Note: Descriptions are shown in the official language in which they were submitted.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-1-
Energy Release Buoyant Actuator
Field of the Invention
This invention relates to an energy release buoyant actuator responsive to
wave
motion, and more particularly to such a buoyant actuator for coupling wave
motion
to a device operable in response to wave motion. The invention also relates to
a
wave energy conversion system.
The invention has been devised particularly, although not necessarily solely,
as a
buoyant actuator for harnessing wave energy and for converting the harnessed
energy to linear motion for driving an energy conversion device such as a
fluid
pump or a linear electric generator. In such an arrangement, the buoyant
actuator
may be operably connected to the energy conversion device, the actuator being
buoyantly suspended within the body of water, but typically below the water
surface. The buoyant actuator is in effect a submerged float which moves in
response to wave action within the body of water.
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 device operable in response to wave
motion, one example of which is use of a float to translate wave motion Into a
reciprocating pump action. Typically such floats are of solid construction and
comprise buoyant material such as foam.
When exposed to an aggressive sea state, typically adverse weather conditions
(such as in storm conditions), floats can be subject to extreme forces. Known
floats can be prone to damage, collapse or detachment when exposed to such
conditions. Further, tethers to which the floats are connected can be damaged
or
CA 02758989 2011-10-07 PCT/AU2010/000398
- 2 - Received 13 May 2011
ruptured in such conditions. Also, it may be desired to control the movement
of the buoyant actuator so as to limit the pump strokes and the loading on the
attached equipment.
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 floats, or at least provide a useful choice
as
an alternative.
Brief Description of the Invention
.10 According to a first aspect of the invention there is provided a buoyant
actuator responsive to wave motion comprising a body defining an interior
volume comprising at least one gate means to vary the response of the
buoyant actuator to the wave motion, wherein the gate means is confined
within the interior volume.
Preferably, the gate means is adapted to permit water to flow through .the
body of the buoyant actuator.
Preferably, the gates means is responsive to a particular sea state.
In one arrangement, the particular sea state is an aggressive sea state in
adverse weather conditions (such as storm conditions). This is for the
purpose of maintaining the integrity of the buoyant actuator when exposed to
such conditions, and also any mechanism to which the buoyant actuator is
coupled.
Preferably, the gate means may comprise at least one closure element
movable between a closed condition which it normally occupies and which
impedes water flow through the body, and an open condition in which it
permits water flow through the body.
Amended Sheet
IPEA/AU
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-3-
Preferably, a releasable coupling is provided for releasably maintaining the
closure element in the closed condition.
Preferably, the releasable coupling is adapted to actuate to release the
closure
element to allow, it to move from the closed condition to the open condition
to
establish the opening. The release may be actuated by the sea state or by
remote
control.
Preferably, the releasable coupling comprises a magnetic coupling. The
magnetic
coupling may utilise a magnetic attractive force to maintain the closure
element in
the closed condition. The magnetic coupling may comprise a plurality of
magnets
provided on the respective closure element and/or at corresponding locations
along a part of the body against which the closure element locates when in the
closed condition. In this way, the closure elements will remain in closed
conditions
until the force against them is sufficient to overcome the magnetic
attraction, thus
forcing the flaps to release and swing away from the closed condition to
establish
16 the opening.
Preferably the closure element comprises a flap.
Preferably, the flap is pivotally movable between a closed condition which it
normally occupies and which impedes water flow through the body, and an open
condition in which it swings outwardly to permit water flow through the body.
The magnetic attractive force may be configured to a particular wave motion by
varying any or more of the following: the number of magnets, the strength of
the
magnets and the gap which the magnetic field traverses to provide the
attractive
force.
The magnetic attractive force may be adjustable
The magnetic attachment means are adjusted from a remote location.
Preferably, the magnetic attachment means are electromagnetic.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-4-
The magnetic coupling may comprise a magnet means on the closure element
adjacent the inner end thereof and a mating part to which the magnet means is
magnetically attracted. The mating part may comprise a striker plate. The
magnetic coupling Is operable to retain the,respective closure element in the
closed condition until the force against the closure element is sufficient to
overcome the magnetic attraction, thus forcing the magnetic coupling to
release
the closure element and swing away from the closed condition to establish an
opening to allow the water flow though the body.
The magnet means may comprise an array of permanent magnets
accommodated within a housing. The housing is adapted to isolate the magnets
from the water environment in which the buoyant actuator is intended to
operate.
The housing may comprise non-magnetic, non-porous material (such as a plastic
polymer) in which the permanent magnets are encased. Preferably, the plastic
polymer material would have some resilient properties to offer some physical
dampening. Typically, the permanent magnets would be molded into the housing.
Such an arrangement is advantageous as it also confines the permanent magnets
and retains them in position within the housing and also in position relative
to
each other.
The housing may present a contact face to confront the mating part of the
magnetic coupling. The permanent magnets may be recessed with respect to the
contact face to provide the housing with a cushioning portion between the
contact
face and the permanent magnets. The contact face may also function as a wear
surface, protecting the recessed permanent magnets from the effects of wear
upon contact between the magnet means and the mating part.
Typically, the housing is removable and replaceable, as necessary.
The cushioning portion Is preferably integral with the housing. In another
arrangement, the cushioning may be provided by a layer of cushioning material
applied to the housing for contact with the mating part of the magnetic
coupling.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-5-
Preferably, the at least one closure element closes by its own weight.
However,
in another arrangement, the at least one closure element may be biased towards
its closed condition. This may be achieved by use of a biasing mechanism, such
as Incorporation of a spring in the hinge for the closure element.
In a further arrangement, the hinged closure element may be biased in the
closed
condition via a rubber spring mechanism attached to a free end of the at least
one
flap.
Typically, the gate means comprises a plurality of closure elements. This is
advantageous as it renders the buoyant actuator fault tolerant to closure
element
failure. If one closure element were to fail open in, normal operation there
would
still not be a sufficient flow passage established for water to enter and then
leave
the hollow interior of the buoyant actuator to an extent which would adversely
affect its operation. For there to be flow that might adversely affect
operation of
the buoyant actuator there would need to be at least two closure elements
open,
and the probability of two closure elements failing open is considerably less
than
the probability of just one closure element failing.
Preferably, the closure elements are configured to cooperate with each other
to
provide a barrier across the flow path through the body, each closure element
being moveable into and out of a condition in which it cooperates with the
other
closure elements to. provide the barrier. The barrier need not necessarily
block
flow entirely through the body but rather simply impede that flow to the
necessary
extent.
In one arrangement, the barrier provided by the closure elements extends
across
the flow path to be substantially normal to the direction of flow of water
through
the body.
In another arrangement, the barrier is of raked construction such that each
cl osure element when in the closed condition is inclined to the direction of
flow of
water through the body. Specifically, each closure element may be inclined in
the
direction towards the open upper end of the body; that is, the inner end of
each
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
6
closure element is closer to the open upper end of the body than the outer end
when in the closed condition, but still within the confines of the body. In
this way,
the range of movement of the closure elements between the fully closed and
fully,
open conditions Is reduced. With this arrangement, the closure elements when
in
the closed condition provided the barrier with the raked and somewhat conical
configuration.
Preferably, the releasable couplings of each closure element may be actuated
by
the same sea conditions.
In one arrangement, the body may be configured to have a longitudinal extent
and
to provide a flow path along which the water can flow though the body parallel
to
the longitudinal axis of the body.
In another arrangement, the body may be of frusto-conical configuration having
an
upper end, a lower end and a side extending between the two ends. With this
arrangement, the side is of convex shape and preferably bulging at the middle.
Preferably the body is of modular construction.
Preferably the body comprises an inner structure supporting a shell which
defines
an upper end, a lower end and the side.
