GB2456833A

GB2456833A - Tilting wave energy device

Info

Publication number: GB2456833A
Application number: GB0801503A
Authority: GB
Inventors: Adam Zakheos
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-01-28
Filing date: 2008-01-28
Publication date: 2009-07-29
Anticipated expiration: 2028-01-28
Also published as: GB0801503D0; GB2456833B; WO2009095651A1

Abstract

A wave energy generating apparatus 10 comprises a buoyant vessel 12 which rocks about one or more horizontal axes under wave action. The vessel 12 holds a body of water 14 which remains substantially level under the action of gravity despite movement of the vessel 12. The apparatus has means to extract energy from this relative movement. There may be a float 16 on top of the water, and energy may be extracted by hydraulic cylinders 126. Alternatively, the chamber may comprise an annulus which is divided into sections connected at the bottom, so that displacement of the water due to tilting of the vessel causes air in some of the sections to be pressurized (figures 3 and 4).

Description

METHOD AND APPARATUS FOR GENERATING ENERGY FROM WAVES

The present invention relates to an apparatus for generating energy from waves and to a method of such generation. The invention find particular, but not exclusive, use in marine environments, especially coastal locations, where the energy generated may be provided directly to a power network or grid.

Apparatus for the generation of energy from the movement of water, in particular the generation of so-called wave energy', are well known in the art and have many forms. In general, a significant number of the known systems operate on one of two principles. The first principle of operation is the use of movement of the water itself to drive an energy generating device, either directly or indirectly. A second principle of operation is the generation of energy by the movement of a first floating device relative to second, typically relatively fixed, device.

Thus, for example, it is known to mount a turbine assembly at or close to the shoreline in communication with a conduit. Waves are allowed to enter the conduit under their normal action. The turbine may be driven directly by movement of the water within the conduit, under the action of the waves, or indirectly by having the wave move air within the conduit and allowing the moving air to drive the turbine.

WO 01/65112 discloses an apparatus for deriving energy from waves and * *. having a chamber adapted to float in water. The chamber has a water plane area of * 25 such form that the vertical oscillating movement of the chamber is substantially **.* S ** damped, relative to the height of the waves in the water. The chamber has an inlet port through which waves are allowed to enter the chamber. The chamber is S.....

provided with a baffle and vertical side plates. In operation, air is compressed under S..

* the action of a wave entering the chamber through the inlet and is forced out through a manifold to an outlet port, where it is used to provide a source of energy. S. *S *. S

* An alternative approach is disclosed in WO 2007/141363. A device for harnessing wave energy is disclosed and comprises a plurality of converging floating hulls, between which waves are caused to pass. As the wave passes between the hulls, the convergence causes the height of the wave to increase until water spills over the side of the hull and enters a plurality of stepped tanks. Water in the tanks is used to drive turbines.

WO 2006/10904 discloses an apparatus having one or more floats, which are allowed to move under the action of passing waves. Vertical movement of each float is used to generate power. The floats are retained by flexible restraints to limit lateral movement of the floats.

A wave energy converter is disclosed in WO 2007/137426 and has a primary body connected to a second body in a manner allowing relative longitudinal movement between the bodies. The movement of the bodies is damped by a so-called slug mass' and can be controlled to maintain out of phase oscillation of the bodies, thereby increasing the driving force imparted to a power generating device.

A floating apparatus for extracting power from sea waves is disclosed in US 6,476,511. A development of the apparatus is described and shown in US 2006/0273593. The apparatus comprises a number of buoyant cylindrical members connected together at their ends to form an articulated chain-like structure. Relative movement of adjacent members is permitted about at least one transverse axis.

Adjacent members are coupled together by a system comprising one or more hydraulic rams which resist movement between the members and extract power from their relative movement. The axis of permitted movement is arranged according to a * *. roll bias angle to optimise the dynamic response of the apparatus to incoming waves.

The roll bias angle is applied by differential ballasting of the body members and/or mooring constraints attached to one of more members. *

S.....

* An improved assembly for generating energy from waves has now been devised. The assembly comprises a first body or vessel that has a normally vertical : ..30 orientation and is free to move about an axis other than a vertical axis under the action of a wave. The assembly comprises a second body moveabte with respect to but retained by the first body in a manner that allows the second body to be biased to a first position under the action of gravity. The second body is held in its first position by the bias, as the first body is rotated from its normally vertical orientation.

Alternatively, the second body is moved to a second position by the first body as it is moved from its normally vertical orientation under the action of a wave. Once displaced from its first position, the second body returns under gravity to its first position, again moving relative to the first body. Movement of the second body relative to the first body is used to generate energy.

Accordingly, in a first aspect, the present invention provides an apparatus for generating energy from waves, the apparatus comprising: a buoyant vessel having a normally vertical orientation and able to be displaced from the normally vertical orientation by rotation about an axis other than a vertical axis by the motion of a wave; a body retained by the vessel but moveable with respect to the vessel, the body having a first position corresponding to the normally vertical orientation of the vessel to which it is biased under gravity, the body being moveable relative to the first vessel to stay in or return to the first position when the vessel is displaced from the normally vertical orientation; and means for generating energy coupled to generate energy by the relative movement between the vessel and the body.

The apparatus comprises a vessel that is normally buoyant and may be acted upon by waves passing the vessel. The vessel typically floats at or close to the surface of the water, where it may encounter waves propagating through the water and subjected to the action of the waves. The vessel has a predetermined * ** orientation when at rest, for example when the water is calm and flat. This is referred to herein as a normally vertical orientation'. The vessel is biased into this **** **** orientation, for example by its shape and appropriate location of its centre of gravity.

