WO2009076713A1

WO2009076713A1 - Reciprocating pump actuated by wave energy

Info

Publication number: WO2009076713A1
Application number: PCT/AU2008/001854
Authority: WO
Inventors: Alan Robert Burns; Petru Tinc; Matt Keys
Original assignee: Seapower Pacific Pty Ltd
Current assignee: Seapower Pacific Pty Ltd
Priority date: 2007-12-17
Filing date: 2008-12-17
Publication date: 2009-06-25
Anticipated expiration: 2010-06-17
Also published as: CL2008003767A1; TW200940823A

Abstract

A reciprocating pump (15) adapted for actuation by a reciprocating input, typically generated by wave motion. The pump (15) comprises a fluid delivery means such as a piston mechanism (201) adapted for reciprocation in response to reciprocation of the input. A gearing means (251) is provided between the reciprocating input and the piston mechanism (201), the gearing means (251) delivering a stroke length to the reciprocating piston mechanism (201) different from the stroke length of the reciprocating input. Typically, the gearing means (251) delivers a reduction in the stroke length of the reciprocating piston mechanism (201) in relation to the stroke length of the reciprocating input. The gearing means (251) may comprise a pulley mechanism (261) coupling the piston mechanism (201) to the reciprocating input.

Description

RECIPROCATING PUMP ACTUATED BY WAVE ENERGY

Field of the Invention

The invention relates to a reciprocating pump.

The invention has been devised particularly, although not necessarily solely, as a reciprocating pump adapted to be activated by wave energy.

The invention also relates to a wave energy system which utilised such a pump.

Background Art

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

It is known to couple wave motion to a reciprocating pump operable in response to wave motion, one example of which is use of a float to translate wave motion into the reciprocating pump action. Typically, the float is disposed generally vertically above the pump and is coupled thereto by a tether. There is a direct connection between the float and the reciprocating piston of the pump such that the stoke length of the reciprocating piston accords with the extent of vertical displacement of the float in response to wave action. This may can be problematic in certain applications.

Brief Description of the Invention

According to a first aspect of the invention there is provided a reciprocating pump adapted for actuation by a reciprocating input, the pump comprising a fluid delivery means adapted for reciprocation in response to reciprocation of the input, and gearing means between the reciprocating input and the fluid delivery means, the gearing means delivering a stroke length to the fluid delivery means different from the stroke length of the reciprocating input. Preferably, the gearing means delivers a reduction in the stroke length of the fluid delivery means in relation to the stroke length of the reciprocating input.

Preferably, the gearing means comprises a pulley mechanism coupling the fluid delivery means to the reciprocating input.

Preferably, the pulley means comprises an axle assembly rotatable about an axis transverse to the direction of the strokes of the input and the fluid delivery means, at least one first flexible elongate element connected at one end to the axle assembly and adapted to wind around the axle assembly at a first radial distance from the axis, the first elongate flexible element being coupled to the reciprocating input, and at least one second flexible elongate element connected to the axle and adapted to wind around the axle assembly at a second radial distance from the axis, the second elongate flexible element being coupled to the fluid delivery means, the second radial distance being different from the first radial distance to provide the gearing.

Preferably, the first flexible elongate element and the at least one second flexible elongate element wind about the axle assembly in different directions.

With this arrangement, the first elongate element reciprocates in response to the reciprocating input, causing the first section of the axle assembly to rotate which in turn causes the at least one second section to also rotate, thereby causing the at least one second flexible elongate element to reciprocate and thus imparting reciprocating motion to the fluid delivery means.

Preferably, the axle assembly comprises a first section about which the first elongate element is adapted to wind, and at least one second section about which the at least one second elongate element is adapted to wind.

Preferably there are two second elongate flexible elements and thus two second sections about which the two elongate flexible elements wind.

Preferably, the two second sections are disposed one to each side of the first section. The axle assembly may comprise a shaft, the first section comprises a wheel on the shaft and each second section comprises a circumferential groove in the shaft.

Preferably, the reciprocating fluid delivery means comprises a reciprocating piston mechanism within the pump.

This provides advantages in that: (a) the stroke length reduction leads to reduction in the overall length of the pump; (b) there is a velocity reduction in the piston mechanism relative to the input which may facilitate better high pressure sealing; and (c) the piston diameter can be increased, leading to better piston dimensional stability.

