Tidal Weir

Abstract

a plurality of spaced apart tower bodies, a plurality of barriers between the tower bodies for controlling the flow of water through the weir, and one or more turbine devices, the tower bodies comprising at least a first tower body, a second tower body, and a third tower body, the first tower body being disposed between the second tower body and the third tower body and housing one or more of the turbines, one or more first barriers being provided between the first tower body and the second tower body, and one or more second barriers being provided between the first tower body and the third tower body, the barriers being comprised of one or more first barriers and one or more second barriers. 1. A tidal weir configured such that when the one or more first barriers and the one or more second barriers are in a first arrangement, a first flow path is defined through the weir from a first side of the weir to a second side of the weir, and when the one or more first barriers and the one or more second barriers are in a second arrangement, a second flow path is defined through the weir from the second side of the weir to the first side of the weir, water flowing through the first flow path and the second flow path flows in the same direction through one or more turbines housed within the first tower body, and one or more of the barriers comprise a water-impermeable flexible membrane body, a buoyancy member, and one or more tethers.

Description

[Technical Field]

[0001] This disclosure relates to tidal weirs, and more particularly to tidal weirs that can generate electricity from both phases of bidirectional flow using unidirectional turbine generators. [Background technology]

[0002] Conventional tidal weirs (or barriers) used for coastal protection, built on the same principles as gravity dams, are common in the Netherlands, for example. They are also used to generate electricity as the tide passes through turbines, also like conventional dams, but this is a less common practice. A well-known example is located across the mouth of the River Rance in France. However, some commentators consider them to be uneconomical and environmentally destructive.

[0003] The present disclosure relates to a method that achieves the same objectives as these conventional tidal technologies but is much lighter, less complex, less costly, and significantly easier and less expensive to install and maintain. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a simple, environmentally friendly, cost-effective and unobtrusive tidal weir that significantly reduces marine civil engineering work, can be quickly installed and can be easily configured to provide full bidirectional or ebb tide power generation, flood mitigation, coastal protection, as well as recreation and transportation facilities. [Means for solving the problem]

[0005] According to the present invention, in a first aspect, there is provided a system comprising a plurality of spaced apart tower bodies, a plurality of barriers between the tower bodies for controlling the flow of water through a weir, and one or more turbine devices, the tower bodies comprising at least a first tower body, a second tower body, and a third tower body, the first tower body being disposed between the second tower body and the third tower body and housing one or more of the turbines, one or more first barriers being provided between the first tower body and the second tower body, and one or more second barriers being provided between the first tower body and the third tower body, the barriers comprising one or more first barriers and A tidal weir is provided, the tidal weir being configured such that when the one or more second barriers are in a first configuration, a first flow path is defined through the weir from a first side of the weir to a second side of the weir, and when the one or more first barriers and the one or more second barriers are in a second configuration, a second flow path is defined through the weir from the second side of the weir to the first side of the weir, water flowing through the first flow path and the second flow path flows in the same direction through one or more turbines housed within the first tower body, and one or more of the barriers comprises a water-impermeable flexible membrane body, a buoyancy member, and one or more tethers.

[0006] The one or more first barriers located between the first and second towers preferably comprise a single two-way barrier comprising a water-impermeable flexible membrane, a buoyant member, and one or more tethers.

[0007] A unique passive control is achieved by providing a bidirectional buoyant barrier in the intake channel defined between the first and second towers, which reverses direction in response to changing flow direction without the need for external control.

[0008] The one or more second barriers disposed between the first and third towers preferably comprise a pair of one-way barriers, each of which may comprise a water-impermeable flexible membrane, a buoyant member, and one or more tethers.

[0009] Preferably, the tower body further comprises a fourth tower body disposed on an opposite side of the third tower body from the first tower body, and one or more third barriers provided between the third tower body and the fourth tower body, the third tower body housing one or more further turbine devices, the barriers configured such that when the one or more third barriers are in a first configuration, a third flow path is defined through the weir from a first side of the weir to a second side of the weir, and when the one or more third barriers are in a second configuration, a fourth flow path is defined through the weir from the second side of the weir to the first side of the weir, and water flowing through the third flow path and the fourth flow path flows in the same direction through one or more turbines housed within the third tower body.

[0010] The one or more third barriers located between the first and second towers preferably comprise a single two-way barrier comprising a water-impermeable flexible membrane, a buoyant member, and one or more tethers.

[0011] If a pair of barriers is provided between two of the towers, one of the barriers will be on either side of the turbine or turbines. If a single barrier is provided, it will be movable between a first position on one side of the turbine or turbines and a second position on the opposite side of the turbine or turbines.

