GB2638182A

GB2638182A - Apparatus for generating energy from water waves, watercraft and sails

Info

Publication number: GB2638182A
Application number: GB2402059.6A
Authority: GB
Inventors: Rayne Damian
Original assignee: Individual
Current assignee: Individual
Priority date: 2024-02-14
Filing date: 2024-02-14
Publication date: 2025-08-20
Also published as: WO2025172515A3; GB202402059D0; WO2025172515A2

Abstract

Apparatus 1 for generating energy from water waves 2 comprises a buoyant body 3 comprising a first and second body sections 4, 5 and a ballast 7. The ballast is rotationally fixed relative to and first body section, and both together can rotate relative to the second body section in first and second opposed directions. The apparatus further comprises an energy generation system 10 comprising first and second gears 11, 12, first and second flywheels 13, 14 and first and second generators 15, 16. The first gear rotates in the first direction 8 only and the second gear rotates in the second direction only. A first drive path is provided from the ballast to the first generator via the first gear and first flywheel such that relative rotation between the ballast and the second body section in the first direction drives the first generator. A second drive path is provided from the ballast to the second generator via the second gear and second flywheel such that relative rotation between the ballast and the second body section in the second direction drives the second generator. A watercraft comprising a mast rotationally fixed relative to a keel, and both together rotatable relative to a hull may include the apparatus for generating energy from waves. A sail for the watercraft comprises at least one blade.

Description

APPARATUS FOR GENERATING ENERGY FROM WATER WAVES, WATERCRAFT AND SAILS

FIELD

The present disclosure relates to an apparatus for generating energy from water waves, watercrafts, and sails for watercraft.

BACKGROUND

Renewable energy is highly sought after, as traditional finite energy sources are becoming scarcer, and tidal energy may be thought of as an inexhaustible resource. The present disclosure provides improved apparatus for harnessing the power of water waves and generating energy therefrom; and also provides improved watercraft and sails; as well as improved watercraft comprising such sails and/or such energy generating apparatus.

Water waves are sinusoidal and therefore have both positive and negative amplitude in one wave cycle, with the wave crests having positive amplitude and the wave troughs having negative amplitude. As water waves pass along a floating object, the series of wave crests and wave troughs cause the object to reciprocate, and it is this reciprocating movement that can be used to generate energy from the water waves.

A known apparatus for generating energy from water waves, as described in US 2012/0007363 A1, comprises a pair of floats adapted to rise on a water surface such that the pivot rod is rotatable C\J relative to the main frame in response to water wave front action to generate a bidirectional mechanical rotary power output corresponding to water wave energy.

A further known apparatus for generating energy from water waves, as described in CN 102650255 A, comprises power generation boxes, cylindrical floating pontoons for providing buoyancy and rigid connecting rods.

A further known apparatus for generating energy from water waves, as described in DE 2847750 A1, comprises at least two floats connected to allow them to pivot and/or move vertically relative to one another. This movement is transferred via a cog mechanism to a rotary drive shaft, which is in turn coupled via a freewheel coupling, operable in either direction, to a generator.

A known watercraft, as described in EP 2 775 140 A1, comprises a floating structure fluid dynamic force use system and a wind-propelled vessel which uses the system whereby it is possible to compensate for overturning moment due to fluid dynamic force and to alleviate both tilting and size increases of a floating structure.

A known sail for a watercraft, as described in DE 28369221 A1, comprises several sets of masts that are mounted on the raft parallel to each other. In each set the masts at the corners are fixed. The masts between them can be moved laterally along guides by a hydraulic or mechanical mechanism. When not required they are thus moved until they are up against the fixed masts to form a single composite mast.

A further known sail for a watercraft, as described in US 201 5/01 91 234 A1, comprises an aerofoil sail for providing motive power to a waterborne vessel, the sail comprising a leading aerofoil portion and a trailing aerofoil portion, and the sail comprising a spar, at least one of the aerofoil portions rotationally positionable, and the sail comprising a controller to control individually the angular position of at least one of the aerofoil portions relative to the spar, and the spar rotationally positionable about its longitudinal axis.

The present disclosure seeks to alleviate, at least to a certain degree, the problems and/or address at least to a certain extent, the difficulties associated with the prior art.

SUMMARY

According to a first aspect of the disclosure, there is provided an apparatus for generating energy 20 from water waves, comprising: a buoyant body comprising a first body section and a second body section, wherein the buoyant body comprises a longitudinal axis; and a ballast, wherein the ballast and the first body section are configured to rotate relative to the C\J second body section about said longitudinal axis both in a first direction and a second direction, the second direction being opposite to the first direction; wherein the ballast is rotationally fixed relative to the first body section such that rotation of the first body section relative to the second body section about said longitudinal axis causes the ballast to rotate relative to the second body section about said longitudinal axis, and such that rotation of the ballast relative to the second body section about said longitudinal axis causes the first body section to rotate relative to the second body section about said longitudinal axis; an energy generation system, comprising: a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in the first direction only and the second gear is configured to rotate in the second direction only; wherein the ballast is coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the ballast to the first generator, such that relative rotation between the ballast and the second body section in the first direction drives the first generator; and wherein the ballast is coupled to the second gear, the second gear is coupled to the second 40 flywheel, and the second flywheel is coupled to the second generator, so as to define a second drive path from the ballast to the second generator, such that relative rotation between the ballast and the second body section in the second direction drives the second generator.

Advantageously, the relative rotation between the ballast and the second body section in both the first direction and the opposite second direction allows the apparatus to generate energy throughout the whole water wave cycle, thus generating more energy per water wave cycle. This is because water waves are typically sinusoidal and have both positive and negative amplitudes, with the wave crests having positive amplitude and the wave troughs having negative amplitude. Therefore, as the water wave passes along the longitudinal axis of the buoyant body, it causes points along the longitudinal axis to rise as the wave crest passes through the point and fall as the wave trough passes through the point, and, hence, providing for relative rotation between the ballast and the second body section in two directions facilitates that the apparatus can harness the power of the waves throughout the entire cycle, and thus generate more energy therefrom. Furthermore, the first drive path and the second drive path comprise few parts, thus increasing the efficiency of power generation as fewer energy conversions need to be made.

Optionally, the buoyant body comprises a generally cylindrical sealed chamber. Advantageously, the generally cylindrical sealed chamber can act as a float and provides surface buoyancy sufficient for the apparatus to ride on the surface of the water waves. Furthermore, the chamber being sealed provides that if any components are placed inside the chamber, they are protected from water ingress and other potential damage from the water waves and foreign object debris.

Optionally, the ballast is configured to protrude from the first body section, and during use of the CV apparatus, may be configured to be at least partially submerged underwater. Advantageously, the ballast being configured to be at least partially submerged underwater contributes added stability to the apparatus by shifting the resonance periods of the apparatus out of the predominant wave periods and damping the motion of the apparatus.

Optionally, the ballast comprises an elongate element and a base element, the base element for example comprising a generally circular portion; wherein the elongate element is coupled to the first body section at a first end of the elongate element, and wherein the elongate element is coupled to the base element at a second end of the elongate element.

Optionally, the base element is generally spherical or ellipsoidal.

Optionally, the ballast is a heave plate. Advantageously, the heave plate contributes added stability to the apparatus by shifting the resonance periods of the apparatus out of the predominant wave periods and damping the motion of apparatus.

Optionally, the heave plate is configured to be arranged below the surface of the water waves, such 40 that it is configured to be at least partially submerged underwater during use of the apparatus.

Optionally, the heave plate is configured to be arranged between approximately 8 metres to 16 metres below the surface of the water waves, more preferably between approximately 10 metres to 14 metres below the surface of the water waves, more preferably approximately 12 metres below the 5 surface of the water waves.

Optionally, the first body section is coupled to the second body section by a first shaft and a second shaft, wherein the first shaft is coupled to the first gear such that rotation of the first shaft in the first direction drives the first generator, and wherein the second shaft is coupled to the second gear such 10 that rotation of the second shaft in the second direction drives the second generator.

Optionally, the first generator and the second generator are configured to generate energy, for example electrical energy. Advantageously, the first generator and second generator generating energy, such as electrical energy, provides a sustainable source of energy that does not use finite resources.

Optionally, the first body section and the second body section are arranged to be concentric with respect to one another. Advantageously, this allows the first body section and the second body section to rotate about the same axis, that is, for them to share a common longitudinal axis corresponding to the longitudinal axis of the buoyant body.

Optionally, one of the first body section and the second body section is arranged to be at least partially arranged inside the other one of the first body section and the second body section. C\J

Optionally, the first body section is at least partially arranged inside the second body section.

In this way, the first body section may comprise an inner body section of the buoyant body and the second body section may comprise an outer body section of the buoyant body.

Optionally, the second body section is at least partially arranged inside the first body section.

In this way, the second body section may comprise an inner body section of the buoyant body and the first body section may comprise an outer body section of the buoyant body.

Optionally, at least a portion of the first body section is generally cylindrical and at least a portion of the second body section is generally cylindrical.

Optionally, the energy generation system is arranged inside the first body section and/or the second body section. Preferably, the buoyant body is hermetically sealed. Advantageously, this protects the energy generation system from water ingress and other potential damage from the water waves and foreign object debris.

Optionally, the first flywheel is configured to rotate in the first direction only and the second flywheel is configured to rotate in the second direction only. Advantageously, the first flywheel and the second flywheel being configured to rotate in opposite directions with respect to each other eliminates any gyroscopic effects. Additionally, the first flywheel and the second flywheel are configured to store rotational energy such that: when the ballast rotates in the second direction, the first flywheel continues to rotate in the first direction thus continuing to power the first generator even when the first gear is not being rotated; and when the ballast rotates in the first direction, the second flywheel continues to rotate in the second direction thus continuing to power the second generator even when the second gear is not being rotated.

Optionally, the flywheel comprises a substantially large mass configured so as to increase the momentum of the flywheel. Advantageously, the flywheel comprising a substantially large mass gives the flywheel high inertia and allows the flywheel to absorb energy and release energy with little change in speed.

Optionally, the apparatus further comprises an energy generation system rotational axis, about which the first gear and the first flywheel are configured to rotate in the first direction, and about which the second gear and the second flywheel are configured to rotate in the second direction.

Optionally, the ballast is configured to rotate about the energy generation system rotational axis. C\1

Optionally, the central axis of the first generator is offset from the energy generation system rotational axis and the central axis of the second generator is offset from the energy generation system rotational axis.

Optionally, the first generator and the second generator each comprise a central axis, wherein the central axis of the first generator is parallel to the energy generation system rotational axis and the central axis of the second generator is parallel to the energy generation system rotational axis.

Optionally, the energy generation system rotational axis is generally parallel to the longitudinal axis of the buoyant body.

Optionally, the energy generation system rotational axis is coincident with the longitudinal axis of the buoyant body. Advantageously, this allows the first and second gears and the first and second flywheels to rotate about the same axis that the first and second body sections rotate about, that is for them to share a common rotational axis.

Optionally, the ballast comprises a propulsion system. Advantageously, the propulsion system may provide a steering effect, such as a differential steering effect, to the apparatus, such that the apparatus may be propelled through the water and/or directed to point the apparatus into the oncoming water waves so as to ensure maximum energy generation.

Optionally, the propulsion system comprises at least one duct, wherein each of the at least one ducts comprises an inlet configured to draw water into the at least one duct and wherein each of the at least one ducts comprises an outlet configured to expel water out of the at least one duct.

Optionally, the ballast is configured to be anchored. Advantageously, the ballast being configured to be anchored allows the apparatus to stay fixed in the same location and not float away. Furthermore, the ballast being configured to be anchored increases energy generation in the first and second generators, as well as improving the longevity of the apparatus and making maintenance more straight-forward.

Optionally, the ballast is configured to be anchored to a surface below the water waves, such as a seabed.

Optionally, the ballast is configured to be anchored offshore. Advantageously, at offshore locations 20 water waves may be constant, thus the water wave energy which can be harnessed by the apparatus may be more consistent and/or of a higher magnitude.

Optionally, the ballast is anchored, for example to a submerged surface below the surface of the CV water waves, such as the sea bed.

Optionally, the first gear and the second gear are ratchet gears. Advantageously, the first gear being a ratchet gear allows continuous rotary motion in only the first direction while preventing motion in the second direction, and the second gear being a ratchet gear allows continuous rotary motion in only the second direction while preventing motion in the first direction. Furthermore, the first gear being a ratchet gear and only being able to move in the first direction, provides that the first flywheel continues to also rotate in the first direction only, thus providing the first generator with continuous energy, and the second gear being a ratchet gear and only being able to move in the second direction, provides that the second flywheel continues to also rotate in the second direction only, thus providing the second generator with continuous energy.

Also disclosed is a watercraft comprising the apparatus for generating energy from water waves. Advantageously, such a watercraft, for example a boat or ship, can generate energy as the watercraft moves up and down the wave crests, because this movement causes rotation of the ballast from side to side and it is this reciprocating motion that powers the first generator and the second generator. Furthermore, such a watercraft can use the energy generated by the first and second generator to power items and/or processes onboard the watercraft that require energy, thus providing for a more sustainable watercraft harnessing the power of renewable energy.

Optionally, the watercraft further comprises a mast comprising a central axis; wherein: the first body section is a coupling; the second body section is a hull comprising a longitudinal axis; the ballast is a keel; the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by the coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.

Advantageously, the mast and the keel being configured to rotate relative to the hull about the longitudinal axis of the hull and the mast being rotationally fixed relative to the keel provides that as the watercraft moves up and down a wave crest (for example, through a wave cycle) the mast and the keel can move in the first direction and the second direction, thus powering the first generator and the second generator. Additionally, as the mast and the keel are configured to rotate relative to C\J the hull, the hull advantageously remains level when the watercraft moves through a wave cycle, which can be more comfortable for any passengers onboard the watercraft. Advantageously, the coupling being configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast allows components to be placed between the mast and the keel, thus providing for a more compact, space-efficient watercraft. The line of action of the weight of the mast being arranged through the coupling provides that the line of action of the weight of the mast is diverted through the coupling away from the central axis of the mast. This advantageously provides that the mast can thus be less prone to mechanical failure, such as deformation and buckling.

Optionally, the watercraft further comprises a mast comprising a central axis; wherein: the first body section is a coupling; the second body section is a hull comprising a longitudinal axis; the ballast is a keel; the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by the coupling such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and at least a portion of the hull is arranged inside an internal volume of the coupling.

Advantageously, the mast and the keel being configured to rotate relative to the hull about the longitudinal axis of the hull and the mast being rotationally fixed relative to the keel provides that as the watercraft moves up and down a wave crest (for example, through a wave cycle) the mast and the keel can move in the first direction and the second direction, thus powering the first generator and the second generator. Additionally, as the mast and the keel are configured to rotate relative to the hull, the hull advantageously remains level when the watercraft moves through a wave cycle, which can be more comfortable for any passengers onboard the watercraft. Advantageously, the coupling being configured to have an internal volume allows components to be placed between the mast and the keel, thus providing for a more compact, space-efficient watercraft.

