WO2009152606A1

WO2009152606A1 - Wave energy conversion system

Info

Publication number: WO2009152606A1
Application number: PCT/CA2009/000793
Authority: WO
Inventors: Frank Louis Stromotich
Original assignee: Frank Louis Stromotich
Priority date: 2002-10-30
Filing date: 2009-06-12
Publication date: 2009-12-23
Also published as: CA2408855A1; WO2009152606A9

Abstract

An underwater wave energy converter (WEC) (10) has a piston (32) that reciprocates up and down as recurring waves (22) pass over. Downward motion of the piston (32) drives the rods or plungers (50b) of a multiplicity of hydraulic jacks (50) to pressurize hydraulic fluid in an energy conversion system. Ultimately, the energy conversion system powers one or more hydraulic motors (511, 512) that drive an electric generator (510) or multiple generators. A sensor system (25) detects characteristics of in-coming waves such as by detecting changes in pressure as in-coming waves (22) pass over the sensor system (25). The sensors can be mounted on the ocean floor seaward from the WECs (10), and a control computer system (231) calculates characteristics of the in-coming waves such as wave height and speed data, and uses the data to control aspects of the WECs (10) and othei components of the energy conversion system.

Description

WAVE ENERGY CONVERSION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Canadian Patent Application No. 2 634 450, filed June 18, 2008, which is expressly incorporated by reference herein.

BACKGROUND

The present invention relates to ocean wave energy converters, particularly for application near shore, and more particularly to a novel system of wave energy converters having hydraulic components for converting energy of recurring waves to electric energy. The publications listed below are expressly incorporated by reference herein and describe prior approaches to convert energy of ocean waves to another form of usable energy, such as electric energy:

Burns: International Patent Publication No. WO 2004/0003380; Burns: International Patent Publication No. WO 2007/019640; Gardner: U.S. Patent No. 6,256,985;

Stromotich: Canadian Patent Application No. 2 408 855.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In an embodiment of the present invention, several underwater wave energy converters (WECs) are provided, each having a piston that reciprocates up and down as recurring waves pass over. Downward motion of the piston drives the rods or plungers of a multiplicity of hydraulic cylinders to pressurize hydraulic fluid in an energy conversion system. Ultimately, the energy conversion system powers one or more hydraulic motors that drive an electric generator or multiple generators.

In one aspect of the present invention, a sensor system detects characteristics of incoming waves, such as by detecting changes in pressure as an incoming wave passes over an array of sensors. The sensors can be mounted on the ocean floor seaward from the WECs. A computer system calculates characteristics of the incoming waves, such as wave height and speed from data read from the sensors. Such information is used to control aspects of the WECs and other components of the energy conversion system. For example, preferably the sensor system and computer calculation are used for discrete switching of hydraulic fluid flow and operation of hydraulic components associated with each WEC, the object being to efficiently convert potential and kinetic energy of selected ocean w aves and to transmit power to consumers on shore.

In another aspect of the invention, each WEC includes an upper deflector that, under computer control, can be positioned to capture energy of an incoming w ave and direct it downward toward the vertically reciprocating piston of a WEC during the downward power stroke. The deflector is retractable, under computer control, at an appropriate time, such as coincidental with a wave trough, when the piston is moved back up.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and man} of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying draw ings, wherein:

FIGURE 1 is a perspective view of components of a wave energy conversion system in accordance w ith the present invention showing three w ave energy converters (WECs) on the ocean floor near shore, connected by cables laid on the sea bed to a utility on shore, with parts shown diagrammatically;

FIGURE 2 is a perspective view of one of the WECs of FIGURE 1, such one WEC having a piston at top position with a deflector fully raised to capture as much energy as possible from an oncoming ocean wave during a power stroke;

FIGURE 3 is a perspective view of the WEC of FIGURE 2 with parts in different positions, namely, with the piston at the lower limit of the power stroke and the deflector at its lowest position to enable sea water to be discharged into the wave trough during a return stroke;

FIGURE 4 is an exploded view of the WEC of FIGURE 1 and FIGURE 2 show ing the component parts in perspective; FIGURE 5 is a perspective view of components of the WEC of FIGURES 1-3, namely, an assembly of hydraulic cylinders underneath the piston;

FIGURE 6 is a schematic representation of hydraulic fluid energy conversion equipment of a wave energy conversion system in accordance with the present invention. with a WEC operating in power stroke to boost pressure through a fluid power transformer and push fluid to storage in an accumulator;

FIGURE 7 is a schematic representation similar to FIGURE 6 w ith the WEC operating in a power stroke, except w ith pressure being reduced through the fluid power transformer and fluid flow ing to storage in the accumulator;

FIGURE 8 is a schematic representation similar to that of FIGURE 6, with the WEC operating in return stroke with pressure from the accumulator being boosted through the fluid power transformer and fluid flowing to the cylinder assembly to lift the piston to its top position; FIGURE 9 is a schematic representation similar to FIGURE 8, with the WEC operating in the return stroke, except w ith pressure from the accumulator being reduced through the fluid pow er transformer and fluid flowing to the cylinder assembly to lift the piston to top position;

