HK1174963B

HK1174963B - Hydraulic apparatus

Info

Publication number: HK1174963B
Application number: HK13102341.7A
Authority: HK
Inventors: 格雷格．约翰．艾伦; 鲁德．卡尔乔; 乔纳森．皮埃尔．菲耶韦; 戴维．克塞尔; 奈杰尔．拉克斯通; 劳伦斯．德鲁．曼
Original assignee: 刻托知识产权有限公司
Priority date: 2009-11-13
Filing date: 2010-11-15
Publication date: 2017-03-17

Description

Hydraulic device

Technical Field

The present invention relates to hydraulic devices for extracting energy from wave motion.

Background

Hydraulic devices for extracting energy from wave motion are known. For example, CETO^TMSuch devices are disclosed in published international patent applications PCT/AU2006/001187 and PCT/AU2007/001685, which are hereby incorporated by reference.

Existing hydraulic devices for extracting energy from wave motion include a base that is disposed on the seabed of a body of water. An axial flow hydraulic pump is mounted on the base such that the pump can pivot relative to the base. The piston rod of the pump is coupled to the buoyant actuator by a tether. Wave motion and positive buoyancy of the buoyant actuator causes the buoyant actuator to follow the motion of the water disturbance, thereby forcing the buoyant actuator to exert a force upwardly on the tether and expel fluid from the pump to the manifold through the one-way valve under pressure from the pump. As the trough passes, the buoyant actuator drops under the weight of the pump piston and the pump inlet pressure, preparing the pump for the next push-up of the buoyant actuator.

The apparatus is designed to operate in a closed loop mode in which fluid at high pressure is pumped ashore by a hydraulic pump, energy is extracted as useful work, and the depressurized fluid is returned to the hydraulic pump at sea via a pipeline to re-supply energy.

Another known prior art hydraulic pump is similar to the prior art arrangement described above except that it includes a set of hydraulic pumps and a set of buoyant actuators each tethered to a respective piston rod of each pump.

Existing devices such as these generally require special adjustments to operate at a particular location and under particular conditions associated with that location, including wave conditions and tidal variations associated with that location. This typically involves making non-standard hardware specifically designed for a particular location, and configuring the hardware to operate in a particular manner appropriate for that location.

The need to design and manufacture such non-standard hardware means that it is difficult to simplify the manufacturing process to achieve high yields at low cost.

The present invention has been made in view of this background and the problems and difficulties associated therewith.

Disclosure of Invention

It is an object of the present invention to overcome or at least ameliorate one or more of the above disadvantages of the prior art, or to provide the consumer with a useful or commercial choice.

Other objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein is disclosed by way of illustration and example a preferred embodiment of the present invention.

According to a first broad aspect of the present invention there is provided a closed loop hydraulic apparatus for converting wave energy, the apparatus comprising: a pump for pumping fluid through the device, the pump comprising a body defining a chamber and a piston dividing the chamber into a working side and a blind side; a buoyant actuator connected to the piston; an inlet connected to the working side of the chamber enabling fluid to flow from the inlet into the working side of the chamber; an outlet connected to the working side of the chamber enabling fluid to flow from the working side of the chamber to the outlet; and a hydraulic controller operable to control the pump by controlling fluid pressures at the inlet and the outlet to optimize the output of the pump in response to tidal and/or sea state changes, the fluid pressures at the inlet and the outlet being controlled in accordance with a control algorithm, wherein the control algorithm is selected from a set of algorithms, the control algorithm is generated in accordance with an optimal screening method, and the optimal screening and control algorithm is generated by:

(i) determining a power (powermatrix) matrix;

(ii) determining a most robust spectral model of sea conditions applicable to the physical location of the device;

(iii) convolving the sea state spectral density with a power matrix to form a resulting transfer function;

(iv) performing multi-parameter optimization on an energy function obtained by integrating the transfer function with time;

(v) defining an operating point and a stable operating region in a vector space of the energy function to generate a template;

(vi) applying a control system transfer function to a state variable of the device to generate a control algorithm;

(vii) performing a simulation of the control algorithm to verify the accuracy and stability of the algorithm and the set point template;

(viii) repeating steps (ii) to (vii) above according to different sea states to fill the space of the desired control law.

In a first preferred mode, the hydraulic controller includes: an inlet hydraulic accumulator; an input hydraulic control valve connected to the inlet and the inlet hydraulic accumulator; an outlet hydraulic accumulator; an output hydraulic control valve connected to the outlet and the outlet hydraulic accumulator; a sequence valve connected to the inlet and the outlet; a first outlet pressure sensor connected to the outlet; a flow meter connected to the outlet; a proportional throttle valve connected to the flow meter; and a second outlet pressure sensor connected to the proportional throttle valve.

In a second preferred mode, the hydraulic controller includes: a working side hydraulic accumulator connected to a working side of the chamber; an outlet hydraulic accumulator connected to the outlet, an inlet hydraulic accumulator connected to the inlet; an outlet valve connected to the outlet; an inlet valve connected to the inlet; a pressure relief valve connected to the outlet and the inlet valve; an intermediate hydraulic accumulator connected to the inlet valve; a control system; and a plurality of sensors, wherein the control system is operative to control the outlet valve and the inlet valve in response to the output of the sensors.

In a third preferred mode, the hydraulic controller includes: a working side hydraulic accumulator connected to a working side of the chamber; an outlet hydraulic accumulator connected to the outlet; an inlet hydraulic accumulator connected to the inlet; a pressure relief valve connected to the outlet and the inlet; an outlet valve connected to the outlet; an inlet valve connected to the inlet; and an intermediate hydraulic accumulator connected to the inlet valve.

Preferably, the hydraulic controller further comprises a further pressure reducing valve connected to the outlet and the inlet.

Preferably, the hydraulic controller further includes: a control system; and a plurality of sensors, wherein the control system is operative to control the outlet valve, the inlet valve and the pressure relief valve in response to the output of the sensors.

Preferably, the sensors include pressure, temperature and flow sensors.

Preferably, the charge in the lines of the working side hydraulic accumulator, the outlet hydraulic accumulator, the inlet hydraulic accumulator and the intermediate hydraulic accumulator can be varied according to the control algorithm.

Preferably, the outlet valve is a gun type valve for a pelton wheel.

Preferably, the apparatus further comprises: a plurality of pumps for pumping fluid through the device; a plurality of buoyant actuators connected to the pistons of the pumps; a plurality of inlets connected to a working side of a chamber of the pump; and a plurality of outlets connected to a working side of the chambers of the pump, the hydraulic controller including a plurality of working side hydraulic accumulators connected to the working side of the chambers of the pump.

Preferably, the pumps are arranged in an array of no more than three rows.

Preferably, the pumps are identical pumps.

Preferably, the control algorithm is adjusted to provide the maximum total energy.

Preferably, step (i) may also be repeated as part of step (viii) if the set or space of step control algorithms includes a change in condition of the machine/device.

Preferably, the generation of said control algorithm is heuristic.

Preferably, the optimization is achieved by:

(i) determining a power matrix;

(ii) using the power matrix and the wave model to refine and optimize the transfer function of the control system;

(iii) a robust physical spectral model for a physical location is used to optimize the transfer function for a particular physical location.

According to a second broad aspect of the present invention there is provided a method of forming an optimal screen and set of control algorithms for a closed loop hydraulic device for converting wave energy, said method comprising the steps of:

(i) determining a power matrix;

Preferably, the generation of said control algorithm is heuristic.

Preferably, the optimization is achieved by:

(i) determining a power matrix;

Preferably the closed loop hydraulic means for converting wave energy comprises a hydraulic means according to the first broad aspect of the present invention.

According to a third broad aspect of the present invention, there is provided a method of controlling the hydraulic apparatus according to the first broad aspect of the present invention.

According to a fourth broad aspect of the present invention, there is provided a method for obtaining an optimal screening method (optimalfilter) for controlling a hydraulic device according to the first broad aspect of the present invention.

According to a fifth broad aspect of the present invention, there is provided a hydraulic device comprising a pump for pumping fluid through the device and a control element for controlling the flow of the fluid.

According to a sixth broad aspect of the present invention, there is provided a method of controlling the hydraulic apparatus according to the fifth broad aspect of the present invention, the method comprising the steps of:

operating a pump of the device to pump hydraulic fluid through the device; and

controlling the control element to control the flow of the fluid.

Preferably, the pump is an axial flow hydraulic pump.

Preferably, the control element is an outlet valve, an inlet valve, an accumulator and/or a pressure relief valve.

Preferably, the device further comprises an outlet check valve.

Preferably, the device further comprises an inlet check valve.

Preferably, the device further comprises a rod/adjustment/working side accumulator.

Preferably, the apparatus further comprises a blind side accumulator.

Preferably, the apparatus further comprises an outlet accumulator.

Preferably, the apparatus further comprises an inlet accumulator.