When acted upon by waves, the vessel is arranged to be displaced from the normally vertical orientation by rotation about an axis other than a vertical axis. In particular, *** * the vessel is arranged to rotate about one or more axes perpendicular to the vertical axis. In other words, the vessel is designed to undergo pitching and/or rolling :.. motions (as described in more detail hereinafter) when acted upon by a wave. It is * this tendency of the vessel to undergo pitching and rolling which is used to generate energy from the waves. It will be appreciated that the pitching and rolling of the vessel will typically occur in combination with a change in vertical elevation, as the vessel rises and falls with the passing waves.

It is a distinguishing feature of the present invention that energy is generated from the pitching and rolling motion, rather than the vertical rising and falling of the vessel. This allows the apparatus of the present invention to be operated independently or coupled to a system for generating energy due to the rise and fall of a floating vessel, thereby increasing the energy recovered from the motion of the waves. Systems for generating energy from the rise and fall of a floating vessel are known in the art and are examples of systems into which the present invention may be incorporated.

The vessel may have any suitable configuration. Most preferably, the vessel comprises a vessel wall and has a portion of its interior that is substantially hollow.

The apparatus further comprises a body. The body is retained by the vessel, such that its movement is generally confined or constrained. However, the body is moveable with respect to the vessel. The body has a first position which is adopted when the vessel is in its normally vertical orientation. The body is biased to the first position, in particular by the action of gravity. The body remains in the first position under the action of the bias or may return to the first position by the bias after being moved from its first position by the vessel, as the vessel is displaced from its normally vertical orientation by the action of the waves. The retention of the body by * *, the vessel is such that, while the body may be moved from its first position by the :,::25 vessel, the biasing acts to hold the body in the first position or to return the body to *** the first position. The net effect is that the body moves relative to the vessel as it is displaced from or returns to its normally vertical orientation. ****. * S

S S..

* In a particularly preferred embodiment, the body is a mass of liquid retained within the hollow interior of the vessel. The volume of liquid is such as to occupy only :. a portion of the hollow cavity within the vessel, allowing the liquid room to move * within the cavity. Any suitable liquid may be used. However, it is particularly preferred and most convenient to employ water, in particular water from the body of water on which the apparatus is deployed. Means may be provided for replenishing or maintaining the volume of water present in the vessel from the body of water on which the apparatus is operating.

At rest, when the vessel is in its normally vertical orientation, the body of liquid within the vessel occupies the lowest portion of the hollow interior available to it. This is the first position of the liquid and corresponds to the normally vertical orientation of the vessel. The surface of the liquid will be horizontal under such rest conditions. In operation, the vessel is tilted from its normally vertical orientation about a lateral axis by the action of a wave, causing the vessel to pitch and/or roll.

Overall, the tendency of the body of liquid is to remain in its first position, with its surface horizontal. This is achieved by the body of liquid moving relative to the vessel, as the vessel is displaced. If the movement of the vessel is slow enough, this is the dominating effect. Under some conditions, such as the rapid displacement of the vessel by a wave, the movement of the vessel is translated to the body of liquid within the vessel by friction or drag between the liquid and the inner walls of the vessel, causing the liquid to move with the vessel. The pitching or rolling action of the vessel serves to tilt the body of liquid at an angle to the horizontal, that is raise one side of the body of liquid and lower the opposing side. Under the action of gravity, the liquid is caused to flow within the vessel from the raised portion to again adopt the first position, with the surface of the liquid horizontal. In doing so, the liquid again moves within the cavity relative to the vessel. The movement of the body of liquid and the relative movement between the liquid and the vessel will be repeated as the vessel returns to its normally vertical orientation under the aforementioned bias. * S...

The principle of the present invention is to generate energy from the relative : movement between the vessel and the body, in particular the body of liquid, which occurs during this cycle of movement of the vessel under the action of the waves. *

S

As noted, the apparatus further comprises a means for generating energy :.. from the relative movement between the body and the vessel. The means may * S comprises any suitable device for generating energy from the relative movement of two bodies, in particular the movement of a body of liquid within a vessel, as hereinbefore described. The means for generating energy may be coupled directly between the body and the vessel. Alternatively, the means for generating energy may act through an indirect coupling.

The energy generating device may be any suitable device or system for generating energy from the movement of the body. Suitable systems include a turbine or pump powered by a liquid or gas, such as a hydraulic pump, the rotor of which is connected to a suitable device for generating energy, such as an electrical generator.

In one embodiment, the body comprises a mass of liquid disposed within a cavity within the vessel, as noted above. The means for generating energy comprises a member disposed on the surface of the liquid. In this respect, the surface referred to is the surface of the liquid when in the first position. The energy generating means may comprise a single member or a plurality of members each of which is connected to one or more energy generating devices. The member may be buoyant relative to the liquid within the vessel, in which case the member will act as a float and will be moved as the surface of the liquid moves within the vessel. In this arrangement, the member may be provided with one or more cavities to provide buoyancy, the cavities being left empty or filled with a buoyant material, such as an expanded material or foam. The buoyant member may be provided with ballast, in order to allow it to follow more closely the movement of the liquid within the vessel.

In one convenient arrangement, the member is provided with a cavity which is filled with liquid from the body of liquid within the vessel, to provide the desired ballast. * S.

Alternatively, the member may be of the same or higher density than the liquid. In such an arrangement, the member acts as a baffle, supported by the vessel and moved by the movement of the liquid within the vessel. Preferably, the member * extends across the cavity within the vessel such that the movement of the liquid around the baffle is reduced, more preferably prevented. In this way, movement of : ...30 the liquid relative to the vessel is more fully realised as movement of the member. In one arrangement, seals are provided between the edges of the member and the inner surface of the vessel, to reduce or prevent the passage of liquid past the member.

In operation, the or each member is moved in response to the movement of the body of liquid within the vessel, in particular following the surface of the body of liquid. Movement of the liquid is thus translated into movement of the member, which is in turn used to generate energy.

