WAVE ENERGY CONVERTER

CONVERTISSEUR DE L'ENERGIE DES VAGUES

English Abstract

A wave energy conversion device uses a float
member and a support structure for having a water move
the float in a vertical direction due to water movement
in combination with a lock function for temporarily
maintaining the float member in the raised position. The
float member is released to fall by gravity into a wave
trough. Power extraction is removes energy during the
fall of the flat member.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A wave energy extraction system comprising
a float member arranged in a body of water to rise with
upward movement caused by the motion of the water;
a support structure secured to a base and providing
vertical support and temporary locking of said float
member in a raised position without the support of the
water;
a release arrangement for releasing the temporary
locking of said float member to allow said float to fall
by gravity into said water disposed at a lower position;
and
an energy extraction arrangement for extracting
energy during the fall of said float member.
2. A wave energy extraction arrangement as claimed in
claim 1 wherein said support structure includes at least
two vertical support members in engagement with a bottom
of said body of water.
3. A wave energy extraction arrangement as claimed in
claim 1 or 2 wherein said support structure includes
three vertical support members disposed in a triangular
configuration with each support member being positioned
interior to a peripheral edge of said float member.
4. A wave energy extraction arrangement as claimed in
claim 1, 2 or 3 including a ballast tank associated with
said float member that at least partially fills with
water when said float member is floating on said water
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and includes means to automatically retain the water when
supported in said raised position.
5. A wave energy extraction arrangement as claimed in
claim 4 wherein said means to automatically retain the
water is a check valve arrangement.
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Description

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TITLE: WAVE ENERGY CONVERTER
FIELD OF THE INVENTION
The present invention relates to wave energy
conversion systems and in particular relates to a
distributed system having a series of conversion devices
that cooperate and energy is extracted and accumulated in
a group manner.
BACKGROUND OF THE INVENTION
It has long been recognized that waves contain a
significant amount of energy and this energy is
essentially dissipated once the waves reach shore. A
number of wave conversion systems have been proposed
based on the displacement of buoyant bodies. For wave
conversion systems to be practical, the energy needs to
be extracted in a reasonable manner and the cost of
building and maintaining the system should not be
excessive. Typically the energy extraction system is
offshore but at a point where the depth of the water has
caused the height of the wave to significantly increase
to thereby cause a significant displacement of the
buoyant body.
SUMMARY OF THE INVENTION
A wave energy extraction system according to the
present invention comprises a float member arranged in a
body of water to rise with upward movement caused by the
motion of the water. A support structure is secured to a
support base submerged in the water and provides vertical
support and temporary locking of said float member in a
raised position without the support of the water. A
release arrangement acts to release the temporary locking