Preferably, the device further comprises a sensor.

Preferably, the apparatus further comprises a controller.

Preferably, the device is a closed loop hydraulic device.

Preferably, the device is used to extract energy from wave motion or to convert wave energy.

According to a seventh broad aspect of the present invention, there is provided a system for controlling and optimizing a wave energy device, comprising: a wave energy converter utilising a wave energy converter having a hydraulic power output, the converter operating in a closed loop mode, the closed loop including an equipment output line at a higher pressure and a fluid input line at a substantially lower pressure, a fluid circulating within the closed loop being substantially based on seawater, the fluid transferring energy to shore, the fluid transferring energy by pressure and flow; and devices that remove energy from the onshore working fluid by means of hydro-mechanical equipment such as turbines or pressure-exchange engines.

Preferably, the system comprises control elements both onshore and offshore.

Preferably, the control element comprises: valves controlling pressure and flow in the onshore outlet and inlet lines; an offshore pressure reducing valve located between the inlet line and the outlet line; a hydraulic accumulator located at sea and a hydraulic accumulator located onshore, one connected to the outlet line and the other connected to the inlet line; and a pressure reducing valve located onshore between the inlet line and the outlet line.

Preferably, a control algorithm is used to control a plurality of hydraulic valves and the charge pressure (gaspresurecharges) within the accumulator.

According to an eighth broad aspect of the present invention, there is provided a control algorithm for use in the system according to the fourth broad aspect of the present invention. Preferably, the control algorithm is capable of performing one or more of the following functions or has one or more of the following characteristics:

a. between two limits (both limits included) of piston restricted and piston free, through CETO^TMThe mechanical stiffness is adjusted by a change in the volume of the energy accumulator (open/close valve) of the Wave Energy Converter (WEC). "piston restricted" refers to a situation in which the piston will experience a minimum amount of movement because the movement of hydraulic fluid within the hydraulic line is restricted to the extent permitted by the trim accumulator; "piston free" refers to the situation where fluid is free to flow between the inlet and outlet lines and the piston is free to move under its own weight and the external forces applied to it.

b. Adjusting CETO^TMTo accommodate slow changes in water depth that would occur in the tide.

c. The control elements of the WEC device are adjusted according to the real-time input of the nearby wave measuring device. Such a device can record the instantaneous wave height (H), wave period (T), wave amplitude (θ) and any other relevant parameters defining the sea state, and provide real time data to the algorithm.

d. The setting in c is adjusted so that the power P is an instantaneous maximum.

e. The setting in c is adjusted so that the power P is the instantaneous minimum. This condition is ideal if maintenance and inspection is to be performed.

f. Adjusting the settings in c so that the power P exceeds the minimum value P_mProbability of p_m。

g. The value of the control element is limited by applying a preset template F, which maximizes the total power delivered by the WEC during the time interval τ.

h. The time interval τ may range from seconds to fractions of hours to hoursAn internal variation. For example, the standard practice at sea is 20 minutes for continuous irregular sea conditions and 3 hours for severe sea conditions.

i. Each epoch τTemplate F to be uniqueCorrelation, the template FThe set operating point of algorithm a and the control range to be applied by algorithm a are defined.

j. The control algorithm A may comprise a series of templates F as in i)Such that the respective templates cooperate to provide an optimum energy output E for any period of time between the shortest and longest_max. That is, the algorithm A is always adjusted to provide the maximum integration energy E_maxWherein:

k. the specific algorithm A may be selected from the algorithms A_iIs selected from the set of (1), wherein the set A_iInclud ing inclement weather (elements) that are specific to one or more of the following conditions:

a.i. a specific geographical location;

specific water depths and water depth measurements;

specific classifications of wave activity, e.g., energetic, marine, mild, offshore or combinations of these;

a specific time of year, e.g., winter, summer;

specific structure of e.v. wec;

specific physical structures of wec, including CETO^TMEnergy release devices as already described in the co-pending patent application;

g.vi.wec specific physical state, corresponding to WEC running history time, state;

any other change in the structure of wec;

major annual sea state. For example, the position of the fijiri island on the west australian sea has 6 to 8 major sea states; and

j.x. specific safety/emergency conditions.

According to a ninth broad aspect of the present invention, there is provided a system comprising an array of WECs connected together in parallel to the same set of inlet and outlet conduits forming a closed loop system according to any one of the seventh to eighth aspects of the present invention.

According to a tenth broad aspect of the present invention, there is provided a system according to the ninth broad aspect of the present invention wherein the optimization of algorithm a is affected by wave amplitude. The algorithms Ai and F being substantially different from those of a single WEC. The multi-cell algorithm differs from the single-cell algorithm in that it is controlled by hydraulic interaction between the cells.

According to an eleventh broad aspect of the present invention, there are provided seventh toThe system according to any one of the ten broad aspects, wherein algorithm A_iProduced according to the optimal screening method.

According to a twelfth broad aspect of the present invention, there is provided a hydraulic apparatus comprising:

a hydraulic pump including a body defining a chamber and a piston dividing the chamber into a working side and a blind side (ablindside); and

a blind side hydraulic accumulator connected to the blind side of the chamber.

Preferably, the blind side hydraulic accumulator is connected in parallel with the blind side of the chamber. Optionally, the blind side hydraulic accumulator is connected in series with the blind side of the chamber. Preferably, the apparatus further comprises a closed blind side hydraulic line comprising the blind side hydraulic accumulator and the blind side of the chamber.

Preferably, the apparatus further comprises a fluid able to flow between the blind side hydraulic accumulator and the blind side of the chamber. Preferably, the fluid is a high lubricity fluid. Preferably, the fluid is a low viscosity fluid.

Preferably, the apparatus further comprises a blind side mechanical damper fixed to the piston. Preferably, the blind side mechanical damper is an elastic damper. Optionally, the blind side mechanical damper is a spring.

Preferably, the device further comprises a working side mechanical damper fixed to the piston. Preferably, the working side mechanical damper is an elastic damper. Optionally, the working side mechanical damper is a spring.

Preferably, the apparatus further comprises a working side hydraulic accumulator connected to the working side of the chamber. Preferably, the working side hydraulic accumulator is connected in parallel with the working side of the chamber. Optionally, the working side hydraulic accumulator is connected in series with the working side of the chamber.

Preferably, the device further comprises an outlet check valve connected to the working side of the chamber and an inlet check valve connected in parallel with the outlet check valve. In some embodiments, the inlet check valve is connected to the blind side of the chamber. Preferably, the apparatus further comprises an outlet hydraulic accumulator connected in parallel with the outlet check valve. Preferably, the apparatus further comprises an inlet hydraulic accumulator connected in parallel with the inlet check valve.

Preferably, the apparatus further comprises a hydraulic interface unit comprising an outlet check valve, an inlet check valve, an outlet hydraulic accumulator and an inlet hydraulic accumulator. Preferably, the hydraulic interface unit further comprises a blind side hydraulic accumulator. Preferably, the hydraulic interface unit further comprises a working side hydraulic accumulator. Preferably, the hydraulic interface unit further comprises a pressure relief valve.

Preferably, the apparatus further comprises a hydraulic controller connected to the outlet check valve and the inlet check valve. Preferably, the hydraulic controller comprises a pressure reducing valve. Preferably, the apparatus further comprises a high pressure line connecting the hydraulic control to the outlet check valve and a low pressure line connecting the hydraulic control to the inlet check valve. Preferably, the apparatus further comprises a hydraulic load connected to the hydraulic controller.

Preferably, the device is a closed loop hydraulic device.

Preferably, the device is used to extract energy from wave motion or to convert wave energy. In a particularly preferred form, the apparatus further comprises a buoyant actuator bolted to the piston.

According to a thirteenth broad aspect of the present invention, there is provided a hydraulic device comprising:

a hydraulic pump including a body defining a chamber and a piston dividing the chamber into a working side and a blind side; and

a working side hydraulic accumulator connected to the working side of the chamber.

Preferably, the working side hydraulic accumulator is connected in parallel with the working side of the chamber. Optionally, the working side hydraulic accumulator is connected in series with the working side of the chamber.

Preferably, the apparatus further comprises a blind side hydraulic accumulator. Preferably, the blind side hydraulic accumulator is connected in parallel with the blind side of the chamber. Optionally, the blind side hydraulic accumulator is connected in series with the blind side of the chamber. Preferably, the apparatus further comprises a closed blind side hydraulic line comprising the blind side hydraulic accumulator and the blind side of the chamber.

Preferably, the device further comprises an outlet check valve connected to the working side of the chamber and an inlet check valve connected in parallel with the outlet check valve. In some embodiments, the inlet check valve may be connected to the blind side of the chamber. Preferably, the apparatus further comprises an outlet hydraulic accumulator connected in parallel with the outlet check valve. Preferably, the apparatus further comprises an inlet hydraulic accumulator connected in parallel with the inlet check valve.