The shell may comprise a plurality of sections configured as panels adapted to
be
connected together. The panels may be arranged in at least two rows comprising
an upper row and a lower row. The upper row defines an upper edge at the upper
end of the body and the lower row defines a lower edge at the lower end. The
upper edge bounds the upper portal and the lower edge bounds the lower portal.
Preferably, there are two rows, being the upper row and the lower row, and the
panels are each of the same configuration so that any panel can be located at
any
position within either row. This, is advantageous as it facilitates cost-
effective
manufacture of the panels and ready assembly of the panels into the shell.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-7-
Preferably, each panel is of generally rectangular construction.
Preferably, the connections between adjacent panels comprise half lap joints.
The body may be provided with one or more anchoring points to facilitate
movement of the buoyant actuator once deployed in water.
Under certain combinations of hydrodynamic conditions and motion of the
buoyant actuator in the moving body of water, it is possible. for the flaps to
close
with excessive force, in effect being slammed shut rather than closing gently.
With a view to mitigating this problem, some form of physical dampener may be
provided between the contacting surfaces. This dampener may take the form of
shaped pieces of elastomeric material with appropriate energy damping
properties, attached to either or both contacting surfaces; for example, the
elastomeric material can be attached to each flap or the mating part of the
body.
Other dampening arrangements are, of course, possible; for example, the
swinging motion of the flaps could be dampened hydraulically or by way of
electrical (eddy current) damping control. Further, both elastomeric damping
on
contacting surfaces, and dampening of the swinging motion by hydraulic or
electrical (eddy current) means may be provided.
A suitable hydraulic dampener may comprise a dashpot in which the viscous
fluid
comprises water drawn from, and expelled into, the water environment in which
the buoyant actuator is deployed. The piston of the dashpot may be fitted with
a
resilient bumper for contact with the respective flap, the arrangement being
that
resilient nature of the bumper affords some initial cushioning to the closing
action
of the flap.
According to a second aspect of the invention there is provided a buoyant
actuator responsive to wave motion comprising a body incorporating a flow path
along which water can flow, and a gate means for controlling flow along the
flow
path, the gate means comprising a plurality of closure elements configured to
cooperate with each other to provide a barrier across the flow path through
the
CA 02758989 2011-10-07' PCT/AU2010/000398
Received 4 February 2011
-8-
body, each closure element being moveable into and out of a condition in which
it
cooperates with the other closure elements to provide the barrier, wherein the
barrier is so configured and positioned to be within the confines of the body
and
wherein the closure elements which constitute the barrier remain within the
confines of the body even when in the fully open condition. The barrier need
not
necessarily block flow entirely through the body but rather simply impede that
flow
to the necessary extent.
When one or more closure elements have moved out of the condition in which
they cooperate with the other closure elements to provide the barrier, the
barrier
opens to permit fluid flow therethrough. In effect, the closure elements are
configured as hatches which can open and close, and when in the closed
condition provide the barrier. When in the open condition the hatches each
provide an opening within the barrier through which water can flow.
In one arrangement, the barrier provided by the closure elements extends
across
the flow path to be substantially normal to the direction of flow of water
through
the body.
In another arrangement, the barrier is of raked construction such that each
closure element when in the closed condition is inclined to the direction of
flow of
water through the body. Specifically, each closure element may be inclined in
the
direction towards the open upper end of the body; that is, the inner end of
each
closure element is closer to the open upper end of the body than the outer end
when in the closed condition. In this way, the range of movement of the
closure
elements between the fully closed and fully open conditions is reduced. With
this
arrangement, the closure elements when in the closed condition provided the
barrier with the raked and somewhat conical configuration.
According to a third aspect of the invention there is provided a buoyant
actuator
responsive to wave motion comprising a body having a support structure adapted
to receive a plurality of sections defining a chamber for interrupting water
flow
Amended Sheet
IPEA/AU
CA 02758989 2011-10-07 PCT/AU2010/000398
-9 - Received 13 May 2011
through the body, wherein the support structure and the plurality of sections
are
adapted to be transported and assembled in situ, and wherein the chamber
comprises at least one gate means to vary the response of the buoyant actuator
to
the wave motion, wherein the gate means is confined within the chamber
The body may be of any appropriate shape such as, for example, cylindrical,
spherical, frusto-spherical, or frusto-conical. The shape of the body may be
configured by provision of profiled elements thereon. The profiled elements
may be
of buoyant construction; typically being formed of buoyant material with a low
specific gravity, such as foam material.
Preferably, each section comprises a frame having two ends, one end adapted to
receive a wall portion and the other end adapted for connection to the support
structure.
Preferably, the plurality of sections is adapted to couple to one another to
define the
chamber for interrupting water flow through the body.
In one arrangement, a hydrodynamic property of the buoyant actuator may be
selectively varied. This may allow the performance characteristics of the
buoyant
actuator to be calibrated according to the environment in which the buoyant
actuator
is operating at any particulartime (including, for example, the likely sea
state).
The variation to the hydrodynamic property may comprise a variation to the.
buoyancy (either positively or negatively) or a variation to the response area
(such
as the volume or configuration) of the body, as well as a combination thereof.
Where the hydrodynamic property being varied is the -buoyancy of the buoyant
actuator, the variation may be achieved by addition or removal of buoyant
material
in the buoyant actuator. For example, the variation to the buoyant material
may
25' comprise addition of buoyant material to, or extraction of buoyant
material from, the
support structure. This may be achieved in an automatic mode by addition or
removal of a fluid (liquid or gas).The variation to the response may entail a
variation
of the configuration of the body. The configuration of the body may be varied
by use
of profiled elements, as alluded to earlier. Byway of example, the outer shape
of the
Amended Sheet
IPEA/AU
CA 02758989 2011-10-07 PCT/AU2010/000398
- 10 - Received 13 May 2011
buoyant actuator may be varied by attaching, for example, buoyant material to
the
exterior surface of the buoyant actuator.
According to a fourth aspect of the invention there is provided a buoyant
actuator
for immersion in a body of water, the buoyant actuator comprising a body
defining a
hollow interior adapted to receive a volume of water from the surrounding
water
body,.the body having flow control means for controlling flow through the
hollow
interior, the flow control means having a first condition for blocking or at
least
impeding fluid flow through the body and a second condition permitting fluid
flow
through the hollow interior, wherein the flow, control means are confined
within the
interior volume.
Preferably, the flow control means are adjustable.
In an arrangement, the flow control means may be remotely adjustable. -
According to a fifth aspect of the invention there is provided a buoyant
actuator
responsive to wave motion comprising a body defining an interior volume, the
body
comprising an inner structure supporting a shell which defines the inner
volume, the
shell comprising a plurality. of sections configured as panels adapted to be
connected together, the interior volume comprising at least one gate means to
vary
the response of the buoyant actuator to the wave motion, wherein the gate
means
is contained within the interior volume.
According to a sixth aspect of the invention there is provided a buoyant
actuator
responsive to wave motion comprising a body defining an interior volume,
comprising at least one gate means to vary the response of the buoyant
actuator to
the wave motion, wherein the gate means is confined within the interior
volume, the
body being of frusto-conical configuration having an open upper end, an open
lower
end and a side extending between the two ends. With this arrangement, the side
is
of convex shape and preferably bulging at the middle.
According to a seventh aspect of the invention there is provided a buoyant
actuator
responsive to wave motion comprising a body incorporating a flow path along
which
water can flow, and a gate means for controlling flow along the flow path, the
gate .
Amended Sheet
IPEA/AU
CA 02758989 2011-10-07 PCT/AU2010/000398
- 11 - Received 13 May 2011
means comprising a plurality of closure elements providing a barrier across
the flow
path through the body, the closure elements being moveable into and out of a
condition in which it cooperates with the other closure elements to provide
the
barrier, and latch means for releasably retaining each closure element in said
condition, the latch means comprising a magnetic coupling, wherein the barrier
is
so configured and positioned to be within the confines of the body and wherein
the
closure elements which constitute the barrier remain within the confines of
the body
even when in the fully open condition.