FIGURE 10 is a schematic representation of a second embodiment of w ave energy conversion system in accordance with the present invention, w ith a WEC operating in a pow er stroke, with pressure from an accumulator being boosted through a fluid power transformer having a motor rotatably connected to a pump, after passing through a fluid transposing sw itch;

FIGURE 11 is a schematic representation similar to FIGURE 10 with the WEC operating in the pow er stroke, but with pressure from the accumulator being reduced through the fluid pow er transformer after passing through a fluid transposing sw itch;

FIGURE 12 is a schematic representation similar to FIGURE 11 with the WEC operating in the return stroke, with pressure from the accumulator being boosted through the fluid pow er transformer after passing through a fluid transposing sw itch; FIGURE 13 is a is a schematic representation similar to FIGURE 12 with the

WEC operating in the return stroke, with pressure from the accumulator being reduced through the fluid pow er transformer after passing through a fluid transposing sw itch;

FIGURE 14 is a schematic representation of a third embodiment of w ave energy conversion system in accordance with the present invention, with a WEC operating in pow er stroke, the WEC being represented by a piston with multi-cylinder assembly below divided into tw o groups, each represented by a single cylinder, with one cylinder connected to transfer fluid directly to a fluid energy sw ing accumulator introduced in this embodiment, and with pressure from the second cylinder being boosted through the fluid pow er transformer and fluid flow ing to storage in the high pressure accumulator;

FIGURE 15 is a schematic representation similar to FIGURE 14, except with the WEC operating in return stroke with fluid from the energy swing accumulator acting to return the piston to its top position;

FIGURE 16 is a schematic representation of a fourth embodiment of w ave energy conversion system in accordance with the present invention; and

FIGURE 17 is a flow diagram of operation of a w ave energy conversion system in accordance w ith the present invention. Detailed Description

Terminology

ATerminal≡ or Aline terminals means a connection point of a hydraulic fluid line to a port of a hydraulic fluid device, such as "input terminal" means a point of flow into a device such as a hydraulic motor, pump, accumulator, "fluid pow er transformer," and so on, and Aoutlet terminals means a point of flow out of a hydraulic device;

Acylinder assembly switching states means valve positions setting the number of cylinders in groups for operation below a piston thereby adjusting the ratio of w ave pressure to fluid pressure at the terminal of the cylinder assembly, where state one means all cylinders in operation, providing low est fluid pressure and highest fluid flow in communication w ith the fluid pow er transformer, and may also include, in the alternative, a second group of cylinders whose fluid flow by -passes the fluid pow er transformer and communicates directly w ith an accumulator for that purpose;

Afliiid power transformers means a device that transforms fluid pow er from one particular combination of pressure and flow at the input terminals to another combination of pressure and flow at the output terminals;

Afluid transposing switch≡ means a switching device for use with a fluid pow er transformer comprising multiple tw o-w ay valves, with position indicator mechanism, for transposing the fluid lines to a hydraulic motor w ith the fluid lines to a hydraulic pump in the configuration w here a pump serves in place of a fluid motor operating in regenerative mode;

Afluid piping network switching state≡ means a particular set of fluid control valve positions and motor displacement settings that facilitate hydraulic fluid flow through the fluid power transformer during a power-stroke and return-stroke power production axle;

Afluid energy swing≡ means a system for transferring fluid energy between a power-stroke and a return-stroke by communication between a hydraulic cylinder assembly and an accumulator without need for hydraulic rotary equipment;

Aocean-wave-degree≡ means a unit of measurement in units of time or distance, equivalent to the period of an ocean w ave divided by 360, the number of degrees in a w ave cycle, used in a context analogous to degrees-before-top-dead-center as commonly shown on a scale on an engine block for advancing ignition timing for internal combustion engines; for example, a w ave period of 18 seconds computes to a wave speed of 20 ocean-w ave-degrees per second;

Awave state vector≡ means a two-dimensional vector representation of the wave w ithin a computer control system, which includes separate vectors for the wave peak and the wave trough, the "wave peak vector" defines the location of the vertical axis of the w ave crest in units along the x-axis corresponding to distance in feet from piston center, and the elevation of the wave crest in units along the y-axis corresponding to elevation in feet relative to the top of shell opening; the wave trough vector defines the location of the vertical axis of the wave trough in units along the x-axis corresponding to distance in feet from piston axis center, and elevation of the wave trough represented in units along the y-axis corresponding to elevation in feet relative to the top of shell opening; the wave peak vector minus the wave trough vector equals the wave vector, the real component of which equals the horizontal distance betw een the peak axis and trough axis of the w ave and the imaginary or quadrature component equals the wave height in absolute terms; the wave vector is used within the computer to select those w aves that can be harvested efficiently as the} approach the WEC; other wave vectors may be computed to monitor distant waves as the} approach from farther off-shore;

Avector drive≡ means a system with computer control for optimal functioning of the WEC. which includes sensing a train of on-coming waves, computing their wave state vectors, setting the switching states for the cylinder assembly and the fluid pow er transformer for various operating conditions as the} develop, initiating and controlling the transmitting of energy during the pow er-stroke-return-stroke power production axle, and transmitting electric power across the underwater cables to a user on shore. General

