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Title:
MULTI-CAPTURE-MODE WAVE ENERGY CONVERTER WITH BROAD BEAM FLOAT AND SEA BED REACTION MASS
Document Type and Number:
WIPO Patent Application WO/2019/217485
Kind Code:
A1
Abstract:
A wave energy converter (WEC) utilizing one or more adjacent surface floats together forming a wide or broad beam float, with its port to starboard width substantially exceeding its fore to aft dimension. The broad-beam float being preoriented or self-orienting parallel to prevailing oncoming wave fronts. The float serving as the WEC's primary reaction body, the motion of which is constrained to being driven upward and rearward by oncoming wave crests and returning downward and forward on ensuing wave troughs. The float's upward and rearward motion capturing both heave and surge wave energy. The float wave induced motion being resisted by at least one forward power take-off (PTO) located between the float and a seabed attachment forward of the float's center of buoyancy, the seabed attachment serving as the WEC's forward second reaction body and at least one aft PTO located between a second aft seabed attachment or aft reaction body or suspended mass located under or aft of the float's center of buoyancy.

Inventors:
ROHRER, John, W. (5 Long Cove Road, York, ME, 03909, US)
Application Number:
US2019/031212
Publication Date:
November 14, 2019
Filing Date:
May 07, 2019
Export Citation:
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Assignee:
ROHRER TECHNOLOGIES, INC. (5 Long Cove Road, York, ME, 03909, US)
International Classes:
B63B39/00; F03B13/10; F03B13/12; F03B13/14; H02K7/00
Foreign References:
US20140097617A12014-04-10
US20100259047A12010-10-14
US9140231B12015-09-22
Attorney, Agent or Firm:
LORUSSO, Mark D. (LORUSSO & ASSOCIATES, P.O. Box 21915Portsmouth, NH, 02802, US)
Download PDF:
Claims:
1. A wave energy conversion devise comprising; at least one wide-beam float having a wave impacting forward face a float bottom and a float aft wall, wherein a horizontal port-to-starboard width of the face, alone or in combination with attached adjacent float faces, is greater than the float fore-to-aft depth measured by excluding any attachments, extensions, or

appendages; one fore tensioned cable or leg or member attached to the float at a position forward of the float’s center of buoyancy and inclined at a downward angle and directly or indirectly connected to the seabed at a single fixed rotatable position substantially forward or up-sea of the float center of buoyancy; at least one aft tensioned cable or leg or member attached to the float at a position substantially aft of the entry position of the fore tensioned cable and either movably connected to the seabed such that its seabed connection point is free to move laterally along a prescribed path on, or near, the seabed and substantially under or aft of the float’s center of buoyancy, or the aft cable is connected to at least one suspended ballast or counter-weight or drag plate substantially under or aft of the float’s center of buoyancy, wherein the fore cable’s fixed seabed position and the aft cable’s laterally movable position combined with the fore and aft cable float- connecting positions maintain the travel line of the float and the fore and aft cables, when viewed from above, substantially normal to oncoming wave fronts and the float face substantially normal to the wave fronts; at least one power-take-off means in mechanical communication with the fore and aft tensioned cables or legs or members, independently and concurrently either extracting power or applying reactive power to the fore and aft cables by controlling the tension and length of each cable as each oncoming wave crests first moves the at least one float both upward and rearward and the power take-offs and cables subsequently return the float both downwardly and forwardly into subsequent wave troughs, the power-take-off applied tension controlling the submerged depth of the float.

2. The device of claim 1 wherein the majority of the float aft wall of the at least one float is substantially flat and oriented on a substantially fore-to-aft downward inclined angle, the angle approximating the angle of the fore tensioned cable or leg, which float aft wall may have a beam exceeding the beam width of the float.

3. The device of claim 1 wherein the float aft wall has a forward portion and a rearward portion, wherein at least the rearward portion of the aft wall is slanted or convex or curvilinear shaped upwardly relative to the forward portion of the aft wall.

4. The device of claim 1 wherein the at least one wide-beam float has a lower aft wall and a float body and further comprising a lower shoaling lip that extends from the lower aft wall below and forward of the float body protruding downwardly and forwardly approximating the angle of the fore tensioned cable or leg, which lower shoaling lip may be of a wider, narrower, or varying beam than the at least one float, wherein the lower shoaling lip may have port and starboard upward-extending parallel or diverging side plates.

5. The device of claim 1 wherein the at least one wide-beam float further comprises at least one fixed or hinged plane secured to the at least one float, wherein an upward orientation of the float aft wall or an upward and rearward path of motion of the at least one float during each wave crest or subsequent wave trough is altered by the placement of the at least one fixed or hinged plane below or to the sides of the at least one float.

