WAVE ENERGY DEVICES Technical Field

This invention relates to a method and means for extracting energy in the form of thrust from waves and in particular to a method of and means for generating nett thrust in a preferred direction from the kinetic energy of moving water in waves for application to water craft to assist in the forward motion thereof or for driving a load such as electrical power generating means. Background Art

Many different devices for extracting energy from waves have been proposed in the past. Generally, such devices have been suggested in order to enable the generation of electrical power from-wave motion and in most cases include a floating body or bodies and complex mechanical or hydraulic power take off means to enable the oscillating movement or relative movement of the floating bodies to be converted into useful power. The known devices are generally massive, with a low output of power per unit of mass, complex and unable to generate power from a broad spectrum of wave periods, as they need to be "tuned" to a particular wave period and are quite inefficient in waves of other periods. The above described arrangements are of course limited to the generation of electrical power and are not applied to or applicable to providing thrust for water craft.

In a further arrangement, a 'foil propeller' which utilises the interaction of a deeply submerged adjusting aerofoil wing (controlled in its attitude by spring or hydraulic resistance) & either wave induced boat motion or engine produced vertical movement in the wing to generate thrust has been proposed. In this proposal, the wing is intended to be moved vertically either by the pitching of the boat, ship or other floating body to which it is attached, the floating body acting as a collector of wave energy in the form of movement perpendicular to the direction of travel. Alternatively, the wing is moved by power supplied by an engine or other power source.

The present invention aims to provide means for extracting energy in the form of thrust directly from the kinetic energy of the water close to the surface, moving due to wave action, for application in a first instance (linear) to water craft to assist or comprise the motive power for such craft and in a further aspect (rotary) to electrical generation or other load, by employing the properties of suitably constrained aerofoil wing sections immersed in and interacting with the surface water agitated by wave action. As opposed to the arrangement referred to above, in die present invention, the wing or wings are positioned as close as practicable to the surface where water movement is at its maximum and constrained against substantial vertical movement thus utilizing the kinetic energy of the moving water direcfly rather than using the wave induced movements of the floating body to move die wing or wings.

Disclosure of Invention

With the above and other objects in view the present invention resides in a first aspect in a metiiod of extracting energy from waves by using an aerofoil sectioned wing and cause said wing to move in a desired direction along a path, comprising the steps of

(1) at least partially submerging said wing in water agitated by wave action with its leading edge forward in the said direction of travel and its chordal plane substantially parallel to said direction.

(2) supporting said wing for movement along said path and

(3) constraining said wing against substantial movement perpendicular to said path. The constraint for the wing may comprise an external fixed mounting such as the seabed or a body having a large external mass, that is a body having a natural period of oscillation substantially slower than the ambient wave period. Alternatively, the constraint for the wing may comprise an external object or arrangement of objects placed deeper below the surface where water movement is less, having a hydrodynamical resistance to perpendicular movement

In an alternative aspect, many wings or assemblages of wings for example, in the form of rotors may be rigidly interconnected and spaced over a distance preferably longer than the wave length of the waves so that individual wings or assemblages of wings, being at different positions in the wave cycle, generate forces perpendicular to die direction of wing motion that oppose the perpendicular forces generated by other individual wings so that forces perpendicular to the direction of travel cancel each other out.

In yet another alternative aspect, the present invention provides one or more elongated wings, supported at intervals as necessary, preferably as long as or longer than the wavelength of the ambient waves so that different areas along a wing are acted upon by different parts of the wave cycle so that whilst some areas along the length of the wing experience a perpendicular force in one direction, other areas experience a counteracting perpendicular force and thus the nett forces perpendicular to the wings direction of movement are minimal or zero effectively constraining each wing or assemblages of wings by a statistical averaging effect.

In one preferred arrangement the wing or wings are supported for rotation about an axis in a rotor assembly adapted to be associated witii power generating means or other load. The swept path of said wing or wings may constitute a planar, conical, spherical, cylindrical or any other surface and die rotor assemblies may be individual or ganged together in any number.

