WO2009153787A1

WO2009153787A1 - A system for transformation of ocean wave energy into useful energy

Info

Publication number: WO2009153787A1
Application number: PCT/IL2009/000603
Authority: WO
Inventors: Guy Gavish
Original assignee: Guy Gavish
Priority date: 2008-06-18
Filing date: 2009-06-17
Publication date: 2009-12-23
Also published as: EP2307707A1

Abstract

The invention provides a system for transformation of ocean wave energy into useful energy. The system comprises: a lengthened flexible member capable of conforming to the shape of an ocean wave, and a rigid frame. The flexible member is harnessed on its extremities to the rigid frame. The harnessing allows the flexible member to contact ocean waves and to rise and fall in response to movement of the waves. A mechanical component is included for moving in response to movement of the flexible member. The mechanical component is coupled to and activates a useful device. Winching means may be present for rolling and unrolling the flexible member so as to adapt its operable length to correspond to the wavelength of ocean waves. Mooring means are included for anchoring the system to a specific oceanic location.

Description

A SYSTEM FOR TRANSFORMATION OF OCEAN WAVE ENERGY

INTO USEFUL ENERGY

FIELD OF THE INVENTION The invention pertains to a system for transformation of kinetic energy from ocean waves into useful mechanical or electrical energy.

BACKGROUND

The estimated amount of energy that can potentially be harvested by utilizing the kinetic motion of oceanic waves is calculated at being far greater than that of other renewable energy sources such as wind energy and solar energy. For instance, in certain high energy wave locations such as off the coasts of Australia, Scotland and others, the average wave energy is estimated at 50 Kw/M². In contrast, optimal wind energy is estimated at approximately 0.4-0.8 Kw/M² while optimal solar energy is estimated at only lO W/M².

Numerous attempts have therefore been made to utilize oceanic waves for generating electrical or useful mechanical energy however few systems have proven themselves in terms of cost effectiveness and long-term durability.

The general concept of wave power devices is that the kinetic force of a wave or of a wave group, acts to move specific components of the device, with these components directly or indirectly linked to an electrical generator or other "power take-off systems which generate or store useful energy. Thus movement of these components results in movement of a piston or a turbine thereby transforming kinetic energy to mechanical or electrical energy. In some instances, the energy harvested is used on-site to power desalination of seawater.

Paradoxically, the kinetic force of powerful waves typically results in destruction of wave-harvesting devices placed in the vicinity of such waves, though this formidable kinetic force seems to promise a high energy potential for energy conversion. An additional problem with existing devices for harvesting oceanic wave energy is their complexity and cost. These devices are predominantly large structures, with rigid components, placed in a harsh environment. There is little use of well-proven components. Most proposed devices are challenging in terms of engineering design, deployment and maintenance. Famed prototypes currently being tested include the Pelamis Wave Generator which is a pitching device developed by the Scottish company Pelamis Wave Power and tested in Portugal; the 237 ton Wave Dragon which is an overtopping device jointly developed European model tested off of Denmark; and oscillating water column type devices. These all suffer from high cost and low efficiency.

Simpler and less expensive devices exist, such as heaving devices which rely on a floating buoy anchored to a submerged power take-off. Typically, waves force a buoy to rise and fall, moving an attached piston or other power take-off. Heaving devices are exemplified for instance, in U.S. Pat. Nos. 7,444,810 and 7,245,041 to Olson, and U.S. Publication No. 2008/0100065 Al to Lee. Heaving devices suffer from low efficiency and saltwater damage to the submerged power take-off.

