GB2467907A

GB2467907A - Wave energy converter with flexible membrane supporting solar energy converters

Info

Publication number: GB2467907A
Application number: GB0901780A
Authority: GB
Inventors: Dominic Michaelis
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-02-04
Filing date: 2009-02-04
Publication date: 2010-08-25
Anticipated expiration: 2029-02-04
Also published as: GB0901780D0; GB2467907B

Abstract

A wave energy converter uses a flexible membrane 11 at the ocean surface which is connected to the seabed and/or to a submerged membrane 15 so that wave movement generates energy e.g. by powering a hose pump or piston pump. The pressurised water may be supplied to an electricity generator or reverse osmosis desalination equipment. The membrane 11 caries solar energy converters which may be photovoltaic, photothermal or photobiological. A part spherical concentrating reflector may be used which is able to maintain its orientation despite fluctuations of the membrane (figure 8).

Description

DESCRIPTION

Apparatus for Deriving Power from Sea Waves and Solar Energy.

This invention relates to apparatus for deriving power from sea waves and solar energy.

It has previously been proposed to harness energy from sea waves in many ways, and in particular, by means of buoys which, as they rise and fall under the wave action, drive hydraulic pistons or other means for generating power and electricity. Disadvantages that exist in these systems include the high cost of manufacturing, transporting and installing the buoys that are inevitably large and relatively fragile and/or heavy. Also, buoys of a size that is effective for the production of electricity constitute a potential hazard to shipping, particularly if they drift from their moorings and they are, therefore, securely anchored to the seabed.

It is proposed to use the large surface area of the apparatus to collect solar energy in a variety of ways, thermal, photovoltaic and photobiological.

It is an object of the present invention to provide an improved apparatus for deriving power from sea waves, in which the aforementioned disadvantages are at least reduced, combined with solar energy converters.

According to the present invention, there is provided an apparatus for deriving power from sea waves comprising a buoyant member in the form of a flexible membrane arranged to lie at the water's surface and energy conversion means provided between said flexible membrane and a submerged station to derive energy from the waves during movement of the membrane relative to the submerged station.

Preferably the membrane is provided with reinforced parts that resist deformation and via which the flexible membrane may be interconnected with said energy conversion means.

The said reinforcement may be reduced or dispensed with when a number of rubber flanges are attached to the underside of the membrane, made of the membrane material, but reinforced with encapsulated metal scrim and cables, spreading the load from the tie means to the membrane The membrane may be of an elongate form and provided with one or more rows of said reinforced parts. Each of said reinforced parts may have a central node point to which energy conversion means is connected, either directly or via tie means.

The tie means may comprise cables extending from the reinforced parts of the membrane to submerged and relatively stationary energy converters such as a hydraulic piston and cylinder device or a hose pump arranged to drive an electricity generator. A hose pump may extend along and comprise the whole or only part of the length of said tie means.

The buoyant member may comprise a plurality of interconnected inflated units that may be individually or collectively flexible.

The apparatus may comprise additionally a second membrane that is arranged to lie submerged at the level of relatively still water, i.e. water which experiences substantially less effect from waves than water at the surface.

Said second membrane may support energy conversion means to which said tie means are connected.

Preferably the submerged second membrane is, in turn, connected to a submerged anchorage such as for example the seabed or means, typically cables, extending from a ship or other structure. The connection between the second membrane and submerged anchorage is preferably not inextensible.

Additional or alternative to a connection between a submerged anchorage and a second membrane, a connection may be provided between the flexible membrane and anchorage.

The anchorage can be at both ends of the submerged membrane, and occasionally along its length, since the upper buoyant membrane can carry the submerged membrane, without the need for anchorage at every membrane connection.

More than one submerged membrane may be provided, and in this case two or more of the membranes may be arranged to lie at different depths. In the case where hose pumps interconnect with said submerged membranes, the pumps connecting to membranes at different depths may be arranged to pump at different internal pressures.