In anodier preferred arrangement, the wing or wings may be secured to the hull of a ship or other body .to extend laterally thereof and at suitably spaced apart positions along the hull to be exposed to water agitated by wave action and so that the leading edges of die wings are forward in the direction of normal movement of the vessel and d e chordal plane thereof is substantially parallel to that direction. So diat the lift force components in a direction perpendicular to the chordal planes substantially cancel each other out, die region of the body supporting die wings is suitably longer than the wave length of waves encountered. Preferably such wings are pivotally mounted to die hull for movement about a substantially vertical axis to be pivotal from a laterally extending operative position to an inoperative position adjacent to the hull. Suitably biasing means are associated with the wing or wings to permit pivotal movement thereof against the bias in the event of an obstruction being encountered or the wings being overloaded. The wing or wings may , as well as or as an alternative to the above, be provided with a pivotal connection to the hull to permit limited pivotal movement about a substantially horizontal axis against a bias to absorb overloads caused by exceptionally large waves.

In each of the above situtations it is preferred diat the wings have a high aspect ration preferably greater than five to one to maximise energy transfer from the waves. Brief Description of Drawings

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Reference will now be made to the accompanying drawings which illustrated preferred embodiments of the invention and wherein :-

Fig. 1 illustrates schematically die principles of wave motion

Fig. 2 illustrates schematically die principles of generating thrust from a aerofoil sectioned wing subject to wave motion.

Figs. 3 and 4 illustrate in plan and elevational views a ship provided with aerofoil sectioned wings according to die present invention

Figs. 5 (a) to (d) Ulustrate a preferred means of mounting the wings to the hull of the ship of Figs. 3 and 4 and various modes of the wing Fig. 6 illustrates in sectional view the preferred means of control of the wing attitude

Fig. 7 is an elevational view of a yacht provided with adjustable aerofoil wing assemblies according to the present invention.

Figs. 8 and 9 are respective plan and elevational views of a preferred form of adjustable aerofoil wing assemblies Figs.lO and 11 are perspective views of die support core and wings of die wing assembly of Figs. 8 and 9 Figs. 12(a) to (d) Ulustrate die manner of adjustment of die wing assembly of Figs. 8 to 11 Figs. 13 and 14 illustrate alternative forms of adjustable wing assemblies

Fig. 15 is a perspective partly cut away view of a further alternative form of adjustable wing assembly Fig. 16(a) to (d) illustrate various attitudes of die wing assembly of Fig. 15 Fig. 17 illustrates die basic form of a simple rotor according to the invention

Figs. 18 and 19 illustrate in plan and elevational view an alternative form of rotor assembly Fig. 20 is a perspective view of ganged rotor assemblies of the type illustrated in Figs. 18 and 19 Fig.21 is a perspective view of a cylindrical rotor assembly according to die present invention Fig. 22 is an end view of the rotor of Fig. 21 in its operative attitude relative to wave motion. Figs. 23 to 27 illustrate various applications of the above rotor assemblies.

Best Mode for Carrying Out the Invention

Referring to the drawings and firstly to Fig. 1 there is illustrated schematically the motion of water particles in a wave. As illustrated by die arrows, die water particles revolve in a generally circular path or orbit at or below the surface of die water and die motion of die particles and die position they occupy give die wave its shape at any particular time. A normal ocean surface represents the sum of motions generated by many simple wave patterns of different lengdis, amplitudes and directions. Each of the component wave patterns influence each particle of water and tiiis influence may be expressed as a vector of velocity and direction. It is an object of the present invention to derive from the kinetic energy of die water particles close to die surface of the water a usable thrust using aerofoil sectioned wings.

As illustrated in Fig. 2, an aerofoil sectioned wing 10 in accordance witii die present invention is arranged for movement along a path 11 so as to be subject to die motion of various water particles of a wave some of which are represented by die arrows numbered 1 to 8 about die circle 12. If die vector arrow 8 is considered,

the apparent flow as seen by the moving wing is represented by the vector arrow 13 which is at an apparent angle of attack of Θ8 to the wing 10. In accordance witii the properties of aerofoil sectioned wings a lift force perpendicular to die apparent flow as represented by die vector arrow 14 will be generated. Whilst drag (represented by die vector arrow 15) is also created parallel to the apparent flow, a resultant thrust represented

5 by the arrow 16 will be generated parallel to the wing chord 17(provided that the angle of attack of the wing is greater than the lift/drag angle). A similar situation exists when water particle flow represented by die vector arrow 2 is considered.

For water particle flow in the positions indicated by die arrows 2,3,4,6,7 and 8 a nett tiirust in the relative direction of movement of the wing 10 is created. At positions 1 and 5 at the crest and trough of the wave a

LO nett drag is created however tiiis only lasts for a small proportion of die cycle so that an overall nett thrust results in the relative forward moving direction of die wing 10.