Optionally, the coupling is further configured to be coupled to the first gear and the second gear such that relative rotation between the coupling and the hull in the first direction drives the first generator and relative rotation between the coupling and the hull in the second direction drives the second generator.

Optionally, the coupling comprises a collar-like element. C\1

Optionally, the keel comprises a first keel element and a second keel element, wherein the first keel element and the second keel element are coupled to the coupling and are configured to protrude therefrom, the first keel element and the second keel element being spaced apart with respect to each other. Advantageously, the first keel element and the second keel element being spaced apart allows the watercraft to have a shallower draft (that is, the vertical distance between the waterline and the bottom of the hull) while still allowing for minimum leeway while sailing. The placement of the first keel element and the second keel element also allows the watercraft to stand upright when out of the water without additional support, since they can act as stabilisers, as opposed to a watercraft with a single keel element that might inadvertently fall over if water levels dropped.

Optionally, the first keel element and the second keel element are circumferentially spaced apart, about a perimeter, for example a circumference, of the coupling.

Optionally, the first keel element comprises a longitudinal axis and the second keel element comprises a longitudinal axis, wherein: the longitudinal axis of the first keel element is generally normal to the perimeter, for example a circumference, of the coupling; and the longitudinal axis of the second keel element is generally normal to the perimeter, for example a circumference, of the coupling.

Optionally, the first keel element and the second keel element define a twin keel or a bilge keel.

Advantageously, twin keels, or bilge keels, allow the watercraft to have a shallower draft (that is, the vertical distance between the waterline and the bottom of the hull) while still allowing for minimum leeway while sailing. The placement of the twin keel or bilge keel also allows the watercraft to stand upright when out of the water without additional support, since they can act as stabilisers, as opposed to a watercraft with a single keel that could inadvertently fall over if water levels dropped.

Optionally, the watercraft further comprises a sail, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.

Advantageously, the at least one blade comprising an aerofoil cross-sectional profile and being configured to provide a propulsive force allows the aerofoil cross-sectional profile to deflect the oncoming air which results in a force on the aerofoil cross-sectional profile in the direction opposite C\J to the deflection, which can thus propel the watercraft. Furthermore, the blades comprising a first rotational degree of freedom provides that the angle of attack of the aerofoil cross-sectional profile can be varied so as to provide varying directions of propulsive force to the watercraft. In addition, the blades comprising a second translational degree of freedom provides that the blades can be moved into a formation that results in an increased or decreased total surface area of the blades, thus increasing or decreasing the propulsive force to the watercraft respectively, as desired. Additionally, the blades having the first and second degrees of freedom provides that the watercraft can advantageously change course without having to tack (change course by turning the bow of the watercraft into and through the wind),Instead, the rotational and/or translational position of the at least one blade can be varied to change the course of the watercraft.

Optionally, each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally perpendicular to the longitudinal axis of the buoyant body; the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.

Optionally, the central axis of the mast is configured to be arranged with respect to the longitudinal axis of the buoyant body at an angle of between approximately 60 degrees and 90 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably between approximately 85 degrees and 90 degrees.

Optionally, the longitudinal axis of each of the at least one blades is configured to be arranged with respect to the longitudinal axis of the buoyant body at an angle of between approximately 60 degrees and 90 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably between approximately 85 degrees and 90 degrees.

Optionally, the apparatus for generating energy from water waves may additionally comprise any one or more of the optional features of the second, third, and fourth aspects of the disclosure as outlined below.

According to a second aspect of the disclosure, there is provided a watercraft comprising: a hull comprising a longitudinal axis; a mast comprising a central axis; and a keel; CV wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.

Advantageously, the mast and the keel being configured to rotate relative to the hull about the longitudinal axis of the hull and the mast being rotationally fixed relative to the keel provides that as the watercraft moves up and down a wave crest (for example, through a wave cycle) the mast and the keel can move in the first direction and the second direction, thus powering the first generator and the second generator. Additionally, as the mast and the keel are configured to rotate relative to the hull, the hull advantageously remains level when the watercraft moves through a wave cycle, which can be more comfortable for any passengers on board the watercraft. Advantageously, the coupling being configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast allows components to be placed between the mast and the keel, thus providing for a more compact, space-efficient watercraft. The line of action of the weight of the mast being arranged through the coupling provides that the line of action of the weight of the mast is diverted through the coupling away from the central axis of the mast. This advantageously provides that the mast can thus be less prone to mechanical failure, such as deformation and buckling.

Optionally, the line of action of the weight of the mast is diverted through the coupling and is offset from the central axis of the mast. Advantageously, the mast can thus be less prone to mechanical failure, such as deformation and buckling.

Optionally, the longitudinal axis of the hull and the central axis of the mast are arranged in planes that are generally perpendicular to one another.

Optionally, the mast and the keel are configured to rotate relative to the hull only about the longitudinal axis of the hull. Advantageously, the mast and the keel rotating only about the longitudinal axis of the hull, and not, for example, in other directions such as about a pitch axis of the watercraft (towards the bow and the stern of the watercraft), reduces the risk of mechanical failure of the mast, the keel, and/or the coupling as the mast and the keel cannot be suddenly inadvertently rotated in different directions by the water waves.

c\I Optionally, the coupling comprises a generally cylindrical portion, such that at least a portion of the line of action of the weight of the mast is arranged through a first section and a second section of the generally cylindrical portion of the coupling, wherein the first section and the second section are diametrically opposed. Advantageously, at least a portion of the line of action of the weight of the mast being arranged through the first and second sections of the generally cylindrical portion provides that the mast can thus be less prone to mechanical failure, such as deformation and buckling.

Optionally, the coupling and the hull are arranged to be concentric with respect to one another. Advantageously, this allows the coupling and the hull to rotate about the same axis, that is, for them to share a common rotational axis corresponding to the longitudinal axis of the hull.

Optionally, at least a portion of the coupling is arranged inside the hull.

Optionally, the hull at least partially surrounds the coupling.

Optionally, at least a portion of the hull is arranged inside an internal volume of the coupling. Advantageously, the coupling being configured to have an internal volume allows components to be placed between the mast and the keel, such as at least a portion of the hull, thus providing for a more compact, space-efficient watercraft.

Optionally, the coupling is configured to surround the hull.

Optionally, the keel comprises a first keel element and a second keel element, wherein the first keel element and the second keel element are coupled to the coupling and are configured to protrude therefrom, the first keel element and the second keel element being spaced apart with respect to each other. Advantageously, the first keel element and the second keel element being spaced apart allows the watercraft to have a shallower draft (that is, the vertical distance between the waterline and the bottom of the hull) while still allowing for minimum leeway while sailing. The placement of the first keel element and the second keel element also allows the watercraft to stand upright when out of the water without additional support, since they can act as stabilisers, as opposed to a watercraft with a single keel element that could fall over if water levels dropped.

Optionally, the first keel element and the second keel element are circumferentially spaced apart about a perimeter, for example a circumference, of the coupling.

Optionally, the first keel element comprises a longitudinal axis and the second keel element comprises a longitudinal axis, wherein: the longitudinal axis of the first keel element is generally normal to the perimeter, for example a circumference, of the coupling; and the longitudinal axis of CV the second keel element is generally normal to the perimeter, for example a circumference, of the coupling.

Optionally, the first keel element and the second keel element define a twin keel or a bilge keel. Advantageously, twin keels, or bilge keels, allow the watercraft to have a shallower draft (that is, the vertical distance between the waterline and the bottom of the hull) while still allowing for minimum leeway while sailing. The placement twin keel or bilge keel also allows the watercraft to stand upright when out of the water without additional support, since they can act as stabilisers, as opposed to a watercraft with a single keel that could fall over if water levels dropped.

Optionally, the keel comprises a propulsion system. Advantageously, the propulsion system may provide a steering effect, such as a differential steering effect, to the watercraft, such that the watercraft may be propelled through the water and/or directed to point the watercraft into the desired direction.

Optionally, the watercraft further comprises an apparatus for generating energy from water waves, wherein the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull both in a first direction and a second direction, the second direction being opposite to the first direction; the apparatus for generating energy from water waves comprising an energy generation 10 system, comprising: a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in the first direction only and the second gear is configured to rotate in the second direction only; wherein the mast and the keel are coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the mast and the keel to the first generator, such that relative rotation between the mast and the keel, and the hull in the first direction drives the first generator; and wherein the mast and the keel are coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define 20 a second drive path from the mast and the keel to the second generator, such that relative rotation between the mast and the keel, and the hull in the second direction drives the second generator.

Advantageously, the relative rotation between the keel and the hull in both the first direction and the CV opposite second direction allows the apparatus to generate energy throughout the whole water wave cycle, thus generating more energy per water wave cycle. This is because water waves are typically sinusoidal and have both positive and negative amplitudes, with the wave crests having positive amplitude and the wave troughs having negative amplitude. Therefore, as the water wave passes along the longitudinal axis of the hull, it causes points along the longitudinal axis to rise as the wave crest passes through the point and fall as the wave trough passes through the point, and, hence, providing for relative rotation between the ballast and the second body section in two directions facilitates that the apparatus can harness the power of the waves throughout the entire cycle, and thus generate more energy therefrom. Furthermore, the first drive path and the second drive path comprise few parts, thus increasing the efficiency of power generation as fewer energy conversions need to be made. Additionally, a watercraft comprising the apparatus can use the energy generated by the first and second generator to power items and/or processes on the watercraft that require energy.

Optionally, the coupling is configured to rotate relative to the hull about the longitudinal axis of the hull in both the first direction and the second direction, wherein the coupling is further configured to be coupled to the first gear and second gear such that relative rotation between the coupling and the hull in the first direction drives the first generator and relative rotation between the coupling and the hull in the second direction drives the second generator.

Optionally, the watercraft further comprises a sail, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a 10 second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.

Advantageously, the at least one blade comprising an aerofoil cross-sectional profile and being configured to provide a propulsive force allows the aerofoil cross-sectional profile to deflect the oncoming air which results in a force on the aerofoil cross-sectional profile in the direction opposite to the deflection, which can thus propel the watercraft. Furthermore, the blades comprising a first rotational degree of freedom provides that the angle of attack of the aerofoil cross-sectional profile can be varied so as to provide varying directions of propulsive force to the watercraft. In addition, the blades comprising a second translational degree of freedom provides that the blades can be moved into a formation that results in an increased or decreased total surface area of the blades, thus increasing or decreasing the propulsive force to the watercraft respectively, as desired. Additionally, the blades having the first and second degrees of freedom provides that the watercraft can C\J advantageously change course without having to tack (change course by turning the bow of the watercraft into and through the wind). Instead, the rotational and/or translational position of the at least one blade can be varied to change the course of the watercraft.

Optionally, each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally perpendicular to the longitudinal axis of the hull; wherein the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and wherein the longitudinal axis of the support is generally perpendicular to the central axis of 35 the mast and the longitudinal axis of each of the at least one blades.

Optionally, the central axis of the mast is configured to be arranged with respect to the longitudinal axis of the hull at an angle of between approximately 60 degrees and 90 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably between approximately 85 40 degrees and 90 degrees.

Optionally, the longitudinal axis of each of the at least one blades is configured to be arranged with respect to the longitudinal axis of the hull at an angle of between approximately 60 degrees and 90 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably 5 between approximately 85 degrees and 90 degrees.

Optionally, the watercraft may additionally comprise any one or more of the optional features of the first, third, and fourth aspects of the disclosure outlined herein.

According to a third aspect of the disclosure, there is provided a watercraft comprising: a hull comprising a longitudinal axis; a mast; and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and at least a portion of the hull is arranged inside an internal volume of the coupling.

c\I Advantageously, the mast and the keel being configured to rotate relative to the hull about the longitudinal axis of the hull and the mast being rotationally fixed relative to the keel provides that as the watercraft moves up and down a wave crest (for example, through a wave cycle) the mast and the keel can move in the first direction and the second direction, thus powering the first generator and the second generator. Additionally, as the mast and the keel are configured to rotate relative to the hull, the hull advantageously remains level when the watercraft moves through a wave cycle, which can be more comfortable for any passengers on board the watercraft. Advantageously, the coupling being configured to have an internal volume allows components to be placed between the mast and the keel, thus providing for a more compact, space-efficient watercraft.

Optionally, at least a portion of the coupling is generally cylindrical, and at least a portion of the hull is generally cylindrical.

Optionally, the first keel element and the second keel element define a twin keel or a bilge keel. Advantageously, twin keels, or bilge keels, allow the watercraft to have a shallower draft (that is, the vertical distance between the waterline and the bottom of the hull) while still allowing for minimum leeway while sailing. The placement of the twin keel or bilge keel also allows the watercraft to stand upright when out of the water without additional support, since they can act as stabilisers, as opposed to a watercraft with a single keel that could fall over if water levels dropped.

Optionally, the keel comprises a propulsion system. Advantageously, the propulsion system may provide a steering effect, such as a differential steering effect, to the watercraft such that the watercraft may be propelled through the water and/or directed to point the watercraft into the desired direction.

Optionally, the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast. Advantageously, the coupling being configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast allows components to be placed between the mast and the, thus providing for a more compact, space-efficient watercraft. The line of action of the weight of the mast being arranged through the coupling provides that the line of action of the weight of the mast is diverted through the coupling away from the central axis of the mast. This provides that the mast can thus be less prone to mechanical failure, such as deformation and buckling.

Optionally, the watercraft further comprises an apparatus for generating energy from water waves, wherein the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull both in a first direction and a second direction, the second direction being opposite to the first direction; the apparatus for generating energy from water waves comprising an energy generation 20 system, comprising a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in the first direction only and the second gear is configured to rotate in the second direction only; C\J wherein the mast and the keel are coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the keel to the first generator, such that relative rotation between the mast and the keel, and the hull in the first direction drives the first generator; and wherein the mast and the keel are coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define 30 a second drive path from the mast and the keel to the second generator, such that relative rotation between the mast and the keel, and the hull in the second direction drives the second generator.

Advantageously, the relative rotation between the keel and the hull in both the first direction and the opposite second direction allows the apparatus to generate energy throughout the whole water wave cycle, thus generating more energy per water wave cycle. This is because water waves are typically sinusoidal and have both positive and negative amplitudes, with the crests of the waves having positive amplitude and the wave troughs having negative amplitude. Therefore, as the water wave passes along the longitudinal axis of the hull, it causes points along the longitudinal axis to rise as the wave crest passes through the point and fall as the wave trough passes through the point, and, hence, providing for relative rotation between the ballast and the second body section in two directions facilitates that the apparatus can harness the power of the waves throughout the entire cycle, and thus generate more energy therefrom. Furthermore, the first drive path and the second drive path comprise few parts, thus increasing the efficiency of power generation as fewer energy conversions need to be made. Furthermore, a watercraft comprising the apparatus can use the energy generated by the first and second generator to power items and/or processes on the watercraft that require energy.