According to a second aspect of the invention there is provided a reciprocating pump adapted for actuation by wave energy delivering a reciprocating input, the pump comprising a fluid delivery means adapted for reciprocation in response to reciprocation of the input, and gearing means between the reciprocating input and the fluid delivery means, the gearing means delivering a stroke length to the fluid delivery means different from the stroke length the reciprocating input.

According to a third aspect of the invention there is provided a wave energy system comprising a buoyant actuator responsive to wave motion, a reciprocating pump comprising an input adapted to reciprocate in response to reciprocating motion of the buoyant actuator under the influence of wave motion, a fluid delivery means adapted for reciprocation in response to reciprocation of the input, and gearing means between the reciprocating input and the fluid delivery means, the gearing means delivering a stroke length to the fluid delivery means different from the stroke length the reciprocating input.

Brief Description of the Drawings

The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which: Figure 1 is a schematic elevational view of apparatus incorporating a plurality of reciprocating pumps according to the embodiment, the apparatus being shown installed in position under water;

Figure 2 is a schematic perspective view of the apparatus;

Figure 3 is a schematic side elevational view of the apparatus, with parts of a buoyant actuator forming part of the apparatus removed to reveal further details;

Figure 4 is a plan view of the arrangement shown in Figure 3;

Figure 5 is a plan view of a lower portion of the apparatus, comprising a base structure and reciprocating pumps according to the embodiment mounted thereon;

Figure 6 is a fragmentary sectional elevational view of part of the lower portion shown in Figure 5;

Figure 7 is an elevational view of the buoyant actuator;

Figure 8 is a schematic perspective view of an internal support structure incorporated within the buoyant actuator;

Figure 9 is a perspective view of part of the internal support structure shown in Figure 8;

Figure 10 is a partly sectioned elevation of the part of the structure shown in Figure 8;

Figure 11 is a partiy sectioned perspective view of the part shown in Figure 8;

Figure 12 is a side view of the partly sectioned part shown in Figure 11 ;

Figure 13 is a fragmentary view of the buoyant actuator, showing in particular a mechanism for reducing the buoyancy thereof in certain conditions; Figure 14 is a cross-sectional view of the arrangement shown in Figure 13;

Figure 15 is a sectional perspective view of one of the reciprocating pumps according to the embodiment;

Figure 16 is a sectional elevational view of the reciprocating pump;

Figure 17 is an elevational view of the pump in part section to reveal some internal details;

Figure 18 is a perspective view of a shaft forming part of the reciprocating pump;

Figure 19 is a side elevational view of the shaft;

Figure 20 is a perspective view of a wheel adapted to be mounted on the shaft shown in Figure 17;

Figure 21 is a side elevational view of the wheel;

Figure 22 is a cross-sectional view of the wheel;

Figure 23 is a fragmentary perspective view of a section of the pump;

Figure 24 is a fragmentary perspective view of a lower end section of the pump;

Figure 25 is a fragmentary perspective view of an upper end section of the pump;

Figure 26 is a schematic perspective view illustrating a number of the apparatus according to the embodiment positioned in an array;

Figure 27 is a view somewhat similar to Figure 26- but is showing the apparatus positioned in another array; and

Figure 28 is also a view similar to Figure 26 but showing the apparatus in yet another array. Best Mode(s) for Carrying Out the Invention

Referring to the drawings, the embodiment is directed to a reciprocating pump 15 used in apparatus 11 for harnessing wave energy in a body of water and for converting the harnessed energy to high pressure fluid, typically above 0.7 MPa and preferably above 5.5 MPa. The high pressure fluid can be used for any appropriate purpose. In the arrangement shown, the high pressure fluid comprises water used for power generation and/or desalination.

The apparatus 11 is installed for operation in a body of seawater 12 having a water surface 13 and a seabed 14.

The apparatus 11 in fact comprises a plurality of pumps 15 according to the embodiment anchored within the body of water 12 and adapted to be activated by wave energy. The pumps 15 are attached to a base 17 anchored to the seabed

14. Each pump 15 is operably connected to a buoyant actuator 19 buoyantly suspended within the body of seawater 12 above the pumps but below the water surface 13 at a depth such that it is typically a few metres below the neutral water line. With this arrangement, each pump 15 is activated by movement of the buoyant actuator 19 in response to wave motion.

