GB2145166A

GB2145166A - Tidal power method and apparatus

Info

Publication number: GB2145166A
Application number: GB08322221A
Authority: GB
Inventors: In Kyu Choi
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-08-18
Filing date: 1983-08-18
Publication date: 1985-03-20
Also published as: GB2145166B; GB8322221D0

Abstract

Tidal power apparatus includes a buoyancy vessel having a variable-buoyancy chamber 2 and a fixed-buoyancy chamber 3. As the tide rises, the vessel is subsequently released so that it rises and drives a pump 11 through a variable ratio transmission including conically wound gears. Water is pumped from the chamber 2 to a reservoir 18 supplying water to electricity generating means which discharges the water to a reservoir 17. The vessel is held at its upper position and balanced by means of a flood gate. The chamber 2 is then supplied with water from the reservoir 17 and as the tide drops, the vessel is released. This drives the pump 11 to pump water from the sea into reservoir 18 to provide further drive power to the generating means. The vessel is then held at its lower position and balanced by means of the flood gate. At high tide, the cycle is commenced again. Movement of water is controlled by a four way valve 12. <IMAGE>

Description

SPECIFICATION Tidal Power Method and Apparatus The present invention relates to a method and apparatus for generating e.g. electric power from changes in the level of a body of water such as a lake, river, or sea. The invention relates particularly to obtaining power through the generation of energy by means of repetitive upwards and downwards motion of a buoyancy vessel in accordance with the ebb and flow of the tide.

It is known to generate tidal electric power through the use of a dam beneath which a propeller is installed. The propeller rotates according to the ebb and flow of the tide and by means of energy produced by the rotation of the propeller, electric power generation is accomplished. However, the practical implementation of the said method can be difficult and expensive. There is also a defect, namely large losses of energy during the process of transforming the tidal energy to electric power.

Viewed from one aspect, the present invention provides a method of generating power from changes in the level of a body of water by means of upwards and downwards movement of a buoyancy vessel, wherein the vessel is held at a first position against upwards movement until a predetermined moment and is then released for movement upwardly to a second position, the mass of the vessel being reduced as it moves upwardly, and the vessel is subsequently held at the second position against downwards movement until a predetermined moment and is then released for movement downwardly to the first position, the mass of the vessel being increased prior to and/or as it moves downwardly.

Generally, the changes in level will be tidal. By holding the vessel against movement, e.g. after the start of ebb or flow of the tide, there will be an instantaneous production of power when it is released. By decreasing the mass of the vessel as it moves upwardly, and increasing it as it moves downwardly, the power generating effects are enhanced.

Preferably, the change in mass is accomplished by supplying water to, or pumping it from, the vessel. A pump can be driven by the movement of the vessel itself, and viewed from a second aspect the invention provides apparatus for generating power from changes in the level of a body of water comprising a variable buoyancy vessel supported for vertical movement with changes in the level of the body of water, means for holding the vessel at upper and lower positions, a pump for supplying water to drive a generator, means for placing the pump in communication with water contained in the vessel during upwards movement thereof, means for collecting water which has driven the generator so as to supply it to the vessel prior to and/or during downwards movement thereof, means for placing the pump in communication with the body of water during downwards movement of the vessel, and means whereby the upwards or downwards movement of the vessel drives the pump.

Preferably the means for driving the pump includes a gear train and means for automatically varying the gear ratio as the vessel moves upwardly and as the vessel moves downwardly. In this case the gear train advantageously includes a gear wheel selectively drivingly engageable with one of a pair of elongate gear members in accordance with whether the vessel is moving upwardly or downwardly, the members being disposed substantially parallel and tapering in opposite directions and the arrangement being such that when the gear wheel is engaged with either one of the elongate members rotation thereof causes axial movement of the point of engagement so as to vary the gear ratio.

With such an arrangement, it is possible to control the driving force of the pump so that it remains constant despite the nature of the upwards and downwards movement of the vessel driving the pump.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of tidal electricity generating plant in accordance with the invention; Fig. 2 is a side schematic view of part of the plant in a high tide condition; Fig. 3 is a view, similar to Fig. 2, of the plant in a low tide condition.

Fig. 4 is a partial view of a drive train used in the plant; Fig. 5 is a schematic enlarged view of a component of the drive train; Fig. 6A and Fig. 6B are schematic section views of part of the drive train, in different positions; Fig. 7 is a schematic view of another part of the drive train.

Fig. 8A to Fig. 8E are schematic views of a valve used in the plant, in different positions; and Fig. 9 is a schematic view of the buoyancy vessel used in the plant.