The member may be free and untethered at the surface of the liquid, apart from the connection to an energy generating device. Alternatively, the member may be retained. The member may be secured to be moveable about a single horizontal axis. In such a case, the member will move as a result of one of pitching of the vessel or rolling. More preferably, the member is mounted so as to be moveable about more than one axis, in particular two or more axes. In one arrangement, the member is mounted in a gimbal, allowing the member to respond to movement of the vessel in any horizontal axis. The member should be mounted to ensure that it is free to rotate about one or more axes, under the action of the liquid body moving within the vessel. The mounting should preferably prevent the member from being moved in a vertical direction within the vessel, as this will reduce the efficiency of the system in generating energy from the rotational motion of the vessel under the action of the incident waves.

As noted above, the movement of the member in the body of liquid relative to the vessel is used to generate energy. The member is therefore connected to an energy generating device. For example, the member may be connected to one or a plurality of rams, whereby each ram produces a stream of pressunsed fluid, such as * ** hydraulic fluid, oil or gas, under the action of the member moving. Alternatively, any suitable form of mechanical system for generating energy may be employed. Such systems are known in the art.

S

*.....

In one embodiment, the movement of the member is used to generate a *S5 * stream of fluid under pressure, in particular a flow of hydraulic fluid. The pressurised fluid is used to drive a turbine or other energy generating device. To ensure a constant supply of pressurised fluid to it is advantageous to have the pressunsed fluid fed first to a reservoir, such as a tank or the like, from which a constant stream of fluid may be led to the energy generating device. In this way, an intermittent supply of fluid as a result of irregular wave action can be used to provide a constant supply of energy from the system.

In an alternative embodiment, the movement of the body, in particular the body of liquid, within the cavity in the vessel relative to the vessel is used to generate a stream of pressurised gas, typically air. The pressurised gas is fed to a turbine, the gas driving the turbine to thereby generate power, in particular electricity. The movement of the body may be used to generate gas at a superatmosphenc pressure or subatmospheric pressure and the term pressurised' is to be construed accordingly.

In one arrangement, the movement of the body of liquid within the cavity is used to pressurise gas, typically air, within the cavity, which is then lead away from the cavity to the turbine. To increase the pressure of the gas within the cavity under the action of a liquid body, the cavity may be divided into a plurality of compartments into which the liquid is caused to flow. The flow of the liquid into and out of a compartment respectively raises and lowers the pressure of the gas within the compartment. The compartment may be provided with one or more one-way or non-return valves, whereby a change in pressure of the gas within the compartment is converted into a flow of gas to or from the compartment, in turn be used to provide a flow of gas through a turbine to generate energy.

The apparatus may be deployed singularly at a location. Alternatively, the * ** apparatus may be arranged as an array of a plurality of separate units or modules, each unit or module being as hereinbefore described. When an array of more than ***.

one unit is employed one or more buffers may be attached to one or both of an *....: adjacent pair of modules, to prevent damage arising from collisions or contact between adjacent modules. **. *

The apparatus may comprise buoyancy means for providing the apparatus with the required degree of buoyancy, allowing the apparatus to be deployed with an appropriate draft at the surface of the water. In particular, it is preferred to provide the vessel with buoyancy means in its outer regions and/or attached to the exterior of the vessel. In use, the buoyancy means will counteract any tendency of an edge portion of the vessel to sink, under the action of a large or severe wave. In this way, the possibility of the vessel capsizing is reduced or eliminated, as buoyancy means act to right the vessel in such an event. The buoyancy means may be formed as a plurality of buoyant members disposed around the vessel, for example its exterior.

Alternatively, the buoyancy means may be a buoyant member, such as a ring, extending around the outer region of the vessel or around the exterior of the vessel.

If the apparatus comprises buffers, these may be of a design that as well as acting as buffers provide the apparatus with additional buoyancy, and provide the vessel with a self-righting capability.

The means for generating energy most preferably generates electricity. The electric power may be led away from the apparatus by a suitable cable. An array comprising a plurality of modules may have each module connected to a central collection system, such as an electrical hub, from where the combined electrical output of the array may be supplied to users, for example by way of an existing power grid or network.

The apparatus is preferably tethered, for example to a suitable anchor disposed at the bed of the body of water, for example the seabed. Any cables required for the supply of the generated energy may be arranged to run along the tether.

* , In a further aspect, the present invention provides a method for the generation of energy from wave motion, the method comprising: exposing a vessel having a normally vertical orientation to the action of a wave, whereby the vessel is displaced from the normally vertical orientation about an axis other than a vertical axis; * providing a body retained by the vessel having a first position corresponding : to the normally vertical orientation of the vessel, the body being movable with respect to the vessel; S. * * biasing the body to its first position; the displacement of the vessel from its normally vertical orientation causing the body to move relative to the vessel; and generating energy from the relative movement between the body and the vessel.

The vessel is exposed to the action of a wave, for example by being buoyant and floating in the water in which the wave is propagating. The normally vertical orientation of the vessel is the one adopted by the vessel when at rest, for example when the surface of the water is flat and there are no waves. The vessel is displaced by the action of the wave about an axis other than a vertical axis. In particular, the vessel is allowed to rotate about an axis perpendicular to the vertical axis. That is, the vessel is allowed to pitch and/or roll under the action of the wave.

In this respect, the pitch of the vessel is a reference to the change in orientation by rotation about an axis transverse to the direction of propagation of the wave, and the roll of the vessel is a reference to the change in orientation of the vessel by rotation about an axis parallel to the direction of propagation of the wave.

The vessel may be constrained to rotate about a single non-vertical axis, for example to pitch or roll under the action of the wave. More preferably, the vessel is arranged to rotate about any non-vertical axis, in particular any axis perpendicular to the vertical axis. In particular, the vessel is preferably arranged to rotate about a plurality of such axes at the same time, for example to undergo both pitch and roll under the action of the wave.