Each pump 15 is operatively connected to the buoyant actuator 19 by a coupling 21 comprising a tether 23. The pumps 15 provide high pressure fluid (water in this embodiment) to a closed loop system 25 in which energy in the form of the high pressure fluid is exploited.

The pumps 15 each comprises a reciprocating pump having a low pressure inlet 27 and a high pressure outlet 29.

In the illustrated arrangement, the base 17 comprises a generally triangular structure 31 having three sides 33 interconnected at corners 35 which are truncated to define edges 37, as best seen in Figure 2. There are three pumps

15, with one of the three pumps connected to each corner 35 of the triangular base. Each pump 15 is also connected to the buoyant actuator 19 by way of the tether 23. The tethers 23 are made of any appropriate material, such as synthetic rope.

The buoyant actuator 19 is positioned above, and is centrally located with respect to, the three pumps 15, as can be seen in Figure 4.

The tethers 23 are connected to the buoyant actuator 19 at a point where, if the tethers were to extend inwardly of the buoyant actuator, they would meet at the centre of the buoyant actuator. In this way, the pumps 15, tethers 23 and the base 17 define a triangular based pyramid with the buoyant actuator 19 located at the apex of that pyramid.

With this arrangement, the pumps 15 as well as the tethers 23 are at an angle to the horizontal. By providing the pumps 15 at an angle to the horizontal, the motion of the buoyant actuator 19 is able to provide a reciprocating stroke length in the pumps 15 that generates sufficient high pressure water while being located within regions of limited seawater depth for example, depths of 7 metres to 10 metres. Further, with such a configuration the pumps 15 are able to exploit horizontal wave motions.

Typically, the tethers 23 subtend an angle of approximately 40 degrees to the horizontal, although each can be at a suitable angle, typically between about 35 degrees and 55 degrees.

The base 17 comprises an equilateral triangle having side lengths of approximately 7 metres, corresponding approximately to the depth of the water in which the apparatus is submerged. The edge 37 of each corner 35 of the base 17 is approximately 2 metres.

The base 17 is made of reinforced concrete and includes an internal system of pipe work 41 that couples the pumps 15 to the closed loop systems 25, as shown in Figure 3 and as will be described in more detail later. In this embodiment, the pipe work 41 comprises mild steel pipe.

At each corner 37 of the triangular base structure 31 there is provided first and second ports 51 , 52, as best seen in Figure 5. Each of the first ports 51 communicates with a low pressure inlet 55 at the outside of the base 17 by way of low pressure piping 53 incorporated within the base 17 as part of the pipe work 41. Each of the second ports 52 communicates with a high pressure outlet 57 by way of high pressure piping 59 incorporated within the base 17 as part of the pipe work 41. A flexible inlet hose 61 connects each first port 51 to the inlet 27 of the respective pump 15, and a flexible outlet hose 63 connects each second port 52 to the outlet 29 of the respective pump 15. In this way, low pressure water is fed^vfrom a low pressure manifold 64 that carries low pressure water from elsewhere, into the piping 53 via the inlet 55. From the inlet 55 the water flows to the first ports 51 via the low pressure piping 53, through the flexible hoses 61 to the inlets 27 of the pumps 15. Water delivered under high pressure from the outlets 29 of the pumps 15 flows through the flexible hoses 63 to the second ports 52 and into the high pressure piping 59 from where it is delivered to the high pressure outlet 57. From the outlet 57 the high pressure water flows into the high pressure manifold 66, and from where the high pressure water is taken to its destination.

The base 17 has an external raised portion 71 around its edge which defines a horizontal surface 72, an inclined surface 73 and an interior recess 75. The inclined surface 73 serves to provide a section to which the respective pump 15 can be secured by a connection 77. The inclined surface 73 subtends an angle of 45 degrees to the horizontal.

The base 17 can also be provided with a lifting eye 78 at each corner which enables the base to be installed onto, and lifted from, the seabed as required. The lifting eye 78 is provided on the horizontal surface 72 of the raised portion 71.