Often, laboratory prototypes of wave energy harvesting devices appear promising, however when they are placed in open sea, where waves strike the device from all directions and with various timing and strength, the moving components are not optimally aimed towards the waves and movement is not synchronized or dependable. The size of the device components, such as the articulated arms of a pitching device, and the size of the buoy in a heaving device, needs to optimally suit the wave-length present at sea in order to achieve sufficient movement which can generate electrical power. While in a laboratory setting, waves are generated at a specific wave-length, and with synchronized timing, in open sea the waves have varying wavelengths, and appear as relatively chaotic wave-groups moving in various directions. This often generates difficulties in scaling up the wave harvesting device and in achieving an efficient system. In the laboratory, 15-20% of estimated potential energy may be exploited, while in open sea, only 5-7% of the estimated potential energy is exploited. Energy efficiency has yet to be attained in wave power energy conversion systems. The need exists for a wave power energy conversion system, which is relatively inexpensive to manufacture, deploy and maintain, and which is energy efficient in converting oceanic kinetic energy into mechanical or electrical energy.

SUMMARY OF THE INVENTION

The present invention thus provides a system for transformation of ocean wave energy into useful energy, said system comprising: a) a lengthened flexible member capable of conforming to the shape of an ocean wave; b) a rigid frame. The lengthened flexible member is harnessed on at least two extremities of the flexible member, to the rigid frame; the harnessing allowing the lengthened flexible member to contact ocean waves and to rise and fall in response to movement of the waves; c) a mechanical component for moving in response to movement of the lengthened flexible member, the mechanical component coupled to and activating a useful device, upon movement of the mechanical component; d) mooring means for securing the system to a specific oceanic location.

Optionally, the lengthened flexible member is formed of a foamed elastomer. The foamed elastomer may be cross-linked Polyethylene Foam. Alternatively, the lengthened flexible member is a woven mat.

Preferably, winching means are included for rolling and unrolling the lengthened flexible member so as to adapt the operable length of the lengthened flexible member to correspond to the wavelength of ocean waves. In such case, a sensor is included, in electrical communication with hardware and software for processing and calculating the average wavelength present at predetermined intervals. The hardware and software are configured to automatically control winching of the winching means to roll or unroll the lengthened flexible member to correspond to the calculated average wavelength. In one embodiment, the sensor and the processing system are programmed to roll and unroll the lengthened flexible member to a length equivalent to ¹A of the average wavelength of ocean waves present.

The lengthened flexible member may have a rectangular or trapezoid shape. Optionally, in use, the rigid frame is substantially parallel to the horizon.

Optionally, the rigid frame may be a multi-hull vessel with an internal zone open to the ocean. The flexible member is harnessed at least partially within the internal zone. One possibility is that the rigid frame is a catamaran.

Optionally, the lengthened flexible member is tightly harnessed at a first extremity of the flexible member, to the rigid frame, and loosely harnessed at a second extremity of the flexible member, to the rigid frame. The mechanical component is then located at the second extremity of the flexible member.

The mooring means may be selected from: slack-mooring anchorage anchoring the system to the ocean floor; and a rigid arm extending parallel to the horizon. The system may further comprise T-elements extendable from beneath the lengthened flexible member; for increasing friction and buoyancy of the lengthened flexible member.

The system may further comprise hinged wing stabilizers associated with the rigid frame or with the flexible member.

Optionally, the mechanical components or the useful devices (c) are selected from: a hydraulic ram, a piston, an elastomeric hose pump, a pump-to-shore, a hydroelectric turbine, an air turbine, and a linear electrical generator.

The system may further comprise at least one of the following: a flywheel, an inverter, an electrical cable system to conduct generated electricity to shore, and an accumulator for storing generated electricity. Optionally, the system further comprises fins attached to the rigid frame, for promoting repositioning of the rigid frame perpendicular to the direction of progression of ocean waves. Optionally, the system further includes a reinforcing grid of cables attached to the flexible member.

The term "flexible member", as used in the present invention, relates to a structural component which is malleable and can bend to accept the sinusoidal shape of an ocean wave. The flexible member may be formed of any material known to man, which can conform to peaks and troughs of ocean waves. The dimensions of the flexible member are suited to obtain a predetermined amount of energy from the system of the invention.

The term "lengthened" in reference to the "flexible member" is intended to convey the notion that the end to end measurement of the flexible member is considerably greater than the width of the flexible member.