Preferably, the device is a closed loop hydraulic device.

According to a fourteenth broad aspect of the present invention, there is provided a hydraulic apparatus comprising a hydraulic pump for circulating fluid through the apparatus and a hydraulic controller for controlling the apparatus.

Preferably, the hydraulic pump includes a body defining a chamber and a piston dividing the chamber into a working side and a blind side.

Preferably, the apparatus includes a blind side hydraulic accumulator connected to the blind side of the chamber. Preferably, the blind side hydraulic accumulator is connected in parallel with the blind side of the chamber. Optionally, the blind side hydraulic accumulator is connected in series with the blind side of the chamber. Preferably, the apparatus further comprises a closed blind side hydraulic line comprising the blind side hydraulic accumulator and the blind side of the chamber.

Preferably, the apparatus further comprises a hydraulic interface unit comprising an outlet check valve, an inlet check valve, an outlet hydraulic accumulator and an inlet hydraulic accumulator. Preferably, the hydraulic interface unit further comprises a blind side hydraulic accumulator. Preferably, the hydraulic interface unit further comprises a working side hydraulic accumulator.

Preferably, the hydraulic controller is capable of controlling the device according to an algorithm.

Preferably, the hydraulic controller is connected to the outlet check valve and the inlet check valve. Preferably, the apparatus further comprises a high pressure line connecting the hydraulic control to the outlet check valve and a low pressure line connecting the hydraulic control to the inlet check valve.

Preferably, the apparatus further comprises a hydraulic load. Preferably, the load comprises a turbine. Preferably, the turbine is a pelton turbine (pelton turbine).

Preferably, the device is a closed loop hydraulic device.

Drawings

For a more complete understanding and appreciation of the invention, preferred embodiments thereof will now be described in connection with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a first preferred embodiment of a hydraulic device;

FIG. 2 is a schematic diagram of a second preferred embodiment of a hydraulic device;

FIG. 3 is a schematic diagram depicting more particular details of a portion of the hydraulic device of FIGS. 1 and 2, including a cross-sectional side view of an axial flow hydraulic pump of the device;

FIG. 4 is a schematic diagram of a third preferred embodiment of a hydraulic device including a cross-sectional side view of an axial flow hydraulic pump of the device;

FIG. 5 is a cross-sectional side view of a fourth preferred embodiment of the hydraulic device;

FIG. 6 is a schematic diagram of a fifth preferred embodiment of a hydraulic device, including a cross-sectional side view of an axial flow hydraulic pump of the device;

FIG. 7 is a schematic diagram of a sixth preferred embodiment of a hydraulic device, including a cross-sectional side view of an axial flow hydraulic pump of the device;

FIG. 8 is a schematic diagram of a seventh preferred embodiment of a hydraulic device, including a cross-sectional side view of an axial flow hydraulic pump of the device;

FIG. 9 is a schematic diagram depicting a hydraulic instrument, a control system, and a battery charging system of the hydraulic device of FIG. 8;

FIG. 10 is a graph depicting piston displacement range versus different suction and discharge pressure ranges for a hydraulic device such as the devices in FIGS. 8 and 9;

FIG. 11 is a schematic diagram of an eighth preferred embodiment of a hydraulic device including a cross-sectional side view of an axial flow hydraulic pump of the device; and

fig. 12 is a schematic view of a ninth preferred embodiment of the hydraulic device.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

Referring to fig. 1-3, a closed loop hydraulic system 30 for extracting energy from wave motion or converting ocean energy includes an axial flow hydraulic pump 31, the axial flow hydraulic pump 31 including a pump body 32 defining a chamber 33. The pump body 32 includes a side wall 34, the side wall 34 having an upper end closed by a top wall 35 and a lower end closed by a bottom wall 36. The bottom wall 36 is arranged to be connected to a base 37.

The piston 38 is received by the chamber 33 such that the piston 38 divides the chamber 33 into a rod or working side 39 and a blind side 40, and the piston 38 is able to slide back and forth within the chamber 33. A seal (not shown) between the piston 38 and the sidewall 34 prevents fluid from flowing past the piston 38 and between the working side 39 and the blind side 40. Ideally, the working side 39 and the blind side 40 of the chamber 33 do not communicate within the pump 31 due to the complete sealing of the moving piston 38 with the sidewall 34 of the pump 31. As the seal wears, some leakage between the two chambers is tolerable.

A working side mechanical damper 41 is fixed to the piston 38 with the damper 41 on the working side 39 of the chamber 33. A blind side mechanical damper 42 is secured to the piston 38 such that the damper 42 is located on the blind side 40 of the chamber 33.

A piston rod 43 extends from the piston 38 and through an opening in the top wall 35 of the pump body 32, allowing the rod 43 to move back and forth with the piston 38 relative to the pump body 32. A seal (not shown) prevents fluid from leaking out of the chamber 33 through the opening.

The buoyant actuator 44 is connected to the upper end of the piston rod 43 by a line 45.

The apparatus 30 further comprises a blind side hydraulic line 46, the blind side hydraulic line 46 comprising the blind side 40 of the chamber 33 and a blind side hydraulic accumulator 47. The conduit 46 is closed so that fluid can only be exchanged between the blind side 40 of the chamber 33 and the accumulator 47. An accumulator 47 is connected to the blind side 40 of the chamber 33 by a hose 48 to enable fluid flow between the accumulator 47 and the blind side 40 of the chamber 33. The blind side hydraulic accumulator 47 has a minimum impedance at all times except for the damping zone, which is controlled via the obstruction of the pump ports by the piston check ring.

The fluid in the blind side conduit 46 comprises a mixture of liquid and gas, according to standard practice. The accumulator 47 thus acts entirely as a reservoir and ideally does not provide any damping.

The fluid in the blind side conduit 46 may be a low viscosity fluid. As with many piston accumulators, the blind side may be completely filled with a gas such as nitrogen to reduce hydrodynamic losses when compared to a fluid. This also has the advantage of lower cost and smaller accumulators.

The fluid in the blind side passage 46 may include a high lubricity (i.e., lubricating capacity) fluid. This lubrication may improve the seal life of the piston. The fluid may also be used to lubricate the rod seal via a capillary tube (not shown). Since the required volume of lubricating fluid required is relatively low, the additional costs can be compensated by savings in maintenance and downtime.

The device 30 further comprises an outlet check valve 49, which outlet check valve 49 is connected to the working side 39 of the chamber 33 by a hose 50, enabling fluid to flow from the chamber 33 through the valve 49 in the direction of arrow "a". An inlet check valve 51 is connected in parallel with outlet check valve 49 and hose 50, allowing fluid to flow in the direction of arrow "B" through valve 51 and into chamber 33.

An outlet hydraulic accumulator 52 is connected in parallel with the outlet check valve 49. An inlet hydraulic accumulator 53 is connected in parallel with the inlet check valve 51.

Referring particularly to fig. 1, in use, a portion of the apparatus 30 is disposed in an offshore body of water 54 (e.g., the sea or ocean), the body of water 54 having a water surface 55 and an average sea level 56. The hydraulic pump 31 is secured to a base 37, the base 37 resting on the seabed 57 of the body of water 54. The pump 31 is fixed to the base 37 such that the pump 31 can pivot relative to the base 37. The check valves 49, 51 and accumulators 47, 52 and 53 are located within a hydraulic interface unit 58 also located offshore. The high-pressure outlet of the hydraulic interface unit 58 is connected by a high-pressure line to the high-pressure inlet of the shore plant 59, and the low-pressure inlet of the hydraulic interface unit 58 is connected by a low-pressure line to the low-pressure outlet of the shore plant.

The buoyant actuator 44 is located within the body of water 54 such that the wave motion of the body of water and the positive buoyancy of the actuator 44 causes it to follow the motion of the water, causing the actuator 44 to be forced upwardly, exerting a force on the line 45 which in turn forces the piston 38 to move upwardly within the chamber 33 towards the top wall 35 of the pump body 32. As the piston 38 moves upward, fluid from the working side 39 of the chamber 33 is pushed out of the chamber 33 in the direction of arrow A through the hose 50 and the outlet check valve 49.

Some of the energy of the fluid pumped through the outlet check valve 49 is stored in an outlet accumulator 52, the outlet accumulator 52 serving to smooth the flow of fluid through the high pressure portion of the closed loop hydraulic circuit of which the outlet check valve 49 and the accumulator 52 form part. The fluid flows around the remainder of the tubing before flowing back to the pump 31 through the various branches of the tubing in the direction of arrow B.

As the piston 38 moves upwardly in the chamber 33, fluid in the closed blind side hydraulic line 46 moves from the accumulator 47 through the hose 48 and into the blind side 40 of the chamber 33. The fluid within the conduit 46 is a high lubricity and low viscosity fluid.