Aspects of an embodiment of a wave energy conversion system in accordance with the present invention are shown in FIGURE 1. Several wave energy converters (WECs) 10a, 10b and 10c are installed on the ocean floor 20. Preferably the location of installation is near shore 21, where energy of waves 22 have a significant translation component toward the shore. In deeper water, the motion of water particles is more nearly orbital. As described in more detail below, each WEC has a piston designed to translate up and down as recurring w aves pass over it. The piston rides in an open topped shell to which it is sealed such that the volume of the shell bound at the top by the piston varies. The interior volume of each WEC is vented to the atmosphere, such as by a vent pipe 15a. 15b, or 15c, which is sufficiently tall as to extend above the water. Alternatively, or additionally, communication to the atmosphere can be shared by w ay of vent piping 12a. 12b, and 12c that communicates with a shared vent pipe 16, by way of canister 11 mounted closer to the shore. Canister 11 with its shared vent pipe 16 serve as an alternate communication vent to atmosphere where high w aves may be over topping the individual vents on the WECs.

In the embodiment represented in FIGURE 1, the WECs are offset relative to the incoming wave crest 26 and trough 27. Thus, the pistons of the individual WECs, which act independently, do not reciprocate in synchronism. Rather, the pistons move down and up sequentially for a smoother power flow. More specifically, in a representative embodiment the most seaward WEC 10a will first encounter the wave crest 26 and operate in a downward power stroke, followed by the next most seaward WEC 10b. and finally the least seaward. WEC 10c. The return stroke of each piston occurs as the wave trough 27 passes over. The up and down reciprocation of the pistons drives a system of hydraulic cylinders, there being multiple hydraulic cylinders beneath each piston. Hydraulic fluid pressurized in the down stroke ultimately drives one or more rotary hydraulic motors connected to an electric generator. Energy of the pressurized hydraulic fluid can be stored in accumulators. Power and system control cables 23 connect the WECs to an electrical distribution surface structure 24 of an under ground electrical distribution system on shore. The control cables include fiber optic lines or other signal transmitting lines from a computer control center to components of the WECs and the hydraulic energy conversion system. Preferably, the control system includes an array of pressure sensors 25, which detect characteristics of incoming w aves prior to the w aves passing over the WECs. The computer control system calculates characteristics of the individual w aves, such as w ave height and speed, thereby estimating the energy of the on-coming wave and controlling aspects of the wave energy conversion system accordingly. Wave energy converter construction

Aspects of an individual WEC, in accordance with the present invention, are shown in FIGURES 2-5. With reference to FIGURE 4, an upright, open-topped shell 31 has an underside for resting securely on the ocean floor w ith the shell axis nearly vertical. After the shell is sunk to the ocean floor, a ballast of two or more parts 34a. 34b is installed on beams 42 that project outward from the lower edge portion of the shell. Upward extending fingers 42a. at the ends of the beams 42, lock the heavy ballast pieces to the shell. Horizontal pins extending through the ballast and securely affixed to the side of the shell can also be provided. In a representative embodiment, the shell can be elliptical, with a major axis of approximately 36 feet aligned transversely to the direction of on-coming waves and a minor axis of approximately 21 feet aligned approximately parallel to the apparent direction of movement of an on-coming w ave. The overall height of the shell can be 11 feet. The shell can be reinforced concrete w ith components of stainless steel or another suitable alloy or rigid, durable material, resistant to erosion by seawater, cast into the concrete where other components are fitted to the shell. The ballast pieces can be reinforced concrete and. accordingly, weighty enough to stably anchor the shell to the ocean floor. Such dimensions are for illustrative purposes only, and the WECs can be scaled differently, but preferably are large for significant power production in a relatively simple design.

Still referring to FIGURE 4, a horizontal base plate 52 is fixed to the inside bottom of the shell 31. An array of hydraulic cylinders 50 is supported on the base plate. For example, the cylinders can include the usual bodies 50a and telescoping rods or plungers 50b. The upper ends of the plungers are connected to a structural framework 53. As seen in FIGURE 5, up-and-down movement of the framework is guided by telescoping columns 54, 55 having bottom ends fixed to the base plate 52 and top ends secured to the framework 53. Two such telescoping guide columns are shown in FIGURE 5 but four or more may be supplied to maintain the structural framework 53 in alignment with the base plate without unduly stressing the plungers or rods of the hydraulic cylinders. Returning to FIGURE 4, the piston 32 is a cup-shaped member im erted within the shell 31. o\ er the structural franiew ork 53 The piston 32 fits closeh o\ er the franiew ork and fairh close within the shell 31 The underside of the piston is secured to the top of the framew ork The piston has a peripheral skirt portion that extends down along and past the peπphen of the framew ork A low er ring 32r is spaced below the bottom edge of the piston skirt and is connected thereto b} collapsible pneumatic cy linders 32c. thereb} adding to the apparent depth of the piston skirt Vertical slats 32s extend upw ard from the ring 32r and are slideable along the outside of the piston skirt While tw o such slats 32s and pneumatic c\ hnders 32c are shown, preferabh the} are spaced more closeh together around the circumference of the piston, such as e\ er\ foot or so In a representatπ e embodiment, the stroke of the piston 32 is limited to about twice the \ ertical dimension from the top of the piston to the bottom of the ring 32r and about 2/3 the depth of the shell 31 A reliable annular seal 33 is connected betw een the piston and the interior 32b of the shell An inner lip portion 33a of the seal has a peripheral edge secured to the top of the piston, and an outer skirt portion 33b of the seal is secured to the inner w all of the shell at the location corresponding to the bottom most position of the piston The fit of the seal is w ater tight such that seaw ater is not introduced into the shell below the piston The flexible seal material rolls up as the piston shifts upw ard and unrolls as the piston mo\ es down Slats 32s help pre\ ent the flexible seal from entering the space below the piston as it mo\ es up