The base 17 is configured to function as a suction anchor for attachment to the seabed 14. In this regard, the base 17 includes a depending flange 81 (as best seen in Figure 6) around its edge to provide anchorage for the base using suction when placed on the seabed 14. The base 17 incorporates a suction hole (not shown) to provide a means of expelling trapped fluid as the base is deployed on the seabed. The suction hole is then sealed to maintain the suction anchorage. The buoyant actuator 19 functions as a submerged float to translate wave action into a reciprocating action at the pumps 15. The buoyant actuator 19 comprises a body 20 which is generally spherical in shape but comprises a plurality of facets 101 that are tessellated. The facets 101 define an outer shell 102 which presents an outer surface. The interior of the buoyant actuator 19 is substantially hollow but comprises an internal support structure 103 which is buoyant, as will be explained later. Some of the facets 101 have been omitted in Figures 1 , 3 and 4 to reveal part of the internal support structure 103.

In the arrangement shown, the outer skin 102 of the buoyant actuator 19 has thirty-six facets 101 , comprising twelve pentagonal facets 105 and twenty-four hexagonal facets 107. The facets 101 are tessellated to create the generally spherical shape (somewhat similar to that of a soccer ball), as shown in Figure 7.

The support structure 103 comprises a plurality of struts 111 that extend radially outwardly from a central core 113. In the arrangement shown there are twelve struts 111 , one corresponding to each pentagonal facet 105, as shown in Figure 8 which is a perspective view of the struts 111 and pentagonal facets 105, but with the hexagonal facets removed for clarity.

Each strut 111 is connected at the inner end to the centrally-located core 113 such that the struts extend radially outward from the core and are substantially radially equidistantly spaced. The core 113 comprises a central inner core of a rigid material such as steel, an intermediate foam layer surrounding the inner core and an outer layer of high density polyethylene (HDPE).

Each distal end of the strut 111 is splayed to present a flat outer face 115 which defines one of the pentagonal-shaped facets 105. The pentagonal-shaped facets 105 are thus supported by the struts 111 , and the hexagonal-shaped facets 107 are located in between and fixed to adjacent facets as illustrated in Figure 7. Figures 10, 11 and 12 further illustrate the core 113 of one of the struts 111. For clarity, only half of each facet 101 and the strut 111 is shown.

Each strut 111 is substantially circular in cross-section and comprises three concentric sections; being an inner steel core 121 , surrounded by a foam layer 122 and an outer layer 123 of high density polyethylene (HDPE). Figure 10 is a longitudinal cross-section of the strut illustrating the different layers of the strut.

The outer layer 123 of HDPE extends along the whole of the strut 111 and also provides the outer face 115 which defines the pentagonal facet 105. The facet 105 is thus made from HDPE.

The facets 101 have edges configured as lips 124. The facets 101 are joined together at adjacent edges by connections 125 extending between the lips 124. In the arrangement shown, the connections 125 comprise bolts extending through holes 129 in the adjacent edges of the facets 101 to secure the facets together.

The buoyancy is provided by the foam in each of the struts 111 and the core 113. The foam is used to provide additional uplift during the pumping stroke. A wave exerts almost as much upwards force as it does downwards force on the buoyant actuator 19. As each pump 15 only acts in one direction the buoyancy inside the buoyant actuator 19 acts as a potential energy storage during the down stroke so that the buoyancy and uplift force both work on the pump during the upwards stroke direction.

The foam may be a closed cell poured urethane foam, although other suitable materials could be used.

Due to the substantially hollow nature of the buoyant actuator 19, it is lightweight compared to prior art floats.

In the arrangement shown, each strut 111 weights of the order of less than 35kg, with the whole float structure weighing the order of 400kg. Further, the diameter of the buoyant actuator 19 is of the order of 4m to 7m, depending upon the depth of water in which it is to be used.

As mentioned earlier the buoyant actuator is connected to each pump15 by tether 23. A coupling in the form of a pad eye 131 is used to connect the tether 23 to the buoyant actuator 19. The pad eye 131 is attached to the inner steel core 121 as can be seen in Figure 10 and extends from the facet 105. The pad eye 131 includes an HDPE coating 133 for water resistance. The buoyant actuator 19 incorporates a storm release feature to maintain the integrity of the buoyant actuator when exposed to an aggressive sea state in adverse weather conditions.

For this purpose, means 141 are provided for opening the interior of the buoyant actuator 19 to permit water to flow through the buoyant actuator in response to exposure of the buoyant actuator to such adverse weather conditions. This is achieved by establishing openings 143 in the shell 102 in response to the adverse weather conditions imposed upon the buoyant actuator 19. Specifically, a number of the hexagonal facets 107 of the buoyant actuator 19 are each designed as a pair of hinged flaps 145. This is illustrated schematically in Figure 13 which is a plan view of one of these hexagonal facets 107. Figure 14 is a cross section along the line 14-14 of Figure 13.

