GB2401404A

GB2401404A - Wave powered generator with air driven turbine

Info

Publication number: GB2401404A
Application number: GB0310667A
Authority: GB
Inventors: Jeremy William Whitham
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-05-09
Filing date: 2003-05-09
Publication date: 2004-11-10
Also published as: GB0310667D0

Abstract

A wave powered power generation system comprises two parallel tubular members 101, 102 positioned vertically, each having a lower open end 105, 106. The upper ends of the members are connected by at least one passage 107, 108 containing an air driven turbine and generator unit 110. Air flows through the passage, passing from one tubular member to the other as a result of pressure differences at the open ends of the members, as waves pass by. The turbine is then driven by the movement of the air in the passage.

Description

1 2401 404

WAVE-POWERED ELECTRICITY GENERATOR

The present invention relates to electricity generation systems which are powered by the action of waves.

A number of systems for converting the energy contained in sea waves into electricity have been proposed. One type of wave-powered electricity generation system utilises floating structures the movement of which by waves is converted into electricity. A second type of wave-powered electricity generation system utilises the movement of sea lo water or air as a result of wave action to drive one or more low pressure turbines.

An example of the first type of device is the eccentrically pivoted assymetric floats invented by Professor Salter. Examples of the second type of device are shown in patent specifications GB 2,005,358 and US 6, 291,904. Patent specification GB 2,005,358 discloses a system in which two submerged chambers are inter-connected by a passage in which is situated a low-pressure turbine. One chamber incorporates non-return valves which enable sea-water to enter and pressurise air in a gas space and the other chamber incorporates non-return valves which allow sea water to pass out of the chamber. In effects the air in the first chamber acts as a gas spring forcing water through the channel 2, and turbine to the second chamber thence to exit back to the sea.

Patent Specification US 6?29l,904 discloses a system in which an openended tube is positioned vertically, the top end being at a depth at which wave action causes significant changes in the depth of immersion of the upper end of the tube and the lower end of the tube is at a depth such that wave action at the surface does not cause significant changes in the depth of immersion of the lower end of the tube. It is stated that the difference between the conditions at the top and bottom of the tube cause movements of water within the tube. In some embodiments of the invention described, these water movements cause corresponding movements of a piston within the tube. The piston is coupled to an hydraulic motor which, in turn, drives an electrical generator. In another embodiment of the invention, a low-pressure turbine is positioned within the tube with its axis of rotation co-axial with the longitudinal axis of the tube. The turbine is coupled to an electrical generator.

Quite apart from any doubts about the physics of the invention disclosed in specification US 6,291,9047 both the above designs of wave-powered electricity generation systems suffer from the disadvantage that at least the power generator drive systems of both are submerged in sea water, which is a very corrosive environment and would require lo hermetical sealing of the generators and/or their drive systems.

According to the present invention, there is provided a wave-powered power generation system comprising two parallel tubular members each having an open end and a closed end positioned with their closed ends adjacent, means for positioning the tubular Is members vertically with their closed ends uppermost, at least one passage connecting the closed ends of the tubular members, means for causing air to flow through the passage from one tubular member to the other as a result of pressure differences at the open ends of the tubular members arising from waves passing sequentially past the tubular members and a turbine adapted to be driven by the air passing through the said passage.

Preferably the turbine is arranged to drive an electrical power generator.

In use, the two tubes are installed in a position such that the upper ends of the tubes will remain immersed at all states of the tide, if applicable, and wave conditions likely to be experienced at the position of use of the power generation system.

Preferably, there are two passages linking the closed ends of the tubes and there is included a system of one-way valves such as to establish a unidirectional direction of air flow through the turbine.

One of the tubular members may be common to a plurality of other tubular members disposed regularly around it thereby to render the wave-powered energy generation system insensitive to the direction of waves passing over it as well as to maximise the power generation capability of the system.

Preferably, there is included means for ensuring that an air space remains at the upper ends of the tubular members at all times thereby to provide buoyancy in the tubular members.

At least a section of the walls of the tubular members may be made to be flexible, thereby to increase the displacement of air as a result of waves passing over the tubular members.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: o Figure 1 is a diagrammatic representation of a wave-powered electrical power generation system embodying the invention and illustrates the action of the system, Figure 2 illustrates the embodiment of figure 1 modified to provide buoyancy chambers, 2s Figure 3 illustrates a second modified version of the embodiment of figure 1, and Figure 4 is a diagrammatic representation of a second embodiment of the invention.

