WO2007148120A1

WO2007148120A1 - An electricity generation system extracting energy from liquid flows

Info

Publication number: WO2007148120A1
Application number: PCT/GB2007/002355
Authority: WO
Inventors: Robin Vernon Goodredge
Original assignee: Flow-Gen Limited
Priority date: 2006-06-23
Filing date: 2007-06-25
Publication date: 2007-12-27
Also published as: GB0612499D0

Abstract

This invention relates to an electricity generation system and more particularly to an electricity generation system adapted to extract energy from liquid flows, such as tidal or river water movement. The invention provides an electricity generation system comprising: a floating structure (10) which, in use, supports at least one electricity generator (18), there being defined in the structure at least one channel through which liquid flows and at least one turbine (16), which is located in the channel and is connected to the generator (18). The structure has deflectors at the entrances of channels to improve mass flow of liquid and stabilisers arranged on the structure so as to ensure optimal deployment with respect to tidal flows.

Description

_AN ELECTRICITY GENERATION SYSTEM EXTRACTING ENERGY FROM LIQUID FLOWS

Field

This invention relates to an electricity generation system and more particularly, but not exclusively, to an electricity generation system adapted to extract energy from liquid flows, such as tidal or river water movement.

Background

Extraction of energy from liquid flows, such as river water movement, has been used for centuries around the world, in the form of water mills for example for grinding grain.

In light of increasing global energy demand and reducing or static supplies of fossil fuels (and concerns over global warming) there is increasing demand to provide a greater variety of flexible electrical power generation from renewable sources.

Prior Art

A number of tidal power systems exist. One example of a tidal power generation system is described and claimed in US Patent US 4 208 875 (Tsubota). US Patent US 4 208 875 discloses an apparatus which extracts energy from waves and which includes a buoyant body from which electricity generation devices is supported.

However, it is felt that these are not efficient or sufficiently flexible to be deployed in shallow coastal conditions or rivers.

Another example of an electricity generating system is described in the Applicant's granted UK Patent GB-B-2 407 345 which discloses a tidal energy extraction device comprising: (i) a structure that is relatively fixed or anchored with respect to the seabed and having at least one open channel through which water flows; and (ii) a floating unit, which is displaceable with respect to the structure, said unit housing at least one impellor connected to a generator, whereby, in use, the impellor is/are located in the channel so that electrical energy is extracted by way of the generator.

The invention therefore arose in an attempt to provide improvements to an efficient and flexible electricity generation system adapted to extract energy from liquid flows, such as tidal or river water movement, particularly in shallow a coastal waters or in river flows.

Summary of the Invention

According to a first aspect of the invention there is provided an electricity generation system comprising: a floating structure which, in use, supports at least one electricity generator, there being defined in the structure at least one channel through which liquid flows and at least one turbine, which is located in the channel and is connected to the generator, characterised in that at least one deflector is arranged on the structure so as to direct liquid to flow through the, or each, channel thereby increasing the mass flow of liquid through the channel(s).

Ideally two or more stabilisers are provided.

In an alternative embodiment one or more conciliators are provided in order to calm or moderate waves impacting the structure so as to shape and waves in order that as much energy can be extracted from waves impacting the generation system.

A support structure is located so as to permit the floating structure to rise and fall with respect to tidal variations whilst remaining in substantially the same location. Preferably the support structure secures the floating structure, with respect to the sea or river bed, so that the floating structure remains in substantially the same location, during rising and falling tides.

The means of securing the floating structure may be by way of tethers or by mounting it to a relatively fixed structure supported on the sea/river bed so that the floating structure may rise and fall with respect to the fixed structure.

The generation system is incorporated into a floating structure, such as a barge, pontoon or other buoyant structure. This ensures that the correct amount of turbine blade is always presented to a tidal flow.

Preferably channels is/are defined by solid wails formed in the structure and is/are adapted to be oriented so as to be substantially parallel to the direction of tidal flow.

The buoyant structure ideally has a deck, which may support additional power generating equipment such as wind driven turbines and/or solar panels.

The fact that liquid is directed to flow through the channels, and an ideal amount of turbine blade is presented to the flow of liquid, ensures that optimum conditions are present for energy extraction from the liquid flow.

Ideally a deflector is provided on the floating structure so as to direct liquid to flow through the, or each, channel thereby increasing the mass flow of liquid through the channel(s).

The fact that one or more channels is/are defined between first and second wails has the advantage that liquid flows are directed an appropriate angle to impact turbine blades and thus drive them.

Means may be provided to alter the angle or pitch of turbine blades ahd/or the depth of water coverage of the blades and/or the angle of incidence of the axis of rotation of the turbine with respect to the direction of liquid flow. These features permit trimming of the turbine blades in order to accommodate for example, variations in sea conditions.