A body is provided that is retained by the vessel. The body has a first * * position, into which it is biased, which it adopts when the vessel is in the normally vertical orientation. The retention of the body by the vessel is such that the body is **** * * moveable with respect to the vessel when the vessel is displaced from the normally * vertical orientation under the action of a wave and is allowed to move relative to the S.....

vessel either to remain in its first position or return to the first position under the *SI * action of the bias while the vessel is displaced from its normally vertical orientation. * I

The body is most preferably a body of liquid, in particular water, disposed within and moveable within a cavity within the vessel. Under rest conditions, when the vessel is in the normally vertical orientation, the liquid is in the first position and occupies the lowermost portion of the cavity and has its surface horizontal. As the vessel is caused to rotate from its normal vertical orientation, the tendency of the body of liquid is to remain in its first position, under the action of gravity. This requires the body of liquid to move relative to the vessel. Under conditions of slow movement or rotation of the vessel, this will be the dominating effect.

Displacement of the vessel from the normally vertical orientation may move the liquid from its first position, as a result of friction or drag between the liquid and the inner surface of the vessel. This is increasingly likely as the speed of rotation of the vessel increases. Under the action of gravity, the liquid flows back into its first position, while the vessel is so displaced and, in doing so, moves relative to the vessel.

The body is biased to its first position, such that when the vessel is displaced from its normally vertical orientation it remains in the first position or, if moved from the first position by the vessel, it returns under the action of the biasing force. The bias is most preferably provided by gravity.

Energy is generated from the relative movement between the vessel and the body. The energy may be generated by any suitable means. Examples of suitable means include turbines driven by a flow of fluid, in particular liquid or gas. The energy may be generated either directly or indirectly from the movement of the body.

In one embodiment, the body comprises a mass of liquid and movement of * *, the liquid relative to the vessel is transferred to a member suspended in the liquid, movement of the member in turn driving the means for generating energy. The *S*S member may be tethered or untethered, with the exception of the connections to the energy generating means. If tethered, the member is free to rotate relative to the ****** * vessel about at least one transverse axis, more preferably two or more such axes. In *** one arrangement, the member is free to rotate about any one or more transverse :30 axis by a suitable mounting assembly, for example a gimbal. * * ** S. * S * * .

The member may have a density lower than that of the liquid and thus be buoyant in the liquid and behave as a float, moving with the surface of the liquid.

Alternatively, the member may have a higher density that the liquid and act as a baffle, acted upon by the movement of liquid.

Alternatively, the movement of the body relative to the vessel may be used to create a flow of gas, in particular air, which is used in turn to drive a turbine to generate energy. In the case of a liquid body within the vessel, the flow of gas may be generated by allowing the liquid to enter and leave a compartment within the vessel. The inwards and outwards flow of gas within the compartment creates a high gas pressure and a low gas pressure, respectively, within the compartment. The change in pressure in the gas in the compartment is used in turn to produce a flow of gas to drive a suitable turbine.

The method is preferably used to generate electricity. The electricity may be supplied to a suitable grid or network by cables and electrical supply systems well known in the art.

As noted hereinbefore, the present invention generates energy from the action of waves to tilt a vessel from a normally vertical orientation, for example by pitching and rolling. This is in contrast to systems which generate energy from the rise and fall of a buoyant body vertically under the action of the waves. As noted, the apparatus and method of the present invention may be combined with a system for converting the vertical movement of a body induced as a result of wave motion.

* ** Accordingly, in a further aspect, the present invention provides a system for the generation of energy from the motion of waves, the system comprising: ** a buoyant body moveable under the action of a wave; * means for generating energy from the vertical motion of the body; and *S**..

means for generating energy from the rotation of the body about a non-*** * vertical axis.

The system comprises means for generating energy from the vertical motion of the body. Such means are known in the art. An example of such means comprises an arm connected at one end to the buoyant body and pivotably connected at its second end to a support. The support is relatively immovable with respect to the buoyant body and does not rise and fall to the same extent as the buoyant body under the action of the incident waves. The support is preferably anchored so as to be substantially immovable under the action of the waves. Means for generating energy are coupled to the arm. Such means for generating energy may be any of the means mentioned hereinbefore.

In operation, the buoyant body will rise and fall vertically under the action of incident waves. Movement of the body is translated into movement of the arm, which in turn drives the energy generating means.

In order to generate energy from the rotation of the buoyant body, the arm is connected to the body by a linkage that allows the body to rotate about at least one transverse axis. In a simple arrangement, the body is rotatable about the longitudinal axis of the arm. A more complex linkage allows the body to rotate about two or more transverse axes. Thus, as the body rises and falls under the action of the incident waves, it also rotates about one or more transverse axes, for example by pitching and/or rolling. Means are provided for generating energy from this rotational movement of the body. A most suitable means is the apparatus hereinbefore described.

The system may comprise a single buoyant body or a plurality of such bodies.

In one arrangement, the system comprises a plurality of buoyant bodies and a central support assembly, each buoyant body being connected to the support assembly by * ** an arm, the bodies being arranged in a line. Preferably, the bodies are arranged such that the line extends in a direction parallel to the direction of propagation or travel of the incident waves. * * S

In a further aspect, the present invention provides a method for the S..

* generation of energy from the motion of waves, the method comprising: : providing a buoyant body that is moveable in a vertical direction under the *. *. action of a wave and is rotatable about a non-vertical axis under the action of a wave; * . S * S generating energy from the vertical movement of the body; and generating energy from the rotational movement of the body.

The body is preferably arranged to be rotatable about one or more transverse axes.

