WO1984004119A1

WO1984004119A1 - Apparatus to use wave energy

Info

Publication number: WO1984004119A1
Application number: PCT/AU1984/000061
Authority: WO
Inventors: Thomas Szolnoky
Original assignee: Thomas Szolnoky
Priority date: 1983-04-15
Filing date: 1984-04-16
Publication date: 1984-10-25
Also published as: NO845044L; GB8512113D0; GB2155556A; JPS60501119A

Abstract

An energy conversion system for converting the kinetic energy of water waves of the like, into potential energy in a reservoir. There is provided a ramp (11) up which the oncoming waves run to spill into the reservoir (8A), the attitude of the ramp being variable to accomodate the varying energy in the oncoming waves and at the same time accomodates the varying level of stored water in the reservoir, by means of ramp end (15).

Description

"APPARATUS TO USE WAVE ENERGY" BACKGROUND ART This invention pertains to conversion of the energies in water waves to a marketable product such as electric power.

In the world as it is today a lion's share of the energy that is used is consumed by the industrialized nations, leaving Less Developed countries in an exceedingly competitive marketplace, and in a hopeless catch-22 situation, where they need to moderately industrialize, yet are unable to find the money for the machinery or fuel, without bankrupting themselves.

At the same time, as a result of the geological mishap that deposited the great bulk of known oil reserves in the politically volatile regions of the globe, the world is inflicted with increased tensions and instability that may- prove decisive on the global order and balance. With the positive realisation that oil and with it all fossil fuels are finite and diminishing, and the awareness to the potentially serious penalties imposed upon the general public and the environment as a whole by the extensive use of fission power, increasing attention has been focused onto alternate energy sources, among these renewed interest for devices for utilizing the energy carried by water waves.

Ever since man's fascination began with the sea, he has devised schemes around it that would benefit him. The idea of extracting the energy transported by water waves and converting it into more usable forms is not new either. Among the earliest of date and still surviving documents describing methods of exploiting this abundant and free energy form provided by Nature, is the patent filed in Prance on July 12, 1799 by a father and son named Girard. Since the times of the Girards there have been in excess of a thousand patented devices around the world and yet, looking around the globe today there is not a single operational wave energy device converting a sizeable amount of energy available from the seas. The basic reasons could be summed up by: (a) lack of investment into Research and Development

(b) nature of the exploited source

(c) no presently known technique or idea that could reasonably satisfy most of the requirements for a full scale wave energy conversion project.

The present invention is addressed to a method, device and system for harnessing the energies of water waves, in a manner overcoming the severe technical and engineering difficulties presently experienced with known methods and devices due to the "nature of the exploited source" and to lay the foundation for a practical and full scale wave energy project by "reasonably satisfying most of the requirement" for the successful undertaking of such a scheme. Surface water waves, where the restoring force is provided by gravity, are the most notable forms of ocean energies. Basically, they are disturbances, in the physical medium of water, responsible for transporting energy away from its source. Water waves may occur in response to wind, seismic or gravitational effects or due to relative motions. Wind waves may be considered to be secondhand solar energy, since the primary driving forces of the wind are the air currents established by the uneven absorption of solar radiation by massive colectors like land and water, and the consequent transferral of energy to the air masses in the form of heat. As a result of the frictional drag existing between the surface of calm water and the air mass in relative motion above it, first ripples are formed on the water's surface, due to this drag and as the ripples present a move pronounced obstacle against which the wind can apply its force directly, a multitude of small wavelets of differing dimensions are created. The trend in this the "generating zone", that may cover many thousands of square kilometres, is for wave heights to increase, steepening the crest to a limit, where no more energy can be accepted by the wave, subsequently the force of the wind blowing the crest off, forming a breaker on the open sea. The energies liberated are lost in turbulence and to overtaking waves better able to accept the extra input. Longer waves unde.e^ξ

_ O similar conditions in the generating zone are better suited to absorb energy and survive, than shorter ones, that reach maximum height rapidly and are destroyed. As the sea waves move out of the generating zone, their character changes, the crests become lower and more rounded, wave profiles become more sinusoid and waves with relatively great length and small height will prevail, this type of disburbance is known as "swell".

