HK1160895B - Method and apparatus for installing tidal barrages - Google Patents

Description

Method and apparatus for installing tidal barrages

Technical Field

The present invention relates to the construction of barrages which can be used to extract energy from the flow of tidal or water currents for the generation of electricity. Background

There have been many proposals for generating electricity from tidal or current flows in bodies of water as a pollution-free way of generating electricity. Such systems have involved the use of a blade through which the flow causes vibration, and a mechanical drive system to convert the vibration into rotary motion. Such systems face a number of problems, such as: they are mechanically complex, require tuned behavior, and they are generally unable to extract energy from other types of motion.

Other systems feature a large underwater propeller that resembles a windmill, but is used for water flow rather than wind flow. In order for the swept disc to be exposed to the maximum incident flow energy, the vanes must be very long, which in turn requires complex designs and materials to accommodate the stresses at the vane root.

Offshore tidal barrages have been proposed to concentrate the incident energy of large cross-sectional water flows by capturing the water flow behind a containment wall and funneling it through a turbine having a much smaller cross-sectional area, as in conventional dams. Such barrages (typically across a tidal estuary) are very expensive and environmentally damaging.

A common problem for all these systems is that it is possible to deal with a sufficiently large cross section of the ocean or other body of water to enable the generation of electricity on an industrial scale. In addition, end or edge effects may make it easier for the water stream to bypass any structure positioned in the water stream to extract energy therefrom rather than pass through the energy extraction system. This problem can be mitigated by making a facility very large, but this in turn can lead to further complexity and expense and may exceed current engineering capacity limits.

WO 2008/015047 discloses an improved device for converting energy from the flow of a wave or water stream in which a series of pipes are arranged to define a venturi. The flow of water between the conduits causes the venturi to act as pumps which pump water through the conduits (which are supplied by a manifold flow conduit) and drive an impeller. The series of pipes are arranged to form arrays having vertical faces, which in turn are erected on the seabed to form a barrage.

The present invention seeks to overcome some of these deficiencies outlined above in relation to tidal barrages by providing a modular construction, allowing for easier installation than was possible with previous designs. Furthermore, the installation of barrages across an estuary from bank to bank or across a strait from coast to coast eliminates end and edge effects. The present invention is based on a modular application of the technology disclosed in a broad sense in WO 2008/015047. Disclosure of the invention

A first aspect of the invention provides a method of installing a barrage across a body of water for generating power from the flow of tides or currents, the barrage being formed from a series of modules each comprising: a base structure carrying a plurality of substantially upright tube structures in a spaced, side-by-side arrangement; and a deck structure extending across the tops of the tube structures and supported by at least two tube structures, the method comprising: preparing a series of foundation platforms across the bed of the body of water in a direction substantially perpendicular to the flow of the tide or current, each foundation platform providing a substantially flat base on which the base structure of one or more modules can be positioned; and positioning a series of modules side-by-side on the platforms such that the base portion of each module rests on one platform and the deck structure of each module is at substantially the same elevation as the deck structure of its adjacent module.

A full depth weir traversing the entire width of the body of water is constructed to maintain the bow wave effect by ensuring that incident flow is directed through the weir thereby eliminating edge losses. Maintaining the upstream bow wave allows conversion of potential energy beyond the Betz limit to electrical energy.

Each foundation platform is preferably formed by a linear revetment positioned at the bed of the body of water, the method further comprising altering the profile of the bed adjacent each revetment by dredging and/or dumping material to match its shape.

The base structure of each module may be secured to the foundation platform by grouting.

Each module may be floated into position above its corresponding base platform and lowered into position by controlled flooding of the module. In one embodiment, the base of each module includes a manifold, and the tube structures are connected to the manifold and have a series of holes along their sides through which water can flow during power generation. In this case, the mounting method may include temporarily closing the holes as the module floats into place, and then fully opening the holes once the module is mounted.

In a preferred embodiment, the method further comprises forming a lock between the two modules to allow the surface vessel to pass through the barrage. The method may further comprise forming a road, rail or airstrip on the deck structure.

The plurality of modules may be selected from a group of modules having different deck heights above the base unit, the module being selected according to the depth of water in which it is to be located.

A second aspect of the invention provides a module for use in the method according to the first aspect of the invention, the module comprising: a base structure defining a manifold; an inlet in the manifold, the inlet housing an impeller connected to drive a generator; a plurality of substantially upright tube structures mounted in a spaced, side-by-side arrangement on the manifold for connection thereto, each tube having a series of apertures formed along a side thereof facing its adjacent tube such that flow between adjacent tubes causes a venturi effect whereby water is drawn from the manifold through the apertures, thereby causing water to be drawn into the manifold through the inlet to drive the impeller; and a deck structure extending across the tops of the tube structures and supported by at least two tube structures.

The generator is typically located at or near the deck structure.

At least some of the tube formations terminate below the deck so that in use they lie above but close to the normal high water level.

A third aspect of the invention provides a module for use in the method according to the first aspect of the invention, the module comprising: a base structure defining a manifold; an inlet in the manifold, the inlet housing an impeller connected to drive a hydraulic pump; a plurality of substantially upright tube structures mounted in a spaced, side-by-side arrangement on the manifold for connection thereto, each tube having a series of apertures formed along a side thereof facing its adjacent tube such that flow between adjacent tubes causes a venturi effect such that water is drawn from the manifold through the apertures causing water to be drawn into the manifold through the inlet to drive the impeller; and a deck structure extending across the tops of the tube structures and supported by at least two tube structures.

The hydraulic pump may be used to drive a high pressure water pump.

Further aspects of the invention will be apparent from the description below. Brief description of the drawings

Figure 1 shows a plurality of SMEC tubes aligned in a sequence to form a barrage apparatus across the tidal flow; fig. 2 shows a side view of one SMEC barrel; fig. 3 shows a bird's eye view of one SMEC cartridge; fig. 4 shows a plurality of SMEC barrage modules placed end-to-end to form a barrage across a typical estuary or strait; fig. 5 shows a cross-sectional view of an SMEC barrage module; figure 6 shows a standard module of a SMEC barrage; fig. 7 shows a general view of an SMEC barrage in operation; figures 8, 9, 10, 11 and 12 show one SMEC barrage being constructed; figure 13 shows a ship lock incorporated into the SMEC barrage; and figure 14 shows a second embodiment of a module according to the invention. Mode(s) for carrying out the invention

The present invention is based on the technology broadly disclosed in WO 2008/015047 which describes an apparatus for generating electricity using the flow of tides, waves or currents in a body of water, the apparatus comprising: an arrangement of first and second conduits, each first conduit being provided with a series of apertures spaced along its length, and the first conduits being arranged relative to the second conduits such that a venturi is defined between the walls of adjacent first and second conduits in the vicinity of the apertures. A flow conduit is provided having an inlet and an outlet, with an impeller positioned in the flow conduit; and a generator is connected to the impeller. Water from the body of water may enter the flow conduit through the inlet, and the first pipes are connected to the outlet of the flow conduit such that the flow of water through the arrangement of first and second pipes causes the first pipes to act as venturi pumps, inducing flow from the interior of the first pipes through the apertures to draw water through the flow conduit and drive the impeller.

The term "lineage marine energy converter" (SMEC) is used to define this technology. The word "pedigree" indicates that energy is extracted from any water movement between these conduits regardless of the frequency of the incident energy. Most other wave energy devices rely on extracting energy by tuning the device to resonate at a frequency at which the energy density of its surrounding spectrum is expected to peak. In contrast, SMEC are "whole lineage". It works well even at zero frequency (i.e. tidal flow).

The basic principle of the invention is to align a series of SMEC modules across a estuary or straits to form a barrage. These SMEC modules are capable of generating electricity from the flow of tidal or current by driving an impeller unit via a venturi. A second embodiment of the present invention provides a platform for supporting a road or railway.

Fig. 1 shows a series of SMEC tubes 1 arranged across a tidal flow, the tubes may have open or closed tops. The fall 3 from the water level 5 at the surface of the water to the water level 7 inside the barrel is caused by the venturi effect. This causes a secondary flow 9 to flow out through the slots 11. This small pressure drop across a large number of venturi orifices results in a large volume, large cross-sectional area, low velocity secondary flow 13 through the manifold piping 15. The slow movement of the large body of water is fed by water flowing through the impeller through a shroud 17 of significantly smaller cross-sectional area to provide a higher local flow rate than the manifold. The total cross-sectional area of the slots 11, manifold piping 15 and shroud 17 is selected to increase the pressure drop and maximize power output according to bernoulli's theorem. This freedom of design allows the impeller to be optimized to operate with high efficiency and desirable stress levels.

FIG. 2 shows a side view of one SMEC barrage in operation; showing the direction of the tide 19. The physical presence of the SMEC barrage causes the upstream water surface level to rise in the manner of an arcuate wave 21. The bow wave is caused by the inability of water to flow through the SMEC tube via the slots due to the pressure differential. The resulting head difference 23 allows the conversion of potential energy to useful power above only the upper efficiency limit (known as the betz limit) of the means for extracting kinetic energy.

Increasing the physical length of the SMEC barrage maintains this bow wave effect by preventing bypass losses at the edge of the device (whereby the incident flow is diverted around the barrage rather than through it). Since the height of the bow wave is not linearly proportional to the length of the SMEC barrage, the quasi-constant energy loss at the device edge is amortized over the increased total energy output. Furthermore, installing a large SMEC barrage across the estuary from bank to bank or across straits from coast to coast will exhibit zero edge loss as bypass flow will be eliminated.

Fig. 3 shows a plurality of secondary flow paths 25 resulting from low pressure 27. The tidal flow 19 flows through the venturi 29 and exhibits a pressure drop according to Bernoulli's Theorem.

Figure 4 shows a section of a typical estuary or strait in which a barrage may be installed. The river bed has been prepared with a plurality of base platforms 10 on which SMEC barrage modules 12 can be placed in an end-to-end arrangement to form the barrage. The barrage may also incorporate a lock 14 to allow shipping. The length of the pipe or barrel of each SMEC module 12 is selected to be suitable for the depth of the foundation to be prepared below the water level for the purpose of maintaining the upper parts of the modules at substantially the same height.

The cross-sectional area of the water flow traversed by the SMEC barrage is not limited by structural length considerations, as is the case with underwater turbines, the size of which is limited by stresses in the blades or near the blade roots. The volume of secondary flow induced in the SMEC barrage can be made as large as desired by increasing the size of the infinitely scalable SMEC. Thus, the tidal flow power converted to electrical power by the SMEC array is also infinitely adjustable, the only constraint being the cross-sectional area of the tidal flow available to the barrage.

Fig. 5 shows a cross section of one SMEC barrage module 12 mounted on its base platform 10. Each platform is formed by piling a linear revetment 16 in the river or sea bed to accommodate the width of the base portion 18. The river bed or sea bed is contoured by dredging and/or dumping rubble 20 to prevent erosion of the river bed and to direct water flow through the SMEC module.

Each SMEC barrage module 12 is made of concrete and/or steel in a temporary or local dock to enable slip forming and other cost effective fabrication techniques to be utilized. The size of each module is typically chosen so that they are commonly towable by tugboats in the area of deployment.

The base portion 18 of the module 12 defines a manifold from which extends a hollow tube portion 22. An inlet in the base portion receives an impeller defining a turbine portion 24. The impeller is connected by a shaft 28 to a generator module 26 located on top of the module. When the module is in place, the tube portions 22 contain slots 30 located below the tidal water level. The impeller is driven by a flow of water directed through the manifold as a result of the water being forced through a series of venturi tubes defined by adjacent tube sections. The increased velocity water passing through the venturi draws water from the slots 30, which in turn draws water through the inlet and manifold. The impeller, in turn, drives an impeller shaft 28, which powers the generator 26.

In another embodiment of the invention, the impeller may drive a hydraulic pump. The hydraulic power converted from the secondary flow may be used to drive a hydraulic motor, which may be used to drive a machine or to generate electricity. Incorporating a hydraulic accumulator in the circuit allows for the storage of energy converted from the secondary flow. This energy can then be used when needed, thereby ensuring that the energy demand is not dependent on simultaneous power generation. The same adjustment effect can be achieved by connecting a high pressure water pump to the hydraulic pump. The pumped water may be used to fill an elevated tank. This water can be used to drive a turbine driven generator powered by hydrostatic pressure when required. In this way, the generator is only used when power is required and the tide and demand cycle may be completely decoupled.

A plurality of laid top sections 32 are positioned on top of the SMEC barrage module 12. Once the SMEC barrage modules are arranged end-to-end, they are connected to form a road or railway. These laid top sections 32 additionally serve to aid in the integrity of the structure. In further embodiments of the invention, these laid top sections may form large applications such as runways with terminal facilities. The airport may be located on a man-made island partially traversing estuaries or straits with its runway at right angles to the SMEC barrage.

Figure 6 shows the standard modules of one SMEC barrage 12. The height of these tubes 22 is chosen to suit the depth of the platform foundation (high water level in tidal zones) to be prepared below the water surface. Water flows from the venturi slots at the mid-chord of the tubes into the lower pressure region, causing a secondary flow through the manifold 18, impeller inlet 34 and impellers 36, which drives the generators 26.

Fig. 7 shows a general view of one SMEC barrage in operation, in which three modules 12a, 12b, 12c are shown. Downstream ecosystems are not severely affected; since the main effect of SMEC is a delay of only one time in the tidal cycle, the solid barrage changes the shape of the time profile of the tidal cycle.

Fig. 8, 9, 10, 11 and 12 show one SMEC dam being constructed. The profile of the river bed or sea bed is altered by dredging and/or dumping rock and the foundation platform is formed by sheet piling a plurality of linear revetments 16 in the river bed or sea bed as described above. The slots 30 of the SMEC barrage modules 12 are temporarily closed to form a buoyancy chamber having a manifold with closed ends. These modules are towed into position by a tug 38. Once the module is positioned above its revetment 16, the module is lowered into position by controlled flooding of the inlets controlled by appropriate valves. Alternatively, the slots 30 and impeller inlet 34 are unsealed to facilitate controlled flooding of the structure and lowering the module into position. The module is lowered into position between the revetment 16 of the pre-driven sheet piles. Once the module is seated on this basis, any gaps around or below the SMEC barrage module are closed with mud 40. These modules 12 need only be connected to each other at road or railway height. When several SMEC barrage modules 12 are in place, a profiled rock ramp 42 is prepared on each side by dumping rock.

Fig. 13 shows one ship lock 14 incorporated into the SMEC barrage to allow passage of shipping. The ship lock may incorporate a lift bridge, level swing bridge or overpass 44 in the road or railway. The lock gates 46 in the closed position may act to increase the flow rate and direct the flow through the SMEC barrage modules, resulting in enhanced power generation.

Fig. 14 shows another embodiment of the SMEC module in which the plurality of tubes 22a are truncated to end just above the normal high water level. The other tubes 22b extend to support the plate surface 32. The truncated tubes 22a allow the harmless passage of large waves (such as storm surge, tidal anomaly, storm surge and flood tide) over these tubes (but under the road), thereby limiting the loads imposed on the module and the upstream flooding effect that may be caused by the barrage-bound flow. SMEC barrages have the additional advantage of being less environmentally damaging. The SMEC barrage slightly modifies the upstream tidal cycle rather than stopping it completely by concentrating the water behind the containment walls; the method employs a conventional tidal barrage. Furthermore, SMEC barrages are also lighter and less expensive and can withstand the entire tidal range of overturning moments by allowing flow in both directions and allowing large waves to pass unobstructed.

Claims (15)

1. A module for forming a barrage across a body of water for generating electricity from the flow of tides or currents, the module comprising:

a base structure defining a manifold;

an inlet in the manifold, the inlet housing an impeller connected to drive a generator or a hydraulic pump;

a plurality of substantially upright tube structures mounted in a spaced, side-by-side arrangement on the manifold for connection thereto, each tube having a series of apertures formed along a side thereof facing its adjacent tube, such that flow between adjacent tubes causes a venturi effect whereby water is drawn from the manifold through the apertures causing water to be drawn into the manifold through the inlet to drive the impeller; and

a deck structure extending across the tops of the tube structures and supported by at least two tube structures.

2. The module of claim 1, wherein the deck structure comprises a roadway, railway, or aircraft landing structure.

3. A module as claimed in claim 1 or 2, wherein at least some of the tube formations terminate below the deck such that, in use, they lie above but close to a normally high water level.

4. A module as claimed in claim 1, including said generator, wherein the generator is located at or near the deck structure.

5. The module of claim 1, comprising said hydraulic pump, wherein the hydraulic pump is connected to a high pressure water pump.

6. A weir for generating electricity from the flow of tides or currents, comprising a plurality of modules as claimed in any one of claims 1 to 5.

7. A method of installing a barrage as claimed in claim 6 across a body of water for generating electricity from a flow of tidal or current, the method comprising:

preparing a series of foundation platforms across the bed of the body of water in a direction substantially perpendicular to the flow of the tide or current, each foundation platform providing a substantially flat base on which the base structure of one or more modules can be positioned; and is

A series of modules are positioned side-by-side on the platforms such that the base portion of each module rests on a platform and the deck structure of each module is at substantially the same elevation as the deck structure of its adjacent module.

8. The method of claim 7, wherein the barrage is installed across the entire width of the body of water.

9. The method of claim 8, comprising maintaining an upstream bow wave to allow conversion of potential energy beyond the Betz limit to electrical energy.

10. The method of claim 7, wherein each foundation platform is formed by a linear revetment positioned on the bed of the body of water, the method further comprising altering the profile of the bed adjacent each revetment by dredging and/or dumping material to match its shape.

11. The method of claim 7, wherein the base structure of each module is secured to the foundation platform by grouting.

12. The method of claim 7 including floating each module into position above its corresponding base platform and lowering it into position by controlled flooding of the module.

13. The method of claim 12, comprising temporarily closing the holes when the module is floated into place and then fully opening the holes once the module has been installed.

14. The method of claim 7, further comprising forming a lock between the two modules to allow the surface vessel to pass through the barrage.

15. The method of claim 7, wherein modules are selected from a group of modules having different deck heights above the base unit, the module being selected according to the depth of water in which it is to be positioned.