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of the float member to allow the float to fall by gravity
into the water disposed at a lower position. An energy
extraction arrangement extracts energy during the fall of
the float member.
In an aspect of the invention the support
structure includes at least two vertical support members
supported by a bottom of the body of water.
In yet a further aspect of the support structure
includes three vertical support members disposed in a
triangular configuration with each support member
positioned interior to a peripheral edge of the float
member.
In a further aspect of the invention the wave
energy extraction arrangement includes a ballast tank
associated with the float member that at least partially
fills with water when the float member is floating on the
water and includes means to automatically retain the
water when supported in the raised position. Preferably
the means to automatically retain the water is a check
valve arrangement.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown
in the drawings wherein:
Figure 1 is a schematic view of the energy
extraction arrangement;
Figure 2 is a side view of the energy extraction
arrangement with a float lifted to a raised position;
Figure 3 is a view similar to Figure 2 with the
raised float temporarily locked on the support;
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Figure 4 shows release of the float for energy
extraction;
Figure 5 schematically illustrates one arrangement
for energy extraction that includes raising of a weight;
Figure 6 is a view similar to Figure 5 with the
weight allowing a cable to pass therethrough;
Figure 7 is a partial schematic view showing a
series of energy extraction devices;
Figure 8 is a partial schematic view showing one
arrangement for the engagement and release of the weight;
Figure 9 is a schematic view of an alternate three
support energy extraction arrangement; and
Figures 10 and 11 are schematic views showing a
variation of the system that includes the filling and
release of a ballast chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An energy extraction arrangement is generally
shown as 2 in Figure 1 and includes a vertical member 4
that is rigidly secured to the bottom support layer 6.
The vertical member 4 includes a relatively heavy float
member 8 that moves upwardly on the vertical member 4 as
the crest of the wave passes the vertical member. As can
be appreciated the float 8 achieves the maximum vertical
displacement generally when the crest 10 of the wave
passes beneath the float. This arrangement is shown in
Figure 2 where the crest 10 is immediately below and
supports the float 8.
The exact height of the float 8 on the crest 10
will be determined by the effective buoyancy of the float
8 and the size of the supporting wave.
Figure 3 illustrates the significant difference
between the proposed structure as discussed herein and
the prior art. In contrast to the typical approach where
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the float member 8 is continuously supported by the wave,
the present structure effectively allows the float member
8 to move upwardly on the vertical member 4 as the crest
of a wave passes beneath the float. The float member
5 8 is then maintained at this vertical position on the
post and supported by the post. The float member 8 is
essentially maintained in a raised position on the
vertical member 4 until such time as the trough 12 is
generally below or about to be below the vertical member
10 4. At this time, it is desired to effectively release
the float member 8 and allow it to move downwardly into
the trough of the wave and effectively bottom out in the
bottom of the trough 12. This position is shown in
Figure 4. The exact timing preferably maximizes the
displacement so the float member bottoms out in the
trough.
In order to extract energy during movement of the
float 8 downwardly, a mechanism is required to
effectively change the potential energy of the float
member 8 and the subsequent kinetic energy of the float
member 8 as it moves downwardly into the trough 12. Such
an extraction arrangement is shown in Figure 5. The
vertical member 4 has been provided with a counterweight
20 that moves upwardly on the vertical member 4 as the
float 8 passes downwardly along the length of the
vertical member into the trough 12.
The float member 8 includes a cable 22 attached to
the float at position 24 and the cable 22 passes over
pulleys 26 and 28. These pulleys guide the cable 22 to
the counterweight 20. The counterweight 20 includes a
passage 30 extending therethrough such that the cable 22
is able to freely pass through the counterweight. The
cable 22 also includes a biasing weight 34 at the end
thereof. As shown in Figure 5 the movement of the float
member 8 downwardly into the trough 12 from its fixed
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position corresponding to the height of the crest 10 has
caused the counterweight 20 to move from the position
shown as 23 to position 25 shown in Figure 5. In the
embodiment shown this is a one to one relationship and as
such the counterweight 20 is somewhat lighter than the
float member 8 to thereby cause the float to pull the
counterweight up as it is released as the trough 12
passes therebelow.
As shown in Figure 6, the next crest l0a has now
moved towards the float member 8 and caused an increase
in the vertical position thereof. This has caused the
cable 22 to pass over the pullies 26 and 28 and the
further weight 34 has moved downwardly towards the float
member 8. The counterweight 20 is maintained at its
raised position on the post typically by a one way clutch
type arrangement or other suitable locking arrangement.
As the crest l0a moves beneath the float member 8 any
slack in the cable 22 is taken up due to the
gravitational force of the additional weight 34. As can
be appreciated, when the next trough 12a is beneath the
raised float member 8, the float member 8 is released (as
would be the case in Figure 3) to move downwardly and
into the trough 12a and essentially forms the power
stroke. This downward movement of the float member 8
causes the cable 22 to pull the counterweight 20 to a
further raised position on the post. At a different
point the counterweight 20 will be allowed to move
downwardly on the vertical member 4 and will drive a
suitable power extraction mechanism. This may involve a
rotating member or a gas pressurizing arrangement, or
other arrangements to convert the potential energy of the
counterweight 20 into a desired power output.