The working side mechanical damper 41 prevents movement of the piston 38 as it approaches the top wall 35 of the pump body 32 to prevent damage to the piston 38 and the pump body 32 during the upstroke of the piston 38. Specifically, the working-side mechanical damper 41 reduces the vibration load on the pump 31 and the rope 45 in the up stroke.

As the trough of the wave passes through the device 30, the buoyant actuator 44 sinks under the weight of the piston 38 and the pressure of the fluid, which flows in the closed hydraulic line and through the inlet check valve 51 and the hose 50 in the direction of arrow B back to the working side 39 of the chamber 33. A portion of the energy of the return fluid is stored in the inlet accumulator 53, and the accumulator 53 serves to smooth the flow of fluid through the low pressure portion of the closed loop hydraulic circuit.

As the piston 38 moves downward within the chamber 33, the high lubricity and low viscosity fluid within the blind side 40 of the chamber 33 flows from the chamber 33 back to the accumulator 47 through the hose 48. Ideally, the accumulator 47 does not provide any hydraulic damping, but merely acts as a reservoir.

The blind side mechanical damper 42 resists movement of the piston 38 as the piston 38 approaches the bottom wall 36 of the pump body 32 to prevent damage to the piston 38 and the pump body 32 on the downstroke of the piston 38. Specifically, the blind side mechanical damper 42 reduces the vibration load on the pump 31 and the rope 45 in the down stroke.

This process is repeated each time a peak and trough pass the device 30.

Referring to fig. 2, the apparatus 30 may include a set of pumps 31 and a set of buoyant actuators 44 connected to a hydraulic interface unit 58.

Referring to fig. 4, a hydraulic device 60 for extracting energy from wave motion or converting wave energy is similar to device 30. Accordingly, like features of the device 60 and the device 30 are indicated with like reference numerals.

The device 60 differs from the device 30 in that the device 60 further comprises a working side hydraulic accumulator 61, the working side hydraulic accumulator 61 being connected in parallel with the working side 39 of the chamber 33 by the hose 50, enabling fluid flow between the chamber 33 and the working side hydraulic accumulator 61.

Furthermore, the arrangement 60 comprises a hydraulic interface unit 62, which hydraulic interface unit 62 comprises a blind side hydraulic accumulator 47, an outlet check valve 49, an inlet check valve 51, an outlet hydraulic accumulator 52, an inlet hydraulic accumulator 53 and a working side hydraulic accumulator 61.

The hydraulic interface unit 62 includes an outlet 63 and an inlet 64.

The operation of the device 60 is substantially the same as the operation of the device 30, except that the accumulator 61 provides hydraulic damping to the piston 38 during the upstroke of the piston 38, which increases the mechanical damping provided by the working side mechanical damper 41.

The hydraulic interface unit 62 is arranged offshore, together with the pump 31 and the buoyant actuator 44 of the device 60.

Referring to fig. 5, a hydraulic device 70 for extracting energy from wave motion or converting wave energy includes an axial flow hydraulic pump 71, the axial flow hydraulic pump 71 including a pump body 72 defining a chamber 73. The pump body 72 includes a side wall 74, the side wall 74 having an upper end closed by a top wall 75. The upper portion 76 of the side wall 74 is thicker than the lower portion 77 of the side wall 74 such that the upper portion 78 of the chamber 73 is narrower than the lower portion 79 of the chamber 73. The upper portion 76 of the sidewall 74 includes an upper port 80 and a lower port 81.

Piston 82 is received by chamber 73 such that piston 82 divides chamber 73 into a working side 83 and a blind side 84, and piston 82 is able to slide back and forth within chamber 73. The piston 82 includes an upper portion 85 and a wider lower portion 86. Unlike the lower portion 86 of the piston 82, the upper portion 85 of the piston 82 is narrow enough to be received by the upper portion 78 of the chamber 73, as shown in FIG. 5. A concave edge 87 extends around the upper periphery of the upper portion 85 of the piston 82. The concave edge 87 includes a vertical surface 88 and a downwardly sloping surface 89. The concave edge 87 prevents the piston 82 from completely covering the upper port 80.

A seal 90 between the piston 82 and the sidewall 74 prevents fluid from flowing past the piston 82 and between the working side 83 and the blind side 84.

A piston rod 91 extends from piston 82 and through an opening in top wall 75 of pump body 72, allowing rod 91 to move back and forth with piston 82 relative to pump body 72. Seal 92 prevents fluid from leaking out of chamber 73 through the opening in top wall 75.

A working side hydraulic accumulator 93 is connected to the upper port 80 by a hose 94, enabling fluid to flow back and forth between the working side 83 of the chamber 73 and the working side hydraulic accumulator 93.

A hose 95 is connected to the lower port 81. High pressure fluid can exit chamber 73 through lower port 81 and hose 95 in the direction of arrow "a" and low pressure fluid can enter chamber 73 through lower port 81 and hose 95 in the direction of arrow "B".

Referring to fig. 6, a closed loop hydraulic device 100 for extracting energy from wave motion or converting wave energy includes a hydraulic load having a pelton turbine 101. The load may also include an electrical generator (not shown) driven by the turbine 101.

The apparatus 100 further comprises a device 60, the device 60 comprising a hydraulic pump 31. The pump 31 operates to pump fluid through the apparatus 100 to drive the turbine 101.

The hydraulic controller 102 controls the fluid pumped through the device 100 by the pump 31. Specifically, the controller 102 controls the pressure and flow rate of the fluid in the high and low pressure portions of the device 100.

An inlet 103 of controller 102 is connected to outlet 63 of hydraulic interface unit 62 by a high pressure line 104. The outlet 105 of the controller 102 is connected to the inlet 106 of the turbine 101 by a high pressure line 107. An outlet 108 of turbine 101 is connected to an inlet 109 of controller 102 by a low pressure line 110. An outlet 111 of the controller 102 is connected to the inlet 64 of the hydraulic interface unit 62 by a low pressure line 112.

With a closed loop device, such as the device 100 shown in fig. 6, it is possible to have a fully closed pump control. A control algorithm is implemented to manage the operation of the onshore hydraulic control system and the offshore wave energy device 31 and the hydraulic interface unit 62, which can manage the inlet and outlet pump pressures to maximize the output (displacement) and reduce the impact at the top and bottom of the pump stroke, with the input of power and displacement of the pump. This algorithm improves the power output of the device and reduces damage/wear to the pump 31. This method will also allow compensation of tidal water movement provided that the pump stroke is long enough to cover the tidal range.

The apparatus 100 should maintain a fixed stationary position relative to the average level of the buoyant actuators in the water column in response to tidal changes. This can be achieved by a closed loop control arrangement.

The control algorithm is site specific and contains information about local wave dynamics and tidal ranges and provides optimal operation of the wave energy converter at that location. For example, the wave energy converter may be used near the coast of western australia, in some locations in europe, and in some foreign countries in france. All locations may have different tidal ranges and different wave statistics. The use of location-specific, adaptively adjusted control algorithms allows for optimal use of the same type of equipment and offshore hardware at each location.

Furthermore, it allows manual or pseudo-control of the buoyancy of the buoyant actuator. This may be achieved by controlling the pump inlet pressure to reduce the physical buoyancy of the buoyant actuator 44 in combination. This has the advantage of allowing operation (downward movement) of the buoyant actuator 44 under smaller wave conditions. The outlet pressure does not change the effective buoyancy of the buoyant actuator, but is controlled in the same manner to ensure operation (upward motion) over a range of wave conditions.

In addition, it allows a degree of hydraulic "stretch" to be added to the conveying function of the rope. The desired stiffness characteristics of the device 100 cannot generally be achieved by mere stretching of the mechanical cords, and accumulators in the hydraulic lines may be used to provide hydraulic "stretch" to achieve the desired characteristics.

The apparatus 100 may provide buffered energy recovery. The accumulator of the apparatus 100 may be used to absorb some of the damping energy during the damping phase of the piston motion and may transfer this energy back to the system for subsequent absorption by the working fluid.

Each of the foregoing features may be applied to the device 100 individually or in increments.

Also, each of the foregoing features may be applied to hydraulics for extracting energy from wave motion or to systems external to the hydraulics. For example, they may be applied to hydraulic devices or systems having:

1. a variable force input on the hydraulic pump;

2. the possibility of damage due to extreme movement of the hydraulic pump;

3. long term wear or leakage in the system must be compensated for.

Referring to fig. 7, a closed loop hydraulic device 120 for extracting energy from wave motion or converting wave energy includes an axial flow hydraulic pump 121, the axial flow hydraulic pump 121 including a pump body 122 defining a chamber 123. Pump body 122 includes a side wall 124, side wall 124 having an upper end closed by a top wall 125 and a lower end closed by a bottom wall 126. The bottom wall 126 is configured to be connected to a base (not shown).