Optionally, the watercraft further comprises a sail, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a 20 second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.

c\I Advantageously, the at least one blade comprising an aerofoil cross-sectional profile and being configured to provide a propulsive force allows the aerofoil cross-sectional profile to deflect the oncoming air which results in a force on the aerofoil cross-sectional profile in the direction opposite to the deflection, which can thus propel the watercraft. Furthermore, the blades comprising a first rotational degree of freedom provides that the angle of attack of the aerofoil cross-sectional profile can be varied so as to provide varying directions of propulsive force to the watercraft. In addition, the blades comprising a second translational degree of freedom provides that the blades can be moved into a formation that results in an increased or decreased total surface area of the blades, thus increasing or decreasing the propulsive force to the watercraft respectively, as desired. Additionally, the blades having the first and second degrees of freedom provides that the watercraft can advantageously change course without having to tack (change course by turning the bow of the watercraft into and through the wind). Instead the rotational and/or translational position of the at least one blade can be varied to change the course of the watercraft.

Optionally, the mast comprises a central axis; each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally perpendicular to the longitudinal axis of the hull; wherein the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and wherein the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.

Optionally, the central axis of the mast is configured to be arranged with respect to the longitudinal axis of the hull at an angle of between approximately 60 degrees and 90 degrees, more preferably 10 between approximately 75 degrees and 90 degrees, more preferably between approximately 85 degrees and 90 degrees.

Optionally, the longitudinal axis of each of the at least one blades is configured to be arranged with respect to the longitudinal axis of the hull at an angle of between approximately 60 degrees and 90 15 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably between approximately 85 degrees and 90 degrees.

Optionally, the watercraft may additionally comprise any one or more of the optional features of the first, second, and fourth aspects of the disclosure as outlined herein.

According to a fourth aspect of the disclosure, there is provided a sail for a watercraft, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; CV wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.

Advantageously, the at least one blade comprising an aerofoil cross-sectional profile and being configured to provide a propulsive force allows the aerofoil cross-sectional profile to deflect the oncoming air which results in a force on the aerofoil cross-sectional profile in the direction opposite to the deflection, which can thus propels the watercraft. Furthermore, the blades comprising a first rotational degree of freedom provides that the angle of attack of the aerofoil cross-sectional profile can be varied so as to provide varying directions of propulsive force to the watercraft. In addition, the blades comprising a second translational degree of freedom provides that the blades can be moved into a formation that results in an increased or decreased total surface area of the blades, thus increasing or decreasing the propulsive force to the watercraft respectively, as desired. Thus, advantageously the blades having the first and second degrees of freedom provides that the watercraft can change course without having to tack (change course by turning the bow of the watercraft into and through the wind). Instead, the rotational and/or translational position of the at least one blade can be varied to change the course of the watercraft.

Optionally, each of the at least one blades is arranged with respect to the watercraft so as to provide a propulsive force to the watercraft.

Optionally, the at least one blade comprises a plurality of blades and the one or more guide means are configured to support the plurality of blades such that at least one of the plurality of blades is movable with respect to at least another one of the plurality of blades in the first rotational degree of freedom and/or in the second translational degree of freedom. Advantageously, the plurality of blades being moveable in the first rotational degree of freedom provides that the angle of attack of the aerofoil cross-sectional profile can be varied so as to provide varying directions of propulsive force to the watercraft. In addition, the plurality of blades being moveable in the second translational degree of freedom provides that the blades can be moved into a formation that results in an increased or decreased total surface area of the blades, thus increasing or decreasing the propulsive force to the watercraft respectively, as desired. Thus advantageously, at least one of the plurality of blades being movable with respect to at least another one of the plurality of blades in the first and second degrees of freedom provides that the watercraft can change course without having to tack (change course by turning the bow of the watercraft into and through the wind). Instead, the rotational and/or translational position of at least one of the plurality of blades can be varied to change the course of the watercraft. C\J

Optionally, the sail comprises a plurality of said supports, and the plurality of blades comprises a plurality of sets of blades, each support being configured to support one of the sets of blades. Advantageously, each support being configured to support one of the sets of blades provides that each set of blades can be supported and guided independently of the other sets of blades. This provides for an adaptable sail that can utilise differing numbers of sets of blades dependent on the wind at sea.

Optionally, the plurality of supports are configured to support one of the sets of blades at a first end of the set of blades and a second end of the set of blades. Advantageously, this provides greater stability and support to the sets of blades as they are supported from both ends. which reduces the risk of mechanical failure.

Optionally, at least one of the at least one blades is configured to rotate relative to the support.

Optionally, at least one of the at least one blades comprises a first axis, said blade being configured to rotate relative to the support about said first axis.

Optionally, at least one of the at least one blades, for example, each of the blades, comprises a first portion and a second portion, wherein the second portion is configured to be movable relative to the first portion. Advantageously, the second portion being configured to move relative to the first portion varies the shape of at least one of the at least one blades, thus varying the surface area available for the oncoming air to hit so as to vary the direction of the propulsive force to the watercraft.

Optionally, said at least one of the at least one blades, for example, each of the blades, comprises a first axis, wherein the second portion is configured to rotate relative to the first portion about the first axis. Advantageously, the second portion being configured to rotate relative to the first portion about the first axis varies the shape of at least one of the at least one blades, thus varying the surface area available for the oncoming air to hit so as to vary the direction of the propulsive force to the watercraft.

Optionally, the second portion is configured to flex relative to the first portion.

Optionally, the first axis is arranged to be generally normal to the aerofoil cross-sectional profile of said at least one of the at least one blades.

Optionally, the first portion is rotationally fixed relative to the support, and wherein the second portion is configured to rotate relative to the first portion and relative to the support. Advantageously, the second portion being configured to rotate relative to the first portion and the support varies the shape of at least one of the at least one blades, thus varying the surface area available for the oncoming air to hit so as to vary the direction of the propulsive force to the watercraft. C\J

Optionally, each of the blades comprises an angle of attack which determines the direction of said propulsive force, wherein movement of said at least one blade in the first rotational degree of freedom is configured to vary the angle of attack. Advantageously, the first rotational degree of freedom being configured to vary angle of attack provides that the direction of the watercraft can be controlled by varying the angle of attack of at least one blade.

Optionally, the first portion of the blade comprises a leading edge of the aerofoil cross-sectional profile and the second portion of the blade comprises a trailing edge of the aerofoil cross-sectional profile, such that movement of the second portion relative to the first portion is configured to change the angle of attack of the blade. Advantageously, movement of the second portion relative to the first portion is configured to change the angle of attack of the blade provides that the direction of the watercraft can be controlled by varying the angle of attack of at least one blade.

Optionally, the first portion comprises a first rigid surface that defines the leading edge, and the second portion comprises a second rigid surface that defines the trailing edge. Advantageously, the first and second portions each comprising rigid surfaces provides a more efficient lift to drag ratio than conventional soft sails.

Optionally, the trailing edge is configured to flex relative to the leading edge.

Optionally, the one or more guide means comprises one or more channels or apertures arranged in the support.

Optionally, the one or more guide means comprise elongate channels within which the at least one blade is configured to be received and move within.

Optionally, the sail further comprises an actuator means configured to actuate the movement of said at least one of the at least one blades in the first rotational degree of freedom and the second translational degree of freedom.

Optionally, the actuator means comprise a motor, such as a high torque planet geared motor. Optionally, the sail further comprises a control means configured to control the actuator means.

Optionally, one or more of the blades of the sail may at least partially be covered with or may 20 otherwise comprise one or more solar panel elements. For example, one or more of the blades may be covered with flexible solar panels, such as 100 Waft 12 Volt flexible monocrystalline solar panels.

Optionally, the sail for a watercraft further comprises a mast, wherein the support is coupled to the CV mast and is arranged to extend therefrom in a generally perpendicular direction. Advantageously, the mast provides increased stability to the sail.

Optionally, the mast comprises a central axis about which the support is configured to rotate. Advantageously, the support being configured to rotate about the central axis of the mast allows the surface area of the at least one blades that is hit by the oncoming air to be varied, and therefore the magnitude of the propulsive force to the watercraft can be varied.

Optionally, each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.

Optionally, the support is further configured such that each of the at least one blades are arranged laterally with respect to each other.

Also disclosed is a watercraft comprising the sail, and a hull comprising a longitudinal axis and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull.

Advantageously, the mast and the keel being configured to rotate relative to the hull about the longitudinal axis of the hull and the mast being rotationally fixed relative to the keel provides that as the watercraft moves up and down a wave crest (for example, through a wave cycle) the mast and the keel can move in a first direction and a second direction allowing the hull to advantageously remain level, which can be more comfortable for any passengers on board the watercraft.

Also disclosed is a watercraft comprising the sail, and a hull comprising a longitudinal axis and a keel; wherein: C\J the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.

Also disclosed is a watercraft comprising the sail, a hull comprising a longitudinal axis, and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and at least a portion of the hull is arranged inside an internal volume of the coupling.

Advantageously, the mast and the keel being configured to rotate relative to the hull about the longitudinal axis of the hull and the mast being rotationally fixed relative to the keel provides that as the watercraft moves up and down a wave crest (for example, through a wave cycle) the mast and the keel can move in the first direction and the second direction, thus powering the first generator CV and the second generator. Additionally, as the mast and the keel are configured to rotate relative to the hull, the hull advantageously remains level when the watercraft moves through a wave cycle, which can be more comfortable for any passengers on board the watercraft. Advantageously, the coupling being configured to have an internal volume allows components to be placed between the mast and the keel, thus providing for a more compact, space-efficient watercraft.

Also disclosed is an apparatus for generating energy from water waves comprising: the sail as claimed in any preceding claim; a buoyant body comprising a first body section and a second body section, wherein the buoyant body comprises a longitudinal axis; and a ballast, wherein the ballast and the first body section are configured to rotate relative to the second body section about said longitudinal axis both in a first direction and a second direction, the second direction being opposite to the first direction; wherein the sail protrudes from the buoyant body so as to provide a propulsive force to the buoyant body; wherein the ballast is rotationally fixed relative to the first body section such that rotation of 40 the first body section relative to the second body section about said longitudinal axis causes the ballast to rotate relative to the second body section about said longitudinal axis, and such that rotation of the ballast relative to the second body section about said longitudinal axis causes the first body section to rotate relative to the second body section about said longitudinal axis; an energy generation system, comprising: a first gear and a second gear, a first flywheel and 5 a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in a first direction only and the second gear is configured to rotate in a second direction only; wherein the ballast is coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the ballast to the first generator, such that relative rotation between the ballast and the second body section in the first direction drives the first generator; and wherein the ballast is coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define a second drive path from the ballast to the second generator, such that relative rotation between the ballast and the 15 second body section in the second direction drives the second generator.

Advantageously, the relative rotation between the ballast and the second body section in both the first direction and the opposite second direction allows the apparatus to generate energy throughout the whole water wave cycle, thus generating more energy per water wave cycle. This is because water waves are typically sinusoidal and have both positive and negative amplitudes, with the crests of the waves having positive amplitude and the wave troughs having negative amplitude. Therefore, as the water wave passes along the longitudinal axis of the buoyant body, it causes points along the longitudinal axis to rise as the wave crest passes through the point and fall as the wave trough passes CV through the point, and, hence, providing for relative rotation between the ballast and the second body section in two directions facilitates that the apparatus can harness the power of the waves throughout the entire cycle, and thus generate more energy therefrom. Furthermore, the first drive path and the second drive path comprise few parts, thus increasing the efficiency of power generation as fewer energy conversions need to be made.

Optionally, the sail for a watercraft may additionally comprise any one or more of the optional features of the first, second, and third aspects of the disclosure as outlined above.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be carried out in various ways and embodiments of the disclosure will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic front view of a preferred embodiment of an apparatus for generating energy from water waves according to a first embodiment of the present disclosure.

Figure 2 is an enlarged front, cross-sectional view of half of an energy generation system of the apparatus for generating energy from water waves of Figure 1.

Figure 3A is a schematic side view of a preferred embodiment of an apparatus for generating energy 5 from water waves according to a second embodiment of the present disclosure, in which the ballast is anchored.

Figure 3B is a schematic side view of the apparatus of Figure 3A at a first point in a wave cycle.

Figure 3C is a schematic side view of the apparatus of Figure 3A at a second point in a wave cycle.

Figure 3D is a schematic side view of the apparatus of Figure 3A at a third point in a wave cycle.

Figure 4A is a schematic front, cross-sectional view of a preferred embodiment of a watercraft according to a third embodiment of the present disclosure.

Figure 4B is a schematic side, cross-sectional view of an energy generation system of the watercraft of Figure 4A.

Figure 4C is a schematic front view of an energy generation system of the watercraft of Figure 4A.

Figure 5 is a perspective view of the watercraft of Figure 4A.

c\I Figure 6A is a schematic front, cross-sectional view of a preferred embodiment of a watercraft according to a fourth embodiment of the present disclosure.

Figure 6B is a schematic side view of the watercraft of Figure 6A.

Figure 7A is a schematic front view of an energy generation system of the watercraft of Figure 6A.

Figure 7B is a schematic side view of a section of the watercraft of Figure 6A, with a transparent portion, to show the energy generation system.

Figure 7C is a schematic front view of an energy generation system of the watercraft of Figure 6A at a first point in a wave cycle.

Figure 7D is a schematic front view of an energy generation system of the watercraft of Figure 6A at a second point in a wave cycle.

Figure 7E is a schematic front view of an energy generation system of the watercraft of Figure 6A at a third point in a wave cycle.

Figure 7F is a schematic front view of an energy generation system of the watercraft of Figure 6A at a fourth point in a wave cycle.

Figure 8A is a schematic side view of a preferred embodiment of a sail for a watercraft according to a fifth embodiment of the present disclosure in a first sail configuration.

Figure 8B is a schematic side view of the sail of Figure 8A in a second sail configuration.

Figure 8C is a schematic side view of the sail of Figure 8A in a third sail configuration.

Figure 8D is a schematic side view of the sail of Figure 8A in a fourth sail configuration.

Figure 9A is a schematic plan view of a preferred embodiment of a sail for a watercraft according to a sixth embodiment of the present disclosure in a first blade configuration and a first support configuration.

Figure 9B is a schematic plan view of the sail of Figure 9A in a second blade configuration and a second support configuration.

