The present invention relates to a wave energy converter. More particularly but not exclusively it relates to a wave energy converter that can extract and convert energy from waves in a body of water into kinetic energy for the generation of for example hydraulic, pneumatic or electrical energy or potential energy of a useful kind.

BACKGROUND

Ocean waves are a large source of renewable energy. Over many decades inventors have been working on ways to harness that energy to create electricity for domestic or industrial use. Devices to extract energy from waves may be referred to as wave energy converters and have had many decades of development. Examples of such devices can be seen in US patent US571551 and US1754025. These devices are designed to be installed in geographic locations where there is a desirable level of wave activity in order to be able to extract and convert wave energy at a desirable capacity and rate.

The weather systems that help create ocean waves can be inconsistent. Even in geographic locations where at times very powerful waves are experienced, such locations can also experience waves of very modest or little power. Wave energy at a particular geographic location is hence variable over time. The ocean is an unpredictable environment. Whilst weather and wave forecasting is becoming more and more accurate, long term predictions of wave activity are still reliant on historical data rather than forward looking predictions. Such historical data can help determine where suitable geographic locations for the installation of a wave energy converter are, typically assessed on an annualised basis. The historic data can indicate where large wave energy events have occurred over time in the past and based on the assumption that the weather patterns that caused the waves are consistent or repeat themselves sufficiently often, suitable geographic locations for the installation of a wave energy converter can be determined.

At any given geographic location, the waves generated from any given weather pattern will vary in size and shape in the short term and even wave-to-wave. Not every wave is of the same amplitude, wavelength and shape. For example, open ocean waves may from time to time break, they may have a steep face and less steep back. Ocean current, wind, waves from other weather systems having a different wave direction, frequency and amplitude and many other factors result in ocean waves being far from the often depicted sinusoidal shape.

With wave energy at a particular geographic location being variable over both long and short durations the energy (such as electricity) that is generated by known wave energy converters also vary over time.

Because of the variability in ocean conditions, known wave energy converters are configured for a particular geographic location with the aim of providing an average energy yield on an annualised basis that is desirably high. This may for example be based on anticipated wave conditions over a year. In times when wave conditions are less than optional for the location specific configured wave energy converter, the energy yield may be very poor. This may for example occur when wave height is well below what the wave energy converter is configured for. Conversely when wave height is very large, the wave energy converter may encounter conditions that may be damaging to the wave energy converter.

It is an object of the present invention to provide a wave energy converter and related methods of harvesting wave energy that overcomes or at least partially ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

BRIEF DESCRIPTION OF THE INVENTION

In a first aspect the present invention may be said to broadly consists in a wave energy converter responsive to waves travelling in a body of water, to convert wave energy from waves traveling in the body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the wave energy converter comprising: a) a reactive member to be provided at the surface of the body of water, b) an active member rotationally appended to the reactive member in a manner to be able to rotationally oscillate about a rotational axis and relative to the reactive member, the active member comprising of a positively buoyant float to follow the amplitude of the waves in and at the surface of the body of water to rotationally oscillate the active member relative the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy converter c) a power-take-off (PTO) mechanism, operational between the reactive member and the active member, to convert angular momentum of the active member during its oscillatory rotation directly or indirectly into electrical energy or pressure energy, wherein the PTO mechanism able to apply a variable resistance to the oscillatory rotation between the active member and reactive member to thereby vary the electrical or pressure energy generated by the PTO, and wherein at least one of i) the position of the float is able to be dynamically moved between and held at at least two different distances from the rotational axis, and ii) the position of centre of mass of the active member is able to be dynamically moved between and held at at least two different distances from the rotational axis, to dynamically change the response of the wave energy converter dependent on at least one of the phase, amplitude and frequency of the waves.

Preferably such dynamically changes the response of the wave energy converter dependent on at least one of the phase, amplitude and frequency of the waves, to vary the electrical energy or pressure energy generated by the PTO mechanism.

Preferably the response of the wave energy converter is able to be changed in realtime to the phase, amplitude and frequency of the waves by:

(i) the PTO mechanism able to apply a variable resistance in real time to the oscillatory rotation between the active member and reactive member to thereby vary the electrical or pressure energy generated by the PTO, and (ii) the float that is able to be moved in real time relative the rotational axis to change the lever arm distance between the rotational axis and the float.

Preferably the response of the wave energy converter is able to be changed in realtime to the phase, amplitude and frequency of the waves by:

(i) the PTO mechanism able to apply a variable resistance to the oscillatory rotation between the active member and reactive member to thereby vary the electrical or pressure energy generated by the PTO, and

(ii) a real time change in angular momentum of the active member by changing the distance of centre of mass of the active member relative to the rotational axis.

Preferably the response of the wave energy converter is able to be changed in realtime to the phase, amplitude and frequency of the waves by:

(i) the PTO mechanism able to apply a variable resistance to the oscillatory rotation between the active member and reactive member to thereby vary the electrical or pressure energy generated by the PTO, and

(ii) the float that is able to be moved in real time relative the rotational axis to change the lever arm distance between the rotational axis and the float, and

(iii) a real time change in angular momentum of the active member by changing at least one of (i) a centre of mass of the active member in distance to the rotational axis and (b) the weight of the active member.

Preferably the active member comprises an arm that is rotationally appended to the reactive member in a manner to be able to rotationally oscillate about a rotational axis of and relative to the reactive member, and the positively buoyant float is connected to the arm away from the rotational axis to cause the arm to rotationally oscillate relative to the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy. Preferably the angular amplitude of the oscillatory rotation and torque applied by the active member to the PTO mechanism is able to be changed by at least one of:

(a) the float by the float being appended to the arm in a moveable manner to vary the distance between the float and the rotational axis,

(b) the tuning mass appended to the arm in a moveable manner, to vary the distance between the tuning mass relative to the rotational axis, and

(c) the variable resistance of the PTO mechanism, and

(d) changing the weight of the active member.

Preferably said response of the wave energy converter is a response between the active member and the reactive member, said response is able to be adjusted in real-time by at least one of:

(a) the float, by the float being appended to the arm in a moveable manner to vary the distance between the float and the rotational axis, and a mass appended to the arm in a moveable manner relative to the arm, to vary the distance between the rotational axis and the centre of mass of the active member.