According to an eighth aspect of the invention there is provided a kit for
assembling.
a buoyant actuator according to any one of the preceding aspects of the
invention
as set forth above.
According to a ninth aspect of the invention there is provided a kit for
assembling a
buoyant actuator responsive to wave motion, the kit comprising a support
structure
and a plurality of sections adapted for connection to the support structure to
assemble the buoyant actuator and define a chamber, and at least one gate
means
to vary the response of the buoyant actuator to the wave motion, wherein the
gate
means is confined within the chamber.
According to a tenth aspect of the invention there is provided a wave energy
conversion system comprising at least one buoyant actuator according to any
one
of the preceding aspects of the invention as set forth above.
Preferably, the buoyant actuator is operably connected to an energy conversion
device (such as a fluid pump or a linear electric generator) to translate wave
action
thereto.
According to an eleventh aspect of the invention there is provided a method of
harnessing wave energy in a body of water, the method comprising deployment of
a
buoyant actuator according to any one of the preceding aspects of the
invention in
the body of water.
According to a twelfth aspect of the invention there is provided a buoyant
actuator
responsive to wave motion, the buoyant actuator comprising a body defining an
Amended Sheet
IPEA/AU
CA 02758989 2011-10-07 PCT/AU2010/000398
11a- Received 13 May 2011
Interior volume comprising at least one gate means to vary the response of the
buoyant actuator to the wave motion, the gate means comprising a plurality of
closure elements configured to cooperate with each other to provide a barrier
across. a flow path along which water can flow through the body, each closure
element being moveable into and out of a condition in which it cooperates with
the
other closure elements to provide the barrier, wherein the barrier is of raked
construction such that each closure element when in the closed condition is
inclined
to the direction of flow of water through the body.
According to a thirteenth aspect of the invention there is provided a buoyant
actuator responsive to wave motion comprising a body incorporating a flow path
along which water can flow, and a gate means for controlling flow along the
flow
path, the gate means comprising a plurality of closure elements configured to
cooperate with each other to provide a barrier across the flow path through
the
body, each closure element being moveable into and out of a condition in which
it
cooperates with the other closure elements to provide the barrier, wherein the
barrier'is of raked construction such that each closure element when in the
closed
condition is inclined to the direction of flow of water through the body.
Brief Description of the Drawings
The invention will be better understood by reference to the following
description of
several specific embodiments thereof as shown in the accompanying drawings in
which
Figure 1 is a perspective view of a buoyant actuator according to a first
embodiment
forming part of apparatus for harnessing ocean wave energy;
Figure 2 is a schematic perspective view of the buoyant actuator;
Figure 3 is a plan view of the buoyant actuator;
Amended Sheet
IPEA/AU
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-12-
Figure 4 is a schematic perspective view of a section of the buoyant actuator;
Figure 5 is a side view of the section of the buoyant actuator shown in Figure
4;
Figure 6 is a plan view of Figure 4, illustrating in particular the gate means
of the
buoyant actuator;
Figure 7 is a plan view of the gate means of the buoyant actuator illustrating
the
open condition thereof;
Figure 8 is a schematic perspective view of the section of the buoyant
actuator
with the gate means in the open condition thereof;
Figure 9 is a side view of the section of the buoyant actuator as shown in
Figure
8;
Figure 10 is a side view of the interior of the support structure;
Figure 11 is a schematic perspective view of the support structure;
Figure 12 Is a plan view of the support structure;
Figure 13 is a schematic perspective view of the apparatus being assembled;
Figure 14 is a sectional view of the buoyant actuator shown in Figure 2;
Figure 15 is a perspective view of a buoyant actuator according to a second
embodiment forming part of apparatus for harnessing ocean wave energy;
Figure 16 is a-schematic side view of the arrangement shown in Figure 15;
Figure 17 is. an underside plan view of the buoyant actuator according to the
second embodiment;
Figure 18 is side view of the buoyant actuator,
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-13-
Figure 19 is a view similar to Figure 18 but in section to reveal the internal
structure of the buoyant actuator;
Figure 20 is a perspective view of the buoyant actuator from the underside
thereof;
Figure 21 is further side view of the buoyant actuator;
Figure 22 is a further underside plan view of the buoyant actuator,
Figure 23 is a fragmentary perspective view of the buoyant actuator, depicting
the
upper row of panels forming the shell of the buoyant actuator,
Figure 24 is a side view of the arrangement shown in Figure 23;
Figure 25 is an exploded view of panels in the upper row;
Figure 26 is a cross-section of panels in the upper row;
Figure 27 is a fragmentary perspective view of the buoyant actuator, depicting
the
lower row of panels forming the shell;
Figure 28 is a side view of the arrangement shown in Figure 27;
Figure 29 is a side view of four interconnected panels in the shell;
Figure 30 is a cross-sectional view of the Interconnected panels depicted In
Figure
29;
Figure 31 is a schematic sectional view of two panels, illustrating in
particular the
joint therebetween;
Figure 32 is a further sectional view of two panels, illustrating in
particular the joint
therebetween;
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-14-
Figure 33 is an elevational view of one of the panels from the inner side
thereof;
Figure 34 is a view similar to Figure 33 but from the outer side thereof;
Figure 35 is perspective view of the panel viewed from above;
Figure 36 is a perspective view of the internal structure of the buoyant
actuator
viewed from the underside thereof;
Figure 37 is a plan view of the internal structure;
Figure 38 is a side view of the internal structure;
Figure 39 is a fragmentary perspective view of the internal structure;
Figure 40 is a plan view of the arrangement as shown in Figure 39;
Figure 41 is a side view of the arrangement as shown in Figure 39;
Figure 42 is a perspective view of a flap forming part of the buoyant
actuator;
Figure 43 is a plan view of the flap;
Figure 44 is a side view of the flap;
Figure 45 is an exploded perspective view of a magnet means used as part of a
magnetic coupling for each flap of the buoyant actuator;
Figure 46 is a schematic plan view of a variation of the magnetic means;
Figure 47 is a schematic side view of the arrangement shown In Figure 46;
Figure 48 Is a side view of a buoyant actuator according to a third
embodiment;
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-15-
Figure 49 is a side view of part of the internal structure of the buoyant
actuator of
Figure 48;
Figure 50 is a' schematic side view of a head portion of the internal
structure
shown in Figure 49;
Figure 51 is a schematic side view of a buoyant actuator according to a fourth
embodiment with the flaps shown in an open condition;
Figure 52 is a view similar to Figure 51, except that the flaps are shown in a
closed condition to establish a barrier;
Figure 53 is a fragmentary view of a buoyant actuator according to a fifth
embodiment, illustrating in particular a flap in a closed condition and in
engagement with a dampener means for dampening the closing action of the flap;
Figure 54 is a view similar to Figure 53, except that the flap is shown in a
condition in which it has swung away from the dampening means;
Figure 55 is also a view similar to Figure 53, except that the flap is shown
in its
return path and commencing contact with the dampener means; and
Figure 56 is a schematic plan view of a wave energy conversion system
incorporation buoyant actuators according to any of the previous embodiments.
Best Mode(s) for Carrying Out the Invention
The embodiments shown in the drawings are each directed to an energy release
buoyant actuator 10 for use in apparatus 11 for harnessing ocean wave energy.
Referring to Figure 1, the apparatus 11 is installed and operating in a body
of
seawater 12 having a water surface 13 and a seabed 14. The apparatus 11
includes a pump mechanism 15 anchored with respect to the seabed 14. The
buoyant actuator 10 is operably connected to the pump mechanism 15 and is
buoyantly suspended within the body of seawater 12 above the pump mechanism
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
16
15 but below the water surface 13 at a depth such that its upper surface is
typically a few metres below the neutral water line. Moreover, the combination
of
buoyant actuator 10 and the pump mechanism 15 to which it is operably
connected preferably defines a total length which in its minimum condition
(when
,the buoyant actuator is at the lowest point of its excursion) is appropriate
for
deployment in water depths preferably no less than ten metres and no greater
than one hundred metres. The buoyant actuator 10 is operatively connected to
the
pump mechanism 15 by way of a coupling 16 which includes a tether 17.
