Wave powered prime mover

Abstract: The prime-mover comprises a central inertial barge 1, a first outer wave-engaging pontoon 2 pivotally movable relative to the central barge 1 about the pivotal axis defined by the arrow A, and a second outer wave-engaging pontoon 3 pivotally movable relative to the central barge 1 about the axis defined by the arrow B. Two series of pumps 4 are mounted on the central barge 1 and driven by the pivotal movement of the outer wave-engaging pontoons 2,3 respectively. A damping mechanism comprising two shafts 6a,6b extend downwardly from the bage 1. The shafts 6a,6b are provided with damping plates 7a,7b at the bottom ends thereof. The damping plates 7a,7b may be moved relative to the shafts 6a,6b by being screwed up or down the shafts as required.

Description: The present invention relates to wave powered prime movers. It has been well known for many years to harness wave energy by means of apparatus comprising two or more rafts or floats connected together so as to be pivotally movable relative to one another. Wave action causes the relative pivotal movement, and the relative movement is converted into useful energy. Published U.K. Patent Application No. 2113311A, in the name of the inventor of the present invention, discloses a particular arrangement of rafts or floats, namely two rafts connected to one another for relative pivotal movement about a common pivotal shaft, and a damping mechanism for damping the movement of the pivotal shaft so as to maintain the pivotal shaft substantially fixed relative to the mean level of the water. The relative motion of the rafts drives pumps, which drive seawater to an elevated storage tank from which the water may be released to generate electricity. In prior art wave powered prime movers such as described in U.S. Patent Specification No. 4,098,084 (Cockerell), the pontoons or buoyant members, will in certain long wave conditions, i.e. when wave length is greater than four times the length of an individual pontoon, become wave followers and thus will not move relative to each other to any great extent. GB-A-1,593,983 discloses a floating device for extracting energy from waves in which liquid is allowed to flow into and out of a chamber in the device and energy is extracted from liquid within the chamber, which liquid is arranged to oscillate at a frequency similar to the predominant frequency of the incoming waves. In WO 87/05078 there is disclosed a wave energy extracting device comprising a main body anchored in the water and at least one swinging lever mounted on the main body. At the free end of the swinging lever a floating body is provided which can move vertically through the water as the lever swings. FR-892,537 discloses apparatus for utilising sea swell for energy production comprising in combination a float and submerged air pumps, in which movement of the float in the swell actuates the pumps. In NAVY TECHNICAL DISCLOSURE BULLETIN, Washington, Vol. 7, No. 4, June 1982, p133-138 is described a wave energy converter having eight pontoons circumferentially deployed about a spar buoy. Energy is generated by the relative movement of each pontoon relative to the spar buoy. An object of the invention is to alleviate the above disadvantage. The present invention provides a wave powered prime mover comprising an inertial body having damping means located beneath the body, at least two wave movable pontoons, each pontoon being pivotally connected to the inertial body and at least two high pressure water pumps mounted on the inertial body, each pontoon being pivotally connected to a unique pump, characterised in that the damping means may be raised and lowered relative to the inertial body to enable the damping means to be tuned to the site conditions and in that the longitudinal axes of the two pontoons are mutually parallel, whereby in use, following the tuning of the damping means to the site conditions, the inertial body remains substantially stationary over a wide range of wave lengths, whilst each pontoon is moved through its longitudinal axis by passing waves or swell relative to the substantially stationary inertial body, so that water is pumped at relatively high pressure from the prime mover by the pontoon's unique pump. Advantageously, a water delivery pipe is provided extending between the inertial body and the shore. Preferably, the water delivery pipe extends away from the inertial body to a mooring buoy, downwards from the mooring buoy to the sea-bed and along the sea bed to the shore. Conveniently, the damping means includes at least one damping plate which is movable relative to the inertial body, whereby the damping plate may be tuned to the site conditions. Advantageously, the damping plate is mounted on a shaft and is screw threadedly movable relative to the inertial body. Preferably, each pontoon is provided with adjustable ballast to control the inertial properties of the pontoon whereby the prime mover may be tuned to the wave spectra at the site. Conveniently, the water pumped by the prime mover is delivered to an electricity generating turbine or alternatively to a reverse osmosis desalination unit for converting seawater into desalinated water. Advantageously, the lengths of the inertial body and the pontoons are chosen as a function of the characteristic local wave length to optimise power output. Preferably, the damping means may be raised relative to the inertial body to enable the prime mover to be towed. The invention further provides a wave powered prime mover in combination with other such wave powered prime movers in which the inertial bodies of the wave powered prime movers are linked together. The invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one embodiment of wave powered prime mover according to the invention. In the drawings: Figure 1 is a side elevation of the wave powered prime mover; Figure 2 is a plan view thereof; Figure 3 is a sectional end view thereof taken on line III-III of Figures 1 and 2; and Figure 4 is a side elevation showing the prime-mover of Figures 1, 2 and 3 in use, moored near the shore and pumping seawater ashore. Referring initially to Figures 1, 2 and 3, the prime- mover comprises a central inertial barge 1, a first outer wave-engaging pontoon 2 pivotally movable relative to the central barge 1 about the pivotal axis defined by the arrow A, a second outer wave-engaging pontoon 3 pivotally movable relative to the central barge 1 about the axis defined by the arrow B, two series of pumps 4 mounted on the central barge 1 and driven by the pivotal movement of the outer wave-engaging pontoons 2,3 respectively, and a damping mechanism comprising two shafts 6a,6b extending downwardly and provided with damping plates 7a,7b at the bottom ends thereof. The damping plates 7a,7b and shafts 6a,6b move up or down relative to the barge 1 as required, by hydraulic jacks (not shown). Referring to Figure 1, it is seen that the damping plates 7 are located beneath the barge 1 at a depth many times greater than that of the barge to provide a moment arm that produces a torque sufficient to resist movement of the barge due to random wave motion. Referring now to Figure 4, the mooring arrangement will now be described. The wave powered prime mover is primarily, though not exclusively, intended to harness the energy of the ocean swell, that is the onshore swell coming across the ocean as a result of storms or disturbances at distant locations, and not the power of local wind-generated waves or waves caused by the tide, and in particular is not intended to harness the power of breaking or crested waves. The prime mover is therefore most advantageously moored in relatively sheltered waters behind an island or headland. Because the swell is towards the shore, the prime mover is secured by a mooring buoy 8 located to seaward. The prime mover is prevented from swinging in the wind by secondary mooring lines 9 towards the shore. Further mooring lines (not shown) may also be connected to the damping plates 7a,7b. The wavelength of the ocean swell varies from region to region, and the lengths of the barge 1 and pontoons 2 and 3 are chosen as a function of the characteristic local wavelength to optimize output. A flexible water pipe 10 leads from the prime mover unit to the mooring buoy 8, from there down to the seabed and back to the shore. The pipe 10 is flexible to accommodate the rise and fall of the prime mover and of the mooring buoy 8 as a result of the ebb and flow of the tide. The prime mover pumps seawater to the shore. A relatively high pressure delivery is achieved. The seawater at high pressure is delivered to a reverse osmosis desalination plant which is not shown in the drawings, and desalinated water is produced there. Alternatively, the high pressure water is delivered to an electricity generating turbine.