One most suitable system for the conversion of vertical motion of a body into energy is one in which the body is connected by a pivotable arm to a central support, the support being substantially immobile relative to the body. As the body is caused to move vertically by the action of an incident wave, the motion is translated to the arm, which is in turn raised and lowered. Movement of the arm is employed to generate energy by having suitable means connected to the arm. Suitable means are known in the art and include hydraulic rams and the like.

In one arrangement, the support is anchored to a fixed point, for example the sea or ocean bed. However, the provision of such an anchor can be problematic, especially as the depth of water in which the apparatus is deployed increases. It has been found that the need for such an anchor can be overcome, allowing the apparatus to be deployed in a very wide range of locations, including deep water locations.

Accordingly, in a further aspect, the present invention provides an apparatus for generating energy from wave motion, the apparatus comprising: an elongate floating support assembly comprising a support member and ballast; a plurality of buoyant bodies moveable vertically under the action of an * ,, incident wave, the support assembly being sufficiently ballasted as to be substantially "25 immovable by incident waves relative to the buoyant bodies; ***. * *

an arm extending between each buoyant body and the support member, the arm being pivotably connected to the support member so as to move vertically * together with the respective buoyant body; and *** means for generating energy from the vertical movement of each buoyant body; wherein the plurality of buoyant bodies are arranged longitudinally along the support member; and wherein the elongate floating support is of a length greater than the wavelength of an incident wave, whereby a single incident wave cannot move all the buoyant bodies in the same vertical direction simultaneously.

The apparatus is preferably arranged with the longitudinal axis of the elongate floating support assembly in line with the direction of travel of the incident waves. In this way, a wave propagates along the length of the apparatus raising and lowering the buoyant bodies in succession. The apparatus is of a sufficient length that one or more buoyant bodies will be moving in one vertical direction, for example upwards, under the action of a wave, while others of the bodies will be moving in the opposite vertical direction, for example downwards, at the same time. In this way, the overall stresses on the support assembly are reduced.

Energy may be generated from the vertical movement of the body in any suitable manner. In one preferred embodiment, the vertical movement of the body is converted into movement of an arm connecting the body to a support, energy being generated from the movement of the arm. Suitable means and arrangements for achieving this are known in the art.

In one preferred arrangement, the apparatus is also provided with means for generating energy from the rotational movement of one or more of the buoyant bodies. Energy may be generated from the rotational movement of the body by the method and assembly as hereinbefore described. * **

Embodiments of the present invention will now be described, by way of "* example only, having reference to the accompanying drawings, in which: * *.S...

Figure 1 is a diagrammatical view of an apparatus of one embodiment of the *** * present invention under the action from an incident wave; Figure 2 is a diagrammatical cross-sectional view of an apparatus of one embodiment of the present invention; Figure 3 is a diagrammatical cross-sectional view of an apparatus of a second embodiment of the present invention; Figure 4 is a cross-sectional view through the apparatus of Figure 3 along the line lV-IV; Figure 5 is a diagrammatical cross-sectional view of an apparatus of a further embodiment of the present invention; Figure 6 is a diagrammatical cross-sectional view of an assembly for generating energy from the vertical and rotational motion of a body under the action of a wave; and Figure 7 is a plan view of an elongate array of assemblies of Figure 6.

Referring to Figure 1, there is shown a cross sectional view of a portion of a body of water, such as the sea, generally indicated as 2, having a surface 4. A wave 6 is propagating in the direction of the arrow A, that is from left to right as shown in Figure 1. The surface 4 of the sea has a notional normal rest position, indicated by the horizontal line 4a, that is the position of the surface 4 when no waves are present. It can be seen that the wave 6 causes the actual surface 4 of the sea to move vertically between positions below the line 4a and above the line 4a. * S.

An apparatus of one embodiment of the invention, generally indicated as 10, is shown floating at the surface 4 of the sea 2. Details of the apparatus 10 are described hereinafter. The apparatus 10 comprises a vessel 12, holding a mass of water 14 that is free to move within the vessel but retained by the vessel wall. A * member 16 is disposed at the surface of the water 14 within the vessel and is pivoted : so as to move with the surface of the water. ** S. * S S

S S

As shown in Figure 1, the vessel 12 is caused to rotate as the wave propagates beneath it. In particular, the vessel 12 is caused to pitch first clockwise (the right hand apparatus, as viewed in Figure 1) as shown by arrow B, return to the horizontal position (the centre apparatus, as viewed in Figure 1), and pitch anticlockwise (the left hand apparatus, as viewed in Figure 1) as shown by arrow C. While the vessel 12 pitches in this manner, the water 14 within the vessel behaves differently. The water 14 is biased by gravity and tends to stay in the position with its surface horizontal. This requires the vessel 12 to rotate with respect to the water 14.

Typically, under conditions of slow movement of the vessel 12 by the wave, this is the effect that dominates. If the vessel 12 is moved rapidly by the wave, the water 14 may be initially displaced from its horizontal rest position under the action of the vessel pitching, as a result of friction between the water and the inner surface of the vessel 12. However, the water 14 quickly returns to a position with its surface horizontal, under the action of gravity, while the vessel remains displaced by rotation from its normal vertical orientation. The overall effect is to move the body of water 14 relative to the vessel 12. This relative movement is converted into energy, as described in more detail below.

Referring to Figure 2, there is shown a diagrammatical cross-section of an apparatus according to one embodiment of the present invention, generally indicated as 102. The apparatus 102 comprises a buoyant hollow vessel 104 having a generally circular shape when seen in plan view (not shown for clarity), an arcuate side wall 105 and flattened upper and lower walls 106, 108. The apparatus 102 is shown floating in a body of water, for example seawater, having a surface 110. The surface 110 of the water is shown as being flat. The apparatus 102 is thus shown in its normally vertical orientation, which can be considered to be its position at rest. * **

A body of liquid 112 is retained in the vessel 104. The liquid is water and is **.. most conveniently drawn from the surround body of water. A hole 114 in the lower surface 108 of the vessel 104 allows water to enter the vessel and fill or replenish the * * * body of the water 112 and maintain the correct volume of water within the vessel S..