A \ ent 15 attaches to the side of the shell to seπ e as a IIΛ draulicalh adμistable snorkel The snorkel can ha\ e telescoping parts so that its height can be adμisted depending on w a\ e conditions, such as b} an internal hy draulic )ack Mo\ ement of the piston 32 causes air below the piston in the chamber of the cy linder assembh to communicate with the atmosphere through the top of the snorkel The flexible seal can be manufactured from reinforced flexible but w atertight fabric formed o\ er a mold The dimensions of the annular seal are fulh described b} measurements of the ma)or and minor axis of the piston and of the shell, and the length of the piston skirt b} the distance from bottom of the stroke to the top of the shell The piston is preferabh fluted to enable the annular seal to fit wrinkle-free against the piston as the outer side of the seal rolls into contact with the piston under pressure from sea w ater as the piston mo\ es up in a return stroke The fluting can be of a form that comprises a hollow channel that co\ ers the top of the aforementione slats The WEC includes an arcuate deflector 38 that can be moved to a position to direct incoming waves downward toward the piston. The deflector can be lowered alongside the shell so as not to interfere w ith expulsion of sea water from the shell as the piston is moved upward. To position the deflector, hydraulic cylinders 39 are mounted on opposite ends of the shell, and corresponding ends of the deflector are pivoted on the reciprocating plungers or rods of the cylinders, such as by pins 41 extending through holes 41a. Additional control cylinders 45 are mounted on the exterior of the shell near the minor axis and at the same side, which w ould correspond to the side away from an incoming wave. The central portion of the arc of the deflector is carried by the reciprocating plungers of hydraulic cylinders 45. Operation of cylinders 39 and 45 can be coordinated to translate the deflector upward and also rotate it somewhat fore and aft around the axis 38a defined by the holes 41a and pins 41. As described in more detail below, operation of the four hydraulic cylinders is under computer control for raising and tilting the w ave deflector so as to capture w ave energy and direct it downward during a power stroke, and retract the deflector during a return stroke.

FIGURE 2 illustrates the WEC 10 w ith parts assembled and w ith the curved deflector 38 raised and tilted forward in preparation for a cresting incoming wave. The piston 32 is fully raised adjacent to the top of the vertical shell 31. The hydraulic cylinders 39 at the sides have their rods extended to lift the deflector. The rear cylinders (the upper ends of which are represented at 45 in FIGURE 4 but are not shown in FIGURE 2) are raised to tilt the deflector forward. The surface 43 of the ballast piece 34a, which faces the incoming w ave, is concave with upright fins 40 to assist in directing the w ave along the ballast surface and toward the raised deflector. The overall result is to increase downward pressure of the cresting w ave on the piston as the w ave passes over.

In the position of FIGURE 3, the deflector has been lowered and tilted down along side the shell opposite the direction of w ave approach. FIGURE 3 represents the lower most position of the piston 32. From that position, at or near alignment with a w ave trough, the piston moves upward to expel water at approximately the location of the trough.

Hydraulic System

FIGURES 6-9 are schematic representations of hydraulic fluid energy conversion equipment of a w ave energy conversion system in accordance w ith the present invention. Piston 252 (shown diagrammaticallv) corresponds to the WEC piston described previously. All hydraulic cylinders driven by such piston are represented as a single cylinder 221, with an internal volume 255 for hydraulic fluid. Such volume within the cylinder decreases as the piston moves down and increases as the piston is moved up, pressurizing fluid on the down stroke and reducing pressure on the up stroke. An inlet- outlet port at the bottom communicates with the fluid conduit 201, which leads to a valve 211. After valve 211, the conduit branches, one branch leading along a conduit 202 through a valve 215 and to inlets of hydraulic motors 511, 512 of known design. Such motors have a common shaft 513 that drives the electric generator 510. Returning to valve 211, another branch from the conduit 201 leads to a two position fluid valve 214, which can be referred to as a boost/reduce switch. In the position indicated in FIGURE 6, such switch directs flow through a conduit 203 to a motor 222. From the motor, the fluid flows through a conduit 204 and a flow transducer 212, then through a conduit 205 to a low pressure accumulator 224. In this condition, the low pressure accumulator 224 is also receiving fluid from the outlets of the hydraulic motors 511, 512. At the same time, output shaft 227 of the motor 222 drives an upper motor 223 operating in regenerative mode so that it functions as a pump. The inlet of regen motor 223 receives fluid from the cylinder 221 through another branch 202a and boosts the pressure at the outlet and into an outlet conduit 206, then through a flow transducer 213, conduit 207 and into a higher pressure accumulator 225.