The term "capable of conforming to the shape of an ocean wave" in relation to the flexible member, refers to the ability of the flexible member to bend and substantially accept the contour of the ocean surface at a given time. The contour may include that present during high energy ocean waves.

The term "mooring means" is used in the present invention to relate to anchoring or fastening components which fix the system to a specific ocean location. Though in the art, "mooring" generally refers to anchorage to the ocean floor, there is no intention to limit the scope of the invention to that type of anchoring. Rather, the system of the invention may be fastened in parallel to the horizon, and may include, for instance, a rigid arm extending parallel to the horizon to anchor the system to a breaker or to a second vessel.

The term "rigid frame" refers to any scaffolding or vessel which surrounds and retains the flexible member generally at the ocean surface. All or some of the flexible member may become momentarily submerged, however the flexible member remains near the ocean surface where the kinetic wave energy is the highest, and the flexible member continues to rise and fall with ocean waves even in its (partially) submerged state.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated by way of example in the figures of the accompanying drawings, in which like references indicate similar elements and in which: Fig 1 is a general perspective illustration of the system of the invention, with Fig. IA showing the majority of the components, Fig. IB showing flexible member depicted separately from rigid frame, and Fig. 1C showing only rigid frame. Fig. 2A, 2B, and Fig. 3A illustrate perspective views of the flexible member in various configurations conforming to the shapes of ocean waves. Fig. 3b is a side view of same.

Fig. 4 is a perspective view illustrating the system after deployment at sea, including mooring means and ocean waves. Fig. 5 is a perspective view illustrating a specific mooring arrangement comprising hinged winged elements.

Fig. 6 is a perspective view illustrating optional T-elements. Fig. 7 illustrates winching components in perspective view. Fig. 8 is a perspective view of the deployed system and the mechanical component.

Figs. 9-10 are block diagrams illustrating forces acting upon the deployed system. Fig. 11 is a block diagram depicts and calculates the average electrical capacity of the system.

Figs. 12A- 12 I is a printout illustrating a software-based simulation of the acceleration, distances and speeds of the moving components of the system. Fig. 12 I schematically plots the system movement over time, piston movement over time and the energetic capacity of the system over time. DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a novel system for transformation of wave energy into useful energy for powering mechanical or electrical devices. In contrast to most prior art systems, the system of the present invention is relatively inexpensive to deploy and maintain, and is remarkably sea-worthy over extended time.

In general, the system includes a lengthened flexible member, which is capable of conforming to the shape of ocean waves, such that the flexible member rises and falls along with a wave present beneath it. This movement causes movement of a mechanical component to which the flexible member is linked, and in turn, this activates a useful device such as a mechanically operative device, or an electrical generator. Kinetic wave energy is thus turned to linear, useful movement.

The flexible member is harnessed at its extremities to a rigid frame. In one embodiment, flexible member is tightly harnessed at one extremity to the rigid frame, and loosely harnessed at a second extremity to the rigid frame. Winching means may be provided along with a control system and relevant hardware and software which allow automatic rolling and unrolling of the flexible member to correspond to the average wavelength present at a given time. This results in optimal wave energy utilization.

The rigid frame may be a multi-hulled vessel, such as a catamaran. The catamaran preferably has an internal zone open to the ocean, and the flexible member is harnessed at least partially within this zone. A catamaran or other multi-hulled vessel grants stability to the frame, allowing it to ride powerful waves without becoming damaged or flipping over.

The system includes mooring means for anchoring the system to a specific oceanic location.

Referring to Figure IA, the system 10 of the invention is shown, comprising of lengthened flexible member 20, which in one presently preferred embodiment, is comprised of a foamed elastomeric mat, having a lengthened rectangular shape. Flexible member 20 is harnessed at two of its extremities by harnessing cables 30, to rigid frame 40. .

In all referenced Figures associated with the invention, flexible member 20 is illustrated as having a generally rectangular outline, with triangular sketched shapes upon it. The triangular shapes are merely aesthetic and are not intended to be viewed as structural elements necessary for carrying out the invention.