Preferably the torque transferred by the buoyant force of the float via the arm to variable PTO mechanism during the oscillatory rotation of the active member relative the buoy, is able to be varied by at least one of:

(a) the float, by the float being appended to the arm in a moveable manner, to vary the distance between the float and the rotational axis,

(b) a tuning mass appended to the arm in a moveable manner, to vary the distance between the centre of mass of the active member and the rotational axis, and

(c) a rotational axis movement mechanism, to vary the vertical location of the rotational axis at the buoy. Preferably the frequency, amplitude and/or phase relative to the wave phase of oscillatory rotation of the active member relative the buoy is adjustable by at least one of:

(a) a changing of the distance between the float and the rotational axis,

(b) a changing the distance of centre of mass of the active member relative the rotational axis

(c) changing vertical location of the rotational axis at the buoy, and

(d) the variable PTO mechanism.

Preferably said response of the wave energy converter is a response between the active member and the reactive member, said response is able to be adjusted in real-time by at least one of:

(b) the float, by the float being appended to the arm in a moveable manner to vary the distance between the float and the rotational axis, and

(c) a mass appended to the arm in a moveable manner relative to the arm, to vary the distance between the rotational axis and the centre of mass of the active member.

Preferably the angular momentum of the active member about the rotational axis is able to be changed in real time by at least one of:

(a) a changing of the distance between the float and the rotational axis,

(b) a changing the distance between the centre of mass of the active member relative the rotational axis.

Preferably at least one of the:

(a) the distance of the centre of mass of the active member relative to the rotational axis is able to be changed,

(b) the distance between the rotational axis and the float is able to be changed, (c) the location of rotational axis at the buoy is able to be vertically changed.

Preferably the reactive member is provided at the surface of the body of water either above, below or both above and below the surface.

Preferably the reactive member is fixed relative to the bottom of the body of water.

Preferably the reactive member is a buoy.

Preferably the reactive member is a moored buoy able to float and be moved by the waves in and at the surface of the body of water.

Preferably the distance of the centre of mass of the active member relative to the rotational axis is able to move in real-time.

Preferably the active member, rotatably appended to the reactive member, comprises: a. an arm rotatably appended to the buoy in a manner to be able to oscillate about a rotational axis relative to the buoy, and b. a buoyant float appended to the arm away from the rotational axis and able to float and be moved by the waves in and at the surface of the body of water to cause oscillatory rotation of the active member relative to the buoy about the rotational axis as waves progress in the body of water and relative to the wave energy converter,

Preferably the float is appended to the arm in a manner to allow it to move or be moved to and between at least two positions relative the arm, a first position being more proximate the rotational axis and a second position being more distal to the rotational axis than the first position.

Preferably the float can move passively between the two positions.

Preferably the float can move in an idle and unfettered manner between the two positions. Preferably the float and arm are adapted and configured to allow the float to move between the two positions relative the rotational axis by the influence of gravity and wave induced forces (including buoyancy forces) experienced by the wave energy converter.

Preferably the float and arm are adapted and configured to allow the float to move along the arm between the two positions relative the arm, by the influence of gravity and wave induced forces (including buoyancy forces) experienced by the wave energy converter.

Preferably the float and arm are adapted and configured to allow the float to move (eg along the arm) between the two positions only by the influence of gravity and wave induced forces (including buoyancy forces) experienced by the wave energy converter.

Preferably the two positions comprise of a first position that is proximate to but not at the rotational axis at a proximal end of the arm and a second position that proximate the distal end of the arm.

Preferably the centre of buoyancy of the float relative to the rotational axis is able to be moved between a first position relative the arm more proximal the rotational axis and a second position relative the arm that is distal more the rotational axis.

Preferably the centre of buoyancy of the float relative to the rotational axis is able to move between a first position that is proximal the rotational axis and a second position that is distal-more the rotational axis.

Preferably the centre of buoyancy of the float relative to the rotational axis is able to move between a first position relative the arms that is proximal the rotational axis and a second position relative the arm that is distal-more the rotational axis by moving the float along the arm.

Preferably the float is able to be releasably fixed relative to the arm at at least two positions relative the arm.

Preferably a float moving mechanism is provided to cause the float to be actively moved between two positions relative to the rotational axis. Preferably the float moving mechanism is provided to cause the float to be actively moved between the two positions and to selectivity secure the float relative to the arm at at least said two positions.

Preferably the float moves along the arm when moving between the two positions.

Preferably the float moves radially to the rotational axis and preferably along the arm when moving between the two positions.

Preferably the two positions remain fixed relative to the arm.

Preferably the float is appended to the arm to move directly with the arm in the oscillatory rotation of the arm relative to the buoy about the rotational axis as waves progress in the body of water and relative to the wave energy converter.

Preferably the float is rigidly connected to the arm. Alternatively, the float may rotate relative to the arms. This may be efficiency for certain float shapes.

Preferably the float is fixedly connected to the arm.

Preferably a tuning mass is appended to the active member eg to the arm

Preferably a tuning mass is appended to the active member (eg to the arm) to move directly therewith in the oscillatory rotation relative to the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy converter.

Preferably the tuning mass is able to be positioned, a first position being more proximate the rotational axis and a second position being more distal to the rotational axis than the first position.

Preferably the tuning mass is appended to the arm in a manner to allow it to move or be moved to and between at least two positions relative the arm, a first position being more proximate the rotational axis and a second position being more distal to the rotational axis than the first position.

Preferably the tuning mass can move passively between the two positions. Preferably the tuning mass can move in an idle and unfettered manner between the two positions.

Preferably the tuning mass and arm are adapted and configured to allow the tuning mass to move along the arm between the two positions relative the arm, by the influence of gravity and wave induced forces (including buoyancy forces) experienced by the wave energy converter.

Preferably the tuning mass and arm are adapted and configured to allow the tuning mass to move freely along the arm between the two positions only by the influence of gravity and wave induced forces (including buoyancy forces) experienced by the wave energy converter.

Preferably the first position is proximate to but not at the rotational axis at a proximal end of the arm.