6. The device of claim 1 wherein reactive power applied through the at least one power-take-off means or an at least one auxiliary drive reduces at least one of the fore tensioned cable’s or the at least one aft tensioned cable’s length sufficient to fully submerge the at least one wide-beam float below wave troughs during severe sea conditions.

7. The device of claim 1 wherein the at least one wide-beam float has mass or buoyancy and further comprises at least one controllable aperture, wherein the mass or buoyancy of the at least one float can be controllably increased or decreased by the controlled admission or discharge of seawater through the at least one

controllable aperture in the at least one wide-beam float in communication with at least one internal or affixed cavity or ballast tank, wherein seawater admission into the at least one cavity or tank is facilitated by forcing submergence of the at least one float by utilizing reactive power from the at least one power-take-off means or an auxiliary drive to decrease the length of at least one of the fore or at least one aft tensioned cables or legs, and seawater discharge from the cavity or tank being facilitated by either maintaining sufficient buoyancy in the float bottom to allow gravity drainage with the at least one wide-beam float on the surface or controllably pressurizing the cavity or tank with compressed air or utilizing a gas filled bladder within the float to expand and displace ballast water as at least one of the fore or at least one aft cables is subsequently lengthened and hydrostatic pressure is reduced.

8. The device of claim 1 wherein an angular orientation of the at least one wide- beam float and its path and rate of motion is controlled by controlling a rate at which the at least one power-take-off means shortens or lengthens the fore and at least one aft tensioned cables, which rates may be different for the fore and at least one aft tensioned cables, which the at least one power-take-off means can both independently absorb energy from, and apply reactive power to, the tensioned cables, and utilize control algorithms throughout each wave cycle to optimize net energy capture based on, or learned from, recent wave cycles, measured oncoming wave properties, or artificial intelligence.

9. The device of Claim 1 wherein maintaining the at least one wide-beam float forward face substantially parallel to oncoming wave fronts coming from directions which vary over time is achieved by attaching a lower end of the fore tensioned cable or leg in such a manner as to allow it to pivot laterally around a lower pivot point and movably attaching a lower end of the at least one aft tensioned cable or leg to a substantially horizontal plane substantially circular tracking device on, affixed to, or suspended above, the seabed, such movable attachment allowing lateral movement on such circular tracking device using a low friction sliding or moving attachment selected from the group consisting of rollers, wheels, tracks, rails or mono-rails, sliding or linear bearings, and combinations thereof.

10. The device of claim 1 wherein the fore tensioned cable or leg has a lower pivot point, wherein either a length or a downwardly inclined angle of the fore tensioned cable or leg is reduced by mounting its lower pivot point at an above-seabed position on a piling, a spar or a tower protruding substantially above the seabed.

12. The device of claim 1 wherein an attachment point of the fore tensioned cable is substantially below a still water line and secured to a seabed-affixed piling, a tower, a structure, or a floating vessel.

13. The device of claim 1 wherein the fore and at least one aft tensioned cables’ at least one power-take-off mean is located either on or within the at least one wide- beam float, at or near afore tensioned cable and/or an at least one aft tensioned cable seabed attachment point, or at a position between the at least one wide-beam float and the seabed.

14. The device of claim 1 wherein the at least one wide-beam float further comprises substantially vertical side plates protruding forwardly and downwardly from port and starboard sides of the at least one wide-beam float, wherein the side plates may also diverge outwardly from the port and starboard sides of the at least one wide-beam float.

15. The device of claim 1 wherein the at least one wide-beam float forward face is curvilinear, convex, or semi-circular in shape when viewed from above and concave, flat, or convex when viewed in elevation.

16. The device of claim 1 wherein the at least one wide-beam float further comprises a forward protruding lower shoaling lip and substantially vertical side plates protruding forwardly and downwardly from port and starboard sides of the at least one wide-beam float and forward protruding lower shoaling lip, wherein the side plates may also diverge outwardly from the port and starboard sides of the at least one wide-beam float, wherein the lower shoaling lip has a forward beam width greater than the float beam width.

Description:
MULTI-CAPTURE-MODE WAVE ENERGY CONVERTER WITH BROAD BEAM FLOAT AND SEA BED REACTION MASS

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims priority to US Provisional Application Serial No. 62/762,534, filed 8 May 2018 and U.S. Regular Utility Application Serial No.

16/153,688, filed 5 October 2018, the contents all of which are incorporated herein by reference.

FIELD OF DISCLOSURE

[002] This disclosure relates to a wave energy converter or WEC for converting the energy in water waves into electric power or other useful work. More particularly, the disclosure relates to an improved WEC that captures both heave and surge wave energy modes (multi-mode), with each mode representing half of the total wave energy in deep water. The disclosure further relates to WECs that utilize at least one forward (seaward) tensioned connection to the seabed which seabed connection inexpensively and effectively provides at least part of the reaction mass of one of at least 2 reaction bodies required of a WEC. The disclosure further relates to a WEC utilizing an elongated wide-beam surface float oriented or self -orienting parallel to oncoming wave fronts which float can have a forward cable guide extension to facilitate such orientation, a forward and downward shoaling plane to capture additional wave energy from deeper within a water column, and a float bottom and shoaling plane bottom shape to minimize production of back waves that would otherwise reduce WEC energy capture.