The electric power generating plant is installed on piles 1 built on the sea floor. A buoyancy vessel is mounted for vertical sliding movement on these piles and comprises an upper, variable buoyancy chamber 2 and a lower, fixed buoyancy chamber 3 filled with air. The upper buoyancy chamber is provided with a vent 9 to atmosphere at its upper end and a flood gate 1 9 adjacent its lower end.

A rack 4 is mounted on the side of the vessel and engages a pinion 5. This in turn drives bevel gears 29A and 29B so as to turn a drive shaft 6 when the vessel moves upwardly or downwardly.

The drive shaft 6 is connected to transmission apparatus 22 shown in detail in Figure 4. Through a pair of bevel gears the shaft drives a main gear wheel 7. This wheel 7 can be selectively engaged with either one of a pair of parallel, elongate, tapered helically wound gears 8A and 8B, sometimes referred to as "wreath shell gears".

The lead angle of the gears increases from the smaller diameter end to the larger diameter end while the pitch remains the same, as shown in Fig. 5. The teeth of the gears are formed helically on the surface. Each gear 8A, 8B is mounted on a shaft 8C, these shafts being supported by a frame 23 slidingly and pivotably mounted by means of a shaft 28. Control levers 27 are provided to pivot the frame 23 and select which of gears 8A or 8B is to engage the wheel 7. Levers 27 could be replaced by suitable electrical means. In either case, rotation of wheel 7 causes its engaged gear 8A or 8B, to rotate and to move axially, the direction of movement depending on which gear is engaged.

Each shaft 8C is drivingly engaged with a pinion 10 mounted on a pivotally mounted lever 25 provided with a weight 26 biasing the pinion upwardly into engagement with the shaft 8C. A locking member, or brake 30, is provided for each pinion 10 and can be selectively engaged to prevent movement of the transmission apparatus, and of course movement of the buoyancy vessel.

The shafts of gears 10 are drivingly connected, by suitable means (not shown) to the drive shaft of a pump 11. The outlet 1 5 from this pump leads to an upper reservoir 18 and the inlet is connected to a four way valve 12.

This valve is connectible via a conduit 1 6 to the sea water, via a conduit 14 to a lower reservoir 1 7, and via a conduit 13 to the interior of the variable buoyancy chamber 2. The valve can be controlled by suitable electrical means to select which of its four connections are in communication with each other.

The upper reservoir 18 supplies water via a conduit 20 to drive an electrical generator E connected by suitable wires to a transmission circuit. Water which has driven the generator is collected by the lower reservoir 1 7.

The operation of the plant is as follows. At high tide the valve 1 2 is in the position shown in Fig.

8A. When the brake 30 as shown in Fig. 7, is released, the buoyancy vessel rises which begins to move the rack vertically and the force for operating the pump 11 is instantaneously produced. At this point, the transmission apparatus 22 is in the condition shown in Fig. 6A and the gear wheel 7 engages with gear 8A, which rotates both the shaft 8C and the gear 10.

Through the operation of the pump 11, sea water contained in the buoyancy chamber 2 is pumped into the upper reservoir 18 through the conduits 13 and 1 5. As a result, the water level within the chamber is lowered thereby causing the buoyancy force to increase. When the buoyancy vessel reaches the highest position, it must stop. At that point, the previously pumped water drops from reservoir 18 through the duct 20 and generates electricity by means of the generator E. The water which has driven the generators is collected in the lower reservoir 1 7.

At this highest position, as shown in Fig. 2, the flood gate 1 9 is opened by suitable means, such as an electric switch as shown in Fig. 9, and the vessel rests at a height which balances the weight of the vessel and the buoyancy force. At that point, the gear 10 is locked by means of the brake 30. Accordingly, the buoyancy vessel is held up, even at low tide.

Subsequently, the flood gate 1 9 is closed by means of the electric switch and the four-way valve is activated to the position shown in Fig. SB.

The water from the lower reservoir 1 7 then flows into the chamber 2 thereby increasing the mass of the buoyancy vessel. However, before that time, the transmission apparatus 22 is changed from the Fig. 6A to the Fig. 6B condition thereby engaging the wreath shell gear 8B with the gear 7. During low tide, the brake apparatus is released and the buoyancy vessel 2 drops, and the four way valve activated to the position shown in Fig.

8C. As a result, force is instantaneously produced to drive the pump so that the outside sea water is pumped into the upper reservoir 18 whilst water can still flow from the lower reservoir into the buoyancy chamber 2. When the buoyancy vessel falls into an intermediate position, the four-way valve changes from the position shown in Fig. BC to that shown in Fig. SD by a suitable means of electrical control and thus, only outside sea water is pumped, the lower reservoir 1 7 being disconnected from the buoyancy chamber 2.