Rigid frame 40 in the embodiment depicted is a multi-hull vessel of the catamaran variety having two pontoons 60a, 60b, and including an internal zone 75 open to the ocean. The lengthened flexible member 20 is harnessed within the internal zone, and allowed to contact the ocean. In use, the rigid frame remains substantially parallel to the horizon.

The flexible member 20 is loosely harnessed by harnessing cables 30 to rigid frame 40 at first extremity 50, allowing the majority of the flexible member 20 to rise and fall in response to movement of ocean waves present beneath flexible member 20. Due to the flexible nature of the flexible member 20, and to capillary forces, flexible member 20 conforms to the shape of ocean waves present beneath. The flexible member 20 is tightly harnessed at its second extremity 100 to rigid frame 40.

First extremity 50 of flexible member 20 is linked to a mechanical component 55; which moves in response to movement of flexible member 20. The mechanical component 55 is coupled in turn to useful device 70, which is activated in response to movement of the mechanical component 55. Thus, the movement of ocean waves is transformed by the system of the invention into useful energy, as movement of the flexible member 20 results in activation of useful device 70. Useful device 70 depicted in Fig. 1 is a linear electrical generator. In the art, useful device 70, with or without the mechanical component, is known as a "power takeoff.

Power take-offs may include: a hydraulic ram, an elastomeric hose pump, pump- to-shore, hydroelectric turbine, air turbine, and linear electrical generator. Parabolic reflectors may be included in the design as a means of increasing the wave energy at the point of capture. The system may further comprise a flywheel, an inverter, an electrical cable system to conduct generated electricity to shore, and an accumulator for storing generated electricity.

Winching means (best shown in Figure 7) and automatic control of the winching means may be included in the invention, for rolling and unrolling the lengthened flexible member so as to adapt the operable length of the lengthened flexible member to correspond to the average wavelength of ocean waves at a given time. This results in optimal wave energy utilization. Preferably, a sensor is included, in electrical communication with appropriate hardware and software for processing and calculating the average wavelength present at predetermined intervals. The hardware and software is configured to automatically control winching of the winching means to roll or unroll said lengthened flexible member to correspond to the calculated average wavelength. Preferably, the length of the flexible member is adjusted to a length equivalent to ¹A of the average wavelength of the ocean waves present.

Referring to Fig. IB, lengthened flexible member 20 is depicted separately from rigid frame 40. First extremity 50 and second extremity 100 of flexible member 20 are shown. Optionally, floats 120a, 120b may be present on extremities 50, 100 of flexible member 20. Alternatively, or additionally, floats may be included on rigid frame 40.

Optionally, submerged fin 80 may be present, contributing to stability of rigid frame 40.

Referring to Fig. 1C, a basic rigid frame 40 is depicted without flexible member 20. Rigid frame 40 is rectangular, having a central area 42 open to the ocean, in which flexible member 20 will be harnessed.

Referring to Fig. 2A, flexible member 20 is shown in concave configuration, conforming to the trough of an ocean wave. Rigid frame 40 is shown in Fig. 2 as a basic scaffold, with fixed floats 130 aiding in attaining buoyancy of the frame 40. IL2009/000603

Referring to Fig. 2B, first extremity 50 of flexible member 20 is loosely harnessed by harnessing cables 30a, 30b to rigid frame 40. Due to the concave configuration of the flexible member 20, brought on by trough of ocean wave, the first extremity 50 has drawn out cables 30 to their most lengthened position, farthest from first end 140 of rigid frame 40. This straining movement of flexible member and cables 30 will be translated by the system into movement of mechanical component and of useful device (power take-off).

Winching means 220 are described herein below in relation to Fig. 7.