Preferably the second location is proximate distal end of the arm.

Preferably the tuning mass is able to be releasably fixed relative to the arm at at least two positions relative the arm.

Preferably a tuning mass moving mechanism is provided to cause the tuning mass to be actively moved between two positions each being at a different distance from the rotational axis.

Preferably a tuning mass moving mechanism is provided to cause the tuning mass to be actively moved between the two positions and to selectivity secure the tuning mass relative to the arm.

Preferably the tuning mass moves along the arm when moving between the two positions.

Preferably the tuning mass moves radially to the rotational axis and along the arm when moving between the two positions.

Preferably the two positions remain fixed relative to the arm. Preferably the PTO mechanism comprises a variable resistance application system able to vary the resistance to rotation between the active member and reactive member to vary the energy converted by PTO mechanism over a given angular displacement of the active member relative to the reactive member.

Preferably the resistance is a toque load acting on arm by the variable resistance application system to vary the energy extracted from the oscillatory motion of the arm by the braking mechanism for conversion to electrical or pressure energy.

Preferably the variable resistance is applied by a variable electrical resistance induced in the PTO mechanism.

Preferably the resistance is caused by pressure resistance of the braking mechanism.

Preferably the resistance is caused by variable pressure resistance of the PTO mechanism.

Preferably the PTO mechanism comprises of an electric generator.

Preferably the PTO mechanism comprises of a hydraulic pressure generator.

Preferably the PTO mechanism comprises of a pneumatic pressure generator.

Preferably the PTO mechanism is able to vary the resistance load applied to the arm to adaptively change the energy converted from angular momentum of the arm, by the power take off mechanism.

Preferably a PTO mechanism comprises a hydraulic or pneumatic pump or an electric generator

Preferably the buoy is geostationary.

Preferably the buoy is anchored preferably to the ground below the body of water.

Preferably the buoy is anchored preferably to the ground below the body of water. Preferably, the wave energy converter further comprises a height adjustment mechanism for moving, or allowing movement of, the rotational axis of the reactive member vertically.

Preferably, the height adjustment mechanism is configured to move, or allow movement of, the rotational axis of the reactive member in response to changes in average sea level, such as tidal changes.

The term 'sea level' is used broadly in this context to apply to any body of water.

Preferably, the height adjustment mechanism is configured to move, or allow movement of, the rotational axis by moving the reactive member relative to a static body or structure.

Preferably, the height adjustment mechanism is configured to move, or allow movement of, the reactive member between at least two operational positions.

The height adjustment mechanism may be configured to move between a plurality of discrete positions, or on a continuum

Preferably, the height adjustment mechanism is configured to lock the reactive member at the operational positions.

Preferably, the height adjustment mechanism is arranged to prevent, limit, or dampen vertical movement of the rotational axis in response to waves in and at the surface of the body of water.

Preferably, the height adjustment mechanism is an active mechanism.

Preferably, the height adjustment mechanism comprises a hydraulic cylinder.

Preferably, the reactive member is positively buoyant and the height adjustment mechanism is a passive mechanism.

Preferably, the height adjustment mechanism comprises a hydraulic damper for resisting vertical movement of the rotational axis in response to waves in and at the surface of the body of water. Preferably, the height adjustment mechanism comprises a telescoping mechanism.

Preferably, the height adjustment mechanism comprises a movement linkage, such as a four-bar linkage.

Preferably the height adjustment mechanism comprises a double-acting telescopic cylinder arrangement having a pair of fluid-filled chambers in fluid communication via a restrictor and an arm member moveable therebetween, wherein the restrictor is configured to limit or dampen the rate of movement of the arm member.

Preferably, the wave energy converter further comprises a sensor for measuring average sea level, or changes in average sea level, wherein the sensor is communicatively coupled to the height adjustment mechanism.

Preferably, the height adjustment mechanism is configured to move, or allow movement of, the rotational axis of the reactive member to dynamically change the response of the wave energy converter dependent on at least one of the amplitude and frequency of the waves to vary the electrical energy or pressure energy generated by the PTO mechanism.

Preferably, the height adjustment mechanism is configured to move, or allow movement of, the rotational axis for limiting the response of the wave energy converter to protect against excessive movement and/or force.

In a further aspect the present invention may be said to be a wave energy converter to convert wave energy from waves traveling in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the wave energy converter comprising: a) a moored buoy able to float and be moved by the waves in and at the surface of the body of water, b) an arm rotatably appended to the buoy in a manner to be able to oscillate about a rotational axis at and relative to the buoy, c) a buoyant float appended to the arm and able to float and be moved by the waves in and at the surface of the body of water to cause oscillatory rotation of the arm relative to the buoy about the rotational axis as waves progress in the body of water and relative to the wave energy converter, the arm adapted and configured to allow the float to move in real-time in a manner to change the distance between the float and the rotational axis, d) a power-take-off mechanism operative between the arm and the buoy to convert angular momentum of the arm relative the buoy during the arm's oscillatory motion about the rotational axis to electrical or pressure energy.

In a further aspect the present invention may be said to be a wave energy converter to convert wave energy from waves traveling in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the wave energy converter comprising: a) a reactive member at or proximate the surface of the body of water, b) an active member rotatably appended to the reactive member in a manner to be able to oscillate about a rotational axis at and relative to the reactive member, and comprising a buoyant float able to float and be moved by the waves in and at the surface of the body of water to cause oscillatory rotation of the active member relative to the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy converter, the active member adapted and configured to allow the float to move in real-time in a manner to change the distance between the float and the rotational axis, c) a power-take-off mechanism operative between the arm and the buoy to convert angular momentum of the arm relative the buoy during the arm's oscillatory motion about the rotational axis to electrical or pressure energy.

In a further aspect the present invention may be said to be a method of adaptively harvesting and converting wave energy from waves in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the method comprising using a wave energy converter as herein described and based on the real time or predicted wave conditions adaptively changing the angular momentum of the active member about the rotational axis by changing at least one of: a. the position of the centre of buoyancy of the float relative the rotational axis, and b. the position of the centre of mass of active member relative the rotational axis.

