This invention relates to conversion of wave power into usable energy.

There have been numerous proposals for utilising wave energy. Examples include GB-A-12099/1904; GB-A-3164/1909; GB-A-1014196 and GB-A-1482085.

Broadly, in accordance with this invention, wave power is converted into usable energy by causing a float to extend an air cylinder as it rises over a wave and allowing the weight of the float and of other structure by which it is connected to the cylinder to contract and compress air in the cylinder as the wave passes. Preferably the float is one of a line of such floats which rise and f ll one after another as a wave passes along the line, each float being caused to extend a respective air cylinder as it rises.

According to an aspect of this invention, a twin-hull vessel is provided with a line of floats between its hulls and is long enough to extend over a sufficient number of waves for it to be substantially stable in an average sea, each float being mechanically linked to a movable part of a respective air cylinder which is mounted in a respective one of the hulls so that it is extended by the rising of the respective float as it rides a wave which passes along the vessel, the cylinder being subsequently contracted to compress air therein by the weight of the float of the movable part of the cylinder and of the linkage by which they are connected, each cylinder having an outlet for air

compressed therein and the outlets being connected to drive energy generating means.

Preferably the compressed air is used to drive an air turbine which is drivingly-coupled to an electricity generator. In an alternative embodiment, the compressed air is used to drive one or more impeller rotors (such as a fan) which in turn function as propulsion means for the vessel.

The vessel may be provided with a retractable closure member which is normally-retracted and housed in the bow section of the vessel, but which can be lowered into the gap between the hulls for excessively high sea conditions. The closure member may be constrained to be lowered along a rearwardly sloping path.

The vessel may be provided with transverse bulkheads extending between adjacent floats. The bulkheads may be retractable and arranged to be lowered in excessively high sea conditions to minimise angular motion of the adjacent floats about their transverse axes and thereby to stabilise the vessel. Alternatively the vessel may be provided with locking devices which can be operated from within the twin hulls to secure some or all of the floats in the lowered position during excessively high sea conditions thereby improving the stability of the vessel.

In one embodiment each float is linked to an air cylinder in each hull by a beam which may extend through vertical guide slots formed in the inner wall, of each hull. Each float may carry more than one such beam which links it to a respective pair of air

cylinders, one in each hull. Alternatively each float may be so linked to just one such pair of air cylinders, but means may be provided to enable each such float to be rigidly linked to a juxtaposed such float for fast running sea conditions. In a preferred embodiment short beam assemblies could be substituted for the full length beams described above. These short beam assemblies would be attached above each cylinder and operated independently by floats free to swivel out of the horizontal plane when waves assume an angled or uneven situation as they pass between the twin hulls. Short beam assemblies would also allow extra decks to be fitted at lower levels between the twin hulls, providing extra cargo space and a lower centre of gravity and improved stability.

Stabilizing plates may be attached at intervals between the twin hulls to provide improved stability to the vessel by reducing the pitching and rolling motion, particularly in stormy weather conditions. These plates would be fitted sufficiently below the water-line, near to the keel, so that they would not interfere with the established rolling, circular pattern of wave formation below sea level. Alternatively, underwater horizontal stabilizing cargo space can be provided between the twin hulls along the entire length of the vessel, which would increase the strength of the vessel, improve stability, increase cargo space and lower the centre of gravity of the vessel by a considerable margin. This large flat area underneath the whole centre portion of the vessel would also prevent any loss of energy produced by the vertical motion of the waves from dispersing into the surrounding area of the sea, and would cause any down- ward motion following the rapid lowering of each float

as each wave passes along between the twin hulls to rebound up again to the surface, producing more turbulence and more piston movement, therefore more power.

One form of twin-hulled vessel in which this invention is embodied is described now, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic plan view of the vessel with all decks and superstructure removed;

Figure 2 is a longitudinal section of Figure 1, on the line A-AA in Figure 1, the floats in the rear portion of the vessel being shown as if displaced by a wave;

Figure 3 is a fragmentary portion of Figure 1, drawn to a larger scale and in more detail;

Figure 4 is a transverse section of Figure 1, on the line B-BB in Figure 1, showing a float in full lines in a low position and in dotted outline in a raised postion; and

Figure 5 is a view in perspective, of part of the inner wall of one of the hulls of the vessel shown in Figure 1 and part of a beam mechanism which extends through a slot in that inner wall to link a float to an air cylinder in that hull.

Referring to the drawings, the vessel, which is of twin hulled construction, is sufficiently long, say about 244 metres (800 feet), to extend over many waves and thus be substantially stable in a running sea. It comprises a substantially constant - section main

portion which extends for a major part of the overall length of the vessel and which separates tapered bow and stern portions.

Fixed sloping members 10 at the bow and the stern connect the twin hulls 16 at inner hull plates 25, forming an integral part of the vessel.

Floats 12 are arranged in a line in the main portion between the hulls 16 and below a deck portion (not shown) which joins the hulls 16 above the water line 34. A float push rod 27 at each end of each float 12 has a swivel joint 28 at either end and is connected to a respective short beam and jockey wheel assembly 45.