Referring now to Fig. 3, system 10 is shown responding to the peak of an ocean wave passing beneath it. In Fig. 3 A, system 10 is shown in perspective view, and in Fig. 3B, in side view. Flexible member 20 has risen above the swell of the wave to a convex configuration, drawing harnessing cables 30 from slack state found when ocean surface is flat, to their extended convex state. Movement of flexible member 20 and of harnessing cables 30 results in movement of mechanical component and in activation of useful device.

According to certain embodiments, the flexible member may be formed of a material selected from: a foamed elastomer, such as polyethylene foam, also termed

"cross-linked PE Foam" and "XLPE foam". Alternatively, the flexible member may be formed of a woven mat such as a bamboo mat or the like. The flexible member may be formed of any material capable of conforming to the shape of ocean waves.

Optionally, a grid of steel cables may be connected to the flexible member for reinforcing the flexible member.

The lengthened flexible member may have a rectangular or trapezoid shape. In one embodiment, the flexible member is formed of a foamed elastomer, and has the approximate measurements ofl5 meters length and 5 meters width.

In one embodiment, the dimensions of the rigid frame are 25 meters width, by 75 meters length. A system of these dimensions is estimated to generate 0.5 Megawatt_*

The rigid frame may be formed of any material, including for instance, aluminum, steel, or carbon fibers/fiberglass. Mooring means are used to anchor the system to a specific oceanic location, and may be slack mooring cables and buoys which anchor the system to the ocean floor. Alternatively, the mooring means may be a rigid arm extending parallel to the horizon which anchors the system to a breaker or to a second vessel. Referring to Fig. 4, system 10 is shown after deployment at sea. Mooring means

150 are depicted beneath system 10. Mooring means 150 comprise anchoring cables 160a,b,c, mid-anchor 170, and hinged winged stabilizer 180, which will be described in conjunction with Fig. 5. Depth anchor 195 rests on the ocean floor and is coupled to the underside of hinged stabilizer 180. Ocean wave 190 is seen peaking under lengthened flexible member 20, with flexible member 20 riding the wave 190 and conforming to the wave 190 such that flexible member attains a convex shape over the wave 190.

In contrast, rigid frame 40 lies beneath the ocean surface and is weighted and moored such that it is less affected by passage of waves than flexible member 20. Referring to Fig. 5, preferred mooring means are shown, comprised of the hinged winged stabilizers 300 disclosed in U.S. Pat. No. 5,095,839 to Peterson. The hinged winged stabilizers 300 of Peterson can open and close upon their midline 310. Any number of hinged winged stabilizers 300 may be utilized. Without being bound by theory, the stabilizers of Peterson and other slack-mooring cables and the like, act to increase resistance on the harnessed flexible member, and prevent the rigid frame from rising and falling to a significant degree with the wave motion. Preferably, the flexible member is allowed to rise and fall, while the rigid frame remains relatively stable in position. The hinged winged stabilizers of Peterson are utilized in the invention as a dynamic anchor, while Peterson disclosed their use for stabilization purposes.

Optionally, fins may be attached to the rigid frame, for promoting repositioning of said rigid frame perpendicular to the direction of progression of ocean waves.

Referring to Fig. 6, optional T-elements 210 are depicted extending from beneath the lengthened flexible member 20; for increasing friction and buoyancy of the lengthened flexible member 20. Upon winching of the flexible member 20, T-elements 210 fold and become wound along with flexible member 20.

Referring to Fig. 7, winching means 220 are depicted, and include, in addition to winch, a battery 230, sensor 240, controller, and appropriate hardware and software connected by circuitry. A waterproof housing protects sensitive elements from the harsh ocean environment. Winching means 220 thus allow automatic winching of the flexible element, to correspond to the wavelength of ocean waves present at a given time, optimizing the energy yield.

Referring to Fig. 8, system 10 is shown after deployment, with flexible member 20 riding the peak of an ocean wave 190. Flexible member 20 conforms to shape of ocean wave 190, and is illustrated as being convex. The strain on harnessing cables 30 due to kinetic movement of ocean wave 190 and of flexible member 20 results in movement of mechanical component 55, and to useful device 70 linked to mechanical component 55.