In a further aspect the present invention may be said to be a wave energy converter to convert wave energy from waves traveling in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the wave energy converter comprising: a. a reactive member provided at the surface of the body of water, b. an active member rotatably appended to the reactive member to be able to oscillate about a rotational axis relative to the reactive member and comprising a buoyant float able to float and be moved by the waves in and at the surface of the body of water so that the buoyant force acting on the float will cause oscillatory rotation of the active member relative to the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy converter, c. a power take off (PTO) mechanism, operational between the reactive member and the active member, to convert relative angular momentum during oscillatory rotation between the active member and the reactive member directly or indirectly into electrical energy or pressure energy.

Preferably the PTO mechanism is able to vary the resistance to rotation between the active member and reactive member to thereby vary the electrical or pressure energy generated.

In a further aspect the present invention may be said to be a wave energy converter to convert wave energy from waves traveling in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the wave energy converter comprising: a) a reactive member provided at or proximate the surface of the body of water, b) an active member rotatably appended to the reactive member to be able to oscillate about a rotational axis relative to the reactive member and comprising a buoyant float able to float and be moved by the waves in and at the surface of the body of water so that the buoyant force acting on the float will cause oscillatory rotation of the active member relative to the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy converter, c) a variable resistance power take off (PTO) mechanism, operational between the reactive member and the active member, to convert relative angular momentum during oscillatory rotation between the active member and the reactive member directly or indirectly into electrical energy or pressure energy, wherein at least one of:

(i) the distance of the centre of mass of the active member relative to the rotational axis is able to be changed (eg by a moveable tuning mass carried by the active member and of the float being movable) in real time, and

(ii) the distance between the rotational axis and the float is able to be changed in real time.

In a further aspect, the invention may be said to be a wave energy converter for converting wave energy from waves traveling in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the wave energy converter comprising: a) a reactive member for providing at the surface of the body of water, b) an active member rotationally appended to the reactive member in a manner to be able to rotationally oscillate about a rotational axis of and relative to the reactive member, the active member comprising of a positively buoyant float to follow the amplitude of the waves in and at the surface of the body of water to cause the active member to rotationally oscillate relative to the reactive member about the rotational axis as waves progress in the body of water and relative to the wave energy converter, c) a variable resistance power-take-off mechanisms (PTO mechanism), operational between the reactive member and the active member, to convert angular momentum of the active member during its oscillatory rotation into electrical energy or pressure energy, d) a height adjustment mechanism for moving, or allowing movement of, the rotational axis of the reactive member vertically in response to changes in average sea level, such as tidal changes.

The wave energy converter of the aspects above may comprise any of the preferably features set out in the preceding statements for the first aspect.

In a further aspect, the invention may be said to be a method of adaptively harvesting and converting wave energy from waves in a body of water to electrical energy or pressure energy (eg hydraulic or pneumatic pressure), the method comprising using a wave energy converter as defined in any preceding statement and based on the real time or predicted wave conditions adaptively changing the angular momentum of the active member about the rotational axis by changing at least one of: a. the position of the centre of buoyancy of the float relative the rotational axis, and b. the position of the centre of mass of active member relative the rotational axis.

In a further aspect, the invention may be said to be a method of adapting the wave energy converter of any preceding statement in accordance with changes in average sea level, comprising: detecting a change in average sea level; raising or lowering the pivot axis using the height adjustment mechanism.

In a further aspect, the invention may be said to be a method of adapting the wave energy converter of any preceding statement, comprising: providing the wave energy converter in a first operational position; detecting a change in average sea level; unlocking the height adjustment mechanism and allowing the reactive member to move vertically from the first operational position to a second operational position; locking the height adjustment mechanism to retain the reactive member in the second operational position.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

As used herein the term "and/or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

The term "comprising" as used in this specification [and claims] means "consisting at least in part of". When interpreting statements in this specification [and claims] which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner.

The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.)

In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

For the purposes of this specification, the term "plastic" shall be construed to mean a general term for a wide range of synthetic or semisynthetic polymerization products, and generally consisting of a hydrocarbon-based polymer.

For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only and with reference to the drawings in which:

Figure 1.1 shows a wave energy converter comprising a buoy and a float in a body of water.

Figure 1.2 shows part of the wave energy converter and a power take off mechanism for converting rotational momentum to for example electricity.

Figure 1.3 shows an alternative power take off mechanism to that shown in figure 1.2.

Figures 2.1-2.3 shows in sequence, a relative motion between the buoy and float and a tuning mass moving between two positions relative to the rotational axis.

Figures 2.4.1 -2.4.5 shows in sequence, a relative motion between the buoy and float and a tuning mass moving between two positions relative to the rotational axis of the wave energy converter of figure 2.1.

Figures 3.1 -3.5 shows in sequence, a relative motion between the buoy and float and a tuning mass controlled for movement between two positions relative to the rotational axis.

Figure 4.1 -4.3 shows in sequence, a relative motion between the buoy and float where the float is able to move between two positions relative to the rotational axis.

Figure 5 shows a variation of the wave energy converter with the reactive member being held fixed and not floating in the body of water. Figure 6 shows a variation of the wave energy converter where the arm and the float are indistinguishable yet there is the provision of a lever arm effect.

Figures 7.1 -7.2 show a wave energy converter comprising a first example of a height adjustment mechanism.

Figures 8.1 -8.2 show a wave energy converter comprising a second example of a height adjustment mechanism.

Figure 9 shows a wave energy converter comprising a third example of a height adjustment mechanism, with some parts illustrated with a cutaway view.

Figure 10 shows a wave energy converter comprising a fourth example of a height adjustment mechanism, with some parts illustrated with a cutaway view.

Figure 11 shows a wave energy converter comprising a fifth example of a height adjustment mechanism.

DETAILED DESCRIPTION

The present invention is a wave energy converter 1 of which a number of embodiments are envisaged. In a broad sense the wave energy converter 1 as depicted in figure 1.1 comprises of a reactive member B that in this example may be considered a buoy B that is preferably moored in a body of water such as the ocean to remain in its desired location. The buoy B may be moored such as by the use of an anchor and anchor chain to the bottom of the body of water A. The buoy B is able to buoyantly float in the body of water A and may be substantially or partially submerged therein.