Sliding members 11 are housed above the fixed members

10 in the bow and stern sections, and can be lowered towards the water-line 34 by means of cables 18 running over pulleys 17 in guides, (not shown), to help protect the floats 12 from excessive violent movement in storm conditions. These sliding members

11 are shown in figures 1 and 2 in the raised position at one end of the vessel and in the lowered position at the other end of the vessel.

Rectangular vertical chambers or tunnels 13 house the short beam and jockey wheel assemblies 45, isolating all the working parts, apart from the floats 12 and float push rods 27, from all decks, cargo and working areas. These chambers 13 also prevent ingress of waves that may enter the chambers through short beam slots 19 formed in the respective inner hull plates 25 from any further access to other parts of the vessel.

The floats 12 are arranged between the twin hulls 16 with Tee section vertical guides 22 attached to inner hull plates 25 to separate floats 12 from each other and to prevent damage to the ends of the floats 12 and to the hull plates 25. These floats 12 are preferably elliptical in cross-section to form less resistance to the waves and wind when the vessel is under way. The ends of these floats 12 are shaped to form a radius centred upon the water-line level at the opposite end of the floats to ensure that the floats 12 do not jamb aggainst the guides 22 or hull plates 25 as they lift and fall with the waves that pass between these plates, or as these floats 12 swing out of the horizontal plane under irregular wave patterns as it is intended that they shall be free so to do. These floats 12 may be subdivided into multi chambers 26 by vertical and horizontal bulkheads 41 to ensure rigidity and stability, also to enable the floats to be used for transportation of liquid cargos of varying types, also sea water ballast, in separate compartments, and filled by combined filler pipes or individual fillers, as required, (not shown). These multi chambers 26 and bulkheads 41 also ensure that liquid cargos remain in a stable situation when the floats 12 are raised out of the horizontal plane by cross winds and/or waves. Such floats may be designed to float with about three quarters of their total volume submerged to achieve maximum displacement and weight for compression purposes; also for maximum cargo or payload. Stops 23 prevent floats from hitting decks in storm conditions. Connection of the floats 12 to the short beam assembly 45 by means of the float push-rods 27 and the swivel joints 28 at either end enables the floats 12 to adjust freely to

any uneven or angular motion of the waves, out of the horizontal plane.

A typical short beam and jockey wheel assembly is shown in more detail in figure 5. It comprises a jockey wheel train of eight wheels 48 which run in the respective tunnel 13, jockey wheel spindles 49 which are journaled in the respective H-section short beam, and ball or roller tracks 43 and ball or roller races 44 for either end of the short beam. Each short beam is connected to a piston rod 14 of a respective air cylinder 24 by clamping collars 46 which are for height setting when the vessel is fully loaded and which are operable by clamping levers 47. The piston rod 14 passes through the short beam, and when in its correct position relative to the correct floating trim of the cargo floats 12, is clamped with the collars 46 above and below a hole in the beam. A float push rod clearance groove 50 is formed in the bottom 32 of each beam slot 19. Each short beam passes through the respective beam slot 19 and the respective eight-wheeled jockey train maintains the correct alignment in relationship to the respective piston rod 14.

An alternative arrangement may be a ball or roller race fitted at each end of the short beam and a vertical track fitted to the inner face of the inboard and outboard bulk-heads of the rectangular vertical chambers 13 to maintain the correct alignment in relationship to the piston rod 14. Another arrangement may be the use of steady bars attached to the vertical bulkheads about which the short beam assemblies slide, (not shown) .

An alternative arrangement would be an automatic fully computerized system to set the trim when the loading of the vessel is completed and ready for sea. (not shown) . Allowance would have to be made for the fact that the trough 35 of a wave, preceeding and following each wave, is several feet lower than the water-line 34 at which the vessel would float in calm water in dock, and the trim height position would have to make allowance for the fact that the piston rods 14 would have to travel several feet further downwards at sea than would be apparent when tied up quietly in dock. This distance would have to be allowed for so that the bottom of each short beam would not contact the bottom of the respective beam slot 32 when the vessel is at rest in dock, but clear by the amount of the trough depth.

Horizontal stabilizing plates 20 are shown situated at intervals along the keel of the vessel. Underwater horizontal stabilizing cargo hulls 51, with forward and aft sections 54 streamlined to reduce resistance when under way, could be substituted in their place. These cargo hulls 51 would be of multi-chamber construction, similar to the chambers 26 in the floats 12 and serving the same purpose. Longitudinal and transverse vertical bulkheads 52 would be used to form these chambers, at the same time forming the framework for their construction. There would be inspection hatches to each chamber, (not shown) , and/or watertight doors 53 at several points along these hulls 51, access to them being possible from the main engine rooms 33 in the lower part of the twin hulls 16. These hulls 51 could be filled completely with liquid fuels, hydrocarbons, crude oil, refined oil products, or highly volatile liquids; or even a

mixture of them. Being isolated from the main twin hulls the risk of fire would be minimal, and being at a considerable depth in the sea at all times during transit would be kept at a safe, cool temperature. These hulls could also be used for ballast, and be discharged by compressed air from the central compressed air manifolds 15. The weight of these cargo hulls and liquids contained within would improve the stability and lower the centre of gravity of the vessel to a considerable extent, acting as a counter¬ balance to the weight of container cargo, or other deck cargo that would be carried on cargo decks 42 or even in the interior of the main twin hulls 16. The very large flat area of these cargo hulls 51 would improve the stability of the vessel both in the longitudinal and the transverse aspects. These multi- chamber cargo bays could be filled by a system of pipes to fill several chambers simultaneously, or by individual means, (not shown).

