GB1594585A

GB1594585A - Extracting energy from waves in liquids

Info

Publication number: GB1594585A
Application number: GB42061/76A
Authority: GB
Original assignee: Sea Energy Associates Ltd
Current assignee: Sea Energy Associates Ltd
Priority date: 1977-11-15
Filing date: 1977-11-15
Publication date: 1981-07-30

Description

(54) EXTRACTING ENERGY FROM WAVES IN LIQUIDS (71) We, SEA ENERGY ASSO CIATES LIMITED, a British Company of Nicholson House Maidenhead, Berkshire SLJ 1 LF, do hereby declare this invention for which we pray that a Patent may be granted and the method by which it is to be performed to be described in and by the following statement:- This invention relates to a method of and an apparatus for extracting useful energy from wave-motions in a body of liquid.

As is well known, the wave motions at the surface of a body of liquid such as a lake, sea or ocean, brought about at least in part by the action of winds, represents, as far as oceans are concerned, a virtually infinite reservoir of energy. It is also well known that it would be desireable for a supply of energy from this large reservoir of energy to be converted into more useful form, such as electrical energy so that it will be used on land for heating, lighting motive power and so on. Because of the awareness of the desireability of extracting energy from wave motions, many attempts to invent suitable converting apparatus have been made, varying from the simple to the sophisticated.

Despite the large amounts of work done in this field, and the progress made, there is still no equipment in operation to any extent to provide a reasonable amount converted energy.

Some success has been achieved towards utilizing the energy of sea waves by supporting a semi-buoyant structure beneath the surface in such a way that it rocks up and down about a pivot under the action of the waves and some of the energy represented by the reciprocation of the mass of the structure is converted into a generally usable form. However, the motion of the waves is variable both in frequency and amplitude so that the system described above has to be designed to accommodate the frequency and amplitude variations, and this complicates the apparatus and increases its cost. Moreover, the energy derived from the conversion of the reciprocating motion varies between zero and a maximum during each wave cycle which is disadvantageous.

The present invention aims at finding a method and a means for the extraction of energy from the energy in waves in a body liquid (referred to hereinafter for simplicity as "the sea").

Also surge and heave forces which are relatively at right angles, are excercised on the structures and it is desirable that the structure should extract energy which is available in surge and in heave.

It appears that the liquid particles defining the crests and valleys of waves in liquids move generally in orbital paths, although there may be progression and regression movements, because of the influence of currents, cross winds and so on, and it is also possible to have standing waves when the particles move up and down.

Generally, however, the said oribital movement is involved and the present invention is based upon utilization of this phenomenon.

According to one aspect of the invention there is provided a method of convering into useful energy, energy in the waves in the sea, the method comprising providing in the sea so as to be moved in orbital movements by the energy in the waves, a buoyant member or unit which is restrained from moving in at least two uncoupled modes by fluid pressure ram means so that as the member or unit moves orbitally the ram means is contracted and expanded so as to act as a pump to provide fluid under pressure output which can be converted into useful energy. By the expression "two uncoupled modes" is the mathematical expression to indicate reciprocatory vectors arranged at an angle. The vectors in this case are displacement vectors.

Preferably, the buoyant member or unit is a sleeve of which the axis orbits round the axis of a spine in the sleeve between which spine and sleeve the ram means is arranged.

Alternatively, instead of a sleeve orbiting round the axis of a spine, the buoyant member may be a cylindrical member the centre of gravity of which is arranged to orbit round an axis fixed relative to a cage surrounding the cylindrical member between which cage and cylindrical member the ram means is arranged.

In another arrangement the buoyant member is a sphere having freedom to orbit about an infinite number of axes.

According to a further aspect the invention provides apparatus for converting energy in waves in the sea into a more useful form, the apparatus comprising a buoyant member or unit for positioning in the sea so as to be moved in orbital movements by the energy in the waves, ram means connected to restrain the orbital movements of the buoyant member or unit in at least two uncoupled modes so that the ram means can expand and contract to act as a pump to provide fluid pressure output.