[0012] Tidal weirs may also be permanently used across tidal estuaries and in tidal lagoons as self-contained, closed, enclosed structures extending out from the shoreline or located offshore for purposes including, but not limited to, power generation, flood prevention and mitigation, creating recreational facilities for water sports, or improving coastal erosion protection.

[0013] Where appropriate, bridge structures may be supported above the high water mark of the tidal barrier to allow access for purposes such as, but not limited to, maintenance, walking or cycling, and rail and / or vehicular traffic and cable laying such as power transmission or fiber optics.

[0014] The towers may be substantially rectangular or diamond-shaped in plan view. The towers may be arranged in linear or curved arrays between which currents are constrained from bypassing the array. The opposing faces of each pair of adjacent towers preferably have substantially parallel, flat, smooth surfaces.

[0015] As discussed, one or more of the barriers comprise a water-impermeable flexible membrane, a buoyant member, and one or more tethers. In use, the membrane can have a lower edge portion and an upper edge portion, the lower edge portion may be fixed relative to the bottom of the body of water in which the weir is installed, the membrane and buoyant member may be attached to each other at the upper edge portion, and the tether may have a first end portion attached to the buoyant member and / or to the membrane at the upper edge portion, and a second end portion attached to the anchor body.

[0016] The buoyant member may include a manifold that allows water to be introduced into the interior of the buoyant member, and the manifold may be connected to a pump.

[0017] The barrier with buoyancy members, as further disclosed, provides a buoyancy-assisted weir that can be deployed in a variety of configurations for the function of a tidal weir used for ebb tide or bidirectional current power generation, as well as for any or all of the following additional functions, including, but not limited to, flood prevention and mitigation, creating recreational facilities for water sports, or improving coastal erosion protection.

[0018] The towers may be fabricated from any suitable material, including, but not limited to, fabricated steel, masonry, or cast concrete construction. The towers may be independent of one another, and the weir is formed by providing a suitable array of towers, followed by providing appropriate barriers between the towers. The towers may comprise prefabricated submersible units, which can be installed in place as separate elements independent of one another, before installing cost-effective buoyant weirs between them.

[0019] By housing the turbines in spaced-apart towers and providing one or more barriers with buoyant weirs between the towers, it is possible to provide a very cost-effective weir that can be installed at a fraction of the cost of prior art configurations.

[0020] An array of unidirectional turbine units may be arranged transversely at the bottom of each tower, and the turbine units may be arranged substantially perpendicular to the direction of the tidal current.

[0021] Each turbine device preferably comprises: a focusing section connected to a first end of the mixing chamber such that a venturi is defined between the end of the focusing section and the mixing chamber; a diffuser section connected to a second end of the mixing chamber, the diffuser configured such that, in use, the pressure at an outlet of the diffuser is greater than the pressure at the venturi; at least a portion of a tube disposed within the focusing section, the tube defining an annulus between the tube and the focusing section to form a first flow path and the tube defining a second flow path within the tube; and a turbine connectable to an electric generator, the turbine disposed within the tube.

[0022] Further preferred features are set out in the dependent claims.

[0023] The invention will now be described, by way of example, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic plan view of a tidal weir according to a first configuration in an ebb tide arrangement. [Figure 2] FIG. 2 shows the configuration of FIG. 1 in a reversed inward flow configuration. [Figure 3] FIG. 2 is a schematic plan view of one module of the tidal weir of FIG. 1 in an ebb tide configuration. [Figure 4] FIG. 4 is a schematic plan view of the module of FIG. 3 in a reverse flow configuration. [Figure 5] FIG. 1 is an elevation view of the elevated tidal weir supporting the bridge structure. [Figure 6] 2 is a plan view and elevation view of a tower suitable for use with the tidal weir of FIG. 1. [Figure 7] 1. FIG. 10 is a plan view and elevation view of an alternative tower body suitable for use with the tidal weir of FIG. 1, with optional installation aids. [Figure 8] FIG. 2 is a side view of an exemplary buoyant weir suitable for use as a barrier in the tidal weir of FIG. 1. [Figure 9] FIG. 5 is a schematic plan view of a module similar to that shown in FIG. 4 but with a modified barrier configuration. [Figure 10] FIG. 2 is a side elevation view of a two-way weir suitable for use as a barrier in the tidal weir of FIG. 1. [Figure 11] 1A-1C show exemplary linearly arranged one-way and two-way buoyant weir membranes in deployed configurations. [Figure 12] FIG. 12 shows a curved, trapezoidal tower with the same membrane shape as in FIG. 11. DETAILED DESCRIPTION OF THE INVENTION

[0025] The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0026] Figures 1 and 2 show schematic plan views of an exemplary configuration of a tidal barrage 1 installed in a tidal body of water in an ebb tide configuration and an inflow configuration, respectively. Figures 3 and 4 show idealized schematic plan views of one preferred power generating module of the barrage of Figures 1 and 2, also in an ebb tide configuration and an inflow configuration.