Referring to Figure 1, a wave-powered electricity-generating system embodying the invention consists of two parallel tubular members 101, 102 which are closed at one end, 103, 104, respectively, and open at the other, 105, 106, respectively. The tubular members 101, 102 are positioned in the sea vertically with their closed ends 103, 104 s arranged to be below the lowest tidal level and wave trough anticipated in the position where the electricity generating system is to be used. The tubular members 101, 102, may be fixed to the sea bed, or maintained in position by anchors or other moorings, which are not shown in the drawing. Two passages 107, 108, respectively, link the interiors of the upper ends 103, 104 of the tubular members 101, 102 and a cross lo passage 104 connects the passages 107, 108. Located in the cross-passage 109 is a combined low-pressure turbine and electricity generator 110. Non-return valves 111 are positioned at the junctions between the tubular members 101, 102 and the passages 107, 108 and function in the manner shown to cause air to flow unidirectionally through the cross-passage 109 and turbo-generator unit 110, regardless of whether air is flowing Is from the tubular member 101 to the tubular member 102 or vice versa as a result of waves passing sequentially over the tubular members 101, 102. Ideally, each installation should have the lengths of the passages 107, 108 be chosen to equal approximately half the wavelength of the waves most frequently occurring at the position in which the power generator is installed, as this maximises the static pressure differential between the so open ends 105, 106 of the tubular members 101, 102.

Figure 2 shows a modified version of the embodiment of the invention described with reference to figure 1 which is suitable for use when the power generator system is moored to the sea bed. The upper passage 107 is situated above the closed ends 103, 2s 104 of the tubular members 101, 102 and has two downwardly directed extensions 201, 202 which pass through the closed ends 103, 104 of the tubular members 101, 102. Two float valves 203, 204 are arranged to close off the extensions 201, 202 of the passage 107 should the water levels in the tubular members 101, 102 rise excessively.

The modification ensures that whatever the sea conditions, air spaces remain at the upper, closed ends 103, 104 of the tubular members 101, 102, so as to provide and maintain buoyancy in the tubular members 101, 102. The remainder of the apparatus is as described with reference to figure 1.

Figure 3 shows a modified version of the invention as described with reference to figure 2 in which areas 301, 302 of the walls of the tubular members 101, 102 are made to be flexible so that they deflect inwards when the pressure is increased as a wave passes over the appropriate tubular member 101 or 102, decreasing the area of the tubular member lo]01 or 102andincreasingtherateofairflowthroughtheturbo-generatorunit 110.

Figure 4 shows a simplified version of the present invention in which there is only one cross-passage, 401. In this case, the airflow will reverse its direction each time a wave passes across the apparatus and the turbine of the turbogenerator unit will have to be of a type which is insensitive to the direction of air flow through it.

The direction of waves is a function of the direction of the wind which generates them.

Thus, if the wind is blowing at right angles to the cross-passages 107, 108, then the tubular members 101, 102 experience the passage of a wave simultaneously and there is 2) no pressure differential across their lower ends 1OS and 106 so that no air passes from one to the other to drive the power generator l lo. This problem can be avoided by positioning groups of power generator units radially about a central position. In particular, one central tubular member can be made to be common to a number of other tubular members grouped regularly around it.

Power generators embodying the present invention are modular in concept and the power generation capacity of a given station can be chosen by including an appropriate number of units in the station.

Claims

1. A wave-powered power generation system comprising two parallel tubular members each having an open end and a closed end positioned with their closed ends adjacent, means for positioning the tubular members vertically with their closed ends uppermost, at least one passage connecting the closed ends of the tubular members, means for causing air to flow through the passage from one tubular member to the other as a result of pressure differences at the open ends of the tubular members arising from waves passing sequentially past the tubular members and a turbine adapted to be driven by the air passing through the said passage.

2. A power generation system according to claim I wherein there is provided means for rendering the tubular members buoyant.

3. A wave-powered power generation system according to claim 2 wherein there is included means for ensuring that air spaces remain within the tubular members at all times thereby to provide buoyancy in the tubular members.

4. A power generation system according to any of claims I to 3 wherein at least a portion of the walls of the tubular members is flexible thereby to increase the displacement of air as a result of waves passing over the tubular members.

5. A power generation system according to any previous claim wherein there is a plurality of individual power generation systems arranged radially around a central point thereby to render the overall power generation system insensitive to the direction of waves passing over it.

6. A power generation system according to claim 5 wherein a central tubular member is common to a plurality of other tubular members disposed about it and linked to it by the said passages.

7. A power generation system according to any preceding claims wherein there are two passages linking the tubular members and there is included a system of one-way valves such as to establish a unidirectional flow of air through the turbine at all times.

8. A power generation system according to claim 7 wherein there is included a cross- passage joining the said two passages and the turbine is located in the cross- passage.

9. A power generation system according to any of claims I to 6 wherein there is a single passage linking the two tubular members and the turbine is adapted to accommodate the reversing flow of air as a wave passes sequentially over the tubular members.

10. A power generation system according to any preceding claim wherein the turbine is adapted to drive an electricity generator.

11. A wave-powered power generator system substantially as hereinbefore described and with reference to the accompanying drawings.