BACKGROUND OF THE DISCLOSURE

[003] Ocean waves are produced primarily by wind, which is produced by solar energy. While ocean wave energy is a huge global renewable energy resource, usually with several times higher energy density (watts/meter 2 ) than solar or wind as it passes through a near surface vertical plane parallel to oncoming wave fronts, solar and especially wind (including offshore wind) have dominated global renewable energy capacity additions in recent years. Wave energy’s delayed commercialization is due primarily to the profusion of unique ocean Wave Energy Converter (WEC) design concepts being proposed, the lack of generally recognized“convergence” on the most cost effective WEC designs, and the high capital cost (CAPEX and

CAPEX/MW of output) of those few early generation WEC designs that have proceeded to ocean trials at large scale to date, primarily with the use of limited available public funding.

[004] WECs, in many parts of the world, will have about the same annual capacity factor (30%-45%) as terrestrial and offshore wind turbines (if they have comparable peak output ratings/mean output ratings). The key to WECs producing a competitive Levelized Cost of Energy (LCOE) with wind is lower CAPEX (as both use free renewable energy, have similar annual maintenance costs/$ CAPEX, and low manpower costs due to unmanned operation). The key to lower WEC

CAPEX/MW is low weight (since both offshore wind turbines and WECs use similar marine steel, composite and electrical components) and high WEC wave energy capture efficiency. Many believe deep water deployed WECs utilizing wave front parallel wide or broad beam surface floats (that intercept maximum energy

containing wave front per meter 3 , per ton, and hence per $ of marine vessel purchased) are likely to emerge as the most cost competitive (lowest CAPEX/MW and LCOE) utility scale WECs.

[005] To achieve high wave energy capture efficiency, WECs must absorb a majority of both heave (potential or vertical component) and surge (kinetic or lateral component) wave energy (multi-mode energy capture), each representing 50% of total wave energy in“deep water” (depths exceeding 1/2 average wavelength).

WECs that only move substantially vertically (including axisymmetric“point absorber” buoy type WECs) only capture a portion of the heave wave energy component and little or no surge component. WECs employing predominantly lateral displacement (like near shore shallow water deployed“surge flap” type WECs), capture only a portion of the“surge” wave component and little“heave” energy. One or more surface or submerged WEC bodies must employ substantial concurrent vertical and lateral displacements to capture a substantial portion of both heave and surge wave energy.

[006] WECs deployed on the ocean surface (where wave energy is highest) must capture (by resisting and damping) the wave-induced relative motion between two or more linked reaction bodies. In surface deployed WECs using one or more surface floats, at least one of the reaction bodies consists of the surface float. The second WEC body can be another surface float, a semi-submerged or submerged moving structure, a body or structure fixed to the seabed, or the seabed itself. It is highly desirable to have the second body either relatively stationary or moving counter to the first floating body’s motion throughout each typical 5-15 second ocean-wave period to maintain or increase the relative motion between the first and second reaction bodies.

[007] While high second body mass can partially stabilize the second body against unwanted motion between the bodies resulting from wave induced forces applied by the first body through the damped linkage with the second body, it is also highly desirable to have the second body smaller than, and weighing substantially less than, (hence costing less than) the first floating body to which the wave forces are applied. Maximum captured wave energy requires maximizing the product of the damping force (between the two linked bodies) and the displacement (linear or rotational) between the two or more linked bodies. If the damping forces (applied by the electrical generator or other power take-off or PTO) between the two linked bodies are too great, the relative motion between the two or more bodies is excessively reduced, but if damping forces are too small, the resultant energy capture (force times distance) is likewise less than the maximum energy capture possible. For most WECs with two or more linked bodies, maximum wave energy capture requires varying the damping force using complex damping force algorithms (including, at times, the application of reactive power) throughout each wave cycle.

OBJECTS OF THE DISCLOSURE:

[008] The objects, principles, and descriptions of the disclosure are primarily described and illustrated using deep-water-deployed terminator and articulating-type WECs that utilize one or more adjacent elongated wave front parallel surface floats which floats concurrently move both vertically and horizontally in response to both wave-induced heave and surge forces for the advantageous low CAPEX/MW and higher-capture-efficiency reasons described previously. These objects, principles, and descriptions, however, are also applicable to, and inclusive of, other types of WECs, including axisymmetric and non-axisymmetric surface floats with at least one tensioned direct or indirect connection to the seabed.