[0027] The tidal weir (or barrage) 1 generally comprises a plurality of spaced towers 2, a plurality of barriers 3 for controlling the flow of water through the weir (or barrage) between the towers, and one or more turbine units 4 (see FIG. 6). The towers are comprised of at least a first tower 2a, a second tower 2b, and a third tower 2c, with the first tower 2a positioned between the second tower 2b and the third tower 2c and housing one or more of the turbine units 4. One or more first barriers 3a are provided between the first tower 2a and the second tower 2b. One or more second barriers 3b are provided between the first tower 2a and the third tower 2c. The barriers 3 are configured such that when the one or more first barriers 3a and the one or more second barriers 3b are in a first configuration, a first flow path is defined through the weir from a first side of the weir to a second side of the weir (as indicated by the flow arrows), as shown in Figures 1 and 3, and when the one or more first barriers 3a and the one or more second barriers 3b are in a second configuration, a second flow path is defined through the weir from a second side of the weir to a first side of the weir (also indicated by the flow arrows), as shown in Figures 2 and 4. As clearly shown, in this configuration, water flowing through the first and second flow paths flows in the same direction through one or more turbines housed in the first tower body.

[0028] In this configuration, the tower bodies preferably further include a fourth tower body 2d disposed on the opposite side of the third tower body 2c from the first tower body 2a, and one or more third barriers 3c disposed between the third tower body 2c and the fourth tower body 2d. The third tower body 2c houses one or more additional turbine devices, and the barriers 3c are configured such that when the one or more third barriers 3c are in a first configuration, a third flow path is defined through the weir from a first side of the weir to a second side of the weir (again as indicated by the flow arrows), as shown in Figures 1 and 3, and when the one or more third barriers 3c are in a second configuration, a fourth flow path is defined through the weir from the second side of the weir to the first side of the weir (again as indicated by the flow arrows), as shown in Figures 2 and 4. As also clearly shown, the water flowing through the third and fourth flow paths flows in the same direction through one or more turbines housed in a third tower.

[0029] The first and third tower bodies 2a and 2c, the one or more turbine devices 4 housed therein, and the one or more first, second, and third barriers 3a, 3b, and 3c therebetween can be considered to define a power generation module, as depicted schematically in Figures 3 and 4, and the weir preferably comprises a plurality of power generation modules. The one or more turbine devices 4 housed in the first tower body 2a preferably face one or more turbines housed in the third tower body 2c of the power generation module, as shown. This allows the flows through the first and third tower bodies 2a and 2c to merge in the region between the first and third tower bodies and exit the weir between the first and third tower bodies 2a and 2c, as clearly shown in Figures 3 and 4.

[0030] As can be seen in Figures 1 and 2, the power generation modules may be arranged next to each other, with the second tower 2b housing one or more turbines facing away from the turbine or turbines housed in the first tower 2a, and / or the fourth tower 2d housing one or more turbines facing away from the turbine or turbines housed in the third tower 2c.

[0031] There may be sections of the weir provided with modules that do not include turbine devices 4 and that function simply to block flow around the weir 1, and this may be of any suitable structure. There may also be openings to allow vessels to pass through the weir, which are closed by one or more barriers 3. As shown in Figures 1 and 2, for example, a two-way opening 5 may be provided to allow vessels to pass through the barrier 3 at high tide. The barriers 3 are in place during tidal power generation and are opened or removed to leave an unobstructed passageway for vessels.

[0032] The tidal weir of Figures 1 and 2 comprises, purely by way of non-limiting example, five power generating modules and a navigation channel 5.

[0033] The barriers 3 in Figures 1-4 are shown schematically and can take any suitable known form, including, but not limited to, sluice gates or caissons. However, as discussed in detail below, they preferably comprise buoyant barriers. Regardless of their specific form, one or more or all of the first barrier(s) 3a, second barrier(s) 3b, and third barrier(s) 3c may comprise a pair of barriers, with one barrier on either side of one or more turbines. This is the case in the configurations of Figures 3 and 4, where only the operating barriers are shown. Alternatively, one or more or all of the first barrier(s) 3a, second barrier(s) 3b, and third barrier(s) 3c may comprise a single barrier that is movable between a first position on one side of one or more turbines and a second position on the opposite side of one or more turbines, such that flow is appropriately controlled in the manner depicted in Figures 3 and 4.