When the buoyancy vessel drops to the lowest position, the four-way valve is moved to the position shown in Fig. BE. Water is discharged from the buoyancy chamber 2 by opening the flood gate 19 by means of the switch shown in Fig. 9 so as to balance the buoyancy force of the vessel with gravity, after which time the flood gate 1 9 is again closed. Subsequently, the buoyancy vessel is fixed by the activation of the brake 30 and the transmission apparatus 22 is changed from the Fig. 6B to the Fig. 6A condition.

At this point the cycle is complete.

When the tide again rises, the brake is released causing the buoyancy vessel to rise and the four-way valve changes from the position shown in Fig. BE to that shown in Fig. 8A, and the cycle repeated.

Claims

1. A method of generating power from changes in the level of a body of water by means of upwards and downwards movement of a buoyancy vessel, wherein the vessel is held at a first position against upwards movement until a predetermined mornent and is then released for movement upwardly to a second position, the mass of the vessel being reduced as it moves upwardly, and the vessel is subsequently held at the second position against downwards movement until a predetermined moment and is then released for movement downwardly to the first position, the mass of the vessel being increased prior to and/or as it moves downwardly.

2. A method as claimed in claim 1 wherein the changes in level of the body of water are tidal.

3. A method as claimed in claim 2, wherein the vessel is held against upwards movement until after commencement of flow of the tide.

4. A method as claimed in claim 2 or 3 wherein the vessel is held against downwards movement until after commencement of ebb of the tide.

5. A method as claimed in any preceding claim wherein the mass of the vessel is decreased by pumping water therefrom and the mass of the vessel is increased by supplying water thereto.

6. A method as claimed in claim 5 wherein the pumping of water from the vessel during upwards movement is effected by a pump driven by the upwards movement of the vessel.

7. A method as claimed in claim 6 wherein the water pumped from the vessel is used to drive an electrical generator.

8. A method as claimed in claim 7 wherein the pump is driven by the downwards movement of the vessel to pump water from the body of water to drive the electrical generator.

9. A method as claimed in claim 7 or 8 wherein the water pumped to drive the electrical generator is supplied to a reservoir and thence to the generator.

10. A method as claimed in claim 7, 8 or 9, wherein the water which drives the electrical generator is supplied to a reservoir to be used for subsequent supply to the vessel.

11. A method as claimed in any preceding claim wherein the buoyancy vessel is balanced in the body of water after movement to the first position and after movement to the second position.

12. Apparatus for generating power from changes in the level of a body of water comprising a variable buoyancy vessel supported for vertical movement with changes in the level of the body of water, means for holding the vessel at upper and lower positions, a pump for supplying water to drive a generator, means for placing the pump in communication with water contained in the vessel during upwards movement thereof, means for collecting water which has driven the generator so as to supply it to the vessel prior to and/or during downwards movement thereof, means for placing the pump in communication with the body of water during downwards movement of the vessel, and means whereby the upwards or downwards movement of the vessel drives the pump.

13. Apparatus as claimed in claim 12, wherein the buoyancy vessel includes a fixed buoyancy tank and a variable buoyancy tank, the variable buoyancy tank being provided with means for placing the interior thereof in communication with the body of water.

14. Apparatus as claimed in claim 12 or 13 including an upper reservoir for receiving water from the pump outlet, the generator receiving water under gravity from the upper reservoir, a lower reservoir for receiving water under gravity from the generator and supplying it under gravity to the vessel, and a four way valve for selectively connecting the pump inlet to the vessel, the lower reservoir to the vessel, and the pump inlet to the body of water,

15. Apparatus as claimed in claim 12, 13 or 14 wherein means for driving the pump includes a gear train and means for automatically varying the gear ratio as the vessel moves upwardly and as the vessel moves downwardly.

1 6. Apparatus as claimed in claim 1 5 wherein the gear train includes a gear wheel selectively drivingly engagable with one of a pair of elongate gear members in accordance with whether the vessel is moving upwardly or downwardly, the members being disposed substantially parallel and tapering in opposite directions and the arrangement being such that when the gear wheel is engaged with either one of the elongate members rotation thereof causes axial movement of the point of engagement so as to vary the gear ratio.

1 7. Apparatus as claimed in claim 14 wherein each of said elongate gear members comprises gear teeth arranged on a helix of tapering radius.

18. A method as claimed in claim 1, using the apparatus as claimed in any of claims 12 to 17.

1 9. A method of generating power from changes in the level of a body of water, substantially as hereinbefore described with reference to the accompanying drawings.

19. Apparatus for generating power from changes in the level of a body of water, substantially as hereinbefore described with reference to the accompanying drawings.