Velocity of water waves depends on the relative ratio of the wave lengths and the depths of water in which they are propagated. The distinction between deep- and shallow-water waves becomes observable as swell approaches the shore, where their velocity is controlled more and more significantly by the depth. Transition from deep- to shallow-water waves is associated with refraction due to the wave interaction with the sea bed, and as a result, they undergo modification due to slowing by refraction, resulting in the familiar sight and sound of a "breaker". Observing swell approaching the shoreline on a macroscopic scale, one would see the motion of fluid particles in sinusoid deep-water wave to be in closed circular orbits, whose radii decrease exponentially with depth, and most importantly water particles would not be observed to travel along with the wave form. In the region of intermediate water depth, observing fluid particles paths would reveal that they have become elliptic with major and minor axes that decrease with depth. Further in shore, in shallow-water, paths taken by particles are still elliptic, however with constant major axes and with minor axes that decrease with depth, moreover, particles close to the surface travel as far and fast in the horizontal direction as particles close to the bottom. The significance of this trend in paths taken by fluid particles during shoaling is the trend from circular to elliptic orbits and onto linear motion directed toward the shore. In the above process the wave changes from having the oscillatory characteristics of transporting energy but not water, to linear motion of translation where the waves carry both water and energ toward the shore. The energy transported by a sinusoid deep-water wave is considered to be the sum of the potential energy, represented by the elevation of the gravitational mass centre in the wave above sea level, and the kinetic energy dependent on the motion of water particles.

Breaking waves may be classified into four main categories:

(a) spilling type, a steep symmetrical wave with a layer of turbulence moving down the forward slope.

(b) plunging type, a violent breaker with a sheet of water shooting out of the crest and dropping into the trough below, quickly dissipating most of the energy carried by the wave in the succeeding turbulence.

(c) collapsing type, where the wave over turns not at its crest but lower down the forward slope, forming a region of turbulence, dissipating energy.

(d) surging type, where the wave advances against a steep beach at a relatively high velocity, with only a small

^" region of the turbulence being present at the advancing face. Little energy is lost in the turbulence and as a result most of the energy carried by the wave is dissipated against the rise of the beach and bottom friction. In category (d) the offshore oscillatory wave has been replaced by a volume of water exhibiting linear motion, directed up the inclined slope generated by the beach, gradually losing the kinetic energy of motion due to the influence of gravity and acquiring a corresponding value of potential energy as a result of the elevated position reached.

Wave energy, as being the product of the wind's driving force is diffused, that is, the energy density per unit of area of water surface is relatively small in comparison with conventional, non-renewable sources. Resulting in proposed wave energy devices that are in-variantly extensive in scope and therefore expensive in construction in order to intercept a sizeable incident wave energy, for conversion into a usable form. Apart from this major handicap of diffuseness most wave energy devices require that the wave energy is extracted by changing wave motion to a primary energy source stored in either mechanical, hydraulic or pneumatic forms. This creates severe engineering problems for the conversion of this primary source to a usable product such as electric power, due to the fact that the energy transfer from waves into the primary source occurs in a slow and irregular fashion, while present technology for electric power generation calls for fast and regular movements. The above should be indicative of the significance of defining the overall efficiency of a wave energy conversion device, performing the process to a marketable product, as the function of the efficiency of extraction (changing of wave energy into the primary source) and conversion (changing the primary source into usable product). For this reason the analogy should be obvious, that while a number of device concepts are able to extract wave energy efficiently, the active system in most instances may be much less efficient, as a result of the conversion process to a marketable product.

Besides overall efficiency, there are also numerous other parameters that must be considered in evaluating a wave energy device. In the assessment of a system considerations must be given to: survivability, construction, positioning, mooring and anchoring, reliability, maintenance, power transmission, sea state, tidal conditions, environmental considerations, obstruction to navigation, aesthetics.

Most of the presently known wave energy devices are designed for operation in the open oceans, due to the greater energy transported by deep-water waves than waves close to shore. However, the open oceans are extremely hostile environment for these large proposed structures encompassing sensitive internals to survive and reliably function for extended periods. Designs must be able to withstand not only forces due to the heaviest predictable wave actions, but attacks from chemical corrosion, as well.. For the above reason it would appear that a device located and operating closer inshore, in relative safety, would not necessarily be less preferable to a device positioned far offshore, subject to the full force of the elements, as the loss in conversion capacity is generously offset by the benefits gained. Considerations must also be given to the extent and costs of additional project(s) required in order to "firm up" the power delivered by the wave energy device, that is to provide for partial or total back-up during periods of low wave actions.

It is an object of the present invention to positively satisfy most f the parameters, which are taken into consideration for evaluating a wave energy conversion device-system. It is in addition an object of the present invention to set forth a water wave energy conversion device, which is adjustable to provide maximum extraction and conversion efficiencies leading to a marketable product, such as electric power, for any particular set of sea states and tidal conditions.

It is in addition an object of the present invention to provide a water wave energy conversion system, with capacity for an efficient level of water management and conservancy, providing "firm" power delivery. That is, supplying a steady electric power output relative to the level of power demand, regardless of the time variant nature of sea states, tidal conditions and power demand.

It is also an object of the present invention to convert the energy in water waves into a marketable product, such as electric power by means of a device which may be partially or totally submerged for protection from the damaging forces of the elements, as during intense storms.

DISCLOSURE OF INVENTION In pursue of the above set out aims: Central to most wave energy conversion systems is a device whose function is to extract the energy transported by waves into some other more convenient primary source. The present energy conversion device exploits the energies in waves by raising masses of water to an elevation corresponding to a relative increase in the potential energy of said mass, due to the force of gravity acting on it. It is by "dropping" masses of water via the "hydraulic head"

hydroelectric turbines in the process, that conversion to marketable product may take effect.

The "extracting mean" basically consists of the following sections: dyhedral (or funnel shaped) entrance; channel section, including slab structure, which may be raised or lowered by a single or a combination or various methods; reservoir whose confine is at least in part defined by the abovementioned slab structure, and which reservoir receives its supply of water from the channel section. The "conversion mean" basically consists of suitable conduits from reservoir via hydro-electric turbines to discharge outlets.

In the form of a wave energy system with capacity for efficient level of water management and conservancy, providing firm power delivery, the present invention in addition consists of suitable conduits linking various water stations in the system via pumps to an elevated water catchment area, returning through hydro-electric turbines to discharge outlets. Many other features and additional objects of the present invention will become manifest to those versed ^• in .the art, upon making reference to the detailed description and the accompanying sheets of drawing in which various structural embodiments are shown by way of illustrated examples. It is to be expressly understood, however, that the drawings are for purpose of illustration and description only, and are not intended as a definition of the limits of this invention.

The invention in its broadest form comprises an energy conversion system for receiving transported energies in a body of water comprising: a slab structure located in a channel housing said slab structure having side walls that abut the side walls of the channel housing a front end open to the body of water and a rear end facing in the direction of a water receiving reservoir, said front end of the slab structure being hingedly mounted towards the water end of the channel housing and the rear end of the slab structure being adapted to be raised or lowered between the channel side walls depending on the level of the energies in the oncoming water to form a sloping surface up which the oncoming water runs to spill into the reservoir, said rear and also forming at least part of the adjustable height of a wall of the reservoir, if required

A preferred form of the invention will now be described with reference to the drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows paths taken by water particles at various water depth.

Figure 2 shows a schematic view of wave energy conversion system.

Figure 3 side elevation of extraction mean, with slab structure in elevated position. Figure 4 side elevation of extraction mean, with slab structure in rest position.

Figure 5 show plan view of seal assembly lay out.

Figure 6 is a sectioned end elevation of seal assembly.

Figure 7 is sectioned elevation of slab structure along line A-A' .

Figure 8 shows a schematic view of free end of slab structure. Figure 9 shows method for locating fixed end of slab structure.

Figure 10 shows a further arrangement for locating fixed end of slab structure.

Figure 11 is a flow chart of information processing and commands.

Figure 12 water stations with relative connections.

BEST MODE OF CARRYING OUT THE INVENTION

For the particular embodiment of the present invention, which will now be disclosed, and described with reference to the accompanying drawings, it is to be expressly understood, that the method of description of distinguishing between the elements constituting the embodiment, and the reference to these elements as "extraction mean", "conversion mean" and "system mean" are for purposes of illustration and description only, and are not intended as a definition of the limits and scope of these said elements, embodiment or of the invention.

Referring now to Figure 2 where a particular embodiment of the extraction mean of the water wave energy conversion system is illustrated. Here is depicted in simplified forms: a large body of water (such as a sea) in communication with dihedral entrance 2, whose extent is defined by training walls 3 and 3A and bottom surface contour 4; also is depicted a channel section 5 in communication with dihedral entrance 2 which channel section 5 extent is defined by walls 6 and 6A and bottom surface contour 7; in addition is depicted a partially confined reservoir 8, in communication with channel section 5, which partially confined reservoir 8 extent is defined by base contour 9 and partially confining boundary 10. Inside channel section 5 a movable slab structure 11 is ' located in such a manner, that the freedom of movements allowed for slab structure 11 within channel secion 5 is restricted to rotations of slab structure 11 between walls '6 and 6A about axis 12. Said axis is 12 being in a location of close proximity of bottom surface contour 7 and is directed through fixed end 13 of slab structure 11, perpendicular to the longitudinal axis of symmetry of channel section 5.

Free-end 14 of^' slab structure 11 exhibit face 15, which is preferably a curved surface, so as to allow for sustaining a minimal distance of uniform separation between face 15 and similarly curved adjacent surface 16, during the controlled movements (or manipulations) of slab structure 11. Sides 17 and 17A of slab structure 11 also maintain a minimal distance of uniform separation away from adjacent walls 6 and 6A, during the manipulations of slab structure 11. As the above movements of slab structure 11 take effect edge 18 formed at the intersection of upper-surface contour 19 and face 15 will have displacements away from bottom surface contour 7 and base contour 9 of different magnitude in relation to the manipulation of slab structure 11. Signi--_-i-can.ee of the displacements of edge 18 away from base contour 9 are the range of displacements that place the edge 18 at a higher elevation in reference to the elevation of base contour 9 and thereby allowing for face 15 to define a widely confined reservoir 8A. Also significant within said range of displacement are the various angles of inclinations of upper-surface 19 with water surface 20, and the possible diverse lengths of portions of slab structure 11 protruding above water surface 20. Wave_e_nergy_from large body of water 1 enters dihedral entrance 2 of the extraction mean and is guided by training walls 3 and 3A and bottom surface contour 4 towards portion of said dihedral entrance 2, which is in communication with channel section 5. Due to the dihedral entrance 2 geometry, wave energy is compelled to propagate via decreasing dihedral entrance cross sectional areas, which areas are perpendicular to the direction of propagation, resulting in increasing wave energy densities per unit of water surface, as approaching channel section 5. On entry into channel section 5, the transported wave energy is directed, towards slab structure 11 by the combined geometry of walls and 6 and 6A and bottom surface contour 7. Upon encountering slab structure 11 the direction of wave energy propogation is modified by said slab structure 11, deflecting the transported wave energy onto the upper surface contour 19 which upper surface contour 19 is inclined with water surface 20, so as the protruding portion of slab structure 11 above water surface 20 forms a suitable ramp 21 for the transported wave energy by now in the form of moving volumes of water to ascend upon, and said volumes upon reaching edge 18 to be deposited and confined in reservoir 8A.

Having volumes of water originating from large body of water 1 with elevated gravitational mass centres, as in volumes deposited in reservoir 8A_r indicates that said volumes of water confined in reservoir 8A have greater total potential energy, due to their position, than same volumes, as they were in large body of water 1. This suggest that the increased potential energy is gained by the conversion of kinetic energy of water particles in orbital motion, as exhibited by waves in large body of water 1, transporting energy in the direction of didehral entrance 2. The conversion is accomplished in the present invention with the combined hydrodynamic effects of dihedral entrance 2, chanel section 5 and slab structure 11 geometry on motion of water particles within the conversion mean. Ideally, inducing a uniformly smooth, turbulence free transition away from oscillatory to translational wave characteristics, that is from orbital water particle motion to unidirectional linear water particle drift (flow), resulting in moving volumes of water ascending the inclined slope generated by the upper-surface contour 19 of slab structure 11, with portions, of said upper-surface contour 19 protruding above water surface 20, so as said moving volumes ascending said surface 19, increase their potential energy in proportion to their dissipated kinetic energy, resulting from the work done against the force of gravity, due to the rise in elevation reached. Reaching the zenith of elevation, represented by edge 18, said moving volumes of water spill over edge 18 and are deposited in reservoir 8A and confined there by base contour 9, boundary 10 and face 15.

As can be seen from the preceding, the slab structure 11 serves to fulfil a number of functions; some of these are:

(a) inducing the linear drift (flow) in water particles,

(b) generating suitable slope, upper-surface contour 19, for water run up, (c) converting kinetic energy of moving volumes of water to potential energy,

(d) partially defining reservoir 8A,

(e) confining the deposited water in reservoir 8A,

(f) generating ramp 21, protruding above water surface 20, for water "run up".

Due to various sets of sea states and tidal conditions, in order to maximize extraction efficiency, extraction mean geometry must change in relation to the magnitude of wave energies entering the extraction mean during any set of_/^' ^H,

_OM ι , V I: tidal conditions. In other words for similar tidal conditions, the optimum geometry for extraction of heavy wave action will not be ideal for extraction of light wave action, or vice versa, thereby greatly reducing overall conversion efficiency to a marketable product, as a consequence of passive extraction mean.

To provide maximum extraction efficiency for any set of sea state and tidal conditions and to be able to tune into the prevailing dominant band of the wave energy spectrum, the present invention provides for that the moveable slab structure 11 be moveable so as to change the overall channel section 5 and slab structure 11 geometry. Thereby changing the hydrodynamic effects on water particles, so as to induce at all times a mostly uniformly smooth and turbulence free transition away from orbital water particle motion to unidirectional linear water particle drift (flow) within channel section 5, and provide for maximum extraction efficiency during any combinations of prevailing conditions. Slab structure 11 is made adaptable to various sets of conditions by allowing it to pivot around axis 12, thereby having the free-end 14 to mve upr or down relative to bottom surface contour 7, effectively altering the angle of incidence between upper-surface contour 19 and water surface 20 and length(s) of slab structure 11 protruding above water surface 20, which length(s) of protruding portion of slab structure 11 representing a length of suitable ramp 21 for water run up.

More over, due to the close proximity of axis 12 to^" bottom surface contour 7, movements of slab structure 11 will modify the length(s) of significant interaction between water particles in motion and upper surface contour 19, when said length(s) of interaction is measured from edge 18 along upper-surface contour 19 to the point where water particle motion beings to be significatly effected by the hydrodynamic effects of upper-surface contour 19 on said water particles. This being most important for high extraction efficiency, as angle of incidence between upper-surface contour 19 and water surface 20, and the ^U f __gι length of significant interactlo_n___ar_e- two main factors effectijng the rate and duration of energy input into advancing wave form in channel section 5, thereby effecting transformation and possible break and loss of energy, due to turbulence caused.

Therefore overall channel section 5 and slab structure 11 geometry is changed by the manipulation of slab structure 11 in order to vary its attitude within channel section 5 to provide the most favourable arrangement for efficient wave energy extraction, during any combination of sea states and tidal conditions.

In addition, to tune into the prevailing dominant band of the wave energy spectrum, that is to extract the maximum available energy transported by waves for any particular combination of conditions, the slab structure 11 is manipulated so as the edge 18 is at the highest elevation that volumes of water ascending upon upper-surface contour 19 are able to reach and spill over said edge 18 into reservoir 8A. In this manner it is assured, that at the instant of spilling over edge 18 most of the binetic energy of said volume of water is converted to potential energy.

A feature of the extraction mean of the present invention is that the slab contructions 11 is moveable about fixed axis 12 in order to achieve the most favourable overall channel section 5 and slab structure 11 geometry for maximum extraction of energies from water waves. Thus the ability to raise or lower the slab structure 11 on command provides a means for fine-tuning the extraction mean for maximum efficiency of wave energy extraction, for any given sea states or tidal conditions.

In order to raise or lower the slab structure 11 through a range of positions a single or combinations of various mechanical methods (such as hydraulic jacks, steel cables and suitable purely arrangements) may be employed and in addition or alternatively the movable slab structure 11 may cooperate to define enclosed chamber 22. The extent of the enclosed chamber 22 is substantially defined by lower-contour surface 23 of slab structure 11, bottom surface contour 7, walls 6 and 6A and under certain slab structure 11 positions enclosed chamber 22 may in addition be further defined by surfac 16. Through a -number of suitable conduits 24 connected to inlet ports 25 and discharge ports 26 a relatively incompressible fluid (such as water) is supplied into enclosed chamber 22 or discharged out of said chamber 22, so as to raise or lower slab structure 11. Due to the relative incompressability of the liquid (such as water), by altering the volume of fluid within the enclosed chamber 22, the slab structure 11 being the only mobile restriction defining said chamber 22 will be raised or lowered in relation to the volumes of fluid forced into said chamber 22 or discharged out of same. For the sole purpose of illustration it might be useful to point out some other benefits of this particular arrangement and the nature of the relative incompassibility of the fluid supplied to enclosed chamber 22. The fluid supplied to said chamber 22 occupies a given volume and maintains that same volume under large variations of loads, while the volume occupied by a more compressible substance varies with the load. Applying this analogy to the present example, it is obvious that, while the load on the enclosed chamber 22 varies mostly in relation to the mass of water supported by the slab structure 11, the capacity of said chamber 22 filled with a fluid (such as water) will remain substantially constant. However, if the fluid supplied to enclosed chamber 22 is replaced by a more compressible substance, the varying loads upon the slab structure 11 would cause the capacity of the enclosed chamber 22 to alternate, resulting in the undesirable up and down

"bobbing" motion of ^"the slab structure 11. Similarly, while the anticipated dimensions of the slab structure 11 might make it suspect to forces of destruciton, these forces are substantially cancelled or at least minimized by the uniform foundation and support provided by the nature of th fluid (such as water) supplied to the enclosed chamber 22.

For any given combination of sea states and tidal conditions the state structure 11 would be moved to the most favourable position for maximum wave energy , __vre

^ extraction, by altering the capacity of the enclosed chamber 22, by the controlled supply and discharge of fluid via inlet 25 and discharge 26 ports. In addition to (or instead of) the enclosed chamber 22, one or more interconnected flooded compartments 36 may be provided for, inside the slab structure 11. Which compartments 36 may be evacuated systematically of water by the introduction of compressed air, to enable positioning of slab structure 11. The proper position of lab structure 11 would be determined by computing the informations obtained by a number of monitoring devices located at various points in the present wave energy conversion system, and in accordance to the informations coputed for optimum overall conversion efficiency, slab structure 11 is moved by automatic or manual command to assume a position best suited for maximum energy conversion for the prevailing sea state and tidal condition. If conditions become violent enough to threaten the structural integrity of the apparatus, the slab structure 11 may be completely submerged beneath water surface 20 within channel section 5, for as long as is necessary to escape to possibility for damage.

In order to provide sealing means to sealingly contact slab structure 11 and adjacent surfaces in relative motion, as said structure is manipulated, and to prevent undesirable passage of water between various regions within the extraction mean, such as the escape of water from reservoir 8A back into channel section 5, and in order to isolate the enclosed chamber 22, so as to prevent the escape of fluid from said chamber vital for the support and manipulation of slab structure il, and also to similarly isolate the to be described pressure regions 35 and 35A, a system of sealing means are provided. Which sealing means may be effected by any or a combination of the following methods, including an expandable elongated flexible seal extending around the periphery of the slab structure 11, or alternatively a resilient elongated seal may be sandwiched between the slab structure 11 and adjacent surfaces in relative motion as said structure 11 is manipulated. Preferably the seals would be Ipcatd in recesses in the slab.

O structure 11. In addition suitable sealing could be provided by the following mathod. In the present instance sealing means would be provided by a plurality of substantially parallel running continuous recesses 27 formed in the slab structure 11, which said recesses 27 follow paths generally along the periphery of te said structure 11, in which said recesses 27 are located a plurality of abuting sections of resilient blocks 28, thereby forming a plurality of continuous seal assemblies 29 located in said parallel running recesses 27. Sealing effect is provided by having a plurality of prssure zones 30 within said recesses 27, which said zones 30 are located behind seal assemblies 29, so as when th pressure zones 30 are force supplied with a relatively incompressible fluid via a system of condiutis 31 within slab structure 11 and said conduits31 are connected t a plurality of ports 32 in communication with said zones 30, the supplied fluid forces the seal assemblies 29 to engage the corrosion resistant surface 33 covering the adjacent surfaces in relative motion, as slab structure 11 is manipulated. The force with which the seal assemblies 29 are made" to engage the corrosion resistant surface 33 is adjusted in accordance with the movements of said structure 11, that is during the operations of raising or lowering of slab structure 11 the force may be reduced in order to facilitate these movements and minimize wear of seal assemblies 29. As indicated the surfaces that are engaged by said assemblies 29 are covered with a tesselation of smooth and corrosion resistant material to form surfaces 33, thereby minimizing wear to individual resilient blocks 28. To overcome the envisaged problems presented by the requirement of ahving each individual seal assemblies 29 to form continuous bond generally running around the periphery of the slab structure 11, individual resilient blocks 28 have angled abuting faces to reduce to possibility of loss of fluid from pressure zones 30 between said abuting faces of said blocks 28. Moreover, to eliminate the possibility of gaps occurring between resilient blocks 28, due to the co bonation of wear and the nead for the seal assemblies 29 to run from one surface plane of slab structure 11 to

O another, such as from sides 17 and 17A to face 15 (that is along lip 67, which lip 67 serves the function of maintaining a column of water 37 between face 15 and adjacent side 16, so as to balance the longitudinal foces on slab structure 11), and sides 17 and 17A to under side 38 of fixed end 13, specially shaped wear compensating resilient blocks 34 are employed. Said blocks 34 have more or less vedge forms, thereby takingup any gaps that may occur in seal assembly 29, as said block 34 are steadily forced into said assembly 29 by pressure zones 30. In practice, as indicated by Figure 6, the resilient blocks 28 would be located in recesses 27 and subsequently deformed by retainers 39, so as to prevetn escape of pressure lid. For the elimination of possibly lateral movements of slab structure 11, within channel section 5, a plurality of pressure regions 35 and 35A are established within the combined confining boundaries of the seal assemblies 29, and between the internal surfaces of walls 6 and 6A, and adjacent sides 17 and 17A of the slab structure 11. Force suplying the regions with a relatively incompressible fluid (such as water) via a system of conduits within said structure 11 connected to a plurality of inlet and outlet ports in co muncation with said regions 35 and 35A, and subsequently dosing inlet and outlet ports, the slab structure 11 is deprived of subvstantial lateral movements, due to the fact that any movement towards any one of the walls 6 and 6A would require a relative decrase of pressure region capacity located adjacent that wall, which decrease is virtually made impossible by the relative incompressibility of fluid within said pressure region. In short, any firce causing lateral movement on slab structure 11 is met with a restoring force of substantially equal magnitude but opposing direction.

Turning now to the conversion mean of the present invention. As indicated previously the volumes of water deposited and confined in reservoir 8A have greater total potential energy, due to their position, than identical volumes of water, as they were in large body waer 1. Basically the vertical distance between water surface level 40 in reservoir 8A and water surface of said body of water 1 represents the "hydraulic head", which is exploited by the conversion mean, by utilizing the binetic energy liberated to drive one or more hydro-electric turbines 41, as volumes of water are returned from reservoir 8A via said "hydraulic head" through suiatable pipe 57 and said hydro-electric turbines 41 to discharge outlets 42. For maintaining the potential energies possessed by the volumes of water at the instant of being deposited in resevoir 8A, the water level 40 is variable between the lowest drainage point 43 of said reservoir 8A and uppermost edge 18 of slab structure 11. Water level 40 and therefore reservoir 8A capacity is changed by the controlled drainage and/or replenishment of reservoir 8A in unison with the raising and lowering of said structure 11, so as to sustain the water level 40 in the closest practicable horizontal plane to edge 18 of slab structure 11, without having successively deposited volumes of water raising said level . 40 to a plan where over spilling may occur. For example, if the distance between edge 18 and water level 40 is substantial, the volumes of water deposited fall through that distance dissipating a relative amount of energy in the turbulence formed as said volumes strike opposition, thereby reducing the efficience of conversion. The capacity of reservoir 8A is therefore designed with view for maximum efficiency of the overall conversion system. The optimum capacity required is assessed in terms of actual project dimensions and anticipated sea states. As seen, for maximum conversion efficiency water level 40 must be within a certain range of edge 18 of slab structure 11, and since said structure 11 is maniplutated for particular set of sea states and tidal conditions, water level 40 must also move in unison, requiring reservoir capacity 8A to be adequately large for said level 40 not to fluctuate excessively with the intermittent delivery of volumes of water, but sufficiently small to be drained or replenished in harmony with the positioning of slab structure 11 as sea and/or tidal ocnditions change. Due to the time dependent variation in the volumes of water deposited into reservoir 8A and thge corresponding available "hydraulic head", for peak conversion efficiency a number of hydro-elecric turbines 41 may be used, in which set each type of turbine is choosen to meet a particular range of conditions, and are brought onto line at their peak range of operational efficiency.

In order to establish a wave energy system with the capacity for efficient level of water management and conservancy, providing firm power delivery, that is a steady electri power output, meeting the low demand for power at night and peak demand during the day, regardless of variations in sea dn/or tidal conditions energy is stored in a pumped storage installation 44. The pumps 45 could either be separate pumpts coupled to the same shaft as the turbines 41 or completely indpendent motor-driven or reversible-pump turbines, which act as pumps when operating in the reverse direction of rotation, or a combination of these, delivering water to a main storage installation 44, which could be a high elevation natural catchment area or a man-made reservoir. The volume of water that are delivered to the high elevation storage installation 44 during time intervals of light electric power demand such as in storms, may be fed back into the same or different hydr-electric turbines 41, to provide and/or supplement the necessary energy required for conversion into electric power to meet the heavy demand for same during the day and/or in calm seas. For environmental reasons it could become necessary to pump fresh water instead of sea water to the pumped storage installation 44, which could require the establishment of suitable pipes from the pumps 45 to a fresh water source (such as a lake or river).

In order to achieve overall system efficiency (maximum extraction, converions, water conservancy and meeting variousload demands), it is envisaged that an eleborate system of controls coupled to a number of monitoring and sensing devices will be required. Figure 11 shows a flow chart of such a system. Where: 46 - computing informations for various commands; 47 - long range forecast of sea states and tidal conditions; 48 - prevailing se states and tidal conditions; 49 - slab structure 11 postion; 50 - reservoir 8A water capacity; 51 - pumped storage installation 44 water capacity; 52 - electric power demand; 53 - forces acting on slab structure 11; 54 - hydro-electric turbines 41; 55 - pumps 45; 56 - positioning slab structure 11.

Figure 12 shows the different water stations 68 in the overall energy conversion system, interconnected by a number of water carrying pipes 57, with flow being directed and regulated by a number of control valves 58.

Construction of the slab structure 11 could be carried out by employing on site construction techniques, using heaving reinforced and prestressed concrete elements due to the fact that concrete finds a hospitable environment in to oceans and is relatively inexpensive, yet functional and easy material to work with, possessing immense strenght. The fixed end 13 may be captively located by a number of methods. One of these could be by constructing a large diameter pivot shaft, supported on th two ends by walls 6 and 6A, using concrete reinforced with a steel internal skeleton and lined on the outside with a tesselation of steel plates, forming a smooth and circular cross sectioned load bearing surface. The fixed end 13 is then systematically constructed around the pivot dhaft, having the load bearing surface encompassing the pivot shaft again lined with a tesselation of steel plates, forming an oversized bush. Another method, as shown by Figure 9, is by constructing the fixed end 13 having half shafts 59 and integral part of slab structure 11. The half shafts 59 are constructed using concrete 6 with an internal steel skeleton and lined on the outside with a tesselation of steel plates 61 forming a smooth and circular corss sectioned load bearing surface. The half shafts 59, subsequently are surrounded by oversized bushes 62 with tesselation of steel plates 63 as load bearing surface, so as the said shafts are located within walls 6 and 6A. Allowance is made for pipes carrying provisions for vital functioning of slab structure 11, such as fluids for pressure zones 30 and pressure regions 35 and 35A, via the half shaft 59 into said structure 11, in the form of a hollow 64 running along axis 12.

Lower-controur surface 23 is constructed with "beam" construction 65, as shown on Figure 7, in order to reduce the mass of slab structure 11, without sacrificing rigidity. Figure 10, shows a further arrangement for locating fixed end 13. In situation where the length of slab structure 11 exceed a certain limit, it could become advantageous to locate axis 12 below bottom surface contour 4 and sections of bottom surface contour 7.

For maximum flow through most of training walls 3 and 3A, and walls 6 and 6A should be stremlined and covered with concrete sheet pilings 66.

INDUSTRIAL APPLICABILITY This invention would normally be fabricated of reinforced concrete in a position to receive oncoming wave motion. The resultant stored water is used, to energise turbo-electric generators.

Claims

1. An energy conversion system for receiving transported energies in a body of water comprising: a slab structure located in a channel housing said slab structure having side walls that abut the side walls of the channel housing, a front end open to the body of water and a rear end facing in the direction of a water receiving reservoir, said front end of the slab structure being hingedly mounted towards the water end of the channel housing and the rear end of the slab structure being adapted to be raised or lowered between the channel side walls depending on the level of the energies in the oncoming water to form a sloping surface up which the oncoming water runs to spill into the reservoir said rear end of the slab structure also forming at least part of the adjustable height of a wall of the reservoir if required.

2. A system as claimed in claim 1 including means for intercepting incident energies transported by a body of water and directing them towards the channel housing.

3. A system as claimed in claim 2 wherein the means for intercepting comprises a dihedral entrance with side walls converging towards the channel housing.

4. A system as claimed in any preceding claim in which the rear end of the slab structure has a broadened face to act as a variable confining wall of the reservoir.

5. A system as claimed in any preceding claim in which sealing means are provided between the slab structure and the channel housing.

6. A system as claimed in claim 5 wherein the sealing means form a pressure chamber between the slab structure and the channel housing, which holds fluid to support the slab structure.

7. A system as claimed in claim 6 wherein the volume of fluid in the pressure chamber can be increased or decreased to raise or lower the height of the rear end of the slab structure.

8. A system as claimed in claim 7 wherein the seals maintain contact with the channel housing at all positions