Preferably, the ram means comprises a plurality of pressure cylinders arranged at angularly spaced locations relative to the centre of gravity of the buoyant member or unit (when stationary) whereby on the approach of the buoyant member or unit towards a cylinder, a quantity of fluid under pressure is displaced from said cylinder which fluid under pressure can be made to do useful work. Preferably, means are provided for combining or adding the quantities of fluid under pressure displaced by the fluid pressure cylinders.

Suitably, the buoyant member or unit is a sleeve located so that it is adapted to orbit so that its axis orbits round the axis of a spine forming the support means.

Alternatively, instead df a sleeve orbiting round the axis of a spine, a cylinder member is arranged to orbit round an axis fixed relative to a cage surrounding the cylinder member.

In another arrangement, the buoyant member is a sphere having freedom to orbit about an infinite number of axes.

Ernbodiments of the invention will now be described by way of example, with reference to accompanying diagrammatic drawings, of which; Figure 1 is a section perpendicular to an assembly of a sleeve and spine; Figure 2 is a perspective view of an embodiment comprising a spine common to a plurality of similar sleeves; Figure 3 is a perspective view of the apparatus according to a second embodiment of this invention.

Figure 4 is an end view of the apparatus shown in Figure 3; Figure 5 is a view illustrating further embodiment of apparatus according to the invention.

Referring to Figure 1 a support means in the form of a spine 1 is located within a moveable member in the form of sleeve 2 of which the internal diameter is substantially greater than the outer diameter of the spine.

The sleeve is supported by light hydraulic rams 6 which are located in cylinders 5 located symmetically about the spine 1. The inner surface of sleeve 2 bears on the rams 6 through rollers 4 mounted on the ends of the rams.

Each cylinder 5 is provided with an outlet 8 and an inlet 9 which lead respectively through valves 10 and 11 respectively to a common high pressure pipe 12 and low pressure pipe 13. The high pressure pipe 12 is connected to one side of a variable displacement hydraulic motor 14, whilst low pressure pipe 13 is connected to the other side of motor 14. The hydraulic motor is operatively connected to a generator 15 (or to a pump for connection to a generator unit) for the production of electrical energy produced by the movement of the system as will be described below.

The apparatus described provides a practical way of converting the cyclic orbital wave motion of a submerged cylinder into usable energy and because of the arrangement of rams the device can extract energy from heave and surge forces, or in other words in two uncoupled modes.

The assembly of spine and sleeve is submerged preferably just below the surface of the sea with its longitudinal axis substantially horizontal.

Under the action of the wave motion in the sea the sleeve 2 moves relative to spine 1 in such a way that the axis of the sleeve orbits round the axis of the spine in sympathy with the motion of the surrounding water. In doing so the internal surface of the sleeve moves towards the spine in a first radial direction, say the direction corresponding to the location of ram and cylinder means 3a, whilst at the same time moving away from the spine in the direction corresponding to ram and cylinder means 3b, and the relative movement towards and away from the spine progresses circumferentially of the spine, acting in the direction of successive pairs of ram and cylinder means. During the inward movement of any of the rams, hydraulic fluid is forced through the corresponding valve into the common high pressure tube 12, from whence it moves into the hydraulic motor 14 which converts the energy in the fluid to mechanical shaft energy. The fluid returning from the motor 14 flows into low pressure tube 13 and thence through the appropriate valve into the diametrically opposed cylinder, thus forcing its ram outwardly so that its roller 4 contacts the inner surface of the sleeve 2. The inward working strokes of the rams occur successively around the circumferences of the spine, each pressure stroke providing a flow in the same direction into the hydraulic motor 14 via the common input pipe 12.

The pressure exerted by the sleeve on the rams 6 is dependant on the energy of the particular wave motion, and the hydraulic motor 14 is so constructed that the angle of swash is controlled by the pressure applied.