* 104.

* .* A member in the form of a float 116 is mounted in the vessel by means of a * S S central pivot assembly 118 and supports 120. The float 116 is pivoted so as to be moveable in any transverse axis relative to the vessel 104. This allows the float 116 to maintain or resume its horizontal position shown in Figure 2 when the vessel is rotated or tilted about a transverse axis, such as pitching or rolling, under the action of a wave. A seal assembly 122 is disposed between the edge of the float 116 and the inner surface of the vessel 104 to prevent water from passing the edges of the float 116. The radius of curvature of the side walls of the vessel 104 is such as to allow the float 116 to rotate about its pivot assembly 118.

The float 116 is hollow and comprises an upper cavity and a lower cavity.

The upper cavity of the float is filled with an expanded foam material, or may be empty. The lower cavity is filled with liquid, again most conveniently water from the surrounding body of water. The liquid present in the lower cavity of the float 116 provides the float with ballast, allowing it to more closely follow the movement of the body of liquid. A hole 124 is provided in the lower surface of the float 116 to allow water to enter and fill the lower cavity.

Hydraulic rams 126 are connected between the float 116 and the upper wall 106. Movement of the float 116 relative to the vessel 104 operates one or more of the hydraulic rams 126, generating a flow of pressunsed hydraulic fluid. This flow of pressunsed fluid is used to drive a turbine (not shown for clarity) and generate electricity.

The apparatus 102 is further provided with a buoyant ring 128 mounted to the exterior of the vessel 104 around the side wall. The ring 128 provides buoyancy to the apparatus and acts as a buffer to prevent damage to the vessel 104 in the event * *. of a collision. In particular, the ring 128, being disposed at the outermost region of the apparatus, resists any tendency of the vessel 104 to capsize and acts to right the vessel and maintain or return the vessel to the generally vertical orientation shown in Figure 2.

*.*I*. * * * ***

* In operation, the vessel 104 is rotated and tilted under the action of a wave, * ,,30 as shown in Figure 1. The body of water 112 and the float 116, acted upon by the water 112, tends to remain in the position shown in Figure 2, with the surface of the water 112 and the float 116 horizontal. If displaced as a result of friction with the vessel, the body of water 112 the float 116 quickly resumes this position. The overall effect is that the action of the wave causes the float 116 to rotate about one or more transverse axes relative to the vessel 104, as indicated by arrows E. This in turn generates a flow of pressurised hydraulic fluid from the rams 126, which iS in turn used to generate electrical energy.

Referring to Figure 3, there is shown a further embodiment of the apparatus of the present invention, generally indicated as 202. The apparatus 202 comprises a generally conical vessel 204 having a circular form when seen in plan view, as shown in Figure 4. The apparatus 202 is shown floating in a body of sea water having a surface 206.

The vessel has a flat floor 208, a frusto conical side wall 210 and a flat upper wall 212. A central, generally circular baffle 214 is mounted in the centrally in the vessel. The baffle 214 is spaced from the floor 208 and the side wail 210 to define therebetween a lower chamber 216 and an annular side chamber, divided into a plurality of compartments 218 by walls 220.

Water is present in the lower chamber 216 and fills the lower portion of each compartment 218, as shown in Figure 3.

The upper portion of each compartment 218 is enclosed by a plate 222, having an aperture and a valve in the form of a flap 224 therein. The flap 224 is pivoted to the plate 222 in such a manner as to be urged towards the plate and close the aperture in the event the liquid level in the compartment 218 is too high. This * * prevents liquid from entering the compartments and components located above the compartment 218. *** * * S...

An air flow annulus is provided above the compartments and is divided into a *****.

plurality of air flow chambers 226, formed by walls and plates. Each compartment * 218 has a corresponding air flow chamber 226 connected to each other by a j0 respective valve 224. The air flow chambers 226 extend around a central housing * 228 in which is retained a turbine assembly 230 having blades 232. The turbine assembly 230 is connected by a drive shaft 234 to a generator 236 mounted on the upper wall 212 of the vessel 204. The uppermost portion of the interior of the vessel 204 comprises a pressure chamber 238.

A hollow tubular ring 240 extends around and is mounted to the external surface of the vessel 204 to provide buoyancy and act as a buffer.

In operation, the vessel 204 is tilted and rotated about a transverse axis by the action of incident waves. For the example the vessel 204 is pitched and/or rolled as shown in Figure 1. As the vessel 204 rotates, water is caused to flow into one or more of the compartments 218 on one side of the vessel and to leave one or more of the compartments 218 on the opposing side. The action of water entering a compartment 218 compresses the air within the compartment, which is caused to flow into the respective air flow chamber 226. A system of valves (not shown for clarity) passes the compressed air to the pressure chamber 238, from where it flows past the blades 232 of the turbine 230, causing them to rotate. The action of water leaving a compartment 218 reduces the pressure of air in the compartment, drawing air out of the respective air flow chamber 226. A system of valves (not shown for clarity) connects the air flow chamber 226 under reduced pressure to the interior of the central housing downstream of the turbine assembly 230, drawing air past the turbine blades 232 from the pressure chamber 238. The arrangement is such that the tilting and rotation of the vessel 204 about any transverse axis will cause water to enter and leave different compartments 218, in turn forcing air to move past the turbine blades 232.