The piston 127 is received by the chamber 123 such that the piston 127 divides the chamber 123 into a working side 128 and a blind side 129 and the piston 127 is capable of sliding back and forth within the chamber 123. A seal (not shown) between the piston 127 and the sidewall 124 prevents fluid from flowing past the piston 127 and between the working side 128 and the blind side 129.

A piston rod 130 extends from piston 127 and through an opening in top wall 125 of pump body 122, allowing rod 130 to move back and forth with piston 127 relative to pump body 122. A seal (not shown) prevents fluid from leaking out of the chamber 123 through the opening.

An outlet check valve 131 is connected to the working side 128 of the chamber 123 by a quick connector 132. An inlet check valve 133 is connected in parallel with the working side 128 by a quick connector 132. The inlet check valve 133 is also connected in parallel with the blind side 129 of the chamber 123 by a quick connector 134. The sequence valve 135 is connected in parallel with the outlet check valve 131 and the inlet check valve 133.

The hydraulic control valve 140 is connected in series with an outlet hydraulic accumulator 141. The hydraulic control valve 140 is connected in parallel with the outlet check valve 131 and the sequence valve 135.

The hydraulic control valve 142 is connected in series with the inlet hydraulic accumulator 143. The hydraulic control valve 142 is connected in parallel with the sequence valve 135.

The pressure sensor 144 detects the pressure of the high pressure portion of the device 120 and the flow meter 145 measures the flow rate of the fluid of the high pressure portion of the device 120.

A proportional throttle valve (proportional) 146 is connected in series with the flow meter 145, and a pressure sensor 147 detects the pressure of the fluid output from the proportional throttle valve 146.

The fluid output from the proportional throttle valve 146 drives a turbine 148, which turbine 148 in turn drives a water pump 149 for the chiller.

The low pressure fluid output from the turbine 148 drives the water pump 150 and flows through the check valve 151, the water pump 150 cooling the fluid returning to the pump 121, the check valve 151 connected in parallel with the sequence valve 135.

The valves 140 and 142, the pressure sensors 144 and 147, the flow meter 145, the proportional throttle valve 146 and the sequence valve 135 form part of a controller or control system for controlling the operation of the device 120.

The device 120 may provide energy spillover. I.e. it may provide for excess energy consumption. For example, if the turbine 148 drives a generator connected to the grid and there is a grid fault, the device 120 may consume energy instead of using the energy to rotate the turbine 148. Energy may be consumed by operating the device 120 to run low pressure within the pump chamber 123 or by using a body of water in which the pump 31 is located, by mechanically heating the water to act as a heat sink. Sequence valve 135 may be operated to bypass turbine 148.

The operation of the closed-loop devices 30, 60, 70, 100, 120 allows for many of the innovations described herein.

Importantly, the operation of the apparatus in the closed loop mode allows the use of common or standard hardware in many different parts of the world, the response of each apparatus being actively adjustable in real time, or pre-adjusted to accommodate different wave conditions, allowing tidal changes, more generally, to accommodate a wide range of anticipated operating scenarios occurring in different parts.

The advantage of having a common or standard system or set of pumps, buoyant actuators, ropes and hydraulic equipment is the ability to simplify the manufacture of such equipment and to achieve high production and therefore lower cost. When used in place, each set of equipment can be optimized by a control algorithm running on a closed loop hydraulic system. Each location may have a custom algorithm that controls the movement of the hydraulic fluid in response to wave and tidal power changes at that location, optimizes energy output, and minimizes wear or damage to the offshore equipment.

Referring to fig. 8, a closed loop hydraulic device 160 for extracting energy from wave motion or converting wave energy includes an axial flow hydraulic pump 161, the axial flow hydraulic pump 161 including a pump body 162 defining a chamber 163. Pump body 162 includes a side wall 164, side wall 164 having an upper end closed by a top wall 165 and a lower end closed by a bottom wall 166. The bottom wall 166 is arranged to be connected to a base (not shown) which rests on or is fixed to the seabed of the body of water in which the pump 161 is located.

Piston 167 is received by chamber 163 such that piston 167 divides chamber 163 into a working side 168 and a blind side 169 and piston 167 is capable of sliding back and forth within chamber 163. A seal (not shown) between the piston 167 and the sidewall 164 prevents fluid from flowing past the piston 167 and between the working side 168 and the blind side 169.

A piston rod 170 extends from piston 167 and through an opening in a top wall 165 of pump body 162, allowing rod 170 to move back and forth with piston 167 relative to pump body 162. A seal (not shown) prevents fluid from leaking out of the chamber 163 through the opening.

The pump 161 also includes an outlet check valve 171, the outlet check valve 171 being connected to the blind side 169 of the pump 161. Check valve 171 prevents fluid from flowing back therethrough toward pump 161.

Although not shown, the buoyant actuator is connected to the upper end of the piston rod 170 by a cable.

A trim or work side hydraulic accumulator 172 is connected to the work side 168 of the pump 161 by a hose 173. Accumulator 172 is connected to outlet hydraulic accumulator 174 through outlet check valve 175, outlet check valve 175 preventing fluid from flowing back therethrough toward pump 161. A controllable outlet valve 176 connects the outlet accumulator 174 to the heat exchanger 177. The heat exchanger 177 is connected to an intermediate hydraulic accumulator 178 by a check valve 179, through which the check valve 179 prevents fluid from flowing back towards the heat exchanger 177. The controllable inlet valve 180 is connected to an inlet check valve 181, the check valve 181 being connected to the working side 168 of the pump 161 and preventing fluid flow therethrough away from the pump 161. An inlet hydraulic accumulator 182 is connected to the working side 168 of the pump 161 through a check valve 181. Turbine 183, check valve 184 are connected in parallel with valve 176, heat exchanger 177, accumulator 178, check valve 179 and valve 180. The turbine 183 drives a generator 185.

The pressure relief valve 186 is connected in parallel with the valve 176, the heat exchanger 177, the accumulator 178, and the check valve 179. The pressure relief valve 186 is used to prevent over-pressurization of the high pressure side of the hydraulic line of the device 160. The pressure relief valve 186 may be a controllable valve.

Check valve 171 is connected by a hose 188 to the drain/blind side of hydraulic accumulator 187 and also to a make-up electric pump 189. Check valve 190 connects pump 189 in parallel with check valve 181 and accumulator 182. Check valve 190 prevents fluid flow therethrough toward pump 189.

The pump 189 is capable of pumping hydraulic fluid accumulated in the blind side of the hydraulic line including the accumulator 187 back to the working side of the hydraulic line connected to the outlet of the pump 189.

Referring to fig. 9, the generator 185 supplies power to the charging device 191, and the charging device 191 is connected to the external battery charging module 192. The charging device 191 and/or the external battery charging module 192 charges the battery 193 and the battery 194. Electric power is supplied to the electric pump 189 through the battery 194. The instrumentation and control system/controller 195 is powered by a battery 193.

The plurality of sensors 196 are connected to one or more inputs of the controller 195. Sensors 196 include different types of sensors, including pressure sensors, temperature sensors, and flow sensors that detect the pressure, temperature, and flow of hydraulic fluid within device 160.

The outlet valve 176, inlet valve 180 and make-up electric pump 189 are connected to the output of the controller 195 so that the controller 195 can control the operation of the outlet valve 176, inlet valve 180 and pump 189. The controller 195 may control the operation of the outlet valve 176, the inlet valve 180, and the pump 189 in response to the output of the sensor 196. In other words, the controller 195 may control the operation of the outlet valve 176, the inlet valve 180, and the pump 189 in response to the pressure, temperature, and flow detected by the sensor 196.

The pressure relief valve 186 may also be connected to an output of the controller 195 such that operation of the valve 186 can be controlled by the controller 195.

The controller 195 may control the outlet valve 176, the inlet valve 180, the pump 189, and/or the pressure relief valve 186 such that the device 160 is able to extract, convert, or transfer an optimal or near optimal amount of energy from the wave motion of the body of water in which the device 160 is located.

Varying the suction and discharge pressures of the hydraulic circuit allows for some control of the piston stroke. The range of mean piston stroke limits/ranges of piston displacement of a hydraulic device such as device 160 with respect to/versus mean control pressure (Hsig 0.45m, Tsig 3 s)/different suction and discharge pressure ranges over a period of constant wave conditions are shown in fig. 10. It can be seen that the minimum value of the piston displacement range increases as the suction pressure range and the discharge pressure range decrease. Similar charts or graphs of other types of wave conditions may also be obtained.

