GB2081816A

GB2081816A - Wave energy conversion apparatus

Info

Publication number: GB2081816A
Application number: GB8123719A
Authority: GB
Original assignee: Sea Energy Associates Ltd
Current assignee: Sea Energy Associates Ltd
Priority date: 1980-08-02
Filing date: 1981-08-03
Publication date: 1982-02-24

Abstract

The device comprises a reaction member 29 buoyantly supportable and having at one side means defining a pumping chamber 26 which is at least partially defined by a flexible membrane so that the chamber is compressed and expanded under the influence of waves to effect pumping of fluid, e.g. air, for driving a prime mover, e.g. a turbine 27. A number of pumping chambers may be provided. A pivoted flap 12 may cooperate with the membrane as shown. Alternatively, the flap may be omitted and the membrane may define a pumping chamber (14A), Figs. 7 & 8 (not shown), or a pair of membranes may define juxtaposed high and low pressure pumping chambers (17, 13), Figs. 9 & 10 (not shown). <IMAGE>

Description

SPECIFICATION Improvements relating to energy conversion devices This invention relates to energy conversion devices and has reference to devices by which the energy in the waves in a body of water (usually the sea) is converted by the device into a more readily usable form, such as electrical energy.

We have already made a number of applications for patents for inventions relating to such devices, and in one specific application No.

06512/79 we have described an apparatus in which energy conversion is achieved by displacing a fluid from an enclosed chamber or cavity by having the cavity arranged so that the waves in the body of liquid displace a wall of said cavity to reduce its volume. The displaced fluid is used to drive a turbine or the like, which in turn drives an electrical generator.

The present invention is concerned with the design of said cavity, which requires to be defined at least partially by means of a flexible membrane.

As that membrane must flex during the cyclic operation of the device, then its design is important if it is to withstand the repeated flexings to which it will in use be subjected.

We have already outlined the problems of membrane design in connection with energy conversion devices in our copending application No. 8010534 and the present invention is concerned with designs of membrane (or flexible bag) construction.

Basically, the application according to the invention can be considered as comprising a reaction or support member which takes the main thrust and heave forces of the waves, and the wave forces on the wall cavity are supported by the reaction or support member so that the cavity is squeezed by the waves onto the support or reaction member, fluid, for example air, which is most favoured, being displaced from the cavity through a suitable outlet and over a turbine or like device which is driven by the displaced fluid, and which in turn drives an electrical generator.

A number of embodiments are illustrated in the accompanying diagrammatic drawings and such embodiments are now described.

Referring to Fig. 1 and Fig. 2, which show respectively a side and end elevation of a portion of an apparatus for converting wave energy, in these drawings a spine is indicated by the numeral 10, the spine being a support or reaction structure.

The spine is buoyantly supported in the water of which the level is indicated by the letter L, and attached to a lower edge of the spine 10, which is rectangular in cross section, so as to be pivotably relative thereto is a flap 12. Between the flap 12 and the spine 10 is a flexible bag or membrane 14.

As the flap 12 comes under the influence of the waves in the water, so it will oscillate as indicated by the doubie arrow 16, thereby to cause the membrane 14 to act as a bellows pump, to pump air through an appropriate outlet aperture and into the spine 10. The pump air is utilised as described herein to rotate a prime mover to create electrical power.

It will be understood that the membrane or bag 14 is subjected to repeated fiexings, and the bag design is of significance if bag failure is not to be encountered prematurely. The bag is most likely to fail in the region of the corners 20 as it is difficult to make a part spherical shape fold to flap form without creasing occuring.

In the arrangement shown in Figs. 3 and 4, again the spine is indicated by numeral 10, and the plate by numeral 12. In this case, the plate is smaller and is of a slightly different configuration, and the membrane or bag 14 is connected only to the periphery of the plate 12 and thereby a minimum amount of flexible membrane is used, thereby reducing the potential risk of premature failure. The other reference numerals are used to indicate parts corresponding to the parts already described in relation to Figs. 1 and 2.

In the arrangement shown in Figs. 5 and 6, the construction is essentially the same as that illustrated in Figs. 1 and 2, except that internal compression springing 22 acting between the plate 12 and the spine 10 is utilised, in order to return the plate 12, and to limit the degree of flexing of the membrane 1 4.

With regard to the arrangement disclosed in Figs. 7 and 8, in this case no plate 12 is provided, but the bag ends are shaped, as shown in Fig. 7, so that at the lower portion of the bag, the ends are closer together and then they curve outwardly as shown clearly in Fig. 7. As shown in Fig. 8, no plate 12 is provided, and the front face of the bag forms the surface which is contacted by the waves. In Fig. 8, it is also shown that the face which contacts the waves curves from the bottom edge of the spine outwardly to define a top lobe portion 1 4A. This is due to the fact that the pressure on the membrane by the surrounding water is greater in proportion to the depth of the membrane under the surface L.

In all of the arrangementsdescribed thus far, it will be normal to prime the interior of the membrane with fluid under pressure, normally compressed air, so that the displacement of the active face of the means defining the cavity will be against a back pressure, and also so that the extent of flexing of the membrane will be limited or restricted.

