GB2060082A

GB2060082A - Improvements in or relating to Wave Energy Devices

Info

Publication number: GB2060082A
Application number: GB8031399A
Authority: GB
Original assignee: French M J Co Inc
Current assignee: French M J Co Inc
Priority date: 1979-10-03
Filing date: 1980-09-29
Publication date: 1981-04-29
Also published as: GB2060082B

Abstract

A wave energy device 10 has submerged tanks 12, 13, filled with a ballast liquid 16 and upper ducts 25, 26 above the sea level for air pumped into the upper ducts 25, 26 by a flexible wall pump 14, 15 actuated by sea waves. In order to assist in maintenance of the device 10, the submerged tanks 12, 13 can be blown out to alter the trim of the device 10 whereby the device 10 achieves a stable position balanced by the buoyancy provided by the submerged tanks 12, 13 and the upper ducts 25, 26. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Wave Energy Devices This invention relates to devices for extracting energy from waves on a liquid, and more particularly but not exclusively to wave energy devices the subject of co-pending patent application No. 21 768/76. In Claim 1 of the aforesaid co-pending patent application No.

21768/76, a wave energy device for conversion of energy from water waves comprises an enclosure having a flexible wall of impermeable material, the enclosure containing gas, an outgoing gas passageway and a return gas passageway communicating with the enclosure via non-return valves arranged to permit one way gas flow from the enclosure into the outgoing gas passageway and to permit one way gas flow from the return gas passageway into the enclosure, support means to which the material of the flexible wall is attached with the enclosure extending upwards in operation from its attachment to the support means, the device being located for operation in water with the top of the enclosure approximately at or just below the surface, whereby in operation pressure imparted via the flexible wall of the enclosure to the gas within the enclosure by the passage of a water wave crest forces gas into the outgoing gas passageway and, correspondingly, as gas pressure in the enclosure falls with the passage of a water wave trough, gas is returned into the enclosure from the return gas passageway.

A wave energy device may be installed in a marine location for a relatively long period of time. During this period maintenance, whether routine or breakdown, may be necessary at the location, and whilst components of the device above the water level may provide ready access, submerged components may present some difficulties in carrying out such maintenance.

According to the present invention, there is provided a device for extracting energy from waves on a liquid and comprising duct means for containing a working fluid and extending along the device, ballast tank means extending along the device in spaced relationship with the duct means and adapted to contain a ballast liquid, port means for the passage of said ballast liquid into and out of said ballast tanks means, pumping means located between the duct means and the ballast tank means, the pumping means being responsive to the pressure of the waves on the device so as to pump the fluid into the duct means, and inlet port means and outlet port means each connecting the pumping means to the duct means, the disposition of the duct means and of the ballast tank means in the device being such that in operation of the device with the ballast tank means containing the ballast liquid, the ballast tank means is below the duct means, and evacuation of the ballast tank means changes the trim of the device in the liquid so as to raise a submerged portion of the device above the liquid level.

In the preferred form of the invention the duct means is positioned such as to be above the liquid in operation of the device but such as to act as a buoyancy chamber means of the device in the changed trim position of the device, and desirably comprises two ducts extending in side adjacent relationship and connectable together through a means for performing useful work from the working fluid of the duct means.

The ballast tank means may comprise two ducts extending in side adjacent relationship, each said duct having a plurality of transverse divisions so as to form each said duct into a plurality of ballast tanks.

The pumping means may comprise a pumping chamber having at least a part of the wall thereof of a flexible material impermeable to said working fluid, the flexible material being arranged to be exposed to the waves so as to change the volume of the pumping chamber from the deflection of said flexible material in response to the waves, for example as described in co-pending application No.21768/76.

Alternatively, the pumping means may include at least one movable member of rigid form arranged to be exposed to the waves so as to actuate the pumping means from movement of said movable member in response to waves, for example as described in co-pending application No. 8011 823 to which reference is directed.

The invention will now be further described by way of example only with reference to the accompanying drawings in which: Figure 1 shows a diagrammatic cross-sectional representation of a wave energy device; Figure 2 shows a reduced scale a diagrammatic view on the line Il-Il of Figure 1; and Figure 3 shows the device of Figure 1 but at an alternative trim.

Referring now to Figures 1 and 2, a wave energy device 10 is shown floating in a liquid 1 6 (e.g. the sea), and comprises an elongate structure 11 having a left-hand ballast tank means 12 and a right hand ballast tank means 13 each being of triangular cross-section and extending along the lower portion of the device 10 in side adjacent relationship and being provided by a plurality of individual tanks 1 2a or 1 3a respectively each filled with the liquid 1 6.

Above the ballast tank means 12, 13, a plurality of left hand pumping chambers 14 and of right hand pumping chambers 15 in side adjacent relationship extend along the structure 11, each pumping chamber 14, 15 being air filled and defined at least in part by a relatively thick flexible wall 20 of a plastics coated cloth or similar flexible impermeable material, and separated from each other by relatively thin respective divisions 21 of the same flexible impermeable material as the flexible wall 20.A high pressure duct 25 and a low pressure duct 26 in side adjacent relationship extend along the device 10 above the pumping chambers 14, 15, each pumping chamber 14, 15, having an outlet port 27 connected to the high pressure duct25 and an inlet port 28 connected to the low pressure duct 26.