Referring now to Figures 2 to 6, the buoyant actuator 10 according to the
first
embodiment comprises a body 21 having a support structure 23 and a plurality
of
sections 25. Sections 25 surround the support structure 23 defining a chamber
24
of generally annular configuration having an outer chamber wall 26 and an
inner
chamber wall 28. The ends of the buoyant actuator 10 are open allowing
entrance of water into the chamber 24.
As shown in Figure 4, each section 25 comprises a frame 27 having an outer end
adapted for supporting a wall portion 29 and an inner end adapted for
attachment
to the support structure 23. The sides of each frame 27 are adapted to couple
to
each other as shown in Figure 13. The sections 25 define the chamber 24
surrounding the structure 23. Each section 25 is traversed by gate means 31.
The
gate means 31 are adapted to be confined within the buoyant actuator in the
open
and closed conditions. The purpose of which will become apparent later.
The frame 27 is a structure comprising steel struts. The wall portions 29 are
metal
sheets. Alternatively, frame 27 and wall portions 29 may be constructed from
other materials suitable to sustain the marine conditions.
Water flow through chamber 24 between the open ends thereof may be controlled
via the gate means 31 activated in response to a predetermined fluid pressure
differential imposed thereon between the hollow interior and the surrounding
body
of water in which the buoyant actuator 10 is immersed. The predetermined fluid
pressure differential arises from heaving motion imparted to the buoyant
actuator
when it is subjected to an aggressive sea state. In other arrangements, the
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-17-
movement of the buoyant actuator may be controlled by selective operation of
the
gate means 31 so as to stay within specific ranges of movement
The gate means 31 comprise a closure element configured as a flap 33 pivotally
connected to a side of the frame 27 via hinges 35 (see Figure 6). Hinges 35
are
attached to one side of flap 33. At an opposite side (the free end) of flap
33, a
latch mechanism 37 releasably maintains the flap 33 in the closed condition.
This
impedes water flow through the chamber 24. The latch mechanism 37 comprises
a releasable coupling 39 which in the illustrated arrangement comprises
magnetic
couplings 41 and a plate 43. The plate 43 is located at the opposite side of
frame
27. The magnetic couplings 41 are attracted to plate 43 so as to maintain the
flap
33 in the closed condition (see Figure 4 and 5). The magnetic coupling 41 may
comprise a plurality of magnets (see Figures 8 and 9) provided at a location
along
the free edge of the respective flap 33 and/or at corresponding locations
along
corresponding edges of frame 27. In this way, the flaps 33 will remain in
closed
conditions until the force against them is sufficient to overcome the magnetic
attraction, thus forcing the flaps 33 to release and swing.away from the
closed
condition to establish the opening (see Figures 7 to 8) and to allow the water
flow
though the body.
In this embodiment, the releasable coupling 39 is adapted to actuate to
release
the flap to allow it to move from the closed condition to the open condition
to
establish the opening In response to the adverse weather conditions.
The magnetic attractive force may be adjustable. The magnetic attractive force
may be adjusted to a particular wave motion varying any of. the number and
strength of the, magnets, and the separation of the magnets and the struts.
In another arrangement, the magnetic attractive force is adjusted from a
remote
location. In this case the magnetic attachment means may be, for example,
electromagnets with variable magnetic attractive force.
The flaps 33 may each be adapted to close under the influence of its own
weight
at specific water flow levels. Alternatively, each flap may be biased towards
its
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-18-
closed condition. This may be achieved by use of a spring mechanism, such.as
incorporation of a spring in the hinge for the flap.
In a further arrangement, the hinged flap is biased in the closed condition
via a
rubber spring mechanism attached to a free end of the at least one flap.
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
10.
As previously explained, the opening of flaps 33 allows water to pass through
the
chamber 24 so that there is minimal resistance to the moving water that
impinges
on the buoyant actuator. This removes much of the potential energy as the
buoyant actuator 10 is not being heaved up as much by the waves and it Is
lighter,
and it also reduces the kinetic energy at the same time because the mass is
reduced (water is no longer trapped) and the velocity is reduced (because the
buoyant actuator is no longer providing such reaction to the wave forces that
would cause it to accelerate). It is not possible to make the buoyant actuator
10
appear completely transparent to the water as there will always be some
coupling
between the two but it is expected that the storm, loads on the pumps 15 and
couplings 21 can be attenuated to acceptable levels using the gate means 31 so
there is not the need to engineer very massive (and expensive) structures to
resist
these large forces.
It is a feature of the buoyant actuator 10 that it is fault-tolerant to flap
failure. If
one flap 33 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 enough of a
flow
passage established for water to enter and then leave the hollow interior of
the
buoyant actuator 10 to an extent which would adversely affect its operation.
For
there to be flow that might adversely affect operation of the buoyant actuator
10
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.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-19-
In this respect, the confining of the gate means 31 within the buoyant
actuator is
particularly advantageous. The gate means 31 are protected from the external
sea environment and are not exposed to be vulnerable to damage in the event of
the buoyant actuator 10 being involved in a collision. This arrangement
permits
the use of mesh material to close the open ends of the buoyant actuator 10 to
prevent ingress of marine material into chamber 24. Also, methods for
inhibiting
growth of marine organisms may be employed. For example, coatings may be
applied to the surfaces of the gate means 31 to discourage formation of
colonies
of marine organisms.
The sections 25 described above form together with the support structure 23
the
buoyant actuator shown in Figures 2 and 3.
Referring to Figure 10, the support structure 23 comprises a central core 49
and a
frame 47 surrounding the central core 23. The frame 47 comprises three groups
of struts 51. First and second group of struts 51 extend outwardly at an angle
from
the core 40 defining each a conical space within the structure 23. The first
group
of struts 51 extends from a first end of the core 49 to the middle section of,
the
core 49; the second group extends from the middle of the central core 49 to
the
second end section of the core. The third group of struts (not visible) extend
radially outwardly from the first end of the core 49. In this arrangement the
struts
define a pentagonal prism. Alternatively, other shapes may be suitable. In the
arrangement shown in Figure 10, there are 10 struts 51 per group of struts, a
pair
corresponding to each side 54 of structure 23. Lugs 59 and 61 extend
longitudinally from each end of central core 49. Lugs 59, 61 may serve as
lifting
and support means during operation, transport and assembly of the buoyant
actuator 10.
Furthermore, frame 47 comprises a series of vertically aligned stubs 45
extending
along the periphery of frame 47 (see Figure 10 to 12). Between the series of
stubs
45 are located side panels 53. Side panels 53 define the facets of the support
structure and also the inner chamber wall 26. End panels 55, 57 are located at
ends of the frame 47. This arrangement defines a closed internal volume within
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-20-
structure 23 shown in Figure 12. The stubs 45 extend above side panels 53 so
as
to receive sections 25.
The arrangement described defines a void within the structure 23. Due to the
substantially hollow nature of the buoyant actuator 10, it is lightweight
compared
to known prior art floats. The void is filled with buoyant material to provide
overall
net buoyancy to the buoyant actuator 10. The buoyant material may be, for
example, air, bladders containing air, low density materials such as foams,
among
others. The foam may be a closed cell poured urethane foam, although other
suitable materials could be used.
The buoyancy provides additional uplift during the pumping stroke. A wave
exerts
almost as much upwards force as it does downwards force on the buoyant
actuator 10. As each pump 15 only acts in one direction the buoyancy inside
the
buoyant actuator 10 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 hydrodynamic properties of the buoyant actuator may be varied by
selectively
varying the buoyancy within the structure 23. The variation to the
buoyancy'may
comprise addition of buoyant material to, or extraction of buoyant material
from,
the structure 23. Also, in other arrangements the type of buoyant material may
be
varied.