The hydraulic system/device 160 is a closed loop system/device 160 capable of maintaining the proper pressure at the pump inlet and outlet. When the pump is activated, pressure and flow are created in the hydraulic circuit. The pressure of the hydraulic circuit is controlled by 2 control valves 176, 180, one control valve (i.e., outlet valve 176) controlling the pressure of the output pump 161. Another control valve (i.e., the inlet valve 180) controls the pressure input to the pump 161. These valves (outlet valve 176 and inlet valve 180) are the 2 main control "levers" in the system/device 160. The control valves 176, 180 are remotely controlled to vary the pressure for different wave conditions. For this system setup, the pelton turbine is replaced by 2 control valves and a heat exchanger 177 for consuming the energy generated by the pump 161. At the blind side 169, there is no fluid transfer. A partial vacuum is created during the expansion of the pump. In the event of a leak through the interior of the piston seal, fluid will be discharged through the leak tube and check valve 171 will prevent fluid from flowing back to pump 161 during expansion of pump/piston 167/piston rod 170.

The rod/trim/work side hydraulic accumulator 172 is important in the optimization of the system/device 160. Adjusting the gas charge and volume of the accumulator 172 allows for control of the energy flow and the dynamic variation of the energy flow. Also, one feature of the closed loop system/arrangement 160 is that the dynamic variation effect is similar to a "water hammer," i.e., momentum transfer effect, which can be mitigated by appropriate adjustment of the modulation/working side hydraulic accumulator 172 and the outlet and inlet accumulators 174, 182. The momentum transfer effect may be caused by one or more check valve bounces (bouncing).

The pressure relief valve 186 prevents the system/device 160 from over-pressurizing. The system/device 160 includes accumulators 172, 174, 178, 182 on the rod/work side 168 of the pump 161 to allow for the storage of hydraulic energy and control of pressure changes. The drain/blind side accumulator 187 stores hydraulic fluid resulting from internal leaks at the pump or system level before it is re-pressurized to the primary (i.e., working side) hydraulic line of the device 160. The check valves 171, 175, 179, 181, 184 ensure that the hydraulic fluid flows through the hydraulic circuit in the correct direction. There is also a trim/work side hydraulic accumulator 172 before the pump outlet check valve 175 to trim the system/device 160 and optimize the energy produced.

The flow of fluid through the device 160 can be varied between a "soft" state and a "hard" state. In the soft state, which corresponds to the lowest load on the pump 161, the relief valve 186 is fully open, allowing most of the fluid to be pumped through the valve 186. In a hard state, which corresponds to the highest load on the pump 161, the pressure relief valve 186 and the inlet valve 180 are fully closed, and the outlet valve 176 is fully open.

A small battery operated pump (i.e., the makeup electric pump 189) returns fluid lost to internal pump leakage from the working side 168 of the pump 161 to the blind side 169 of the pump 161.

As described/shown in fig. 9, all instrumentation/sensors 196, valves 176, 180 and return/makeup motor pumps 189 are connected to a locally installed control system/controller 195. System/device 160 includes 2 batteries 193, 194. The main battery (i.e., battery 193) supplies power to the instrumentation and control systems, including instrumentation/sensors 196, valves 176, 180, and control system/controller 195. The auxiliary battery 194 supplies power to the replenishment pump 89 and auxiliary equipment.

Referring to fig. 11, a closed loop hydraulic apparatus 200 for extracting energy from wave motion or converting wave energy includes an axial flow hydraulic pump 201, the axial flow hydraulic pump 201 including a pump body 202 defining a chamber 203. The pump body 202 includes a side wall 204, the side wall 204 having an upper end closed by a top wall 205 and a lower end closed by a bottom wall 206. The bottom wall 206 is arranged to be connected to a base (not shown) which rests on or is fixed to the seabed of the body of water in which the pump 201 is located.

The piston 207 is housed by the chamber 203 such that the piston 207 divides the chamber 203 into a working side 208 and a blind side 209 and the piston 207 is able to slide back and forth within the chamber 203. A seal (not shown) between the piston 207 and the sidewall 204 prevents fluid flow through the piston 207 and between the working side 208 and the blind side 209.

A piston rod 210 extends from the piston 207 and through an opening in the top wall 205 of the pump block 202, allowing the rod 210 to move back and forth with the piston 207 relative to the pump block 202. A seal (not shown) prevents fluid from leaking out of the chamber 203 through the opening.

The pump 201 also includes a check valve 211, the check valve 211 being connected to the blind side 209 of the pump 201.

Although not shown, the buoyant actuator is connected to the upper end of the piston rod 210 by a rope.

A rod/trim/work side hydraulic accumulator 212 is connected to the work side 208 of the pump 201 by a hose 213. The accumulator 212 is connected to an outlet hydraulic accumulator 214 through a check valve 215. A controllable outlet valve 216 connects the outlet accumulator 214 to a turbine or pelton wheel 217 so that hydraulic fluid flowing out of the valve 216 can rotate the turbine or wheel 217. The turbine or wheel 217 may be connected to a generator (not shown) such that rotation of the turbine or wheel 217 can drive the generator, which thereby produces or generates electricity. The output or outlet of the turbine or wheel 217 is connected to a water tank or reservoir 217, allowing low pressure hydraulic fluid flowing from the turbine or wheel 217 to flow into the reservoir 217 as indicated by arrow 218. The turbine or wheel 217 is connected to the working side 208 of the pump 201 by means of a pump 219, a controllable inlet valve 220, a check valve 221 and a hose 213. Pump 219 may be used to pump fluid toward pump 201. An intermediate hydraulic accumulator 222 is connected to the working side 208 of the pump 201 in parallel with the pump 219 and the inlet valve 220. An inlet hydraulic accumulator 223 is connected to the working side 208 of the pump 201 in parallel with the check valve 221. The pressure relief valve 224 and the pressure relief valve 225 are connected between the high pressure side of the hydraulic line connected to the working side 208 of the pump 201 and the low pressure side of the hydraulic line. Pressure relief valve 224 and/or pressure relief valve 225 are controllable.

Check valve 211 is connected by a hose 227 to a drain/blind side hydraulic accumulator 226 and also to a make-up electric pump 228. A check valve 229 connects the pump 228 to the water reservoir 217. The pump 228 is capable of pumping hydraulic fluid accumulated in the blind side of the hydraulic line including the accumulator 226 back into the reservoir 217, which reservoir 217 is located on the working side of the hydraulic line connected to the outlet of the pump 228.

All components of the device 200 located on the left side of the wave line 230 are located in the offshore body, while all components of the device 200 located on the right side of the wave line 230 are located onshore.

Although not shown in fig. 11, device 200 may include means for providing power to the various components of device 200. For example, if the turbine or pelton wheel 217 drives a generator, the generator will supply power to the charging device. The charging device and battery charging module may charge one or more batteries of the device 200 that provide power to the various power components of the device 200.

A respective air or gas charging line 231 connects the respective accumulator 212, 214, 222, 223, 226 to one or more onshore charging sources (not shown).

Like device 160, device 200 may also include instrumentation and a control system/controller (not shown). The controller may be powered by the battery of the device 200.

A plurality of sensors (not shown) are connected to one or more inputs of the controller of the device 160. The sensors may include different types of sensors, including pressure, temperature, and flow sensors that detect the pressure, temperature, and flow of hydraulic fluid within the device 200.

The outlet valve 216, inlet valve 220, and make-up pump 228, pressure relief valve 224, and/or pressure relief valve 225 may be controlled by a controller. The controller may control the operation of the outlet valve 216, the inlet valve 220, the charge pump 228, the pressure relief valve 224, and/or the pressure relief valve 225 in response to the output of sensors connected to the input of the controller. In other words, the controller may control the operation of the outlet valve 216, the inlet valve 220, the make-up pump 228, the pressure relief valve 224, and/or the pressure relief valve 225 in response to the pressure, temperature, and flow detected by the various sensors.

The controller may control the outlet valve 216, inlet valve 220, make-up pump 228, pressure relief valve 224, and/or pressure relief valve 225, enabling the apparatus 200 to capture, convert, or transfer an optimal or near optimal amount of energy from the wave motion of the body of water in which the apparatus 200 is located.

The working side 208 of the pump chamber 203 has a single line/hose/line to which a trim/working side hydraulic accumulator 212 is connected. An onshore drain/blind side hydraulic accumulator 226 and makeup electric pump 228 divert fluid leaking from the blind side 209 of the pump 201 to the inlet line of the main hydraulic line connected to the working side of the pump 201. A pressure relief valve 224 connects the outlet and inlet lines of the main hydraulic line at the offshore end of the circuit adjacent the pump 201. The pressure relief valve 224 provides fail-safe against over-pressure in the main hydraulic line. Pressure relief valve 225 (which may or may not be provided, if provided, located onshore) provides redundancy in the event of a failure of offshore pressure relief valve 224.

The outlet flow of hydraulic fluid drives the turbine 217 and the spent/low pressure fluid at the outlet of the turbine 217 is returned to the reservoir/sump tank 217 for pre-pressurization and return to the pump 201. A pipe 231 with an arrow at its end leads to shore and is the control point. The gas charge in the lines 231 of the different accumulators may be different from onshore according to the control algorithm.