Figure 9C is a schematic plan view of the sail of Figure 9A in a third blade configuration and a third CV support configuration.

Figure 9D is a schematic plan view of the sail of Figure 9A in a fourth blade configuration and a fourth support configuration.

Figure 10A is a schematic plan view of a preferred embodiment of a sail for a watercraft according 30 to a seventh embodiment of the present disclosure in a first blade configuration.

Figure 10B is a schematic plan view of the sail of Figure 10A in a second blade configuration.

Figure 10C is a schematic plan view of the sail of Figure 10A in a third blade configuration.

Figure 10D is a schematic plan view of a blade of the sail of Figure 10A in a straight configuration.

Figure 10E is a schematic plan view of a blade of the sail of Figure 10A in a flexed configuration.

DETAILED DESCRIPTION

An apparatus 1 for generating energy from water waves 2 is shown in schematic front, cross-sectional view in Figure 1 and an enlarged front, cross-sectional view of a portion of the apparatus 1 is shown in Figure 2. The apparatus 1 comprises a buoyant body 3, with the buoyant body 3 comprising a longitudinal axis 6, a first body section 4 and a second body section 5. The buoyant body 3 has a first end 28 (shown in Figure 3) and a second end 29 (shown in Figure 3), where the first end 28 is configured to point into the direction of the oncoming water waves 2 and the second end 29 is configured to point away from the direction of the oncoming water waves 2.

The first body section 4 and the second body section 5 are arranged to be concentric with respect to one another, and in the example illustrated in Figure 1, the first body section 4 is arranged inside the second body section 5 such that the first body section 4 is an inner body section of the buoyant body 3 and the second body section 5 is an outer body section of the buoyant body 3. The first body section 4 and the second body section 5 are both generally cylindrical, however it is envisaged that 15 the first body section 4 and the second body section 5 may be any other suitable shape, such as generally rectangular.

The apparatus 1 further comprises a ballast 7 that is coupled to the first body section 4. The ballast 7 comprises an elongate element 19 and a base element 20, the elongate element 19 comprises a first end 21 and a second end 22, and a length 23, with the first end 21 of the elongate element 19 being spaced apart from the second end 22 of the elongate element 19 along the length 23 of the elongate element 19. The elongate element 19 is configured to protrude from, or extend from, the first body section 4. The first end 21 is coupled to the first body section 4 and the second end 22 is CV coupled to the base element 20. The elongate element 19 is coupled to the first body section 4 at the midpoint of the length of the first body section 4 and at the midpoint of the width of the first body section 4. However, it is also envisaged that the ballast 7 may be not coupled to the first body section 4 at a midpoint of the length or width of the first body section 4, and may be coupled to the first body section 4 at any other suitable location. The base element 20 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 20 may be generally cuboidal, hexagonal or any other suitable shape. The base element 20 is a substantially heavy body and thus acts as a heave plate. Advantageously, the heave plate contributes added stability to the apparatus 1 by shifting the resonance periods of the apparatus 1 out of the predominant wave periods and damping the motion of the apparatus 1.

It is also envisaged that the ballast 7 may have more than one elongate element 19, such as two elongate elements 19 (as shown in Figure 4B). As described above, each elongate element 19 comprises a first end 21 and a second end 22, and a length 23, the first end 21 of the elongate element 19 being spaced apart from the second end 22 of the elongate element 19 along the length 23 of the elongate element 19. Each elongate element 19 may protrude from, or extend from, the first body section 4. The first end 21 of each elongate element 19 may be coupled to the first body section 4 and the second end 22 of each elongate element 19 may be coupled to the base element 20. Each elongate element 19 may be coupled to the first body section 4 such that they are spaced apart along the longitudinal axis 6 of the buoyant body and aligned in the same plane, so that when the apparatus 1 viewed from the first end 28 or the second end 29 of the buoyant body 3, only one of the elongate elements 19 is visible (as shown in Figure 4A and 4B for example). The base element 20 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 20 may be generally cuboidal, hexagonal or any other suitable shape.

Alternatively, the ballast 7 may comprises a first ballast element and a second ballast element (as shown in Figure 7A and 7B to 7F), where the first and second ballast elements are circumferentially spaced apart from each other about a perimeter of the first body section. The first and second ballast elements each comprise a longitudinal axis, where the longitudinal axis of the first ballast element is generally normal to the perimeter of the first body section and the longitudinal axis of the second ballast element is also generally normal to the perimeter of the first body section. The first ballast element and the second ballast element each comprise an elongate element 19, each elongate element 19 comprising a first end 21, a second end 22, and a length 23, the first end 21 being spaced apart from the second end 22 along the length 23 of the elongate element 19. The elongate element 19 protrudes from, or extends from, the first body section 4. The first end 21 is coupled to the first body section 4 and the second end 22 is coupled to the base element 20. The base element 20 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 20 may be generally cuboidal, hexagonal or any other suitable shape.

CV During the use of the apparatus 1, the ballast 7 is submerged below the surface of the water waves 2, such that the elongate element 19 and the base element 20 are arranged below the surface of the water waves 2. For example, the base element 20 may be arranged between approximately 8 metres to 16 metres below the surface of the water waves 2, more preferably between approximately 10 metres to 14 metres below the surface of the water waves 2, more preferably approximately 12 metres below the surface of the water waves 2. The ballast 7 being submerged underwater contributes added stability to the apparatus by shifting the resonance periods of the apparatus 1 out of the predominant wave periods and damping the motion of the apparatus 1.

The ballast 7 and the first body section 4 are configured to rotate relative to the second body section 5 about the longitudinal axis 6 of the buoyant body 3 in both a first direction 8 (shown in Figure 3A) and a second direction 9 (shown in Figure 3A), the second direction 9 being opposite to the first direction 8. Relative rotation between the ballast 7 and the second body section 5 in both the first direction 8 and the opposite second direction 9 allows the apparatus 1 to generate energy throughout the whole water wave cycle, thus generating more energy per water wave cycle. The first direction 8 is clockwise when viewed along the longitudinal axis 6 of the buoyant body 3 from the first end 28 or the second end 29 of the buoyant body 3 and the second direction 9 is anti-clockwise when viewed along the longitudinal axis 6 of the buoyant body 3 from the same one of the first end 28 or the second end 29 of the buoyant body 3.

The ballast 7 is rotationally fixed relative to the first body section 4 such that rotation of the first body 5 section 4 relative to the second body section 5 about the longitudinal axis 6 of the buoyant body 3 causes the ballast 7 to rotate relative to the second body section 5 about the longitudinal axis 6 of the buoyant body 3, and rotation of the ballast 7 relative to the second body section 5 about the longitudinal axis 6 of the buoyant body 3 causes the first body section 4 to rotate relative to the second body section 5 about the longitudinal axis 6 of the buoyant body 3. In the example illustrated 10 in Figure 3, the second body section 5 comprises an aperture 32 through which the ballast 7 protrudes from the first body section 4. The aperture 32 is configured so as to allow the first body section 4 and the ballast 7 to rotate relative to the second body section 5 about the longitudinal axis 6 of the buoyant body 3.

The apparatus 1 further comprises an energy generation system 10 configured to generate energy from water waves 2. In the example illustrated in Figures 1 and 2, the energy generation system 10 is arranged inside the first body section 4 and in turn, is thus also arranged inside the second body section 5. The energy generation system 10 is hermetically sealed inside the first body section 4 inside a cylindrical chamber 18 so as to protect the energy generation system 10 from water ingress and other potential damage from the water waves 2 and foreign object debris. In the example illustrated, the cylindrical chamber 18 comprises structural ribs 30 configured to provide strength and support to the cylindrical chamber 18.

CV The energy generation system 10 comprises a first gear 11 and a second gear 12, a first flywheel 13 and a second flywheel 14, and a first generator 15 and a second generator 16. The first generator 15 and the second generator 16 are each configured to generate electrical energy. Advantageously, the first generator 15 and second generator 16 generating electrical energy provides a sustainable source of electrical energy that does not use finite resources. The first gear 11 and the second gear 12, and the first flywheel 13 and the second flywheel 14 are each configured to rotate about an energy generation system rotational axis 17. The first gear 11 and the second gear 12 are ratchet gears, hence the first gear 11 is configured to rotate about the energy generation system rotational axis 17 in the first direction 8 only and the second gear 12 is configured to rotate about the energy generation system rotational axis 17 in the second direction 9 only. Correspondingly, the first flywheel 13 is configured to rotate about the energy generation system rotational axis 17 in the first direction 8 only and the second flywheel 14 is configured to rotate about the energy generation system rotational axis 17 in the second direction 9 only.

The first generator 15 comprises a first generator central axis 33 and the second generator 16 comprises a second generator central axis 34. In the example illustrated, the axes 33 and 34 are parallel to and offset from the energy generation system rotational axis 17 and from one another.

It is though also envisaged that the first generator central axis 33 and the second generator central axis 34 may be arranged to be coincident with each other, parallel to, and offset from the energy generation system rotational axis 17. Alternatively, the first generator central axis 33, the second generator central axis 34 and the energy generation system rotational axis 17 may be all coincident with each other.

The first gear 11 is coupled to the first flywheel 13, and the first flywheel 13 is coupled to the first generator 15, such that a first drive path is defined from the first gear 11 to the first generator 15.

The second gear 12 is coupled to the second flywheel 14, and the second flywheel 14 is coupled to the second generator 16, such that a second drive path is defined from the second gear 12 to the second generator 16. The ballast 7 is also coupled to the first gear 11 so as to form a part of the first drive path, such that relative rotation between the ballast 7 and the second body section 5 in the first direction 8 drives the first generator 15. The ballast 7 is also coupled to the second gear 12 so as to form a part of the second drive path, such that relative rotation between the ballast 7 and the second body section 5 in the second direction 9 drives the second generator 16. The first and second drive path comprise few parts, therefore increasing the efficiency of power generation as fewer energy conversions need to be made. The first flywheel 13 and the second flywheel 14 are configured to store rotational energy such that when the ballast 7 rotates in the second direction 9, the first flywheel 13 continues to rotate in the first direction 8 thus continuing to power the first generator 15 even when the first gear 11 is not being rotated and when the ballast 7 rotates in the first direction 8, the second flywheel 14 continues to rotate in the second direction 9 thus continuing to power the second generator 16 even when the second gear 12 is not being rotated. C\J

The first body section 4 is coupled to the second body section 5 by a first shaft 35 and a second shaft 36, the first shaft 35 and the second shaft 36 each comprise a longitudinal axis about which they rotate. The longitudinal axis of the first 35 and second 36 shaft is coincident with the energy generation system rotational axis 17 and the longitudinal axis 6 of the buoyant body 3. The first shaft 35 is coupled to the first gear 11 such that rotation of the first shaft 35 about the longitudinal axis 6 of the buoyant body 3 in the first direction 8 rotates the first gear 11 in the first direction 8 and as such drives the first generator 15, and the second shaft 36 is coupled to the second gear 12 such that rotation of the second shaft 36 about the longitudinal axis 6 of the buoyant body 3 in the second direction 9 rotates the second gear 12 in the second direction 9 and as such drives the second generator 16. The first shaft 35 and the second shaft 36 each comprise a series of bearings 31 configured to assist the rotation of the first shaft 35 in the first direction 8 and assist the rotation of the second shaft 36 in the second direction 9.

Alternatively, it is envisaged that the first body section 4 may be coupled to the second body section 5 by a collar-like element (see for example 238 in Figure 6A and Figure 6B). The collar-like element may be generally cylindrical and arranged to be concentric with respect to the first body section 4.

The first body section 4 may be arranged inside the collar-like element such that the collar-like element surrounds at least a portion of the first body section 4. The collar-like element is coupled to the first gear 11 such that rotation of the collar-like element about the longitudinal axis 6 of the buoyant body 3 in the first direction 8 rotates the first gear 11 in the first direction 8 and as such drives the first generator 13, and the collar-like element is coupled to the second gear 12 such that rotation of the collar-like element about the longitudinal axis 6 of the buoyant body 3 in the second direction 9 rotates the second gear 12 in the second direction 9 and as such drives the second generator 16.

The first flywheel 13 is coupled to the first generator 15 by a first generator coupling 39. In some embodiments, the first generator coupling 39 may comprise a series of generator gears configured so as to increase the gear ratio such that the generator gear that is coupled to the first generator 15 is configured to spin faster than the generator gear that is coupled to the first flywheel 13. Advantageously, this increases the energy generated by the first generator 15. Alternatively, the first generator coupling 39 may comprise a first generator gear that is coupled to the first flywheel 13 and a second generator gear that is coupled to the first generator 15, the first generator gear and the second generator gear being coupled together by a belt, such that rotation of the first generator gear causes rotation of the second generator gear. Advantageously, this arrangement is lightweight, and the two generator gears are able to be separated by a distance.

Similarly, the second flywheel 14 is coupled to the second generator 16 by a second generator coupling 40. In some embodiments, the second generator coupling 40 may comprise a series of generator gears configured so as to increase the gear ratio such that the generator gear that is C\J coupled to the second generator 16 is configured to spin faster than the generator gear that is coupled to the second flywheel 14. Advantageously, this increases the energy generated by the second generator 16. Alternatively, the second generator coupling 40 may comprise a first generator gear that is coupled to the second flywheel 14 and a second generator gear that is coupled to the second generator 16, the first generator gear and the second generator gear being coupled together by a belt, such that rotation of the first generator gear causes rotation of the second generator gear.

Advantageously, this arrangement is lightweight, and the two generator gears are able to be separate by a distance.

In this way, the apparatus 1 can function like a pendulum to generate energy, where the ballast 7 swings back and forth in the first direction 8 and the second direction 9 in a reciprocating motion. 35 This reciprocating, pendulum-like motion then drives the first and second drive paths and thus powers the first generator 15 and the second generator 16.

In one variation, the ballast 7 comprises a propulsion system 24 configured to propel the apparatus through the water and/or direct the apparatus 1 to point the first end 28 of the buoyant body into the 40 oncoming water waves 2 (as illustrated in Figures 3B to 3D). The propulsion system 24 comprises at least one duct 25 comprising a first end 26 and a second end 27, the first end 26 of the at least one duct 25 acts as an inlet and is configured so as to draw water into the at least one duct 25 and the second end 27 of the at least one duct 25 acts as an outlet and is configured so as to expel water out of the at least one duct 25. In examples where the at least one duct 25 comprises two ducts 25, the two ducts 25 may be arranged on opposing sides of the base element 20, such that they extend through the base element 20 parallel to each other. The configuration of the first 26 and second 27 ends of the two ducts 25 provides a differential steering effect to the ballast 7 which can propel the apparatus 1 through the water and/or direct the apparatus 1 to point the first end 28 of the buoyant body into the oncoming water waves 2 by applying more drive torque to one side of the apparatus 1 than the other.