A framework, typically of pressurised braces, may be provided adjacent the second membrane or interconnecting a plurality of second membranes, and the second membrane may be connected to a submerged anchorage by means of said framework.

The apparatus may also consist of an upper membrane and pumps as described, with the lower flexible membrane replaced by weighty hydrodynamically shaped elements that will, by their shape, resist any upward motion transferred by the hose pump or other link element, but, when the wave has passed, fall by gravity and favourable shape, to their initial position ready for the next cycle. These units would need some space between them to be able to operate independently, but would need to be linked together by elastic ties so that they cannot overlap. They can be full shapes, or valved as the lower membrane.

The references made herein to sea waves are not restricted to waves in ocean and tidal waters, but include also waves on inland waters and seas, and rivers, irrespective of whether they are tidal.

The upper flexible membrane presents a large surface to the skies, and can therefore be used to collect solar energy as photovoltaic, thermal, or photobiological energy.

Solar energy can be collected by the upper membrane on which are fitted arrays of photovoltaic flexible film or cells mounted on a flexible membrane, arrays raised above the membrane surface on the flexible pads drained around their edges by drainage channels, the said pads providing horizontal surfaces suitable for low latitude applications, but able to be profiled to provide inclined surfaces facing the midday sun, suitable for use in higher latitudes, the photovoltaic converters cleaned by desalinated spray nozzles, or protected by a transparent membrane, in turn cleaned by spray nozzles, and desalinated water spraying.

The space between a thin membrane to which the photovoltaic films, or other collectors adhere and the principal membrane can be designed to allow pumped water to flow below them, thereby cooling them, specially necessary when they are covered, increasing their efficiency, and providing hot water that can be used in a variety of ways.

Because of the marine environment, wind will carry seawater onto the film or cells, and will, on drying, have a negative effect on its efficiency.

Desalinated water, produced by passing the generated pressurised water through a reverse osmosis filter, these filters either mounted at the top of the hose pump or other seawater pressuring device, or centrally located near the power producing apparatus, the said desalinated water under pressure is led to uprising pipes fitted with spray nozzles, that regularly wash the film surface or its transparent cover. All other solar applications are regularly washed with desalinated water.

In higher latitudes North or South, it may be necessary to incline the photovoltaic collectors, which can be done by taking the photovoltaic film or other flexible solar energy collector, such as a thermal energy collector, over a series of inflated tubes running along an East West axis, providing a corrugated section, the pitch dictated by the height of the tubes and the distance between them. The tubes can be mounted at the correct angle when the position of the wave energy converter is established, sometimes running diagonally or at any other dictated angle, on the surface of the upper membrane.

Solar energy can be collected more efficiently by concentrating solar energy collectors, such as part spherical mirror surfaces that concentrate all intercepted energy onto a linear focus which is situated along the outer half of the sphere radius opposite to the sun, in such a way that if a solar collector, thermal, chemical or photovoltaic is placed along that outer line, it will receive highly concentrated radiation which can be used to heat a fluid, to create a chemical reaction or to create electricity by photovoltaic collectors which will act also as thermal collectors, so that they will provide electricity and heat that can be removed to their benefit, and can be used, for instance, to power a thermal engine.

The construction advantages of using such systems include their geometric simplicity, a sphere being able to rotate within another sphere, or spherical supporting arms, with suitable rolling, sliding or fluid motion enablers, to follow wave motion, if at sea.

The only other moving part is the collector arm which can balance around the centre of the sphere, in a gimbal joint, the inner part of the arm having the solar collector at its outer half, the outer part having the counterbalancing weight provided by a heat engine, electric converter, or other system device, or simply a counterweight, these placed in such a way that their loads are transmitted to the centre of the sphere.

In land applications, the same part spherical mirror movement can be used to incline the mirror to be able to track the sun with the absorber arm, or, by partial rotation only, to compensate partly with radiation losses as the sun rises and sets.

