GB2388873A

GB2388873A - Tidal power generator with hydraulic cylinders

Info

Publication number: GB2388873A
Application number: GB0212009A
Authority: GB
Inventors: Ronald Gordon Mackay
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-24
Filing date: 2002-05-24
Publication date: 2003-11-26
Also published as: GB0212009D0

Abstract

A tidal power generator comprises at least one hydraulic cylinder 107 and a buoyant member 104 to which one member of the hydraulic cylinder 107 is attached. The buoyant member 104 is constrained to move vertically in response to tidal motion, allowing the a first member of the hydraulic cylinder to move relative to a second member of the hydraulic cylinder. This relative motion causes a working fluid to pass between the hydraulic cylinder and a reservoir, and a prime mover is operated by the fluid. The cylinders may be mounted on a platform which may form the buoyant member, or the buoyant member may lie below the platform 109. There may also be an hydraulic pressure accumulator for providing pressurised fluid when tidal motion is minimal and the prime mover may be an hydraulic motor 111 for driving an electrical generator 112.

Description

1 2388873

TIDAL POWER GENERATOR

The present invention relates to tidal power generators, that is to say, power generators which utilise the rise and fall of tidal waters as the source 5 of their input energy, and more specifically, to such generators for producing electricity. Tidal power generators have been known at least since medieval times when they took the form of water wheels positioned in apertures in lo impounding walls built in estuaries or the tidal reaches of rivers. More recently, low pressure turbines have been used similarly, or anchored to the sea or river bed, to generate electricity. However, a disadvantage of such systems is that the energy density of tidal streams is relatively low so that the installations have to be large. Also, sea water is very corrosive so that 5 the protection of rotor surfaces and bearings is a problem.

It is an object of the present invention to provide an improved tidal power generator. to Hydraulic cylinders consist of a first component comprising an operating cylinder within which there is a piston and a second component comprising a ram or rod which is connected to the piston and moves therewith in response to the admission to, or withdrawal from, the operating cylinder of an incompressible fluid. Such hydraulic cylinders are referred to as single 25 acting if the hydraulic fluid has access to one side of the piston only and as double-acting if the hydraulic fluid has access to both sides of the piston alternately.

( According to the present invention, there is provided a tidal power generator comprising at least one hydraulic cylinder as above described, a massive but buoyant member to which one member of the hydraulic cylinder is attached, means for constraining the buoyant member to move vertically in response s to tidal action thereby to cause the first member of the hydraulic cylinder to move relative to the second member of the hydraulic cylinder, a reservoir for a working fluid, means for permitting the passage of the working fluid between the reservoir and the hydraulic cylinder in response to the relative motion between the two components of the hydraulic cylinder, and a prime lo mover adapted to be operated by the working fluid.

Preferably, the buoyant member is constrained to move vertically upon risers in the form of piles driven into the bed of the sea, estuary or tidal portion of a river, as appropriate and the operating cylinder or cylinders 5 is/are attached to a fixed working platform positioned above the buoyant member. Preferably also, the working platform is capable of supporting buildings housing the reservoir for the working fluid, the prime mover, apparatus operated by the prime mover and any ancillary equipment.

20 Preferably, the prime mover is an hydraulic motor and the apparatus operated by the prime mover is an electrical generator.

Alternatively, the working platform can be adapted to act as the buoyant member, the second member of the hydraulic cylinders being fixed in 25 relation to risers upon which the working platform is free to move.

Preferably, the reservoir for the working fluid is adapted to act as a pressure accumulator so as to provide motive power to the hydraulic motor

during those periods of the tidal cycle when the rate of change of the height of tide is at a minimum.

The invention will now be described, by way of example, with reference to 5 the accompanying drawings, in which: Figure is a diagrammatic representation of a first embodiment of the invention, and lo Figure 2 is a diagrammatic representation of a second embodiment of the invention. Referring to Figure 1, a system for the generation of electricity by tidal action includes a number of parallel columns 101 which are fixed to the bed 102 of an estuary or region of water subject to tidal action. The columns 101 can be attached to a heavy concrete base 103 as shown, or driven directly into the bed 102 of the estuary or other region of water which is subject to tidal action. A massive but buoyant flotation chamber 104 is so arranged that it can move freely along the columns 101 in response to tidal action in 20 the estuary or other region of water which is subject to tidal action.