It is alternatively envisaged that the second body section 5 may be arranged inside the first body section 4 such that the second body section 5 is an inner body section of the buoyant body 3 and the first body section 4 is an outer body section of the buoyant body 3. In such arrangements, the arrangement and configuration of the aforementioned features including (but not limited to) features related to the ballast 7, and the energy generation system 10 are substantially similar, other than the differences noted in the paragraph below.

In this example, as the ballast 7 is attached to the first body section 4 (the first body section 4 being arranged around the second body section 5), there is no need for an aperture 32 for the ballast to protrude through, as the ballast 7 is arranged on the outer body section. Furthermore, the energy generation system 10 is arranged inside the second body section 5 and is thus also arranged inside the first body section 4. The energy generation system 10 is hermetically sealed inside the second C\J body section 5 inside a cylindrical chamber 18 which may similarly comprise structural ribs 30 for strength and support.

Now turning to Figures 3A to 3D, in some examples the ballast 7 is configured to be anchored to a surface below the surface of the water waves 2, such as a sea bed, a submerged pontoon or any other submerged structure or surface, at a location that is offshore. Advantageously, the ballast 7 being anchored allows the apparatus 1 to stay fixed in the same location and not float away.

Furthermore, the ballast 7 being anchored increases energy generation in the first 15 and second 16 generators, as well as improving the longevity of the apparatus 1 and making maintenance more straight-forward. At offshore locations water waves 2 may be constant, thus the water wave energy which can be harnessed by the apparatus 1 may be more consistent and/or of a higher magnitude.

The ballast 7 may be anchored to a surface below the water by at least one tether 37, for example one tether 37 (as shown in Figure 3B), two tethers 37 (as shown in Figures 3A; 3C and 3D), three tethers 37, four tethers 37, or any other suitable number of tethers 37. Each tether 37 is coupled to the base element 20 at a first end of each tether 37 and each tether 37 is configured to be coupled to the surface below the water waves 2 at a second end of each tether 37. Each tether may be a rigid element or may be a flexible element, such as a cable, a rope or a chain.

Figures 3A and 3B show the buoyant body 3 in an instantaneously level configuration where, for 5 example, the water wave 2 may be halfway through the wave cycle such that the amplitude of the water wave 2 is zero. Figure 3C shows an oncoming water wave 2 causing the first end 28 of the buoyant body 3 to rise up, thus rotating the buoyant body 3 in the first direction 8. Figure 3D shows the oncoming wave 2 as it has passed along the buoyant body 3 such that it has caused the second end of the buoyant body to rise up, thus rotating the buoyant body 3 in the second direction 9. 10 Figure 4A shows a schematic front, cross-sectional view of a watercraft 141 comprising a hull 144, a mast 142 and a keel 146. The watercraft 141 further comprises a bow 155 (the front of the watercraft 141) and a stern 156 (the back of the watercraft 141), as shown in Figure 5. The hull 144 comprises a longitudinal axis 145 (Figure 5) and the mast 142 comprises a central axis 143, where the central axis 143 of the mast 142 is generally perpendicular to the longitudinal axis 145 of the hull 141. The central axis 143 of the mast 142 is arranged with respect to the longitudinal axis 145 of the hull 144 at an angle of between approximately 60 degrees and 90 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably between approximately 85 degrees and 90 degrees.

The mast 142 and the keel 146 are rotationally fixed relative to each other by a coupling 147, such that rotation of the mast 142 relative to the hull 144 about the longitudinal axis 145 of the hull 144 causes the keel 146 to rotate relative to the hull 144 about the longitudinal axis 145 of the hull 144, C\J and vice versa. The mast 142 and the keel 146 are fixed to the coupling 147 at positions that are diametrically opposed to each other. Alternatively, the mast 142 and the keel 145 are fixed to the coupling 147 at any other suitable position about the coupling 147.

The keel 146 and the mast 142 are configured to rotate relative to the hull 144 about the longitudinal axis 145 of the hull 144 in both a first 108 and second 109 direction, where the first 108 and second 109 directions are opposite to each other. The first direction 108 is clockwise when viewed along the longitudinal axis 145 of the hull 144 from the bow 155 or the stern 156 of the watercraft 141 and the second direction 109 is anti-clockwise when viewed along the longitudinal axis 145 of the hull 144 from the same one of the bow 155 or the stern 156 of the watercraft 141. The mast 142 and the keel 146 can rotate relative to the hull 144 only about the longitudinal axis 145 of the hull, and not about any other axis, for example, in the mast 142 and the keel 146 cannot rotate in other directions such as about a pitch axis of the watercraft (towards the bow and the stern of the watercraft). This reduces the risk of mechanical failure of the mast, the keel, and/or the coupling as the mast and the keel cannot be suddenly inadvertently rotated in different directions by the water waves.

The coupling 147 and the hull 144 are concentric with respect to each other, so that the coupling 147 is arranged inside the hull 144. The hull comprises an aperture 157 through which the mast 142, the coupling 147, and the keel 146 extend. The aperture 157 allows the mast 142, the coupling 147, and the keel 146 to rotate relative to the hull 144.

The coupling 147 has a generally cylindrical portion and comprises an internal volume 165, such that the coupling 147 is tube-like. The generally cylindrical portion of the coupling 147 comprises a first section 168 and a second section 169 that are spaced apart from each other about the central axis 143 of the mast 142 and are diametrically opposed from each other, such that they can be thought of as two halves of the coupling 147, as illustrated in Figure 4C.

The mast 142 has a weight, and the weight of the mast 142 may be thought of as inherently acting along an imaginary line 148 along the length of the mast. When the mast 142 is arranged vertically (such that it is perpendicular to the longitudinal axis 145 of the hull 144), the line of action 148 of the weight of the mast 142 would ordinarily inherently be coincident with the central axis 143 of the mast 142. However, the coupling 147 is configured so that at least a portion of the line of action 148 of the weight of the mast 142 is diverted away from and offset from the mast 142 and is instead configured to act through the coupling 147. For example, when the mast 142 is vertical, the line of action 148 of the weight of the mast, at the point where the coupling 147 and the mast 142 meet, splits in two such that some of the weight of the mast 142 acts through, or is diverted through, the first section 168 of the coupling 147 and some of the weight of the mast 142 acts through, or is diverted through, the second section 169 of the coupling 147. As the first section 168 and the second section 169 are spaced apart about the central axis 143 of the mast 142, the line of action 148 of the weight of the C\J mast 142 is thus offset from the central axis 143 of the mast 142 when it is acting through the first section 168 and the second section 169 of the coupling 147. The line of action 148 of the weight of the mast 142 being arranged through the coupling 147 advantageously provides that the mast 142 can thus be less prone to mechanical failure, such as deformation and buckling.

Turning now to Figures 4B and 4C, the keel 146 comprises two elongate elements 119 and a base element 120, the elongate elements 119 each comprising a first end 121, a second end 122, and a length 123, each first end 121 being spaced apart from each second end 122 along the length 123 of the elongate element 119. The elongate elements 119 protrude from, or extend from, the coupling 147. Each first end 121 is coupled to the coupling 147 and each second end 122 is coupled to the base element 120. Each elongate element 119 is coupled to the coupling 147 such that they are spaced apart along the longitudinal axis 145 of the hull 144 and aligned in the same plane, such that when viewed from the bow 155 or the stern 156, only one of the elongate elements 119 is visible (as shown in Figure 4A and 4C). The base element 120 of the keel 146 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 120 may be generally cuboidal, hexagonal or any other suitable shape. During use of the watercraft 141, the entirety of the keel 146 is submerged below the surface of the water waves 2.

Alternatively, the keel 146 may comprise one elongate element 119 and a base element 120, the elongate element 119 comprising a first end 121, a second end 122, and a length 123, the first end 121 being spaced apart from the second end 122 along the length 23 of the elongate element 119 (as illustrated in Figure 5). The elongate element 119 protrudes from, or extends from, the coupling 147. The first end 121 is coupled to the coupling 147 and the second end 122 is coupled to the base element 120. The elongate element 119 is coupled to the coupling 147 at the midpoint of the length of the coupling 147 and at the midpoint of the width of the coupling 147. It is also envisaged that the elongate element 119 may be not coupled to the coupling 147 at a midpoint of the length or width of the coupling 147, and may be coupled to the coupling 147 at any other suitable location. The base element 120 of the keel 146 may comprise a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 120 may be generally cuboidal, hexagonal or any other suitable shape.

Alternatively still, the keel 146 is a twin keel (or a bilge keel) and as such comprises a first keel element and a second keel element, where the first and second keel elements are circumferentially spaced apart from each other about the perimeter of the coupling (as illustrated in Figure 6A for example). Twin keels, or bilge keels, allow the watercraft 141 to have a shallower draft (that is, the vertical distance between the waterline and the bottom of the hull 144) while still allowing for minimum leeway while sailing. The placement of the twin keel or bilge keel also allows the watercraft 141 to stand upright when out of the water without additional support, since they can act as stabilisers, as opposed to a watercraft 141 with a single keel that could fall over if water levels dropped. The first and second keel elements each comprise a longitudinal axis, where the longitudinal axis of the first C\J keel element is normal to the perimeter of the coupling and the longitudinal axis of the second keel element is also normal to the perimeter of the coupling. The first keel element and the second keel element each comprise an elongate element 119, each elongate element 119 comprising a first end 121, a second end 122, and a length 123, the first end 121 being spaced apart from the second end 122 along the length 123 of the elongate element 119. The elongate element 119 protrudes from, or extends from, the coupling 147. The first end 121 is coupled to the coupling 147 and the second end 122 is coupled to the base element 120. The base element 120 of the keel 146 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 120 may be generally cuboidal, hexagonal or any other suitable shape.

The keel 146 comprises a propulsion system 124 configured to propel the watercraft 141 through the water and/or direct the watercraft 141 to point the bow 155 in the desired direction (further illustrated in Figure 5). The propulsion system 124 comprises at least one duct 125 comprising a first end 126 and a second end 127, the first end 126 of the at least one duct 125 acts as an inlet and is configured so as to draw water into the at least one duct 125, and the second end 127 of the at least one duct 125 acts as an outlet and is configured so as to expel water out of the at least one duct 125. In examples where the at least one duct 125 comprises two ducts 125, the two ducts 125 may be arranged on opposing sides of the base element 120, such that they extend through the base element 120 parallel to each other. The configuration of the first 126 and second 127 ends of the two ducts 125 advantageously provides a differential steering effect to the keel 146 which can propel the watercraft 141 through the water and/or direct the watercraft 141 to direct the bow 155 to the desired direction by applying more drive torque to one side of the watercraft 141 than the other. In other examples, the keel 146 may not comprise the propulsion system 124.

The watercraft 141 further comprises an energy generation system 110, configured to provide energy to the watercraft 141. The energy generation system 110 is hermetically sealed inside a cylindrical chamber 118 so as to protect the energy generation system 110 from water ingress and other potential damage from the water waves 2 and foreign object debris. In the example illustrated, the cylindrical chamber 118 comprises structural ribs 130 configured to provide strength and support to the cylindrical chamber 118. The cylindrical chamber 118 is concentric with the coupling 147, such that it is arranged inside the coupling 147.

The energy generation system 110 comprises a first gear 111 and a second gear 112, a first flywheel 113 and a second flywheel 114, and a first generator 115 and a second generator 116. The first generator 115 and the second generator 116 are each configured to generate electrical energy. The first gear 111 and the second gear 112, and the first flywheel 113 and the second flywheel 114 rotate about an energy generation system rotational axis 117. The first gear 111 and the second gear 112 are ratchet gears, hence the first gear 111 is configured to rotate about the energy generation system rotational axis 117 in the first direction 108 only and the second gear 112 is configured to rotate about the energy generation system rotational axis 117 in the second direction 109 only. Correspondingly, C\J the first flywheel 113 is configured to rotate about the energy generation system rotational axis 117 in the first direction 108 only and the second flywheel 114 is configured to rotate about the energy generation system rotational axis 117 in the second direction 109 only.

The first generator 115 comprises a first generator central axis 133 and the second generator 116 comprises a second generator central axis 134. In the example illustrated, the axes 133 and 134 are parallel to and offset from the energy generation system rotational axis 117 and from one another. It is also envisaged that the first generator central axis 133 and the second generator central axis 134 may be arranged to be coincident with each other, parallel to, and offset from the energy generation system rotational axis 117. Alternatively, the first generator central axis 133, the second generator central axis 134 and the energy generation system rotational axis 117 may be all coincident with each other.

The first gear 111 is coupled to the first flywheel 113, and the first flywheel 113 is coupled to the first generator 115, so as to define a first drive path from the first gear 111 to the first generator 115. The second gear 112 is coupled to the second flywheel 114, and the second flywheel 114 is coupled to 40 the second generator 116, so as to define a second drive path from the second gear 112 to the second generator 116. The keel 146 and the mast 142 are coupled to the first gear 111 so as to form a part of the first drive path, such that relative rotation between keel 146 and the mast 142, and the hull 145 in the first direction 108 drives the first generator 115. The keel 146 and the mast 142 are also coupled to the second gear 112 so as to form a part of the second drive path, such that relative rotation between the keel 146 and the mast 142, and the hull 144 in the second direction 109 drives the second generator 16. The first flywheel 113 and the second flywheel 114 are configured to store rotational energy such that when the mast 142 and the keel 146 rotate in the second direction 109, the first flywheel 113 continues to rotate in the first direction 108 thus continuing to power the first generator 115 even when the first gear 111 is not being rotated and when the mast 142 and the keel 146 rotates in the first direction 108, the second flywheel 114 continues to rotate in the second direction 109 thus continuing to power the second generator 116 even when the second gear 112 is not being rotated.

The coupling 147 is coupled to the hull 144 by a first shaft 135 and a second shaft 136, the first shaft 135 and the second shaft 136 each comprise a longitudinal axis about which they rotate. The longitudinal axis of the first 135 and second 136 shaft are coincident with the energy generation system rotational axis 117 and the longitudinal axis 145 of the hull 144. The first shaft 135 is coupled to the first gear 111 such that rotation of the first shaft 135 about the longitudinal axis 145 of the hull 144 in the first direction 108 rotates the first gear 111 in the first direction 108 and as such drives the first generator 113, and the second shaft 136 is coupled to the second gear 112 such that rotation of the second shaft 136 about the longitudinal axis 145 of the hull 144 in the second direction 109 rotates the second gear 112 in the second direction 109 and as such drives the second generator 116. The first shaft 135 and the second shaft 136 each comprise a series of bearings 131 configured C\J to assist the rotation of the first shaft 135 in the first direction 108 and configured to assist the rotation of the second shaft 136 in the second direction 109.