Referring to Fig. 9, the forces acting upon the deployed system of the invention are schematically depicted. Floats IB, 3B present upon rigid frame, and float 2B upon flexible member (broken convex line), act upwards as shown by arrows. Weight (G) of entire system acts downwards, while tension (T) produced by mooring system is angled downwards as well. Without being bound by theory, dynamic pressure (P) produced by wave passing beneath the system forces flexible member (broken line) upwards, shortening the distance between float 2B and float 3B, and thus the effective length of harnessing cable D23. Harnessing cable D23 is coupled to mechanical component (not shown), thus this effective shortening activates mechanical component and associated useful device. A counterweight may be included in the system to influence the length of the harnessing cable. The flexible member is perpendicular to the direction and force of the ocean wave, thus the resistance of the flexible member is equal to that of a surface with high trailing force. Without being bound by theory, it is assumed that adherence of the flexible member to the ocean surface causes the flexible member to extend upon the ocean surface. Flexible member floats upon ocean waves, thus the energy absorbed from the wave will be maximal, as wave energy is focused at the ocean surface.

Referring to Fig. 10, the forces acting upon the system (described in relation to

Fig. 9) appear as arrows pointed in the appropriate direction in which they act upon the components of the invention.

Referring to Fig. 11, the average electrical capacity of the system is estimated. The wave force is calculated by estimating the weight and acceleration of the harnessing cable. Assuming that if floats IB, 3B were to be tightly harnessed in place, then the harnessing cable would not move and the wave force would be effectively eliminated; then:

The weight of the system is assumed to be equal to the displacement force that the system creates, assuming floating or permanent mooring means are utilized.

If the area beneath the flexible member is 6 m², then weight of the water is 6,000 Kg. If the acceleration of the cable is lm/sec², and the wave speed is 0.5 m/sec, then the force is 60,000 Newton, and the capacity is 30 kilowatt per each meter of width of the system. The transference is calculated as known in the art to be 50-85% of the force, so that the electrical capacity exiting the system is estimated to be 40% of that entering the system.

Referring to Fig. 12, a software-based simulation of the acceleration, distances and speeds of the moving components of the system, upon 1-3 sinusoidal ocean waves, was prepared. The simulation demonstrates the effect of superposition of several waves on the energy efficiency (harvestable energy) of the system. As opposed to a laboratory setting, where wave size, timing and direction are all controlled, in the open sea waves appear as wave groups having different phases such that one wave may cancel out or minimize the effect on the system of another wave. The simulation shows the system deployed upon an ocean with a pattern of several waves of various energies and varied timing.

In the simulation, winching is programmed to roll and unroll the length of the flexible member to correspond to ¹A of the wave-length present at a given time. The following parameters were taken into account: the density and acceleration of the waves, the height of the waves, the displacement based on a specific size system, the distances between various components of the system, (such as first and second floats (buoys), flexible member (blanket).

The measurements taken during the simulation include the rate of change of the distance between the loosely harnessed extremity of the flexible member and the rigid frame.

Plotted on Fig. 12-1 are: a) a schematic of the system vs. wave displacement over time; b) the piston movement based on the simulation; c) the capacity as a function of time elapsed.

EXAMPLES

Example 1

A small scale (1:25) model will be tested in a wave-generating pool, to determine energy efficiency and resilience. The wave characteristics, including wave height, will be decided using the dimensionless Froude number defined as:

C

The Froude number is known in the art for comparing inertia and gravitational forces. It may be used to quantify the resistance of an object moving through water, and compare objects of different sizes. The Froude number is based on a speed/length ratio. In the wave-generating pool, the repetitive wave pattern will include one perfect wave and superposition of two and three waves.

One or more weights will be used to represent the mechanical component and useful device (power take-off), and testing will utilize instrumentation to precisely measure movement, and position of the weights in response to wave occurrence and as a function of time.

Example 2

Using the model of Example 1, several lengths of flexible members will be tested to determine the effect on the energy harvested from the waves.

Example 3

Using the model of Example 1, several materials will be tested for the flexible member.

Example 4

Using the model of Example 1, the effect of small-angle tilting of the system relative to the wave angle, will be tested to determine the effect on energy efficiency.

Example 5 A larger scale (1:5) system will be tested in open sea, as will a final full-scale system (of 25 meters width, 75 meters length). The rigid frame of the full-scale system will have the general appearance of a catamaran.

Energy efficiency will be determined, as will resilience of the system to harsh conditions as occur during stormy weather at high wave-energy locations in the open sea.

Having described the invention with regard to certain specific embodiments thereof, it is to be understood that the description is not meant as a limitation, as further modifications will now become apparent to those skilled in the art, and it is intended to cover such modifications as are within the scope of the appended claims.

Claims

1. A system for transformation of ocean wave energy into useful energy, said system comprising: a) a lengthened flexible member capable of conforming to the shape of an ocean wave; b) a rigid frame; wherein said lengthened flexible member is harnessed on at least two extremities of said flexible member, to said rigid frame; said harnessing allowing said lengthened flexible member to contact ocean waves and to rise and fall in response to movement of said waves; c) a mechanical component for moving in response to movement of said lengthened flexible member, said mechanical component coupled to and activating a useful device, upon movement of said mechanical component; d) mooring means for securing said system to a specific oceanic location.

2. The system of claim 1 , wherein said lengthened flexible member is formed of a foamed elastomer.

3. The system of claim 1, wherein said lengthened flexible member is a woven mat.

4. The system of claim 1, further comprising winching means for rolling and unrolling said lengthened flexible member so as to adapt the operable length of said lengthened flexible member to correspond to the wavelength of ocean waves;

5. The system of claim 4, further comprising a sensor in electrical communication with hardware and software for processing and calculating the average wavelength present at predetermined intervals; and said hardware and software configured to automatically control winching of said winching means to roll or unroll said lengthened flexible member to correspond to said calculated average wavelength.

6. The system of claim 5, wherein said sensor and said processing system are programmed to roll and unroll said lengthened flexible member to a length equivalent to % of the average wavelength of ocean waves present.

7. The system of claim 1, wherein said lengthened flexible member has a rectangular or trapezoid shape.

8. The system of claim 1, wherein in use, said rigid frame is substantially parallel to the horizon.

9. The system of claim 1, wherein said rigid frame is a multi-hull vessel having an internal zone open to the ocean, said flexible member harnessed at least partially within said internal zone.

10. The system of claim 9, wherein said rigid frame is a catamaran.

11. The system of claim 1, wherein said lengthened flexible member is tightly harnessed at a first extremity of said flexible member, to said rigid frame, and loosely harnessed at a second extremity of said flexible member, to said rigid frame, and wherein said mechanical component is located at said second extremity of said flexible member.

12. The system of claim 1, wherein said mooring means are selected from: slack- mooring anchorage anchoring said system to the ocean floor; and a rigid arm extending parallel to the horizon.

13. The system of claim 1, further comprising T-elements extendable from beneath said lengthened flexible member; for increasing friction and buoyancy of said lengthened flexible member.

14. The system of claim 1, further comprising hinged wing stabilizers associated with said rigid frame or with said flexible member.

15. The system of claim 1, wherein said mechanical components or said useful devices (c) are selected from: a hydraulic ram, a piston, an elastomeric hose pump, a pump-to-shore, a hydroelectric turbine, an air turbine, and a linear electrical generator.

16. The system of claim 1, further comprising at least one of the following: a flywheel, an inverter, an electrical cable system to conduct generated electricity to shore, and an accumulator for storing generated electricity.

17. The system of claim 1, further comprising fins attached to said rigid frame, for promoting repositioning of said rigid frame perpendicular to the direction of progression of ocean waves.

18. The system of claim 1, further comprising a reinforcing grid of cables attached to said flexible member.

19. The system of claim 2, wherein said foamed elastomer is cross-linked polyethylene foam