The function of the outlet control valve 216 may be performed by an inlet valve or a gun type valve (spearvalve) for the pelton turbine/wheel 217, wherein a single outlet valve 216 assembly is not required as it is contained in the pelton turbine/wheel 217.

Referring to fig. 12, a closed loop hydraulic system 250 for extracting energy from wave motion or converting wave energy is similar to the apparatus 200 except that the apparatus 250 includes a bank of 8 axial flow hydraulic pumps/Wave Energy Converters (WECs) 201, each pump 201 having a respective trim/work side hydraulic accumulator 212 and check valves 215, 221 connected to the work side 208 of the pump 201. The device 250 emulates a device comprising a plurality of CETO^TM"full scale system of wave energy converter units.

Each check valve 215 is connected to manifold 251 and each check valve 221 is connected to manifold 252. The manifold 251 is connected to the outlet hydraulic accumulator 214 and the manifold 252 is connected to the inlet hydraulic accumulator 223.

The blind side of each pump 201 may be connected to one or more drain/blind side hydraulic accumulators 226 through one or more hoses 227 and check valves 211 and to a makeup electric pump 228, which makeup electric pump 228 may be connected to the reservoir 217 of the apparatus 250 through check valves 229.

Respective air/gas charging lines 231, depicted as asterisks, connect the respective accumulators 212, 214, 222, 223, and 226 of the apparatus 250 to one or more onshore charging sources (not shown).

Typically, the pump 201 of the apparatus 250 will be arranged so that no more than 3 rows are present.

The pumps 201 may or may not be identical pumps.

In a typical installation/installation of the type shown in fig. 12, the installation may include multiple arrays of 8 pumps 201 connected together at sea and having marine ponding (offset marine accumulation) that provides flow to a turbine/pelton wheel 217 onshore. An onshore external pump 219 feeds flow back to the pump to drive the piston of the offshore pump 201 down. This is schematically illustrated in fig. 12 as an example. Alternatively, pressurized hydraulic fluid on the turbine/pelton wheel 217 may be used to supply flow back to the pump 201 to drive the piston of the pump 201 downward.

An operable power station using a pump or point (point) WEC can configure any number of units; the number of units is determined by the total power output needs of the power station. A point WEC is to be understood as any WEC that behaves as a single point absorber of energy.

Different systems for controlling and optimizing a wave power assembly have been described above. The wave power assembly comprises a wave power converter (WEC) using a WEC with a hydraulic power output, e.g. CETO^TMWECs of a particular type, such as wave energy converters. The WEC operates in closed loop mode. The closed loop includes the plant outlet line at a higher pressure and the inlet (return) fluid line at a substantially lower pressure. The circulation of fluid in a closed loop is generally water-based. The fluid transfers energy to shore. Fluids transfer energy by pressure and flow. Furthermore, there is provided a means for removing energy from the onshore working fluid by means of a hydro-mechanical device, such as a turbine or a pressure exchange engine.

The system may include control elements located onshore and/or offshore. The control element may comprise valves controlling pressure and flow in the onshore outlet line and the inlet line. Furthermore, the control element may comprise an offshore pressure reducing valve located between the inlet line and the outlet line. The control element may also include a hydraulic accumulator located at sea. Furthermore, the control element may comprise an onshore hydraulic accumulator. One connected to the outlet line and the other connected to the inlet line. Furthermore, the control element may comprise a pressure relief valve located onshore between the inlet line and the outlet line.

The system may use a control algorithm to control the control element. For example, if the control elements comprise hydraulic valves and the gas pressure charges the accumulators, the control algorithm may be used to control them.

The control algorithm may perform one or more of the following functions or have one or more of the following characteristics:

a. between and including the two limits of piston limited and piston free, the mechanical stiffness is adjusted by the volume change (opening/closing valve) of the accumulator of cetoweec. "piston restricted" refers to a situation in which the piston will experience a minimum amount of movement because the movement of hydraulic fluid within the hydraulic line is restricted to the extent permitted by the trim accumulator; "piston free" refers to the situation where fluid is free to flow between the inlet and outlet lines and the piston is free to move under its own weight and the external forces applied to it.

b. Adjusting CETO^TMThe reference position of the piston of the pump of the wave energy converter is adapted to the slow changes in water depth that will occur in the tide.

c. The control elements of the WEC device are adjusted according to the real-time input of the nearby wave measuring device. Such a device can record the instantaneous wave height (H), wave period (T), wave amplitude (θ) and any other relevant parameters that define the sea state and provide real time data to the algorithm.

h. The time interval τ may be over a period τ from seconds to fractions to hoursWithin a range. For example, for continuous irregular sea conditions, the standard marine practice is 20 minutes, for severe sea conditions 3 hours.

j. The control algorithm A may comprise a series of templates F in i)Such that the respective templates cooperate to provide an optimum energy output E for any period of time between the shortest and longest_max. That is, the algorithm A is typically adjusted to provide the maximum full energy E_maxWherein:

k. the specific algorithm A may be selected from the algorithms A_iIs selected from the set of (1), wherein the set A_iIncluding elements limited to one or more of the following conditions:

a. a particular geographic location;

b. specific water depth and water depth measurement;

c. specific categories of wave activity, such as high energy waves, waves at sea, mild waves, waves near shore, or combinations of these waves;

d. a specific time of the year, e.g., winter, summer;

specific structure of wec;

specific physical Structure of WEC, including CETO^TMThe energy release arrangement already described in the co-pending patent application for wave energy converters;

the specific physical state of the WEC corresponds to the time and the state of the operation history of the WEC;

any other change in the structure of wec;

i. the major sea state of the year. For example, the position of the fijiri island on the west australian sea has 6 to 8 major sea states; and

j. a particular safety/emergency condition.

Also described above is a system comprising an array of WECs connected together in parallel to the same set of inlet and outlet lines forming the closed loop system described above.

In a system comprising a set of WECs, the optimization of algorithm a is affected by the wave amplitude. Algorithm A_iAnd a template FEssentially different from a single WEC. Multiple unitThe algorithm of (a) differs from the single-unit algorithm in that it is controlled by the hydraulic interaction between the units.

The above describes a system according to all the above (where algorithm A is_iProduced according to the best screening method).

Single point absorption Wave Energy Converter (WEC), e.g. single CETO^TMThe response of the wave energy converter unit can be mathematically described by means of a power function P (H, T, θ) indicating that in principle the instantaneous power is a function of the instantaneous wave height H, the instantaneous wave period T and the instantaneous angle of the wave amplitude. The actual sea may have multiple wave directions, waves, swells or other possible portions.

The function P represents the instantaneous power.

The generation of the response function P can be obtained in a number of ways:

i. exciting a single WEC using a pulse train of sine wave excitations having a known period T and amplitude H and measuring the instantaneous power P resulting therefrom;

the model accurately describes power output as a function of these variables by simulating inputs to the WEC in finite element models and/or dynamic simulation models.

The above process forms a three-dimensional surface map, commonly referred to as a "power matrix" with respect to instantaneous power versus instantaneous wave period and instantaneous wave height. The power matrix describes the mechanical response of the system subject to sea state and possible applied controls, as described above. For a hypothetical sine wave disturbance, at a given value of wave height and wave period, the integral of the function P with time τ yields the average energy delivered over time τ.

The wave height and period of the actual water waves have random (free) variations in time and space. Temporal and spatial distribution functions are used to describe these variations and the interrelationships between them. The resulting distribution and empirical models such as the Pearson Moskowitz spectrum yield the wave height spectrumDistribution, per unit frequency interval (wave height)²Unit is m²in/Hz. The accuracy of these distribution functions can describe and predict typical wave times at a given location and at a given time of year, depending on how extensive the data records of actual or simulated data obtained at that location are. The more extensive the recording of observations or simulations at that location, the higher the statistical confidence in the predictive power of the model obtained from that data.

Statistical predictive performance of the power output of a WEC at a given location and a given time of year can be obtained from the convolution of the machine response (through the power matrix) and the wave model; i.e. a convolution function. The total expected energy output over time τ is provided by the time integral of the convolution function.

If the convolution function is robust, that is, if it can be used to predict energy output with high statistical confidence, then the function can be used as an optimal screening method to optimize the response of the WEC (i.e., closed loop hydraulic devices such as devices 160, 200, 250). The optimal screening method uses knowledge of the system characteristics and the spectral characteristics of the disturbance driving it (in this case the wave) to maximize a given output (in this case the energy produced by the WEC).

Implementation of the optimal screening method causes the control algorithm A_iAnd its associated control set point and control range, indicated as F, as described above. The optimal screening method results in a control algorithm (as described above) that varies the control elements of the WEC such that the energy output of the device is maximized on the time scale τ.

The method to generate the optimal screening and derivation algorithms is the following for a single wave position:

i. the power matrix for the wave energy converter is determined using the method outlined above. The power matrix will be a function of the state variables of the system, as well as a function of time. The state variables include: the pressure and flow of the outlet and return circuits, the charge pressure and volume of the different accumulators in the system.