Advantageously a microprocessor may be arranged to monitor conditions and to control automatically the aforesaid features for trimming turbine blades.

Overall, the invention may be used in shallow waters, for example coastal waters or river flows or, if suitable securing is available, in deeper waters.

Ideally, in the case of the floating structure, there are at least two channels, located adjacent to a generally rectangular structure, allowing turbines to be grouped in pairs.

Preferably, further pairs of channels may be located adjacent to further of the generally rectangular structures within a floating mainframe.

Preferably a plurality of turbines is located in each of the channels.

A main support frame provides the rigidity required to keep a turbine shaft properly aligned with its supporting bearings.

The main support frame of the floating structure also provides walls for the channels and may also be constructed to provide: one or more of the following: a channel floor below the turbine blades to contain the water flow and/or a channel roof to prevent overspill from waves or other liquid movement.

The position of the main support frame relative to the liquid surface can be controlled by ballast and/or air tanks or other buoyancy aids.

Adjustment of buoyancy may be automatically controlled and powered from electrical power from the generators. Entrances to each channel may be guarded by one or more anti-fouling gates or traps arranged to divert debris and prevent it form entering the channels.

At the ends of each channel a deflector/compression devices may be fitted in order to maintain a head of water, thereby ensuring consistency of water flow to the turbines.

Shafts from the turbines are ideally connected to a gear-box, which in turn is connected to an electricity generation system (or generators), thereby allowing kinetic energy from liquid movement to be converted into electrical power.

Electricity is then transferred to a place of use, sub-station or to an electrical grid connection through power lines, running either below and/or above water level.

The floating structure is ideally protected by a wave barrier (wave breaker), to reduce liquid overspill on to the upper surfaces of the structure.

Navigation lighting, marker buoys, radio beacons and other appropriate warning signs may be used to mark its location.

Generators may be in self-contained pods, which are modular and therefore removable by crane or other lifting gear, for servicing, repair or replacement, in situ or in dry or wet dock.

Turbine blades may be constructed to allow uncoupling from the generators, so that they also may be removed for servicing, repair or replacement, in situ or in dry or wet dock.

The support structure may be prefabricated or assembled in situ, from modular or basic components, and may be made from steel, fibre-glass composites or any other material(s) suitable to provide required rigidity and strength. Assembly of the support structure may be achieved through frameworks, cabling or other stabilising method that is connected or affixed to the sea-bed. The support structure does not necessarily have to float, but is arranged so as to allow the floating structure to rise and fall as the liquid levels rise and fall, and so keep it on the liquid surface.

The support structure may be prefabricated or assembled in situ, from modular or basic components, and may be made from steel, fibre-glass composites or any other material(s) suitable to provide the required securing of the floating structure.

The invention provides access to predictable renewable energy sources to supply power into established local, regional or national grid systems or, in remote situations, to provide a local source of power.

An additional advantage is that the invention does not need deep water to operate and so can be situated in fast flowing shallow water situations away from shipping lanes, sailing or fishing areas.

It is possible to capture water flow in either direction, as occurs with tidal flows.

Brief Description of the Figures

Figure 1a shows a diagrammatical plan view of a floating electricity generation system showing a mainframe, channel, turbines and generators;

Figure 1b shows a diagrammatical side view of a floating electricity generation system showing the mainframe, stabilisers and tethers to the seabed;

Figure 2a shows a diagrammatical plan view of an electricity generation system showing a mainframe with a single set of turbines; Figure 2b shows a diagrammatical plan view of an electricity generation system showing a mainframe with twin sets of turbines and four channels;

Figure 3a shows a cross-sectional view, taken along a turbine channel, to show turbine arrangement and liquid level;

Figure 3b shows a cross-sectional view, taken across part of the mainframe and two of the channels, to show turbine arrangement and liquid level;

Figure 4 is a cross-sectional view, taken across part of the mainframe and two of the channels and shows the relationship between turbines, gearbox and an electrical generator;

Figures 5a and 5b show front elevational views of a stabiliser unit suitable for use with a mainframe of the electricity generation system; 5a shows stabiliser retracted; 5b shows stabiliser extended down.

Figure 6 shows a diagrammatical side view of a part of an aqua foil horizontal stabilising unit for use with a mainframe of the electricity generation system;

Figure 7 shows an overall diagrammatical view of a stabilising unit for use with a mainframe of the electricity generation system;

Figure 8 shows a diagrammatical plan view across part of the mainframe and illustrates how stabilising units are secured to the mainframe of the electricity generation system.

Figure 9 additionally shows alternative profiles of nose ends;

Figures 10a and 10b illustrate diagrammatically how conciliator plates calm impacting waves in moderate sea conditions (Figure 10a) and in more severe sea conditions (Figure 10b).