In another embodiment of the invention the reactive member B may not be in the form of a buoy that floats in the body of water. It may instead be fixed relative to the bottom of the body of water A. It may be supported by piles or attached to a platform that is itself secured to the bottom of the body of water in a fixed or floating manner. The reactive member B may be secured to an oilrig 200 for example as shown in Figure 5. The reactive member may be securely attached to a vessel that itself floats in a body of water.

In the version of the invention where the reactive member B is a buoy B, the buoy B is positively buoyant so that it is able to float at the surface of the body of water A as shown in for example figure 1.1. The buoy B may be of any suitable shape so that it can, when in use, remain floating at the surface of the body of water A. The buoyancy of the buoy may be adjustable. It may have a buoyancy chamber that can be flooded and evacuated with water from the body of water to change the buoyancy of the buoy and hence its waterline level in the body of water and its inertial mass.

In figure 1.1 the state of the body of water is depicted as being calm with the surface of the body of water A being substantially smooth or flat. The wave energy converter 1 is preferably located in a body of water at where that body of water will experience surface waves. The body of water may for example be an ocean. Ocean swell, caused by weather systems in sufficient proximity, can cause such waves to travel through the body of water and reach the wave energy converter.

The wave energy converter can convert wave energy from such waves travelling in the body of water such as into electrical energy or pressure energy.

An active member 2 is appended to the reactive member B. In the example of the invention where the active member 2 is a buoy, the active member 2 is appended to the buoy B to allow for the active member to rotate relative to the buoy B. The rotation is about a rotational axis C. The rotational axis C generally remains substantially horizontal when the wave energy converter is in use. As a result, the active member 2 rotates substantially in a vertical plane. The buoy may be able to rotate about a vertical axis so that its orientation can change. This may occur to allow the wave energy converter to orient itself to the wave direction, which may not be the same all the time. It will be appreciated that sea state can vary and from time to time cause a tilting or tipping of the rotational axis C from its horizontal condition. However, generally the rotational axis remains substantially horizontal. In the example of the wave energy converter where the reactive member is fixed and not floating, the rotational axis C will stay horizontal but is orientation may be adjustable to take account of changing wave directions.

The active member 2 in use oscillates about the rotational axis C and relative to the buoy B. It oscillates over an arc that is of varying length wave to wave, given that each wave is not the same as the next.

The active member 2 comprises of a buoyant float D that is connected to the reactive member in a manner to rotate about axis C in an oscillatory manner. The float D has a centre of buoyancy that is away from and does not pass through axis C so that the float can apply a lever arm force to the reactive member. The float is able to float and be moved by the waves in and at the surface of the body of water. In this configuration the float can cause the oscillatory rotation of the active member relative to the buoy about the rotational axis C as waves progress in the body of water and relative to the wave energy converter 1. In figure 2.4 a sequence of the wave energy converter is shown in a sea with waves travelling through it.

The active member 2 preferably comprises of an arm 3 for the purposes of transmitting the lever arm force mentioned above. It will however be appreciated that the arm 3 may be integrally incorporated with the active member as for example shown in figure 6. The arm may hence be a notional arm.

The arm 3 is rotationally appended to the buoy B in a manner to be able to oscillate about the rotational axis C relative to the buoy. In a preferred form of the wave energy convertor 1, the arm does not rotate 360 degrees about the rotational axis C but merely oscillate over an arc about the rotational axis C.

The buoyant float D is appended to the arm 3 at a location away from the rotational axis C.

When waves are incident onto the wave energy converter, a relative rotation between the buoy B and the active member 2 will occur. Where the reactive member is a buoy, the buoy itself will travel up and down due to the passing waves. This can be seen in the sequence of figures 2.4.1 -2.4.5 where the rotational axis C in not at the same height above the surface the water at each phase of the waves.

Where the reactive member is fixed and not floating, its movement will not be affected by the passing waves. Where the reactive member B is floating, the buoy B is desirably of a configuration that its vertical movement is restricted or limited to help create more relative motion between the active member 2 and reactive member B. To some extent the reactive member B may move up and down and also pitch, so it may hence not stay in the same vertical orientation that is depicted for convenience in the attached drawings. Its momentum in such movement will also cause it to displace more in and out of the body of water. Its waterline will hence vary. Likewise, the float will move up and down as the waves pass the wave energy converter and will also be subjected to not just heave forces but also surge forces of the waves.

It can hence be appreciated that when there is a wave running in the body of water a relative rotation of the active member to the buoy will occur.

A power take off (PTO) mechanism 4 (see figure 1.2 for example), may be provided that is operational between the reactive member B and the active member 2. The PTO mechanism 4 can utilise the relative rotation between the active member 2 and the reactive member B for the conversion of such movement to for example electrical energy or pressure energy such as hydraulic pressure or pneumatic pressure. The PTO mechanism is preferably operational between the reactive member B and the arm 3.

The PTO mechanism may for example be an electrical generator that can convert the relative rotation between the buoy and the active member to electrical energy.

Alternatively, the PTO mechanism may be a hydraulic pressure generator or a pneumatic pressure generator.

The PTO mechanism may be a direct PTO mechanism or alternatively it may indirectly be operational between the active member and the buoy. The example shown in figure 1.2 the PTO mechanism 4 may comprise of an input gear 5 that is geared to an electrical generator 6 for example. The input gear 5 being directly connected to the arm to transfer the rotational motion of the arm in a geared manner to the electrical generator 6. In figure 1.3 an alternative variation is shown of the PTO mechanism 4 where a hydraulic ram 7 is utilized. In figure 1.3 it can be seen that the hydraulic ram is not located at or proximate to the rotational axis C yet can still be operational between the buoy and the arm to be caused to be active based on the relative rotation between the arm and the buoy. Many other PTO mechanisms are envisaged.

Although not shown, the PTO mechanism may be coupled to an energy conversion unit (ECU) for integration with other energy (e.g., electrical) infrastructure, such as the power grid, by for example regulating the voltage, current, and/or frequency of the power from the electrical generator 6. The ECU may be a part of (e.g., mounted on, secured to, or integrated with) the wave energy converter 1, or be a structurally separate (but operatively coupled) unit located on another offshore structure or onshore.