The generation of thrust as above may be applied to many different situations for example to a ship 18 as illustrated in Figs.3 and 4. In tiiis embodiment, die ship 18 is provided witii a plurality of aerofoil sectioned wings 19 which are fixedly secured to opposite sides of die hull 20 of the ship 18 at spaced intervals to

15 project in use laterally outwardly tiierefrom. The ship 18 acts as a rigid spine linking die wings together so d at the components of the lift forces, generated by die wings under die influence of the wave generated water movement, perpendicular to die direction of travel substantially counteract each otiier and thus act as a statistical constraint against substantial movement of die wings 19 in a direction generally perpendicular to the forward motion of die ship (and wings) which in this instance is substantially horizontal. Interaction of

20 die wings 19 with the waves occurs also because die ship, having a large mass, has a natural period of oscillation substantially greater than the ambient wave period and also substantial inertial, hydrodynamic and archimedian resistance to acceleration perpendicular to its direction of travel.

In accordance witii the principles described above, die wave motion acting upon die respective wings 19 will cause generation of thrust by each wing 19 in die direction of forward motion of die ship 18 to diereby

25 assist in that forward motion enabling a reduction in drive power required to be produced by conventional drive systems and diereby a reduction in fuel costs. Any motion which die ship 18 develops due to the waves such as roll or pitch will also be converted by interaction of the wings 19 with die water to a nett forward tiirust and further stabilise the ship 18 as such motions will be damped by being converted to tiirust. Preferably the wings 19 have a high aspect ratio for maximum efficiency of energy transfer and preferably greater than five

30 to one.

The wings 19 as above may be secured to die ship during construction or alternatively be retrofitted to existing ships. For this latter purpose, and as illustrated in Figs.5 (a) to (d),a hollow elongated spine 21 carrying the wings 19 may be secured to opposite sides of the ship's hull 20 for example by welding. Preferably, the wings 19 are secured to the spine 21 for pivotal movement about a generally vertical axis 35 22 and die spine 21 is provided with a longditudinal slot or recess 23 so that die wings 19 may be pivoted from an outwardly extending attitude shown in Fig. 5(b)to a folded stowed attitude shown in Fig. 5 (a)where the wings 19 are located substantially wholly within die recess or slot 23. This arrangement permits die wings to be stowed against die side of die ship for docking or other purposes. Preferably also and as shown

in Figs. 5(c) and (d), die wings 19 are constructed so as to be pivotal in a vertical plane under die influence of a biasing force so as to relieve overstressing of the wings. The above principle of energy extraction from waves to apply a thrust force to vessels may be applied to torpedoes, submarines or surveillance vessels where it is important that die motive power be as quiet as possible. Fig. 6 illustrates a preferred mechanism for controlling the wing 19 in die above manner. In this arrangement the wing 19 includes a first part 24 provided witii a pivot pin 25 which is mounted for rotation about a vertical axis in bearings 26 in the spine 21and a second part 27 pivotally connected to die first part 24 for pivotal movement about a horizontal axis suitably by means of a further pivot pin 28. An hydraulic or pneumatic ram 29 is located in die spine 21 and includes a plunger 30 which may act upon a flat 30 formed in d e shaft 25 to maintain when the ram is pressurised, the wing 19 in an outwardly extending operative attitude.The pressure applied to the plunger will determine die release point of d e wing 19 to permit the wing to pivot forwardly or rearwardly in the event of momentarily overstressing by waves larger than the design limit or by floating objects, whilst when the wing 19 is to be moved to its inoperative attitude shown in Fig. 5(a), hydraulic pressure is released to remove the bias. The second part 27 of the wing 19 is preferably maintained in a substantially horizontal attitude or in an attitude where its chordal plane is substantially parallel to die direction of motion by further biasing means 31 arranged witiiin the first part 24 of die wing. In this instance the biasing means 31 comprises a spring loaded plunger 32 arranged for reciprocation in a recess 33 within the wing part 24. The plunger 32 is normally biased into engagement with a flat 34 on the end of die wing part 27 to maintain diat part in an outwardly extending attitude however in the event of overstressing, the wing part 27 may overcome the biasing force of die plunger 32 and pivot in a vertical plane. Of course, die wing part 24 need not have an aerofoil configuration and it will be realised d at many different biasing structures may be employed to achieve die above results. The biasing arrangements may also be employed separately or in combination.