The mirror can be covered with a transparent cover to reduce the necessity of cleaning it, the cover being washed as necessary, but being convex as opposed to concave, it is less likely to accumulate dust, sand or rain, this partly making up its small transmission losses.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: -Figure 1 is a fragmentary plan view showing apparatus according to the present invention in situ for deriving power from sea waves.

Figure 2 is an extended section, generally along the line II of Figure 1.

Figure 3 is a fragmentary plan view, part from above and part from below, showing another apparatus in accordance with the present invention for deriving power from sea waves. And Figure 4 is a section on the line A-A of Figure 3.

Figure 5 shows plans and sections of photovoltaic films or flexibly mounted solar cells used to make use of the large surfaces presented by the apparatus and plans and sections of arrays of concentrating high temperature high efficiency photovoltaic solar collectors adapted to the apparatus top membrane surface.

Figure 6 shows plans and sections of photovoftaic collectors taken over tubes to give them inclination, as well as plans and sections of compartmented surface water containers, used for heating water, for photobiological vegetal growth or for fish farming.

Figure 7 shows a detailed section through the concentrating collector.

Referring to Figures 1 and 2, the apparatus comprises a buoyant member in the form of a flexible membrane 10 carrying a series of hexagonal sheets 11. The membrane 10 and the sheets 11 are formed of a plastics material or a synthetic rubber such as neoprene and are secured together by, for example, sewing or welding. Each hexagonal sheet 11 is reinforced by a pad-like assembly of four circular discs 12 (see Figure 2) formed of, for example, glass reinforced plastics or metal, and a node point 13 exists at the centre of each reinforced sheet.

Below the membrane are shown reinforcing flanges, 45, spreading the load from tie members.

The membrane 10 is also provided with an air inflated tubular edge float 14 that extends continuously around the periphery of the membrane 10.

The same construction methods can use sheets of any suitable form to achieve the same means.

The membrane 11 floats on the seawater surface, which is indicated generally by reference numeral 21.

Below the membrane 10, which is either inherently buoyant or formed with foam fill or air spaces to produce buoyancy, is a submerged second membrane 15 of similar form and dimensions but not buoyant. The membrane 15 carries power generators 16 such as hydraulic piston and cylinder devices, and individual ties 17 in the form of inextensible cables extend from the node points 13 to these generators. Further ties 19, which may be elastic, extend down to the seabed where they are anchored at points 20, The size of the membranes 10 and 15 and the depth of membrane 15 is selected dependent on factors such as sea conditions and power requirements, but typical dimensions are a breadth of about 30 metres and a length of about 1 to 5 kilometres. However, for a lighting or signalling buoy, only one "module" would be needed, typically 5 metres by 5 metres on plan.

In use of the apparatus, wave movements cause the upper membrane 10 to undulate and the distributed force of rising water is carried through sheets 11 and the reinforcing discs 12 to the node points 13 which also rise and fall.

As indicated in Figure 2, the membrane 10 and sheets 11 are flexible and the reinforcing discs are also flexible, albeit to a lesser degree, to allow the membrane to follow the contour of the waves and facilitate the passage of the waves below the unrestrained edges of the membrane. It is also found that the continuous edge float 14 resists the passage of surface water and acts to increase the buoyancy of the membrane 10, The lower membrane 15 is submerged at a depth, which is preferably greater than one sixth of the wavelength that is generally expected in the area where the apparatus is sited, and at this depth there should be relatively still water. Thus, the node points 13 will move up and down in relation to and thereby drive the power generators 16 by means of the ties 17 which are drawn back downwards by weights (not shown) or other suitable means. It is preferred that the submerged membrane 15 is more rigid than the upper membrane 10, to minimise deformation by any water movement which does occur at that depth, and it is to be noted that the presence of the lower membrane 15 may reduce the required number of ties 19 to the sea bed. A further advantage of providing a submerged second membrane is that, if sea waves of a size greater than expected occur, the submerged membrane will tend also to flex and so accommodate, at least in part, any abnormally large movements of the upper membrane 10.