The first flywheel 113 is coupled to the first generator 115 by a first generator coupling 139. In some examples, the first generator coupling 139 may comprise a series of generator gears configured so as to increase the gear ratio such that the generator gear that is coupled to the first generator 115 is configured to spin faster than the generator gear that is coupled to the first flywheel 113.

Advantageously, this increases the energy generated by the first generator 115. Alternatively, the first generator coupling 139 may comprise a first generator gear that is coupled to the first flywheel 113 and a second generator gear that is coupled to the first generator 115, the first generator gear and the second generator gear being coupled together by a belt, such that rotation of the first generator gear causes rotation of the second generator gear. Advantageously, this arrangement is lightweight, and the two generator gears are able to be separate by a distance.

Similarly, the second flywheel 114 is coupled to the second generator 116 by a second generator coupling 140. In some embodiments, the second generator coupling 140 may comprise a series of 40 generator gears configured so as to increase the gear ratio such that the generator gear that is coupled to the second generator 116 is configured to spin faster than the generator gear that is coupled to the second flywheel 114. Advantageously, this increases the energy generated by the second generator 116. Alternatively, the second generator coupling 140 may comprise a first generator gear that is coupled to the second flywheel 114 and a second generator gear that is coupled to the second generator 116, the first generator gear and the second generator gear being coupled together by a belt, such that rotation of the first generator gear causes rotation of the second generator gear. Advantageously, this arrangement is lightweight, and the two generator gears are able to be separate by a distance.

In this way, the mast 142, the keel 146 and the coupling 147 can function like a pendulum to generate energy, where the mast 142 and the keel 146 swings back and forth in the first direction 108 and the second direction 109 in a reciprocating motion. This reciprocating, pendulum-like motion then drives the first and second drive paths and thus powers the first generator 115 and the second generator 116.

Turning to Figure 5, as the watercraft 141 sails along the water waves 2, the mast 142 is tilted about the longitudinal axis 145 of the hull 144, by, for example, air (wind) moving over the mast 142, which in turn rotates the keel 146 about the longitudinal axis 145 of the hull 144. As the mast 142 and the keel 146 are configured to rotate relative to the longitudinal axis 145 of the hull 144, the hull 144 remains level when the mast 142 and the keel 146 rotate, as shown in Figure 5, which provides improved comfort levels for passengers aboard the watercraft 141.

As the bow 155 of the watercraft 141 begins to be lifted by the crest of a water wave 2, the moment C\J produced by the keel 146 about the longitudinal axis 145 of the hull 144 is much greater than the counter moment produced by the mast 142 about the longitudinal axis 145 of the hull 144 such that the mast 142 rightens itself (that is, it moves the mast 142 back towards a vertical position) about the longitudinal axis 145 of the hull 144. The opposite occurs when the bow 155 of the watercraft 141 begins to drop as the crest of the water waves moves along the longitudinal axis 145 of the hull 144, the hull 144 descends a water wave 2 and the keel 142, due to the inertia and fluid drag from the water, rotates towards the surface of the water about the longitudinal axis 145 of the hull 144. This rotational back and forth movement of the mast 144 and the keel 146 is what drives the first and second drive paths, thus powering the first 15 and second 16 generators.

Figure 6A shows a schematic front, cross-sectional view of a watercraft 241 comprising a hull 244, a mast 242 and a keel 246. The watercraft 241 further comprises a bow 255 (the front of the watercraft 241) and a stern 256 (the back of the watercraft 241), as shown in Figure 6B. The hull 244 comprises a longitudinal axis 245 (Figure 6B) and the mast 242 comprises a central axis 243, where the central axis 243 of the mast 242 is generally perpendicular to the longitudinal axis 245 of the hull 241. The central axis 243 of the mast 242 is arranged with respect to the longitudinal axis 245 of the hull 244 at an angle of between approximately 60 degrees and 90 degrees, more preferably between approximately 75 degrees and 90 degrees, more preferably between approximately 85 degrees and 90 degrees.

The mast 242 and the keel 246 are rotationally fixed relatively to each other by a coupling 247, such that rotation of the mast 242 relative to the hull 244 about the longitudinal axis 245 of the hull 244 causes the keel 246 to rotate relative to the hull 244 about the longitudinal axis 245 of the hull 244, and vice versa.

The keel 246 and the mast 242 are configured to rotate relative to the hull 244 about the longitudinal axis 245 of the hull 244 in both a first 208 and second 209 direction, where the first 208 and second 209 directions are opposite to each other. The first direction 208 is clockwise when viewed along the longitudinal axis 245 of the hull 244 from the bow 255 or the stern 256 of the watercraft 241 and the second direction 209 is anti-clockwise when viewed along the longitudinal axis 245 of the hull 244 from the same one of the bow 255 or the stern 256 of the watercraft 241. The mast 242 and the keel 246 can rotate relative to the hull 244 only about the longitudinal axis 245 of the hull, and not about any other axis, for example, mast 242 and the keel 246 cannot rotate in other directions such as about a pitch axis of the watercraft 241 (towards the bow 255 and the stern 256 of the watercraft 241). This reduces the risk of mechanical failure of the mast 242, the keel 246, and/or the coupling 247 as the mast 242 and the keel 246 cannot be suddenly inadvertently rotated in different directions 20 by the water waves 2.

The coupling 247 has a generally cylindrical portion and comprises an internal volume, such that the coupling 247 is tube-like. The generally cylindrical portion of the coupling 247 comprises a first CV section 268 and a second section 269 that are spaced apart from each other about the central axis 243 of the mast 242 and are diametrically opposed from each other, such that they can be thought of as two halves of the coupling 247.

The coupling 247 and the hull 244 are concentric with respect to each other, so that the hull 144 is arranged to pass through the internal volume of the coupling 247 and the coupling 247 surrounds the hull 144. The coupling 247 surrounds the hull 244 at a point approximately halfway along the length of the hull 244 (Figure 6B), although it is also envisaged that the coupling 247 may surround the hull 244 at any other suitable location along the length of the hull 244.

The mast 242 has a weight, and the weight of the mast 242 may be thought of as inherently acting 35 along an imaginary line 248 along the length of the mast 242. When the mast 242 is arranged vertically (such that it is perpendicular to the longitudinal axis 245 of the hull 244), the line of action 248 of the weight of the mast 242 would ordinarily be coincident with the central axis 243 of the mast 242. However, the coupling 247 is configured so that at least a portion of the line of action 248 of the weight of the mast 242 is diverted away from and offset from the mast 242 and is instead configured 40 to act through the coupling 247. For example, when the mast 242 is vertical, the line of action 248 of the weight of the mast, at the point where the coupling 247 and the mast 242 meet, splits in two such that some of the weight of the mast 242 acts through, or is diverted through, the first section 268 of the coupling 247 and some of the weight of the mast 242 acts through, or is diverted through, the second section 269 of the coupling 247. As the first section 268 and the second section 269 are spaced apart about the central axis 243 of the mast 242, the line of action 248 of the weight of the mast 242 is thus offset from the central axis 243 of the mast 242 when it is acting through the first section 268 and the second section 269 of the coupling 247. The line of action 248 of the weight of the mast 242 being arranged through the coupling 247 provides that the mast 242 can thus be less prone to mechanical failure, such as deformation and buckling.

The keel 246 is a twin keel 254 (or a bilge keel) and as such comprises a first keel element 249 and a second keel element 250, where the first 249 and second 250 keel elements are circumferentially spaced apart from each other about the perimeter 253 of the coupling 247. The first 249 and second 250 keel elements each comprise a longitudinal axis 251, 252, where the longitudinal axis 251 of the first keel element 249 is normal to the perimeter 253 of the coupling 247 and the longitudinal axis 252 of the second keel element 250 is also normal to the perimeter 253 of the coupling 247. The first keel element 249 and the second keel element 250 each comprise an elongate element 219, each elongate element 219 comprising a first end 221, a second end 222, and a length 223, the first end 221 being spaced apart from the second end 222 along the length 223 of the elongate element 219.

The elongate element 219 protrudes from, or extends from, the coupling 247. The first end 221 is coupled to the coupling 247 and the second end 222 is coupled to the base element 220. The base element 220 of the keel 246 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 220 may be generally cuboidal, CV hexagonal or any other suitable shape.

Alternatively, the keel 246 comprises two elongate elements 219 and a base element 220, the elongate elements 219 each comprising a first end 221, a second end 222, and a length 223, where each first end 221 is spaced apart from each second end 222 along the length 223 of the elongate element 219. The elongate elements 219 protrude from, or extend from, the coupling 247. Each first end 221 is coupled to the coupling 247 and each second end 222 is coupled to a base element 220. Each elongate element 219 is coupled to the coupling 247 such that they are spaced apart along the longitudinal axis 245 of the hull 244 and aligned in the same plane, such that when viewed from the bow 255 of the watercraft 241 or the stern 256 of the hull 244, only one of the elongate elements 219 is visible (see for example Figure 4B and 4C). The base element 220 of the keel 246 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 220 may be generally cuboidal, hexagonal or any other suitable shape.

Alternatively, the keel 246 may comprise one elongate element 219 (as in Figure 5) and a base element 220, the elongate element 219 comprises a first end 221, a second end 222, and a length 40 223, the first end 221 being spaced apart from the second end 222 along the length 223 of the elongate element 219. The elongate element 219 protrudes from, or extends from, the coupling 247. The first end 221 is coupled to the coupling 247 and the second end 222 is coupled to a base element 220. The elongate element 219 is coupled to the coupling 247 at the midpoint of the length of the coupling 247 and at the midpoint of the width of the coupling 247. It is also envisaged that the elongate element 219 may be not coupled to the coupling 247 at a midpoint of the length or width of the coupling 247, and may be coupled to the coupling 247 at any other suitable location. The base element 220 of the keel 246 comprises a generally circular portion, such as a generally spherical, ellipsoidal, or disk-like portion. Alternatively, the base element 220 may be generally cuboidal, hexagonal or any other suitable shape.

The keel 246 comprises a propulsion system 224 configured to propel the watercraft 241 through the water and/or direct the watercraft 241 to point the bow 255 in the desired direction. The propulsion system 224 comprises at least one duct 225 comprising a first end 226 and a second end 227, the first end 226 of the at least one duct 225 acts as an inlet and is configured so as to draw water into the at least one duct 225 and the second end 227 of the at least one duct 225 acts as an outlet and is configured so as to expel water out of the at least one duct 225. In examples where the at least one duct 225 comprises two ducts 225, the two ducts 225 may be arranged on opposing sides of the base element 220, such that they extend through the base element 220 parallel to each other. The configuration of the first 226 and second 227 ends of the two ducts 225 provides a differential steering effect to the keel 246 which can propel the watercraft 241 through the water and/or direct the watercraft 241 to direct the bow 255 to the desired direction by applying more drive torque to one side of the watercraft 241 than the other.

CV Turning to Figures 7A and 7B, the watercraft 241 comprises an energy generation system 210, configured to provide energy to the watercraft 241. The energy generation system 210 is hermetically sealed inside the hull 244 so as to protect the energy generation system 110 from water ingress and other potential damage from the water waves 2 and foreign object debris.

The energy generation system 210 comprises a first gear 211 and a second gear 212, a first flywheel 213 and a second flywheel 214, and a first generator 215 and a second generator 216. The first generator 215 and the second generator 216 are each configured to generate electrical energy. The first gear 211 and the second gear 212 are ratchet gears, hence the first gear 211 is configured to rotate in the first direction 208 only and the second gear 212 is configured to rotate in the second direction 209 only. Correspondingly, the first flywheel 213 is configured to rotate in the first direction 208 only and the second flywheel 214 is configured to rotate in the second direction 209 only.

The first gear 211 comprises a first gear rotational axis 286 about which it rotates in the first direction 208 and the second gear 212 comprises a second gear rotational axis 287 about which it rotates in the second direction 209. The first flywheel 213 comprises a first flywheel rotational axis 288 about 40 which it rotates in the first direction 208 and the second flywheel 214 comprises a second flywheel rotational axis 289 about which it rotates in the second direction 209. The first generator 215 comprises a first generator central axis 233 and the second generator 216 comprises a second generator central axis 234. The first gear rotational axis 286 and the second gear rotational axis 287 are coincident with each other, and parallel to and offset from the rotational axes 288, 289 of the first 5 213 and second 214 flywheels and parallel to and offset from the rotational axes 233, 234 of the first 215 and second 216 generators. The first flywheel rotational axis 288 and the second flywheel rotational axis 289 lie in the same plane and are spaced apart from each other. The first generator central axis 233 and the second generator central axis 234 lie in the same plane and are offset from each other. Alternatively, the rotational axes 286, 287, 288, 289 of the first 211 and second 212 gears 10 and the first 213 and second 214 flywheels are coincident such that they all rotate about the same axis, an energy generation system rotational axis.

The first gear 211 is coupled to the first flywheel 213, and the first flywheel 213 is coupled to the first generator 215, so as to define a first drive path from the first gear 211 to the first generator 215. The second gear 212 is coupled to the second flywheel 214, and the second flywheel 214 is coupled to the second generator 216, so as to define a second drive path from the second gear 212 to the second generator 216. The keel 246 and the mast 242 are coupled to the first gear 211 so as to form a part of the first drive path, such that relative rotation between keel 246 and the mast 242, and the hull 245 in the first direction 208 drives the first generator 215. The keel 246 and the mast 242 are also coupled to the second gear 212 so as to form a part of the second drive path, such that relative rotation between the keel 246 and the mast 242, and the hull 244 in the second direction 209 drives the second generator 216.

c\I The coupling 247 is coupled to the first gear 211 such that rotation of the coupling 247 about the longitudinal axis 245 of the hull 244 in the first direction 208 rotates the first gear 211 in the first direction 208 and as such drives the first generator 213, and the coupling 247 is coupled to the second gear 212 such that rotation of the coupling 247 about the longitudinal axis 245 of the hull 244 in the second direction 209 rotates the second gear 212 in the second direction 209 and as such drives the second generator 216. The coupling 247 is coupled to the first gear 211 and the second gear 212 by an energy generation apparatus coupling 285, the energy generation apparatus coupling 285 may comprise any suitable means for coupling the coupling 247 and the first 211 and second 212 gear, such as a rack and gear apparatus, or a belt and gear apparatus.

The first flywheel 213 is coupled to the first generator 215 by a first generator coupling. In some examples, the first generator coupling may comprise a series of generator gears configured so as to increase the gear ratio such that the generator gear that is coupled to the first generator 215 is configured to spin faster than the generator gear that is coupled to the first flywheel 213. Advantageously this increases the energy generated by the first generator 215. Alternatively, the first generator coupling may comprise a first generator gear that is coupled to the first flywheel 213 and a second generator gear that is coupled to the first generator 215, the first generator gear and the second generator gear being coupled together by a belt, such that rotation of the first generator gear causes rotation of the second generator gear. Advantageously, this arrangement is lightweight, and the two generator gears are able to be separate by a distance.