[0034] The shape of the tower bodies 2 is not particularly limited. They preferably extend along longitudinal axes in plan view, and the longitudinal axes are preferably arranged generally parallel to one another and / or in a direction of tidal current that is substantially aligned with the direction of the tidal current. In this configuration, as clearly shown, the tower bodies 2 are parallel and substantially aligned with the direction of the tidal current. The tower bodies may be substantially rectangular in plan view, as shown. Adjacent tower bodies may have substantially planar, opposing, parallel faces, also as shown.

[0035] The flow axis of the turbine device or devices 4 is preferably arranged at an angle to the tidal current, and they are preferably arranged substantially perpendicular to the longitudinal axis, as in the present configuration.

[0036] Figure 5 shows an elevation view of the tidal weir of Figures 1 and 2, with tower 2 having the optional additional function of a bridge pier. Also shown illustratively is how channel 5 can optionally be located in deeper water. Bridge 6 can serve any of the purposes discussed above. If desired, a higher bridge height above the channel can be accommodated, as illustratively shown.

[0037] A preferred turbine unit and an exemplary construction of a tower housing with the turbine unit will now be discussed with reference to FIGS.

[0038] Preferably, each turbine device 4 comprises a focusing section 4a connected to a first end of a mixing chamber 4b, the focusing section 4a defining a venturi between the end of the focusing section 4a and the mixing chamber 4b, and a diffuser section 4c connected to a second end of the mixing chamber 4b, the diffuser 4c configured such that, in use, the pressure at the outlet of the diffuser is greater than the pressure at the venturi. More preferably, at least a portion of a tube (not shown) is disposed within the focusing section 4a, the tube defining an annulus between the tube and the focusing section to form a first flow path, the tube defining a second flow path within the tube, and a turbine connectable to a generator disposed within the tube. The turbine device may be constructed in accordance with the teachings of EP 2864627, the contents of which are incorporated herein by reference. However, it should be noted that the turbine device 4 may take any suitable alternative form.

[0039] The turbine units 4 are preferably provided in an array and may be configured as desired. The turbine units 4 may be provided in several rows, for example, as shown. One or more of the turbine units 4 in any array may include a turbine unit barrier (not shown) for selectively blocking flow through the turbine unit. Any suitable barrier capable of blocking flow may be implemented for such purposes.

[0040] With particular reference to FIG. 6 , plan and elevation views are shown of an exemplary tower body comprising a bank of turbine units 4, each configured in accordance with the above considerations. One preferred option is to integrally cast the focusing section 4 a and the diffuser section 4 c into the tower body. Another preferred option is to provide a vertical wet recovery facility in the access area above the waterline of the power generation section, including a turbine and generator housed within the housing, and associated equipment including mechanical power takeoff. In this case, a conventional sluice gate or similar conventional device may be installed upstream of the power generation section across the turbine units to prevent large flows from bypassing other turbine units in the same turbine unit bank. Additionally, a second sluice gate may be installed downstream of the power generation section if dry access to the power generation section housing is required.

[0041] In one preferred option, the tower body 2 is fabricated off-site in a dry dock or other suitable location and is designed to have a substantially watertight submersible interior compartment so that the entire tower body is buoyant and can be floated into position using towing and arresting tugs in the conventional manner before being flooded and lowered into position.

[0042] 7 discloses optional additional installation aids that may be integral with the tower body. These may be omitted. If included, they may be employed alone or in combination with one another, as will be readily apparent to those skilled in the art.

[0043] For example, during off-site fabrication of the tower body, one or more scour skirts 7 may be attached to its base to assist in achieving rapid positional stability during installation. Depending on the conditions of the estuary bottom, the weight of the tower bodies may be utilized to achieve rapid partial penetration of the scour skirts 7 by flooding the tower bodies to increase their own weight and thereby provide temporary positional stability of the tower body within the estuary bottom.

[0044] Additionally, vertical pile guide tubes 8 may be provided. These may be left open at the tower base, in which case piles may be driven through the guide tubes into the estuary floor to fix the tower base in place. The number of piles driven per tower will depend on several site-specific conditions, including, but not limited to, prevailing environmental conditions such as water depth, wind and wave reach, estuary floor configuration, and pile size, as will be readily understood by those skilled in the art. In the preferred case, at least three piles per tower will be driven, as this provides a convenient mechanism for maintaining the tower base in a vertical position during installation.