In other arrangements, the hydrodynamic properties of the buoyant actuator may
be varied by selectively varying the outer shape of the buoyant actuator. This
may
be accomplished by attaching, for example, buoyant material to the outer
surface
of wall portions 29.
Suitable shapes may include spheres, frusto-spheres, squat inverted-cones,
frusto-cones or squat cylinders for the buoyant actuator with a single tether.
Other
shapes may, of course, also be suitable.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-21-
A spherical shape may be optimal because, owing to its symmetry, there is no
rotational coupling between the wave disturbance and the buoyant actuator,
thereby providing optimal conversion of heaving force to linear tension on the
tether.
The differences' in energy gathering performance between a sphere, a squat
cylinder and a squat inverted cone are not so great as to exclude these shapes
in
favour of spheres when other factors such as manufacturability and robustness
are also taken Into consideration. Hence there is a range of shapes that have
acceptable energy gathering performance and acceptable ratings in terms of
robustness.
Because of its modular construction, the buoyant actuator is capable of being
transported as separate elements and assembled near its final destination. The
arrangement is, in effect, a kit comprising the previously described support
structure 23 and the ten sections 25. As show in Figure 13, the buoyant
actuator
10 is formed by fastening sections 25 to stubs 45 of support structure 23 and
coupling neighbouring sections 25 with respect to each other. This operation
may
be performed while the support structure 23 is suspended vertically from lug
61
with help of, for example, a crane.
The assembled buoyant actuator 10 (see Figure 2) may be lifted via lug 61 for
deployment into the body of water. As previously explained, in operation the
buoyant actuator 10 is operatively connected to a pump mechanism 15 by way of
a coupling 16 which includes a tether 17. The tether 17 is fastened to lug 59
of
the buoyant actuator (see Figure 10).
The pump 15 is anchored within the body of water 12 and adapted to be
activated
by wave energy via buoyant actuator 10. Pump 15 is operably connected to a
buoyant actuator 10 according to the embodiment buoyantly suspended within the
body of seawater 12 above the pump 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, pump 15 is activated by movement of the 'buoyant actuator. 10 in
response to wave motion. The pump 15 may provide high pressure, working fluid
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-22-
(for example, water) to a closed loop system in which energy in the form of
the
high pressure fluid is exploited.
In operation, a wave impinging on 'the apparatus 10 causes uplift of the
buoyant
actuator 10. This uplift is transmitted through the tethers 17 to the pump 15
causing it to perform a pumping stroke. Once the wave has passed, the uplift
force applied to the buoyant actuator 10 diminishes and the buoyant actuator
descends under the weight of the various components connected thereto,
including the, pumping mechanism of pump 15, thereby causing the pump 15 to
perform an intake stroke. As the piston mechanism descends, it plunges into
water which has entered the intake chamber. As the piston mechanism
descends, water within the intake chamber flows into the piston chamber and
the
progressively expanding pumping chamber. An intake check valve allows entry of
the water. This charges the piston chamber and the discharge chamber in
readiness for the next pumping stroke which is performed upon uplift of the
buoyant actuator 10 In response to the next wave disturbance.
In the event of an aggressive sea state, typically adverse weather conditions
(such' as In storm conditions), the buoyancy actuator 10 can be subject to
extreme
forces which impart a heaving motion to the buoyant actuator 10. In such
conditions there is a need to preserve the buoyant actuator 10 against damage
and limit the heaving loads that it transmits to other components of the
apparatus
11. This is achieved by releasing the energy of the buoyant actuator 10
effectively rendering it inoperative, or at least limit the heaving forces
imposed on
It, by allowing water to flow through the buoyant actuator. This has the
effect of
rendering the buoyant actuator 10 transparent to the body of water in which it
is
immersed; that is, the buoyant actuator 10 responds less to the heaving motion
of
the water than it otherwise would. This outcome is achieved by opening of the
gate means 31. The gate means 31 opens in response to a predetermined fluid
pressure differential imposed thereon, thereby permitting water flow upwardly
through the buoyant actuator 10. The predetermined fluid pressure differential
arises from upward heaving motion Imparted to the buoyant actuator 10 when it
is
subjected to an aggressive sea state.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-23-
In other arrangements, the movement of the buoyant actuator may be controlled
by selective operation of the gate means 31 so as to stay within specific
ranges of
movement.
Referring now to Figures 15 to 45, there is shown a buoyant actuator 10
according to a second embodiment. As depicted in Figures 15 and 16, the
buoyant actuator 10 according to the second embodiment forms part of apparatus
11 installed and operating in a body of seawater 12 having a water surface and
a
seabed 14. The apparatus 11 Includes a pump mechanism 15 anchored with
respect to the seabed 14. The buoyant actuator 10 according to a third
embodiment is operably connected to the pump mechanism 15 and is buoyantly
suspended within the body of seawater 12 above the pump mechanism 15 but
below the water surface 13, as was the case with the buoyant actuator 10
according to the first embodiment. The buoyant actuator 10 is operatively
connected to the pump mechanism 15 by way of a coupling 16 which includes a
tether 17.
The buoyant actuator 10 according to the second embodiment comprises a body
101 of frusto-conical configuration having an upper end 103, a lower end 105
and
a side 107 extending between the two ends. With this arrangement, the side 107
is of convex shape and bulging at the middle.
The body 101 is hollow, and the upper end 103 and the lower end 105 each open
onto the hollow interior ,109 within the body. The hollow interior 109 defines
a
chamber 110 which incorporates a controlled flow path along which, when open,
water can flow through the body between the open upper end 103 and the open
lower end 105. The upper end 103 defines an upper portal 104 opening into the
chamber 110 and the lower end 105 defines a lower portal 106 opening Into the
chamber 110.
The body 101 comprises an inner structure 111 supporting a shell 113 which
defines the upper end 103, the lower end, 105 and the side 107 of the body.
The inner structure 111 is configured for attachment of the tether 17 thereto.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-24-
The buoyant actuator 10 is configured such that the centre of mass is below
the
centre of buoyancy. This provides some stability to the buoyant actuator when
operating in adverse sea conditions. In this embodiment, the relative
positioning
and construction of the inner structure 111 and the shell 113 achieves this
relationship between the centre of mass and the centre of buoyancy.
The inner structure 111 incorporates gate means 115 for controlling flow
through
the body 101 between the upper portal 104 at the open upper end 103 and the
lower portal 106 at the open lower end 105, as will be described In more
detail
later. The gate means 115 is operable in response to a predetermined fluid
pressure differential imposed thereon, as was the case with the first
embodiment,
thereby permitting water flow upwardly through the buoyant actuator 10. The
predetermined fluid pressure differential arises from upward heaving motion
imparted to the buoyant actuator 10 when it is.subjected to an aggressive sea
state.
The embodiment seeks to provide an arrangement which can achieve the largest
possible cross-sectional flow area through the upper and lower portals 104,
106 of
the body 101 for a given trapped water volume within the body, and the frusto-
conical configuration of the body is conducive to such an arrangement.
The shell 113 is of modular construction, comprising a plurality of sections
121
configured as panels 123 adapted to be connected together. In the arrangement
shown, the panels 123 are arranged in two rows, being an upper row 125 and a
lower row 127. The upper row 125 defines an upper edge 128 at the upper end
103 of the body 101 and the lower row 127 defines a lower edge 129 at the
lower
end 107. The upper and lower edges 128, 129 are rounded in cross-sectional
profile.
The upper edge 128 bounds the upper portal 104 and the lower edge 129 bounds
the lower portal 106.