Similarly, the second flywheel 214 is coupled to the second generator 216 by a second generator coupling. In some embodiments, the second generator coupling may comprise a series of generator gears configured so as to increase the gear ratio such that the generator gear that is coupled to the second generator 216 is configured to spin faster than the generator gear that is coupled to the second flywheel 214. Advantageously, this increases the energy generated by the second generator 216. Alternatively, the second generator coupling may comprise a first generator gear that is coupled to the second flywheel 214 and a second generator gear that is coupled to the second generator 216, the first generator gear and the second generator gear being coupled together by a belt, such that rotation of the first generator gear causes rotation of the second generator gear. Advantageously, this arrangement is lightweight, and the two generator gears are able to be separate by a distance.

It is also envisaged that the energy generation system 110 as described in Figures 4B and 4C is suitable for use in this watercraft 241. Alternatively, it is envisaged that the energy generation system 210 as described in Figure 7A and 7B is suitable for use in the watercraft described in Figures 4A to 20 4C.

In this way, the mast 242 (not pictured in these figures), the keel 246 and the coupling 247 can function like a pendulum to generate energy, where the mast 242 and the keel 246 swings back and C\J forth in the first direction 208 and the second direction 209 in a reciprocating motion. This reciprocating, pendulum-like motion then drives the first and second drive paths and thus powers the first generator 215 and the second generator 216. Figure 7C to if show the keel 246 of the watercraft 241 at four different points in a wave cycle, the hull 244 of the watercraft 241 (and thus the energy generation system 210) remain in the same orientation and the keel 246 (and the mast 242) rotate in the first 208 and second 209 direction about the longitudinal axis 245 of the hull 244.

As the watercraft 241 sails along the water waves 2, the mast 242 is tilted about the longitudinal axis 245 (Figure 6B) of the hull 244, by, for example, air (wind) moving over the mast 242, which in turn rotates the keel 246 about the longitudinal axis 245 of the hull 244. As the mast 242 and the keel 246 are configured to rotate relative to the longitudinal axis 245 of the hull 244, the hull 244 remains level when the mast 242 and the keel 246 rotate, which provides improved comfort levels for passengers aboard the watercraft 241.

As the bow 255 (Figure 6B) of the watercraft 241 begins to be lifted by the crest of a water wave 2, the moment produced by the keel 246 about the longitudinal axis 245 of the hull 244 is much greater 40 than the counter moment produced by the mast 242 about the longitudinal axis 245 of the hull 244 such that the mast 242 rightens itself (that is, it moves the mast 242 back towards the vertical) about the longitudinal axis 245 of the hull 244. The opposite occurs when the bow 255 of the watercraft 241 begins to drop as the crest of the water waves moves along the longitudinal axis 245 of the hull 244, the hull 244 descends a water wave 2 but the keel 246, due to the inertia and fluid drag from the water, rotates towards the surface of the water about the longitudinal axis 245 of the hull 244. This rotational back and forth movement of the mast 244 and the keel 246 is what drives the first and second drive paths, thus powering the first 215 and second 216 generators.

Figures 8A to 8D show a schematic side view of a watercraft 341 comprising a sail 358, a hull 344 and a keel 346. The sail 358 comprises a plurality of blades 359 and a plurality of supports 360 (in the example illustrated there are three supports 360, but other examples are envisaged with any other number of supports, such as one, two, four, five or more supports 360), where each support 360 supports the plurality of blades 359 with respect to each other. The plurality of blades 359 each have a first end 390 and a second end 391 and each support 360 supports each of the plurality of blade 359 at the first end 390 and/or the second end 391. Each blade 359 has a longitudinal axis 365 and each blade 359 is arranged on the watercraft 341 so as to provide a propulsive force to the watercraft 341. That is, each blade 359 is arranged with respect to the hull 344 of the watercraft 341 such that the longitudinal axis 365 of each blade 359 is generally perpendicular to the longitudinal axis 345 of the hull 344. Each support 360 has a longitudinal axis 366 and the longitudinal axis 365 of each blade 359 is generally perpendicular to the longitudinal axis 366 of each support 360.

In the example illustrated by Figures 8A to 8D, the sail 358 comprises a mast 342, the mast 342 comprising a central axis 343. The support 360 is coupled to the mast 342 and arranged to protrude C\J therefrom so that a longitudinal axis 366 of the support 360 is generally perpendicular to the central axis 343 of the mast 342. The support 360 is coupled to the mast 342 at a point along the longitudinal axis 366 that is towards one end of the support 360. Alternatively, the support 360 may be coupled to the mast 342 at a midpoint along the longitudinal axis 366 of the support 360, such that the support 360 is coupled to the mast 342 at the centre of the support 360. The support 460 may be configured to rotate about the central axis 343 of the mast 442 (as shown in Figures 9B and 9C). It is also envisaged that the sail 358 may not comprise a mast 342, and the support 360 may instead be coupled to the coupling or the hull 344 of the watercraft 341 instead at any point along the longitudinal axis 366 of the support 360.

Each blade 359 has an aerofoil cross-sectional profile, the aerofoil cross-sectional profile comprising a leading edge and a trailing edge where the leading edge is the edge that faces into the oncoming wind (towards the bow 355) and the trailing edge is the edge at the opposing end of the aerofoil cross-sectional profile to the leading edge (towards the stern 356). Each aerofoil cross-sectional profile has an angle of attack, the angle of attack being the angle between an imaginary line joining the leading edge and the trailing edge (the chord line) and the relative oncoming airflow. The angle of attack of the aerofoil cross-sectional profile determines the direction of the propulsive force created on the blade by the oncoming air.

The plurality of blades 359 form a set of blades 359, with each sail 358 comprising one or more sets of blades 359. In the example illustrated in Figures 8A to 8D, the sail 358 comprises two sets of blades 359, where each set of blades 359 is arranged on top of each other such that they are stacked vertically on top of each other, and separated by a support 360.

The support 360 further comprises a guide means where the guide means guides the plurality of blades 359 so that the blades 359 are moveable with respect to each other. The guide means is configured such that the blades 359 are moveable along the guide means so that they move along the longitudinal axis 466 of the support 460. In the position shown in Figure 8A, both the top set of blades 359 and the bottom set of blades 359 are fully extended along the whole length of each support 360. In the position shown in Figure 8B, the top set of blades are fully retracted towards the mast 342 and the bottom set of blades 359 are fully extended along the whole length of each support 360. In the position shown in Figure 8C, both the top set of blades 359 and the bottom set of blades 359 are halfway extended along the length of each support 360. In the position shown in Figure 8D, both the top set of blades 359 and the bottom set of blades 359 are fully retracted towards the mast 342. This movement of the blades 359 along the longitudinal axis 366 of the support 360 defines a translational degree of freedom of the blades 359. The first portion 374 is fixed relative to the support 360 such that the second portion 375 rotates relative to the first portion 374 and the support 360. The translational degree of freedom of the blades 359 advantageously allows the blades 359 to be moved into a formation that results in an increased total surface area of the blades 359, thus CV increasing the propulsive force to the watercraft. It is also envisaged that the blades 359 may further have a rotational degree of freedom, for example as described in relation to Figures 9A to 10E below.

In the examples illustrated in Figures 8A to 8D, the sail 358 has a forestay 385, the forestay 385 being arranged to couple the mast 342 to the hull 344. The sail having a forestay 385 prevents the mast from rotating in directions other than about the longitudinal axis 345 of the hull 344. It is also 30 envisaged that the sail 358 may not comprise a forestay 385.

The sail 358 may comprise an actuator means configured to actuate the blades 359 such that they move in the first rotational degree of freedom and the second translational degree of freedom. The actuator means may be a motor, for example, such as a high torque planet geared motor. The sail 358 may further comprise a control means configured to control the actuator means such that the blades 358 move in the first rotational degree of freedom and the second translational degree of freedom.

Furthermore, it is envisaged that one or more of the blades 359 of the sail 358 may at least partially 40 be covered with or may otherwise comprise one or more solar panel elements. For example, one or more of the blades 359 may be covered with flexible solar panels (not shown), such as 100 Watt 12 Volt flexible monocrystalline solar panels. In this way, the sail 358 may further be used to capture solar energy.

The sails as described in Figures 8A to 8D are suitable for use in and with all embodiments of the present disclosure, for example, as part of the watercraft described herein.

Figures 9A to 9D show an embodiment in which the sail, blades, mast, central axis of the mast, support, longitudinal axis of the support, and guide means are substantially similar to the sail, blades, mast, central axis of the mast, support, longitudinal axis of the support, and guide means of the embodiment of Figures 8A to 8D as described above, wherein reference numerals 458, 459, 442, 460, and 466 denote like elements to 358, 359, 342, 360, and 366 respectively.

Figures 9A to 9D show a schematic plan view of a sail 458 for a watercraft 441, the watercraft 441 comprising a hull 444. The hull comprises a longitudinal axis 445, a bow 455 and a stern 456. The sail 458 comprises a plurality of blades 459, in the example illustrated four blades 459, however any number of blades 459 is envisaged, for example, one, two, three, five, six, seven, eight, nine, ten, or any other suitable number of blades 459.

The blades 459 and the support 460 are together configured to be rotatable about the central axis 443 of the mast 442, as sequentially shown in Figures 9A to 9D, which show the support in different rotational positions. Advantageously, the support 460 being configured to rotate about the central axis 443 of the mast 442 allows the surface area of the at least one blades 459 that is hit by the CV oncoming air to be varied, and therefore the magnitude of the propulsive force to the watercraft 441 can be varied.

Each blade 459 has an aerofoil cross-sectional profile 461, the aerofoil cross-sectional profile 461 comprising a leading edge 478 and a trailing edge 479 where the leading edge 478 is the edge that faces into the oncoming wind (towards the bow 455) and the trailing edge 479 is the edge at the opposing end of the aerofoil cross-sectional profile 461 to the leading edge 478 (towards the stern 456). The aerofoil cross-sectional profile 461 is generally normal to the longitudinal axis of each blade 459. Each aerofoil cross-sectional profile 461 has an angle of attack, the angle of attack being the angle between an imaginary line joining the leading edge 478 and the trailing edge 479 (the chord line) and the relative oncoming airflow. The angle of attack of the aerofoil cross-sectional profile 461 determines the direction of the propulsive force created on the blade 459 by the oncoming air.

In the example shown, the plurality of blades 459 are arranged laterally with respect to each other, such that the chord line of each aerofoil cross-sectional profile 461 of each blade 459 is parallel to each of the other chord lines of the aerofoil cross-sectional profiles 461 and the longitudinal axis 466 40 of the support 460. The support 460 comprises a plurality of guide means 464, in the example illustrated two guide means 464, however any other number of guide means 464 is envisaged, for example, one, three, four (as illustrated in Figures 10A to 10C), five, six, seven, eight, nine, ten, or more guide means 464. Additionally, any number of blades 459 can be positioned on each guide means 464, for example, one blade 459 per guide means 464 (as illustrated in Figures 10A to 10C), or two blades 459 per guide means 564 (as illustrated in Figures 9A to 9D), or three blades 559 per guide means 564 etc.. As illustrated in Figures 9A to 10C, the guide means 464 comprise channels in the support 460 within which the blades 459 are configured to move along (or slide along), however other alternative guide means 464 are also envisaged. For example, the guide means may comprise a gear and rack system along which the blades 459 are configured to move. The plurality of guide means 464 guide the plurality of blades 459 so that the blades 459 are moveable with respect to each other. The plurality of guide means 464 are arranged on the longitudinal axis 466 of the support 460 (or alternatively, parallel to the longitudinal axis 466 of the support 460) and as such the blades 459 are moveable along the guide means 464 such that they become spaced apart along the longitudinal axis 466 of the support 460, as shown in Figure 9B and 9C (and in Figures 10B and 10C). This movement along (or parallel to) to the longitudinal axis 466 of the support 460 defines a translational degree of freedom of the blades 459. The translational degree of freedom of the blades 459 allows the blades 459 to be moved into a formation that results in an increased total surface area of the blades 459, thus increasing the propulsive force to the watercraft 441.

Each blade 459 has a first axis about which the blade 459 can rotate in its rotational degree of freedom. Each blade 459 is rotatable about the first axis 476 so that the chord line of the aerofoil cross-sectional profile of the blade 459 is arranged with respect to the longitudinal axis 466 of the support 460 at any angle between 0 degree and 90 degrees. For example, in Figure 9A, 9C and 9D CV the chord line of each aerofoil cross-sectional profile 461 of each blade 459 is arranged to be generally perpendicular to the longitudinal axis 466 of the support 460. In Figure 9B, the chord line of each aerofoil cross-sectional profile 461 of each blade 459 is arranged to be approximately 45 degrees to the longitudinal axis 466 of the support 460. The rotational degree of freedom allows the angle of attack of the aerofoil cross-sectional profile 461 to be varied so as to provide varying directions of propulsive force to the watercraft 441.

The sail 458 described in Figure 9A to 9D is suitable for use in any of the embodiments disclosed in Figure 1 to Figure 8D.

Figures 10A to 10E show another embodiment in which the sail, blades, mast, central axis of the mast, support, longitudinal axis of the support, aerofoil cross-sectional profile, leading edge, trailing edge, and guide means are substantially similar to sail, blades, mast, central axis of the mast, support, longitudinal axis of the support, aerofoil cross-sectional profile, leading edge, trailing edge, and guide means of the embodiment of Figures 8A to 8D and of the embodiment of Figures 9A to 9D, wherein reference numerals 558, 559, 542, 560, 566, 561, 578, 579, and 564 denote like elements to 458, 459, 442, 460, 466, 461, 478, 479, and 464 and like elements to 358, 359, 342, 360, and 366 respectively.

Figures 10A to 10C show a schematic plan view of a sail 558 for a watercraft 541. The sail 558 comprises a plurality of blades 559. Each blade 559 has a first portion 574 and a second portion 575, the first portion 574 comprising the leading edge 578 of the aerofoil cross-sectional profile 561 and the second portion 576 comprising the trailing edge 579 of the aerofoil cross-sectional profile 561, as further illustrated in Figures 10D and 10E. The first 574 and second 575 portions each have a rigid surface that defines their shape, the first rigid portion defining the leading edge 578 and the second rigid portion defining the trailing edge 579. The first portion 574 and the second portion 575 are rotationally coupled relative to each other by a first axis 576, such that the second portion 575 can rotate relative to the first portion 574 about the first axis 576, as sequentially shown in Figures 10D and 10E. As such, the second portion 575 may be thought of as being able to flex relative to the first portion 574. Rotation/flexing of the second portion 575 relative to the first portion 574 varies the angle of attack of the blade 558 and as such varies the direction of the propulsive force generated by the oncoming air hitting the blade 559. This rotation/flexing of the second portion 575 relative to the first portion 574 about the first axis 576 defines a rotational degree of freedom of the blades 559. The first portion 574 is fixed relative to the support 560 such that the second portion 575 rotates relative to the first portion 574 and the support 560.

