WO2021240396A1

WO2021240396A1 - Tidal hydroelectric generating system

Info

Publication number: WO2021240396A1
Application number: PCT/IB2021/054593
Authority: WO
Inventors: Graham Hodgson
Original assignee: Tidal Renewable Energy Limited
Priority date: 2020-05-26
Filing date: 2021-05-26
Publication date: 2021-12-02
Also published as: GB202007829D0

Abstract

This invention relates to a system for generating hydroelectricity from the tides. The current tidal hydroelectric technology being used is completely limited to suitable geographic areas. Tidal barrages and lagoons are expensive to construct, use very large quantities of raw materials and energy and have detrimental environmental impact. They only generate roughly 40% of the capacity of the electric generator. The invention is suitable to be used on any ocean current and or coastal tidal including within harbours. An advantage is that relatively small amounts of materials are used in its construction. It has little or no environmental impact and is much less expensive to construct and deploy.

Description

Tidal Hydroelectric Generatinq System

Field

This present invention relates to a tidal hydroelectric generating system which exploits tidal height differences between two areas to generate electricity.

Backqround

Currently a problem when generating hydroelectricity from tides, occurs when using a conventional barrage across a tidal sea inlet or estuary to construct a tidal lagoon near to a coastal region.

In other instances tidal flow generators may be placed in the sea, making use of the energy of a tidal flow. The tidal flow of water then generates power by passing through turbines in a barrage or lagoon wall or through the tidal flow generator.

However, the use of these conventional systems suffers from several drawbacks. The construction of both the aforementioned types of tidal power generating systems are expensive, especially the barrage and lagoon constructions. Also currently tidal hydroelectric generation is limited geographically and can only usually be used in strong tidal flows or large tidal range locations suitable for the technology.

In addition, tidal flow generators can only exploit strong tidal current local to the tidal flow generator, which limits their geographical use and their generating capacity.

Furthermore the barrage and lagoon systems can be ecologically damaging to their locality, affecting sediment and other conditions due to damming and high water turbulence at the outlets of the turbines and at times, due to the need to flood large areas of previously shallow mud flats, where birds and other wildlife are affected.

Another drawback is that the barrage, and lagoon systems use large constructions which require very large quantities of raw materials and energy to construct.

The average power generation of barrage and lagoon systems is normally about 40% of the generator capacity. This is due to the high tide water that has to be held behind the barrage until a low tide when there is sufficient head of water to flow through the turbines to generate power.

Subsequently no power is generated until an incoming tide, that is held back from filling the coastal inlet, is allowed to flow through the turbines in the opposite direction to generate electricity.

The constructions of these tidal generating systems are subjected to the full force of storms, which has to be considered in the constructional mass and the maintenance systems of dams, breakwaters and barriers. Sea water is a corrosive environment, which makes the maintenance of all these turbines and their systems challenging when they are either underwater or enclosed in a dam. The electric cable connection to a tidal flow generator and the turbine has to be located underwater in this corrosive environment.

When tidal flow generators are located to make use of ocean currents, cabling may have to be many miles long. This causes problems with voltage drop where the cable hits landfall.

A number of existing tidal flow system have been proposed. Some examples of existing systems are described below.

Prior Art

French patent application FR 3 081 940 (ROSTAN) discloses a method and a system for producing, from sea or river currents, a circulation of water intended to turn a set of remote turbines for electrical energy generation. The system consists of submerged caissons which transform underwater currents into an accelerated flow of water which is routed using pipes to the turbines.

Japanese patent application JPS 57181976 (OCHIAI) discloses a generator connected to a water hammer pump whose pumping head and pump discharge are set in practical pressure ranges for the pump to discharge. United States patent application US 2015/0113968 (Christensen) describes a transient liquid pressure power generation system that includes a drive component, and a valve to cause a high pressure transient wave in the liquid traveling towards a liquid source to operate the drive component.

US patent US 6 606 857 (SIMONDS) discloses a fluid actuated power assembly for generating power from a pressurised fluid. A tube is provided for siphoning fluid from a body of water to a vane motor. A generator is coupled to the vane motor to produce electricity.

United States patent application US 2006/0181086 (MARTIN) discloses a hydroelectric power generating apparatus with one or more inlet pipes perpendicular to a flow of water in a stream or river. The inlet pipes have a length and have apertures along at least one inlet pipe. A feedline and a turbine generator combination are interconnected with the inlet pipes. One or more outlet pipes are interconnected with the feedline and the turbine generator. The outlet pipes have an elevation lower than the inlet pipe.

A flow of water passes through the inlet pipes, the feedline, the turbine generator combination, and the outlet pipes, and generates electricity from the flow of water passing through the turbine generator combination.

The invention arose in order to solve the problems associated with prior art and the aforementioned systems.

Summary of the Invention

According to a first aspect of the invention there is provided a hydroelectric generating system comprising: a network of pipes, interconnected with at least a first valve which is operative to open one end of a pipe in the network, when the first end is at a relatively high pressure location, and a second valve opens a second end of a pipe in the network, the second end is in a relatively low pressure location; at least one hydroelectric turbine is located between the relatively high and relatively low pressure locations so that water flows from the relatively high pressure location to the relatively low pressure location, through the at least one hydroelectric turbine, thereby generating electricity; and a control system remote from the valves is operative to actuate at least one of the valves in accordance with a signal from a processor the signal being dependent upon tide times. The present invention proposes a hydroelectric turbine, with the inlet and outlet fed from pipes serving two or more geographic areas, to exploit the potential energy of any tide and tidal currents, oceanic and or coastal without polluting environmental locations and without damage to them.

In preferred embodiments the invention is modular and can be removed after installation for upgrading, maintenance and repair and does not require the expense major infrastructure and construction equipment or materials, or use of barriers that are often associated with lagoons and conventional hydroelectric tidal flow generators.

In some embodiments at least one hydroelectric turbine is located on an oil rig platform. Alternatively at least one hydroelectric turbine is located on a decommissioned ship.

Preferably the at least one hydroelectric turbine is located on land. An advantage of this is that electricity can be transmitted directly to high voltage power lines in an electricity grid. Another advantage is that maintenance and repair cost are lower as turbines are housed in a conventional turbine hall and so do not have to be modified for undersea use.

Ideally at least one pipe is laid on the sea bed. Preferably at least one pipe is buried under the sea bed.

In an alternative arrangement at least part of a pipe may be floating on the sea or in a semi-submerged state. Suitable markings and warnings systems are incorporated in such floating or semi-submerged systems.

Pipes are ideally flexible in parts to allow a pipe inlet and/or a pipe outlet to be moved to open towards or away from a rising or falling tide. Actuators may be provided for orienting a pipe inlet towards or away from a direction of a tide. Preferably the actuator is a robotic actuator.

Preferably a means is provided to vary the size of a manifold or opening of a pipe inlet or outlet to accommodate fluctuations in turbulence or mass flow. Preferably the manifold is provided on an entrance of at least one of the pipes and reduces turbulence. Preferably one or more filters are provided to prevent fish and other debris from entering a pipe and damaging a turbine or killing aquatic life, such as fish.

In one embodiment, water may be delivered to a raised region or platform where a holding tank with a weir is located. In this case the water has potential energy by virtue of it being raised to an elevated position. The weir optionally has sluices over which fish can swim and escape. Alternatively grills or bars are provided to provide a by-pass route or channel for fish to swim through, whilst water is retained in a holding tank or reservoir, from which water drops through a height and passes through turbines, converting its potential energy into kinetic energy and then to electricity.

In some embodiments at least one pipe, or part of a pipe, is formed from a recycled plastics material.

Preferably the diameter of at least two of the pipes is different one from another.

Preferably a syphon is established between at least one of hydroelectric turbines and a pipe outlet.

Preferably valves are located at entrances/exhausts of pipes. However, in some embodiments, valves may be located between each end of a pipe and used to control flow through the pipe. Valves therefore may be located at interconnects, nodes, junctions or connections between two or more pipes.

In some embodiments a remote control system, which is operable to control one or more hydroelectric generating systems, may be included. The remote control system ideally includes: a communication system capable of operating valves, of one or more hydroelectric generating systems, from a remote location, so as to cause the hydroelectric generating systems to operate separate networks in a sequential manner with respect one to another. To make optimum use of the water flow in the pipe network it is beneficial for the control system to use flow metering. So that if required flow can be switched to the greatest water flow routes of the network.

Optionally control of valve opening and closing, including the sequence in which valves are opened and closed; the time at which they are opened and closed; and the degree to which each valve is opened and closed, is controlled by two or more inputs. Input signals may be provided to a remote control centre or directly to servos or actuators which oversee the opening and closing of valves. Signals indicating absolute and relative sea levels may be obtained from satellites.

In some embodiments, signals indicating absolute and relative sea levels may be obtained from buoys or measuring stations on a region of coast or on estuaries. By measuring sea height data and using this to control computer to allow the control to be adjusted to accommodate water that is blown by storms or high winds along a stretch of coastline.

An advantage of this configuration is that sea levels, are obtained from buoys and/or measuring stations and/or satellites and are processed by a computer to obtain control signals for control, valves in response to variations in weather conditions, such as variations in air pressure or storm surges.

Preferably outlets of pipes of the network are disposed at different locations, in tidal zones, so that valves are opened in a sequence according to location and tidal height in a zone, in order to maximise the period of electricity generation.

One of the main advantages and reasons for using an interconnecting pipe, against the currently used technology. Is to increase the seawater flowrate and velocity at the turbine by collecting the seawater from an area where there is a higher tidal rise than locally and then discharge the seawater to an area where there is a lower tide than locally.

In geographic areas where there is insufficient head of water to normally drive a turbine. The pipe effectively increases the head of water available to the turbine and overcomes this problem.

This system may be managed to generate electricity continuously by exploiting tidal progression as tides rise and fall along a particular stretch of coast. Preferably the generating system is deployed as a temporary structure.

Preferred embodiments of the invention will now be described with reference to the Figures in which: Brief Description of Figures

Figure 1 shows a diagrammatic view of a pipe with turbine blades and a generator for illustrative purposes;

Figure 2 shows a diagrammatical view of a pipe extending to two areas of water, at differing heights, separated by a land mass;

Figure 3 shows a diagrammatical views of a pipe extending through a land mass which connects two separate areas of water;

Figure 4 shows an aerial view of an embodiment of the invention deployed along a length of coast;

Figure 5 shows an embodiment of the invention where a turbine and generator are installed on a rig or decommissioned oil platform;

Figure 6 shows an embodiment of the invention where a turbine and generator are installed on a ship or floating platform;

Figure 7 shows an embodiment of the invention where a system of interconnected pipes is installed along a stretch of coastline with pipes branching into different geographical areas of the sea to exploit progressing tides;

Figure 8 shows an embodiment of the invention with a filter located at an inlet of the pipe to prevent fish and large objects from being drawn into the pipe;

Figure 9 shows an embodiment of the invention where a low flow turbine is provided which is switchable from a high pressure to a flow turbine by use of diverter valves; Figures 10 and 11 show examples of locations with prime tidal ranges that could be exploited within the local area;

Figure 12 is a diagrammatical view showing how a large pipe inlet reduces to a narrower bore in order to increase rate of flow;

Figure 13 illustrate diagrammatically where a turbine and generator are located on a sandbar or isthmus; and

Figure 14 shows an example of a mesh which is placed over a pipe inlet when a valve used as an inlet, prior to a valve being opened, in order to prevent ingress of debris and flotsam.

Detailed Description of Preferred Embodiments

The present invention proposes a hydroelectric turbine, with the inlet and outlet fed from pipes serving two or more geographic areas, to exploit the potential energy of tide and tidal currents, in the two or more geographic areas. Without pollution, environmental damage, geographic restrictions, or the use of barriers, lagoons and the geographic restrictions of hydroelectric tidal flow generators.

Theoretically an inlet pipe/s could be in say the river Seven and the outlet pipe/s just off the welsh coast and vice versa. This allows for the large tidal differences between any two geographic areas to be exploited. Considerable distances between tidal zones could be exploited with long pipes.

Figure 12 shows an instance where the open ends of the pipes 10 and or 16 are enlarged 28 to form a Venturi inlet. The water at 22 enters pipe 10 and the restriction of the Venturi and be forced to increase in flow rate 24, because water is not compressible. This difference in absolute water levels produces a head of water which results in kinetic energy (KE) when the water flows to drive turbines 10. This is also the case where ends of the pipes are manifolds with several inlets reducing to one pipe.

Referring to Figure 1 there is shown a diagram illustrating the principle of the invention. An inlet/outlet of a pipe 10 is joined to an inlet of a hydroelectric turbine 12. The outlet of the turbine 12 is connected to another inlet/outlet of pipe 16. Power output of the turbine 12 connected to and drives an electric generator 14. Figure 1 shows an instance where the turbine 12 and generator 14 are positioned closer to the outlet of the system to reduce turbulence in the pipes 16 after water has passed through the turbine 12.

Inlet and outlet ends of pipes can be effectively reversed depending on tidal conditions and in order to modify flow rates of water exiting a pipe. The control of inlet and outlet mass flow avoids or reduces turbulence in specific localities so as to avoid disturbing sediment, mud flats or areas of ecological importance. The fact that inlet/outlet sizes can be varied also has the advantage that the pipes 10 and 16 can be smaller in diameter and but as they are carrying the same mass flow of water, a higher velocity of water between inlet and outlet results.

Referring to Figure 2 there is shown an arrangement corresponding to that shown in Figure 1 and depicting a coastal area where pipe 10 is in a geographic area of higher tide 48. Pipes 10 are typically buried under the sea bed or underground. Turbine 12 and generator 14 are shown above sea level, located on land. Pipe 16 exits the turbine 12 and exhausts to an area of lower tide 50. It is understood that in use pipes 10 and turbine 12 are evacuated of air and fill with water. By establishing a syphon, this allows water to flow through the turbine 12, initially ‘uphill’ and pipes that are buried under the sea bed assist in creation of the siphon.

Figure 3 shows another example of the system where a turbine 12 and generator 14 are installed on the land 41 below an average sea level, so that no syphon is required for their operation.

Figure 4 shows an embodiment where the system is used for the progression of tides along a section of coast 46. Where pipe 10 is fed from a region of higher tide 48 via a turbine 12 driving a generator 14 on the land 46. Water then exits turbine 12 by pipe 16 to another geographical area of lower tide 50.

Referring to Figure 5, shows an instance where the turbine 12 and generator 14 are installed on an oil rig platform 60. Like parts bear the same reference numerals. In the embodiment shown in Figure 6 which shows a turbine 12 and generator 14 installed on a ship or floating platform 40. Figure 7 shows an embodiment where the system is installed at a coastal location 46 with pipes 10 and 16 branching into several geographical areas of the sea to exploit the progression of the tide by opening and shutting valves 42 in a sequential manner.

Referring to Figure 8 there is shown a filter 56 on one end of a pipe 10 to stop or inhibit fish and large objects from entering the pipe 10. Figure 9 shows an example of a low flow turbine 12 and how it can be switched with a higher pressure or higher flow turbine 18 by the use of diverter valves 42.

Figures 10 and 11 show various locations in the UK where normal tidal areas may be exploited by the invention.

Figure 12 is a diagrammatical view showing how a large pipe inlet reduces to a narrower bore in order to increase rate of flow.

Figure 13 illustrate diagrammatically where a turbine and generator are located on a sandbar or isthmus.

It is understood that the head of water of a higher tide in one or more geographic areas provides a hydrostatic pressure which drives a hydroelectric generators by when delivered to the generators by pipes. The resulting spent water is taken by pipes to one or more geographic areas of lower tide via a route in a network of pipes that is directed by valves and determined by a controller.

The potential energy of the tidal differences between geographic areas is therefore transformed into kinetic energy in the pipes and passed through the turbines to generate electricity.

The system therefore harnesses tidal differences, depicted by different heights of water in Figures 10 and 11 , between two or more geographic areas, can be coastal or oceanographic, or both. Theoretically an inlet pipe/s could be in say the river Seven and the outlet pipe/s just off the welsh coast and vice versa. This allows for the large tidal differences between any two geographic areas to be exploited. Considerable distances between tidal zones could be exploited with long pipes.

Figure 12 shows an instance where the open ends of the pipes 10 and or 16 are enlarged 28 to forming a Venturi inlet. The water at 22 entering the pipe will enter the restriction of the Venturi and be forced to increase in flow rate 24, because water is not compressible. This produces a greater kinetic energy to drive the turbines. This increase the efficiency of the system. The outlet end can be vice versa, dropping the flow rate of the exiting water, which will be less turbulent in the local environment. This also has the advantage that the pipes 10 and 16 can be smaller in diameter, carrying higher velocity water, in between geographic areas as well as being less expensive to construct and install.

Figure 13 shows an instance where the turbine 12 and generator 14 are positioned closer to the outlet of the system to reduce turbulence in the pipe after the water has gone through the turbine 12.

The hydroelectric turbine generator can be built at any convenient position and transported for local installation. Maintenance of the turbine is a lot easier with the turbine on land, or in any other convenient position out of the corrosive environment of the sea.

The hydro turbine generator inlet and outlet pipes may have multiple branches and or branch shut off valves/gates. These allow the management of the use of different geographical tidal differences, to provided optimal flow rates through the hydro generators, as shown for example in Figure 7.

In certain circumstances, with ocean currents and or with the progression of the tide along coastal areas, it is possible to generate energy on a constant basis, using pipes, valves and pipe branches. Unlike the current use of tidal barrages and tidal lagoons which may only be emptied at low tide and filled on a rising tide.

The pipes may be laid on the sea bed, use a syphon or inverted syphon if the generators are on land syphon maximum height of about 10 metres. The pipes could be floated on the sea or semi submerged or tethered. The pipes could be sufficiently flexible to allow the inlets or outlets of the pipes to be moved to follow the high and or low tide. This movement could be via robotic power heads, ships etc. The pipes could go over land, or be buried under the land, or tunnelled. See Figure 2 and 3.

The mouth or multiple mouths of the inlets and outlets can be in deep water, and if away from the sea bed, the turbulence helps to ensure against sediment disturbance.

If the water for one pipe was drawn from a multiple pipes on a manifold, the turbulence, would be further reduced, causing less water turbulence in the geographic area. In the embodiment shown in Figure 8 open ends of pipes 10 have filters to stop fish and other large objects entering the pipes and damaging the turbines. The flow through the pipe may be diverted between two or more turbines to allow for the different tidal flow rate between ebb and high tide to be exploited with turbines designed for low flow rates used at the ebb tide. Then being switched with a diverter to a higher flow rate designed turbine at higher tide. The invention exploits any tidal differences from different geographic areas, either very local (within a few hundred metres) and or far apart.

The addition of a gate/valve in any part of the pipe allows for the management of hydroelectric generation to match energy demand, when the demand for energy is low the gate/valve can be shut or partially shut and the difference in tidal zone height between the two or more geographical areas can be allowed to build until the energy demand is greater, then when the gate/valve is opened there will be greater potential energy between the geographic areas and this will convert to greater kinetic energy to drive the turbines. The laying of pipework is a lot less expensive than tidal barriers or lagoons.

This system may be deployed so that it exploits the tidal zones in busy harbours without any detriment to the shipping and normal business of the harbour, as can be seen for example in Figures 10 and 11. Like parts bear the same reference numerals as in the earlier Figures. However, in Figure 11 pipes with inlets A1 , A2 and A3 are opened to allow flow of water to exists at B2 and B3 respectively as tide ebbs and water drawing form within the harbour through harbour mouth indicated by ‘Hayling Golf Club’. Figure 14 shows an example of a mesh 100 which is placed over a pipe inlet 102 when a valve 104 used as an inlet, prior to the valve 104 being opened, in order to prevent ingress of debris and flotsam.

Likewise decommissioned North Sea oil and gas rigs may be used as offshore infrastructure. Furthermore the plastics waste recycling industry may be a source of plastic material for the pipework. Pipes are flexible and may be reinforced with a wire mesh or other strong tensile material.

Pipes may comprise steel pipes and synthetic plastics pipe sections connected together to enable pipes to flex and bend in strong currents, as well as define a strong and durable conduit for relatively faster flowing water which can withstand pressure differentials across the pipe wall which may arise. The system enables turbines to be ideally located above sea level so that in some embodiments water can be syphoned up an inlet pipe from the higher tidal area, through the turbine, then down the outlet pipe into the lower tidal area, thereby exploiting the difference in absolute water levels.

An advantage over tidal flow generators, is that instead of only being able to exploit the tidal flow at one position this invention can exploit the tidal zone as it is building over a larger geographic area, so it will be able to generate earlier and later on the same tidal flow that the tidal flow at the location of a generator.

As an illustration of a place where this could be used is between the Solent and Southampton harbour, Portsmouth Flarbour, and Langstone Flarbour in the south coast of the United Kingdom as shown in Figures 10 and 11 or the Menai Straits (not shown) off the Welsh coast where extreme tides are found.

Variation may be made to the aforementioned embodiments without departing from the scope of protection as defined by the claims.

Claims

1 . A hydroelectric generating system comprises: a network of pipes, interconnected with at least a first valve which is operative to open one end of a pipe in the network, when the first end is at a relatively high pressure location, and a second valve opens a second end of a pipe in the network, the second end is in a relatively low pressure location; at least one hydroelectric turbine is located between the relatively high and relatively low pressure locations so that water flows from the relatively high pressure location to the relatively low pressure location, through the at least one hydroelectric turbine, thereby generating electricity; and a control system remote from the valves is operative to actuate at least one of the valves in accordance with a signal from a processor the signal being dependent upon tide times.

2. A hydroelectric generating system according to claim 1 wherein the at least one hydroelectric turbine is located on an oil rig platform.

3. A hydroelectric generating system according to claim 1 wherein the at least one hydroelectric turbine is located on a decommissioned ship.

4. A hydroelectric generating system according to claim wherein the at least one hydroelectric turbine is located on land.

5. A hydroelectric generating system according to any preceding claim wherein at least one pipe is laid on the sea bed.

6. A hydroelectric generating system according to any preceding claim wherein at least one pipe is buried under the sea bed.

7. A hydroelectric generating system according to any preceding claim wherein at least one pipe is floating on the sea or are semi submerged.

8. A hydroelectric generating system according to any preceding claim wherein at least one pipe is flexible to allow a pipe inlet and/or a pipe outlet to be moved to open towards or away from a rising or falling tide.

9. A hydroelectric generating system according to claim 8 wherein at least one pipe is moved using a robotic actuator.

10. A hydroelectric generating system according to any preceding claim wherein a means is provided to vary a manifold of a pipe inlet or outlet to accommodate fluctuations in turbulence.

11. A hydroelectric generating system according to any preceding claim wherein one or more filters prevent fish and other debris from entering a pipe and damaging a turbine.

12. A hydroelectric generating system according to any preceding claim wherein at least one pipe is formed from a recycled plastics material.

13. A hydroelectric generating system according to claim 12 wherein the diameter of at least two of the pipes is different one from another.

14. A hydroelectric generating system according to any preceding claim wherein a manifold is provided on an entrance of at least one of the pipes for reducing turbulence.

15. A hydroelectric generating system according to any preceding claim includes a syphon which is established between at least one of hydroelectric turbines and a pipe outlet.

16. A hydroelectric generating system according to any preceding claim wherein valves are located at interconnects, nodes, junctions or connections between two or more pipes.

17. A hydroelectric generating system according to any preceding claim wherein outlets of pipes of the network are disposed at different locations, in a tidal zone, so that valves are opened in a sequence according to location and tidal height, in order to maximise the period of electricity generation.

18. A hydroelectric generating system according to any preceding claim which is deployed as a temporary structure.

19. A hydroelectric generating system according to any preceding claim includes a mesh which is movable to cover an inlet of a pipe and removable when water is expelled from the pipe.

20. A hydroelectric generating system according to any preceding claim wherein valves are opened and closed by a servo or an actuator.

21. A hydroelectric generating system according to any preceding claim wherein signals, indicating absolute and relative sea levels, are obtained from buoys and/or measuring stations and/or satellites and are processed by a computer to obtain control signals for control, valves in response to variations in weather conditions, such as variations in air pressure or storm surges.

22. A hydroelectric generating system according to any preceding claim includes a holding tank with a weir located therein.

23. A hydroelectric generating system according to claim 22 wherein the holding tank has sluices over which fish can swim or bars through which fish can swim, thereby avoiding ingress into a turbine.