In a further embodiment, aerofoil sectioned wings may be applied to die hulls of small boates or yachts as shown in Fig. 7. In this instance, die yacht 35 includes wing assemblies 36 supported on or in the hull 37 adjacent to die bow, keel and skeg. Smaller boats and yachts are generally shorter tiian die wavelengdis of waves they encounter, travel at slower speeds tiian large ships, and are generally subject to greater pitching and rolling motion than encountered by ships. In such situations the angle of attack of the flow of water impinging upon fixed wings may increase to such an extent so as to cause the wing to stall. To overcome this disadvantage, die wing assemblies 36 illustrated in Fig. 7 are made self-adjusting so that the angle of attack of the symmetrical aerofoil wing sections 38 of d e wing assemblies 37 do not exceed die optimum angle. For tiiis purpose and as more clearly illustrated in Figs. 8 to 11, each wing assembly 36 includes a support core 39 which may be suitably formed from extruded nylon or otiier material and which is mounted through the hull, keel and skeg of die yacht in any suitable manner for example by forming a hole theredirough to neady accept die core 39 which is cut to an appropriate length to fit neady in position and which may be secured in position by adhesives, fibreglass or the like. The pair of opposed wing sections 36 are provided on tiieir operative inner ends witii respective brackets 40 which are fixedly interconnected by a pair of upper and lower pivot bars or shafts 41 offset on opposite sides from the central chordal plane of die

- 6 - wings 38 and rearward of die centre of lift effort of the aerofoil section as shown more clearly in Figs.12(a) to (d). The angle between die line extending between die pivot axes of the pivot bars and die centre of effort and a line perpendicular to die chordal plane of die wing determines the angle of attack the wing maintains in use. The pivot bars 41 extend freely dirough respective symmetrical slots or apertures 42 in die support core 39 each of which includes an arcuate portion 43 centred on a pivot portion 44 forming part of and terminating the opposite slot 43. As will be apparent the slot portions 44 extend inwardly towards each otiier.

In use.one pivot bar 41 may seat in the pivot portion 44 of one slot 42 whilst die opposite pivot bar41 is free for but constrained for limited pivotal movement along the arcuate portion 43 of die opposite slot 42, the angular extent of which determine the limits desired jn die adjustment angles of of die wings 38 ODependant upon die apparent angle of die flow of water to die wings 38, die opposite bars 41 will seat in die opposite pivot portions 44 of the slots 42 and permit limited pivotal movement of the wings 38.

Operation of die wing assemblies 36 is more clearly illustrated in Figs. 12(a) to (d) witii die arrows marked 45 indicating die apparent direction of water flow at any one time consequent on wave motion and die arrows _ 46 indicating the direction of lift generated by the wings 38. In Fig. 12(a), the angle of attack is relatively 5small and die lift direction through die centre of lift of die wing is offset from the pivot axis of the lower bar 41 defined by die lower pivot recess portion 44 tiius creating a moment tending to increase the angle of attack however tiiis is limited by die upper bar 41 abutting against the end of die upper slot portion 43. As die apparent flow direction changes as shown in Figs. 12 (b), the lift will first act through tiie pivot axis of the lower bar 41 so that no moment is created and tiien swing to a position past the pivot axis creating a 0 moment causing pivotal movement of the upper bar 41 in die upper slot portion 43 and pivotal movement of the wings 38 to maintain optimum angle of attack of the wings 38 to apparent flowor angle of attack within a predetermined range.

Fig. 12(c) illustrates die position of the wings 38 and pivot mechanism at zero angle of attack witii neither pivot bar 41 seated in its pivot recess 44 whilst Fig. 12(d) illustrates the wing position for opposite apparent 5 flow to the wing. In use, the pivot points or axes of die wing assembly 36 will "switch" between die upper and lower pivot axes depending upon die apparent flow direction to maintain die wings 38 in their desired range of angle of attack.

In some circumstances, for example when applied to a hydrofoil-type arrangement intended to provide a constant lifting force irrespective of wave movement, die wings 38 may be supported for controlled pivotal movement about a single pivot axis either located above or below the wings 38.

The above described arrangements may also be applied to single wing sections as shown in Figs. 13 and 14. In Fig. 13, a single wing 45 is supported at each end by respective support cores 39' similar to the type 39 shown in Figs. 8 to 12. In tiiis arrangement, each support core 39' is sandwiched between a pair of end plates or members 46 which are interconnected rigidly by respective pivot bars or shafts 47 , which extend dirough die respective slots 42' to be maintained captive and be movable freely therein in die manner described above The opposite ends of die wing sections 45 are secured to die inner end plates 46 so as to be guided for movement in a manner similar to diat shown in Figs. 12(a) to (d). In tiiis configuration, die cores 42' may be supported in a frame extending below die hull of die vessel or arranged on one or botii sides of die

hull. Alternatively the opposite support cores 42' may be secured to die spaced hulls of a multihull vessel such as a catamaran or a trimaran.