The hydraulic power which is generated by the devices 16 is either transferred through pipes along the sea bed or along one of the lower membranes to a central electricity generating station, or could be employed to induce a rotational movement to generate electricity for example at each node point 13.

In a modified form of the afore described apparatus, the upper membrane 10 is apertured at the node points and held firmly by means of the substantially inextensible upper cables 17. With this arrangement seawater will gush through the node openings as the sea rises and the gushing water can be employed, for example, to power turbines. In this embodiment, smaller or flap-controlled apertures provided with valve means may be provided to allow the return of water as the sea falls.

In a further modified form, means such as propellors are attached by substantially inextensible ties to the node points 13 at approximately the level of the submerged membranes shown in Figure 2. In this case, the rise of the node points 13 will draw the propellors upwardly through relatively still water thus rotating the propellors to produce power. In yet a further modified form, hydraulic power is generated by the elongation and contraction of a set of flexible straps interconnected with a flexible, generally tubular envelope so that a greater volume of water is enclosed in their contracted state than in their stretched state.

As an alternative to being anchored to the seabed, the membranes may be tethered to and possibly towed by a ship in which the electrical generator is mounted. This embodiment is particularly suited to deep-sea locations. Its power could help to propel the ship.

In a further modification, cross cables may also be provided to restrain unwanted lateral movement of the node points 13.

In a further embodiment of the invention (illustrated in Figures 3 and 4) apparatus comprises a series of inflated units 30 interconnected with one another along adjacent edges 31. The units are formed from flexible membranes of plastics material or synthetic rubber, and preferably the lower parts 30a which are subject to the greatest strain, are of stouter material than the sides and upper parts 30b. Each hexagonal unit 30 is formed with a central drainage outlet 32 which opens to a non-return valve 33 and also extends downwardly to provide a connection with the central (node) point of the lower membrane 30a.

Around the periphery of the buoyant member is an inflated edge float 34, which is connected to the outer units 30 by lower and upper membranes 34a and 34b.

Extending from the central (node) point of each unit 30 is a hose pump 35 closed at its upper end. The lower end of each hose pump is connected to a submerged station 36 which will hereinafter be described. Hose pumps are already known (see for example the specification of U.K, Patent Application No. 2,002,052) and consist of lengths of flexible and elastic tubing which, when extended, reduce in internal volume and, when they retract, expand in internal volume; thus, as the tubing is stretched and released, water can be pumped out and in of at least one end.

The submerged station 36 comprises a weighted membrane 37 that is anchored to the seabed by ties 38 connected to the membrane through skirts 39, and a structural support, such as a series of pressurised braces 40 which extend between feed pipes 41. The feed pipes 41 connect with the hose pumps 35 through one-way valves 42, and the feed pipes lead to one or more turbines (not shown).

In use of the apparatus, as the buoyant units 30 rise and fall, the hose pumps 35 stretch and retract to pump water through the valves 33 and the feed pipes 41 to power the turbines. Any water, which passes over the edge float 34, will drain off through the outlets 32 and non-return valves 33.

As illustrated, the inflated units 30 are completely sealed but, in a modified form, may be continuously pressurised by, for example, one or more hose pumps (such as 35) arranged to draw air from the atmosphere above the apparatus.

In a further modification, the buoyant member may consist of a pressurised tubular structure, the pressurised tubes being interconnected by

suitable membranes.

In yet a further modification, to provide a relatively small amount of power, the apparatus may comprise a single buoyant unit such as 30 with its individual hose pump 35, the lower end of which may be anchored directly to the sea bed possibly through a suitable tie. In constructions such as this the submerged membrane or station may not be required.

