Field of the Invention

The present invention relates to water-retaining structures, and to related barrages and methods of retaining water.

Background to the Invention

Tidal energy systems offer the potential to generate electricity while avoiding disadvantages associated with using fossil fuels in generation. In order to increase the efficiency of tidal energy systems it is desirable to maximise the amount of water that flows through the turbines, so for systems that employ tidal storage a location that that has a large tidal range is preferred. Such locations are often exposed to the open sea, meaning that the tidal energy system requires protection to be installed for the turbines and associated tidal storage structures.

Example embodiments aim to address issues associated with the prior art, whether identified herein or otherwise.

Summary of the Invention

In one example embodiment there is provided a water-retaining structure for a tidal energy system, the water-retaining structure comprising a gateway and a moveable gate, wherein the movable gate is arrangeable in an open configuration to allow water to pass from one side of the structure to the other and a closed configuration to block water from passing from one side of the structure to the other through the gateway, and further comprising a wave retaining element above the movable gate, shaped to impede passage of waves outwardly over the structure and to allow relatively unimpeded passage of inwardly incident waves over the structure.

In one example embodiment, the wave retaining element presents a generally convex surface to inwardly incident waves. That is, to waves inwardly incident in a landward direction.

In one example embodiment, the wave retaining element presents a generally concave surface on its inward facing side. That is, to waves that approach in the seaward direction.

In one example embodiment, in cross section the retainer comprises a generally hooked profile, concave on its inward facing side. In one example embodiment, the wave retaining element extends upwardly above the water-retaining structure. In one embodiment, the wave retaining structure extends inwardly of the water-retaining structure. That is, the wave retaining structure extends in the landward direction.

In one example embodiment, the movable gate is rotatably mounted to move between the open configuration and the closed configuration.

In one example embodiment, the movable gate is mounted to rotate about a generally vertical axis.

In one example embodiment, the movable gate is mounted to rotate about a central axis.

In one example embodiment, the wave retaining element is moveable, arranged in use with relatively free inward movement over a working range of movement so that in use it moves downward through the working range under influence inwardly incident waves and upward within the working range to retain water on the inward side thereof in response to incident waves in the contrary direction.

In one example embodiment, the wave retaining element is moveable, mounted for rotation about a lower portion thereof.

In one example embodiment, the wave retaining element comprises the uppermost portion of the wave retaining structure.

In one example embodiment, there is provided a barrage for a tidal energy system, comprising a water-retaining structure as set out herein.

In one example embodiment, the barrage system comprises a plurality of moveable gates arranged below a common wave retaining element.

In one example embodiment, there is provided a method of retaining water on an inward side of a water-retaining structure of a tidal energy system that comprises a gateway with a moveable gate and a wave retaining element above the moveable gate, the method comprising: allowing inward movement of water through the gateway with the movable gate arranged in an open position; arranging the moveable gate in the gateway to block water from passing through the gateway; and impeding passage of waves outwardly over the structure and allowing relatively unimpeded passage of inwardly incident waves over the structure according to the shape of the wave retaining element. In one example embodiment, the step of arranging the moveable gateway to block water from passing through the gateway is performed to coincide with high tide at the tidal energy system.

In one example embodiment, the method is performed using a water-retaining structure as described herein, and/or with a tidal energy system comprising a barrage as described herein. According to the present invention there are provided an apparatus and method as set forth in the appended independent claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

Brief Introduction to the Drawings

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figure 1 shows a schematic plan view of a barrage system according to an example embodiment of the present invention;

Figure 2 shows a schematic front view of a plurality of water-retaining structures according to an example embodiment of the present invention arranged in a wave wall;

Figure 3 shows a schematic front view of a water-retaining structure according to an example embodiment of the present invention;

Figure 4 shows a schematic side view of the water-retaining structure of Figure 3;

Figure 5 shows schematic plan views of a horizontal section through the water-retaining structure of Figure 3, at the level of the moveable gate; and

Figure 6 shows example steps in a method of method of retaining water on an inward side of a water-retaining structure, according to an example embodiment.

