GB2204919A

GB2204919A - Wave energy apparatus

Info

Publication number: GB2204919A
Application number: GB08804247A
Authority: GB
Inventors: William B Cranston
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-05-16
Filing date: 1988-02-24
Publication date: 1988-11-23
Also published as: GB8711618D0; GB8804247D0

Abstract

The apparatus includes an elongate float 12 which is wider at its top than at its bottom and is mounted by support means 14,15 "up-wave" from the land 11 or from a structure fixed to the seabed (Fig.4) or from a movable structure and constrained to be reciprocable (pivotable and/or translational motion) in a mode which has at least a major vertical component, means 15 being provided to extract energy from the float. Other arrangements are described having floats provided with a different wedge-shaped outline and associated with different support and energy extraction means supported on the land (Figs. 5 to 8) and on the land and seabed (Figs. 9 and 10). <IMAGE>

Description

WAVE ENERGY This invention relates to wave energy apparatus, that is to say an apparatus which takes wave energy and converts it to a usable form.

It is an object of the present invention to provide wave energy apparatus which combines reasonable efficiency with realistic construction and operating costs.

The invention provides wave energy apparatus including an elongate float intended, in use, to be partly immersed and disposed transversely of the wave direction, being narrower at its base than at its top and being mounted for reciprocating motion in a mode having at least a major vertical component.

The energy in the moving float can be transferred by a transmission to be used. Normally the transmission will connect with an electric generator or the like. However, there may be situations where the transmission can provide direct mechanical energy, for example to a pump or the like.

The transmission can be the same as or separate from or a component of support means for the float.

The transmission can be an upwardly extending rod or a mounting boom or an array of levers. Preferably, however, the transmission is a tensioned cable connecting the float to other apparatus. The other apparatus can be a generator or part of a power collector serving several floats and itself connected to a generator.

The two major, generally upright surfaces of the float can be termed on outside and an inside surface, the outside surface being that which faces the waves. This surface is preferably concave, having an upper part further forward than a lower part.

The rear surface and the mounting means are co-designed to ensure that the rear surface extends parallel to the direction of movement of the float, so as to have as little interaction with the (theoretically calm) water behind the float. If the float is mounted to move in a straight line up and down the rear face will be flat planar. If the float is mounted to pivot about an axis, the rear surface will be cylindrical about that axis.

The apparatus will be mounted to be disposed "up-wave" from a supporting structure such as a moored or moving vessel or fixed structure such as land, a jetty or a seawall.

In such cases the apparatus is advantageously supported by an array of struts and tensioned cables, transmission of energy occurring by means of a cable.

Alternatively the apparatus can be mounted free" in relatively deep water, in which case a guyed mast and cable suspension system is envisaged, with the float performing substantially vertical movement.

When the apparatus is mounted on land or a structure providing a wave-reflecting sea-wall effect, the float can be generally vertically moving, and can have concave front and rear surfaces to act, in effect, in both directions. To be most effective in such a position the float must be positioned a distance W/2 from the reflecting wall, wherein W is the wavelength of the waves.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein Fig. 1 is a schematic elevation (not to scale) of a first preferred wave energy apparatus of the invention; Fig. 2 is a plan view of the apparatus of Fig.l; Fig. 3 is a perspective view of a float of a second apparatus of the invention; Fig. 4 shows a possible layout for the second apparatus; Fig. 5 is a side elevation of part of a third preferred apparatus of the invention; Fig. 6 is a side elevation showing the whole of the third preferred apparatus; Fig. 7 is a plan view of the third preferred apparatus; Fig. 8 is a sketch of a fourth preferred apparatus of the invention; Fig. 9 is a side elevation of a fifth preferred apparatus of the invention; and Fig. 10 is a plan view of the apparatus of Figure 9.

Referring firstly to Figs. land 2 a first preferred wave energy apparatus 10 is suitable for mounting on land 11 or some other structure as a vessel or pontoon. The apparatus includes a partly-immersed float 12, a pair of guyed support struts 13, cables (wire ropes) 14 and take-off transmission cables (wire ropes) 15.

The float 12 has a rear surface 16 which faces the land 11 and is cylindrical about an axis parallel to the float 12 and passing through the attachment point 17 of cables 14.

Thus as float 12 moves it (tends to pivot) about axis 17, ensuring that its rear face 16 avoids any interaction with the water behind float 12.

Forward surface 18 of float 12 is concavely curved and has a top edge 18a further away from land than its bottom edge 18b, making the float generally wedge-shaped in vertical cross section.

As waves pass the float it is rythmically raised and falls under its own weight. The cables 15 pass to a unit 19 where the linear motion of cables 15 can be converted to rotary motion to drive a generator, or can be collected to drive a shaft or other collector common to several devices 10 and connected to drive a generator or other machine.

The cables 15 will usually be pre-tensioned as by weights or springs (not shown) to take some part in holding the float 12 in position.

Figs. 3 and 4 illustrate a comparable structure 20 suitable for mounting in deeper water (say 40m deep). In the apparatus 20 a plurality of floats assemblies 21 are respectively suspended by vertical cables 22 which are combined to support and power transmission cables. A support for the whole structure is constituted by an array of guyed masts 23 and suspension cable(s) 24. Transmission cables 22 pass over pulleys suspended from cable(s) 24 and to a power accumulator/generator 25 mounted on masts 23 (or other nearby structure). Electrical power generated can be passed via a cable for use on land or elsewhere.