The weighted membrane 37 may consist of two layers, the lower layer being a load-carrying (perforated) scrim and the upper layer being formed with flexible flaps. This arrangement will resist upward movement of the station 36 when the buoyant member (units 30) rises, but the flaps will deflect to allow through-flow of water when the station returns downwards under gravity, so that the output of the hose pumps 35 will be increased.

In a development of the invention, the feed pipes 41 may lead to a reverse osmosis device or to another alternative apparatus that is hydraulically powered.

In a further development, the Units 30 may be formed of transparent upper memhranes 30b and dark-coloured lower membranes 30a. With this arrangement, limited quantities of salt water admitted into the units 30 may evaporate, condense as fresh water on the angled inner surfaces of the upper membranes and collect in annular troughs (not shown) around the drainage outlets 32; thus, a form of water-distillation plant can be incorporated in the apparatus.

Referring to Figure 5, there is shown a hydrodynamically shaped weighty unit, 80, which, because of its inversed pyramid shape, will resist upward motion, but will readily sink back to its original position once the wave has passed. The unit can be fitted with valved openings, 81, provided with elastically opening flaps, 82, above a mesh support, 83, such that the valves close against the mesh as the unit is pulled up, the flaps opening as the unit falls back to its lowest position, the said valved openings making the descent easier and improving the system efficiency. The unit is held at its four corners by cables, 84, linking the unit to a hose pump, 85, or other power take off means.

The units are linked together by strong elastic members, 86, allowing them differential motion, but preventing them from overlapping and causing damage to each other.

In the section, a series of units are shown linked together at different heights. Because high amplitude waves are long, the relative displacement of the units between each other is small, in such a way that the elastic link between them will not be torn and will keep the units together. Smaller waves will create lesser vertical movements and the units will keep together more readily.

Referring to Figure Fig 6, diagram A, there are shown, fixed to the surface of the upper membrane, 10, secondary membranes on a foam filled substrate, forming flexible pads, 40, drained around their edges, 46, to the upper surface of which are fitted arrays of flexible photovoltaic film or cells mounted on a flexible membrane, the said arrays providing horizontal surfaces suitable for low latitude applications, but able to be profiled to provide inclined surfaces facing the midday sun, suitable for use in higher latitudes, the photovoltaic converters cleaned by desalinated spray nozzles on short poles, 42, the desalinated water created by reverse osmosis units located either centrally, or at the top of a close-by power unit, the water delivered to the nozzle poles by an underwater feeder pipes, 44.

Servicing is carried out by unrolling thick rubber mats directly over the film surface or by linear platforms running on supports in the edge draining channels.

A section AA is shown through the photovoltaic film array.

In order to prevent saltwater deteriorating the quality of the photovoltaic film or flexibly mounted cells, an inflated transparent sheet, 43, can be placed over them.

Lighting posts, 46, are placed at regular intervals along the apparatus, with high posts with high intensity flashing lights are located at both ends In order that seawater splashing over the edge booms, or wind blown spray, does not accumulate above the solar film carrying pads, there is provided an edge suction pumping valved system, so that as the sea surface water presses against it, it closes and prevents it from passing, whereas when the boom pulls away from the sea surface, it sucks entrained water away from the surface of the upper membrane, 45. This detail applies generally to the apparatus.

Referring to Figure 6, diagram B, there is shown on plan an array of stationary reflector / tracking absorber (SRTA) part spherical mirror concentrating collectors, 51, taking all intercepted solar radiation onto the half-radius long linear absorber, lined with high temperature photovoltaic cells providing over 40% of solar energy conversion to electricity, over 3 times the normal efficiency of photovoltaic films or cells of 12%. Spherical geometry allows the part spherical concentrating dish to swivel in a spherical container, thus remaining in the same position relating to the sun as the upper membrane, 10. The same array is shown in section BB. Details of the spherical collector are given in Figure 8.