Claims: A wave powered prime mover comprising an inertial body (1) having damping means (6,7) located beneath the body, at least two wave movable pontoons (2,3), each pontoon (2,3) being pivotally connected to the inertial body (1) and at least two high pressure water pumps (4) mounted on the inertial body (1), each pontoon (2,3) being pivotally connected to a unique pump (4), characterised in that the damping means (6,7) may be raised and lowered relative to the inertial body (1) to enable the damping means (6,7) to be tuned to the site conditions and in that the longitudinal axes of the two pontoons (2,3) are mutually parallel, whereby in use, following the tuning of the damping means (6,7) to the site conditions, the inertial body (1) remains substantially stationary over a wide range of wave lengths, whilst each pontoon (2,3) is moved through its longitudinal axis by passing waves or swell relative to the substantially stationary inertial body (1), so that water is pumped at relatively high pressure from the prime mover by the pontoon's unique pump (4). A wave powered prime mover as claimed in Claim 1, characterised in that a water delivery pipe (10) is provided extending between the inertial body (1) and the shore. A wave powered prime mover as claimed in Claim 2, characterised in that the water delivery pipe (10) extends away from the inertial body (1) to a mooring buoy (8), downwards from the mooring buoy (8) to the sea-bed and along the sea bed to the shore. A wave powered prime mover as claimed in any one of the preceding claims, characterised in that the damping means (6,7) includes at least one damping plate (7) which is movable relative to the inertial body (1), whereby the damping plate (7) may be tuned to the site conditions. A wave powered prime mover as claimed in Claim 4, characterised in that the damping plate (7) is mounted on a shaft (6) and is screw threadedly movable relative to the inertial body (1). A wave powered prime mover as claimed in any one of the preceding claims, characterised in that each pontoon (2,3) is provided with adjustable ballast to control the inertial properties of the pontoon (2,3) whereby the prime mover may be tuned to the wave spectra at the site. A wave powered prime mover as claimed in any one of the preceding claims, characterised in that the water pumped by the prime mover is delivered to an electricity generating turbine or alternatively to a reverse osmosis desalination unit for converting seawater into desalinated water. A wave powered prime mover as claimed in any one of the preceding claims, in combination with other such wave powered prime movers in which the inertial bodies (1) of the wave powered prime movers are linked together. A wave powered prime mover as claimed in any one of the preceding claims, in which the lengths of the inertial body (1) and the pontoons (2,3) are chosen as a function of the characteristic local wave length to optimise power output. A wave powered prime mover as claimed in any one of the preceding claims, in which the damping means (6,7) may be raised relative to the inertial body (1) to enable the prime mover to be towed.

Inventors: MCCABE RICHARD PETER, MCCABE, RICHARD PETER
Applicants: HYDAM TECHNOLOGY LTD, HYDAM TECHNOLOGY LIMITED
Application year: 1989
Main classification: F03B13
IPC codes: B01D61, F03B13