The panels 123 are each of the same configuration so that any panel can be
located at any position within either row 125, 127'. This Is advantageous as
It
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-25-
facilitates cost-effective manufacture of the panels 123 and ready assembly of
the
panels 123 into the shell 113.
Each panel 123 is of generally rectangular construction, comprising a panel
body
131 having an outer face 133, an inner face 135 and four edges 137. The four
edges 137 comprise an outer edge 139, an inner edge 141 and two opposed side
edges 143, 145.
When a respective panel 123 is installed in the assembled shell 113, the outer
edge 139 of the panel defines either part of the upper edge 128 of the shell
113 or
lower edge 129 of the shell 113, according to whether the panel 123 Is located
In
the upper row 125 or lower row 127 of the assembled shell 113. The outer edge
139 is rounded to conform to the rounded profile of the upper and lower edges
128, 129 of the shell 113.
The two opposed side edges 143, 145 of each respective panel 123 are
configured for connection to the adjacent edges of neighboring panels 123 in
the
same' row of panels within the assembled shell 113. This can be seen with
reference to Figure 18 in which panel 123a is shown, together with its
neighboring
panels 123b and 123c. Figure 29 also shows the arrangement, but without panel
123. Panel 123a has opposed side edges 143a and 145a, with side edge 143a
connected to side edge 145b of panel 123b and side edge 145a connected to side
edge 143c of panel 123c.
More particularly, the side edges 143, 145 of each respective panel 123 are
configured for mating engagement with the corresponding side edges of adjacent
panels. In the arrangement shown, the side edges 143, 145 are configured to
provide half lap joints.147 between the panels 123. With this arrangement, the
side edge 143 of one panel and the corresponding side edge 145 of a
neighbouring panel can mate in overlapping relation. The mating side edges
143,
145 can be secured together' in any appropriate way, such as by mechanical'
fixing, chemical bonding or welding. In the arrangement shown, the connection
is
mechanical fixing using fasteners 149 such as bolts or rivets. Connection by
way
of mechanical fixing 'using removable fasteners can be advantageous as it
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
26 -
facilitates disassembly of the shell 113 should that be required later for
repair or
maintenance purposes.
The half, lap joints 147 are formed by a rebate 151 along each side edge 143,
145
to define a flange 153 and an adjacent recess 155. The flange 153 and recess
155 are configured for mating engagement. With such an arrangement, in the lap
joint 147 between two panels, the flange 153 on side edge 143 of the first
panel
123 locates in the corresponding recess 155 on side edge 145 of the second
panel, and the flange 153 on side edge 145 of the second panel 123 locates in
the
corresponding recess 155 on side edge 143 of the first panel.
The inner edge 141 of each respective panel 123 is configured for connection
to
the inner edge of neighboring panel 123 in the adjacent row of panels within
the
assembled shell 113. This can be seen with reference to Figures 18 and 29 in
which panel 123a in the upper row 125 is panel 123d in the lower row 127 are
shown, with their respective inner edges 141a and 141d being adjacent to each
other.
More particularly, the inner edge 141 of each respective panel 123 is
configured
for mating and interlocking engagement with- the inner edge 141 of the
neighboring panel 123 in the adjacent row of panels within the assembled shell
113. In the arrangement shown, the inner edge 141 is configured to provide a
plurality of half lap joints 161. In this embodiment, there are two half lap
joints
provided by each inner edge 141, but more than two are also.possible.
The two half lap joints 161 are formed by first and second rebates 163, 165
along
the inner edge 141 on opposite sides thereof. The first rebate 163 defines an
outer flange 167 and an adjacent inner recess 169. Similarly, the second
rebate
165 defines an Inner flange 171 and an adjacent outer recess 173. The outer
flange 167 and the outer recess 173 are contiguous, and the inner recess 169
and
the inner flange 171 are also contiguous.
The outer flange 167 and the inner recess 169 are configured for mating
engagement, and the inner flange 171 and the outer recess 173 are also
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-27-
configured for -mating engagement. With such an arrangement, in the lap joint
147 between two panels, the flange 153 on side edge 143 of the first panel 123
locates in the corresponding recess 155 on side edge 145 of the second panel,
and the flange 153 on side edge 145 of the second panel 123 locates in the
corresponding recess 155 on side edge 143 of the first panel.
In this embodiment, the mating engagement between the respective flanges 167,
171 and recesses 169, 173 which constitute the half lap joints 161 is a
friction fit
engagement, thereby providing a snap fit connection between the panels 123 at
their inner edges 141.
With this arrangement, the inner edge 141 of one panel and the corresponding
inner edge 141 of neighboring panel can mate in overlapping relation. The
mating
inner edges 141 can be secured together in any appropriate way, such as by
mechanical fixing, chemical bonding or welding. In the arrangement shown, the
connection is mechanical fixing using fasteners 175 such as bolts or rivets.
Connection by way of mechanical fixing using removable fasteners can be
advantageous as It facilitates disassembly of the shell 113 should that be
required
later for repair or maintenance purposes.
The shell 113 is of buoyant construction. For this purpose, each shell panel
123
is buoyant. This may be accomplished in any appropriate way, such as by
forming one or more voids within the panel or encapsulating buoyant material
such as foam within the panel. In this embodiment, the body 131 of each panel
123 is of hollow construction comprising a skin 181 having an outer skin
section
183 defining the outer face 133 and an inner skin section 185 defining the
inner
face 135. The outer and inner skin sections 183, 185 are in spaced apart
relation
to define a closed space 187 therebetween. An array of bridging elements 189
are formed Integrally with the outer and,inner skin sections 183, 185 and
extend
therebetween across the space 187 to provide reinforcement for the two skin
sections. In this embodiment, the space contains air but may contain any
appropriate buoyant matter including other gases or foam material.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-28-
One or more anchoring points 190 are provided on the exterior of the shell 113
to
facilitate movement of the buoyant actuator 10 once deployed in water.
Typically,
such movement would be performed as a towing action. The anchoring points
190 are connected to the inner structure 111 to provide a robust arrangement.
The inner structure 111 provides a central core 201 supporting the shell 113.
The
inner structure 111 comprises a central column 203 and a frame 205 mounted on
the central column 203. Typically, the central column 203 and the frame 205
are
constructed primarily of metal, which assists In ensuring that the centre of
mass of
the buoyant actuator 10 is below the centre of buoyancy.
The central column 203 comprises an upper section 206 and a lower section 207.
The upper section 206 comprises a central plate 208 surrounding the column 203
and mounting brackets 209 below the central plate 208.
The frame 205 comprises arms 210 extending radially from the upper section 206
of the central column 203 and struts 211 extending between the lower section
207
of the central column 203 and the radially outer ends of the arms 210. Each
arm
210 comprises a frame element 213 mounted at its radially inner end on one of
the mounting brackets 209. The radially outer end of each frame element 213 is
supported by a respective one of the struts 211.
The frame 205 includes mounts 215 to which the shell 213 can be attached. In
the arrangement illustrated, the mounts 215 comprise mounting brackets 217 at
the outer ends of the frame elements 213 onto which the shell 213 can be
bolted.
The frame 205 also Includes radial frame elements 218 extending between the
lower section of the central column 203 and the shell 213 to brace the shell
in
position on the inner structure 111, as best seen in Figure 20..
The radial arrangement of the arms 210 defines spaces 219 between the arms
which form part of the flow path through the body along which, when open,
water
can flow through the body between the upper portal 104 and the a lower portal
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-29-
106. The spaces 219 are of generally triangular configuration, with the apex
radially innermost.
The gate means 115 is operable to regulate flow of water through the body 101
between the upper portal 104 and the lower portal 106.
The gate means 115 comprises a plurality of closure elements configured as
flaps
221 adapted to cooperate with each other to provide a barrier 222 across the
flow
path through the body 101 between the upper portal 104 and the lower portal
106.
The barrier 222 need not necessarily block flow entirely through the body 101
but
rather simply impede that flow.