[0045] Further penetration of the scour skirt 7 into the seabed can be achieved by conventional techniques, injecting water beneath the tower body through suitable water injection conduits 9 at the base of the scour skirt 7 inside its periphery, and pumping the resulting slurry out through selected members of a set of discharge conduits 10. This sole use of discharge pumping, with the water injection conduits 9 closed, can also be utilized to reduce the pressure of the water beneath the tower body, thereby substantially increasing the tower's dead weight and providing further control of penetration into the estuary floor. Installation can be completed by first injecting grout into the annular space between the inner surface of the longitudinal guide pipe 7 and the outer surface of the pile, allowing the grout to solidify and secure the tower body base to the pile, and then secondly injecting grout through the water injection conduits beneath the invert at the tower body base, inside the periphery of the scour skirt 7, until all the water has been expelled from this space through the discharge conduits and undiluted grout begins to flow out through the discharge conduits.

[0046] Also disclosed in Figure 7 is a preferred option in which each scour skirt 7 is compartmentalized, allowing selective leveling of the tower base during installation by pumping water into one compartment through selected water inlet conduits 9 while pumping water out of another compartment through selected water outlet conduits 10. Figure 7 illustrates three compartments and three longeron guide tubes, merely as one example of many possible arrangements, which allow for maintaining vertical trim about both horizontal axes of the tower base during installation; however, this process may also be aided by selectively driving one or more piles into corresponding longeron guide tubes to keep such points on the tower base vertically fixed while subsequently adjusting the height of one or more other points.

[0047] Figure 7 also discloses a further optional feature of the scour skirt arrangement that may be employed when a seepage barrier has already been pre-installed in the estuary bottom at the same location. A gap 11 across the base allows the tower base to be installed across the seepage barrier without physical interference. With the aid of a suitably positioned water injection conduit 9, sand and silt can be flushed aside from the gap, which can then be sealed against the seepage barrier by grout injection through the same water injection conduit 9.

[0048] As discussed above, it is preferred that one or more of the barriers 3 comprise buoyant barriers. Such buoyant barriers may be arranged in accordance with the disclosure in UK Patent Application No. 2102604.2, the contents of which are incorporated herein. Preferably, the barriers in Figures 3 and 4 are all buoyant barriers.

[0049] An exemplary buoyant barrier is shown in Figure 8 and comprises a water-impermeable flexible membrane 12, a buoyant member 13, and a tether 14. Preferably, as shown, in use, membrane 12 comprises a lower edge portion 12a and an upper edge portion 12b, with lower edge portion 12a secured to the bottom 15 of the body of water 16 in which weir 1 is installed, membrane 12 and buoyant member 13 attached to each other at upper edge portion 12b, and tether 14 comprises a first end portion 14b attached to buoyant member 13 and / or to membrane 12 at upper edge portion 12b, and a second end portion 14b attached to anchor body 17. Water levels are indicated at 16a and 16b. An optional seepage barrier is indicated at 18. Seepage barrier 18 may optionally also function as anchor body 17, depending on the configuration. In an alternative configuration, for example, the lower edge portion 12a of the membrane may be provided against the bottom and ballasted or otherwise secured.

[0050] The buoyant member 13 preferably includes a manifold (not shown) that allows water to be introduced into the interior of the buoyant member 13. The manifold is preferably connected to a pump.

[0051] A buoyant barrier is a very cost effective solution. Furthermore, the buoyant barrier can be raised or lowered as desired by introducing or expelling water from the buoyant member 13. If required, a groove 21 or other feature may be provided to receive the buoyant member in the lowered position.

[0052] As a non-limiting example only, a tidal weir according to the configuration of FIGS. 1 and 2 with one or more buoyant barriers in the navigation channel may be configured to prevent flooding due to high waves as follows: Discharge of water from buoyant element 13 raises barrier 3 in navigation channel 5. As the water level rises above normal high tide, the buoyant element will continue to rise along with it. A specific safety limit for rising water levels upstream of the estuary may be established. In such a case, a sluice gate blocking flow through the turbine device can be closed to prevent further rise in the water level upstream of the estuary. Buoyant element 13 continues to rise, increasing the head difference across the buoyant barrier and preventing further flooding, eventually reaching a height that can be specified at the design stage as sufficient to protect coastal areas upstream of the estuary from even the highest projected water levels under storm surges and sea level rise due to global warming. In the event of an extreme flood beyond what was specified in the design, the geometry of the buoyant barrier would, from a theoretical standpoint, ultimately prevent the buoyant member from rising any further, allowing water to continue flowing over the buoyant member as a weir and upstream into the river, just as any other type of barrier would be unable to cope with unpredictable sea level rise caused by, for example, a large tsunami.

[0053] As discussed further below, particularly with reference to Figures 9 and 10, a two-way buoyant barrier may be implemented.

