GB2488185A

GB2488185A - Free floating bellows wave energy converter

Info

Publication number: GB2488185A
Application number: GB1107631.2A
Authority: GB
Inventors: Francis James Macdonald Farley
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-02-21
Filing date: 2011-05-09
Publication date: 2012-08-22
Anticipated expiration: 2031-05-09
Also published as: GB2488185B; GB201107631D0; GB201102910D0

Abstract

A wave energy converter comprising two or more interconnected airtight vessels filled with gas; a main vessel 1 has flexible walls and ballast 5 so as to float freely in the sea without other support and auxiliary vessel(s) 10, the interconnections 8 include one or more turbines 12 driven by the gas flowing between the vessels. In a first aspect the auxiliary vessels are located above sea level, whereas in a second aspect the auxiliary vessels have rigid walls. The main vessel is preferably in the form of a V-shaped vertical wedge, broad at the top narrow at the bottom, with two wide faces 2 with rigid cover plates which are closed at the top and ends by flexible airtight fabric. The waves cause the main vessel to heave, with the effect that it is alternately compressed and expanded and gas is pumped to and fro between the vessels driving the turbine(s).

Description

FREE FLOATING BELLOWS WAVE ENERGY CONVERTER

According to this invention the free floating bellows wave energy converter comprises two or more closed airtight vessels connected by one or more connection means and filled with air or gas under pressure. Said vessels comprise a main vessel and one or more auxiliary vessels.

The main vessel having flexible walls is compressible and is ballasted to float partially submerged in the sea. With advantage said main vessel is generally in the shape of a vertical wedge, narrow at the bottom, broad at the top and of any width. The pressure changes in the sea due to the waves alternately compress and expand said main vessel.

Each auxiliary vessel is of fixed volume, is not compressible and is not affected by the waves, either because it is located above sea level or because it is protected from the waves by rigid walls. As the waves compress and expand the main vessel the contained gas is pumped to and fro through the connection means into and out of the auxiliary vessel with the effect that the energy in the waves is converted into pneumatic energy of gas flowing through the connection means.

The connection means is furnished with energy conversion means which transforms said pneumatic energy into useful power, such as electric or hydraulic power. The connection means may comprise a plurality of tubes of any length or shape and may comprise flow control means to direct and modulate the flow through each tube. With advantage said energy conversion means comprise one or more air turbines, which may be reversible flow turbines commonly called Wells turbines, or may be unidirectional flow turbines according to the art with the flow being directed by said flow control means. The connection means may be flexible with the effect that the main vessel can heave independently of the position of the auxiliary vessel or vessels.

Said flow control means may comprise any apparatus such as flaps, gates, doors or valves which allow flow in one direction and not the other; or which can be opened and shut by remote control.

The main vessel is ballasted and floats freely in the sea: apart from mooring lines it is not attached to or supported by any other structure. The upward thrust due to the volume of water displaced by said main vessel balances the downward force due to the mass of the structure plus ballast. If said vessel is moved downwards, it is compressed by the higher water pressure outside, so its buoyancy is reduced with the effect that it tends to sink further than a rigid body of the same initial shape, and the downward movement is amplified. This effect is limited by the increasing pressure of the compressed gas inside the system. As a result the vertical stability of the system is influenced by the volume of gas contained in the main and auxiliary vessels and connecting means. By correctly choosing the volumes of the main and auxiliary vessels the resonant heave period of the main vessel can be adjusted. According to the invention said resonant heave period is close to the period of the waves prevailing in the sea with the effect that said main vessel heaves with enhanced amplitude and more power is captured from the waves.

The auxiliary vessel may comprise a plurality of separate vessels interconnected by flow control means with the effect that the volume of gas in communication with the main vessel can be varied and accordingly the resonant heave period of the main vessel can be changed from time to time to match the prevailing wave period.

The cross section of the main vessel may with advantage be in the form of a V-shaped vertical wedge, broad at the top and tapering to a narrow keel, with two wide faces of any width. The ballast is attached to the keel. The faces of said vessel may comprise rigid cover plates of any shape reinforced according to the art, flexibly connected or hinged at the bottom, the vessel being closed at the top and ends by arcs of flexible material such as polymer-coated fabric, with the effect that the V can open and shut under the action of the waves and the contained volume is changed with the effects described above. Alternatively the faces of said main vessel may comprise flexible material such as polymer-coated fabric. In this case said material may with advantage be stiffened by a multiplicity of rigid rods, tubes or battens of any shape oriented in any direction in order to maintain an optimum shape for the vessel.