As noted, the ingress of liquid into the air flow chamber 226, which may occur when the vessel is severely tilted from its vertical orientation, is prevented by the flap * 25 224. ***S * *

Rotation of the turbine is transferred to the generator 236 by the drive shaft * S * 234, in turn generating electricity. ** S

I

Referring to Figure 5, there is shown a diagrammatical cross-sectional view of r* :* an apparatus according to a further embodiment of the present invention, generally indicated as 302. The apparatus 302 is shown floating in a body of water having a surface 304.

The apparatus 302 comprises a generally rectangular tank 304 having a side wall 306 and a floor 308. A support assembly 310 is mounted centrally within the tank, distanced from the side wall 306 and the floor 308. Water occupies the cavity defined between the support assembly 310 and each of the side wall 306 and the floor 308. An annular baffle 312 extends in the annulus between the side wall 306 and the support assembly 310. Upper and lower seals 314 and 316 are disposed between the side wall 306 and the support assembly 310 and the respective sides of the baffle 312.

A support 318 extends upwards from the support assembly 310. A beam assembly 320 extends horizontally across the top of the support assembly 310 and is pivotally mounted to the support 318. A connecting arm 322 extends from each of the beam assembly 320 to the baffle assembly 312. Each connecting arm 322 is pivotally connected at its respective ends to the beam assembly 320 and the baffle 312.

Hydraulic rams 324 extend from the beam assembly 320 to the support assembly 310. Operation of the hydraulic rams by relative movement between the beam assembly 320 and the support assembly 310 generates a flow of pressunsed fluid, which in turn is used to drive an electrical generator (not shown for clarity).

A tubular ring 326 is mounted to the exterior of the side wall 306 of the vessel 304 and provides buoyancy and acts as a buffer. * **

In operation, as the vessel 304 is tilted or rotated, as shown in Figure 1, by **I* the action of an incident wave, water in the vessel is caused to flow from one side of the vessel to the other. This in turn raise one side of the baffle 312 and lowers the S.....

opposing side, relative to the central support assembly. This is translated into *5d * relative movement between the beam assembly 320 and the support assembly 310, : 30 indicated by arrows F, in turn operating the hydraulic rams 324. * S S.

Referring to Figure 6, there is shown a cross-sectional diagrammatical view of an assembly according to the present invention for generating power from both the vertical and rotational movement of a body under the action of an incident wave. The assembly, generally indicated as 402, is shown disposed at the surface 404 of a body of water, such as sea water.

The assembly comprises a buoyant central support structure 406 held in an upright orientation by a ballast weight 408. The use of a ballast weight in this way renders the support structure 406 substantially immovable, relative to the buoyant arm assemblies, without the need for the structure to be firmly anchored or fixed to the seabed or the like. The structure may be tethered, so that it is able to change orientation as the direction of travel of incident waves changes.

Buoyant arm assemblies 410 extend from opposing sides of the support structure 406. The arm assemblies 410 are connected to the support structure 406 by a pivoted connection. Hydraulic rams 412 extend between the support structure 406 and each arm assembly 410, such that movement of the arm in a vertical direction operates the ram to produce a flow of pressunsed hydraulic fluid.

A buoyant assembly 414 is connected to the distal end of each arm assembly 410. The buoyant assembly 414 is adapted to rise and fall vertically under the action of an incident wave. In operation, vertical movement of the buoyant assembly 414 moves the respective arm assembly 410 in a vertical direction, as indicated by arrows G, in turn operating the respective hydraulic ram 412.

The connection between each arm assembly 410 and its respective buoyant * ** assembly 414 allows the buoyant assembly to rotate and tilt under the action of the incident wave. The buoyant assembly 414 is an apparatus as shown in any of is.. Figures 2, Figure 3 and 4, or Figure 5, for generating energy from such rotational * motion of the assembly. ***.. * S 5.

* S Finally, referring to Figure 7, there is shown a plan view of an array of : 30 assemblies of the general type shown in Figure 6. The array, generally indicated as 502, comprises an elongate central support assembly 504 having a plurality of modules, each indicated as 506. Each module 506 is of the general configuration shown in Figure 6 and described above and components common to both have been indicated using the same reference numerals. Reference is made to the description above relating to Figure 6 for a detailed understanding of the individual modules.

Angled braces 510 are pivotally connected between the distal end of each arm assembly 410 and the central support assembly 504 and help to retain the buoyant assemblies in alignment.

The assembly is arranged to extend with its longitudinal axis in line with the direction of travel of the incident waves, indicated by the arrow H. The assembly is sufficiently long that it exceeds the length of one incident wave and, preferably, spans the length of two or more waves. As the wave passes along the length of the assembly in the direction of arrow H, each of the buoyant assemblies 414 is raised and then lowered in succession. The overall length of the assembly and the number of the buoyant assemblies is such that some buoyant assemblies will be moving vertically upwards, while others are moving vertically downwards. Overall, this reduces the net forces acting on the support assembly 504. The support assembly 504 is preferably sufficiently flexible to accommodate the relative movement of the buoyant assemblies, but is subject to significantly reduced stresses, compared with a shorter structure. * ** S. I * S. is. * I iSdi

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Claims

1. An apparatus for generating energy from waves, the apparatus comprising: a buoyant vessel having a normally vertical orientation and able to be displaced from the normally vertical orientation by rotation about an axis other than a vertical axis by the motion of a wave; a body retained by the vessel but moveable with respect to the vessel, the body having a first position corresponding to the normally vertical orientation of the vessel to which it is biased under gravity, the body being moveable relative to the first vessel to stay in or return to the first position when the vessel is displaced from the normally vertical orientation; and means for generating energy coupled to generate energy by the relative movement between the vessel and the body.

2. The apparatus according to claim 1, wherein the vessel is arranged to rotate about a transverse axis.

3. The apparatus according to claim 2, wherein the vessel is arranged to rotate about a plurality of transverse axes.

,..,

4. The apparatus according to claim 3, wherein the vessel may be subjected to * S. both pitch and roll. *...

5. The apparatus according to any preceding claim, wherein the means for *:. generating energy are connected directly to the body.