[0054] Figure 9 shows an exemplary configuration of one power generation module of a tidal weir. This configuration differs from that discussed with reference to Figures 3 and 4 in that the barrier 3 consists of a one-way barrier and a two-way barrier. In the depicted configuration, two-way barriers 3a and 3c are provided in the intake channel. The two-way barriers 3a and 3c are passive and reverse direction in response to changes in flow direction without external control. The two one-way barriers 3b in the central outlet channel can operate under any circumstances by partially submerging the inactive buoyancy elements 13 during power generation periods, causing them to sink, and then draining them back into their active state during the tidal cycle. Alternatively, the inactive barriers can operate passively if they automatically sink to the seabed under the pressure of the tidal currents over them. The extent to which this passive operation is effective will depend on the specific circumstances of the project.

[0055] It should be noted that alternative combinations of one-way and two-way buoyant barriers, and various combinations of buoyant and non-buoyant barriers are possible. Numerous suitable configurations will be readily apparent to those skilled in the art. The invention is not limited in this respect.

[0056] In any of the configurations described, the inlet channel may be wider than the central outlet channel, or vice versa.

[0057] When considering barriers, these may be all conventional, all buoyant, or hybrid arrangements may be employed. For example, the inlet may be equipped with a passive two-way buoyant weir, and the outlet may be equipped with a conventional barrier of any desired form. Many different arrangements will be readily contemplated by those skilled in the art.

[0058] Figure 10 shows a side elevation view of a bidirectional buoyant barrier of the type disclosed in UK Patent Application No. 2102604.2. Figure 10 illustrates the complete translation of the buoyant barrier as the tide reverses. This view represents an end elevation rather than a cross section, and the buoyant weir / barrier extends between two of the towers 2 in the configuration depicted. As indicated by the right-hand arrow, the acting flow is from right to left in Figure 10, and solid line detail shows the acting positions of the weir components. Dashed line detail shows the positions of these components when a flow reversal occurs.

[0059] The membrane 12 is attached to the tower wall above the anchor on the vertical centerline v. The edges of the membrane 12 fold against the wall, allowing the buoyant members 13 to move freely as the water level and flow direction change. Thus, the membrane 12 forms a slack B at each end of the buoyant members, extending a short distance downstream of the buoyant members 13. Note that the top level of the membrane 12 at slack B never drops below the top of the buoyant members 13 at any point, and instead of being dragged along the surface of the end wall 2, it folds away from it to minimize frictional damage to the membrane 12. Note also that the membrane 12 is held against the end wall by water pressure and rises above the high water mark to minimize seepage losses. The flexible membrane 12 has slots 21 to allow the flow to reach the turbine unit 4.

[0060] 11 shows the deployed configuration of an exemplary flexible membrane 12 intended for bidirectional operation between turbine unit concentrators in two adjacent parallel towers 2. The location of slots 14 is shown in the section of the membrane that collapses vertically against the parallel faces of the adjacent towers. Also shown is the deployed configuration of one of the four immediately adjacent one-way barriers that does not require a slot 14.

[0061] As will be apparent from the discussion herein, a single power generating module comprises a single central upstream section flanked by two downstream sections shared with adjacent modules.

[0062] The central upstream section preferably includes a single bidirectional buoyant weir with a membrane centrally moored to the estuary floor. This single bidirectional buoyant weir automatically adjusts whenever the tidal current reverses. Excessive seepage below the membrane, which could cause head loss and / or downstream ground uplift, is prevented or sufficiently mitigated by either or both of the central seepage barrier 18 and / or a sufficiently long seepage path below the membrane.

[0063] Each of the two downstream sections preferably includes two one-way buoyant weirs, the upstream of which is constantly active in response to the tide to maintain a head differential between the upstream and downstream sides of the tidal weir. The downstream buoyant weir is inactive and is always either actively submerged by partial flooding or passively submerged by downstream flow overflow. Excessive seepage flow and any resulting downstream ground heave is preferably prevented from bypassing each of the four one-way buoyant barriers in each power generation module by equipping the underside of the tower with a scour skirt as described above during construction, and then by preferentially ensuring that dimension "x" in Figure 11 (the length of the membrane that remains in contact with the estuary bottom) is sufficient to ensure a seepage path long enough to reduce seepage to an acceptably small amount, or by installing seepage barriers at both ends of the tower that also function as anchor bodies for the membrane, if necessary.

[0064] It should also be noted that, as a matter of detailed design, a particular tidal weir installation may require that the level of rock throw be selected for all or part of the plan footprint of the weir depending on environmental conditions and other design factors. This may be selected, for example, to mitigate local scour at the weir inlet or outlet, or in any event, to help mitigate the susceptibility of that area to downstream river bottom uplift.