Each float assembly 21 includes'a float 26 comparable with float 12 and having a flat near face 27, because the float moves vertically, and a convex front surface 28 like surface 18. To constrain the free hanging float assembly 21 to vertical movement, a depending lattice array 29 is provided which has elongate vertical members 30 supporting cross members 31 streamlined to pose minimal resistance to vertical movement.

The action of this apparatus and the power extraction from the cables 22 are comparable to those of the apparatus of Figs. 1 and 2 Figs. 5, 6 and 7 illustrate a third preferred embodiment of apparatus 32 comparable in many ways to that of the first embodiment, and comprising a guyed support 33, a strut 34, a float 34a, suspension cables 34b,c and a rigid arm 35 connected to float 34a and to a power take-off 36. The float 34a is of tapered cross section and has a concave rear face 37 cylindrical about axis 37a and a convex front surface 38.

Strut 34 is guyed by cales 39, The suspension of the float 34a is such as to allow it to pivot about axis 37a in response to wave movement. The connection point between the rigid arm and suspension cable 34c acts upon a take-off device 36 to provide power to a generator or to a hydraulic power collector, power being extracted as the float moves downwards after being lifted by a wave.

Fig. 8 illustrates a fourth embodiment of wave energy apparatus 40 which comprises a float 41 supported by a combined suspension cable 42 and transmission cable 42b depending from a guyed support strut 43. Cable 42b connects with a collector or generator 44. float 41 has similar front and rear concave faces 41a, 41b. With float 41 disposed a distance W/2 from a sea wall or like reflecting barrier 45 (wherein W is the wavelength) there is at the position of float 41 a condition wherein waves approach the float 41 from both directions, hence the need for two concave, wave receiving faces 41a, 41b.

Figs. 9 and 10 illustrate a fifth embodiment of wave energy apparatus 50 which comprises a float 51 anchored by cables 52 to the sea-bed up-wave and to the sea-bed beneath the float by a combined anchor and transmitting cable 53.

Cable 53 connects with a collector or generator 54.

The invention is not limited to the foregoing examples and variations can be made. For example, various support and transmission mechanisms can be used. For example, any of the floats could be supported at by outwardly extending beams, pivoting of the beams being used to actuate an onward transmission or a collector shaft or like means.

Many other support and transmission means can be used in combination with the wedge-shaped floats.

Many other variations are possible.

Claims

1. Wave energy apparatus including an elongate float intended, in use, to be partly immersed and dispqsed transversely of the wave direction, being narrower at its base than at its top and being mounted for reciprocating motion in a mode having at least a major vertical component.

2. Apparatus as claimed in claim 1 wherein energy in the moving float is transferred by a transmission to be used.

3. Apparatus as claimed in claim 2, wherein the transmission connects with a usable power generator.

4. Apparatus as claimed in claim 3 wherein the generator is an electric generator.

5. Apparatus as claimed in claim 2, wherein the transmission provides direct mechanical energy.

6. Apparatus as claimed in claims 2, 3, 4 or 5 wherein the transmission constitutes at least part of support means for the float.

7. Apparatus as claimed in claims 2, 3, 4 or 5 wherein the transmission is separate from support means for the float.

8. Apparatus as claimed in any of claims 2 to 7 wherein the transmission is an upwardly extending rod or a mounting boom or an array of levers.

9. Apparatus as claimed in any of claims 2 to 7 wherein the transmission is a tensioned cable connecting the float to other means.

10 Apparatus as claimed in claim 9 wherein the other means is said generator or part of a power collector serving several floats and itself connected to a generator.

11. Apparatus as claimed in any preceding claim, wherein the float has two major, generally upright surfaces, an inside surface, and an outside surface which faces the waves, the outside surface being concave.

12. Apparatus as claimed in claim ill wherein an upper part of the outside surface is further forward than a lower part.

13. Apparatus as claimed in any preceding claim, wherein the float rear face and mounting means for the float are co-designed to constrain the rear surface to exend parallel to the direction of movement of the float, so as to have as little interaction with the (theoretically calm) water behind the float.

14. Apparatus as claimed in claim 13 wherein the float is mounted to move substantially vertically and the rear face is flat.

15. Apparatus as claimed in claim 13 wherein the float is mounted to pivot about an axis and the rear surface is cylindrical about that axis.

16. Apparatus as claimed in any of claims 1 to 15 and mounted to be disposed "up-wave" from a supporting structure the apparatus being supported by an array of struts and tensioned cables, transmission of energy occurring by means of a cable.

17. Apparatus as claimed in any of claims 1 to 15 and mounted "free" in relatively deep water.

18 Apparatus as claimed in claim 17 wherein there is a guyed mast and cable suspension system, the float performing substantially vertical movement.

19. Apparatus as claimed in claim 17 whrein the apparatus is mounted on structure providing a wave-reflecting sea-wall effect and the float is generally vertically moving, and has concave front and rear surfaces to act, in effect, in both directions.

20. Apparatus as claimed in claim 19 and positioned a distance W/2 from the reflecting wall, wherein W is the wavelength of the waves.

21. Wave energy apparatus as claimed in any preceding claim wherein the float is hollow and made fron concrete.

22. Wave energy apparatus substantially as hereinbefore described with reference to the accompanying drawings.