GB2129059A

GB2129059A - A wave energy device

Info

Publication number: GB2129059A
Application number: GB08326916A
Authority: GB
Inventors: Michael James Platts; Colin Palmer
Original assignee: ENERGY SECRETARY OF STATE FOR; UK Secretary of State for Energy
Current assignee: ENERGY SECRETARY OF STATE FOR; UK Secretary of State for Energy
Priority date: 1982-10-22
Filing date: 1983-10-07
Publication date: 1984-05-10
Also published as: GB8326916D0

Abstract

In the device a flexible membrane 26 of a pump chamber 22 is exposed to the waves and deflection of the membrane 26 in response to the waves is used to pump a working gas to and from a plenum chamber 20. A fluid-filled bag 42 is disposed along the edges of the pump chamber 22, to add shape to the pump chamber 22, to reduce dead areas therein and to support the membrane 26 so as to inhibit creasing or kinking of the membrane 26 during the compression stroke. The working gas drives a turbine 32 which, in turn, drives a generator 36. <IMAGE>

Description

SPECIFICATION A wave energy device This invention relates to a wave energy device, and in particular to a wave energy device in which the effect of waves on a movable wall of a pump chamber is arranged to vary the volume of the pump chamber to perform useful work by pumping a working gas, the movable wall having at least a part thereof of flexible impermeable material.

Examples of such devices are described in British Patent Specification Nos. 2060082A and 1580805, and one problem common to such devices is that of inhibiting creasing or kinking of the flexible material, and reducing the dead area in the pump chamber during the compression portion of the pumping cycle of the pump chamber.

The invention therefore provides a device for extracting energy from waves on a liquid, and comprises a body arranged to be exposed to waves, and a pumping means at the body responsive to the effect of the waves, the pumping means comprising a pump chamber having at least a part of a movable wall thereof of flexible material impermeable to the liquid, and the movable wall being arranged to be exposed to the waves on one side thereof so as to vary the volume of the pump chamber in response to the waves, there being provided in the pump chamber along at least part of the edge thereof, a flexible support for the movable wall arranged to be internally pressurised by a fluid.

The flexible support may extend along the upper edge and/or the lower edge of the pump chamber and, desirably, also extends along the side edges of the pump chamber Convenientiy, the flexible support locates on an inclined portion of the body. At least one shaped tail portion extending from the flexible support may be adapted to be located in shaped grooves in the body, and the flexible material of the movable wall at least at one edge thereof may be shaped so as to be located in a respective shaped groove in the body.Each tail portion or edge of the flexible material at one side thereof, may be held in the respective shaped groove by complementary wedges having inclined sides thereof adjacent, and the inclined sides may be shaped to defined interengaging surfaces such as to inhibit withdrawal of one or other of the complementary wedges from the shaped groove.

The body preferably defines a plenum chamber for the working gas, and a respective selfrectifying air turbine is desirably connected between each said pump chamber and the plenum chamber, so that discharge of the working gas between the plenum chamber and a said pump chamber is through the respective turbine.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Figure 1 shows a side view of a device for extracting energy from waves; Figure 2 shows to an enlarged scale a view on the line I1--II of Figure 1; and Figure 3 shows to an exaggerated scale that portion of the view of Figure 2 within the circle 'X' of Figure 2.

Referring now to Figure 1, a wave energy device 10 is shown floating in a liquid 12 (e.g. the sea), and comprises an elongate reinforced concrete body 14 having a plurality of pumping means 1 6. As shown in Figure 2, the body 14 is of tubular section so as to define a plenum chamber 20 for a working gas (e.g. air) along the body 14.

Each pumping means 16 comprises a pump chamber 22 defined between a flat side 24 of the body 14 by a relatively thick flexible membrane 26. The membrane 26 is impermeable to the liquid 12 and is joined therearound to the body 14, the membrane 26 comprising rubber or plastics material, reinforced with cloth or cord. A duct 30 extending from the pump chamber 22 to the plenum chamber 20 houses a self-rectifying air turbine 32 connected by a drive shaft 34 to an electric generator 36. An example of a selfrectifying air turbine 32 is that devised by Dr. A. A.

Wells, formerly of The Queens University of Belfast, Northern Ireland, and described in British Patent Specification No. 1595700.

A flexible support at the upper end of the pump chamber 22 for the membrane 26 is provided by a flexible bag 42 inflated by a fluid (e.g. air or water) and is of similar material to that of the membrane 26. The bag 42 sits on a plinth portion 48 of the body 14 and bears against (a small gap is shown for clarity) the inside surface of the membrane 26.

The bag 42 has side portions 50, 52 (see Figure 1) respectively, one at each side of the pump chamber 22, and which reduce in cross-section towards the lower end of the purrip chamber 22.

Two displaced tails 56 project from each bag 42, and, as shown in Figure 3, each tail 56 has a flared end 58 formed by a steel beading 60 set in a rubber fairing 62 in the flared end 58. Each flared end 58 locates in a respective groove 66 in the body 14, the groove 66 having a rounded end 67 to allow the tail 56 to deflect without kinking. The groove 66 is shaped at one side 68 so as to locate the flared end 58, and is straight at the other side to locate complementary plastics (e.g.

nylon) wedges 72a, 72b for trapping the flared end 58 in the groove 66. The wedges 72a, 72b have complementary serrations 74 (shown to an enlarged scale for clarity) along adjacent faces 76a, 76b of the wedges 72a, 72b respectively.

The serrations 74 are of saw-tooth form and aligned so as to resist withdrawal of the wedge 72a from the groove 66. The tails 56 extend for the full length of the bag 42 to hold the bag 42 to the plinth portion 48 and to the flat side 24. In a similar manner to that described in relation to Figure 3, the edges of the membrane 26 are held in the body 14, the membrane 26 replacing the tails 56 in Figure 3. Referring again to Figure 2, at the lower end of the membrane 26, the flat side 24 is rounded at 82 to allow the membrane 26 to deflect without kinking during the compression cycle of the pumping means 1 6, a buttress portion 84 of the body 14 providing additional support for the membrane 26 as it protrudes from the body 14.

In operation, the device 10 is presented broadside to the waves with the membranes 26 facing the waves. Under the effect of a wave at each pump chamber 22, the membrane 26 is displaced through a stroke 'S' (see Figure 2) with the working gas being displaced from the pump chamber 22 through the duct 30, and is pressed (shown in broken line) against the flat side 24 except at the upper end and at the sides of the membrane 26 where it is held away by the bag 42. The bag 42 distorts (as shown in chain broken line) in supporting the membrane 26, but reduces any tendency of the membrane 26 to crease or kink, and also minimises the dead space in the pump chamber 22. On the wave passing the device 10, working gas from the plenum chamber 20 discharges through the duct 30 into the pump chamber 22 to distend the membrane 26.The working gas in passing through the duct 30 in each direction rotates the turbine 32 unidirectionally which drives the electric generator 36 through the drive shaft 34.

Suitable alternative materials may be used in the device 10, for example the wedges 72a, 72b might comprise, polypropylene, or polyvinyl chloride, or might comprise a suitable wood such as teak, and the steel beading 60 might be replaced by a nylon or a polyamide cord.

Although the bag 42 has been described as being free of the membrane 26, if desired the bag 42 might be attached to the membrane 26 or even be integral therewith. Alternative shapes of bags 42 may be used in relation to the pump chamber 22. For example, the bag 42 might extend along the lower end of the pump chamber 22 instead of the upper end, or may extend completely around the pump chamber 22, and to the edge of the duct 30. The shape of the bag 42 can provide important beneficial effects on the pumping performance of the membrane 26.

Although the arrangement of Figure 3 is preferred for attaching the bag 42 and the membrane 26 to the body 14, alternative arrangements may be used. It will also be appreciated that the invention may be incorporated in alternative wave energy devices to that of Figure 1, for example a wave energy device in which the movable wall thereof includes a rigid panel portion, or a device fixed rigidly to the sea bed or forming part of a sea wall.

Claims

1. A device for extracting energy from waves on a liquid, and comprising a body arranged to be exposed to waves, and a pumping means at the body responsive to the effect of the waves, the pumping means comprising a pump chamber having at least a part of a movable wall thereof of flexible material impermeable to the liquid, and the movable wall being arranged to be exposed to the waves on one side thereof so as to vary the volume of the pump chamber in response to the waves, wherein there is provided in the pump chamber along at least part of the edge thereof, a flexible support for the movable wall arranged to be internally pressurised by a fluid.

2. A device as claimed in Claim 1, wherein the flexible support extends along the upper edge and/or the lower edge of the pump chamber.

3. A device as claimed in Claim 1 or Claim 2, wherein the flexible support extends along the side edges of the pump chamber.

4. A device as claimed in any one of the preceding Claims, wherein the body at the pump chamber defines a flat side and an inclined portion thereof, and at least part of the flexible support locates at the inclined portion.

5. A device as claimed in any one of the preceding Claims, wherein at least one shaped tail portion extends from the flexible support and is shaped to be located in a respective shaped groove in the body.

6. A device as claimed in Claim 5, wherein the flexible material of the movable wall at least at one edge thereof is shaped so as to be located in a respective shaped groove.

7. A device as claimed in Claim 5 or Claim 6, wherein each tail portion or edge of the flexible material at one side thereof is arranged to be held in the respective shaped groove by complementary wedges having inclined sides thereof adjacent.

8. A device as claimed in Claim 7, wherein the inclined sides are shaped to define interengaging surfaces such as to inhibit withdrawal of one or other of the complementary wedges from the shaped groove.

9. A device as claimed in Claim 7 or Claim 8, wherein the wedges comprise polypropylene, polyvinyl chloride, or teak.

10. A device as claimed in any one of the preceding Claims, wherein the body defines a plenum chamber for the working gas, and a respective self-rectifying air turbine is connected between each pump chamber and the plenum chamber so as to be driven by flow of the working gas between the pump chamber and the plenum chamber.

11. A device as claimed in any one of the preceding Claims, wherein the flexible support is integral with the movable wall.

12. A device for extracting energy from waves on a liquid, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

13. A device for extracting energy from waves on a liquid, substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.