[0065] Figure 12 shows the same deployed configuration of an exemplary flexible membrane 12 intended for unidirectional operation between the diffusers of two adjacent parallel towers 2 in a curved arrangement. Figure 12 also shows a preferred trapezoidal planar shape of the towers to achieve the curved configuration of the tidal weir while maintaining the opposing parallel faces of the adjacent towers 2.

[0066] It should be noted that the overall arrangement of the tidal weir 1, for example as shown in Figures 1 and 2 and configured according to any of the principles discussed above, allows for the achievement of the following desirable design results:

[0067] The natural current velocity and volumetric flow profile at each location along the array across the estuary can be effectively maintained, minimizing any environmental disturbance to the overall seabed morphology. This is possible because the number and size of turbine units in each tower can be adapted to the natural flow velocity and volume passing through each module's location on the weir. For example, in Figure 1, the fourth module from the left is located in a deeper channel, which is assumed to carry a larger volume of water than the other modules would need to pass through to maintain optimal performance across all modules while maintaining the original flow profile throughout the array. As a result, this module is designed to be longer than the others to accommodate more and / or larger turbine units.

[0068] UK Patent Application No. 2102604.2 discloses that, to a first approximation, the displacement of the buoyant element of a buoyant weir / barrier (which is a function of diameter) is approximately equal to the weight of the water supported behind the portion of the membrane vertically above the downstream waterline with a void below it. The smaller dead load of the buoyant element itself and the dead load of the membrane are secondary downward forces that react to the buoyancy. This is essentially a very light-weight, low-cost alternative to solid structural seawall alternatives such as rockfill embankments, or to structural dam barriers designed to resist the maximum overturning moment that may be exerted by the head difference between the water upstream and downstream of the barrier. Longer arrays result in a larger capital cost differential, favoring weirs with buoyant barriers as described herein. Furthermore, as water depth increases, the increase in the size of the buoyant weir's floating body required to achieve the same head difference is very minimal, commensurate with the negligible additional wet weight of the longer flexible membrane required. The cost of a buoyant weir to achieve any given head difference follows a first-order approximation and is therefore independent of water depth. In stark contrast, the cross-sectional area of ​​any structural barrier, such as a gravity dam, increases proportionally with a factor that approximates the square of the water depth, so the capital cost advantage of a buoyant weir increases with increasing water depth.

[0069] Turbine devices in the form disclosed herein provide a fish-friendly technology that allows for approximately 80% of the flow bypassing the turbine to be included in any throughflow. As much as 20% of the flow through the turbine can be screened with much smaller, less costly screens than those required by alternative technologies. These screens can be easily cleaned with mechanical devices such as brushes or water jets, or more simply, by short bursts of powered turbine reverse thrust during low tide. Any debris thus removed can continue through the turbine device in the 80% throughflow.

[0070] Although the tidal weir has been described with reference to being installed across a tidal estuary, it could also be installed in other bodies of water, for example, across a unidirectional flow in a large river, or to generate power only during the ebb tide of a tidal current. Also, where significant tidal currents occur in very shallow water, perhaps even exposing the estuary floor at low tide, this shallow water depth could limit the maximum diameter of any renewable energy generation devices, necessitating a large number of such devices, possibly requiring a longer array than can reasonably be accommodated within the width of the estuary. Excavating a trench along the array to accommodate larger diameter devices would be unsatisfactory because such a trench would be prone to silting and could lead to concentrating all of the larger generators in deeper water, dramatically changing the natural distribution of velocity profiles across the array with environmentally damaging consequences. In such cases, the disclosed configuration allows for the deployment of multiple power generation devices to match the natural flow pattern, regardless of the available length of the tidal barrier array.

[0071] As used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps, or integers are included. The term is not to be interpreted as excluding the presence of other features, steps, or components.

[0072] The features disclosed in the foregoing description or the following claims or the accompanying drawings, whether expressed in their detailed form or in terms of means for performing a disclosed function or a method or process for achieving a disclosed result, may be utilized individually or in any combination of such features to realize the invention in diverse forms thereof.

[0073] While specific exemplary embodiments of the present invention have been described, the appended claims are not intended to be limited to these embodiments. The claims are to be interpreted literally, operatively, and / or to encompass equivalents. Those skilled in the art will readily appreciate numerous alternative configurations within the scope of the claims.