[009] An object of the disclosure is to utilize and achieve high WEC capture efficiency by capturing a substantial portion of both heave wave energy and surge wave energy, each representing half of the total wave energy in deep water.

[010] A further object of the disclosure is to utilize at least two tensioned connections for at least one surface float with at least one of the tensioned

connections directly or indirectly connected to the seabed forward of the surface float and the second tensioned connection under or aft of the surface float and connected either to the seabed or a mass suspended above the seabed, such seabed connection providing part or all of the WEC’s second reaction body or mass while reducing the cost of such second body.

[011] A further object of the disclosure is to provide a WEC with one or more adjacent wave-front parallel surface floats which floats remain self-orienting to oncoming wave fronts and self-adjusting to tidal changes to the mean water level or still water line (SWL).

[012] A further object of the disclosure is to provide a WEC with reduced lost energy capture from“back waves” (waves propagating rearward from the WEC’s surface floats as they are forced rearward and upward by wave crests impacting and lifting the at least one float) by the shape of the float bottom and rearward walls and the path of motion of the float(s) controlled by the tension and length of the at least two tensioned connections to the float(s).

[013] A further object of the disclosure is to provide a WEC with one or more adjacent wave-front parallel surface floats which floats are securely protected from the waves of severe sea states by the submergence of the floats significantly below oncoming wave troughs by pulling the floats substantially below their normal operating depth by forcibly reducing the length of at least one of the seabed tensioned connections, which submerging force can be reduced by optionally flooding part or all interior cavities in the surface float(s) with seawater to reduce the float’s buoyancy, or by combinations of both force and seawater flooding. [014] A further object of the disclosure is to provide a shoaling plane attached to, and extending forward and downward from, the at least one surface float, the shoaling plane accessing wave energy deeper in the water column. The forward and downward extending shoaling plane optionally has substantially vertical port and starboard side shields extending upwards and being either parallel to each other or diverging outward at the front to increase the effective width of the wide beam surface float(s).

[015] A further object of the disclosure is to provide a means to adjust the float’s mass and submerged depth for performance optimization, or de-tuning and protection during severe sea states by admitting or discharging seawater into integral cavities within the float(s) through controllable apertures.

[016] A further object of the present disclosure is to provide an effective and efficient power take-off (PTO) means and control means to resist the wave-induced forces in the tensioned cables by timely increasing or decreasing the length and/or tension in the aft or fore cables. The PTO means is selected from the group including direct driven or geared capstan pully motor-generator drives, linear electric motor- generators, capstan pully-driven hydraulic motor-pumps with optional accumulator reservoirs and electric generators, or linear (cylinder) hydraulic drives.

[017] A further objective of the disclosure is to provide a WEC with high wave- energy capture efficiency over the broad spectrum of wave periods typically found in sea conditions located around the world.

SUMMARY OF THE DISCLOSURE

[018] The disclosure provides a low CAPEX high-capture-efficiency WEC deployable on the ocean surface in deep water (where wave energy is highest) at either small or utility scale (over 1 MW). CAPEX is reduced by utilizing at least one wide-beam surface float oriented or self-orienting parallel to oncoming wave fronts providing interception of maximum wave-front energy per unit of float volume, weight, and hence cost. CAPEX is further reduced by utilizing at least one tensioned connection to the seabed, forward of the float, that allows the seabed to replace all of, or the majority of, the mass and cost of the at least one second WEC reaction body that would otherwise be required. The at least one forward-tensioned seabed connection or cable and the at least one rearward or aft-tensioned seabed connection (FIG. 7) or tensioned mass connection (FIG. 8) both act concurrently as both guide cables dictate float orientation, float position relative to the tensioned connection seabed attachment points and float submergence, and further function as working or energy-transfer connections or cables that drive the float-mounted PTO(s) to capture energy.

[019] High wave-energy capture efficiency is achieved by arranging and suitably controlling the tension and length of both fore and aft tensioned seabed connections by PTO(s) located within the wide-beam surface float(s) in such a manner that the float(s) move(s) concurrently both upwardly and rearwardly on an optimum path on wave crests and are returned both downwardly and forwardly into subsequent wave troughs. Such control of the concurrent paths of the float vertical and horizontal displacement captures both vertical (heave) and lateral (surge) wave energy components (multi-mode energy capture) while minimizing production of back waves from the rear surface of the float(s). Capture efficiency is further enhanced by optionally utilizing a shoaling plane or plate with port and starboard side shields that extend forwardly and downwardly from the float and deeper into the water column.

[020] Secure survival of the disclosed WEC in severe sea conditions is achieved by forcibly submerging the float(s) substantially below storm wave troughs by increasing the tension on, and reducing the length of, either the fore, the aft or both seabed tensioned connections. Float submergence can be further facilitated by controlled admission of seawater into cavities (ballast tanks) formed within the float to reduce float buoyancy and the subsequent use of gravity or pumped ballast water drainage to restore buoyancy.