In Figs. 14, a single wing 48 is supported in cantilever like fashion from a support cores39 " which may be secured to the hull of the vessel in any suitable manner for example in a bore in the hull and adhesively secured dierein. Suitably, die wings 38, 45 or 48 may be made of fibreglass in a mould whilst die pivot bars or shafts 41 and 47 are preferably formed of a corrosion resistant material suitably stainless steel.

Referring now to Fig. 15 tiiere is illustrated an alternative form of adjustable wing assembly 49 according to the present invention. In this embodiment, die adjustment is internal and for tiiis purpose, tiie wing assembly 49 includes a symmetrical aerofoil sectioned wing portion 50 having a central longitudinally extending aperture 51 and a support 52 which extends dirough the aperture 51. The recess 40 includes opposite arcuate surfaces 53which are centred on die desired pivotal axes of d e wing portion 50 and die support 52 is provided with complimentary configured opposite surfaces 54. The aperture 51also includes opposite leading surfaces 55 which converge from the curved surfaces 53 towards die leading edge of die wing portion 50 and die support 52 is provided witii a corresponding wedge shaped converging leading portion 56. The support 52 and wing portion 50cooperate in the manner shown in Fig. 16(a) to (d) and it will be seen that when the apparent flow is from below the wing portion 50 in the drawings, the wing portion 50 will be urged against the support 52 with d e complimentary curved surfaces 53 and 54 cooperating and guiding die pivotal movement of the wing portion as the angle of attack varies. As die angle of attack decreases towards zero, die corresponding converging leading surfaces 55 and 56 of die support ^d wing will cooperate to maintain the wing portion 50 at a substantially zero angle of attack as it moves rearwardly relative to the support 52. As the flow direction changes towards die opposite side of die wing portion 50,dιe wing portion 50 will slide forwardly by virtue of die cooperation between the converging surfaces 55 and 56 until the opposite complimentary curved surfaces 54 and 53 engage to guide die wing portion 50 in a controlled pivotal movement , the extent of which is limited by die rear split portion 57 of the recess 40 which receives the "tail" of die S ξ Dt± 52- - Thus die wing portion 50 will maintain optimum angle of attack or have an angle of attack witiiin a predetermined range irrespective of die direction of water flow in the same manner as die mechanism of Figs.8 to 12, that is the wing is permitted to rotate about a pair of alternate pivot points positioned outside of, and on eitiier side of die chordal plane and rearward of die center of lift of die aerofod with a means of switching between pivots as the flow changes from above to below .Thus in the first described arrangement the pivot points are "real" whilst in the second (internal) arrangement die pivot points are "virtual", being the centers of curvature of the cooperating curved surfaces 53 and 54.

In a particularly preferred construction and as shown in Figs. 15 die wing portion 50 is formed of a plurality of juxtaposed individual segments 58 each, of which has the cross section illustrated in Fig. 16. Each individual segment 58 may pivotally adjust independently on the support 52 to the flow conditions at its particular position so as for example to shape die aerofoil sectioned wing portion 50 to a twisted longitudinal form so that die optimum angle of attack is maintained at all positions along die lengtii of the wing. Thus die appropriate angle of attack may be maintained botii at the tip and root of the wing. Preferably the

individual wing segments 58 as above are covered with a flexible skin material 59 to improve streamlined flow about the wing.

The principles of the present invention may also be applied to cause rotation of a rotor assembly for driving power generation means such as an electrical generator or any other load. The rotor assembly may include one or more rotors 60 as shown in Fig. 17 each of which includes a pair of aerofoil wing sections 61 arranged in end to end relationship in opposite configurations so that dieir leading edges point in the same direction of rotation. This rotor 60 is provided witii a central shaft or rotational axis 62 arranged substantially normal to die chordal planes of the wing sections 61. The shaft 62 may be supported for rotational movement about a vertical axis with die rotor 60 submerged in water subject to wave action and in accordance with die above described principlcs,thrust will be extracted by the wing sections 61 from die waves to cause rotation of the rotor 60 in the direction indicated by the arrows. The shaft 62 may be coupled to a conventional electrical generator so diat rotation thereof as a consequence of rotation of the wing sections 61 will drive die generator for the generation of electrical power. It will also be recognized that in accordance witii the above principles, the shaft 62 may be arranged for rotation about any axis for example a horizontal axis , water flow impinging on the wing sections 62 causing rotation of the rotor 60 in one direction only.