The rotational momentum that the active member 2 has relative to the buoy allows for the PTO mechanism to be used to extract useful energy from wave energy. Such energy may for example be electrical energy that is transmitted to a power grid for example.

In order to ensure that the rotational momentum of the active member is significant and preferably variable to be adaptive to sea state, preferred forms of the active member 2 has certain features that are herein after described.

The upward buoyant force that is experienced by the float D and the heave and surge forces imparted on it by the waves, provide an input force to the active member in a direction or directions that can cause its rotation about the rotational axis C. The mass of both the active member and the buoy are also factors that contribute to the angular momentum that is able to be generated during the oscillatory motion of arm about the rotational axis C. During such oscillatory rotation, a torque T is able to be applied about the rotational axis C by the arm 3. A negative or opposed reactive torque is applied by the PTO mechanism to the input torque of the arm 3. The negative or opposed torque that is applied correlates proportionally to the amount of energy that the PTO converts from the angular momentum to for example electrical energy.

The PTO mechanism is able to vary the reactive torque it applies to the arm in an opposite direction to the input torque. The variation correlates proportionally to the amount of energy that the PTO mechanism is able to generate. The reactive torque may be applied and varied by way a variable electrical load being applied to the PTO mechanism, where the PTO mechanism is an electrical generator.

The PTO mechanism is able to exert a resisting force on the arm. Hence the PTO mechanism can dampen the motion of the arm. The amount of resistance can be varied. An objective of the resistance is that the active member should move as much as possible and the amplitude of the active member is varied by varying the resistance applied by the PTO mechanism but ensuring not too much resistance is applied as otherwise the relative motion between the active and reactive members stops.

When the sea state is large and the amplitude of the waves is substantial the range of the arc that the arm travels relative to the buoy is large. In addition, the energy in the waves is more substantial when compared to a wave of a smaller amplitude. Therefore, the wave energy converter has the potential to extract more energy from the waves in such a sea state. In order to allow for the wave energy converter to adapt to different sea states to better utilise the energy of the waves, the wave energy converter of this invention is able to be dynamically reconfigured. There are a proposed number of examples of wave energy converters of the present invention that are capable of reconfiguration that will now be discussed.

With reference to figures 2.1 - 2.4 a first example of a wave energy converter 1 is shown where the active member 2 includes a tuning mass F. In the example of the wave energy converter shown in figures 2, a tuning mass F is preferably of a fixed weight. Alternatively the tuning mass is of an adjustable weight. It may be dynamically adjustable and may for example utilise water from the body of water to dynamically adjust. Water may be displaced (e.g., by a pump) into and out of a buoyancy tank of the tuning mass.

The tuning mass F is carried by the active member 2 to rotate with the active member 2 about the rotational axis C. It hence oscillates with active member 3.

The tuning mass may be able to be displaced relative to the axis C to be more proximate to the axis C and more distal from the axis C. A more proximal position of the tuning mass F is shown in figure in 2.2 and a more distal position is shown in figure 2.3. In the first position as shown in figure 2.2 the tuning mass is more proximate to the rotational axis C and as a result the angular momentum of the active member for a given rotational speed is less compared to when the mass F is in a second position being further away from the rotation axis C as shown in figure 2.3. In the second position the angular momentum of the active member 2 is greater for a given rotational speed of the active member about the axis C.

In some embodiments the tuning mass F may be fixed relative the axis C and instead may provide an ability to tune the wave energy converter purely by having the ability to vary its weight.

In the example of the wave energy converter in figures 2.1 -2.3, the tuning mass is able to move freely and unfretted between its first position shown in figure 2.2 and it's second position shown in figure 2.3. The mass may be restrained by a slot E or rails or the like for example, part of the active member. Within the slot E the tuning mass F is able to freely move between it's two positions based on gravitational forces and input forces and other dynamic forces that it experiences relative to the active member.

The tuning mass F may be attached to the active member or may be within the active member such as in the arm and/or the float.

In a preferred form the tuning mass may be of a constant weight and in the form of a solid mass for example. Alternatively, the tuning mass may comprise of a tank or tanks that is/are capable of being flooded and evacuated of water from the body of water to thereby allow for that tuning mass to be varied by weight and not just its position relative to the rotational axis.

In the example shown in figures 2, the mass can either be moved by using gravity which could be accomplished when the wave rises the surface of the body of water which would then cause the float to rise as seen for example in figure 2.4.3 - 2.4.4 the mass is then able to fall closer to the rotational axis C. The opposite happens as seen in 2.4.1, 2.4.2 and 2.4.5 where the mass can fall relative to the rotation member to move further away from the rotational axis C. The use of dynamic forces as per the example of the wave energy converter of figure 2 can allow for the tuning mass to be displaced without the need for a displacement mechanism of the wave energy converter. In this example there may be a way of capturing the tuning mass in a desired location between its limits of movement between the first position of figure 2.2 and the second position of figure 2.3. A brake or ratchet or other type mechanism may be incorporated in the wave energy converter to lock the tuning mass in position relative to the active member at intermediate locations between the first and second position.

A variation to the wave energy converter as shown in figures 2 is shown in figures 3. In figures 3 a tuning mass F is provided which may be of a fixed weight or a variable weight. In the variation of the wave energy converter of figure 3 the tuning mass is able to be actively positioned by a mechanism G to move and hold the mass in its desired location and desired distance away from the rotational axis C. The moving mechanism G may be a mechanical mechanism. It may rely on mechanical actuators, hydraulic or pneumatic actuators or an electrical actuator, or other actuators with mechanical elements to move and hold the mass in its desired position. It can move the tuning mass in an active and real-time manner. This may be desirable to dynamically reconfigure the wave energy converter in response to changing sea states and/or in response to the next incident wave.

Other methods to move the mass with a force or pressure could include pumping a of liquid. Another variation may include an array of chambers able to be selectively flooded by water from the body of water. The array of chambers may be radially spaced relative to the rotational axis C along the active member. Valves or gates or the like may be utilised for controlling the in and out flow of water selectively to each of the chambers independently in order to thereby vary the angular momentum of the active member for any given rotational speed of the active member about the rotational axis C.