DISTINGUISHING FEATURES FROM THE RELEVANT ART

[021] Several prior art WECs including the Salter-Edinburgh Duck, and several modern Duck derivatives (Columbia StingRay, WEPTOS WEC, WET-NZ/AZURA, and Brimes Energy Jellyfish), like the disclosure, have one or more adjacent surface floats that collectively have a port-to-starboard width or beam wider than their fore- to-aft depth (broad-beam float) which broad-beam float(s), like the device of the disclosure, are oriented or self-orienting parallel to prevailing or oncoming wave fronts. Such WECs also utilize floats that are mechanically linked to a second reaction body that allows the float to move both vertically and laterally to capture at least some heave and surge wave energy (multi-capture modes). Unlike the disclosure, however, these WECs utilize and require a massive costly second reaction body or mass such as a semi-submerged central cylinder or semi- submerged frame (with a mass often substantially exceeding the mass and cost of their floats that perform all the WEC energy absorbing work). They do not utilize a tensioned seabed connection for all or part of their second reaction body mass.

[022] Vowles (FIG. 1 Prior Art and US 7,737,568) utilizes a self-orienting surface float (which could be broad-beam although not so described) attached to either the seabed (not shown, but described) or a drag plate (shown) by a single tensioned member (containing a piston water pump for energy capture). Vowles does not use the at least two (fore and aft) tensioned members of the present disclosure. The SurfPower WEC (FIG. 3) also utilizes a broad-beam surface float also attached to the seabed by a single tensioned member (that also contains a piston water pump). The Edinburgh Sloped IPS Buoy is slack moored and moves on an inclined axis with a forward shoaling plane. While used as a“point absorber,” the WEC could be made using a wide-beam float. While it was proposed to use the sea water mass contained within an inclined“inertial tube,” it was tank tested (by Chia Poe Linn) using an inclined track fixed to the tank bottom that showed strong multi- mode wave energy capture efficiency.

[023] More common are axis-symmetric (buoy-type“point absorber”) WECs that utilize a single tensioned seabed connection including the Aquaharmonics WEC (FIG. 2 Prior Art) that also utilizes a single cable with a capstan pulley PTO within a circular float that rotates a geared or ungeared motor-generator. Several other WECs also utilize an axis-symmetric float with a single tensioned cable connected to a PTO located on the seabed (like SeaBased shown in FIG. 4 as Relevant Art that uses a linear generator PTO) or the CorPower WEC (not shown but one that uses a rack and pinion PTO within its float).

[024] Several WECs utilize two or more tensioned cables or connections to the seabed (or suspended gravity weights). The Relevant Art shown in FIG. 6 is the Olsen Bolt Lifesaver WEC that utilizes 3-5 vertically-tensioned, seabed-connected cables that drive 3-5 capstan pulley driven PTOs located on the deck of their large- diameter, axis-symmetric“ring” shaped buoy. The multiple tensioned cables spaced a substantial distance apart allow wave energy capture from both float heaving and pitching. FR2869368A1 to Zalcman describes a circular axis-symmetric float attached to three equally spaced seabed attachment points that use three tensioned cables that drive three capstan pulley-driven PTOs with cable tension maintained by using a common counterweight suspended below the float and attached to the opposite ends of the three cables. The Oscilla Triton WEC utilizes a very similar configuration.

[025] It should be noted that WECs with axis-symmetric floats face both scale limitations due to hydrodynamic principles (generally limiting the scale to under 0.5 MW). They also suffer negative economies of scale. When their diameter is doubled to intercept twice the energy-containing wave front, float area increases fourfold, which increases float volume 4-8-fold (volume dictates float weight and cost).

[026] The NEMOS WEC (FIG. 5 Relevant Art), like the disclosure, combines the use of at least one broad-beam float, oriented towards oncoming wave fronts, with at least one tensioned connection to a seabed connection point forward of the float and at least one tensioned connection to the seabed aft of the float (in the embodiment of the disclosure shown in FIG. 8, the aft-tensioned connection is to a ballast or drag plate suspended from a tensioned cable rather than from a seabed position.