A specific embodiment of the invention will now be described by way of example without limitation with reference to the accompanying drawing in which: Figure 1 shows a side view of the free floating bellows wave energy converter together with the vertical transverse section AA Figure 1 shows an embodiment of the invention in vertical lateral view and in vertical transverse cross section AA. The wave energy converter comprises a main vessel 1 and an auxiliary vessel 10. The more or less rectangular side faces 2 of the main vessel may comprise rigid cover plates of any material or may comprise flexible airtight sheet for example without limitation polymer-coated fabric stiffened by a multiplicity of rigid rods, tubes or battens 3 (shown with dotted lines in the figure) oriented in any direction. The side faces 2 may be of any width. The faces of said vessel are flexibly connected at their lower edge 4. Ballast 5 is attached to said faces at their lower edge. Mooring lines 6 are attached wherever convenient. Said main vessel is closed at the top and ends with panels of flexible airtight sheet 9 for example without limitation polymer-coated fabric. Said main vessel is inflated with air or other gas under pressure. Said main vessel floats in the sea as illustrated, the approximate position of the sea surface being indicated by the wavy lines 7. Said main vessel is furnished at any convenient position with one or more connection means 8 (only one is shown in the figure) communicating with the auxiliary vessel 10, which is inflated with the same gas at the same pressure.

With advantage said auxiliary vessel is cylindrical with hemispherical ends with its axis lying in any direction. In this embodiment, as illustrated in the Figure 1, the auxiliary vessel 10 is attached to and supported by the main vessel 1 above the water line by support means 11 according to the art, with its axis parallel to the faces of the main vessel. In an alternative embodiment said axis is perpendicular to the faces of the main vessel with the effect that the auxiliary vessel floats on the sea surface at the side of the main vessel. The walls of said auxiliary vessel can be made of any material but may with advantage comprise flexible airtight sheet for example without limitation polymer-coated fabric. Said auxiliary vessel is located above the surface of the sea so that it is not exposed to the pressure of the waves. Alternatively said auxiliary vessel may be attached to said main vessel below the water line but in this case its walls must be rigid so that it is not exposed to the varying pressure of the waves.

The combined structure comprising the main vessel 1 and the auxiliary vessel 10 is not attached to any other body: it floats freely in the sea and can oscillate vertically in heave. As it does so, the varying external pressure of the sea exerted on the faces 2 of the main vessel causes said vessel to contract and expand, driving the contained gas via the connection means or tubes 8 into and out of the auxiliary vessel 10. The wave energy is thus converted into pneumatic energy flowing to and fro inside said connection means. As illustrated in Figure 1 the connection means is a tube 8 furnished with an air turbine 12, which may be a reversing flow turbine commonly called a Wells turbine, with the effect that the flow of gas to and fro between the vessels generates useful electric or hydraulic power. With advantage two or more connecting tubes are provided, with flow control means so that the flow in each tube is intermittent but unidirectional, each tube being furnished with a unidirectional air turbine according to the art.

The main vessel may be provided with a plurality of connection means furnished with a plurality of turbines communicating with one or more auxiliary vessels with flow control means for opening or closing said connections.

With advantage one or more intermediate vessels may be connected between the main vessel and the auxiliary vessel or vessels with flow control means with the effect that gas is temporarily stored in the intermediate vessel or vessels and the flow through the turbine(s) is smoothed.

In operation the device is moored with the side faces 2 oriented in any direction relative to the incident wave fronts. The action of the waves causes the device to heave and the side faces 2 to move towards and away from each other, pumping the contained gas to and fro from one vessel to the other through the connection means with the effect that the turbine or turbines generate useful power.

Claims

SCLAIMS1) A wave energy converter comprising two or more airtight vessels interconnected by connection means and filled with air or gas under pressure, a main vessel having flexible walls and ballasted to float freely in the sea without other support, with auxiliary vessels being located above sea level, the connection means being furnished with energy conversion means driven by the gas flowing between the vessels.
2) A wave energy converter comprising two or more airtight vessels interconnected by connection means and filled with air or gas under pressure, a main vessel having flexible walls and ballasted to float freely in the sea without other support, with auxiliary vessels having rigid walls, the connection means being furnished with energy conversion means driven by the gas flowing between the vessels.
3) A wave energy converter as claimed in claims 1 or 2 in which the main vessel is generally in the shape of a vertical wedge, narrow at the bottom, broad at the top and of any width.
4) A wave energy converter as claimed in claims 1, 2 or 3 in which the sides of the main vessel comprise rigid cover plates of any shape flexibly connected at the bottom said main vessel being closed at the top and ends by airtight flexible sheet.
5) A wave energy converter as claimed in claims 1, 2 or 3 in which the main vessel is made of airtight flexible sheet.
6) A wave energy converter as claimed in claims 1, 2 or 3 in which the main vessel is made of airtight flexible sheet reinforced by a multiplicity of rigid rods, tubes or battens oriented in any direction.
7) A wave energy converter as claimed in any of claims 1 to 6 in which said auxiliary vessel or vessels are made of airtight flexible sheet.
8) A wave energy converter as claimed in any of claims 1 to 7 in which said auxiliary vessel or vessels are attached to and supported by said main vessel and oriented in any direction.
9) A wave energy converter as claimed in any of claims 1 to 8 in which said energy conversion means is one or more air turbines driving electric generators or hydraulic pumps.
10) A wave energy converter as claimed in any of claims 1 to 9 in which flow control means are provided to switch the flow between a plurality of connection means.
11) A wave energy converter as claimed in any of claims 1 to 10 in which one or more intermediate vessels are connected between the main and auxiliary vessels with flow control means with the effect that the flow through the turbine(s) is smoothed.
12) A wave energy converter generally as described in the text and illustrated in the drawings and used to extract useful power from the sea.