Referring to Figure 6, diagram C, there is shown a series of tubes, running along an East West axis, 60, over which a secondary membrane is draped, creating inclined surfaces, 61, the South facing inclined surfaces being fitted with photovoltaic flexible film sheets, 62, or solar cells mounted on a flexible substrate, this inclination dictated by the latitude at which the apparatus is used. To protect the films or cells from seawater, a stretched or inflated transparent sheet, 63, can be used. With or without the transparent sheet, the solar collector surfaces are periodically sprayed with desalinated water from nozzle bearing poles, 42.

Referring to Fig 7, diagram D, the upper membrane is covered with inflated or otherwise constructed flexible ridges, 71, creating chambers of a reasonable size, typically hexagonal, 72, seawater can be let in to submerge the said upper membrane, which will then be below these water chambers, whose sides will be high enough to prevent water from spilling over from one chamber to the other, these chambers being possibly used for culture of marine biomass, or for fish farming. Lightweight gangways are used to span one or two such chambers to allow them to be serviced. In another embodiment, they can be covered with a transparent membrane, 76, and shallower, used to heat water flowing through a black membrane sandwich structure. Flow, 73, and return, 74, pipes can feed the chambers with water, or with nutrients for biomass culture and fish farming, the flow direction showed by arrows, 75.

Referring to Fig 8, there is shown a section of two stationary reflector / tracking absorber (SRTA) part spherical mirror collectors, 51, mounted on the apparatus upper membrane, 10, that is shown flexing as it would under the effect of waves. A supporting plate, 90, is embedded into or fixed to the surface of the upper membrane, 10, from which rises a column, 91, which gives firm support to a part spherical container, either a full dish, drained at its base, or made up of part spherical separate "fingers", 92, supplied with ball bearings, 93, or other surface treatment, or hydraulic fluid, allowing the solar collector mirror, 94, to slide so that, under gravity, or by the use of a driving mechanism, it remains with its rim in a horizontal position in which, in high sun conditions, the totality of solar radiation falling on the mirror is concentrated onto a linear focus at the outer half of the radius of the sphere, the absorber, 95 where are located high temperature, high efficiency solar cells. The tubular arm holding these, 96, is aligned with the sun by a mechanism that uses a gimbal mounting, 97, to allow it to pivot along two axes, the gimbal being located at the centre of the sphere. The arm passes through the gimbal to support, at the top end, a thermal power generation device, 98, using the high temperature generated at the focus to heat a working fluid that is taken up the arm to the device where it is evaporated to power a turbine or engine electricity generator, the working vapour being then condensed by air cooled fins, 99 or heat exchangers using the distilled water as it is being created by the apparatus as a coolant, or evaporative cooling, the condensate being pumped down to the absorber to be heated again. The mirror can beneficially be protected by a transparent cover, 100, which protects it from rain, sea spray and corrosion.

Referring to Figure 8, there is also shown a single concentrating collector unit in which a mechanism, 101, is used to cause the mirror dish, 94, to turn so as to keep not only the absorber, 95, aligned with the sun, but also the mirror dish itself, so that it can turn and roll upwards from the horizontal to intercept the greatest amount of solar radiation, as the sun has lower angles of incidence. So that the mirror dish, 94, moves with its support, 92, a pair of part circular guide rails, 102, are fixed to the support, whilst the mirror dish, 94, is fitted with guide plates, 103, held between the rails. The arrows, 104, show the two required axes of rotation.

This part spherical concentrating collector as described is suitable for use on solid decks as well as on land.

Although this particular type of concentrating collector is illustrated, many other types can be used, including parabolic solar concentrators or Fresnel concentrators, producing heat, electricity or hydrogen at their focus.

Although specific mention has been made of energy converters that derive energy from the sea waves as a means of providing a source of energy, it is to be understood that the energy converters may be employed alternatively to serve as energy dissipators where it is required only to dampen wave movements and not provide an energy source. In this case, all that is needed is an elastic resisting material between the two membranes, making the device much more economical. When acting as wave attenuators only, their upper membrane surfaces can beneficially be used as solar collectors.

The apparatus can be set up so that all the pressure generated in the hose pumps, piston systems or actuators is used to produce desalinated water by reverse osmosis, becoming a desalination plant, the upper surface of which can still be used for solar energy conversion.

The apparatus according to the present invention is of simple construction, and the membranes may be assembled at least partly on site.

Also, due to the flexible nature of the membranes, the danger to shipping is greatly reduced, although it is still necessary to mark the position of the apparatus with lights, flags and foghorns, as with any sea going vessel. In some instances, it may be recommended to have loudspeakers, responding to selected sound waves, explaining the nature of the obstacle, its dimensions and the best way of passing by it.

Any such apparatus will of course need permission and be registered with the appropriate naval authorities.

Claims

CLAIMS1. Apparatus for deriving power from sea waves comprising a buoyant member in the form of a flexible membrane arranged to lie at the water's surface and energy conversion means provided between said flexible membrane and a submerged station to derive energy from the waves during movement of the membrane relative to the submerged station, its upper surface used to collect solar energy in various embodiments.
2. Apparatus according to claim 1, wherein the flexible membrane is provided with reinforced parts which resist deformation and via which the flexible membrane is interconnected with said energy conversion means.
3. Apparatus according to claim 1 or claim 2 comprising a second membrane arranged to lie at the level of relatively still water and to serve as a submerged station.
4. Apparatus according to claim 3, wherein the second membrane is more rigid than the flexible membrane of the buoyant member.
5. Apparatus according to claim 3 or claim 4, wherein said second membrane supports energy conversion means.
6. Apparatus according to anyone of claims 3 to 5, wherein the second membrane is secured to a submerged anchorage by an extensible means.
7. Apparatus according to anyone of claims 3 to 6 and comprising a plurality of second membranes arranged to lie at different levels.
8. Apparatus according to anyone of claims 3 to 7, wherein the submerged station comprises a structural support.
9. Apparatus according to claim 8, wherein said structural support comprises a series of pressurised braces.
10. Apparatus according to anyone of the preceding claims, wherein energy conversion means is provided between the flexible membrane of the buoyant member and a submerged anchorage.
11. Apparatus according to anyone of the preceding claims, wherein the flexible membrane of the buoyant member comprises a plurality of interconnected inflated units.
12. Apparatus according to claim 11, wherein said units are individually flexible.
13. Apparatus according to claim 11, wherein the inflated units are collectively flexible.
14. Apparatus according to anyone of the preceding claims, wherein the buoyant member comprises a substantially continuous edge float extending around the periphery of the flexible membrane, and provided with an edge valve device aimed at returning any entrapped water to the sea.
15. Apparatus according to anyone of the preceding claims, wherein the flexible membrane is of elongate shape comprising at least one row of reinforced parts which resist deformation.
16; Apparatus according to anyone of the preceding claims, wherein the flexible membrane of the buoyant member is provided with apertures for the flow of water therethrough.
17. Apparatus according to claim 16, wherein energy conversion means is provided to derive energy from water flowing through said apertures.
18. Apparatus according to claim 16 or claim, 7, wherein at least some of said apertures are provided with valve means arranged to permit water to drain from an upper surface of the buoyant member.
19. Apparatus according to anyone of the preceding claims, wherein the energy conversion means comprises a flexible reinforced tubular member the internal volume of which reduces on elongation of the member.
20, Apparatus according to anyone of claims 1 to 18, wherein the energy conversion means* comprises a hydraulic piston and cylinder device, or an actuator.
21. Apparatus for deriving power from sea waves comprising a buoyant member in the form of a flexible membrane arranged to lie at the water's surface. A second membrane arranged to lie at the level of normally still water, substantially inextensible tie means interconnecting said buoyant member and second membrane, and energy conversion means movable substantially in unison with the second membrane to derive energy from the waves in consequence of said waves causing relative movement of the buoyant member and submerged second membrane.

22 Apparatus according to anyone of the preceding claims, in which the lower membrane is replaced by elastically interlinked hydrodynamically profiled weighty units, provided or not with valved openings, such as they resist the upward motion of the waves transmitted by the power take off device, and return by gravity to their initial position as the trough of the wave passes by.

23 Apparatus according to anyone of the preceding claims, in which the power take off system is replaced by an elastic member able to give the same resistance as the power take off unit, to create a more economic device used to absorb energy from the waves, acting s a wave attenuator, used for protection of operations at sea, of floating vessels and structures and for coastal protection and erosion control.Apparatus according to anyone of the preceding claims, to the upper membrane of which are fitted flexible photovoltaic flexible film or cells mounted on a flexible membrane, arrays, raised above the membrane surface on flexible pads drained around their edges, the said arrays providing horizontal surfaces suitable for low latitude applications, but able to be profiled to provide inclined surfaces facing the midday sun, suitable for use in higher latitudes, the photovoltaic converters cleaned by desalinated spray nozzles, or protected by a transparent membrane, in turn cleaned by spray nozzles with desalinated water, produced by reverse osmosis powered by the high pressures generated by the apparatus.26 Apparatus according to anyone of the preceding claims, to the upper membrane of which are fitted an array of tubes, running along an East-West axis, and therefore sometimes running diagonally across the upper membrane, over which a flexible photovoltaic film or flexibly mounted solar cells can be stretched, providing them with an inclined surface better suited to higher latitude applications, the film or cells covered or not with a transparent cover, in either case washed with desalinated water.27 Apparatus according to anyone of the preceding claims, to the upper membrane of which are fitted arrays of convex part-spherical mirror-surfaced concentrating solar collectors, at the linear focus of which are placed high temperature, high efficiency solar cells, able to achieve conversion efficiencies above 40%, the mirrors, optionally fitted with transparent covers, placed in secondary part-spherical dishes or support arms, these moving with the waves, but allowing the mirror to remain in its horizontal position, suitable for low latitudes, the mirror dish able to be inclined to further face the sun, in higher latitudes or to gather lower angle solar radiation, the heat generated at the focus transferred to a suitable working fluid, taken to the top of the gimbal fitted absorber pivoting arm, mechanically aligned with the sun, and there providing thermal energy to a turbine or heat engine electricity generator, the said turbine or heat engine provided with air cooled or distilled water cooled heat exchangers condensing the vaporised working fluid, thereby further increasing the solar collector efficiency.28 A convex part-spherical mirror-surfaced concentrating solar collector, according to claim 27, and arrays of the same, used on land.29 Apparatus, according to any one of the preceding claims, whose upper membrane is covered with inflated or otherwise constructed flexible ridges creating chambers of a reasonable size, typically hexagonal, seawater being let in to submerge the said upper membrane, which will then be below these water chambers, whose sides will be high enough to prevent water from spilling over from one chamber to the other, these chambers being used for culture of marine biomass, or for fish farming. In another embodiment, they can be shallower and covered with a transparent membrane to heat water flowing through a black membrane sandwich structure. Flow and return pipes feed the chambers with water, or with nutrients.Apparatus, according to anyone of the preceding claims, in which all the pressure generated in the hose pumps, piston systems or actuators is used to produce desalinated water, the apparatus becoming a desalination plant, the upper surface of which can still be used for solar energy conversion.31 Apparatus, according to anyone of the preceding claims, which, due to the flexible nature of its membranes, presents reduced danger to shipping, although it is still necessary to mark the position of the apparatus with lights, flags and fog horns, as with any sea going vessel, in some instances, it being recommended to have loudspeakers, responding to selected sound waves, explaining the nature of the obstacle, its dimensions and the best way of passing by it.32. Apparatus for deriving power from sea waves and solar energy, and producing desalinated water, constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.