Figures 1 and 2 show the vessel has main transverse watertight bulkheads 21 which form the main integral framework of the hulls 16. The bulkheads 21 could be provided with watertight doors, (not shown) for access to adjacent cargo holds along the entire length of the vessel. The horizontal bottom edge of the fixed central section of each of these bulkheads 21, which extends between the hulls 16, must, however, terminate clear of the highest point attained by any wave to avoid resistance to such waves when the vessel is under way. This height would coincide with the level of the lowest central cargo deck 42, which must be higher then the highest point reached by any float 12.

The compressor cylinders 24 are situated in the lower parts of the vessel within the interior of the hulls 16 and could have a system to adjust their height in relationship to the height of the floats when fully loaded with cargo, (not shown) . An adjustable water¬ tight gland 31 is situated protruding through the deck adjacent to the bottom 32 of each short beam slot 19 to ensure that any water entering the vertical tunnel or chamber 13 through that short beam slot 19 cannot enter the respective compressor cylinder 24. A breather hole 55 situated below this deck but higher than any point achieved by the piston 40 of the respective cylinder 24 at any time ensures that there is no air resistance to the area above that piston 40. Air enters each cylinder 24 via valve 38 when the respective piston 40 is raised by the action of the respective float 12, to which it is connected as described above. The floats 12 are raised by the action of the waves as they pass along the vessel between the twin hulls 16. Compression is achieved as the weight of the whole assembly of pistons 40, piston rods 14, short beam assemblies 45, floats 12 containing cargo and ballast, all combine when the wave passes further along between the hulls 16, with the force of gravity providing the power. Compressed air is forced out of each cylinder 24 through a non¬ return valve 39 into a compressed air storage tank 15 via a non-return valve 36. From the air storage tank 15, air is supplied via a valve 37 to an air turbine which is in turn drivingly coupled to an electricity generator (not shown) .

In another embodiment, the vessel is provided with one or more propulsion fans which are supported on the superstructure of the vessel. Each -cylinder outlet

valve 39 is connected to a respective pipe (not shown) and the pipes are led in bunches to the fans (not shown), being divided equally among the fans. The bunch of pipes led to each fan have their orifices arranged as a circumferential array of jets directed at the blades of the respective fan substantially parallel to the axis of the fan rotor. Hence the fans are driven by the annular array of jets impinging on their blades and in turn propel the vessel. Each fan may be mounted on an angularly swivelable pylon so that the vessel may be steered by swivelling these pylons.

In operation of the invention, the vessel could be anchored. The floats 12 would rise and fall over waves that pass between the twin hulls 16. Each float 12 would extend the air cylinders 24 to which it is linked by the float push rods 27 and short beam assemblies 45 as it rises over a wave. After the peak of the wave has passed, the weight of the float 12, short beam assembly 45, float push rods 27, jockey wheels 48, spindles 49, pistons 14, clamping collars 46, levers 47, cargo and ballast in floats 12, would cause contraction of the cylinders 24 so that air within these cylinders 24 is compressed, being vented through non return valves 39, and into the central compressed air manifolds 15 via inlet valves 36. From air manifolds 15 compressed air would exit through valves 37 to air turbines, (not shown), coupled to an electricity generator, (not shown). Alternatively, compressed air could be fed direct to fans to provide propulsion, or assisted part propulsion, to the vessel. The sloping members 10 help to concentrate any wind towards the surface of the sea, thus possibly increasing disturbance of the sea, such extra energy

being transmitted to the floats and hence to the cylinders 24.

In a modification the cylinders 24 could be arranged in pairs 29 in line fore and aft, or in pairs 30 across ships, to provide increased power, or to enable smaller diameter pistons to be used. With cylinders in line fore and aft, a more suitable arrangement would be to have the tunnel housings as a continuous vertical bulkhead 13 running the complete length of the floats area fore and aft, and connected to each of the main bulkheads 21. A continuous longitudinal bulkhead 13, connected to each of the main bulkheads 21 may be a preferred arrangement to enable any combination or number of cylinders to be accommodated in the lower part of the hulls 16, and to enable the modified arrangements for the short beams 45 and jockey wheel assemblies 45 to be accommodated in the tunnel housings 13.

In another modification provision could be made to link juxtaposed pairs of floats to one another so that they move together as one for faster running seas whereas they are allowed to move independantly under normal conditions.