to electric generators.
(83) FIG. 45 provides an arrangement of WEC with a single diaphragm bank of cells 166, 168 with cross flow manifold 170, 172 and double turbines 174, 176. This single bank arrangement has closed loop dual pneumatic circuit cross flow (rectified flow) and dual axial turbines coupled to electric generators.
(84) FIG. 46 shows a single diaphragm bank of cells 178 with single manifold 180 and bi-directional turbines 182. This provides open loop ducting (applicable to all configurations). A rectifying turbine and generator are mounted in the port between diaphragm cell and common transfer manifold. Multiple turbines per diaphragm cell is also possible.
(85) It will be appreciated that performance of the wave energy convertor cell(s) and or system can be controlled or optimised to suit prevailing or predicted sea conditions or to match a required level of performance or demand.
(86) Fluid pressure within one or more of the cells, or within the system including the cell(s), can be increased or decreased as required. For example, fluid pressure within a low pressure or high pressure conduit(s) and/or manifold of the system can be varied.
(87) Preferably the fluid pressure is increased or decreased relative to at least one reference pressure value. Fluid pressure can be determined by readings from one or more pressure sensors within the cell(s) and/or conduits and/or manifold of the system. Such pressure sensors can provide pressure related signals to a processor to determine required pressure values, and therefrom be used as a factor to control or optimise the fluid pressure.
(88) The or each reference pressure value can be an average of fluid pressure determined within the or each respective said cell and/or within the low and/or high pressure conduit(s) and/or manifold of the system.
(89) Average pressure may be determined, at least in part, by averaging various pressures within a cell or across a number of cells at a particular time (simultaneous average pressure) or across one or more cells over time (temporal averaging).
(90) Preferably the method includes controlling or optimising pressure within the cell(s) to maintain optimum cell pressure as a function of water depth changes with tidal or other longer term effects, and preferably depending on the optimal conditions for the prevailing or current sea state. Thus, as effective water depth increases above the cell(s), pressure within the cell(s) may be increased to balance the increased external pressure from the water, and as water depth decreases, pressure within the cell(s) may be decreased to balance the decreased pressure from the water. In this way, performance and output from the cell(s) and/or system may be optimised for a required output or demand on the system.
(91) Also, in the event of actual or predicted deterioration in sea conditions, pressure within the cell(s) may be reduced to prevent damage to the membrane. Pressure can, if required, be reduced to zero or atmospheric pressure such that the membrane(s) is/are pushed flat by water pressure and do not function until the cell(s) is/are internally pressurised to reinflate the cell(s).