It can be seen in figures 3.4 the mass F is held at its first position relative to the rotational axis C and in figure 3.5 the mass F is held in its second position more distal from the rotational axis C than the first position.

Moving the mass out further from axis C will help extract more power because the torque arm becomes longer. This is useful for extracting energy from higher waves that can exert more force on the arm. Moving the mass in towards the axis C will make the float believe it is lighter than it is.

The process of moving the tuning mass F may involve optimising the float movement and then optimising PTO mechanism applied damping. This may involve increasing the damping force that is applied until that starts to affect the float movement adversely.

A further variation of a dynamically adjustable wave energy converter of the present invention is shown in figures 4. In figures 4 the float D (or at least its centre of buoyancy, COB) is able to be moved relative to the rotational axis C. In the example shown in figure 4.2 the float is more proximate to the rotational axis C than in its second position shown in figure 4.3 where the float D is more distal. This changes the Centre of Buoyancy (COB) position and hence the active force against the torque T able to be applied by the float about the rotation axis C. In a preferred form a mechanism is provided that allows for the buoy to be displaced along the arm 3 and in an active manner and to be able to be held in position relative to the arm when the desired location of the buoy relative to the arm is achieved.

In some embodiments the wave energy converter may utilise more than one of the means of dynamic adjustment as set out above.

The positioning and repositioning of the float and/or the centre of mass relative the rotational axis may be achieved by their displacement along the arm but it will be appreciated that this may also be achieved by an arm that is articulated or telescopic for example. So hence "along the arm" should be interpreted as being of a notional arm of a lever arm.

By being able to be dynamically reconfigured, the wave energy converter of the present invention can allow more energy to be extracted from the waves in the body of water on the basis that the sea state will change over time. Allowing more velocity of the active member to be generated can equate to more power being able to be extracted from the waves.

The energy able to be extracted is dependent on the amplitude of the active member and the acceleration of the active member.

Moving the centre of mass changes the frequency response of the device between the float and the primary buoy. Moving the centre of mass in towards the buoy may be better for extracting energy from smaller waves because the mechanism then becomes more responsive to smaller wave energy.

An advantage of the real time adaptive reconfigurability of the wave energy converter of the present invention is that it can adapt to changing sea states yet endeavour to achieve a high energy yield from incident waves. The dynamic adjustability of the wave energy converter means that for any given location its design optimisation is not confined by what the average wave conditions are on say an annual basis. This may have the potential to reduce wave energy product costs as a PTO of a smaller size may be capable of being used to be effective over a very large range of sea states due to the ability of the wave energy converter to dynamically adapt to sea states in a manner to help ensure the PTO is being worked as much as possible/needed.

A further consideration for sea state and wider geographic adaptability is that of tidal variation. Most large bodies of water are subject to changes in sea level (used generically in this context for any body of water) to some extent as a result of tidal forces, and oftentimes the offshore locations that provide consistent wave energy (and are therefore desirable locations for wave energy harvesting) also experience a large tidal range; it is not uncommon for there to be several metres between high water and low water. Even average sea level is not persistent long term and can decrease or, more likely, increase over time due to changes in climate. These changes occur over much longer timescales than the relatively high-frequency changes associated with travelling surface waves. For example, tidal oscillations occur on the order of hours compared to seconds for the surface wave oscillations that are used to generate energy in the context of the present disclosure. Hence, the energy-generating oscillations (i.e., waves) are herein referred to as 'high-frequency' whereas the non-energy generating oscillations (e.g., tides) are referred to as 'low frequency'.

As mentioned previously, the relative position of active and reactive members can influence the amount of power generated by the wave energy converter, and this may generally be achieved with the rotational axis C therebetween at or near the surface of the water. Therefore, for fixed wave energy converters (i.e., those secured to the seabed, shore, or a fixed structure, such as the oil rig 200 in figure 5), it can be desirable to enable vertical adjustment of the rotational axis C between active and reactive members in response to (or anticipation of, or otherwise in accordance with) low frequency changes in sea level so that the reactive member B and the active member 2 remain in an operatively effective relative configuration (preferably with the rotational axis C at or near the surface of the water). However, the performance of the wave energy converter can also be dependent upon the relative immobility of the reactive member in the context of high-frequency wave-generated motion, since a more static reactive member can provide for greater relative movement between the active member and the reactive member in response to waves. As such, the reactive member also preferably remains operatively substantially fixed (or at least limited, or dampened, in its vertical motion) with respect to high-frequency oscillations.

The following description provides, by way of the examples shown in figures 7-11, wave energy converters that broadly comprise means for adjusting the height (i.e., moving vertically) of the rotational axis C through a plurality of operative positions (discrete or continuous) in which, at said operative positions, the reactive member is preferably substantially fixed (in vertical movement, and preferably also in other movement, such as horizontally or pitching).

The reactive member is moveably coupled to a fixed structure via a height adjustment mechanism (also referred to as a tide adaptor mechanism), which is configured to raise and lower the reactive member to thereby raise and lower the rotational axis C in accordance with average sea level. The mechanism may be an active mechanism or a passive mechanism.

In the illustrated examples of figures 7-11, the active member 2 comprises of a wedge-shaped float D, in which the arm members 3 that connect the float to the rotational axis C are mostly integrated as per figure 6. The reactive member B has a bridge-like form comprising a pair of vertical arm members 8 between which the float B is rotatably coupled via a rotatable shaft 9 that extends horizontally along the rotational axis C (about which it can rotate). The PTO 4 comprises a pair of energy capture cylinders 7 disposed above the float B between the float and a frame 10 extending between and projecting horizontally forward from the pair of vertical arms 8. The active member 2 may be configured according to any of the examples discussed in relation to figures 1 -6. Preferably, the active member 2 is configured with a passively moving tuning mass F as per figures 2.4. This is just one preferred form and is not intended to be limiting. The skilled person will recognise that the general principles apply equally for the simplified forms described elsewhere in this specification. Additionally, any specific features shown here may be also present in any of the examples described in this specification.

Figure 7.1 is a first example of a wave energy converter 1 comprising a telescoping height adjustment mechanism 11. Figure 7.2 is a cut-away view of figure 7.1 in which interior components are visible.

The telescoping mechanism 11 comprises a first elongate arm 8 (e.g., a cylindrical tube) retractable into, and extendable from, a second elongate arm 12 (e.g., a cylindrical tube of greater diameter) along the elongate axis thereof. The first elongate arm 8 is connected to, or part of, the reactive member B, such that movement of the first arm 8 causes a corresponding movement of the rotational axis C. Preferably, the first elongate arm 8 is a vertical arm member 8 of the reactive member B. The second elongate arm 12 may be fixed for example to the seabed, shore, or other static structure or body. Preferably, a pair of telescoping mechanisms 11 is provided as shown, wherein each comprises a first and second elongate arm 8, 12 as above.

As seen in figure 7.2, the extension and retraction of the first arm 8 may be driven by a hydraulic cylinder 13 or the like housed within, and coupled between, the first and second arms 8, 12.

The telescoping mechanism 11 may be controlled by a controller to adjust the height of the reactive member in response to average sea level as determined by one or more sensors. The sensors may be provided as part of the wave energy converter (e.g., disposed on a structure thereof), or located externally but in communication with a controller of the wave energy converter 1.

Alternatively, the telescoping mechanism 11 may be a passive mechanism. For example, the reactive member B may be arranged to be positively buoyant such that the extension and retraction of the first arms 8 is driven by environmental forces (upthrust and gravity) as the reactive member B naturally follows the rising and falling of average sea level. Preferably, the reactive member B is arranged to float at the operationally desired position (e.g., at, on or proximate the surface of the body of water), such as by connection to an appropriately buoyant float. One example of a wave energy converter having a passive telescoping mechanism 11 is shown in figures 8.1 -8.2. Here, the reactive unit B comprises a float B' and the hydraulic cylinder is replaced with a hydraulic damper 13 or the like, which allows the reactive unit B to respond buoyantly to low frequency changes in sea level but prevents, dampens or restricts movement in response to high-frequency changes. In other words, the damper 13 may be configured to filter out high-frequency variations in height due to waves but allow the reactive unit B to adjust to the low frequency tide height changes.

A further passive telescoping variation is shown in figure 9. The telescoping mechanism 11 works in much the same way as that described above, except that the dampers 13 are replaced with a mechanical locking mechanism 14, which fixes the position of the first arm 8 relative to the second arm 12 for operation when a desired position has been reached. When the locking mechanism 14 is in an unlocked position, the reactive member is able to move up and down freely (guided by the buoyancy of the reactive member). When the locking mechanism is in a locked position, the reactive member is vertically fixed. The locking mechanism may for example comprise a retractable pin or bolt 15 arranged to extend through holes or slots 16 in the telescopic arms. The locking mechanism 14 may be locked and unlocked in response to detecting sufficient changes in average sea level, such as via sensors as described above. A sufficient change may correspond to the distance between successive holes 16 along the telescopic arms 12.

Yet another example of a passive height adjustment mechanism is the double-acting telescopic cylinder arrangement shown in figure 10. In this example, the first arm members 8 of the reactive member B have upper and lower end regions 8a, 8b, each moveably housed within upper and lower fixed cylinders 12a, 12b, respectively. The upper and lower fixed cylinders comprise chambers 17 that are filled with fluid and into which a respective end of the first arm members can move. The chambers 17 are in fluid communication with one another along fluid lines 18 connected via a restrictor 19, which moderates the transfer of fluid from one chamber 17 to the other. Hence, the speed at which the first arm members 8 can move up or down into a fixed cylinders 12 (and thus displace the fluid within) is limited or dampened by the restrictor 19. This restrictor 19 can therefore act to filter out high-frequency variations in sea level due to waves whilst allowing the unit to adjust to the low frequency tide height changes. Figure 11 shows a further example of a wave energy converter having a height adjustment mechanism that may be particularly suitable in cases where the wave energy converter 1 is fixed to an adjacent structure, such as the oil rig 200 of figure 5.

Here, the height adjustment mechanism comprises a movement linkage 11 such as the illustrated four-bar linkage. A first link 20a connects an upper end region 8a of the vertical arm 8 to a first static point 21a, and a second link 20b connects a lower end region 8b of the vertical arm 8 to a second static point 21 b (below the first). The static points 21a, 21 b may be, for example, points on a fixed structure such as the oil rig 200 in figure 5. The link connections are articulated joints 22 such that the vertical arm 8 is moveable vertically relative to the fixed structure.

The mechanism may be active in which case movement is driven by a hydraulic cylinder 17 connecting diagonally across the linkage 11. In the case of a passive mechanism, the hydraulic cylinder may be replaced by a hydraulic damper 17, with operation analogous to that already discussed.

Where the reactive member B comprises a pair of vertical arm members 8, as illustrated, the height adjustment mechanism may comprise a corresponding pair of linkages. The linkages on each side may be coupled via beams 23 that provide a rigid structure.

The height adjustment mechanism described in any of the examples above may additionally, or alternatively, be used to adjust the height of the rotational axis C for dynamic sea state adaptability as described for the examples in figures 1 -4. For example, the rotational axis C may be raised or lowered in response to changing amplitude and/or frequency of incident waves with a view to extracting more energy from waves in the body of water. In particularly heavy seas, such as waves of large amplitude beyond the tolerance of the wave energy converter where there may be a risk of damage, the height adjustment mechanism may be used to lower the rotational axis C below the surface of the body of water such that the wave energy converter assumes a 'survival mode'. In this mode, the wave energy converter may be configured such that the waves overtop the active member limiting the movement of the active member. The wave energy converter may still be operative in the sense that power is generated, though the response to the incident waves limited to avoid excessive movement and/or force. The wave energy converter may be configured to assume the survival mode automatically upon detecting certain sea state conditions. Sea state conditions may be monitored using a sea height sensor. Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

Although the invention has been described by way of example and with reference to particular embodiments, it is to be understood that modifications and/or improvements may be made without departing from the scope or spirit of the invention.

In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognise that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.