In the arrangement shown in Figs. 9 and 10, a double bag construction, each being substantially of the configuration shown in Fig. 8, is used, and two membranes 14 and 1 5 are provided, the membrane 1 5 defining a high pressure cavity 17.

whilst the membrane 14 defines a low pressure cavity 1 3. By appropriately pressurising the cavities 17 and 13 with air or other fluid under respectiveiy high and low pressure, so the active face of the combined membranes can be of the form shown in Fig. 10, thereby ensuring the satisfactory positioning of the membrane 14 to make it suitable for deflection by the wave forces for best results. Again, in Figs. 9 and 10, there is no front plate, such as the plate 12 in the Figs. 1 to 6 embodiments.

In the arrangement shown in Figs. 11 and 12, the membrane 14 may be continuous throughout the length of the spine 10, and it may contain therein spaced high pressure pockets 24 which can be charged with air or other fluid under high pressure, in order to define individual low pressure working cavities 26 which form the pumping zones. The low pressure cavities may be associated with plates 1 2 for the deflection of the membrane 14 between each pair of high pressure.

separating cavities 24. Fig. 12 also shows a prime mover in the form of a uni-directional turbine 25 in a passage 27 which communicates with the shown cavity 26.

This is a turbine 25 and passage 27 for each cavity 26 and the passages lead to a common manifold 29. This arrangement can be used in each embodiment described herein.

In the arrangement shown in Figs. 13 and 14, the membrane 14 between the plate 12 and spine 10 is of the shape shown in Fig. 1, but in addition, within the bag there are defined conical end pockets 30 which are sealed, but contain at the lower and a quantity of liquid 32 to act as a pressure balancing means as regards the external pressure applied from the surrounding water on the plate 12. These sealed cavities 30 and the liquid contained therein provide a means for supporting the ends of the bag, and ensure that the bag deflects in an advantageous fashion in operation, minimizing or preventing failure as a result of flexing.

In the arrangment shown in Figs. 1 5, 1 6 and 1 7, the spine is made up of the cylindrical portion 10A, to the bottom side of which is a rectangular portion 1 OB, and a plurality of bags 14 are mounted on one side of the spine as shown, each in register with an air port 40 which can be covered by a deflectable sealing plate 42 depending upon the conditions inside the associated bag. The bag is adapted to be attached along the rim 44, so as to cover the sealing plate 42 and port 40 and be in register therewith as indicated in Fig. 1 6, but the bottom of the bag is open to the surrounding liquid L, so that the liquid will partially fill the cavity 1 7 defined by the bag 14. The level of liquid inside the bag 14 will be lower than the level of liquid L due to the fact that the interior of the bag 14 will be pressurised with air under pressure. During normal operation the bag 14 will deflect in the normal manner, and air will be displaced past the plate 42 and out of port 40, but should the level of liquid inside the bag 14 reach a pre-determined height, and contact a significant portion of the plate 40, the plate 40 will be urged by the water pressure against the port 42 in order to close same, and prevent any further discharge of fluid from cavity 17, and also the ingress of water through the port 40.

Claims

1. Apparatus for the converstion into a more readily usable form of the energy in waves in a body of liquid comprising a reaction member, means defining a pumping cavity to one side of the reaction member, said means being at least partially defined by a flexible membrane, so that under the influence of the waves compressing and relaxing of the pumping chamber cyclically takes place and displacement and induction of fluid from and into the chamber takes place, use being made of the fluid movement to drive a prime mover.

2. Apparatus according to claim 1 , wherein said means defines a plurality of said chambers.

3. Apparatus according to claim 2, wherein each chamber is defined by a flexible bag located between a pivotable rigid flap which faces the waves, and the reaction member.

4. Apparatus according to claim 3, wherein there is a spring means in each cavity which resists the pivoting of the flap towards the reaction member.

5. Apparatus according to claim 2, wherein each chamber is defined by a pivotable rigid flap which faces the waves, and a flexible membrane connecting the edge of the flap and the reaction member.

6. Apparatus according to claim 2, wherein each cavity is defined by a flexible bag of generally rectangular shape of which the ends are curved so that the bag will be shorter at the bottom than at the top.

7. Apparatus according to claim 2, wherein each cavity is defined by a flexible bag under which there is a second flexible bag which can be pressurised to a higher degree than the first mentioned flexible bag.

8. Apparatus according to claim 2, wherein a flexible membrane extends along the reaction member, and at spaced intervals are high pressure bags, the membrane between adjacent bags and the bags defining one of said cavities.

9. Apparatus according to claim 2, wherein each cavity is defined by a flexible bag at each of a pair of ends of which there is a sealed sub cavity containing a quantity of liquid.

10. Apparatus according to claim 2, wherein each cavity is defined by a flexible bag which is open to the body of water at the underside, and there is a valve flap adapted to cover a port through which the fluid is normally pumped in the event that the level of the body of liquid rises in the cavity to act on the valve flap.

11. Apparatus for the conversion into a more readily usable form of the energy in waves in a body of liquid, substantially as any of the embodiments hereinbefore described.