Description of Example Embodiments Figure. 1 shows a schematic plan view of a tidal energy system according to an example embodiment of the present invention. The tidal energy system is for generating electrical energy from the tidal movement of sea water using barrages. Water is allowed to flow into storage basins B, which are also referred to as lagoons, as the tide rises, and allowed to flow from behind the barrages once the tide has gone out. Movement of water into and out of the storage basins B is used to drive turbines that are coupled to electrical generators. The tidal energy system of Figure 1 incorporates barrage between basins, and a seaward wave wall 1 that also comprises a water-retaining structure.

The water-retaining structures of the wave wall 1 are arranged to retain water from wave crests on an inward side thereof. In this way the wave crests can be used to increase the amount of water retained in the barrage system compared to that which would be possible in the absence of waves and wave valves, thereby increasing the amount of stored energy potential available for conversion to electrical energy. The water-retaining structures serve as the seaward portion of the barrage system, and as such are arranged to protect the turbines and other components of the barrage system from damage by storm swells etc.

The water-retaining structures 10 that make up the wave walls 1 are shown in more detail in Figures 2 to 5. The wave walls 1 are provided by a plurality of water-retaining structures 10 arranged next to one another. Providing the water-retaining structures 10 as individual, independently operating sections of the overall wave wall 1 enables the water- retaining structures 10 to be modularly applied to different barrage systems according to local coastal conditions, and to be operated and maintained efficiently over their operation lifetime. For example, the wave wall 1 shown in Figure 2 comprises nineteen water-retaining structures 10, each of 25m width to span a distance of 475m between sea walls 3 at each end thereof. In other example embodiments the water-retaining structures are provided in larger numbers, for example with one hundred water-retaining structures 10 arranged to span a distance of 2.5km.

In Figures 3 to 5 the operation of the water-retaining structures 10 are explained.

Figure 3 shows a schematic side view of a water-retaining structure 10. The water- retaining structure sits on the sea bed 2, and comprises a gateway 11 and a moveable gate 20. The gateway 11 is bounded, at its sides, by support pillars 12. Above the support pillars 12 and the moveable gate 20 is wave retaining element 30, also referred to as a wave catcher. The gateway 11 is bounded, at its upper side by the bottom of the wave retaining element 30, and its bottom side by a base set into the sea bed 2. The water-retaining structure 10 may be provided as a modular unit with support pillars 12 on either side of the gateway 11 , or with only one support pillar 12 so as to cooperate with one or more corresponding structures as part of a barrage, or other structures adjacent to the gateway 11 . The movable gate 20 is arrangeable in an open configuration to allow water to pass from one side of the water-retaining structure 10 to the other and a closed configuration to block water from passing from one side of the water-retaining structure 10 to the other through the gateway 11. For example, as the tide is incoming, the moveable gate 20 is opened to allow water to flow toward the storage basins B in a barrage system such as shown in Figure 1. When the maximum water level is reached, corresponding to high tide, the moveable gate 20 is closed, with the water levels on each side being equalised. The moveable gate 20 is of sufficient height to be at least as high as the maximum water level under normal tidal variation. in the embodiment of Figures 2 to 5 the moveable gate is 8m high above the sea bed 2.

The moveable gate 20 is rotatable between the open and closed configurations by virtue of a pivot or hinge 22. Figure 5 shows, in plan the position of the hinge 22 between the support pillars 12, and the rotational positions of the movable gate 20. The gate is shown in the closed position 20' aligned between the support pillars 12 and in the open position 20" rotated by ninety degrees to allow movement of water through the gateway 11 comprising the support pillars 12.

The wave retaining element 30 is shaped to impede passage of waves outwardly over the water-retaining structure 10 and to allow relatively unimpeded passage of inwardly incident waves over the water-retaining structure 10. In typical barrage systems, the seaward side is exposed to relatively large waves compared to the landward side. By matching the size and shape of wave retaining element 30 above the moveable gate to the waves typically incident thereon, from both the seaward side and the landward side, the water-retaining element enables additional head of water, above the level of high tide, to be retained.

The wave retaining element 30 extends in the inward direction, corresponding to the direction of approach of the larger waves incident on either of the sides of the water-retaining structure 10. This will generally be the landward direction, i.e. larger waves approach the wave retaining element 30 from the open sea than from the side of the water-retaining structure 10 which faces toward land.

The height of the wave retaining element 30 above the top of the moveable gate 20 is determined according to the expected amplitude of inwardly incident waves. In the example embodiment of Figures 2 to 5, the wave retaining element 30 is 2m higher than the top of the moveable gate 20.

An inwardly incident wave moving in the landward direction comprises a forward component of motion, which when incident on the wave retaining element, will carry some of the water from the crest of the inwardly incident wave over the inwardly extending part of the wave retaining element 30 . However, a relatively smaller wave, incident on the other side of the wave retaining element will be retained by the inwardly extending wave retaining element 30.

To improve retention of the waves by the wave retaining element 30, the wave retaining element 30 suitably extends both upwardly and inwardly to allow the crest of inwardly incident waves to wash over the top of the wave retaining element. In the example embodiment of Figures 2 to 5, as can be seen in the side sectional view of Figure 4, the wave retaining 30 presents a continuous, smooth upper surface. The wave retaining element presents a generally convex surface 36 to inwardly incident waves approaching in the landward direction and a generally concave surface 35 on its other side. The wave retaining element 30 suitably presents an upslope and then a downslope for the crest of an inwardly incident wave to wash over. On the other side, the wave retaining element 30 presents a surface that has a normal that extends back toward the direction of waves incident thereon, to reverse the direction of such waves, and thus impede passage of waves in this direction. In the embodiment of Figure 4 it can be seen that the normal extends downwardly, and that the surface is shaped to reverse the direction of movement of water that moves initially upwardly thereon.

In some embodiments, the wave retaining element may be moveable, for example by rotation about a lower portion thereof. The wave retaining element 30 may suitably be arranged in use with relatively free inward movement over a working range of movement so that in use it moves downward through the working range under influence inwardly incident waves, and upward within the working range to retain water from wave crests on the inward side thereof in response to incident waves in the contrary direction.

In order to further enhance the operation of the water-retaining structures 10 it is desirable for the waves incident thereon to be of suitable amplitude, which can be engineered to occur more frequently by use of wave drivers 31-34 shown in Figure 1. The wave drivers 31-34 comprise suitably sized and positioned on the sea bed 2. The wave drivers 31-34 increase the height of inwardly incident waves by providing an effective reduction in depth that increases toward the barrage. Ridges of the wave drivers 31-34 project from the sea floor, with valleys there-between. The valleys successively narrow toward the wave wall 1 thereby forcing moving waves to increase in effective height.

A further enhancement is provided by the arrangement if Figure 1 in which a wave funnelling region 40 in the form of a sea wall that presents a relatively wide reception portion to receive inwardly incident waves, and relatively narrow funnelling portion at the approach to the wave wall 1 is shown. From Figure 1 the operation of the funnelling region 40 can be ascertained, serving to increase the effective depth of waves as they move through a narrowing channel.

Figure 6 shows steps in a method according to an example embodiment. The method is useful with barrages for tidal energy systems as described herein. The method results in retention of water from wave crests on an inward side of a water-retaining structure of a tidal energy system that comprises a gateway with a moveable gate and a wave retaining element above the moveable gate. At step S101 the method comprises allowing inward movement of water through the gateway with the movable gate arranged in an open position. At step S102, when high tide has been reached, the moveable gate is arranged in the gateway, to block water from passing through the gateway. At step S103, the shape of the wave retaining element impedes passage of waves outwardly over the structure while allowing relatively unimpeded passage of inwardly incident waves over the structure.

The methods and apparatus described herein may increase efficiency in tidal barrage systems and this enhance the environmental and other benefits associated with generation of electrical energy by capturing energy from tidal sources.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.