Determine the most robust spectrum of sea states for a physical location suitable for the WEC. The above method is used. Most likely any location can be described by a fixed number of major sea states.

Convolving the sea state spectral density with a power matrix. Note that there may be a natural link between the variables of wave height and wave period. The resulting transfer function links the power production of the unit to the state variables of the WEC and the parameters that drive the ocean. This function can be integrated over time to obtain an estimate of the average energy expected output of the WEC over that time interval. The energy estimate is a function of the state variables of the WEC that control the operation of the algorithm and is determined by the parameters of the ocean model that are used to predict the spectrum of the ocean disturbances.

Apply vector computation techniques to perform multi-parameter optimization of the energy function (state variables) and find local or global extrema using standard procedures such as the newton-raphson method. Those skilled in the art of numerical analysis and multivariate optimization are familiar with these techniques and the precise conditions under which they are applied.

v. defining an energy function E_maxThe operating point and the stable operating region of the vector space in (1). This results in template F.

Applying the control system transfer function to the state variables to generate the control algorithm a.

A simulation of the control algorithm was performed to verify the accuracy and stability of algorithm a and set point F.

Repeating the above steps from ii) according to different sea states to fill the space of the desired control law Ai. If the whole also includes variables of the state of the machine, repeat from i).

An important feature of the algorithm development process and subsequent application to WECs is its ability to be inspired, i.e., its ability to learn over the operational life of the WEC. Initial model evaluation of wave statistics at a given location may be unrefined, as the WEC is running and wave-waitingAs more detailed statistical images are built, their predicted confidence level improves over time. Learning is obtained by feeding back information to the algorithm generation process in ii). Likewise, there is an opportunity to inspire processes in the power matrix when information about the aging of the device over operational life is collected and fed back to the algorithm generation process in i). In both cases, the heuristic development leads to algorithm A_iAnd a more complete combination of templates F to optimize energy output under all conditions encountered during the life of the wave energy conversion assembly.

The above description and method apply equally to a wave farm and a plurality of WECs. The only difference here is that more controllable state variables are possible due to the more complex equipment, and

a) there will be an angular relationship in the power matrix called "amplitude" (spread);

b) there will be interactions between the various cells in the WEC array;

c) the distribution of the angles of incidence for sea states will need to be included in the wave modeling.

With respect to optimization, discussion is useful. To optimize the system:

1. firstly, determining a power matrix;

2. the power matrix and the wave model are used to refine and optimize the system transfer function.

3. The transfer function for a particular location is optimized using a robust bopp model for the physical location. The control algorithm functions here.

The formula is as follows:

the waves driving the pump of the above-mentioned device are irregular input regulators, which means that the pump of the device is irregularly driven. Therefore, the device needs to be controlled to maximize the output. The apparatus was controlled using the optimal screening method. The parameters of the system/apparatus are set according to the "recipe" provided by the optimal screening method. The optimal screening will typically be different or vary depending on the location of the device or the season, e.g., summer, winter, etc. This optimal screening may be obtained by testing the system/device using different parameters and/or using a model. Controlling the device according to the optimal screening method can maximize the energy under the power curve of the device.

It will be appreciated by those skilled in the art that variations and modifications to the invention as described herein may be made without departing from the spirit and scope of the invention. Variations and modifications as would be obvious to those skilled in the art are deemed to fall within the broad scope and ambit of the present invention.

In the description and claims, except where the context requires otherwise, the word "comprise", and the like, will be understood to imply the inclusion of a stated element or group of elements but not the exclusion of any other element or group of elements.

In the specification and claims, the word "substantially" or "about" will be understood as a value that does not limit the scope of the word unless the context requires otherwise.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in australia or in any other country.

Claims

1. A closed loop hydraulic apparatus for converting wave energy, the apparatus comprising: a pump for pumping fluid through the device, the pump comprising a pump body defining a chamber and a piston dividing the chamber into a working side and a blind side; a buoyant actuator connected to the piston; an inlet connected to the working side of the chamber enabling fluid to flow from the inlet into the working side of the chamber; an outlet connected to the working side of the chamber enabling fluid to flow from the working side of the chamber to the outlet; and a hydraulic controller controlling the pump by controlling fluid pressures at the inlet and the outlet to optimize the output of the pump in response to tidal and/or sea state changes, the fluid pressures at the inlet and the outlet being controlled in accordance with a control algorithm, wherein the control algorithm is selected from a set of algorithms, the control algorithm being generated in accordance with an optimal screening method, the optimal screening method and control algorithm being generated by:

(i) determining a power matrix;

(vii) performing a simulation of the control algorithm to verify the accuracy and stability of the control algorithm and the set point template;

(viii) repeating steps (ii) to (vii) above according to different sea states to fill the space of the required control algorithm.

2. The closed loop hydraulic apparatus of claim 1, wherein the hydraulic controller comprises: an inlet hydraulic accumulator; an input hydraulic control valve connected to the inlet and the inlet hydraulic accumulator; an outlet hydraulic accumulator; an output hydraulic control valve connected to the outlet and the outlet hydraulic accumulator; a sequence valve connected to the inlet and the outlet; a first outlet pressure sensor connected to the outlet; a flow meter connected to the outlet; a proportional throttle valve connected to the flow meter; and a second outlet pressure sensor connected to the proportional throttle valve.

3. The closed loop hydraulic apparatus of claim 1, wherein the hydraulic controller comprises: a working side hydraulic accumulator connected to a working side of the chamber; an outlet hydraulic accumulator connected to the outlet, an inlet hydraulic accumulator connected to the inlet; an outlet valve connected to the outlet; an inlet valve connected to the inlet; a pressure relief valve connected to the outlet and the inlet valve; an intermediate hydraulic accumulator connected to the inlet valve; a control system; and a plurality of sensors, wherein the control system is operative to control the outlet valve and the inlet valve in response to the output of the sensors.

4. The closed loop hydraulic apparatus of claim 1, wherein the hydraulic controller comprises: a working side hydraulic accumulator connected to a working side of the chamber; an outlet hydraulic accumulator connected to the outlet; an inlet hydraulic accumulator connected to the inlet; at least one pressure relief valve connected to the outlet and the inlet; an outlet valve connected to the outlet; an inlet valve connected to the inlet; and an intermediate hydraulic accumulator connected to the inlet valve.

5. The closed loop hydraulic apparatus of claim 4, wherein the hydraulic controller further comprises: a control system; and a plurality of sensors, wherein the control system is operative to control the outlet valve, the inlet valve and the pressure relief valve in response to the output of the sensors.

6. The closed loop hydraulic apparatus of claim 5, wherein the sensors include pressure, temperature, and flow sensors.

7. The closed loop hydraulic apparatus as claimed in any one of claims 4 to 6, characterized in that the charge in the lines of the working side hydraulic accumulator, the outlet hydraulic accumulator, the inlet hydraulic accumulator and the intermediate hydraulic accumulator can be varied according to the control algorithm.

8. The closed loop hydraulic apparatus as claimed in any one of claims 4 to 6, wherein the outlet valve is a gun type valve for a Pelton wheel.

9. The closed loop hydraulic apparatus as claimed in any one of claims 4 to 6, further comprising: a plurality of pumps for pumping fluid through the device; a plurality of buoyant actuators respectively connected to the pistons of the pumps; a plurality of inlets respectively connected to a working side of a chamber of the pump; and a plurality of outlets respectively connected to working sides of the chambers of the pump, the hydraulic controller including a plurality of working side hydraulic accumulators respectively connected to the working sides of the chambers of the pump.

10. The closed loop hydraulic apparatus of claim 9, wherein the pumps are arranged in an array of no more than three rows.

11. Closed loop hydraulic apparatus as claimed in claim 9, characterized in that the pumps are identical pumps.

12. The closed loop hydraulic apparatus of claim 9, wherein the control algorithm is adjusted to provide maximum full energy.

13. Closed loop hydraulic apparatus as claimed in claim 9, wherein the generation of the control algorithm is heuristic.

14. Closed loop hydraulic arrangement according to claim 9, characterized in that the optimization is achieved by:

(i) determining a power matrix;

15. A method of generating an optimal screen and set of control algorithms for a closed loop hydraulic device for converting wave energy, said method comprising the steps of:

(i) determining a power matrix;

16. The method of claim 15, wherein step (i) is repeated if the control algorithm includes a change in machine/plant conditions.

17. Method according to any of claims 15 to 16, characterized in that the generation of the control algorithm is heuristic.

18. A method according to any one of claims 15 to 16, characterized in that the optimization is carried out by:

(i) determining a power matrix;

19. The method of claim 15, wherein the closed loop hydraulic means for converting wave energy comprises the hydraulic means of any one of claims 1 to 14.