[027] The NEMOS US Patent Application Publication No. 2013/0313832 references a prior invention (by Dr. I. K. U. Graw in“Wellenenergie— eine

hydromechanische Analyse”, ISSN 0179-9444, IGAW BUGFI Wuppertal, section 8 page 8-8) that describes a floating body connected to the seabed fore of, and aft of, the float with two cables aligned in the prevailing wave direction. One of the cables of fixed length serves as a guide cable while the other cable of varying length functions as the“working cable” that drives a hydraulic cylinder-type PTO on the float. US 5,066,867 and US 5,808,368 to Shim and Brown, respectively, both disclose WECs using a surface float with a seabed attached guide cable and tensioned working cable with tension maintained by a suspended counterweight ballast. [028] The disclosure is distinguished from the NEMOS WEC (and US

2013/0313832) in several substantial respects:

[029] 1. In the NEMOS WEC, either the front tensioned cable or the aft tensioned cables (usually two) act as the guide cable with the other acting as the working cable (changing length in response to wave-induced float movement). In my WEC disclosed herein, the fore cable with its single rotatable seabed attachment point acts as the guide cable while both the fore and the aft cables are controlled by their respective PTOs with both continuously and concurrently acting as working cables, each independently dictating tensions and cable lengths and the optimum float travel path (to avoid creation of energy consuming“back waves” from the rear of the float) and applying optimum cable tension throughout each wave cycle for maximum wave energy capture efficiency.

[030] 2. The NEMOS float can only rotate (weathervane) about its vertical spindle (which is the float connection point for both the fore and aft tensioned cables) to remain parallel with oncoming wave fronts. The NEMOS fore-to-aft travel line of the float is dictated by the fixed or limited location(s) of the single or dual, fore seabed attachment points and the single fixed rearward seabed attachment point (at the tower base). If, for example, when the oncoming wave direction differs by 45° from the fixed travel line, the NEMOS float will only intercept 0.707 (cosign of 45°) of the wave front energy. My WEC as disclosed herein (as per the embodiments shown in FIG. 7 or FIG. 8) provides true and full weathervaning directional adjustment with the float travel line always fully normal to the wave direction and the wide-beam float always parallel to oncoming wave fronts because the aft tensioned cable attachment point is free to move.

[031] 3. Unlike the NEMOS, my WEC only requires two (not three) tensioned cables or members fororienting/weathervaning and can weathervane a complete 360°, if required. The NEMOS can only weathervane, at most, between its two fixed forward seabed cable attachment points. According to my disclosure, the rear tensioned cable or member is free to move laterally to facilitate float orientation. In the NEMOS WEC, the aft tensioned cable attachment point is fixed. With my WEC as disclosed herein, the fore tensioned cable or member is guided into the float well forward of the float’s center of buoyancy (COB) and center of gravity (COG) with the rearward tensioned cable well aft of same. This maintains the float orientation normal to its line of motion. The NEMOS WEC has both fore and aft cables attached to the float at approximately the same location (its vertical spindle) that is near the COB and COG.

[032] 4. My WEC as disclosed herein does not require a vertical tower or column for mounting its near-seabed aft pulleys and for placing it’s energy

conversion equipment (PTO) high above the water line like preferred embodiments of the NEMOS, which tower adds substantial CAPEX or limits NEMOS deployments to existing offshore tower locations that are limited in number, often in poor wave climates, and confined to limited water depth locations (under 50 meters). Placing the fore and aft cable PTOs on the deck or within the float(s) of my WEC as disclosed herein, reduces the amount of cable length exposed to seawater fouling conditions or marine mammal injury (by 2-3 fold), eliminates the need for long cable lengths near the seabed, and eliminates the need to maintain near-seabed pulleys that accelerate cable wear.

[033] 5. My WEC as disclosed herein utilizes a forward extension from the float

(as shown in FIGS. 7 or 8 as the element assigned reference character(s) 211 and/or 212) to maintain the angular orientation of the float bottom and back at approximately the same angle as the forward tension cable or member. This, in concert with the PTO control system, allows the flat float back and any extended forward shoaling plane to maintain its angular orientation and linear line of motion during each upward and rearward power stroke to thereby limit or eliminate any energy losses from“back waves” created by float motion. The NEMOS float has a semicircular float bottom, likely because of substantial rocking or pitching, which float bottom shape pushes up an energy consuming“back wave” during each power stroke.

[034] 6. The NEMOS WEC lacks a shoaling plane (with optional wave- focusing, vertical side shields) extending forward and downward from the float to capture additional wave energy from deeper in the water column. The NEMOS WEC also lacks a relatively flat float bottom-aft wall having an inclined angle approximating the inclination angle of the tensioned fore cable and any shoaling plane, all of which reduces or eliminates the creation of any efficiency-reducing back waves. BRIEF DESCRIPTION OF THE DRAWINGS

£035] FIG. 1 is a perspective view of a relevant art WEC according to Vowles.

[036] FIG. 2 is side view in elevation of a relevant art WEC according to

Aquaharmonics.

[037] FIG. 3 is a perspective view of a relevant art WEC according to SurfPower.

[038] FIG. 4 is a perspective view of a relevant art WEC according to SeaBased.

[039] FIG. 5 is a perspective view of a relevant art WEC according to NEMOS.

[040] FIG. 6 is a perspective view of a relevant art WEC according to Bolt Lifesaver.