Figure 8 shows a simple ratchet arrangement 40
provided on the counterweight 20 that pivots outwardly as
shown in the dashed lines of Figure 8 when there is a
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release of tension in the cable 22. The ratchet 40 moves
to the locked position of Figure 8 once movement of the
cable 22 in a downward direction is stopped. Any
movement of the cable vertically as will occur when the
float member 8 moves downwardly into a trough causes the
ratchet 40 to move to the locked position and thus the
counterweight 20 is moved upwardly and accumulates
energy.
Figure 7 shows a series of these wave energy
extraction devices 2 where the extraction devices 2 are
spaced at different distances from shore and some of
these devices will experience a particular wave or set of
waves before the wave moves past the devices that are
closer to shore. One aspect of this distribution
arrangement is to have a series of these extraction
devices which are essentially leading devices such that
the leading devices can be of assistance in computing the
period or frequency of the waves. This is important in
the present arrangement as it is desired to release the
lock on the float member 8 when a trough is effectively
passing by or about to pass by the vertical member. In
this way the float member 8 can be released and move
downwardly into the bottom of the trough and thereby
achieve the maximum stroke of the system. By spacing the
devices at different positions in the direction of wave
movement the lead devices can provide frequency or period
information or the devices can cooperate to allow the
calculation of the period or frequency in a relatively
precise manner. It can also be appreciated that the
average vertical movement of the float member 8 can be
monitored as well as the effective time for a full cycle.
This provides similar information and will allow for
timing of the release of the float members such that an
effective stroke length is realized. Other arrangements
for calculating the timing of the release of the float
member 8 can also be used.
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The present system effectively shows a 1 to 1 type
relationship between the float member 8 and the
counterweight 20. It is also possible to use a heavier
counterweight and an appropriate gear train arrangement
or ratio arrangement such that the counterweight can be
heavier and the distance that the counterweight is raised
generally decreased by this ratio. In this way there may
be some loss in the possible potential energy that can be
extracted by the counterweight 20 due to the release in
movement of the float member 8 downwardly on the vertical
member. As can be appreciated the counterweight cannot
be exerting a force greater than the gravitational force
on the float member 8 as the member would not move
downwardly when released. Thus there will be an
effective balance or determination between the necessary
efficiency rate regarding the extraction of energy and
accumulating that energy as potential energy in the
counterweight's position on the vertical member 4.
From the above it can be appreciated that the
energy conversion either as potential energy in a
counterweight or in a suitable compression stroke due to
movement of the float member 8 can be accomplished in a
shorter period of time where the maximum velocity of the
buoyant member is higher than would be the case if the
buoyant member merely was allowed to rise and fall with
the crests and troughs of the wave. It is believed this
arrangement of locking and releasing of the buoyant
member is more effective in both the accumulation and the
extraction of energy.
In Figure 9 a three post system 100 is shown with
a triangular float 108. As can be appreciated this
support arrangement has increased stability and can
include an upper platform wall above the float 108 to
support a power extraction arrangement (not shown).
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A further embodiment of the invention is shown in
Figures 10 and 11 where a modified float 8a is supported
between two posts. The float 8a includes a funnel shape
bottom 50 with a one way check valve 15. The funnel
shaped bottom 50 is flooded when the float is supported
on the wave as shown in Figure 10 and the check valve 15
is open. Therefore the buoyancy level of the float is
essentially fixed and not affected by the water in the
funnel. Once the float is locked and the wave starts to
dissipate as shown in Figure 11 due to the crest moving
through, the check valve closes and thus the mass and
weight of the float is increased by the captured water.
Therefore the weight of the float is increased for the
downward power stroke. The float, upon bottoming out in
the trough, removes the weight of the water as the check
valve opens. This funnel concept or water
capture/release concept can also be used between floats
on separate columns to increase the weight of the
captured water or on single floats with a single vertical
support.
In the embodiment of Figures 10 and 11 it is also
possible to provide a series of outlet ports or check
valves generally at a top region of the funnel. These
ports or check valves allow displacement of water when
the bottom check valve opens as it impacts the water at
the bottom of the power stroke. They can also assist in
filling. With this arrangement it may not be necessary
to include the check valve.
The arrangement of Figures 10 and 11 have been
described with a two post system, however the three post
system of Figure 9 is also a practical alternative.
Furthermore one funnel and one check valve have been
shown for illustrative purpose only. More funnels and
check valves per float can be used and may be preferred
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for efficiency and reliability. Multiple post systems
may be preferred in the working load for the support
becomes too high or to increase structural integrity.
The present system has been described with respect
to a float member moving and locking on a vertical member
and then being released but other arrangements are
possible. For example a float suspended from a cable
trained over a column member could also be used to lock
and release such a cable to rotate a shaft as part of the
power extraction or could raise a weight or otherwise
accumulate power.
Although various preferred embodiments of the
present invention have been described herein in detail,
it will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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Representative Drawing