Claims

1. A plurality of tower bodies arranged at intervals; a plurality of barriers between the tower bodies for controlling the flow of water through the weir; one or more turbine devices; The towers include at least a first tower, a second tower, and a third tower; the first tower is disposed between the second tower and the third tower and houses one or more of the turbine units; one or more first barriers are provided between the first tower body and the second tower body, and one or more second barriers are provided between the first tower body and the third tower body; the barriers are configured such that, when the one or more first barriers and the one or more second barriers are in a first configuration, a first flow path is defined through the weir from a first side of the weir to a second side of the weir, and when the one or more first barriers and the one or more second barriers are in a second configuration, a second flow path is defined through the weir from the second side of the weir to the first side of the weir, wherein water flowing through the first flow path and the second flow path flows in the same direction through the one or more turbines housed within the first tower body; one or more of the barriers comprises a water-impermeable flexible membrane, a buoyant member, and one or more tethers; Tidal weir.

2. 10. The tidal weir of claim 1, wherein the one or more first barriers disposed between the first tower and the second tower comprise a single two-way barrier comprising a water-impermeable flexible membrane, a buoyant member, and one or more tethers.

3. 3. A tidal weir as claimed in claim 1 or 2, wherein the one or more second barriers provided between the first tower and the third tower comprise a pair of one-way barriers.

4. 4. The tidal weir of claim 3, wherein each of the second barriers comprises a water-impermeable flexible membrane, a buoyant member, and one or more tethers.

5. 5. The tidal weir of claim 1, further comprising a fourth tower located on an opposite side of the third tower from the first tower, and one or more third barriers provided between the third tower and the fourth tower, the third tower housing one or more further turbine devices, the barriers configured such that when the one or more third barriers are in a first configuration, a third flow path is defined through the weir from a first side of the weir to a second side of the weir, and when the one or more third barriers are in a second configuration, a fourth flow path is defined through the weir from the second side of the weir to the first side of the weir, and water flowing through the third flow path and the fourth flow path flows in the same direction through the one or more turbines housed within the third tower.

6. 6. The tidal weir of claim 5, wherein the one or more third barriers disposed between the first tower and the second tower comprise a single two-way barrier comprising a water-impermeable flexible membrane, a buoyant member, and one or more tethers.

7. 7. A tidal weir as claimed in claim 5 or 6, wherein the one or more turbines housed on the first tower face the one or more turbines housed on the third tower.

8. 8. A tidal weir as claimed in claim 7, wherein the second tower houses one or more turbines facing away from the one or more turbines housed in the first tower, and / or the fourth tower houses one or more turbines facing away from the one or more turbines housed in the third tower.

9. 9. A tidal weir as claimed in any one of claims 5 to 8, wherein the first tower and the third tower, the one or more turbine devices housed therein, and the one or more first, second and third barriers define a power generation module, and the weir comprises a plurality of the power generation modules arranged adjacent to one another.

10. A tidal weir according to any one of claims 1 to 9, wherein the tower body extends along a longitudinal axis when viewed in plan.

11. 11. A tidal weir according to claim 10, wherein the longitudinal axes are arranged generally parallel to one another and / or generally in the direction of the tidal current.

12. 12. A tidal weir according to claim 10 or 11, wherein the flow axis of the one or more turbine devices is substantially perpendicular to the longitudinal axis.

13. A tidal weir according to any one of claims 1 to 12, wherein the tower body is substantially rectangular in plan view.

14. A tidal weir according to any one of claims 1 to 13, wherein adjacent towers have substantially planar, opposing, parallel faces.

15. 15. A tidal weir as described in any one of claims 1 to 14, wherein, in use, the membrane body has a lower edge portion and an upper edge portion, the lower edge portion being fixed relative to the bottom of the body of water in which the weir is installed, the membrane body and the buoyant member being attached to each other at the upper edge portion, and each of the one or more tethers having a first end portion attached to the buoyant member and / or the membrane body at the upper edge portion, and a second end portion attached to an anchor body.

16. 16. A tidal weir as claimed in any one of claims 1 to 15, wherein the buoyant member is provided with a manifold that allows water to be introduced into and / or discharged from the interior of the buoyant member.

17. 17. The tidal weir of claim 16, wherein the manifold is connected to a pump.

18. each of the one or more turbine devices; a focusing section connected to a first end of a mixing chamber such that a venturi is defined between the end of the focusing section and the mixing chamber; a diffuser section connected to a second end of the mixing chamber, the diffuser section configured such that, in use, the pressure at an outlet of the diffuser is greater than the pressure at the venturi; at least a portion of a tube disposed in the focusing section, the tube defining an annulus between the tube and the focusing section to form a first flow path, the tube defining a second flow path therein; and A tidal weir as claimed in any one of claims 1 to 17, comprising a turbine connected to an electric generator, located within the tube.

19. 19. A tidal weir according to any one of claims 1 to 18, wherein each tower houses an array of turbine units.

20. 18. The tidal weir of claim 17, wherein one or more of the turbine units includes a turbine unit barrier for selectively blocking flow through the turbine unit.

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