[041] FIG. 7 is a side sectional view in elevation of a WEC according to one embodiment of the disclosure.

[042] FIG. 8 is a side sectional view in elevation of a WEC according to another embodiment of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[043] Referring now to FIG. 7, a WEC shown generally as , includes a single float 204, or multiple attached adjacent surface floats (not shown), with a combined port-to-starboard float width or beam greater than the fore-to-aft float depth, excluding any attached shoaling lips or other appendages, the float(s) being oriented or self-orienting parallel to oncoming wave fronts, with the floats being attached to the seabed with at least two tensioned cables 210 and 217. The cabled connections to the seabed provide a reactive second body (the seabed itself). Float 204

concurrently moves both upwardly and rearwardly in response to vertical heave buoyant forces and lateral surge kinetic forces, respectively, during upward power strokes and returns forwardly and downwardly on subsequent wave troughs.

[044] Float 204, when viewed from above, may have a linear (straight line) forward face 201 as shown or the float may have a curvilinear convex or semi- circular face (not shown), which for certain sea conditions (primarily waves of relatively uniform period and height) may provide some wave-focusing“antenna effect” to incoming wave fronts that can somewhat improve energy capture efficiency. Float 204 may also have substantially vertical side shields 272 protruding or extending forwardly and downwardly from the port and starboard float sides or extending even further forwardly and downwardly along shoaling plane or plate 205, which side shields 272 or shoaling plane 205 may flare substantially outwardly port to starboard making the beam width forward of the float wider than the beam width of the main float body 204.

[045] Float 204’s upward and rearward movement during each oncoming wave crest is resisted by at least one PTO 216 driven by and controlling both the length and tension of fore cable 210 connected to forward seabed attachment point 235 with the aft or rear cable 217 serving as a guide cable of fixed length. In preferred embodiments, however, at least two PTOs are utilized, the second PTO 215 being attached to aft cable 217. Alternatively, both fore and aft PTOs can be attached to a common PTO 233 that may have differing drive ratios (shown as differing capstan pully diameters 233) or the two separate PTOs can be otherwise mechanically or electrically linked. The circular arrows around PTOs 230 and 231 with capstan pulleys 215 and 216 or alternatively the combined single PTO 232-233 show the capstan pully rotational direction during the float upward and rearward power stroke which direction is reversed during subsequent down strokes. By using programable or artificial intelligence or Al- (feedback) controlled PTOs to control both fore and aft cable length, the length rate of change, and the cable tension throughout the entirety of each wave cycle, float movement and position, displacement, and combined PTO net energy capture can be optimized.

[046] Past WEC research (Johannes Falnes and Kjell Budal of NTNU in the

80’s and 90’s) clearly established that surface float WECs could substantially increase wave energy capture efficiency by“latching” (maintaining the float position in the bottom of each wave trough until wave induced buoyant forces on the float increased substantially as float submergence increased). More recent research (Alexandria Price, U. of Edinburgh, Fusco and Ringwood, U. of Ireland Maynooth,

2011 and many others) has universally established that WEC PTO reactive control strategies (using a WEC PTO to apply force against the float rather than absorbing power from the float) during a portion of each wave cycle substantially increases net WEC power output). The fore and aft PTOs of this disclosure alternatively acting as generator and motor can supply optimum reactive power, including accelerating float return during declining waves and/or increasing float submergence and displacement in wave troughs. Predictive PTO control via Al, with or without advance wave height and period measurement, will further enhance capture efficiency and are within the scope of this disclosure.

[047] The PTOs can be contained within flooded or dry cavities within the float 204 body (as shown) or can be attached to the float deck or body (not shown), the seabed (260 and 260’ dotted) or anywhere along the fore or aft tensioned cable lengths (260 and 260’ shown on cables at or near seabed attachment points). The PTOs can be capstan pulley or spool cable drives (shown) or other rotary input- output PTOs (not shown) or linear input-output (260 and 260’) including linear hydraulic cylinders, linear electric generators, or linear ball screws. The PTO(s) maintain tension during both upward power strokes when wave energy is absorbed and during downward return strokes when a portion of absorbed wave energy is utilized to maintain cable tensions by utilizing motor-generator reactive power, mechanical springs, or like means.

[048] In some embodiments where aft cable 217 is utilized as a working cable, float 204 can weathervane to maintain its wave-front parallel position with respect to oncoming wave fronts by attaching aft cable 217 at its termination 252 with rollers 253 on cantilevered axels 255 or other rolling or sliding means to at least a partial semi-circular horizontal plane track, or rail 250, or near seabed linear or curvilinear tensioned line (not shown) affixed to the seabed (shown) by seabed attachments 251 or positioned above the seabed (not shown).