: 40

6. The apparatus according to any of claims I to 4, wherein the means for r: generating energy are driven indirectly by the body moving relative to the vessel.

7. The apparatus according to any preceding claim, wherein the vessel comprises a hollow cavity.

8. The apparatus according to claim 7, wherein the body is a mass of liquid retained in the cavity.

9. The apparatus according to claim 8, wherein the apparatus comprises a member disposed at the surface of the liquid when the liquid is in the first position.

10. The apparatus according to claim 9, wherein the member is buoyant and floats at and follows the surface of the liquid.

11. The apparatus according to claim 9, wherein the member is a baffle acted upon by the liquid.

12. The apparatus according to claim 11, wherein a seal is provided between the edge of the baffle and the inner surface of the vessel.

13. The apparatus according to any of claims 9 to 12, wherein the member is retained and pivotable about at least one transverse axis.

14. The apparatus according to any of claims 8 to 13, wherein relative movement between the liquid and the vessel is employed to change the pressure of gas within the vessel, the change of pressure of the gas being used to generate energy.

* **,

15. The apparatus according to claim 14, wherein the vessel comprises a plurality *.*25 of compartments therein, the liquid being caused to enter or leave a compartment as the vessel is displaced from its normally vertical orientation by a wave, movement of liquid into or out of a cavity change the pressure of gas within the cavity. * ***

16. The apparatus according to any preceding claim, wherein the means for * 10 generating energy generates electricity. ** ** * S * * *

17. The apparatus according to any preceding claim, further comprising a buoyant member on or adjacent the exterior of the vessel.

18. An assembly for generating energy from wave motion comprising a plurality of apparatus according to any preceding claim.

19. A method for the generation of energy from wave motion, the method comprising: exposing a vessel having a normally vertical orientation to the action of a wave, whereby the vessel is displaced from the normally vertical orientation about an axis other than a vertical axis; providing a body retained by the vessel having a first position corresponding to the normally vertical orientation of the vessel, the body being movable with respect to the vessel; biasing the body to its first position; the displacement of the vessel from its normally vertical orientation causing the body to move relative to the vessel; and generating energy from the relative movement between the body and the vessel.

20. The method according to claim 19, wherein the vessel rotates about at least one axis perpendicular to the vertical.

*

21. The method according to claim 20, wherein the vessel is constrained to rotate about one axis.

.

22. The method according to claim 20, wherein the vessel rotates about a :25 plurality of such axes.

* :

23. The method according to any of claims 19 to 22, wherein the body is biased *. by gravity.

0

24. The method according to any of claims 19 to 23, wherein energy is generated r** indirectly from the movement of the body.

25. The method according to claim 24, wherein energy is generated from pressurised gas obtained from movement of the body relative to the vessel.

26. The method according to any of claims 19 to 25, wherein the body is a mass of liquid.

27. The method according to claim 26, wherein a member is disposed at the surface of the liquid, movement of the member being used to generate energy.

28. The method according to claim 27, wherein the member is buoyant and floats at the surface of the liquid.

29. The method according to claim 27, wherein the member is a baffle acted upon by movement of the liquid.

30. The method according to any preceding claim, wherein the energy generated is electricity.

31. A system for the generation of energy from the motion of waves, the system comprising: a buoyant body moveable under the action of a wave; means for generating energy from the vertical motion of the body; and means for generating energy from the rotation of the body about a non-vertical axis.

*..

32. The system according to claim 31, wherein the means for generating energy *..:5 form the vertical motion comprises an arm connecting the buoyant body to a support, S...

the means for generating energy being connected between the arm and the support.

S

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* *

33. The system according to claim 31 or 32, wherein the buoyant body comprises an apparatus according to any of claims I to 18.

r**

34. An assembly comprising a plurality of systems according to any of claims 31 to 33.

35. The assembly according to claim 34, wherein the systems are arranged in a line extending in the direction of propagation of the incident waves.

36. A method for the generation of energy from the motion of waves, the method comprising: providing a buoyant body that is moveable in a vertical direction under the action of a wave and is rotatable about a non-vertical axis under the action of a wave; generating energy from the vertical movement of the body; and generating energy from the rotational movement of the body.

37. An apparatus for generating energy from wave motion, the apparatus comprising: an elongate floating support assembly comprising a support member and ballast; a plurality of buoyant bodies moveable vertically under the action of an incident wave, the support assembly being sufficiently ballasted as to be substantially immovable by incident waves relative to the buoyant bodies; an arm extending between each buoyant body and the support member, the arm being pivotably connected to the support member so as to move vertically together with the respective buoyant body; and means for generating energy from the vertical movement of each buoyant body; wherein the plurality of buoyant bodies are arranged longitudinally along the . support member; and * S. wherein the elongate floating support is of a length greater than the S...

wavelength of an incident wave, whereby a single incident wave cannot move all the r' buoyant bodies in the same vertical direction simultaneously.

S S..

S

38. The apparatus according to claim 37, wherein the buoyant bodies are :3o arranged on opposing sides of the support member. S. S. * S S

S S

39. The apparatus according to either of claims 37 or 38, wherein the means for generating energy are connected each arm and generate energy from the vertical movement of the arm.

40. The apparatus according to any of claims 37 to 39, further comprising means for generating energy from the rotational motion of one or more buoyant bodies.

41. An apparatus for generating energy from wave motion substantially as hereinbefore described having reference to Figure 1, Figure 2, Figures 3 and 4, Figure 5, Figure 6 or Figure 7.

42. A method of generating energy from wave motion substantially as hereinbefore described. * S. * S S * S* *.** * S S...

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S..... * S S..

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