A housing 30 above the high pressure duct 25 and the low pressure duct 26 contains a turbogenerator 31 having an inlet duct 33 connected to the high pressure duct 25 and an outlet duct 34 connected to the low pressure duct 26.

A buoyancy chamber 36 is provided at each end of the structure 11, and each ballast tank 12a, 13a is capable of being evacuated in a conventional manner, e.g. discharged by compressed air through a port (not shown), to change the buoyancy and thus the trim of the device 10 in the sea. The compressed air may be supplied from a maintenance vessel or from the device 10 itself.

The device 10 in use is aligned parallel to the direction of incoming waves so that waves pass along the device as shown by the line 38 of Figure 2. Thus the flexible wall 20 of each pumping chamber 14, 1 5 is subjected to compression as a wave crest rises about it, so that air is discharged from the respective pumping chamber 14 or 15 through the respective outlet port 27 into the high pressure duct 25 as the flexible wall 20 progressively collapses under the compressive load applied by the wave crests as shown by the broken lines 20a-20c. Air in the high pressure duct 25 flows through the inlet duct 33 to the turbo-generator 31 to perform useful work, and from the turbo-generator 31 flows through the outlet duct 34 to the low pressure duct 26.As the wave crest passes so that the level of the liquid 1 6 falls about each flexible wall 20, air from the low pressure duct 26 discharges through the respective inlet port 28 into the respective pumping chamber 14 or 15 and thus expands the pumping chamber 14 or 15 and moves its flexible wall 20 outwardly.

This sequence of the progressive collapse and subsequent outward movement of the flexible walls 20 with the associated discharge and expansion of the pumping chambers 14 and 1 5 continues as wave crests move along the device 10, and the electrical output produced by the turbo-generator 31 represents energy extracted from the waves.

When maintenance needs to be carried out on parts of the device that are usually below the level of the liquid 16, the ballast tank(s) 12a and/or 1 3a may be evacuated to provide an additional buoyancy component to alter the trim of the device 10 and cause it to capsize, for example, as shown in Figure 3, to a stable position balanced by the buoyancy provided by the ballast tank(s) 1 2a and/or 1 3a and the low pressure duct 26, so that the flexible walls 20 on one side of the device 10 are exposed above the liquid 16 and can be removed for replacement or for access into the pumping chambers 14. Once maintenance on the exposed side of the device 10 has been completed, the ballast tank(s) 1 2a and/or 13a, can be refilled with water to restore the device 10 to its operating position. Naturally, the other side of the device can be exposed for maintenance in a similar manner.

Although the invention has been described in relation to a wave energy device having pumping chambers defined in part by flexible walls which are exposed to the waves, the invention may be incorporated in alternative wave energy devices, for example devices in which movable members of rigid form are exposed to the waves so as to actuate a pumping device, an example of such a device being described in co-pending patent application No. 8011823 to which reference can be made.

Claims

1. A device for extracting energy from waves on a liquid and comprising, duct means for containing a working fluid and extending along the device, ballast tank means extending along the device in spaced relationship with the duct means and adapted to contain a ballast liquid, port means for the passage of said ballast liquid into and out of said ballast tank means, pumping means located between the duct means and the ballast tank means, the pumping means being responsive to the pressure of the waves on the device so as to pump the fluid into the duct means, and inlet port means and outlet port means each connecting the pumping means to the duct means, the disposition of the duct means and of the ballast tank means in the device being such that in operation of the device with the ballast tank means containing the ballast liquid, the ballast tank means is below the duct means, and evacuation of the ballast tank means changes the trim of the device in the liquid so as to raise a submerged portion of the device above the liquid level.

2. A device as claimed in Claim 1 , wherein the duct means is positioned such as to be above the liquid in operation of the device but such as to act as a buoyancy chamber means of the device in the changed trim position of the device.

3. A device as claimed in Claim 1 or Claim 2, wherein the duct means comprises two ducts extending in side adjacent relationship and connectable together through a means for performing useful work from the working fluid of the duct means.

4. A device as claimed in any one of the preceding Claims, wherein the balance tank means comprises two ducts extending in side adjacent relationship, each said duct having a plurality of transverse divisions so as to form said each duct into a plurality of ballast tanks.

5. A device as claimed in any one of the preceding Claims, wherein the pumping means comprises a pumping chamber having at least a part of the wall thereof of a flexible material impermeable to the working fluid, the flexible material being arranged to be exposed to the waves so as to change the volume of the pumping chamber from the deflection of said flexible material in response to the waves.

6. A device as claimed in any one of Claims 1 to 4, wherein the pumping means includes at least one movable member of rigid form arranged to be exposed to the waves so as to actuate the pumping means from movement of said movable member in response to the waves.

7. A device as claimed in any one of the preceding Claims, wherein a compartment for increasing the buoyancy of the device is provided at each end of the device.

8. 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.