CA2408855A1 - Ocean wave energy converter - Google Patents

Abstract

An ocean wave energy converter means for powering an electric generating system said converter comprising a chamber with the bottom end closed and resting on the ocean floor, with top end open to the sea above, and a reciprocating piston with an annular seal to keep sea water out of a gas filled chamber below, vented so to operate near atmospheric pressure, free to move axially in response to pressure changes as ocean waves pass over.
The invention, positioned below wave trough level at a location of significant wave height near a shoreline, converts potential and kinetic energy of recurring ocean waves into electric energy by way of a system of hydraulic-cylinders, -accumulators, -motors and -pumps, and electric generators. A power transfer medium is connected from the ocean wave energy converter to a receiving device onshore in the nature of an electric customer or an electric utility.

Description

1 Description 3 1. Field of Invention:

4 The present invention relates in general to systems for harnessing and converting energy from recurring ocean waves to electric energy. More particularly it relates to those 6 systems that use hydraulic fluid means as the medium for energy exchange.
The simplest 7 and most minor of these prior art devices comprises a float on the ocean surface far 8 offshore that reciprocates a piston in a hydraulic cylinder fixed to the ocean floor and 9 pumps fluid to a hydraulic motor to rotate an electric generator for power production. The most elaborate and most major of these devices is an assembly of different size floats 11 hinged together into a floating platform moored near shore, that is configured to be 12 responsive to almost all wave lengths and frequencies. It is meant to recover almost all 13 the energy of a ocean wave by seemingly damping all the energy out of all sizes of the 14 waves and converting the energy to hydraulic fluid energy through movement of the cylinders by articulation of hinges connecting the floats.
16 In the context of the present invention "switching state" means a particular set of control 17 valve positions that facilitate hydraulic fluid flow during the power production cycle as 18 shown on a schematic drawing 19 Also, in the context of the present invention "fluid power transformer"
means a device that transforms fluid power from one combination of pressure and flow combinations at the 21 input terminals to another combination at the output terminals, analogous to an electric 22 power transformer. An ideal fluid power transformer means one with no power losses.
23 Also, in the context of the present invention "terminal" or "tine terminal"
means a 24 connection point on a hydraulic fluid device such as input terminal means a point of flow into a device such as a fluid power transformer, also known as inlet port and outlet port.
26 Also, in the context of the present invention "ocean ~ivave degree" means a unit of 27 measurement in units of time or distance, equivalent to the period of an ocean wave 1 divided 360, the number of degrees in a wave cycle, and is analogous to the degrees-2 before-top-dead-center scale on an engine block associated with ignition timing for 3 internal combustion engines.
4 Also, in the context of the present invention "vector drive" means a control scheme for 5 transmitting energy through a "fluid power transformer" during the power-stroke-return-6 stroke power production cycle.

7 2. Background of the Prior Art 8 The world's oceans and large lakes contain large amounts of wave energy. For almost 9 as long as there has been electric power, approximately 100 years, inventors have tried to harness ocean waves as an alternative source of renewable electric energy.
Generally 11 speaking almost all these inventions were not cost-effective because too little energy 12 could be produced for assets employed. Also the ocean can suddenly turn into an 13 extremely hostile environment commonly known to capsize even massive floating offshore 14 oil production platforms thought to be securely anchored to the ocean floor.
Inventors such as Schroeder US Pat. 4,622,471 and Nedyalkov US Pat. 4,345,434 have 16 developed apparatus for producing electric power from ocean waves by in effect rectifying 17 the ocean waves by drawing seawater into a high chamber through a high level inlet from 18 the wave crest, and passing it through a turbine into a low chamber with a low level outlet 19 that discharges it into the wave trough, with the result that the turbine operates at a head nearly equal to the wave height above the trough. The requisite massive floating structure 21 is particularly vulnerable to breakup in ocean storms. Others have developed apparatus 22 that use air chambers which are usually installed at or near shore. These structures are 23 massive in relation to the electric energy generated because the air speed through the 24 turbines is relatively very low compared to gas turbines generally. Also the power generated pulsates at twice the frequency of the ocean wave as air is pushed through the 26 turbine with the rise of the crest of the wave and sucked back by the wave trough. This 27 power fluctuation must be smoothed because it would cause voltage flicker in the utility 28 distribution system.

1 Other inventors have developed apparatus to convert ocean wave energy directly to 2 electrical energy in a seemingly efficient single step. The electrical devices in their 3 disclosures appear complex and prone to high maintenance in a sea water environment, 4 and costly to service because they require a deep water environment which would place them substantially offshore. Woodbridge US Pat. No. 6,020,653 shows a wave power 6 generator comprising a float on the ocean surface that reciprocates a coil in an armature 7 fixed to the ocean floor and from there presumably to a power conditioning device on 8 shore. The electric power generating device on the ocean floor generates power of 9 varying amplitude and frequency. Also the voltage is probably not sinusoidal.
Transmission losses would be substantial at low voltage. Woodbridge US Pat.
No.
11 5,696,413 is similar but near shore and mounted above the surface. Such electric 12 generating devices transmit energy by way of a magnetic field across an air gap and thus 13 are able to transmit only a small fraction of the force from the float on the ocean surface 14 compared to a high pressure hydraulic cylinder. There appears to be no cost-effective direct electrical conversion apparatus that could be built near shore in sufficient scale to 16 generate substantial quantities of electricity from ocean waves.
17 It has long been known that a hydraulic fluid system was an effective medium for 18 converting ocean wave energy to electric energy. This hydraulic interface type of system 19 can be seen in prior art systems which use wave motion to drive a hydraulic pump to force fluid through a turbine connected to an electric generator, both near shore and offshore.
21 The most major invention that utilizes hydraulic cylinders to pump fluid through a turbine 22 and generate electric power is described in USRD03111. It is an assembly of different 23 size floats hinged together into a floating platform moored near shore, that is configured 24 to be responsive to almost all wave lengths and frequencies. It is meant to recover almost all the energy of a ocean wave by seemingly damping all the energy out of all sizes of the 26 waves and converting the energy to hydraulic fluid energy through movement of the 27 cylinders by articulation of hinges connecting the floats.
28 The closest art found to the present invention is shown on page 3-2 of a report entitled, 29 " Wave Energy Resource and Economic Assessment for the State of Hawaii u, Final 1 Report June 1992, principal investigator: George Hagerman, Seasun Power Systems.
2 This device comprising a float inside a cylinder with top closed, operably connected to a 3 hydraulic cylinder mounted on the top side of said cylinder, that reciprocates with ocean 4 heaves and pumps hydraulic fluid. However even this prior art teaches the use of a surface float to operate a hydraulic fluid cylinder and is not as effective an energy 6 concentrator as my invention. The force transferred to the hydraulic cylinder is limited to 7 the force of displacement of water by the float, in other words the product of the cross 8 sectional area and thickness of the float. In my invention the full force of the entire 9 column of water above the piston up to the wave crest bears down on the converter piston and is transferred to hydraulic fluid cylinders. Additionally with my invention, the force on 11 the converter piston can be made to include the effect of supercharging by converting 12 kinetic energy into downward force on the piston.
13 The aforementioned Hagerman report is a comprehensive authority that summarizes the 14 best state of the art ocean wave energy conversion devices prior to its date of publication in 1992.
16 Since 1992 there appear to be no patents of any apparatus or method of obtaining power 17 from ocean waves, that utilizes hydraulics and advances the state of art of ocean energy 18 converters. There are a number of floating oscillating water column type devices and 19 floating inclined ramp type devices. Floating devices are vulnerable to capsizing under heavy ocean storms. A recent invention of Wells US 6,194,791 B1 issued 27 Feb 21 teaches an oscillating water column type power converter configured to be floated out to 22 sea and attached to the ocean floor in shallow water near shore.
23 An overview of the prior art of ocean energy power conversion can be had by perusing 24 the following web sites:
www.eren.doe.gov/RE/ocean wave.html;
26 www.energy.ca.gov/education/story/story~html/ chapter08.html;
27 www.europa.eu.int/en/comm/dg17/atlas/htmlu/ wavint2.html; and 28 www.waveenergy.dk/apparater/engelsk_klassificering.html 1 No prior art found by the inventor teaches the advantages of a large scale direct acting 2 energy converter device resting on the ocean floor, totally submerged below the wave 3 trough with a vent to surface atmosphere. Nor is there any prior art that teaches a 4 converter that can hunker down to avoid breaking up when under attack by heavy ocean storms. Wells device US 6,194,791 B1 is probably vulnerable to being overturned by 6 extremely high waves. Whereas with my invention, extremely high waves will pass over 7 and only the pressure surge will be felt by my wave energy converter.

It is a broad object of this invention to provide an ocean wave energy converter capable 11 of being utilized in shallow water close to shore adjacent to where the energy will be 12 utilized.
13 The guiding principle of this invention is to maximize electric power generation for assets 14 employed, rather than to try to recover all the energy in an ocean wave.
To appreciate the potential and comprehend the operation of this invention one needs 16 only to be familiar with the operation of internal combustion engines, fluid power systems, 17 and electric power systems, particularly hydro-electric power generation.
The invention 18 can be characterized as like a single cylinder engine with an large piston, submerged 19 near shore, that pumps electric power from the bottom of the sea without noise or pollution of any kind.
21 The teachings of this invention can best be explained by reflection on hydro-electric 22 generation, one of the earliest forms of large scale generation, which over time has 23 remained the preferred method of electrical supply. It is economic, renewable and free 24 of greenhouse gas emissions.
High head, high water pressure turbine-generator plants are generally the least costly on 26 a unit of energy basis, and least obtrusive particularly when the powerhouse is 27 underground, excavated from a mountain side, where water flows from the reservoir 1 through an intake tunnel down a penstock to a high pressure pelton turbine and 2 discharges through a tunnel to a stream nearby. Such plants are remarkable for how little 3 water is required to produce a large amount of electrical energy. In such plants where the 4 head is typically a few thousand feet, the turbine is much smaller and much higher speed than turbine-generators in run-of-the-river plants which are typically less than 100 feet of 6 head. Hydro-electric plants commonly use pumped storage to bank energy to be recalled 7 days or months later when load conditions are more compelling, and to transfer hydro 8 resources from adjacent catchment basins to the main reservoir to maximize generation.
9 With these systems the hydro-logical cycle is usually one year. Reservoirs are generally sized to be larger than necessary to capture run-off in an average water year.
During 11 years of prolonged drought, commonly known as critical water years, when reservoirs can 12 not be fully refilled, dependable electric energy capability is reduced substantially.
13 More particularly this invention is analogous in several respects to a very high-head 14 hydro-electric generating plant with an underground powerhouse. It is hidden from view by virtue of being fully submerged at low tide. It is also capable of collecting energy from 16 surrounding resources and storing it in an accumulator which functions like a hydro-17 electric reservoir and serves to smooth out power output. An accumulator is comprised 18 of a large free moving piston in a long cylinder, on one side of which is hydraulic fluid and 19 on the other side high pressure nitrogen gas connected to a plurality of gas pressure vessels.
21 The economies of a high head energy supply are achieved by way of a high ratio pressure 22 amplifier feature inherent in the power conversion device which amplifies the relatively 23 small pressure change of an ocean wave into a hydraulic fluid pressure several times 24 higher than maximum design pressure for a pelton turbine. Compare for example say a 23 foot head ocean wave, measured crest-to-trough, to a 2,300 foot head hydro-electric 26 plant. The pressure of 23 foot head, equal to about 10 psi, is amplified to about 6,000 psi 27 then applied to a hydraulic motor which drives a generator. A head of 2,300 feet is 28 equivalent to about 1;000 psi. In terms of pressure at the prime mover, this invention 29 compares with a 13,800 foot head hydro plant, ideal for producing high electric energy per unit mass. In this example, if the output was 1,000 psi, the overall gain would be 60.

1 Furthermore, the pressure amplifier feature inherent in the energy converter has an 2 adjustable gain. In this illustrative example, with 10 psi input and output set to 6,000 psi, 3 the gain is 600. The high pressure accumulator, operating in the range of 3,000 to 6,000 4 psi, functions analogous to a deep hydro plant reservoir with steep side slopes, with 5 bottom (empty) at 6,900 feet and top (full) at 13,800 foot elevation. Energy is stored in 6 the accumulator in increasingly concentrated form, directly proportional to increasing 7 pressure. When conditions are such that the extra reservoir capacity is unnecessary, or 8 it is more efficient or cost-effective to operate at some lower pressure, it is readily possible 9 to operate at say between 1,000 psi and 3,000 psi, analogous to a hydro reservoir with 10 a range of 2,300 to 6,900 feet of head above the power turbines.

11 Consider, it is common for~a hydro-electric utility to have a mix of peaking plants and base 12 load plants side by side supplied from a common reservoir. With this invention the large 13 energy converter units operate intermittently like peaking generation and rely on heavy 14 ocean waves for efficiency. Some hydro-electric peaking plants operate the equivalent of only 5% of the time at full output, commonly known as a capacity factor of 5%. Small 16 units of this invention can operate continuously like base load generation running at full 17 output over the entire range of small to large ocean waves. During large waves the head 18 above the energy converter is higher giving the power stroke higher force but the stroke 19 frequency is lower so the extra energy needs to be stored for a longer period so amount of power generated can be maintained about the same. It is preferable to increase the 21 storage pressure to the higher pressure of each power stroke.
22 The hydro-logical cycle is analogous to the period of an ocean wave. Waves persist with 23 great regularity since they open ocean is set in motion by winds from thousands of miles 24 away. There is no prolonged shortage of energy supply to impact on production like a long period of drought impacts on a traditional hydro-electric system, only short periods 26 of relative ocean calm. Critical-water conditions are reduced from years in a hydro-27 electric system to hours or days in my wave energy conversion system, and can be 28 mitigated by banking energy in the high pressure accumulator well in advance of changing 29 ocean conditions, in response to a marine forecast.
:, .:
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1 Unfortunately this invention is only on about one thousandth scale of large hydro-electric 2 plants. The largest hydro-electric generator today is about 1,000 megawatts, whereas the 3 largest possible hydraulic motor-generator combination realizable today is about 1 4 megawatt, limited by the size of hydraulic motors currently manufactured.
This invention is on the scale of traditional small hydro plants. Nonetheless, it has a major advantage 6 in that many times more ocean wave energy potential can be developed compared to all 7 traditional hydro-electric generation. The ocean is a renewable resource of seemingly 8 endless supply with potential power up to tens of kilowatts per foot of ocean front. A large 9 number of energy converter units can be readily deployed along a shoreline to create a substantial energy supply.
11 It is an object of the present invention to capture energy from recurring ocean waves by 12 converting the potential energy of the crest of the wave into axial motion of a large piston 13 in an open top curved chamber, where seawater presses on the top side of the piston onto 14 hydraulic cylinders attached on the underside of the piston like connecting rods in a internal combustion engine. The hydraulic cylinders pump fluid around a loop that powers 16 the electric generators. The invention has a two stroke cycle, power-stroke and return-17 stroke.
18 As the wave crest moves over the top of the piston, seconds in advance of the axis of the 19 crest aligning with the axis of the piston, say 30 - 35 ocean wave degrees in advance of top-dead-centre, hydraulic valves are opened to allow the piston to move with maximum 21 force through the power stroke, similar to that of an engine wheri ignition is applied 30 -22 35 mechanical degrees in advance of top-dead-centre for optimum combustion.
Similarly 23 seconds before the wave trough axis aligns with the piston"axis, valves are switched, flow 24 is reversed and the hydraulic cylinders return the piston to the top of the converter chamber and discharge the seawater like an engine discharges exhaust gases.
When 26 wave heights are less thari maximum the converter is designed for, the stroke is reduced 27 so as not to waste energy on the return stroke. For example in a calm sea, the energy 28 converted during power stroke equals the energy consumed to reset the piston to top 29 position. In fact, because of system losses, energy needs to be drawn from storage. It is analogous to losses with an idling engine.

1 This variable stroke feature is analogous to the displacement-on-demand feature recently 2 announced by General Motors for their next generation of efficiency improved motors for 3 trucks, where it is claimed under light load conditions up to 4 cylinders of an 8 cylinder 4 engine will shut down automatically to reduce losses and thereby improve efficiency up to 25 percent.
6 Going now to the mechanics of my invention. Force times distance equals energy. A
7 stroke with a force of 55 pounds through a distance of 10 feet equals 550 foot-pounds;
8 550 ft-Ibs/sec equals 1 horsepower. 33,000 ft-Ibs equals 1 hp-min; 44,236 ft-Ibs equals 9 1 kW-min. An accumulator operating at 6,000 psi stores 1 kW-min of fluid energy in 88.47 cubic inches of volume. Consider a single elliptical energy converter about 40 feet wide 11 by 20 feet deep with a piston surface area of 600 square feet; a stroke of 10 feet; an 12 overall efficiency of 64 - 80%; in a sea with a head of 6 feet crest to trough with a wave 13 period of 10 seconds. Energy generated by the piston equals 52 to 65 kW-min per stroke 14 --- approximately 2.66 cubic feet of accumulator volume at 6,000 psi. Under these conditions power output is in the range of 312 to 390 kilowatts.
16 The energy converter can be mounted directly on the ocean floor, or alternatively on a 17 tripod base configured to the ocean floor, and anchored to the seabed to Withstand heavy 18 ocean storms. The invention automatically hunkers down to avoid damage during severe 19 ocean storms. In a worst case scenario, an extremely high wave could otherwise over pressure the hydraulic system, cause a line to rupture and the converter piston to slam 21 down on its bottom stop.
22 This invention can be configured into a dynamic breakwater by arranging several large 23 units in an array of two or more rows running parallel to the shoreline, one row offset from 24 the other by half the spacing between units. Thus the extreme energy can in effect be combed out of the wave.
26 The invention includes accost-effective add-on device which converts kinetic energy to 27 extra head to increase electric power production. The kinetic energy of an ocean wave 28 is a function of its mass and velocity, where mass is apparent from wave height. The 29 relationship between kinetic energy and potential energy [ '/Z (mv2 ) = mgh ] can be 1 reduced to equivalent wave height and velocity [ h = v2 / (2 x g) ]. The kinetic energy of 2 a unit of mass moving in an ocean wave at 10 mph or 15 fps {where g = 32.2 fps/s) is 3 equivalent to about 3.5.feet of head; 20 mph to 14 feet; 30 mph to 31 feet;
and 40 mph to 4 56 feet of head.
Additional kinetic energy can be converted by initiating a wave surge above the piston.
6 Consider as units of mass are slowed as they come in contact with the piston, other units 7 push from behind, increasing pressure on the piston, much like trailing boxcars add force 8 to leading boxcars when a freight train strikes a barrier. Raising the barrier into place at 9 the appropriate time so this train of units of kinetic energy surges directly above the piston would further enhance energy conversion. Several such unit trains of kinetic energy 11 moving in parallel can be deflected to converge above the piston to further enhance the 12 conversion of wave energy to useful energy.
~i>
13 It is an object of the invention to capture kinetic energy of ocean waves by tilting the 14 piston axis in the direction of the incoming wave, exposing the cylinder opening to the on-coming wave, thereby deflecting horizontal motion down onto the piston and increasing 16 energy conversion, herein called a stage 1 supercharger. It is an object in the alternative 17 to said tilting the piston axis, to construct the cylinder so that the top of the shore side 18 edge is higher than the ocean side edge and the height difference, herein called the 19 window opening for capturing kinetic energy, is the same as if the axis was tilted, except that the piston chamber opening is elliptical rather than circular, the piston surtace area 21 remains the same.
22 Another object is to capture kinetic energy of ocean waves with an adjustable externally 23 mounted deflector positioned on the shore side of the energy converter, set so as to 24 deflect seawater down into the cylinder and increase pressure on the piston and thereby increase power conversion, herein called a stage 2 supercharger. The stage 2 26 supercharger is alternatively rotatably mounted on the converter so the axis of its opening 27 is automatically pointed directly into the oncoming wave for maximum efficiency. Or 28 extensions mounted along the cylinder circumference.
29 An additional object is to enhance kinetic energy conversion by an externally mounted 1 deflector on the ocean side of the converter set so as to deflect seawater up to increase 2 wave height as it passes above the piston, herein called a stage 3 supercharger. This 3 can be done by arranging ballast along the front of the converter.
4 It is a further object of the invention to combine the aforementioned supercharger means and control the deflector devices to increase pressure on the piston and thus increase 6 power production like a supercharger on an internal combustion engine compresses 7 intake air before it is mixed with fuel and applied to the piston thus boosting energy of 8 combustion in the same displacement volume resulting in higher power output for the 9 same engine mass, commonly known as supercharging the engine. All three aforementioned piston pressure increasing means operating simultaneously are herein 11 called a 3-stage supercharger.
12 Some new analytical concepts are introduced here to help explain how the fluid power 13 transformer operates within the vector drive as the energy converter goes through the 14 power-stroke-return-stroke cycle Analysts commonly use fluid mechanics concepts to explain the operation of electric 16 power systems: Current is analogous to fluid flow; voltage to pressure, the force that 17 causes flow; and voltage drop to pressure drop. Current times voltage equals power, 18 specifically one amp times one volt equals one watt ( 1 a~x 1 v = 1 w ). In other words, a 19 flow of one amp through a voltage differential of one volt equals one watt.
This is herein called a unitized system of power measurement with a basis of 1 watt. Through a judicious 21 selection of units of fluid measurement it would be possible to have one unit of flow 22 through one unit of pressure change equal one watt of fluid power. However commonly 23 used units of measure do not lend themselves to this directly. One US
gallon equals 4 24 quarts and one US quart equals 0.946 liters; One bar equals 14.47 pounds per square inch (psi); and One Imperial gallon equals 4.54 liters.
26 It is necessary with the aforementioned units of measurement to apply a constant to one 27 unit of fluid power to equate it to one unit of electric power:
28 a) In US measure: A flow of 1 gallon per minute (gpm) through a pressure differential 1 of 1 psi equals 112.3 of one watt. [ 1 gpm x 1 psi x 2.3 = 1 w ].
2 b) In metric: A flow of one liter per minute (Lpm) times a pressure differential of one 3 bar (1 bar) equals 10/6 of one watt. [1 Lpm x 1 bar x 0.6 = 1 w ].
4 c) In Imperial: [1 gpm x 1 psi x 1.917 = 1 w ].
5 It would be possible to compute hydraulic power directly with only units of flow and 6 pressure, if the US gallon was 2.3 times larger; If the Imperial gallon was 1.917 times 7 larger; and If 1 bar was equal to 8.70 psi, (60 percent of what it is currently, 14.47 psi).
8 Then 1 gpm through a pressure change of 1,000 psi would equal 1 kilowatt;
and 10 Lpm 9 through a pressure change of 100 bar would also equal one kilowatt. Commonly available 10 transducers of fluid pressure and flow with output to millivolts and or milliamps can be 11 connected to a common kilowatt meter and power input or power output can be measured 12 directly just as if the hydraulic fluid device was an electrical motor, generator, or electric 13 transformer.
14 Electric system analysts commonly use the Per Unit system to compute voltage, current 15 and power flows in large power pools comprising many interconnected utilities serving 16 millions of customers over thousands of square miles, each with different operating 17 voltages, frequencies, etc. The Per Unit system is extended here into fluid power systems 18 to integrate the fluid power aspects of the energy converter with the electric power 19 aspects to maximize efficiency and power production from the integrated utility system.
It is expedient to compute energy stored in the accumulator in kWh when estimating 21 storage requirements for smoothing power output over the period of an ocean wave, and 22 when positioning energy converters on the ocean floor to minimize size of accumulators.
23 The Per Unit system is also used here to explain the operation of the fluid flow and 24 pressure transformer device which is the care element of what is herein called the vector drive.
26 All fluid power devices used in this invention are commonly available with small signal 27 electrical controls similar to that for devices commonly used in electric power systems, 28 making it possible to control fluid system operation with current state of the art power 1 system controllers with only minor software adjustments. Computerized power system 2 controllers commonly used in large scale electric utility power systems for many years are 3 now cost-effective for small power systems. It is thus possible to optimally control 4 hydraulic fluid power systems to meet power production objectives. Operators of ocean wave power generating plants can have the benefit of computer graphics to monitor the 6 state of the hydraulic systems.
7 Optimal control techniques are also commonly used in motor vehicles. The operation of 8 the main power piston of the present invention is analogous to a piston in an internal 9 combustion engine. Its optimal operation conjures terms like spark advance before top-dead-center, combustion monitoring, feedback to adjust the ignition timing for the next 11 power stroke to maximize efficiency, supercharging, displacement on demand, etc. In 12 high end automobiles the engine and transmission control systems seemingly learn as the 13 car is driven along and readjust to changing situations, a control strategy commonly called 14 sub-optimal adaptive control. The present invention capitalizes on state-of-the-art optimal control systems and computer graphics to maximize efficiency and for ease of monitoring 16 power conversion operation. It is advantageous to have an algorithm in the computer 17 control system that gives a running state estimate of the ocean wave as it approaches the 18 converter. This is easily achieved with state of the art computer control devices 19 commonly known as PLC and DCS controls.
It is a further object of the invention to pass the hydraulic fluid through a flow and pressure 21 fluid power transformer, herein called a fluid power transformer, which is the core 22 element of what is hereiri called a vector drive. The fluid power transformer serves to 23 transfer energy from and~~to the converter piston for the power-stroke and return-stroke, 24 and to boost energy to storage and generally minimize energy losses. Fluid flow from the power-stroke, represented graphically by a vector, is amplified to match pressure in the 26 accumulator as pressure gradually rises as energy is accumulated there.
Flow is 27 continually adjusted to optimally control piston velocity throughout the power-stroke to 28 minimize energy losses and maximize overall efficiently. Flow is also directed to a lower 29 pressure accumulator reserved for the return-stroke to minimize return stroke energy. At the bottom of the power-stroke, the fluid power transformer is switched to return-stroke 1 and the optimizing function repeated --- to minimize the energy expended to discharge the 2 sea water into the lowest point in the wave trough and return the piston to the top position 3 and await the wave crest to move into position, then open the valves to begin the power 4 stroke.
The fluid power transformer is essentially a high power, variable ratio hydraulic 6 pressure amplifier that can boost pressure and reduce pressure over the entire range of 7 pressure conditions, including forward and reverse flows. The fluid power transformer 8 is analogous to a variable ratio auto-transformer in an electric power system with voltage-9 increase (boost) and voltage-decrease (reduce) over the entire range, where power can flow in both directions with equal ease. The vector drive is the control system for the 11 energy converter which includes the accumulators and the hydraulic motors that drive the 12 electric power generators. In effect it takes ocean power in the form of alternating ocean 13 waves of variable frequency and converts it to alternating current electric power of 14 constant frequency to match that of electric utility receiving the power. A
vector drive in an electric power system, as it is commonly known, is a drive that takes power from a 16 constant frequency source and converts it to direct current power and then inverts it to 17 variable frequency alternating current power to drive an induction motor at a speed which 18 corresponds to the frequency of the power produced. In electrical systems switching of 19 voltage and current is extremely fast and the circuitry is such that inertia effects are minimized. Similarly, in this invention, inertial effects are minimized for fast response. The 21 converter piston is made strong yet especially light so it responds immediately when the 22 valves are opened to begin the power stroke, and momentum kept to a minimum allowing 23 the piston to be stopped quickly at the end of the power stroke and restarted quickly into 24 the return stroke to exhaust water from the converter chamber into the wave trough. The preferable configuration for the ocean wave energy converter 10 is where the piston and 26 the piston chamber are elliptical. An elliptical converter cuts a wider swath from the ocean 27 wave, has a shortened minor axis and is less limited by wave length. A
circular converter 28 becomes less effective as its diameter along the wave axis increases to about 1/4 wave 29 length.
The vector drive is suited to other applications requiring efficient storage and recovery 31 of regenerative energy. Energy in hydraulic fluid stored in an accumulator at 6,000 psi 1 is equivalent to 0.044 kWhIUSgaI. One US gal of hydrogen at 3,000 psi contains 8,057 ,;
2 btu, equivalent to 2.4 kWhlUSgal. With no hazard like hydrogen fuel and even only about 3 1 /50 kWh/gal, the vector drive is attractive for high frequency repetitive operations.
4 Another object of this invention is the ability of the ocean wave power conversion plant to boot itself up from a cold start like hydro-electric plants boot themselves up with a 6 small, so-called black-start diesel -generator set of just sufficient capacity to power the 7 stations' auxiliary devices to start a single turbine-generator unit, which then starts the 8 entire power station. Alternatively, black-start power is imported by way of a small 9 transmission line from another electric system nearby. In this invention power is drawn from shore via the power cable to supply a small electric motor-pump set just sufficient to 11 slowly charge the pressure accumulator to where it holds enough energy to reset the main 12 piston and restart power production should the plant have been drained of all its stored 13 energy such as in the case where the converter was hunkered down to wait out a heavy 14 ocean storm.
Another object of this invention is to provide a reliable electric energy supply with few or 16 no moving objects suspended in the seawater where they would be subject to corrosion, 17 costly maintenance and lengthy shutdowns for repairs.
18 Another object of the invention is to provide a maintenance free piston with a reliable, 19 friction free water tight seal. Maintenance can be facilitated tat sea with a portable pressure bell adapted to the top of the energy converter with an access conduit to a point 21 safely above the ocean surface. The design of the converter is such that it can be quickly 22 unfastened from its base and floated to a dry dock, or to a launching ramp and drawn out 23 of the water, for maintenance.
24 The present invention is a plurality of ocean wave energy converters set on the ocean floor near shore in shallow water with significant wave height. The invention is a 26 particular form of hydro-electric utility that draws its energy from recurring ocean waves.
27 These and other objects and advantages will become evident from the description when 28 taken in connection with the drawings.

1 FIG. 1 is a perspective view of a plurality of ocean wave energy converters positioned 2 near shore and connected by cables to a utility on shore.
3 FIG. 2 is an elevation view in cross-section of an idealized ocean wave showing two 4 energy converters: one under the wave crest drawing sea water in, and the other discharging sea water into the wave trough. The chamber below the piston is shown 6 vented to the surface.
7 FIG. 3 is a pie sectional view of a typical ocean wave energy converter showing the 8 internal arrangements in simplified form with the piston part way through a stroke.
9 FIG. 4 is an elevation view in cross-section of a typical ocean wave energy converter showing the rack holding 'the hydraulic cylinders.
11 FIG. 5 is a perspective view of the energy converter with the supercharger fully raised to 12 capture kinetic energy.
13 FIG. 6 is a side view of the energy converter shown in FIG. 5 together with a side view of 14 the tripod base shown in FIG. 7 on which it would be preferably mounted.
FIG. 7 is an axial sectional view of the energy converter mounting base shown in side 16 view in FIG. 6.
17 FIG. 8 is a schematic representation of the invention meant to be viewed in combination 18 with FIG. 9. The invention is shown broken down into three configurations:
a basic energy !, 19 converter 102; a basic energy converter with a hydraulic fluid system 106;
and a basic energy converter with a hydraulic fluid system and a turbine-generator bay 110. In FIG.
21 8 the devices are shown schematically connected to each other and to an electric utility 22 or electric power user onshore.
23 FIG. 9 is a detailed schematic arrangement of the hydraulic components in the energy 24 converters in the arrangements of FIG. 8.
FIG. 10 is a schematic representation of the fluid power transformer showing the hydraulic 26 motor and pump components in switching states for power stroke and return stroke.

1 FIG. 11 is a graphic representation of the fluid power transformer as it would appear on 2 a computer screen at an instant of time during the power-stroke and return stroke cycle.
3 FIG. 12 shows a flow control diagram of the fluid power transformer of the vector drive in 4 power stroke with pressure being boosted to accumulator 164.
FIG. 13 shows a flow control diagram of the fluid power transformer of the vector drive in 6 return stroke with power being drawn from accumulator 162.
7 FIG. 14 shows a flow control diagram of the fluid power transformer of the vector drive in 8 power stroke with pressure being boosted to terminal 152 also connected to accumulator 9 164 and from a lower pressure accumulator 162 terminal 150.
FIG. 15 shows a flow control diagram of the fluid power transformer of the vector drive in 11 return stroke with power being drawn from accumulator H2 to boost fluid from L1.
12 FIG. 16 is a top view of an elliptical embodiment of the ocean wave energy converter 10.
13 FIG. 17 is a perspective view of the elliptical embodiment of ocean wave energy converter 14 10 shown in FIG. 16.
FIG. 18 is an elevation view in cross section of the elliptical embodiment of the ocean 16 wave energy converter shown in FIG. 16 and FIG. 17 showing the assembly 44 holding 17 the hydraulic cylinders.
18 FIG. 19 is a top view of maintenance cover 510 for the elliptical embodiment of the ocean 19 wave energy converter 10 shown in FIG. 16 to FIG. 18. ;
FIG. 20 is a perspective view of maintenance cover 510 shown in FIG. 19.
21 FIG. 21 is a sectional view along the major axis of the maintenance cover 510 shown in 22 FIG. 19.
23 This invention utilizes certain principles and/or concepts as are set forth in the claims 24 appended hereto. Those skilled in the arts to which this invention pertains will realize that these principles and/or concepts are capable of being utilized in a variety of embodiments 1 which may differ from the exact embodiments utilized for illustrative purposes herein. For 2 this reason this invention is not to be construed as being limited solely to the illustrative 3 embodiments, but only to be construed in view of the claims.

Brief description of the operation of the current invention is explained with reference to 6 the figures.
7 FIG. 1 shows in perspective a plurality of ocean wave energy converters 10 configured 8 into an arrangement of power generating plants positioned below sea level at a point of 9 significant wave height 26 near shore 32. This cluster of ocean wave energy converters 10 is functionally similar to a cluster of hydro-electric plants in a river basin. Some of the 11 converters 10 include power generation, some with accumulators and no generation, and 12 others with no generation and no accumulators as shown in FIG. 8 and FIG.
9. The latter 13 being analogous to moving from one hydro-electric watershed to the main reservoir.
14 The energy converters 10 in the row closest to shore 32 are interconnected with power and system control cables 14 and hydraulic fluid lines 16 laid on the ocean floor 36, joined 16 through connection boxes 18 to each other and to the distribution system 100 of a utility 17 on shore 32, or to a customer 100 receiving the power being produced. The cables to the 18 connection boxes 18 have sufficient slack to be lifted out of the water and serviced on the 19 deck of a boat. The interconnecting cables between converters 10 in the row furthest from shore are not shown. The connection boxes 18 facilitate removal of energy 21 converters 10 from service.
22 FIG. 2 is an elevation view in cross-section of an idealized ocean wave 20 with a crest 22 23 and a trough 24, of wave height 26 and wave length 28, moving in the direction 30 of 24 shore 32. One converter 10 is shown under the wave crest 22 with the converter piston 12 moving down the converter cylinder 34 in power-stroke 38, under compression from 26 the wave crest above 22, and the converter piston 12 in the other converter 10 moving up 27 the converter cylinder 34 in the return-stroke 40 discharging sea water into the wave 28 trough 24. The gas filled chamber below the piston is shown vented to the ocean surface.

1 To reduce the amount of air drawn from the surface, such air being salty and corrosive, 2 chambers of adjacent converters can be interconnected with a vent pipe so air can pass 3 from one to the other as the pistons operate 180 degrees out of phase with each other.
4 An imaginary ocean wave degree indicatar 29 graduated in increments of 2 ocean wave degrees is shown positioned so as to read ocean wave degrees of the crest 22 of the 6 ocean wave 20 ahead and above dead-centre of ocean wave energy converter 10.
The 7 imaginary ocean wave degree indicator 29 is a computer algorithm resident in the 8 software of the vector drive described in I=IG. 12 to 15. An ocean wave degree is equal 9 to ocean wave length 28 divided by 360, resulting in units of seconds per degree, and/or in feet distant of the crest axis from the converter axis.
11 FIG. 3 is a pie sectional view of a typical ocean wave converter 10 showing the internal 12 arrangements with the converter piston 12 about 40% of the way into the power stroke 38, 13 or alternately, 60% through the return stroke 40. This embodiment is for purposes of 14 illustration only; The hydraulic cylinders 42 can be of the telescoping type and when fully extended can be about three times their retracted length. A piston skirt 56 is shown with 16 annular seal 60 between the converter piston 12 and the converter cylinder 34. The 17 piston skirt 56 is optional, allowing the piston 12 to operate through a longer stroke within 18 the same height of inner chamber 34. Some artisans may prefer to eliminate the skirt 56, 19 increase the height withiii'the chamber 34, and make the side of the piston 12 longer to achieve similar stroke length.
21 FIG. 4 is an elevation vievcr in cross-section of a typical ocean wave energy converter 10 22 showing the main elements of the converter piston 12 and hydraulic cylinders 42 mounted 23 in mechanical assembly means 44 to maintain the converter piston 12 and cylinders 42 24 in alignment as the converter piston 12 moves through a power-stroke 38 return-stroke 40 cycle. A telescoping alignment device 46 is shown in retracted position 48 and in 26 expanded position 50. A hydraulic cylinder 54 adjusts the alignment of the converter 27 assembly 12, 42, 44. Some artisans prefer to eliminate the telescoping alignment device 28 by mounting castors radial'ly around the bottom end of the piston side which roll vertically 29 along the inner surface of the cylinder chamber 34 thereby maintaining the piston in alignment during power 'and return strokes. The converter piston is shown in two zs 1 positions, near the ends of the piston stroke 54. A hydraulic operator 58 keeps the skirt 2 up so it does not touch the floor at the bottom of the converter cylinder 34. One end of 3 the annular seal 60 is fastened to the cylinder 62 at about mid stroke position, and the 4 other end is fastened to the converter piston 12 near the circumference 64 on the top of the piston 12. The pressure on the annular seal 60 is less than 10 psi at about 20 feet 6 of head of seawater. Assuming a clearance of the piston 12 to the cylinder inner wall 34 7 of about 6 inches maximum, the tension in the annular seal 60 computes to a linear 8 tension of less than 30 pounds per circumferential inch width, well below the rated 9 strength of commonly available industrial fabric. A hatch 66 in the top of the converter piston 12 allow for operation inspection and maintenance. The hatch is positioned 11 generally for use with a maintenance cover fixed to the top of energy converter 10 as 12 shown in FIG. 19.
13 FIG. 5 is a perspective view of energy converter 10 with the supercharger 68 fully raised 14 to deflect kinetic energy down onto the converter piston 12. The supercharger 68 is rotatable mounted 72 about the converter cylinder 34. A hinge pin 70 constrains the 16 movement of the supercharger 68 as it is opened by the hydraulic operator 74. The 17 supercharger window 76 opens to capture kinetic energy and diverts the force down on 18 the converter piston 12.
19 FIG. 6 is a side view of FIG. 5, and additionally with the energy converter 10 mounted on a tripod base 82, shown in axial view in FIG. 7. The legs of the tripod base are cast to 21 support the energy converter 10 titled at some angle 78 into the oncoming wave to 22 enhance the effectiveness of the supercharger 68, and/or alternatively, to hold the energy 23 converter 10 in a preferred position if the sea floor is excessively inclined. Lugs 86 on the 24 side of the converter 10 are to fasten the converter to the base 82. Lugs on the base 84 maintain the converter 10 in position on the tripod base 82.
26 FIG. 7 is an axial view of the tripod base 82 for the energy converter 10, shown in side 27 view in FIG. 6. Lugs 86 on the converter 10 are clamped to the tripod base 82. Injecting 28 seawater between the base of converter 10 and tripod base 82 causes the converter to 29 float to facilitate turning the converter 10 to face the ocean wave. The angle of rotation 1 88 is shown to be about plus or minus 45 degrees of the setting for tripod base 82. Holes 2 90 in the feet of the tripod base 82 anchor the base to the ocean floor 80 as shown in 3 FIG. 6.
4 FIG. 8 is a schematic representation of the invention broken down into three different embodiments showing how different combinations of the three different embodiments can 6 be connected together to form an hydro-electric utility powered by ocean waves. FIG. 1 7 shows energy converters 10 in a utility-like arrangement. FIG. 8 should also be viewed 8 in combination with FIG. 9, which is a schematic diagram of the hydraulic components in 9 the energy converters 10 broken down into three embodiments corresponding to FIG. 8.
FIG. 1 shows a typical physical arrangement of energy converters 10 in perspective view 11 and FIG. 2 in sectional view. Energy converters 10 placed in a row 21 nearest shore 32 12 consist of energy converters 10 with all features, ' including electric generators, 13 represented in FIG. 8 by energy converter 110 and in FIG. 9 by energy converter 112.
14 The row 23 farthest from shore 32 in FIG. 1 consists of energy converters 10 with no generation of their own. These energy converters 10 supply hydraulic fluid energy to 16 energy converters 10 in row 21 nearest shore 32 and are represented in FIG.
8 by energy 17 converter 106 and in FIG. 9 by converter 108. Alternatively, energy converters 10 in the 18 second row 23 could also have no storage of their own as represented in FIG. 8 by 19 converter 102 and in FIG. 9 by converter 104. It is advantageous to add generating capacity in the second row 23, which is shown in FIG. 2 to be in the direction 30 of the 21 oncoming wave 20. It is possible thereby to reduce the amount of accumulator capacity 22 that would otherwise be required, particularly if the rows of energy converters 10 are 23 approximately half a wave length 28 apart. Accumulator capacity functions to smooth 24 power output analogous to flywheel mass provides inertia in an internal combustion engine. It is commonly known that a 2-cylinder engine for example, requires a smaller 26 flywheel mass than a single cylinder engine. A V-8 engine needs even less flywheel mass 27 and runs smoothest of all because a V-8 engine has 4 power strokes about 90 degrees 28 apart for 360 degrees of crankshaft rotation. Similarly it is possible to reduce the capacity 29 of the accumulator by spacing the rows of converters over half the wave length 25.

1 More particularly consider the three embodiments of energy converters 10 represented 2 in FIG. 8 and FIG. 9. Energy converter '102 shown in FIG. 8 and energy converter 104 3 shown in FIG. 9, represent a bare-bones energy converter 10 with a converter piston 12 4 and requisite hydraulic fluid cylinders. The hydraulic cylinder 138 in FIG.
9 represents 5 the plurality of hydraulic cylinders 42 shown in FIG. 3 and FIG. 4. Energy converter 108 6 shown in FIG. 9 comprises energy converter 104, plus a fluid power transformer 140, a 7 high pressure accumulator 164, a medium pressure accumulator 162, a hydraulic fluid 8 supply reservoir 160, and a black-start electric motor-pump set 168. Energy converter 9 112 comprises all of energy converter 108 together with a turbine-generator bay 170. The 10 turbine-generator bay is comprised of turbines 172, generators 174, and a electrical 11 control panel 126. From the control panel 126 a cable 176 connects to each generator 12 172 and a cable 178 to the black-start hydraulic motor-pump set 168, and via under water 13 cables 124 to a pad mounted transformer 128 of a traditional electric utility and via a 14 distribution line 130 to, electric power user onshore 134.
15 Sufficient power is imported via cable 124 to operate the black-start electric motor-pump 16 set 168 to charge the medium pressure accumulator 162 to build up an energy reserve 17 sufficient to run the energy converter 10 through a few return-stroke power-stroke cycles 18 while the control systems automatically adjusts to ocean wave conditions and brings the 19 energy converter 10 to a state of reliable energy production. In other words, the energy 20 converter 10 starts itself up. It is then necessary to run for a time to build up fluid energy 21 in the high pressure accumulator 164. After fluid energy in the high pressure accumulator 22 164 is considered sufficient to sustain continuous electric power production, and with line 23 158 connected to the turbine supply manifold in the turbine generator bay 170, hydraulic 24 turbines 172 are started and electric generators 174 are brought up to speed and 25 synchronized at electrical control panel 126. Then power is exported to shore 134 on line 26 124 by further opening the turbine flow valve to increase generation.

27 FIG. 10 is a schematic diagram of fluid power transformer 140 with relation to its operation 28 in FIG. 9. Several different configurations are shown for arranging the components of the 29 fluid transformer 140, including configurations for different operating conditions. The preferred embodiment 212 is switchable for all operating conditions and has fewer cross-1 overs than embodiment 204.
2 The fluid power transformer is the core element in the overall control system for the power 3 converter 10, which is explained in FIG. 12-15. The fluid power transformer 140 is 4 comprised of a hydraulic motor 182 rotatably coupled to drive a hydraulic pump 184. The hydraulic motor 182 is of higher power rating than the pump 184 to include for power 6 losses in the pump. In the preferred embodiment of the fluid power transformer 140, the 7 motor 182 and the pump 184 are infinitely variable displacement type and the motor 182 8 is infinitely variable speed controllable type. These features are commonly available.
9 Schematic diagrams of the fluid power transformer are shown without flow control valves in configurations 190-200. Switching states 202-212 show the position of control valves 11 for power-stroke and return-stroke of the power production cycle. The switching states 12 of the preferred embodiment of the fluid power transformer are shown in figures 206-212.
13 The fluid power transformer 140, shown in FIG. 10, is shown under normal operating 14 conditions in power stroke in configurations 190,194, and in return stroke in configurations 192, 196.
16 Briefly, arrows show the direction of fluid flow in configurations for power stroke and return 17 stroke. The fluid line from the energy converter 10 is connected at terminal 148. The line 18 from the high pressure accumulator 164 is connected at terminal 152. The fluid line from 19 low pressure accumulator 162 is connected at terminal 150. Alternatively, a line from the main hydraulic fluid supply reservoir 160 can be connected at terminal 150 by switching 21 valve 166 shown in FIG. 9.
., 22 During normal running conditions pressure in high pressure accumulator 164, connected 23 to line terminal 152, is higher than pressure in fluid line terminal 148 from energy 24 converter 10. During power stroke, shown in configurations 190, 194, flow from outlet terminal 150 of the fluid power transformer is connected to the medium pressure 26 accumulator 162. During return stroke, shown in configurations 192, 196, the inlet 27 terminal 150 of pump 184 is connected either to the medium pressure accumulator 162 28 or alternatively the supply reservoir 160 by switching valve 166 shown in FIG. 9.

1 During startup and warm-up conditions, the high pressure accumulator 164 connected to 2 line terminal 152, is at a lower pressure than fluid pressure from the converter 10 3 connected to terminal 148. It is necessary therefore to set valves of fluid power 4 transformer 140 according to configuration 198 for power stroke and according to configuration 200 for return stroke.
6 Adding fluid control valves to return stroke configuration 192 results in switching state 204 7 and switching those valves to positions as shown in switching state 202 gives fluid flows 8 corresponding to configuration 190.
9 Adding valves to configuration 194 results in switching state 206 which has fewer cross-overs than switching state 202. Rotating valves to positions shown in switching state 208 11 gives proper fluid flow for return stroke. Similarly 198 relates to switching state 210 for 12 power stroke and rotating valves to positions shown in switching state 212 gives fluid flow 13 for return stroke.
., 14 Switching states 206 and 208 facilitate fluid flow for power stroke and return stroke respectively for normal running conditions where high pressure accumulator 164 operates 16 at higher pressure than the incoming fluid at terminal 148 from the power stroke. Similarly 17 switching states 210 and 212 are for running under start-up and warm-up conditions, 18 where the high pressure accumulator 164 is lower pressure than the incoming fluid at 19 terminal 148. Commonly available switching valves operate faster than the allowable switching time of about 4 to 5 seconds. The preferred embodiment, shown in switching 21 states 206, 208, 210, and 212, is suitable for all operating conditions.
22 It possible to improve efficiency by reducing the circulating flow in switching state 212 23 during startup conditions. An alternative switching state 212a is shown where fluid from 24 high pressure accumulator 164 connected to terminal 152, is boosted by pump 184 to terminal 148, to eliminate the losses as fluid flowing out of terminal 148 goes first through 26 the motor and then through the pump as shown in switching state 212.
Avoiding these 27 circulating flow losses can cut the return stroke losses by about 10-20 percent. How 28 power transformer 140 avoids said circulating losses is discussed further with reference 29 to FIG. 11.

za 1 FIG. 11 is a graphic representation of power flow through the fluid power transformer 140 2 as it operates according to the schematic diagram shown on FIG. 9. The power 3 transformer 140 is FIG. 11 is shown as it would appear on a computer display screen 220, 4 222 at an instant of time when the energy converter 10 is in power stroke 220 and in return stroke 222. Pressure is measured along the y-axis 223 which is the reference axis 6 for flow. Flow is in the positive direction 224 during power stroke and in the negative 7 direction 225 during return stroke. Flow is measured along the x-axis 226 which is the 8 reference axis for pressure, with pressure rise in the positive direction 227 and pressure 9 drop in the negative direction 228 relative to the pressure at the input terminal 148 at the axis intersection. The vectors are drawn to scale within circle 229 which is surrounded 11 by square 221 graduated in units of pressure and flow.
12 During power stroke 220 fluid from the converter 10 flows into terminal 148 of the power 13 transformer 140, and is applied to the hydraulic motor 182, which drives pump 184 to 14 boost pressure to terminal 152 as shaven by vector 238. From terminal 152 fluid flows 234 to accumulator 164. Fluid discharges from motor 182 terminal 150 and flows 232 to low 16 pressure accumulator '162, or to the main reservoir 160 by setting valves 166 in the 17 appropriate positions. The pressure drop through the motor 182 is represented by vector 18 236, is also shown within circle 229. The pressure rise through pump 184 is shown by 19 vector 238, is also shown within circle 229.
Power input 240 from converter 10 is comprised of the area 240 enclosed by flow 230 of 21 length 231 and pressure change 236 of length 237. A flow-pressure vector 241 is 22 symbolic of power input to transformer 140, and is the resultant vector of flow and 23 pressure. Similarly, power 242 drawn by motor 182 is comprised of the product of flow 24 232 out terminal 150 and pressure drop 236 across terminals 148 and 150.
Flow-pressure vector 243 is symbolic of power 242 drawn by motor 182. Flow-pressure vector 245 is 26 symbolic of power 244 boosted by pump 184, powered by motor 182, to pressure 27 accumulator 164. It is assumed there are no losses in motor 182 or in pump 184, 28 therefore area 244 equals 242. The total power input 240 equals power output 246, as 29 computed by the product of flow 235 times (pressure rise 237 plus pressure rise 239), all pressures relative to pressure at terminal 150.

1 The flow-pressure vector 241 is shown in the third quadrant of the graphic circle 229 in 2 power-stroke 146 and transformer 140 is boosting pressure to accumulator 162, as shown 3 by pressure vector 238.
4 A vector dipped below the x-axis signifies a pressure reduction. It is possible to have flow with no pressure change, and pressure change with no flow, which would be the case 6 when the pump control valve is first opened and pressure builds behind a valve that is 7 closed in the output line. Consider the initial state of the system where pressure at 8 terminal 152 equals pressure at terminal 148. On a signal to begin the power stroke, the 9 pump valve opens and to maintain constant speed as pump load increases. the motor valve opens. As pressure at terminal 152 gradually increases, the flow-pressure vector 11 245 rotates in a positive direction (CCW).
12 The particulars of the return stroke display 222 can be extrapolated from the explanation 13 for the power stroke operation 220. The flow-pressure vector rotates through 90 degrees 14 CCW in the first quadrant as energy converter 10 goes through a power-stroke.
During return stroke 222 fluid from power transformer 140 flows to hydraulic cylinders 138 16 shown in FIG. 9. At the start of a return-stroke cycle, the flow-pressure vector reverses 17 itself and rotates up to 90 degrees CW in the first quadrant. This power-stroke-return-18 stroke cycle repeats itself as ocean waves crest and trough repeatedly as shown in FIG.
19 2.
The graphic representation shown on FIG. 11 is also a diagnostic device for fine tuning 21 the energy converter 10 to minimize power losses. The preferred embodiment of the fluid 22 power transformer 140 has reduced losses compared to an alternative configuration for 23 the motor and pump as shown in 216 for power stroke graphic 220 and 218 for return 24 stroke graphic 222. Rectangular area 269 is representative of circulating power losses in the power stroke and rectangular area 266 of losses in the return stroke.
During the 26 power stroke the circulating power is equal to rectangular area 269 bounded by pressure 27 difference 237 on the vertical axis and flow magnitude (268 minus 233) along the 28 horizontal axis. During return stroke circulating power is equal to rectangular area 266 29 comprised of pressure difference 259 and flow magnitude 255. The power savings that 1 can be attributed to the~fluid power transformer 140 invention equals the motor losses and 2 pumping losses which would other~rvise occur. These losses are about 15-20%
of the 3 power to drive the fluid through each unit.
4 FIG. 12 shows the control diagram for the vector drive with energy converter 10 in power 5 stroke 146 as shown in FIG. 9. During normal operating conditions fluid pressure in 6 accumulator 164 is higher than that in the line coming from the cylinders 134 . The fluid 7 power transformer 140 is connected according to switch state 206 shown in FIG. 10.
8 Fluid flow through power transformer 140 is shown by arrows on FIG. 11, in configuration 9 220 for the power stroke and configuration 222 for return stroke. Fluid power transformer 10 configuration 194 shown in FIG. 10 is repeated here for clarity. A simple representation 11 of an electric power auto-transformer 304 analogous to fluid power transformer 140 is also 12 included.
13 The motor 182 in the vector drive is first brought up to speed in readiness for the power 14 stroke, a procedure which is analogous to an electric utility commissioning a new auto-15 transformer in a transmission system by first energizing it then gradually bringing it up to 16 load, and drivers starting up their engines before putting the transmission in gear. About 17 45 ocean wave degrees, which would amount to about 5 to 10 seconds, in advance of 18 wave crest 22 arriving over top centre of converter 10 as shown by imaginary wave 19 indicator device 29 in FIG. 2, fluid power transformer 140 is energized by a low voltage 20 speed signal 290 of a quantity appropriate for setting say 70 percent of full speed for 21 motor 182. The speed signal 290 is input to a voltage summing junction 292, the output 22 294 of which is connected to the input of a voltage amplifier 296 of some gain, say 20.
23 The output of speed control amplifier 296 is adjusted to limit voltage to not more than the 24 quantity appropriate for achieving maximum speed of motor 182 when output signal 298 25 is applied to the input of the controller which forms part of a variable displacement piston 26 motor 182. The controller within motor 182 is of a type that maintains constant speed 27 from zero to full load under rated fluid pressure conditions by adjusting piston 28 displacement to match motor load . A shaft 183 couples motor 182 to a variable 29 displacement piston pump 184. Motor 182 is under no load because the flow control 30 valve within pump 184 is in zero position and motor 182 will quickly settle on speed 1 setting 290. Pump 184 is of a type that at rated speed will deliver fluid from zero to full 2 rating according to a voltage flow signal 278 input to the controller on pump 184. Motor 3 182 has a speed transducer whose voltage signal is fed back to summing junction 292 4 where it is subtracted from speed setting voltage 290. When error signal 294 is quite small, that when multiplied by the gain of speed control amplifier 296 output voltage 298 6 is very close to the desired voltage for the particular speed setting and not at voltage limit, 7 then motor 182 is close enough to speed to start pump 184.
8 After motor 182 is up to speed setting 290, a flow control signal 270 is applied to start the 9 power stroke. The desired flow setting is determined in advance by dividing the displacement volume of hydraulic cylinder equivalent 138 by approximately one quarter 11 the wave length 28 measured in seconds, or less. The flow signal 270 is input to a 12 voltage summing junction 272, the output 274 of which is connected to the input of a 13 voltage amplifier 276 of some gain, say '100. The output of flow control amplifier 276 is 14 adjusted to limit voltage to not more than the quantity appropriate for achieving maximum piston displacement of pump 184 when output signal 278 is applied to the input of the 16 controller which forms part of pump 184. The controller within pump 184 is of a type that 17 maintains constant flow from zero to full load under rated fluid pressure speed conditions.
18 The voltage output from flow transducer 282 on the outlet of pump 184 is 19 connected to one input of summing junction 284. The voltage output from flow transducer 286 on the outlet of motor 182 is connected to a second input of summing junction 284.
21 The total voltage 280 from summing junction 284 is representative of total fluid flow, and 22 is fed back to summing junction 272 where it is subtracted from the reference voltage 270 23 to produce an error signal;274. The voltage gain of flow control amplifier 276 causes the 24 actual flow through the fluid power transformer to closely track the flow setting 270 to within approximately 1/Gain times 20 in percent, in this example, about 5 percent.
26 It is shown in FIG. 12 how the vector drive controls the power stroke to convert ocean 27 wave energy to hydraulic fluid energy under normal operating conditions and store the 28 energy in a high pressure accumulator. hart generating electric power 29 FIG. 13 shows the control diagram for the vector drive with energy converter 10 in return 1 stroke with the system configured as shown in FIG. 9 except with flow through fluid power 2 transformer 140 in reverse of that shown. The fluid power transformer 140 is connected 3 according to switch state 208 shown in FIG. 10 with fluid being drawn from accumulator 4 164 to drive motor 182 and fluid being boosted to terminal 148 from medium pressure accumulator 160 during normal operating conditions. Fluid power transformer 6 configuration 196 shown in FIG. 10 is repeated here together with a simple representation 7 of an electric power auto-transformer 344, which is analogous to fluid power transformer 8 140 in switch state 208.
9 Under normal operating conditions pressure in accumulator 162 is requires very little boosting to reset the converter piston 12 to the top of converter cylinder.
Energy for motor 11 184 is drawn from high pressure accumulator 164 to drive pump 184. The vector drive 12 operates to control flow of hydraulic fluid in the return stroke similar to how it operates in 13 the power stroke as shown in FIG. 13. The rate of fluid flow setting 310 could be the 14 same or faster or slower fhan for the flow rate 270 setting in the power stroke as shown in FIG. 12. The fluid flow valves 288, 302, 303, 305 are simply switched to reverse the 16 flow to reset the cylinders 138 shown in FIG. 9.
17 FIG. 14 shows the control diagram for the vector drive with energy converter 10 in power 18 stroke 146 as shown in FIG. 9. On startup and for a warm-up period there is insufficient 19 energy in the high pressure accumulator 164 such that pressure at terminal 152 is lower than pressure at terminal 148 and it needs to be built up to where terminal 152 is higher 21 as it is under normal operating conditions. Fluid flow valves 288, 302, 303, 305 are 22 switched to state 210 shown in FIG. 10 rather than switching state 194 to reconfigure fluid 23 power transformer 140 to state 384 or 386 rather than state 304.
24 Pump 184 is no longer, drawing fluid from the power stoke and flow transducer 362 is switched out of the feedback loop 360 by opening switch 368.
26 FIG. 15 shows the control diagram for the vector drive with energy converter 10 in return 27 stroke otherwise as shown in FIG. 9. The fluid power transformer 140 is connected 28 according to switch state 210 shown in FIG. 10 with converter output pressure being 29 higher than accumulator 164 during startup or warm up operating conditions.
Fluid power 1 transformer configuration 200 shown in FIG. 10 is repeated here for clarity.
A simple 2 representation of an electric power auto-transformer 424, which is analogous to fluid 3 power transformer 140 in switch state 212, and also a second representation 426 of an 4 alternate switch state that comprises switch state 212a is also included, and it is achieved simply by switching valve 305 to a position 180 degrees from that shown on FIG. 15.
6 Motor 182 is no longer discharging fluid into return stoke circuit 148 and flow transducer 7 362 is switched out of the feedback loop 360 by opening switch 408. Switch 368 is left 8 in its normally closed position.
9 It is apparent from FIG. 15 with relation to the return stroke that the vector drive can operate effectively to convert ocean wave energy to hydraulic fluid energy under startup 11 and warm-up operating conditions and draw the energy from high pressure accumulator 12 164.
13 It is apparent from FIG. 12 to FIG. 15 that the preferred embodiment of the vector drive 14 as shown in FIG. 15 can control the ocean wave energy converter 10 through the power-stroke-return-stroke cycle from start- up, through warm-up and during normal operating 16 conditions, by simply switching flow control valves 288, 302, 303, 305 and control relays 17 368 and 408.
18 FIG. 16 is a top view of an elliptical embodiment of the piston chamber 11 of ocean wave 19 energy converter 10 which is similar to the cylindrical embodiment of the convertor 10 shown in FIG. 1 to FIG. 4. ,;The piston 12 roof has two hatch covers 66 to allow access to 21 the equipment room below piston 12. A section indicator arrow is shown through the main 22 axis and the sectional view is shown on FIG. 18. The annular seal 60 is fixed to the piston 23 at 64 and to piston chamber wall 34. Figures 16, 17 and 18 should be viewed in 24 combination with Figures 3 and 4.
FIG. 17 is a perspective view of an elliptical embodiment of the converter 10 shown in 26 FIG. 16 and is similar to the cylindrical embodiment of energy convertor 10 shown in FIG.
27 3 except without the quarter section cutaway.
28 FIG. 18 is a sectional view along the major axis of the elliptical embodiment of piston 1 chamber 34 of energy converter 10 shown in FIG. 16, and is similar to FIG.
4, except this 2 is a much larger energy converter and many more hydraulic cylinders 42 are required to 3 support piston 12. FIG. 18 shows two telescoping alignment columns 46 along the major 4 axis of elliptical converter 10, similar to the single telescoping alignment column 46 shown in FIG. 4. In one sectional view telescoping alignment columns 46 are shown in retracted 6 position 48 and in the other sectional view, in expanded position 50.
Hydraulic cylinder 7 54 adjusts horizontal alignment of piston 12 along the major axis by tilting the lower level 8 of hydraulic cylinders 42 and moves overall assembly 44 and everything above. Similarly 9 another set of hydraulic cylinders at 90 degrees to set 54, tilts hydraulic cylinders 42 along the minor axis of the ellipse and moves assembly 44 and piston 12. Some artisans 11 may prefer to eliminate the telescoping alignment columns by mounting castors radially 12 along the circumference of the piston skirt as given in the explanation of the operation in 13 Figure 4.
14 FIG. 19 is a top view of a maintenance cover 510 that attaches to the top of elliptical energy converter 11 shown in FIG 16 to FIG. 18.
16 FIG. 20 is a perspective view of maintenance cover 510 shown in top view in FIG. 19. Its 17 line-of-sight is similar to the line-of-sight of the perspective view of converter 11 in FIG 17.
18 FIG. 21 is a sectional view along the major axis of maintenance cover 510 shown in FIG.

Features inherent in energy converter maintenance cover 510 are apparent on viewing 21 FIG. 19 to FIG. 21 together. It is apparent maintenance cover 510 can float like a boat 22 and be launched from a boat ramp. Maintenance cover 512 is towed over top of energy 23 converter 11 and gradually sunk by opening valve 530 at the bottom 514 of counters 520.
24 Air trapped in space 528 on underside 526 of contour 520 keeps maintenance cover 510 afloat after contour 520 has filled with water. Lugs 524 on maintenance cover 26 restrain it from sliding off top of converter 11 when under force of heavy waves.
27 The docking procedure is comprised of lowering maintenance cover 510 by slowly 28 bleeding air out of chamber 528 while guiding 510 in descent so lugs 524 mate with lugs 1 523 on converter 11. After contact, remaining air is released until pressure of cover 510 2 on converter 11 secures the integrity of o-ring seal 522, preventing leakage into chamber 3 528 and into piston chamber 34. Lugs 524 mated to lugs 523 shown in FIG. 17 are 4 clasped together with a rectangular fixture 532 as shown in FIG. 21.
5 After docking is complete and fixture 532 secured, conduits 516 are extended to a safe 6 height of about 10 feet or more above ocean wave crest 22 shown in FIG. 2, by inserting 7 a removable conduit inside fixed conduit 516, said removable conduit has an o-ring seal 8 that mates with the top of conduit 516. Chamber roof 528 below floor 510 is drained of 9 water by lowering piston 12 to the bottom of the piston stroke, and then opening a valve 10 on the underside of piston 12 to allow seawater above to flow to a sump pump on the 11 equipment room floor. After pumping all seawater out of piston chamber 34 to the 12 surrounding sea, and vacuuming out trapped water remaining in the annular seal 60, 13 annular seal 60 can be inspected and replaced. Annular seal 60 is replaced by unbolting 14 circumferential metal band 64 from perimeter of piston 12 and unbolting circumferential 15 band 61 on piston chamber wall 34. A new annular seal 60 can installed and the old seal 16 taken up conduit 512. Bracing 518 supporting conduits 516, serve as a catwalk for a 17 mechanic to view operation cycle tests of piston 12 to ensure replacement annular seal 18 60 is properly installed.
19 . Hatch 66 is positioned directly below conduit 512 allowing replacement equipment to be 20 lowered through one of conduit 512 while maintenance mechanics access equipment 21 below piston 12 through other conduit 516.
22 After maintenance has been completed, piston 12 is moved to the top of stroke, valve 530 23 is opened to flood piston chamber 34 above piston 12, conduits extended from conduits 24 512 are removed, air from chamber 528 is released and lugs 523 524 are unfastened. In 25 preparation for ascent, valve 530 is closed and chamber 528 is filled with air and r.
26 maintenance cover 510 gradually rises to the surface. After surfacing, pump 530 is 27 started to drain contour 520 and after that is complete the maintenance cover can be 28 towed to a loading ramp.

Claims (9)

1 Claims What is claimed is:

1. An ocean wave energy converter means and a system for converting energy from recurring ocean waves to useful energy, said ocean wave energy converter means comprising:

a converter chamber means having an inner surface substantially tubular about said converter chamber centre axis, with the bottom end of said converter chamber closed adapted to be fixed with relation to the ocean floor, with top end open to the sea above and enclosing a converter piston coaxial within said converter chamber, with an annular seal between said converter inner surface and said converter piston secured to keep seawater out of a gas filled chamber below said converter piston, said gas filled chamber vented to near ocean surface pressure, said converter piston operable axially in said converter chamber in response to variations in water pressure as ocean waves pass over top of said converter piston;

a means for converting axial forces of ocean water on said top of said converter piston to a plurality of hydraulic cylinders below said converter piston connected so as to pump hydraulic fluid through a hydraulic fluid system as said converter piston reciprocates in a power stroke and return stroke cycle in near synchronism with wave crest and wave trough passing over;

said hydraulic fluid system comprising means for hydraulic fluid transmission, fluid switching and fluid metering;

a means for converting energy in said hydraulic fluid system to useful energy including a means for transferring said useful energy to an energy receiving device onshore and or for transferring energy between ocean wave energy converters.

2. An ocean wave energy converter means and a system for converting energy from recurring ocean waves to useful energy, said ocean wave energy converter means comprising:

a converter chamber means having an inner surface substantially tubular about said converter chamber centre axis, with the bottom end of said converter chamber closed adapted to be fixed with relation to the ocean floor, with top end open to the sea above and enclosing a converter piston coaxial within said converter chamber, with an annular seal between said converter inner surface and said converter piston secured to keep seawater out of a gas filled chamber below said converter piston, said gas filled chamber vented to ocean surface pressure, said converter piston operable axially in said converter chamber in response to variations in water pressure on said converter piston as ocean waves pass over;

a means for converting axial forces of ocean water on top of said converter piston to a plurality of hydraulic cylinders below said converter piston connected so as to pump hydraulic fluid through a hydraulic fluid system as said converter piston reciprocates in a power stroke and return stroke cycle in near synchronism with wave crest and wave trough passing over;

said hydraulic fluid system comprising means for hydraulic fluid transmission, switching and metering, a hydraulic accumulator, a motor, a pump, and at least one hydraulic fluid flow and pressure power transformer means;

a means for transferring energy from said hydraulic fluid system to an energy receiving device onshore and or for transferring energy between ocean wave energy converters.

3. An ocean wave energy converter means for converting energy from recurring ocean waves to useful energy, said ocean wave energy converter means comprising:

a converter chamber means having an inner surface substantially about said converter chamber centre axis, with the bottom end of said converter chamber closed adapted to be fixed with relation to the ocean floor, with top end open to the sea above and enclosing a converter piston coaxial within said converter chamber, with an annular seal between said converter inner surface and said converter piston secured to keep seawater out of a gas filled chamber below said converter piston, said gas filled chamber vented to ocean surface pressure, said converter piston operable axially in said converter chamber in response to variations in water pressure on said converter piston as ocean waves pass over;
a means for converting axial forces of ocean water on top of said converter piston to a plurality of hydraulic cylinders below said converter piston connected so as to pump hydraulic fluid through a hydraulic fluid system as said converter piston reciprocates in a power stroke and return stroke cycle in near synchronism with wave crest and wave trough passing over;

said hydraulic fluid system comprising means for hydraulic fluid transmission, switching and metering; and a means for transferring energy from said hydraulic fluid system to an energy receiving device.

4. An ocean wave energy converter according to claim 1 wherein said inner surface of said converter chamber is elliptical about said converter axis.

5. An ocean wave energy converter according to claim 2 wherein said inner surface of said converter chamber is elliptical about said converter axis.

6. An ocean wave energy converter according to claim 3 wherein said inner surface of said converter chamber is elliptical about said converter axis.

7. An ocean wave energy converter according to claim 1 wherein said inner surface of said converter chamber is circular about said converter axis.

8. An ocean wave energy converter according to claim 2 wherein said inner surface of said converter chamber is circular about said converter axis.

9. An ocean wave energy converter according to claim 3 wherein said inner surface of said converter chamber is circular about said converter axis.