Each of these hexagonal facets 107 comprises the pair of two identical semi- hexagonal flaps 145 that are hingedly connected along a major axis 147 of the facet. A hinge shaft 149 extends between adjacent facets 101a, 101b and the flaps 149 are hingedly mounted on the shaft. The two flaps 145 have interspaced lugs 147 with bores therein through which the hinge shaft 149 extends to enable the flaps 145 to be mounted so that the adjacent edges thereof are closely aligned.

Each semi-hexagonal flap 145 is pivotally movable between a closed condition which it normally occupies and which is in the plane of the facet 107, and an open condition in which it swings outwardly to establish an opening 143 in the outer shell 102. Each flap 145 is biased towards its closed condition. This may be achieved by use of a spring mechanism to apply a spring force to assist in closing of the flap. The spring mechanism may be incorporated in the hinge 148. The spring force needs to be relatively weak in the sense that it will facilitate closure only after the sea conditions have subsided and the flap is just luffing. However, it may not be necessary to have provision for spring loading on the flaps as the flaps may self-close merely with the gentle motion of the buoyant actuator 19.

A releasable coupling 153 is provided for releasably maintaining each flap 145 in the closed condition. The releasable coupling 153 is adapted to actuate to release the flap 145 to allow it to move from the closed condition to the open condition to establish the opening 143 in response to the adverse weather conditions. In the illustrated arrangement, the releasable coupling 153 comprises a magnetic coupling utilising a magnetic attractive force to maintain the respective flap in the closed condition. Specifically, the magnetic coupling comprises a plurality of magnets 155 provided at locations along the free edge 157 of the flap 145 and at corresponding location along the adjacent edges of adjacent facets 101c, 101d, 101e, and 101f. Each magnet 155 is selected to require a force equivalent to a weight of about 50kg to release it. Steel strips 159 are provided on the edges of adjacent facets to which the magnets 155 are attracted to provide the closing. In this way, the flaps 145 will remain in closed conditions defining a hexagonal facet until the force against them is sufficient to overcome the magnetic attraction, thus forcing the flaps to release and open up. The number of magnets 155 is selected depending upon the requirements.

The buoyant actuator 19 does not need to be completely watertight in order to function in the manner described. Indeed in normal operation the buoyant actuator 19 is filled with water and this entrapped water moves with the buoyant actuator as a contiguous entity even if there is a slight flow past the lips of the flaps.

It is a further feature that the buoyant actuator 19 is fault tolerant to flap failure. If one flap 145 were to fail open in normal operation (due, for example, to a failure in the magnetic latch, or a broken hinge) there would still not be a flow passage established for water to enter and then leave the hollow interior of the buoyant actuator 19 to an extent which would adversely affect its operation. For there to be flow that might adversely affect operation of the buoyant actuator 19 there would need to be at least two flaps open, and the probability of two flaps failing open is considerably less than the probability of just one flap failing.

Referring now to Figures 15 to 25, each pump 15 according to the embodiment comprises an elongated body 171 of tubular construction having interior 172. In this embodiment, the elongated body 171 is of circular cross-section. The elongated body 171 has an exterior sidewall 173 which in this embodiment is formed as an upper side wall section 175, an intermediate side wall section 176 and a lower side wall section 177 connected together. The pump body 171 has an upper end which is closed by a top wall 181 and a lower end which is closed by a lower wall 183. The lower wall 183 is configured for attachment of the base 17 by means of the connection 77.

The interior 172 comprises an upper potion 178 defined within the upper side wall section 175 and a lower portion 179 defined within the intermediate side wall section 176 together with the lower side wall section 177.

An intake chamber 185 and a discharge chamber 187 reside within lower portion 179 of the interior 172 of the body 171. The intake chamber 185 is defined between the lower wall 183 and a lower internal portion 191 within ttie interior 172. The discharge chamber 187 is defined between the lower internal portion 191 and an upper internal portion 193 which incorporates a cylindrical interior side wall portion 195 and an end wall portion 197 in opposed relation to and spaced from the lower internal portion 191. The interior side wall portion 195 is spaced inwardly from the exterior side wall 173 of the body 171 such that an annular space 198 is defined therebetween.

A piston mechanism 201 is accommodated in the lower section 179 of the interior 172 and extends between the intake chamber 185 and the discharge chamber 187. The piston mechanism 201 is of hollow construction and incorporates a transfer passage 203 having one end 205 thereof communicating with the intake chamber 185 and the other end 207 thereof communicating with the discharge chamber 187.

The piston mechanism 201 comprises a piston base 209 and a piston tube 211 extending upwardly from the base 209. The piston tube 211 passes through an opening 213 in the lower portion 191 to extend between the intake chamber 185 and the discharge chamber 187. A seal 215 provides a fluid seal around the piston tube 211 between the intake chamber 185 and the discharge chamber 189.

The lower internal portion 191 and the upper internal portion 193 are clamped within a bolted flanged coupling 213 between the intermediate and lower wall sections 176, 177 of the body 171. The transfer passage 203 provides a chamber 219 within the piston mechanism 201. An intake check valve 221 is provided in the base 209 of the piston below the piston chamber to allow flow into the piston chamber 219 upon a downstroke of the piston mechanism 201 while preventing flow in the reverse direction upon upstroke of the piston.

The discharge chamber 187 and the piston chamber 219 cooperate to define a pumping chamber 223

The pump 15 has an inlet potion 225 which defines the pump inlet 27 and which opens onto the intake chamber 185.

The pump 15 has an outlet potion 227 which defines the pump outlet 29 and which opens onto the discharge chamber 187 at discharge port 229. The outlet portion 227 incorporates a check valve arranged to allow flow under pressure outwardly from the discharge chamber 187 while preventing return flow.

The pumping chamber 223 undergoes expansion and contraction in response to reciprocatory movement of the piston mechanism 201. The reciprocatory motion of the piston 201 comprises an upstroke (corresponding to volume contraction of the pumping chamber 223) and a downstroke (corresponding to volume expansion of the pumping chamber 223). In this way, the pump 15 performs a pumping stroke upon upward movement of the piston mechanism 201 and an intake stroke upon downward movement of the piston mechanism 201.

The piston mechanism 201 further comprises a lifting mechanism 241 adapted to operably couple the piston mechanism 201 to the tether 23.

The lifting mechanism 241 comprises a lifting head 243 and a plurality of lifting arms 245 extending outwardly from the lifting head 243 to the piston base 209. The lifting arms 245 extend through the annular space 198 and also through openings 247 in the two internal portions 191 , 193. The openings 247 are configured to guide movement of the lifting arms 245 and may incorporate bushes 248. The bushes 248 are advantageously formed of a material exhibiting low friction material when in seawater, one example of such material being Vesconite™.

The tether 23 is connected to the lifting mechanism 241 through a gearing means 251 accommodated in the upper portion 176 of the pump interior 172. The purpose of the gearing means 251 is to translate the reciprocating motion of the buoyant actuator 19, and hence the reciprocating motion of the tether 23, into a shorter pumping stroke length at the piston. This can be useful as smaller stroke lengths (which correspond to smaller stroke velocities) are advantageous for achieving reliable high pressure sealing (along with larger piston diameters).

The top wall 181 of the pump body 171 incorporates an aperture 253 through which the lower portion 23a of the tether 23 extends via a sheath 255 which is attached to a fitting 257 on the top wall 181 by a sheath seal 258. The purpose of the sheath 255 is to protect the tether 23 from foreign matter (such as scale and marine Crustacea) which might otherwise accumulate on it. This avoids the potential for accumulated foreign matter entering the pump to foul its workings.

The lower portion 23a of the tether 23 comprises a section of rope 259 which is utilised as part of the gearing means 251 , as will become apparent.

The gearing means 251 is configured as a pulley mechanism 261 comprising an axle assembly 263 having a rotational axis transverse to the direction of reciprocation of the tether 23 and also transverse to the direction of reciprocation of the pump piston mechanism 201. The axle assembly 263 comprise a first axle section 265 and two second axle sections 267 disposed one to each side of the first axle section. The first axle section 265 is of a larger diameter than the two second axle sections 267. The two second axle sections 267 each has the same diameter as the other.

The rope section 259 is connected to, and winds about, the first section 265 of the axle assembly. The lifting assembly 241 is coupled to the axle assembly 263 by two ropes 269, each of which is connected to, and winds about, one of the two second sections 267 of the axle assembly 263. In the arrangement shown, the axle assembly 263 comprises a shaft 271. A wheel 273 is mounted on the shaft 271 to provide the first axle section 265 and two circumferential grooves 275 are formed in the shaft 271 to provide the second axle sections 267. The wheel 273 is fixed to the shaft 271 for rotation therewith. The wheel 273 incorporates a circumferential groove 277 at its rim in which the rope section 259 can run. The wheel 273 has an attachment hole 279 for attachment of the end of the rope section 259 to the wheel. As mentioned earlier, the rope section 259 forms part of the gearing means 251 and will hereinafter be referred to as the wheel rope. The two ropes 269 are secured to the shaft 271 and run within the grooves 275. Each rope 269 is secured at one end to the shaft 271 , runs within the respective groove 275 around the circumference of the shaft, extends down to the lifting head 243 and is attached thereto at its other end. The ropes 269 will be hereinafter referred to as the shaft ropes. Figure 15 shows some detail of the gearing mechanism 251 , but with a portion of the wheel 273 removed for clarity.

The shaft 271 is rotatably supported at its ends in bushes 281 accommodated in bearing housings 283 incorporated in the upper side wall section 175 of the pump body 171. The bushes 281 are advantageously formed of a material exhibiting low friction material when in seawater, one example of such material being Vesconite™.

The wheel rope 259 and the two shaft ropes 269 are wound in opposite directions. The points of securement of the respective wheel rope 259 and the two shaft ropes 269 are diametrically opposed. The wheel rope 259 extends through the aperture 253 in the top wall 181 of the pump body and into the bore of a rope sheath 255. The reciprocating motion of the buoyant actuator 19 in response to wave action causes the wheel rope 259 to move up and down with the wave motion. This causes the wheel 273 to rotate, and with it the shaft 271. This rotation of the shaft 271 causes the shaft ropes 269 to move up and down, thus translating to reciprocating movement of the lifting mechanism 241 and the piston 201 as a whole.

In the arrangement shown, the wheel 273 has a diameter of about five times that of the shaft 271. As an example, the wheel 273 can have a 30cm diameter and the shaft of 6cm. Thus for a displacement of 80cm of the wheel rope 259 under the influence of wave motion, the shaft ropes 269 will displace only 16cm. In this way, the wheel 273, shaft 271 and ropes 259, 269 provides a gearing arrangement that allows a larger displacement by the buoyant actuator 19 to be translated into a shorter pumping stroke length of the piston mechanism 201.

The pump 15 is primarily made from steel, although the piston mechanism 201 can be made from other materials such as ceramic materials. The rope sheath 255 may be made from rubber, and the ropes 259, 269 can be made from any suitable material such as composite material, for example nylon and polyethylene. The upper side wall section 175 could also be made of a composite copolymer.

In operation, a wave impinging on the apparatus 10 causes uplift of the buoyant actuator 19. This uplift is transmitted through the tethers 23 to each of the three pumps 15. In each pump 15 this causes the piston mechanism 201 to lift, with the result that the pumping chamber 223 undergoes volume contraction. In this way, the pump 15 performs a pumping stroke, with some of the water confined within the pumping chamber 223 being discharged through the pump outlet 29. Once the wave has passed, the uplift force applied to the buoyant actuator 19 diminishes and the buoyant actuator descends under the weight of the various components connected thereto, including the lifting mechanism 241 and the piston 201. As the piston mechanism 201 descends, it plunges into water which has entered the intake chamber 185. As the piston mechanism 201 descends, water within intake chamber 185 flows into the piston chamber 219 and the progressively expanding pumping chamber 223. The intake check valve 221 allows entry of the water. This charges the piston chamber 219 and the discharge chamber 187 in readiness for the next pumping stroke which is performed upon uplift of the buoyant actuator 19 in response to the next wave disturbance.

It is a feature of this embodiment that that the pump 15 achieves high pressures in the pumping chamber 223 with a larger diameter piston and smaller strokes than was the case in the prior art (un-geared pumps). Both smaller stroke distance (which translates to smaller stroke velocity) and larger piston diameters, are favourable properties for achieving reliable high pressure sealing. Thus the design of a high pressure geared pump leads to more reliable sealing. A number of apparatus 11 can be provided in an array 290. Examples of the arrays 290 that can be implemented are shown in Figures 26, 27 and 28. In each instance, the low pressure inlet 55 and the high pressure outlet 57 of each of the bases 17 are respectively connected to low pressure manifolds 64 and the high pressure manifolds 66.

The spacing between units (being apparatus 11 ) and the patterning of the arrays are features that are optimised with respect to the actual wavelength of the dominant sea state and the directions of the waves.

The arrangement is optimised for operation in shallow waters of about 10 m depth or less. This arises through having a much larger volume for the buoyant actuator

19 than would be allowed by the prior art arrangements comprising a single pump and float as well as the fact that a large buoyant actuator attached to the tripod arrangement comprising the triangular base 17 and three pumps 15 disposed at inclined attitudes in shallow water is able to extract energy from the horizontal and vertical wave motions, the horizontal wave motions being relatively larger than the horizontal motions in deeper waters.

As mentioned earlier, the apparatus 11 operates in conjunction with the closed loop system 25 according to the embodiment in which energy in the form of the high pressure fluid is exploited. In this embodiment the fluid comprises water and the closed loop system 25 provides high pressure water for use in power generation or a desalination plant.

Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

The Claims Defining the Invention are as Follows:

1. A reciprocating pump adapted for actuation by a reciprocating input, the pump comprising a fluid delivery means adapted for reciprocation in response to reciprocation of the input, and gearing means between the reciprocating input and the fluid delivery means, the gearing means delivering a stroke length to the fluid delivery means different from the stroke length of the reciprocating input.

2. The reciprocating pump according to claim 1 wherein the gearing means delivers a reduction in the stroke length of the fluid delivery means in relation to the stroke length of the reciprocating input.

3. The reciprocating pump according to claim 1or 2 wherein the gearing means comprises a pulley mechanism coupling the fluid delivery means to the reciprocating input.

4. The reciprocating pump according to claim 1 , 2 or 3 wherein the pulley means comprises an axle assembly rotatable about an axis transverse to the direction of the strokes of the input and the fluid delivery means, at least one first flexible elongate element connected at one end to the axle assembly and adapted to wind around the axle assembly at a first radial distance from the axis, the first elongate flexible element being coupled to the reciprocating input, and at least one second flexible elongate element connected to the axle and adapted to wind around the axle assembly at a second radial distance from the axis, the second elongate flexible element being coupled to the fluid delivery means, the second radial distance being different from the first radial distance to provide the gearing.

5. The reciprocating pump according to claim 5 wherein the first flexible elongate element and the at least one second flexible elongate element wind about the axle assembly in different directions.

6. The reciprocating pump according to claim 5 wherein the axle assembly comprises a first section about which the first elongate element is adapted to wind, and at least one second section about which the at least one second elongate element is adapted to wind.

7. The reciprocating pump according to claim 5 or 6 wherein there are two second elongate flexible elements and thus two second sections about which the two elongate flexible elements wind.

8. The reciprocating pump according to claim 7 wherein the two second sections are disposed one to each side of the first section.

9. The reciprocating pump according to claim 6, 7 or 8 wherein the axle assembly comprises a shaft, the first section comprises a wheel on the shaft and each second section comprises a circumferential groove in the shaft.

10. The reciprocating pump according to any one of the preceding claims wherein the reciprocating fluid delivery means comprises a reciprocating piston mechanism within the pump.

11. A reciprocating pump adapted for actuation by wave energy delivering a reciprocating input, the pump comprising a fluid delivery means adapted for reciprocation in response to reciprocation of the input, and gearing means between the reciprocating input and the fluid delivery means, the gearing means delivering a stroke length to the fluid delivery means different from the stroke length the reciprocating input.

12. A wave energy system having a reciprocating pump according to any one of the preceding claims.

13.A wave energy system comprising a buoyant actuator responsive to wave motion, a reciprocating pump comprising an input adapted to reciprocate in response to reciprocating motion of the buoyant actuator under the influence of wave motion, a fluid delivery means adapted for reciprocation in response to reciprocation of the input, and gearing means between the reciprocating input and the fluid delivery means, the gearing means delivering a stroke length to the fluid delivery means different from the stroke length the reciprocating input.

14. A reciprocating pump substantially as herein described with reference to the accompanying drawings.

15. A wave energy system substantially as herein described with reference to the accompanying drawings.