Attached to the upper surface 105 of the flotation chamber 104 are the rams 106 of a plurality of double-acting hydraulic cylinders 107 which are attached to the upper surface 108 of a fixed working platform 109 positioned above the flotation chamber 104. In practice, the columns 101 can form part 25 of a supporting structure for the working platform 109. The hydraulic cylinders 107 are contained within a structure 110 constructed upon the working platform 109. The hydraulic cylinders 107 are connected to a manifold system 110 and thence to an hydraulic motor 111 arranged to drive an electric generator 112. The manifold system 110 includes change

( over valves 113 so that the direction of rotation of the hydraulic motor 111 remains the same when the direction of flow of hydraulic fluid from and to the hydraulic cylinders 107 reverses with the changes of tide.

5 The same effect can be achieved in other ways. For example, the hydraulic cylinders, 107 can all be connected to a common manifold which in turn is connected to the hydraulic motor 111 via unidirectional valves, so that whatever the direction of flow of the hydraulic fluid in the pipework connecting the hydraulic cylinders 107 to the manifold, the direction of fluid 0 flow between the manifold and the hydraulic motor 111 remains the same.

In order to compensate for the variations in the rate of rise and fall of the tide during each tidal cycle, at least one of the hydraulic cylinders 107 is connected to a reservoir 114 which is arranged to act as an hydraulic 5 pressure accumulator. During the periods of lower rate of change of tidal height, say an hour and a half either side of high or low water, hydraulic fluid is released from the reservoir 114 at a rate and pressure sufficient to maintain the speed of the hydraulic motor 111 and hence the output from the generator 112. Ancillary voltage and electrical power distribution 20 equipment which do not form a part of the present invention per se, are not illustrated in the drawing.

Figure 2 illustrates a second embodiment of the invention in which the working platform is adapted to float and move with tidal action and acts as 25 the buoyant member. Those components of the second embodiment of the invention which correspond to similar components of the first embodiment of the invention have the same reference numerals. Referring to Figure 2, the working platform 109 is adapted to float and move vertically along risers 201 in response to tidal action. The rams 106 of the hydraulic

s ( cylinders 107 are attached to a permanently submerged member 202 fixed between adjacent risers 201 below the lowest possible limit of vertical movement of the platform 109. The remainder of the equipment is the same as for the first embodiment of the invention and therefore is not described 5 again.

The present invention has a number of advantages. Firstly, unlike wave-

powered generating systems, the equipment does not have to be positioned where wave-action is large and continuous, that is to say, where weather lo conditions are harsh. Secondly, again unlike wave-powered systems, the power-generating equipment is, effectively, on-shore, which simplifies both the generation of electrical power and its transmission. Thirdly, because the energy input is derived from the buoyancy of the flotation chamber or working platform in the case of the second embodiment of the invention, it i5 is not weather dependent and fourthly, the system is modular and the number of generator sets can be chosen to suit the local circumstances.

Claims

( CLAIMS

1. A tidal power generator comprising at least one hydraulic cylinder as above described, a massive but buoyant member to which one member of the hydraulic cylinder is attached' means for constraining the buoyant member to move vertically in response to tidal action thereby to cause the first member of the hydraulic cylinder to move relative to the second member of the hydraulic cylinder, a reservoir for a working fluid, means for permitting the passage of the working fluid between the reservoir and the hydraulic cylinder in response to the relative motion between the two components of the hydraulic cylinder, and a prime mover adapted to be operated by the working fluid.

2. A tidal power generator according to Claim I wherein there is included a

working platform upon which the operating cylinder or cylinders of the tidal power generator are mounted.

3. A tidal power generator according to Claim 2 wherein the buoyant member is situated beneath the working platform and the rams of the hydraulic cylinder or cylinders are attached thereto.

4. A tidal power generator according to Claim 2 wherein the working platform constitutes the buoyant member and is constrained to move vertically upon risers attached to the bed of the sea, estuary or tidal section of a river and the rams of the hydraulic cylinders are attached to a fixed member positioned below the lowest position reached by the working platform in response to tidal section.

(

5. A tidal power generator according to any preceding Claim wherein the reservoir is adapted to act as an hydraulic pressure accumulator and there is provided means for releasing working fluid from the reservoir to the prime mover during those periods in a tidal cycle when the rate of change of the height of tide is least thereby to stabilise the action of the prime mover during a tidal cycle.

6. A tidal power generator according to any preceding Claim wherein the prime mover is an hydraulic motor forming part of an electricity generating set.

7. A tidal power generator substantially as hereinbefore described and with reference to the accompanying drawings.