The sail 458 described in Figures 10A to 10E is suitable for use in any of the embodiments disclosed in Figure 1 to Figure 9D.

CV Various modifications may be made to the described embodiment(s) without departing from the scope of the invention as defined by the accompanying claims.

Claims

CLAIMS1. An apparatus for generating energy from water waves, comprising: a buoyant body comprising a first body section and a second body section, wherein the buoyant body comprises a longitudinal axis; and a ballast, wherein the ballast and the first body section are configured to rotate relative to the second body section about said longitudinal axis both in a first direction and a second direction, the second direction being opposite to the first direction; wherein the ballast is rotationally fixed relative to the first body section such that rotation of the first body section relative to the second body section about said longitudinal axis causes the ballast to rotate relative to the second body section about said longitudinal axis, and such that rotation of the ballast relative to the second body section about said longitudinal axis causes the first body section to rotate relative to the second body section about said longitudinal axis; an energy generation system, comprising: a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in the first direction only and the second gear is configured to rotate in the second direction only; wherein the ballast is coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the ballast to the first generator, such that relative rotation between the ballast and the second body section in the first direction drives the first generator; and wherein the ballast is coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define a second drive path from the ballast to the second generator, such that relative rotation between the ballast and the second body section in the second direction drives the second generator.
2. The apparatus for generating energy from water waves as claimed in claim 1, wherein the first body section and the second body section are arranged to be concentric with respect to one another.
3. The apparatus for generating energy from water waves as claimed in claim 1 or 2, wherein the first body section is at least partially arranged inside the second body section.
4. The apparatus for generating energy from water waves as claimed in claim 1 or 2, wherein the second body section is at least partially arranged inside the first body section.
5. The apparatus for generating energy from water waves as claimed in any preceding claim, wherein at least a portion of the first body section is generally cylindrical and wherein at least a portion of the second body section is generally cylindrical.
6. The apparatus for generating energy from water waves as claimed in any preceding claim, wherein the energy generation system is arranged inside the first body section and/or the second body section.
7. The apparatus for generating energy from water waves as claimed in any preceding claim, wherein the first flywheel is configured to rotate in the first direction only and the second flywheel is configured to rotate in the second direction only.
8. The apparatus for generating energy from water waves as claimed in any preceding claim, the apparatus further comprising an energy generation system rotational axis, about which the first gear and the first flywheel are configured to rotate in the first direction, and about which the second gear and the second flywheel are configured to rotate in the second direction.
9. The apparatus for generating energy from water waves as claimed in claim 8, wherein the energy generation system rotational axis is coincident with the longitudinal axis of the buoyant body.
10. The apparatus for generating energy from water waves as claimed in any preceding claim, wherein the ballast comprises a propulsion system.
11. The apparatus for generating energy from water waves as claimed in any preceding claim, wherein the ballast is configured to be anchored.
12. The apparatus for generating energy from water waves as claimed in any preceding claim, wherein the first gear and the second gear are ratchet gears.
13. A watercraft comprising the apparatus for generating energy from water waves as claimed in any preceding claim.
14. The watercraft as claimed in claim 13, further comprising a mast comprising a central axis; 51 wherein: the first body section is a coupling; the second body section is a hull comprising a longitudinal axis; the ballast is a keel; the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by the coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.
15. The watercraft as claimed in claim 13, further comprising a mast comprising a central axis; wherein: the first body section is a coupling; the second body section is a hull comprising a longitudinal axis; the ballast is a keel; the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by the coupling such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and at least a portion of the hull is arranged inside an internal volume of the coupling.
16. The watercraft as claimed in claim 15, wherein the coupling is further configured to be coupled to the first gear and the second gear such that relative rotation between the coupling and the hull in the first direction drives the first generator and relative rotation between the coupling and the hull in the second direction drives the second generator.
17. The watercraft as claimed in any of claims 14 to 16, wherein the keel comprises a first keel element and a second keel element, wherein the first keel element and the second keel element are coupled to the coupling and are configured to protrude therefrom, the first keel element and the second keel element being spaced apart with respect to each other.
18. The watercraft as claimed in any of claims 14 to 17, further comprising a sail, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.
19. The watercraft as claimed in claim 18, wherein: each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally perpendicular to the longitudinal axis of the buoyant body; the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.
20. A watercraft comprising: a hull comprising a longitudinal axis; a mast comprising a central axis; and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.
21. The watercraft as claimed in claim 20, wherein the mast and the keel are configured to rotate relative to the hull only about the longitudinal axis of the hull.
22. The watercraft as claimed in claim 20 or 21, wherein the coupling comprises a generally cylindrical portion, such that at least a portion of the line of action of the weight of the mast is arranged through a first section and a second section of the generally cylindrical portion of the coupling, wherein the first section and the second section are diametrically opposed.
23. The watercraft as claimed in any of claims 20 to 22, wherein the coupling and the hull are arranged to be concentric with respect to one another.
24. The watercraft as claimed in any of claims 20 to 23, wherein at least a portion of the coupling is arranged inside the hull.
25. The watercraft as claimed in any of claims 20 to 23, wherein at least a portion of the hull is arranged inside an internal volume of the coupling.
26. The watercraft as claimed in any of claims 20 to 25, wherein the keel comprises a first keel element and a second keel element, wherein the first keel element and the second keel element are coupled to the coupling and are configured to protrude therefrom, the first keel element and the second keel element being spaced apart with respect to each other.
27. The watercraft as claimed in any of claims 20 to 26, wherein the keel comprises a propulsion system. 25
28. The watercraft as claimed in any of claims 20 to 27, further comprising an apparatus for generating energy from water waves; wherein the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull both in a first direction and a second direction, the second direction being opposite to the first direction; the apparatus for generating energy from water waves comprising an energy generation system, comprising: a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in the first direction only and the second gear is configured to rotate in the second direction only; wherein the mast and the keel are coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the mast and the keel to the first generator, such that relative rotation between the mast and the keel, and the hull in the first direction drives the first generator; and wherein the mast and the keel are coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define a second drive path from the mast and the keel to the second generator, such that relative rotation between the mast and the keel, and the hull in the second direction drives the second generator.
29. The watercraft as claimed in claim 28, wherein the coupling is configured to rotate relative to the hull about the longitudinal axis of the hull in both the first direction and the second direction, wherein the coupling is further configured to be coupled to the first gear and second gear such that relative rotation between the coupling and the hull in the first direction drives the first generator and relative rotation between the coupling and the hull in the second direction drives the second generator.
30. The watercraft as claimed in any of claims 20 to 29, further comprising a sail, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.
31. The watercraft of claim 30, wherein: each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally perpendicular to the longitudinal axis of the hull; wherein the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and wherein the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.
32. A watercraft comprising: a hull comprising a longitudinal axis; a mast; and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and at least a portion of the hull is arranged inside an internal volume of the coupling.
33. The watercraft as claimed in claim 32, wherein the mast and the keel are configured to rotate relative to the hull only about the longitudinal axis of the hull.
34. The watercraft as claimed in claim 32 or 33, wherein the coupling and the hull are arranged to be concentric with respect to one another.
35. The watercraft as claimed in any of claims 32 to 34, wherein at least a portion of the coupling is generally cylindrical, and at least a portion of the hull is generally cylindrical.
36. The watercraft as claimed in any of claims 32 to 35, wherein the keel comprises a first keel element and a second keel element, wherein the first keel element and the second keel element are coupled to the coupling and are configured to protrude therefrom, the first keel element and the second keel element being spaced apart with respect to each other.
37. The watercraft as claimed in any of claims 32 to 36, wherein the keel comprises a propulsion system.
38. The watercraft in any of claims 32 to 37, wherein the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.
39. The watercraft in any of claims 32 to 38, further comprising an apparatus for generating energy from water waves, wherein the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull both in a first direction and a second direction, the second direction being opposite to the first direction; the apparatus for generating energy from water waves comprising an energy generation system, comprising: a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in the first direction only and the second gear is configured to rotate in the second direction only; wherein the mast and the keel are coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the mast and the keel to the first generator, such that relative rotation between the mast and the keel, and the hull in the first direction drives the first generator; and wherein the mast and the keel are coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define a second drive path from the mast and the keel to the second generator, such that relative rotation between the mast and the keel, and the hull in the second direction drives the second generator.
40. The watercraft as claimed in claim 39, wherein the coupling is configured to rotate relative to the hull about the longitudinal axis of the hull in both the first direction and the second direction, wherein the coupling is further configured to be coupled to the first gear and second gear such that relative rotation between the coupling and the hull in the first direction drives the first generator and relative rotation between the coupling and the hull in the second direction drives the second generator.
41. The watercraft as claimed in any of claims 32 to 40, further comprising a sail, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.
42. The watercraft of claim 41, wherein: each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; the central axis of the mast is generally perpendicular to the longitudinal axis of the hull; wherein the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and wherein the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.
43. A sail for a watercraft, the sail comprising: at least one blade, and a support configured to support each of the at least one blades; wherein: each of the at least one blades comprises an aerofoil cross-sectional profile and is configured to provide a propulsive force; at least one of the at least one blades comprises a first rotational degree of freedom and a second translational degree of freedom; and the support comprises one or more guide means configured to guide the movement of said at least one of the at least one blades.
44. The sail for a watercraft as claimed in claim 43, wherein the at least one blade comprises a plurality of blades and wherein the one or more guide means are configured to support the plurality of blades such that at least one of the plurality of blades is movable with respect to at least another one of the plurality of blades in the first rotational degree of freedom and/or in the second translational degree of freedom.
45. The sail for a watercraft as claimed in claim 43 or 44, wherein the sail comprises a plurality of said supports, and the plurality of blades comprises a plurality of sets of blades, each support being configured to support one of the sets of blades.
46. The sail for a watercraft as claimed in any of claims 43 to 45, wherein at least one of the at least one blades comprises a first portion and a second portion, wherein the second portion is configured to be movable relative to the first portion.
47. The sail for a watercraft as claimed in claim 46, wherein said at least one of the at least one blades comprises a first axis, wherein the second portion is configured to rotate relative to the first portion about the first axis.
48. The sail for a watercraft as claimed in claim 46 or 47, wherein the first portion is rotationally fixed relative to the support, and wherein the second portion is configured to rotate relative to the first portion and relative to the support.
49. The sail for a watercraft as claimed in any of claims 46 to 48, wherein each of the at least one blades comprises an angle of attack which determines the direction of said propulsive force, wherein movement of said at least one blade in the first rotational degree of freedom is configured to vary the angle of attack.
50. The sail for a watercraft as claimed in claim 49, wherein the first portion of the blade comprises a leading edge of the aerofoil cross-sectional profile and the second portion of the blade comprises a trailing edge of the aerofoil cross-sectional profile, such that movement of the second portion relative to the first portion is configured to change the angle of attack of the blade.
51. The sail for a watercraft as claimed in any of claims 46 to 50, wherein the first portion comprises a first rigid surface that defines the leading edge, and the second portion comprises a second rigid surface that defines the trailing edge.
52. The sail for a watercraft as claimed in any of claims 43 to 51, wherein the sail further comprises an actuator means configured to actuate the movement of said at least one of the at least one blades in the first rotational degree of freedom and the second translational degree of freedom.
53. The sail for a watercraft as claimed in claim 52, wherein the sail further comprises a control means configured to control the actuator means.
54. The sail for a watercraft as claimed in any of claims 43 to 53, further comprising a mast, wherein the support is coupled to the mast and is arranged to extend therefrom in a generally perpendicular direction.
55. The sail for a watercraft as claimed in claim 54, wherein the mast comprises a central axis about which the support is configured to rotate. 25
56. The sail for a watercraft as claimed in claim 55, wherein: each of the at least one blades comprises a longitudinal axis generally normal to its aerofoil cross-sectional profile; the support comprises a longitudinal axis; wherein the central axis of the mast is generally parallel to the longitudinal axis of each of the at least one blades; and wherein the longitudinal axis of the support is generally perpendicular to the central axis of the mast and the longitudinal axis of each of the at least one blades.
57. A watercraft comprising: the sail as claimed in claim 54, and a hull comprising a longitudinal axis and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull.
58. A watercraft comprising: the sail as claimed in claim 54, and a hull comprising a longitudinal axis and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling, such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and the coupling is configured such that at least a portion of the line of action of the weight of the mast is arranged through the coupling and is offset from the central axis of the mast.
59. A watercraft comprising: the sail as claimed in claim 54, a hull comprising a longitudinal axis, and a keel; wherein: the mast and the keel are configured to rotate relative to the hull about the longitudinal axis of the hull; the mast is rotationally fixed relative to the keel by a coupling such that rotation of the mast relative to the hull about the longitudinal axis of the hull causes the keel to rotate relative to the hull about the longitudinal axis of the hull, and such that rotation of the keel relative to the hull about the longitudinal axis of the hull causes the mast to rotate relative to the hull about the longitudinal axis of the hull; and at least a portion of the hull is arranged inside an internal volume of the coupling.
60. An apparatus for generating energy from water waves comprising: the sail as claimed in any of claims 43 to 56; a buoyant body comprising a first body section and a second body section, wherein the buoyant body comprises a longitudinal axis; and a ballast, wherein the ballast and the first body section are configured to rotate relative to the second body section about said longitudinal axis both in a first direction and a second direction, the second direction being opposite to the first direction; wherein the sail protrudes from the buoyant body so as to provide a propulsive force to the buoyant body; wherein the ballast is rotationally fixed relative to the first body section such that rotation of the first body section relative to the second body section about said longitudinal axis causes the ballast to rotate relative to the second body section about said longitudinal axis, and such that rotation of the ballast relative to the second body section about said longitudinal axis causes the first body section to rotate relative to the second body section about said longitudinal axis; an energy generation system, comprising: a first gear and a second gear, a first flywheel and a second flywheel, and a first generator and a second generator; wherein the first gear is configured to rotate in a first direction only and the second gear is configured to rotate in a second direction only; wherein the ballast is coupled to the first gear, the first gear is coupled to the first flywheel, and the first flywheel is coupled to the first generator, so as to define a first drive path from the ballast to the first generator, such that relative rotation between the ballast and the second body section in the first direction drives the first generator; and wherein the ballast is coupled to the second gear, the second gear is coupled to the second flywheel, and the second flywheel is coupled to the second generator, so as to define a second drive path from the ballast to the second generator, such that relative rotation between the ballast and the second body section in the second direction drives the second generator.