The movement of the swash plate of the hydraulic motor is controlled by a servo mechanism which is programmed to react appropriately to wave loading and- velocities so as to maximise energy conversion.

In a typical installation the diameter of the sleeve is 17 meters and the stroke of the rams is 2 metres. The axial length of the sleeve is 30 metres, which is only a fraction of the crest length of a typical wave as for example the North Sea. It is desirable, however, that each spine should accommodate several sleeves, and that the spine be long in relation to the crest length, and may in fact be of the order of 500 metres.

The arrangement of a plurality of sleeves on a common spine is shown in Figure 2 of which the apparatus comprises sleeves 20, 21 and 22. Each section corresponding to a sleeve is joined to the next by ajoint such as 25 and 26 enabling limited relative rocking of the spine elements. In such a joint a knuckle such as 24 may accommodate a buoyancy tank of such dimensions as to support the apparatus with sleeves just below the surface of the water. The sleeves are non-rotating, and if it is required to maintain a water-tight joint at the edge 23, such a joint may be provided by a simple bellows construction. However, it may not be necessary to keep the annular space between the sleeve and the spine free from water, and indeed the sleeve may be perforated.

Referring now to Figures 3 and 4, there is shown a cylinder member 110 which is surrounded by a cage 112. The cage 112 is made up of a number of axially extending frame members 114 connected by braces 116 forming a rigid structure. The cylinder member 110 is supported centrally of the frame structure, which is hexagonal in end view as seen in Figure 4, by means of six piston and cylinder devices 118, respectively arranged at the corners of the hexagonal framework. The piston and cylinder devices are arranged so that the cylinder portions extend outwardly from the cage, whilst the piston rods extend inwardly and at the inner end of each piston rod is a follower roller assembly 120.Although not shown in Figures 3 and 4, these rollers 120 engage in tracks in the cylinder member 110 so that they are unable to move radially relative to the cylinder member 110, but the member 110 can rotate freely relative to each roller assembly 120.

In the use of the apparatus shown in Figures 3 and 4, it is located in a body of water similarly to the apparatus of Figures 1 and 2, for example at sea, so that the cylinder member 110 comes under the influence of the motion of the waves in the body of liquid. The wave motion causes the member 110 to move orbitally so that the centre axis of the cylinder member 110 orbits around the notional spatial axis lying centrally of the cage 114/116. This has the effect similar to the Figure 1 embodiment that it operates in two uncoupled modes and the piston and cylinder devices 118 are contracted and expanded in turn and in sequence, and when each is contracted it is being operated in a power stroke, and when it is being extended i.e. when it is opposite the device being contracted, it is operating in an induction stroke.The piston and cylinder devices 118 are interlinked so as to supply a motor indicated by numeral 122 in Figure 4 in sequence, and the motor in turn drives an electrical generator from which electrical energy can be taken, similar to the arrangement as described in relation to Figure 1.

It is to be appreciated that the apparatus described operates essentially in the same manner as the apparatus described in relation to that shown in Figure 1, and the apparatus has the same function. In a typical installation, there will be a plurality of apparatus each described, the apparatus being arranged in axial alignment and in the form of a string. Adjacent apparatus may be- connected by means of knuckling or flexing joints such as described before and the outputs from the respective motors or generators of the apparatus may be connected in parallel to provide gross energy output.

Referring finally to Figure 5, instead of having a cylindrical central mass 110 which orbits in use a sphere 224 is utilized. Again, there are shown six piston and cylinder devices 218 which operate in a diametral plane of the sphere, but as a sphere is used, it will be appreciated that the piston cylinder devices can be arranged in a number of different radial planes and the sphere can be allowed in fact to orbit so that its centre of gravity moves in any of an infinite number of orbits, and this may prove advantageous in some cases, as it will be able to absorb more of the energy from mixed seas on which the waves approach the spine from different directions by extracting energy in three uncoupled directions; the sphere arrangement may absorb some energy which may be missed by a cylinder absorber.Instead of the member being exactly spherical as shown, it may be for example of rugby ball or ovaloid, shape.

With any of the apparatus as described, it is believed that it will be possible to obtain a continuous and substantially constant level of energy output in view of the fact that it absorbs in two uncoupled directions and the apparatus can be fabricated much more simply than an apparatus involving a rockable structure such as is used in the conventional apparatus.

WHAT WE CLAIM IS: 1. A method of converting into useful energy, energy in the waves in the sea, the method comprising providing in the sea so as to be moved in orbital movements by the energy in the waves, a buoyant member or unit which is restrained from moving in two uncoupled modes by fluid pressure ram means so that as the member or unit moves orbitally the ram means is contracted and expanded so as to act as a pump to provide fluid under pressure output which can be converted into useful energy.

2. A method according to claim 1 wherein the buoyant member or unit is a sleeve of which the axis orbits round the axis of a spine in the sleeve between which spine and sleeve the ram means is arranged.

3. A method according to claim I, wherein the buoyant member is a cylindrical member the centre of gravity of which is arranged to orbit round an axis fixed relative to a cage surrounding the cylindrical member between which cage and cylindrical member the ram means is arranged.

4. A method according to claim 1, wherein the buoyant member is a sphere.

5. A method of converting into useful energy, energy in waves in the sea, substantially as hereinbefore described, with reference to Figures 1 and 2, Figures 3 and 4 or Figure 5 of the accompanying drawings.

6. ' Apparatus for converting energy in waves in the sea into a more useful form, the apparatus comprising a buoyant member or unit for positioning in the sea so as to be moved in orbital movements by the energy in the waves, ram means connected to restrain the orbital movements of the buoyant member or unit in at least two uncoupled modes so that the ram means can expand and contract to act as a pump to provide fluid pressure output.

7. Apparatus according to claim 6, wherein the ram means comprises a plurality of fluid pressure cylinder arranged at angularly spaced locations relative to the centre of gravity of the buoyant member or unit (when stationary) whereby on the approach of the buoyant member or unit towards a cylinder, a quantity of fluid under pressure is displaced from said cylinder, which fluid under pressure can be made to do useful work.

8. Apparatus according to Claim 7, wherein the means are provided for combining or adding the quantities of fluid under pressure displaced by the fluid pressure cylinders.

9. Apparatus according to claim 6, 7 or 8, wherein the buoyant member or unit is a sleeve of which the axis is adapted to orbit around the axis of a support spine.

10. Apparatus according to claim 6, 7 or 8, wherein the buoyant member or unit is a sleeve of which the axis orbits round the axis of a spine in the sleeve.

I I. Apparatus according to claim 6, 7 and 8 wherein the buoyant member is a cylindrical member the centre of gravity of which is arranged to orbit round an axis fixed relative to a cage surrounding the cylinder member.

12. Apparatus according to claim 6, 7 or 8, wherein the buoyant member is a sphere.

13. Apparatus for converting energy in the waves in the sea into a more useful form, substantially as hereinbefore described with reference to Figures 1 and 2, Figures 3 and 4, or Figure 5 of the accompanying drawings.

14. Electrical energy derived from energy in waves in the sea, and produced using method of any claims 1 to 5 or the apparatus according to any of claims 6 to 12.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. may be for example of rugby ball or ovaloid, shape. With any of the apparatus as described, it is believed that it will be possible to obtain a continuous and substantially constant level of energy output in view of the fact that it absorbs in two uncoupled directions and the apparatus can be fabricated much more simply than an apparatus involving a rockable structure such as is used in the conventional apparatus. WHAT WE CLAIM IS:

1. A method of converting into useful energy, energy in the waves in the sea, the method comprising providing in the sea so as to be moved in orbital movements by the energy in the waves, a buoyant member or unit which is restrained from moving in two uncoupled modes by fluid pressure ram means so that as the member or unit moves orbitally the ram means is contracted and expanded so as to act as a pump to provide fluid under pressure output which can be converted into useful energy.

4. A method according to claim 1, wherein the buoyant member is a sphere.