Each flap 221 is moveable into and out of a condition In which it cooperates
with
the other flaps to provide the barrier 222. When one or.more flaps 221 have
moved out of that condition,. the barrier 222 opens to permit fluid flow
therethrough. In effect, the flaps 221 are configured as hatches which can
open
and close, and when in the closed condition provide the barrier 222. When in
the
open condition the hatches each provide an opening within the barrier through
which water can flow.
In the arrangement shown, the flaps 221 are each associated with a respective
one of the spaces 219 for opening and closing the space with respect to flow.
The flaps 221 are configured to conform to the shape of the spaces 219.' In
the
arrangement shown, each flap 221 comprises an inner end 223, an outer end 225
and two opposed sides 227. The configuration of the flap 221 is best seen in
Figures 42, 43 and 44. ' The sides 227 comprise an inner side section 227a and
an outer side section 227b. The sides 227 are configured such that inner side
sections 227a of adjacent flaps 221 locate closely adjacent each other, as can
be
seen in Figure 40 when the flaps are in the closed condition. This facilitates
attainment of an effective barrier 222.
The flaps 221 are pivotally mounted on the frame 205 for swinging movement
between open and closed conditions in relation to the respective spaces 219.
In
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-30-
the closed condition, the flaps 221 extend across the spaces 219 to thereby
establish the barrier 222 and obstruct flow. Because of its pivotal mounting,
each
flap 221 can swing away from its respective space 219 to expose the space and
thereby open the barrier 222 to flow threrethrough. The flaps 221 are shown in
the closed condition in Figures.36, 37 and 39. Figure 19 shows the flaps 221
partly swung away from the closed condition.
In the arrangement shown, each flap 221 is pivotally mounted on the frame 205
adjacent the outer end 225 thereof by means of hinges 229. When the flap 221
is
In the closed condition, the inner end 223 is supported on the central plate
208.
The barrier 222 is so configured and positioned to be within the confines of
the
shell 113. Further the flaps 221 which constitute the barrier 222 remain
within the
confines of the shell 113 even when in the fully open condition.
A latch mechanism 231 is associated with each flap 221 to retain the flap in
the
closed condition to Impede water flow through the body 101. The latch
mechanism 231 comprises a releasable coupling 238 which in this embodiment
comprises magnetic coupling 239. The magnetic coupling 239 provides an
attractive force between the inner end 223 of each flap 221 and an adjacent
part
of the central core 201. In the illustrated arrangement, the magnetic coupling
239
comprises a magnet means 241 on the flap 221 adjacent the Inner end 223
thereof and a striker plate 243 on the central column 203. The striker plate
243 is
of material (such as steel or other ferromagnetic material) to which the
magnet
means 241 is magnetically attracted and, in the arrangement illustrated, is
defined
by the central plate 208 of the central column 203.
The magnetic coupling 239 is operable to retain the respective flap 221 in the
closed condition until the force against the flap Is sufficient to overcome
the
magnetic attraction, thus forcing the magnetic coupling to release the flap
and
swing away from the closed condition to establish an opening to allow the
water
flow though the body 101.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-31-
The magnet means 241 in this embodiment comprises an array of permanent
magnets 245 accommodated within a housing 247. The permanent magnets 245
may be of any appropriate type. Permanent magnets having good aging
characteristics are desirable. Neodymium magnets (also known as NdFeB
magnets) are believed to be particularly suitable.
The housing 247 is adapted to isolate the magnets 245 from the water
environment in which the buoyant actuator is intended to operate.
Under certain combinations of hydrodynamic conditions and motion of the
buoyant actuator 10 in the moving body of water, it Is possible for the flaps
221 to
close with excessive. force, in effect being slammed shut rather than closing
gently. If this condition is not mitigated it can lead to excessive wear of,
and
damage to, the flaps 221 themselves, as well as to the latch mechanisms 231
and
other parts of the inner structure 111. In order to mitigate this problem some
form
of physical dampener may be provided between the contacting surfaces. This
dampener may take the form of shaped pieces of elastomeric material with
appropriate energy damping properties, attached to either or both contacting
surfaces; for example, the elastomeric material can be attached to each flap
221
or the mating part of the inner structure 11 such as the striker plate 243, or
both.
Other dampening arrangements are, of course, possible; for example, the
swinging motion of the flaps 221 could be dampened hydraulically or by way of
electrical (eddy current) damping control. Indeed, it may be advantageous to
provide both elastomeric damping on contacting surfaces, and dampening of the
swinging motion by hydraulic or electrical (eddy current) means.
In Figures 46 and 47 of the drawings there is shown a variation of the magnet
means 241 devised to provide protection for the permanent magnets 245 and also
afford some physical dampening when contacting the striker plate 243. In this
variation, the housing 247 comprises non-magnetic, non-porous material (such
as
a plastic polymer) in which the permanent magnets 245 are encased. Preferably,
the plastic polymer material would have some resilient properties to offer
some
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-32-
physical dampening. It is believed that polyurethane, acrylic and polymer HMPE
would be particularly suitable plastic polymers for the housing 247.
Typically, the permanent magnets 245 would be molded into the housing 247.
Such an arrangement is advantageous as it also confines the permanent magnets
245 and retains them in position within the housing and also in position
relative to
each other.
The housing 247 presents a contact face 251 to confront the striker plate 253.
In
the arrangement shown, the permanent magnets 245 are recessed with respect to
the contact face 251 to provide the housing with a cushioning portion 253
between the contact face 251 and the permanent magnets 245. The contact face
251 also functions as a wear surface, protecting the recessed permanent
magnets
245 from the effects of wear upon contact between the magnet means 241 and
the striker plate 253.
Typically, the housing 247 is removable and replaceable, as necessary.
In this embodiment, the cushioning portion 253 is integral with the housing
247.
In another arrangement, the cushioning may be provided by a layer of
cushioning
material applied to the housing 247 for contact with the striker plate 253.
Although not shown, cushioning can also be provided in relation to the striker
plate 243. By way of example, the striker plate 243 may be supported on a
shock-absorbing mounting arrangement. The shock-absorbing mounting
arrangement may comprise rubber mounts on which the striker plate 243 is
elastically supported.
In this second embodiment, the barrier 222 provided by the flaps 221 extends
across the chamber 110 to be substantially normal to the direction of flow of
water
through the body 101 between the upper portal 104 and the lower portal 106.
Typically, the flaps 221 can swing through an arc of movement of about 90
degrees in moving between the fully closed and fully open conditions. With
such a
range of movement, the flaps may be susceptible to closing with excessive
force
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-33-
under certain combinations of hydrodynamic conditions and motion of the
buoyant
actuator 10 in the moving body of water. As alluded to above, the provision of
dampening seeks to alleviating this potential problem.
Another approach to alleviating the problem of closing of the flaps 221 with
excessive force is to reduce the range of movement of the flaps between the
fully
closed and fully open conditions and thereby reduce the extent to which the
flaps
are susceptible to combinations of hydrodynamic conditions and motion of the
buoyant actuator 10 in the moving body of water when they are out of the
closed
condition.
The buoyant actuator. 10 according to the third embodiment, which is shown in
Figures 48, 49 and 50, adopts such an approach.
The buoyant actuator 10 according to the third embodiment is similar in many
respects to the buoyant actuator according to the third embodiment and similar
reverence numerals are used to identify similar parts.
In the buoyant actuator 10 according to the third embodiment, the barrier 222
is of
raked construction such that each flap 221 when in the closed condition is
inclined
to the direction of flow of water through the body 101 between the upper
portal
104 and the lower portal 106. Specifically, each flap 221 is inclined in the
direction towards the upper portal 104; that is, the inner end 223 of each
flap 221
is closer to the upper portal 104 than the outer end 225 when in the closed
condition, as shown in Figure 48. In this way, the range of movement of the
flaps
between the fully closed and fully open conditions is reduced.
With this arrangement, the flaps 221 when in the closed condition provide the
barrier 222 with the raked and somewhat conical configuration.
The inner structure 111 comprising the central column 203 and the frame 205 is
modified to accommodate this arrangement. In particular, the arms 210 which
define the spaces 219 therebetween are raked. Additionally, the central column
203 incorporates a head portion 261 which supports the inner ends 223 of the
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-34-
flaps 221 when in the dosed condition and also provides the striker plates 243
for
the magnetic couplings 239 which function as the latch mechanisms 231.
Specifically, the head portion 261 comprises a plurality of segments 263 each
of
which defines a respective one of the striker plates 243-
The frame 205 comprises a spider structure 271 comprising raked upper frame
elements 273 and raked lower frame elements 275 which converge at their outer
ends to mounting plates 277 onto which the shell 113 can be mounted. With this
arrangement, the upper frame elements 273 define the arms 210 and the spaces
219 therebetween.
Referring now to Figures 51 and 52 there is shown schematically a buoyant
actuator 10 according to a fourth embodiment. The buoyant actuator comprises a
body 301 which is hollow and which has, an upper end 303 and the lower end 305
each opening onto the hollow interior 307 within the body. The hollow interior
307
defines a chamber 309 which incorporates a controlled flow path along which,
16 when open, water can-flow through the body between the open upper end 303
and the open lower end 305. A gate means 311 is provided for controlling flow
through the body 301 between the open upper end 303 and the open lower end
305. As with earlier embodiments, the gate means 311 is operable in response
to
a predetermined fluid. pressure differential imposed thereon. The
predetermined
fluid pressure differential arises from heaving motion imparted to the buoyant
actuator 10 when it is subjected to an aggressive sea state.
The gate means 311 comprises a plurality of flaps 313 configured to cooperate
with each other to provide a barrier 315 across the flow path through the body
301
between the open upper end 303 and the open lower end 305. The barrier .315
need not necessarily block flow entirely through the body 301 but rather
simply
impede that flow.
Each flap 313 is moveable into and out of a condition in which it cooperates
with
the other flaps to provide the barrier 315. When one or more flaps 313 have
moved out of that condition, the, barrier 315 opens to permit fluid flow
therethrough. As with earlier embodiments, the flaps 313 are configured as
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-35-
hatches which can open and close, and when in the closed condition provide the
barrier 315. When in the open condition the hatches each provide an opening
within the barrier 315 through which water can flow.
In this embodiment, the flaps 313 are pivotally mounted for swinging movement
between the open and closed conditions. In the arrangement illustrated the
flaps
313 are pivotally mounted on pivots 317 defined by hinges 319 mounted on the
body 301. The flaps 313 are operably connected to buoyant devices 321 which
bias the flaps 313 into the closed condition. The buoyant devices 321 are
disposed exteriorly of the body 301 in the arrangement illustrated. A stop 323
Is
associated with each buoyant device 321 to limit upward movement of the device
under the influence of buoyancy. Upon upward swinging movement of the flaps .
313 from the closed condition (as shown in Figure 52) to the open condition
(as
shown in Figure 51) in response to a differential pressure imposed thereon,
the
buoyant devices 321 move downwardly away from the stops 323 against the
influence of buoyant forces imposed on them. When the differential pressure on
the flaps 313 reduces to a sufficient extent, the buoyant forces imposed on
the
buoyant device 321 return the latter into engagement with the stops 323,
thereby
returning the flaps 313 to the closed condition.
In this embodiment the flaps 313 are supported within the chamber 309 In a
cantilever fashion; that is, the flaps 313 extend in an unsupported manner
into the
chamber 309 from the hinges 319. With this arrangement, the flaps 313 can be
constructed to incorporate some inherent flexibility, thereby allowing the
flaps to
deflect a limited extent when in the closed condition' In response to downward
hydrodynamic forces (as depicted in broken lines in Figure 52).. This may be
advantageous as flexing of the flaps 313 can provide some cushioning in the
closing action of the flaps.
As mentioned above in relation to several embodiments of the buoyant actuator
10, there Is a' possibility under certain combinations of hydrodynamic
conditions
and motion of the buoyant actuator 10 for the flaps which constitute the
barrier to
close with excessive force, in effect being slammed shut rather than closing
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-36-
gently. Several dampening arrangements have been disclosed, including
reference to dampening by hydraulic means.
Referring now to Figures 53, 54 and 55, there is shown schematically a portion
of
a buoyant actuator 10 according to a fifth embodiment. The buoyant actuator 10
according to this embodiment comprises a gate means 351 comprises a plurality
of flaps 353 (only one of which is shown) configured to cooperate with each
other
to provide a barrier across the flow path, as was the case with earlier
embodiments.
The buoyant actuator 10 according to this embodiment further comprises a
hydraulic dampener. 355 adapted to facilitate closure of each flap 353 in a
cushioned manner. The hydraulic dampener 355 comprises a dashpot 357
having a cylinder 359 and a piston 361. The piston 361 comprises a piston head
363 and a piston shaft 365. The piston head 363 is accommodated in the
cylinder
359 to divide the cylinder into two chambers 367, 369. Chamber 367 is opposed
to the piston shaft 365 and includes a spring 371 adapted to bias the piston
361
into an extended condition. The chamber 367 also includes porting 373 for
controlled intake and expulsion of fluid, which in this embodiment is
typically water
from the surrounding seawater environment. The free end of the piston shaft
365
is fitted with a resilient bumper 375 for contact with the respective flap
353.
When the flap 353 is in the closed condition (as depicted in Figure 53), the
bumper 375 Is in contact with the flap 353, the piston 361 is in the retracted
condition within the cylinder 359 and the spring 371 is compressed. Upon
movement of the flap 353 out of the closed condition (as depicted in Figure
54),
the flap 353 separates from the bumper 375, allowing the piston 361 to extend
under the influence of the compressed spring 371. Extension of the piston
causes
progressive expansion of the chamber 367 which in turn causes water to be
drawn into the chamber 367 through the porting 373. Upon return movement of
the flap 353 (as depicted in Figure 55), the flap 353 first engages the bumper
375
which affords some initial cushioning by virtue of its resilient nature.
Continued
30. return movement of the flap 353 applies force to the piston 361, causing
it to
retract. Retraction of the piston 361 causes progressive contraction of the
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-37-
chamber 367 which in turn causes expulsion of water from the chamber 367
through the porting 373. The porting 373 is sized to regulate the rate of
expulsion
of the water from the chamber 367 and thereby provides a viscous damping
effect. Accordingly, the flap 353 completes its closing action in a controlled
manner and without excessive force.
Referrring now to Figure 56, a sixth embodiment of the invention relates to a
wave
energy conversion system 400 comprising a plurality of units 401 each being
one
of the apparatus according to the previous embodiments and each having a
buoyant actuator 10. With such an arrangement, the respective buoyant
actuators 10 are disposed in an array 403 of buoyant actuators. Any number of
buoyant actuators 10 can be provided in the array.
The spacing between units 401 and the patterning of the array 403 are features
that are optimised with respect to the actual wavelength of the dominant sea
state
and the directions of the waves.
The apparatus according to each embodiment may operate in conjunction with the
closed loop system (not shown) in which energy in the form of the high
pressure
working fluid is exploited for use, for example, in power generation or a
desalination plant.
From the foregoing, it is evident that each of the embodiments provides an
energy
release buoyant actuator which is relatively lightweight, and which can be
rendered effectively Inoperative In adverse conditions for preservation.
Further, It should be appreciated that the scope of the invention is not
limited to
the scope of the embodiments disclosed.
While the embodiments described are each of modular construction, it should be
understood that the buoyant actuator in accordance with the invention can be
constructed as a single unit and transported to site In that condition.
CA 02758989 2011-10-07
WO 2010/115241 PCT/AU2010/000398
-38-
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.