A control computer 231 monitors pressure and displacement, flow to and from the cylinder assembly 221, accumulators, and through motor and pump units 222, 223. All hydraulic motors are fully controllable electrically and are equipped with pressure sensors at inlet and outlet ports, double swing swash-plate fluid displacement actuators with position sensors, and shaft speed indicators (for example, represented at 227a in FIGURE 6). During the power stroke, a signal from a flow transducer 211 on the fluid line of the cylinder assembly is used by the computer to control fluid flow and piston speed during the power stroke (power stroke being represented by the arrow 251). Hydraulic fluid flow is biased in favor of boosting pressure through the fluid power transformer (motors 222 and 223), where receiving-end pressure is about the same as the sending-end pressure. This avoids pressures being unbalanced and there being no flow, which would effective!} freeze the piston in power stroke or return stroke. During the pow er-stroke, shown in FIGURES 6 and 7, the force of the wave presses down, as indicated by arrow 251, on the piston 252 and into the cylinder assembly 221 which is schematically represented as a single cylinder and rod or plunger. The internal pistons 254 force fluid from the interior volume 255 into the fluid line 201. In the case where the pressure of the high pressure accumulator is higher than the pressure from the cylinder assembly, the computer sets the boost/reduce switch 214 to "boost", connecting flow pipe 201 to 203 and designates the lower motor 222 as driving motor, as represented in FIGURE 6. The computer adjusts the displacement setting to provide power for the motor by drawing from the cylinder assembly and discharging to the low pressure accumulator 224. The pumping is done from the cylinder assembly to the high pressure accumulator 225 by the second motor 223 put in regenerative mode by computer control of the displacement setting on the second motor 223.

When the pressure of the high pressure accumulator is lower than the cylinder assembly, the computer sets the boost/reduce switch 214 to "reduce" thereby connecting flow pipe 206 to 203 and designates the upper motor 223 as the driving motor, as shown in FIGURE 7. In the "reduce" position, the motor inlet is connected to the cylinder assembly 221 through pipe 201 and the motor outlet to the high pressure accumulator 225. Simultaneously the computer switches the displacement setting of the second motor 222 to regenerative mode to cause it to pump fluid from the low pressure accumulator 224 to the high pressure accumulator 225. In summary, the two fluid sw itching states for the power-stroke are identical except for the position of the fluid boost/reduce sw itch 214.

At the end of the pow er stroke, valve 211 is closed, thereby effectively "locking" the piston in the low er-most position. Also, an electric brake 227b is set to lock the common or connecting shaft 227 of motors 222, 223. Then, as the w ave trough approaches, the system is set for the return stroke, represented in FIGURE 8 and FIGURE 9.

During the return-stroke, the brake 227b is released and the force from the cylinder assembly 221 is pressing up under the piston 252, as indicated by arrow 261, to discharge seaw ater from the shell. In the case where the pressure of the high pressure accumulator 225 is low er than the pressure from the cylinder assembly 221, the computer sets the boost/reduce switch 214 to "boost", and designates the low er motor 222 as the driving motor, as shown in FIGURE 8. The inlet of motor 222 is connected through pipe 203 and boost/reduce switch 214 to pipe 206 and to the high pressure accumulator 225. and the motor outlet is connected through pipe 204 and 205 to the low pressure accumulator 224. The power of motoring is used to drive the second motor 223 in regenerative mode. The regenerative motor 223 displacement is simultaneously switched to pump fluid from the high pressure accumulator 225 to the cylinder assembly 221. The boost/reduce switch 214 is shown to be on the same side as that shown in FIGURE 7, which reflects the change of view of the fluid flow through the switch from power-stroke "reduce" to return-stroke "boost".

During the return stroke, if the pressure of the high pressure accumulator 225 is higher than the pressure of the cylinder assembly 221, the computer sets the boost/reduce switch 214 to "reduce", and designates the upper motor 223 as the driving motor, as shown in FIGURE 9. The motor inlet is connected to the high pressure accumulator 225 and the outlet to the cylinder assembly 221. The pow er of motoring is used to drive the lower motor 222 in regenerative mode to pump fluid from the low pressure accumulator 224 to the cylinder assembly. The boost/reduce sw itch 214 is shown to be on the same side as that shown in FIGURE 6, which reflects the change of view of the fluid flow through the switch from power-stroke "boost" to return-stroke "reduce".

The aforementioned FIGURES 6 - 9 are the switching states for what is known in this document as a Class A fluid power transformer where both motors 222, 223 are capable of operating in regenerative mode according to displacement set by the control computer 231. It may be preferable to use a pump in place of the regenerative motor, inter alia, a pump may be more efficient than a motor driven in regenerative mode, and to switch the pump into the regeneration motor location each time regeneration is required. In accordance with the present invention this can be done by inserting a fluid transposing switch ahead of the motor and pump as shown in FIGURES 10-13 and toggling the transposing switch (indicated at 310 in these figures and having four individual valves 311-314) such that the pump is always in the position of the regenerative motor as evidenced by comparing FIGURE 10 to FIGURE 6; FIGURE 11 to FIGURE 7; FIGURE 12 to FIGURE 8; and FIGURE 13 to FIGURE 9. The following FIGURE 10-FIGURE 13 show that the fluid transposing switch 310 makes it possible to use the most efficient rotating equipment available, in what is known in this document as a Class B fluid pow er transformer, without any loss of flexibility, functionally identical to figures FIGURE 6-FIGURE 9, and independent of other functions of the inventive WEC. It is shown in FIGURE 10 that the fluid transposing switch 310 is in the transpose position Each of the four fluid switches 311-314 are connected to transpose motor 323 and pump 322 to align with the motor and regenerate e terminals to the configuration shown in FIGURE 6 It is shown in FIGURE 11 that the fluid transposing switch 310 is in the straight though position and no transposition is required Each of the four fluid switches 311-314 that make up switch 310 is connected straight through to the motor 323 and pump 322 to the configuration as shown in FIGURE 7

It is shown in FIGURE 12 a transposition of sw itches 311-314 is required so that the motor 323 and pump 322 are in the same configuration as the motor and regenerate e motor in FIGURE 8

It is shown in FIGURE 13 that no transposition is required as the motor 323 and pump 322 are in the same configuration as the motor and regenerate e motor in FIGURE 9 The fluid transposition switch has an auxihan function, that of transposition switching the electrical sensors and displacement controls for the motor and pump simultaneous with the fluid transposition This requires a tw o-position double-throw switch of the requisite number of poles, plus auxihan contacts to control the fluid transposition switch It is preferable that this electrical switching be done entireh within the control computer, where the first part of an algorithm performs the electrical sensor and displacement control transposition, and the second part, the fluid line transposition, is done b} an electrical pulse to each \ al\ e 311-314 in the fluid transposition switch 310

It is apparent from the discussion of FIGURE 6-FIGURE 13 that the tw o in\ entπ e fluid pow er transformers (Class A and Class B) are functionalh equi\ alent. and w ould perform equalh w ell for the four main operating conditions, boosting and reducing pressure in the pow er-stroke and return-stroke It ma> be preferable to reduce the low pressure accumulator 224 to atmospheric pressure reserv oir 226 A tw o-position double-throw fluid \ al\ e switch 216 (seen in FIGURES 6-10) at the inlet to a charging pump 516 is switchable to allow the low pressure accumulator 224 to communicate through pipe 208 w ith the oil reseπ oir 226 at atmospheric pressure

In the conv ersion of fluid power to electric pow er generation, it is preferable during the pow er-stroke to send about half the fluid energ} directh through on-off switch 215 to the hy draulic motor that pow ers the electric generator and thus a\ oid the power transformation losses that would otherwise occur if all the energy was sent to storage and then drawn back for generation. A fluid power switch 215 inserted into the cylinder assembly line 202 is kept open for direct generation during power-stroke as shown in FIGURES 6, 7, 10 and 11, and kept closed during return-stroke as shown in FIGURES 8, 9, 12 and 13.

The generator 510 is preferably powered by two hydraulic motors 511, 512, rotatabry coupled as indicated at 513, at least one of which is supplied directly from the cylinder assembly during the power-stroke through an open valve 215 as shown in FIGURES 6, 7, 10 and 11. The second motor is switchable to lead the change-over to operate from the high pressure accumulator 225 during periods of transition, which is at a different pressure than the flow from the cylinder assembly 221 via line 201. These hydraulic motors are operated at constant speed for constant frequency electric power generation. The cylinder assembly valve 215 is closed at the end of the power-stroke and fluid is then supplied from the accumulator 225 for the duration of the return-stroke and during periods of piston inactivity. The computer program has a forward looking state- estimator algorithm to estimate the stead} level of power that can be produced for a particular on-coming wave condition and determines the best estimate for the power production settings. Such optimal control and optimal state estimator features are known to be programmable in state-of-art computer PLC and DCS systems. Power is imported from the utility system on shore, or from a motor-generator set. over the under water cables to an electrical box 514 (FIGURES 6-10) to start the WEC into operation. Electrical control lines connect the control computer 231 to a computer on shore. A small electric start-up motor 515 drives a pump 516 to charge the accumulators and hydraulic equipment from a reservoir 226. Sufficient power is imported to operate the electric motor-pump-set to charge the high pressure accumulator 225 to build up an energy reserv e sufficient to run the WEC 10 through a few power-stroke return-stroke cycles and give the computer algorithms time to adjust to ocean w ave conditions. After fluid energy in the high pressure accumulator 225 is considered sufficient to sustain continuous electric power production, the fluid line to the turbine is opened, the hydraulic turbines 511, 512 are started and electric generator 510 is brought up to speed and synchronized at the electrical control panel 514. Power is exported to shore by increasing turbine displacement to increase power generation. Another embodiment of fluid transfer arrangement for further efficiency enhancement, known in this document as a fluid energy swing, from the power stroke to the return stroke, is shown in FIGURE 14 and FIGURE 15. In the power stroke (FIGURE 14), a first group of piston driven cylinders 221a communicates through line 421 to two-position fluid valve 414 and line 423-424 to a separate accumulator 425, storing energy from the power stroke to provide energy for the return stroke without incurring loses from fluid pressure transformation. The fluid energy swing is adjustable from approximateh 0 to 100% of the energy required to return the piston to its top position, depending on numbers of cylinders (each w ith a single-pole double-throw fluid switch 414) in the group and accumulator pressure. The second group of cylinders 221b communicates through fluid line 201 to the fluid power transformer similar to that shown in FIGURES 6-13. FIGURE 15 shows the conditions during the return stroke.

The modified fluid transmission circuit shown in FIGURE 16 has the assembly 221 of piston driven cylinders divided into three groups. Power stroke conditions are illustrated in FIGURE 16. The first cylinder group 221a communicates through conduit 421, valve 414, conduit 423, valve 415, and conduit 424 with the additional accumulator 425. As for the embodiment of FIGURES 14 and 15, charging pressure in accumulator 425 on the down stroke can be recaptured on the return stroke. A second cylinder group 221b communicates w ith the fluid pressure transformation pair 222 and 223, similar to the embodiments of FIGURES 6-13. A third cylinder group 221c communicates directly w ith the high pressure accumulator 225, i.e., by way of line 207, so as to transfer fluid directly to such high pressure accumulator. Thus, the first group 221a functions independent of wave action as if the piston is simply translating up and down, pressurizing the additional accumulator 425 on the power stroke and using this pressure on the return stroke. The third group 221c operates as a base load group where fluid pressure is transmitted directly to the high pressure accumulator on the power stroke without using the pressure transformation motor-pump pair 222, 223. The second group 221b is a residual flow group which transmits the balance of the energy in the ocean wave, some of which goes directly to drive electricity generation through line 202 and valve 215 (valve 215 being open during the power stroke and closed at other times).

A simple flow diagram of operation of all embodiments of the wave energy conversion system in accordance w ith the present invention is shown in FIGURE 17. The sensor array positioned seaward of the WECs detects wave characteristics as indicted at box 600. The control computer reads data from the sensors and computes the w ave vectors and analyzes the useful energy of the on-coming w ave, as indicated by box 602. The control computer then evaluates the operating characteristics of the WEC and. in combination with the wave characteristics calculated from the sensor data, makes a decision as to whether or not the on-coming w ave is appropriate for energy harvest. If not, no additional action is taken and the next w ave is analyzed, as indicated by line 605. On the other hand, if it is determined that the w ave is appropriate for energy harv est based on its energy and the operating condition of the WEC, the power stroke is instituted (box 606) and continued to the optimal lower most position of the piston. For example, for a representative w ave train the WEC deflector may be raised and tilted to its energy capturing position at approximately 10 degrees to 30 degrees prior to alignment with the w ave crest. At the end of the power stroke, the WEC is returned to a "hold" condition with the main supply valve closed and the electric brake applied (box 608), until the appropriate time for instituting the return stroke (box 610), which could occur for example, at 10 degrees to 30 degrees prior to the wave trough passing over the WEC. Between the end of the power stroke and the beginning of return stroke, the deflector is lowered so as not to interfere w ith expulsion of seawater from the WEC. At the end of the return stroke, the system again is placed in the "hold" condition (box 612; electric brake applied and main supply valve closed) and the system recycles to analyzing the next on-coming w ave.

The aforementioned drawings and discussion have been simplified to assist in comprehension with some details omitted for brevity. A WEC operates continuously when waves are favorable, making it cost-effective to apply high efficiency hydraulic equipment and computer technology to the maximum extent possible. It is known that it is preferable, for greatest efficiency and flexibility, that for optimal state estimation all possible parameters be measurable (accessible and observ able) to formulate the computer model for optimal computer control. A comprehensive computer model includes motor speed and fluid displacement indicators, fluid pressure and metering sensors, and fluid valve position indication at all possible points of measurement. It is known good practice for example, that auxiliary contacts on electrically operated devices such as fluid valves in this case, ensure that the devices have responded as required and are in the required position. The hydraulic motors and pumps are preferably the full-range reversible type. actuated with electronic signals, with displacement indicators. The computer on board the WEC is subordinate to a master computer on shore, allow ing the master computer to log, review and improve the performance of the slave.

The w ave energy conversion system in accordance with the present invention is essentially a computer controlled wave energy harvesting device that relies on a state estimator model of an incoming w ave, as determined from pressure transducers on the ocean floor, to set the strategy for the harv esting of each w ave cycle. The WEC=S, forw ard looking, discrete switching synchronizes itself to the w aves coming on shore, and adjusts itself to harvest only those w aves with energy above a predetermined threshold. The system of the present invention lends itself to use for creating w aves for recreational purposes in addition to harvesting w aves for energy generation. In the case of w ave creation, energy for operating the WEC piston conies from shore. If small recurring w aves are present, the WECs are positioned and timed for expelling w ater upw ard and. if deflectors are used, shorew ard in a calculated sequence that progressively increases w ave height and volume. The principles are the same but the energy flow is opposite. When starting a w ave in a calm sea. calculation can be based on creating an imaginary horizontal drum of water and setting it in rotation tow ard the shore, slowly accelerating it in a forward direction. As the imaginary drum passes over a series of WECs, the pistons are reciprocated so as to create a longer drum or w ave front with additional row s of WECs similarly configured.

While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

CLAIMSThe embodiments of the invention in w hich an exclusive property or privilege is claimed are defined as follows:

1. A system for converting energy from recurring ocean waves, said system comprising a w ave energy converter and a control computer, said w ave energy converter comprising; a shell having a circular or a elliptical inner surface about an upright center axis, with a closed bottom end. fixed with relation to the ocean floor, and a top end open to the sea above; a converter piston co-axial within the shell, moveable up and down therein, and defining a gas filled chamber between an underside of the piston and the bottom of the shell, the chamber being vented to atmosphere; a flexible reliable annular seal between the inner surface of the shell and the piston, the seal being secured to keep sea water out of the gas filled chamber vented to atmosphere, below the piston, the piston being moveable axially in the shell in response to variations in water pressure on the piston as ocean w aves pass over; an assembly of hydraulic cylinders below the piston and connected thereto so as to pump fluid through a hydraulic fluid system as the converter piston reciprocates up and down with crest and trough of waves passing over, the hydraulic fluid system including at least one accumulator component, and a fluid power transformer component having a fluid piping network, including a two position fluid switch, a first motor, and a second motor rotatably coupled to the first motor, one of the motors being operable in regenerative mode, all of said components being connected to communicate fluid w ith the cylinder assembly; means for converting energy in the hydraulic fluid system to electric energy; said control computer having means offset seaward from the wave energy converter for sensing physical features of on-coming waves and being programmed to control operation of the w ave energy converter as a function of the w ave features sensed.

2. The system defined in Claim 1. including means adjacent to the shell for deflecting horizontal w ave forces downward onto the piston, the deflecting means being movable relative to the shell between a position at least partially overlying the piston and a position not overlying the piston, the wave energy converter and the control computer including means for adjusting the position of the deflecting means based on the position of an in-coming wave crest and associated wave trough.

3. The system of Claim 1. in which the hydraulic fluid system includes at least one accumulator connected so as to be pressurized as the piston reciprocates and connected under control of the control computer to supply fluid under pressure to a hydraulic motor driving an electric generator.

4. A system for converting energy from recurring ocean waves, said system comprising a wave energy converter comprising; a shell having a circular or a elliptical inner surface about an upright center axis, with a closed bottom end. fixed with relation to the ocean floor, and a top end open to the sea above; a converter piston co-axial within the shell, moveable up and down therein, and defining a gas filled chamber under the piston, the chamber being vented to atmosphere; a flexible rollable annular seal between the inner surface of the shell and the piston, the seal being secured to keep sea water out of the gas filled chamber vented to atmosphere, below the piston, the piston being moveable axially in the shell in response to variations in water pressure on the piston as ocean waves pass over; an assembly of hydraulic cylinders below the piston and connected thereto so as to pump fluid through a hydraulic fluid system as the converter piston reciprocates up and down with crest and trough of waves passing over; means adjacent to the shell for deflecting horizontal wave forces downward onto the piston, the deflecting means being movable relative to the shell between a position at least partially overlying the piston and a position not overlying the piston; and means for adjusting the position of the deflecting means based on the position of an in-coming wave crest and associated wave trough.

5. The method of converting energy from recurring ocean waves, which comprises: positioning pressure sensors adjacent to the sea floor beneath the area of recurring ocean w aves and using the sensors to measure the changing pressure as w ave crests and troughs pass over; using a computer to calculate w ave vectors and analyze energy of one of the w aves; using the computer to automatically control operation of a w ave energy converter located shoreward from the position of the sensors, such w ave energy converter having a piston oriented for up and down movement under pressure from w aves passing over and a hydraulic system including hydraulic cylinders operated by reciprocating motion of the piston; holding the piston in an upward shifted position until such time as a w ave crest is over or nearly over the piston and then automatically releasing the piston for downward motion in a power stroke to pressurize fluid of the hydraulic cylinders; using the pressurized fluid to operate an energy conversion system including at least one rotary hydraulic motor and at least one rotary electric generator driven thereby; thereafter automatically holding the piston in the downward position until a w ave trough is over or nearly over the piston and then automatically releasing the piston and returning it to the upward shifted position by pressure of the hydraulic system.

6. The method of generating ocean w aves, which comprises: using a computer to automatically control operation of a multiplicity of underwater w ave energy converters each having a piston oriented for periodic up and down movement by operation of a hydraulic system including hydraulic cylinders connected to the piston, reciprocating motion of the cylinders and piston being controlled by the computer to force water above the piston upward; and monitoring wave production and movement, and timing reciprocation of the pistons to amplify a w ave as it approaches and passes over the w ave energy converters.