Detailed Description of Preferred Embodiments of the Invention Referring to Figure 1a there is shown a two-channel structure 10, with each channel 20 containing four turbines 18 arranged in a tandem arrangement - that is eight turbines 18 in total. Turbines 18 are in turn connected to generator 16.

Referring to Figures 2a and 2b there is shown a four-channel structure 10, with each channel containing four turbines 16 in tandem arrangement - that is sixteen turbines in all. Again turbines 16 are connected to generators 18.

The channels 14 is/are defined by solid walls formed in the structure 10 and is/are adapted to be oriented so as to be substantially parallel to the direction of tidal flow. The fact that liquid is directed to flow through the channels by way of baffle plates or deflectors 44, and because an ideal proportion of turbine blade 17 is presented to the flow of liquid, ensures that optimum conditions are present for energy extraction from the liquid flow.

Ideally one or more deflectors 44 is/are provided on the floating structure 10 so as to direct liquid to flow through the, or each, channel 20 thereby increasing the mass flow of liquid through the channel(s) 20.

The fact that one or more channels is/are defined between first and second walls has the advantage that liquid flows are directed to be perpendicular to the turbine axis.

The angle or pitch of turbine blades 17 may be altered. Additionally the depth of water coverage of the blades 17 may be altered. Furthermore the angle of incidence of the axis of rotation of the turbine 16 with respect to the direction of liquid flow may be altered. These features permit trimming of the turbine blades 17 in order to accommodate for example, variations in sea conditions. Sensing means (not shown) may be provided and used to provide a signal to actuators (not shown) so as to achieve this trimming effect automatically. Referring to the Figures generally, in which like parts bear the same reference numerals, an electricity generation system comprises: a floating structure 10 having a deck 12 and which, in use, is tethered or supported by way of tethers 14. At least one electricity generator or dynamo 18 is driven by water flowing through at least one channel 20 defined in the structure 10. The flowing water turns at least one turbine 16, which is/are located in the channel 20 and is connected, for example by way of a shaft or gearbox 19 to the generators. Aqua foils 34 act to maintain the structure 10 at an optimum angle to impacting waves so as to improve the efficiency of energy extraction from the waves.

Referring again to Figures 2a and 2b there is shown conciliator panels 22 arranged so as to calm or moderate the effect of impacting waves. The calming effect of the conciliator panels 22 is seen in diagrammatical detail in Figures 10A and 10B. Although not shown in the Figures it will be understood that actuators may be provided to control the conciliator panels 22 so as to alter their angle to oncoming waves and/or height form sea-level, thereby providing a system of wave regulation that can be controlled in dependence of the sea conditions.

Figures 3a shows a cross-sectional view along channel 20 and shows in diagrammatical format four sets of turbine blades 17a, 17b, 17c and 17d. Front upper portions of conciliators panels 22 are shown at fore and aft locations of the structure. The fact that conciliator panels 22 are at both ends of the channel illustrate the "reversibility" of the system: namely that it is capable of being used bi-directionally so as to be able to extract energy from a rising as well as a falling tide. Figure 3b shows a cross-sectional view, taken across the structure 10 of the mainframe and shows two lateral channels 20 and opposite sets of turbine blades 17.

Figure 4 shows a more detailed cross-sectional view through the structure 10 and the relationship between turbine blades 17, turbines 16, gearbox 19 and generator and 18. Also shown are outer skirt 23 which encloses turbine blades 17 and defines one of the walls of channel 20. Figures 5a and 5b show front and side elevational views of a stabiliser unit 26 which in use are bolted or otherwise attached to the structure 10 and are shown diagrammatically in Figure 1 below the structure. Typically the stabiliser is in the form of a flat plate 36, which is supported by and movable within a frame 38. The stabiliser would be extended to its maximum when on station in very rough seas and can be withdrawn in calmer conditions or for repair or servicing of the main unit, rather like a retractable keel. An overall, diagrammatical view of a stabilising unit is shown in Figure 7. The stabiliser unit has two lifting eyes 40a and 40b An angled aqua foil 42 reacts against tidal currents and helps to maintain the structure in an horizontal position in order to maximise the effects are shown in detail in Figure 6.

Referring briefly to Figure 6, there is shown a diagrammatical view of a part of an aqua foil 34 horizontal stabilising unit 26. The purpose of the stabilising unit is to act by containing a body of water, which will have a damping action on vertical (and lateral) movement. Figure 7 shows an overall diagrammatical view of the stabilising unit 26 for use with the electricity generation system.

Referring to Figures 8 and 9 there is shown a diagrammatical plan view and overall view respectively of the mainframe and illustrates how stabilising units 26 are secured to the mainframe of the electricity generation system and additionally shows alternative profiles of nose ends. Figure 9 shows in greater detail a sectional view of stabiliser pods or units 26 in a ballast tank 28. Ideally two or more stabiliser units 26 are located in a symmetrical arrangement. The stabiliser units 26 are adapted to calm or moderate waves impacting the structure.

A support structure, typically embedded in the seabed, is located so as to permit the floating structure to rise and fall with respect to tidal variations whilst remaining in substantially the same location. An advantage with this is that shipping is aware of the relatively permanent position of the generation system as the floating structure remains in substantially the same location, during rising and falling tides. The floating structure is secured by way of tethers 14 anchored onto or into the sea bed or by mounting it to a relatively fixed structure, such as a concrete block (not shown) supported on the sea/river bed so that the floating structure may rise and fall with respect to the fixed structure.

The generation system may be incorporated into a floating structure, such as a barge, pontoon or other buoyant structure. This ensures that the correct amount of turbine blade is always presented to a tidal flow.

Figures 10a and 10b illustrate diagrammatically how conciliator plates 50 calm impacting waves in moderate sea conditions. In Figure 10a, in relatively calm sea, waves pass below conciliator plates and impinge directly on turbine blades. In rougher sea conditions impacting waves, of a greater amplitude, impact on conciliator plates with the result that tidal flow below the conciliator plate is permitted to pass through the channels. Thus it will be appreciated that the conciliator plates are of more use in more severe sea conditions.

Inner and outer turbines are connected to a generator by way of a common drive shaft through a gear box.

The invention has been described by way of example only and it will be appreciated that variation may be made to the embodiments herein described.

Claims

1. An electricity generation system comprising: a floating structure which, in use, supports at least one electricity generator, there being defined in the structure at least one channel through which liquid flows and at least one turbine, which is located in the channel and is connected to the generator, characterised in that at least one deflector is arranged on the structure so as to direct liquid to flow through the, or each, channel thereby increasing the mass flow of liquid through the channel(s).

2. An electricity generation system according to claim 1 wherein at least one stabiliser is provided in order to maintain the structure at an optimum orientation to oncoming liquid flow.

3. An electricity generation system according to claim 1 or 2 wherein adapted to capture water flow in either direction, as occurs with ebbing and flowing tidal flows.

4. An electricity generation system according to any preceding claim wherein a support structure is located so as to permit the floating structure to rise and fall with respect to tidal variations whilst remaining in substantially the same location.

5. An electricity generation system according to claim 4 wherein the support structure is in the form of tethers, such as connectors or cables, secured to the sea or river bed.

6. An electricity generation system according to any of claims 1 to 4 wherein the means of securing the floating structure includes a mounting system adapted to support the structure on a sea/river bed so that the floating structure may rise and fall with respect to the fixed structure.

7. An electricity generation system according to claim 6 wherein the means of securing the floating structure includes piles arranged to be received by the floating structure, such as a barge, pontoon or other buoyant structure.

8. An electricity generation system according to any preceding claim having a means to orient the structure so that, in use, channels are substantially parallel to the direction of tidal flow.

9. An electricity generation system according to any preceding claim wherein a means is provided to alter the angle or pitch of turbine blades with respect to the direction of liquid flow.

10.An electricity generation system according to any preceding claim wherein a means is provided to alter the depth of water coverage of the turbine blades.

11.An electricity generation system according to any preceding claim wherein a means is provided to alter the axis of rotation of the turbine with respect to the direction of liquid flow

12.An electricity generation system according to any of claims 9, 10 and 11 wherein sensors are arranged to monitor conditions and to provide control signals to automatically control the trimming of the turbine blades.

13.An electricity generation system according to any preceding claim wherein at least two channels are provided said channels are located adjacent to a generally rectangular structure and allow turbines to be grouped in pairs.

14.An electricity generation system according to any preceding claim wherein the position of a support frame, relative to the liquid surface, is controlled by ballast and/or air tanks or other buoyancy aids.

15.An electricity generation system according to claim 14 wherein adjustment of buoyancy is automatically controlled and powered from electrical power from the generators.

16.An electricity generation system according to any preceding claim wherein the structure has entrances to each channel guarded by anti- fouling gates.

17.An electricity generation system according to any preceding claim wherein the means of securing the floating structure is protected by a wave barrier (wave breaker), to reduce liquid overspill on to the upper surfaces of the structure.

18.An electricity generation system according to any preceding claim wherein navigation lighting, marker buoys, radio beacons and other appropriate warning signs are fitted to the structure.

19.An electricity generation system according to any preceding claim wherein the floating structure is formed from self-contained pods, which are modular and replaceable.

20.An electricity generation system according to claim wherein the turbine blades may be constructed to allow uncoupling from the generators, so that they also may be removed for servicing, repair or replacement, in situ or in dry or wet dock.

21.An electricity generation system according to any preceding claim wherein the support structure is prefabricated from modular or basic components.

22.An electricity generation system according to any preceding claim wherein nose ends are provided in order to divert liquid flow through the channels.

3.An electricity generation system substantially as herein described with reference to the Figures.