[049] Float 4 may contain at least one internal cavity 243 with at least one lower aperture 240 and upper aperture 241 for the controlled inlet or release of seawater ballast to either increase or decrease float mass or to substantially reduce float buoyancy to facilitate partially or fully submerging the float during severe sea conditions. At least one of the float 204 interior cavities may contain a bladder 242 that can be at least partially pre-filled with gas or can be refilled with compressed air from air storage tank with compressor 259. When the fore or aft tensioned cable or leg is shortened by the PTO or an auxiliary drive, forcing partial or full submergence of the float, air within the cavity or bladder volume is displaced by seawater ballast that reduces float buoyancy and the required submergence force. The buoyancy and draft of the float can be controllably restored by reversing the process. Alternatively, the air storage tank with compressor 259 can discharge seawater by opening lower apertures 240 and closing upper apertures 241 while discharging compressed air from tank 259 into at least one interior cavity 243.

[050] Float 204 may also have an extended lower wave-shoaling lip 205 integral with, or attached to and extending below and forward of, float rear wall 202 which lower wave shoaling lip 205 may extend to, or beyond, the full or partial width (beam) of float 204. Float port and starboard side walls may extend substantially vertically downwardly below the bottom 202 of float 204 serving as a directionally stabilizing keel surface (not shown). The flat rear wall 202 of float 204, plus the lower shoaling extension 205, if used, combined provide a large plane area inclined at approximately the same angle as the fore tensioned cable 210. This large plane area substantially maintains the angle throughout each wave cycle such that little or no energy consuming“back wave” is produced. At least the upper aft section of the float aft wall can be slanted or an upwardly-extending curvilinear shape to prevent wave surge forces from rotating the float rearward or displacing the float downward, which can otherwise reduce energy capture by the rear tension cable or leg.

[051] Surge wave energy capture can be improved by decreasing the angle between tensioned cable or leg 210 and a horizontal plane. In deep water, this may make the fore cable or leg excessively long or costly. Elevating the cable 210 attachment point 235 upwardly to 235’ on upright piling 265 and supported by guy wires 266 can both shorten fore cable 210 and reduce its inclination angle.

[052] Selecting the proper RPM ratio between PTOs 230 and 231 provides one method of maintaining a constant and desired inclined angle among float back 202, shoaling plane 205 and tensioned fore cable 210 throughout each wave cycle.

Alternatively, forward PTO 231 and aft PTO 230 can be independently controlled to optimize fore and aft cable tensions, float movement path, and float and tension cable inclination angles. The float may utilize one or more forward tension cable roller or funnel guides 211 , 212 and 213 to guide tension cable 210 above, below and/or through lower shoaling lip 205. The guides assist in maintaining float face 201 approximately normal to forward cable 210 and parallel to oncoming wave fronts. An attachment below guides 211 and 212 may also guide power and communications cable 214 to the seabed near tensioned cable attachment point 235 for power transmission to, and communication with, shore facilities. While only one forward PTO and one aft PTO 230 with capstan pulleys 216 and 215, respectively, are shown in FIG. 7, multiple smaller forward and aft PTOs can be positioned across the wide-beam width of Float 204, each connected to one of multiple fore tensioned cables or aft tensioned cables which multiple fore and aft cables could converge at or above the fore and aft near-seabed attachment points, 235 and 252 respectively.

[053] Float 204 may also have one or more planes 270 parallel to, and affixed to, float aft wall 202 via struts 271 or affixed to the float sides (not shown) or to at least one keel normal to float bottom 202 and affixed to float bottom 202 or struts 271 , which plane 270 and keel can assist in preventing the float from rotating substantially away from the inclination angle from horizontal formed by tensioned fore cable 210 and the floats alignment with fore cable 210 when viewed from above. Plane 270 can be of a fixed angle relative to float bottom 202 or hinged to allow a differing angle on the power and return stroke.

[054] FIG. 8 describes an alternative embodiment of the disclosure wherein the tensioned fore cable 210 is attached to both the seabed 228 and float 204 forward PTO 231 in a manor identical to the embodiment of the disclosure shown in FIG. 7 that allows utilization of the seabed to provide a major portion of the required WEC reaction body mass. Tension is maintained in the aft cable 217 by a suspended high- density counterweight ballast 288 connected to the end of aft cable 217 by

connecting post 282 through cable connecting eye 285. Tension in cable 217 and a stable position and elevation of counterweight 288 during wave-induced float’s 204 upward and rearward travel can be further enhanced by the entrained seawater water mass and drag plate mass of surface 280 with angled edges 281 and drag plate support struts or cables 284.

[055] While the present disclosure has been described in connection with several embodiments thereof, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the disclosure. Accordingly, it is intended by the appended claims to cover all such changes and modifications as come within the true spirit and scope of the disclosure. What we claim as new and desire to secure by United States Letters Patents is: