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WO2009076714A1 - Apparatus for extraction of energy from wave motion - Google Patents

Apparatus for extraction of energy from wave motion Download PDF

Info

Publication number
WO2009076714A1
WO2009076714A1 PCT/AU2008/001855 AU2008001855W WO2009076714A1 WO 2009076714 A1 WO2009076714 A1 WO 2009076714A1 AU 2008001855 W AU2008001855 W AU 2008001855W WO 2009076714 A1 WO2009076714 A1 WO 2009076714A1
Authority
WO
WIPO (PCT)
Prior art keywords
base
buoyant actuator
pumps
devices
pump
Prior art date
Application number
PCT/AU2008/001855
Other languages
French (fr)
Inventor
Alan Robert Burns
Petru Tinc
Matt Keys
Original Assignee
Seapower Pacific Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2007906885A external-priority patent/AU2007906885A0/en
Application filed by Seapower Pacific Pty Ltd filed Critical Seapower Pacific Pty Ltd
Publication of WO2009076714A1 publication Critical patent/WO2009076714A1/en

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B9/00—Water-power plants; Layout, construction or equipment, methods of, or apparatus for, making same
    • E02B9/08—Tide or wave power plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/18—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore
    • F03B13/1885—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom is tied to the rem
    • F03B13/189—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom is tied to the rem acting directly on the piston of a pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/18—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore
    • F03B13/1885—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom is tied to the rem
    • F03B13/1895—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom is tied to the rem where the tie is a tension/compression member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/20—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" wherein both members, i.e. wom and rem are movable relative to the sea bed or shore
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2250/00—Geometry
    • F05B2250/20—Geometry three-dimensional
    • F05B2250/23—Geometry three-dimensional prismatic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/138—Water desalination using renewable energy
    • Y02A20/144—Wave energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient

Definitions

  • This invention relates to extraction of energy from wave motion. More particularly, the invention relates to apparatus for translating wave motion into reciprocating action. The invention also relates to a wave energy conversion system.
  • apparatus for translating wave motion into reciprocating action comprising a buoyant actuator and a plurality of devices operable with a reciprocating action operably connected to the buoyant actuator, the buoyant actuator being disposed between and above the devices.
  • connection between each device and the buoyant actuator subtends an angle to the horizontal.
  • the buoyant actuator is disposed generally centrally between and above the devices.
  • the angles subtended by the connections are generally equal.
  • the connection between the buoyant actuator and each device comprises a tether.
  • the tether may comprise a flexible elongate element such as a rope.
  • each device typically, the line of reciprocating action of each device is aligned with the length of the tether.
  • the devices are anchored within a body of water subjected to the wave action.
  • the devices are anchored to a common base.
  • the base may be adapted to be anchored to the floor of the body of water.
  • the base may be configured as a suction anchor.
  • the base defines three corners at each of which there is one of the three devices.
  • the base is preferably triangular and each device is located at one apex of the triangle.
  • the base, the devices, the buoyant actuator and the connections therebetween define a triangular-based pyramid configuration resembling a tripod arrangement.
  • Each tether may subtend an angle of approximately 42 degrees to the horizontal, although it can be any suitable angle, typically between about 35 degrees and 55 degrees.
  • the devices may each comprise any appropriate type, examples of which may include a reciprocating fluid pump or a linear electric generator. In the case of fluid pumps, they may be used to generate high pressure water from low pressure water.
  • the base preferably includes an intake fluid flow path for delivery of intake fluid to the inlets of the pumps. Further, the base preferably comprises a discharge fluid flow path for transmitting outlet fluid discharged by the pumps.
  • the intake fluid flow path may communicate with an intake port provided on the exterior of the base.
  • the discharge fluid flow path may communicate with a discharge port provided on the exterior of the base.
  • the tripod arrangement allows a relatively large volume of buoyant actuator to be used for a given water depth and hence optimisation for shallow water energy capture.
  • the configuration of the base is preferably such that a number of apparatus according to the invention can be deployed in an array, such as in a tessellated arrangement.
  • Figure 1 is a schematic elevational view of apparatus according to the embodiment 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 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 partly 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 a reciprocating pump forming part of the apparatus
  • 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
  • Figure 28 is also a view similar to Figure 26 but showing the apparatus in yet another array.
  • apparatus for harnessing wave energy in a body of water and for converting the harnessed energy to high pressure fluid typically above 0.7MPa and preferably above 5.5 MPa.
  • the high pressure fluid can be used for any appropriate purpose.
  • 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 comprises a plurality of pumps 15 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.
  • the apparatus 11 according to the embodiment translates wave motion into a reciprocating pump action.
  • 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.
  • 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.
  • 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.
  • 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.
  • the pumps 15 as well as the tethers 23 are 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.
  • 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.
  • the pipe work 41 comprises mild steel pipe.
  • first and second ports 51 , 52 are provided at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 at each corner 37 of the triangular base structure 31 .
  • 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 from a low pressure manifold 64 that carries low pressure water from elsewhere, into the piping 53 via the inlet 55.
  • 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.
  • 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.
  • 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.
  • struts 111 that extend radially outwardly from a central core 113.
  • 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).
  • HDPE high density polyethylene
  • 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.
  • 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.
  • buoyant actuator 19 Due to the substantially hollow nature of the buoyant actuator 19, it is lightweight compared to prior art floats.
  • each strut 111 weights of the order of less than 35kg, with the whole float structure weighing the order of 400kg.
  • 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.
  • 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.
  • 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.
  • 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 by a hinge 148.
  • the hinge 148 comprises a hinge shaft 149 extending between adjacent facets 101a, 101b, with the flaps 145 being 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.
  • the releasable coupling 153 comprises a magnetic coupling utilising a magnetic attractive force to maintain the respective flap in the closed condition.
  • 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.
  • 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.
  • each pump 15 comprises an elongated body 171 of tubular construction having interior 172.
  • 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 the 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 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 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 mechanism 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).
  • 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
  • the bushes 248 are advantageously formed of a material exhibiting low friction material when in seawater, one example of such material being
  • 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 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.
  • 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.
  • 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 VesconiteTM.
  • 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.
  • the wheel 273 has a diameter of about five times that of the shaft 271.
  • the wheel 273 can have a 30cm diameter and the shaft of 6cm.
  • the shaft ropes 269 will displace only 16cm.
  • 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.
  • 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.
  • this causes the piston mechanism 201 to lift, with the result that the pumping chamber 223 undergoes volume contraction.
  • 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.
  • 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.
  • the piston mechanism 201 descends, it plunges into water which has entered the intake chamber 185.
  • a number of apparatus 11 can be provided in an array 290.
  • the construction of the base 17 incorporating the pipe work 41 is particularly advantageous as it allows apparatus 11 in the array 290 to be conventionally hydraulically coupled together. Examples of the arrays 290 that can be implemented are shown in Figures 26, 27 and 28.
  • 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 triangular configuration of the base 17 allows the basses of apparatus in the array to be positioned in a tessellated arrangement if desired.
  • 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 included altitudes 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.
  • 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.
  • the fluid comprises water and the closed loop system 25 provides high pressure water for use in power generation or a desalination plant.

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Abstract

Apparatus (11) for harnessing wave energy in a body of water and for converting the harnessed energy to high pressure fluid. 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) comprises three pumps (15) 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) suspended within the body of seawater (12) between and above the pumps but below the water surface (13). Each pump (15) is activated by movement of the buoyant actuator (19) in response to wave motion. Thus, the apparatus (11) translates wave motion into a reciprocating pump action. Each pump (15) is operatively connected to the buoyant actuator (19) by a coupling (21) comprising a tether (23). The base (17) typically comprises a generally triangular structure (31) having three sides (33) interconnected at corners (35), with one of the three pumps (15) connected to each corner (35) of the triangular base. The buoyant actuator (19) is positioned above, and is centrally located with respect to, the three pumps (15).

Description

Apparatus for Extraction of Energy from Wave Motion
Field of the Invention
This invention relates to extraction of energy from wave motion. More particularly, the invention relates to apparatus for translating wave motion into reciprocating action. The invention also relates to a wave energy conversion system.
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 provide apparatus which couples wave motion to a device operable in response to wave motion. One example of such apparatus utilizes a float to translate wave motion into a reciprocating pump action. Typically, the float is disposed generally vertically above the pump and is coupled thereto by a tether. The required stroke length for operation of the pump necessitates that there be a certain depth of water available for installation of the apparatus. Consequently, such apparatus cannot normally be deployed in relatively shallow water conditions which are generally more convenient as they are located closer to shore. Furthermore, such floats are generally not well-suited for intercepting the horizontal wave motions that exist in shallow water conditions.
It is against this background and the problems and difficulties associated therewith that the present invention has been developed. Accordingly, it is an object of the present invention to address at least one of the problems or difficulties of previously known apparatus as described above, or at least provide a useful choice as an alternative. Brief Description of the Invention
According to a first aspect of the invention there is provided apparatus for translating wave motion into reciprocating action, the apparatus comprising a buoyant actuator and a plurality of devices operable with a reciprocating action operably connected to the buoyant actuator, the buoyant actuator being disposed between and above the devices.
With this arrangement, the connection between each device and the buoyant actuator subtends an angle to the horizontal.
Preferably, the buoyant actuator is disposed generally centrally between and above the devices. With this arrangement, the angles subtended by the connections are generally equal.
The connection between the buoyant actuator and each device comprises a tether. The tether may comprise a flexible elongate element such as a rope.
Typically, the line of reciprocating action of each device is aligned with the length of the tether.
Preferably, the devices are anchored within a body of water subjected to the wave action.
Preferably, the devices are anchored to a common base.
The base may be adapted to be anchored to the floor of the body of water. In this regard, the base may be configured as a suction anchor.
Preferably, there are three devices.
Preferably, the base defines three corners at each of which there is one of the three devices. With such an arrangement, the base is preferably triangular and each device is located at one apex of the triangle. In this arrangement, the base, the devices, the buoyant actuator and the connections therebetween define a triangular-based pyramid configuration resembling a tripod arrangement. Each tether may subtend an angle of approximately 42 degrees to the horizontal, although it can be any suitable angle, typically between about 35 degrees and 55 degrees.
The devices may each comprise any appropriate type, examples of which may include a reciprocating fluid pump or a linear electric generator. In the case of fluid pumps, they may be used to generate high pressure water from low pressure water.
Where the devices comprise reciprocating fluid pumps, the base preferably includes an intake fluid flow path for delivery of intake fluid to the inlets of the pumps. Further, the base preferably comprises a discharge fluid flow path for transmitting outlet fluid discharged by the pumps.
The intake fluid flow path may communicate with an intake port provided on the exterior of the base.
The discharge fluid flow path may communicate with a discharge port provided on the exterior of the base.
The tripod arrangement allows a relatively large volume of buoyant actuator to be used for a given water depth and hence optimisation for shallow water energy capture.
The configuration of the base is preferably such that a number of apparatus according to the invention can be deployed in an array, such as in a tessellated arrangement.
According to a second aspect of the invention there is provided a wave energy system incorporating apparatus according to the first aspect of the invention. 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 according to the embodiment 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 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 partly 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 a reciprocating pump forming part of the apparatus;
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, there is shown apparatus for harnessing wave energy in a body of water and for converting the harnessed energy to high pressure fluid, typically above 0.7MPa and preferably above 5.5 MPa. The high pressure fluid can be used for any appropriate purpose. In this embodiment the high pressure fluid comprises water used for power generation and/or desalination.
In the arrangement illustrated, 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 comprises a plurality of pumps 15 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. Thus, the apparatus 11 according to the embodiment translates wave motion into a reciprocating pump action.
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 from 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 by a hinge 148. The hinge 148 comprises a hinge shaft 149 extending between adjacent facets 101a, 101b, with the flaps 145 being 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 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 the 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 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 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 mechanism 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 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 arrangement 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. The construction of the base 17 incorporating the pipe work 41 is particularly advantageous as it allows apparatus 11 in the array 290 to be conventionally hydraulically coupled together. 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.
Further, the triangular configuration of the base 17 allows the basses of apparatus in the array to be positioned in a tessellated arrangement if desired.
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 included altitudes 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.
From the foregoing, it is evident that the present invention provides a simple yet highly effective arrangement for translation of wave action (including vertical and horizontal components thereof) into a reciprocating action. 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 is as Follows:
1. Apparatus for translating wave motion into reciprocating action, the apparatus comprising a buoyant actuator and a plurality of devices operable with a reciprocating action operably connected to the buoyant actuator, the buoyant actuator being disposed between and above the devices.
2. The apparatus according to claim 1 wherein the buoyant actuator is disposed generally centrally between and above the devices.
3. The apparatus according to claim 1 or 2 wherein the connection between the buoyant actuator and each device comprises a tether.
4. The apparatus according to claim 3 wherein the tether comprises a flexible elongate element.
5. The apparatus according to claim 3 or 4 wherein the line of reciprocating action of each device is aligned with the length of the tether.
6. The apparatus according to any one of the preceding claims wherein the devices are anchored within a body of water subjected to the wave action.
7. The apparatus according to claim 6 wherein the devices are anchored to a common base.
8. The apparatus according to claim 7 wherein the base is adapted to be anchored to the floor of the body of water.
9. The apparatus according to claim 8 wherein the base is configured as a suction anchor.
10. The apparatus according to any one of the preceding claims wherein there are three devices.
11.The apparatus according to claim 10 wherein the base defines three corners at each of which there is one of the three devices.
12. The apparatus according to any one of the preceding claims wherein at least one of the devices comprise a linear electric generator.
13. The apparatus according to any one of the preceding claims wherein at least one of the devices comprise a fluid pump.
14. The apparatus according to any one of claims 7, 8 or 9 wherein the devices comprise a plurality of fluid pumps.and wherein the base includes an intake fluid flow path for delivery of intake fluid to the inlets of the pumps.
15. The apparatus according to claim 14 wherein the base comprises a discharge fluid flow path for transmitting outlet fluid discharged by the pumps.
16. The apparatus according to claim 14 or 15 wherein intake fluid flow path communicates with an intake port provided on the exterior of the base.
17. The apparatus according to claim 14, 15 or 16 wherein the discharge fluid flow path communicates with a discharge port provided on the exterior of the base.
18. The apparatus according to any one of claims 7 to 16 wherein the base is so configured that a plurality of the apparatus can be deployed in an array, such as in a tessellated arrangement.
19.A wave energy system incorporating apparatus according to any one of the preceding claims.
20. Apparatus for translating wave motion into reciprocating action, the apparatus being substantially as herein described with reference to the accompanying drawings.
21. A wave energy system substantially as herein described with reference to the accompanying drawings.
PCT/AU2008/001855 2007-12-17 2008-12-17 Apparatus for extraction of energy from wave motion WO2009076714A1 (en)

Applications Claiming Priority (2)

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AU2007906885 2007-12-17
AU2007906885A AU2007906885A0 (en) 2007-12-17 Apparatus for Extraction of Energy from Wave Motion

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WO2011116100A3 (en) * 2010-03-18 2012-08-16 Resolute Marine Energy, Inc. Wave-energy converter
EP2606225A1 (en) * 2010-08-16 2013-06-26 CETO IP Pty Ltd Wave energy conversion
WO2014153618A1 (en) 2013-03-28 2014-10-02 Ceto Ip Pty Ltd Deployment system
US9581129B2 (en) 2010-05-28 2017-02-28 Seabased Ab Wave power unit, a use of a such and a method of producing electric energy
NO346423B1 (en) * 2020-07-03 2022-08-01 Erik Alf Hasle Floating wave energy converter unit
CN116062200A (en) * 2023-02-17 2023-05-05 哈尔滨工程大学 Sucker type wave energy self-generating unmanned aerial vehicle

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CN112253365B (en) * 2020-10-15 2022-01-18 安徽工业大学 Electromechanical conversion device of wave-activated generator

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Publication number Priority date Publication date Assignee Title
WO2011116100A3 (en) * 2010-03-18 2012-08-16 Resolute Marine Energy, Inc. Wave-energy converter
US9581129B2 (en) 2010-05-28 2017-02-28 Seabased Ab Wave power unit, a use of a such and a method of producing electric energy
EP2606225A1 (en) * 2010-08-16 2013-06-26 CETO IP Pty Ltd Wave energy conversion
EP2606225A4 (en) * 2010-08-16 2014-12-24 Ceto Ip Pty Ltd Wave energy conversion
EP3150845A3 (en) * 2010-08-16 2017-07-05 CETO IP Pty Ltd Wave energy conversion
WO2014153618A1 (en) 2013-03-28 2014-10-02 Ceto Ip Pty Ltd Deployment system
US9726142B2 (en) 2013-03-28 2017-08-08 Ceto Ip Pty Ltd. Deployment system
NO346423B1 (en) * 2020-07-03 2022-08-01 Erik Alf Hasle Floating wave energy converter unit
CN116062200A (en) * 2023-02-17 2023-05-05 哈尔滨工程大学 Sucker type wave energy self-generating unmanned aerial vehicle
CN116062200B (en) * 2023-02-17 2023-08-29 哈尔滨工程大学 Sucker type wave energy self-generating unmanned aerial vehicle

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CL2008003768A1 (en) 2009-12-28

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