Figs. 18 and 19 illustrate an alternative form of rotor assembly 63 which in this instance includes a central hub 64 and a plurality of wing sections 65 (in this instance four) extending outwardly from the hub 64. In this rotor the wing sections 65 taper in cross section towards dieir tips to reduce tip losses. This rotor assembly 63 when submerged in water subject to wave action will function in the same manner as the Fig.17 embodiment to convert kinetic energy of the waves into a thrust to cause rotation of die rotor assembly 63.

A. plurality of rotor assemblies 63 of die type illustrated in Figs.18 and 19 may be ganged together on a single shaft as illustrated in Fig. 20. Furthermore, the shaft 66 to which the rotors 63 may be secured may eitiier comprise a rigid shaft or alternatively a flexible member such as a cable and suitably the shaft or cable carrying die rotor assemblies is longer than die expected wave length.

In an alternative construction shown in Fig. 21, a rotor assembly 67 for the above purpose may be constructed to include a plurality of aerofoil sectioned blades 68 which are supported at a position radially spaced from d e axis of rotation of the rotor assembly67 to extend generally longitudinally relative to that axis. Preferably, the blades 68 are supported on respective radially extending arms 69 which are interconnected at dieir inner ends suitably via a hub 70. Preferably the blades 68 are symmetrical about the circular circumference line along which they travel and extend along die surface of revolution of the rotor assembly. Alternatively, the blades in cross section may be tangential to the surface of revolution. The wing sectioned blades 68 in tins embodiment are arranged to sweep out a cylindrical path on rotation of die rotor assembly 67. In an alternative embodiment, die wing sectioned blades 68 may lie along die surface of a cone so as to sweep a conical surface on rotation and in tiiis instance die blades are suitably symmetrical about that conical surface. As shown in Fig.22, tiiis rotor assembly 67 is supported for rotation about an axis extending generally parallel to the wave fronts so that maximum energy is transferred from the agitated water particles to the wing sectioned blades 68 to cause rotation of die rotor assembly 67.

Fig. 23 illustrates a typical application of the rotors of the present invention.In tiiis arrangement a shore based generating plant 72 is driven by a rotor assembly 73 comprising a shaft 74 having a plurality of rotors

75 mounted tiiereon as shown in Fig. 24. The shaft 74 being connected to the shore based generating plant acts as a restraint against movement of die aerofoil sectioned blades of die rotors in a direction perpendicular to their chordal planes and the kinetic energy of wave agitated water particles will be converted into a unidirectional ti rust by die aerofoil sectioned blades to rotate the rotor assembly 73 and drive die generating plant.

In the embodiments of Figs. 25 and 26, the principles of the present invention are applied to power navigation lights. In Fig. 25, the navigation light 76 is supported on a floating buoy 77 or other floating body which also defines a support for an electrical generator 78 which is adapted to power the light 76. The generator shaft is coupled only to die upper rotor 80 which is supported rotatably on a shaft 81 whilst a further rotor 82 of opposite configuration and which dierefore rotates in an opposite direction is supported on the shaft 81 at a spaced position from the rotor 80 so that the perpendicular components of- the lift forces generated by the respective rotors cancel each other out. It will also be seen seen that the shaft 80 may be anchored by means of an anchor line 83 so diat die light may be located in a desired area of operation. Alternatively, the blade 80 may be fixed to die generator body and die generator shaft secured to die rotor 82, die generator body and shaft being caused to rotate in opposite directions by die respective rotors.

In Fig.26, the constraint against vertical movement of the rotor due to die perpendicular components of die lift forces is provided by die sea bed. In tiiis embodiment, a navigation light 84 is again powered by a generator 85 driven by a rotor 86 for example of the type illustrated in Fig. 18. The rotor 86 is fixed against vertical movement by means of a support 87 fixed to the sea bed 88. In both die embodiments of Figs. 25 and 26, the generator for the navigation lights are driven by rotors which will extract kinetic energy from the waves and convert that energy into thrust.

In Fig. 27, the constraint against substantial vertical movement of the rotor is provided by die hull 89 of a yacht. In tiiis arrangement, a generator, bilge pump, or other load 90 is supported in a fixed position on a frame 91 which extends from die stern of die vessel. The load 90 is coupled to a rotor 92 which will rotate when subject to wave action to thereby drive die load.