Field of the invention

The present invention relates to a device and method for construction of a whole or partial barrier between a first and a second body of water. Background of the invention

The global community is faced with major challenges as a result of climate change. There is wide political consensus that emission of fossil fuel must be reduced. Oil, gas and coal are limited resources. There is therefore a growing need for renewable and emission-free energy from, e.g. tidal water and waves. The climate changes result in melting of glaciers, leading to a rise in sea level. Increased sea temperature gives rise to greater volume in the bodies of water.

Climate researchers also predict more extreme weather with an increased risk of flooding. Existing flood protection, such as e.g. the Thames Barrier which protects London, and Holland's extensive system of dykes, requires new solutions. Tidal power stations in dams where the dam more or less shuts off an area of sea have the effect of reducing fluctuations in the sea level within the dam. They can therefore contribute to efficient flood protection in addition to providing renewable and environmentally friendly electric power.

WO-2005/017349 discloses a turbine for a tidal power station where the energy is utilised in both tidal directions.

WO-201 1/025387 discloses a turbine of this kind further developed for harnessing both wave power and tidal power.

Norwegian patent 320988 discloses a device and method for interconnecting and fixing prefabricated concrete structures for such power stations. US-2009/1 10484 describes a breakwater barrier system comprising a breakwater wall on a first surface of a floating concrete structure, a substantially watertight wave barrier wall, located at a distance from the breakwater wall on the second surface of the concrete structure, and an anchor for securing the concrete structure at a predetermined location. Summary of the invention

A general object of the invention is to provide an improved device and method for construction of a whole or partial barrier between a first and a second body of water.

The invention has been set forth in the claims. Brief description of the drawings

The invention will now be described in closer detail as a non-limiting example, illustrated by the attached drawings and explained by the following, detailed description. Wherever possible, identical or corresponding elements have been indicated by the same reference terms in the drawings.

Fig. 1 is a perspective view of an installation during building, where some central sections are already mounted while a tugboat is on the way with a new central section.

Fig. 2 illustrates a device for construction of a whole or partial barrier between a first and a second body of water.

Fig. 3 illustrates a central section with transport unit, ready for connection to already embedded central sections.

Fig. 4 illustrates a support leg in a horizontal position, thereby enabling it to be towed from building dock to assembly site. Fig. 5 illustrates further details of a central section and a corresponding transport unit.

Detailed description of the invention

Fig. 1 is a perspective and schematic view of an installation during building where some central sections are already mounted while a tugboat is on the way with a new central section.

Fig. 1 therefore illustrates steps carried out in the construction of a whole or partial barrier between a first and a second body of water. In this case the bodies of water consist in a sound between land areas, and the barrier is established between the land areas, across the sound or over parts of the sound. The method comprises firstly arranging a central section 13 on the surface of the water. In this case the central section is floating, and it is towed in prefabricated condition by a tugboat from a dock or the like to the construction site concerned.

The method further comprises providing support legs to support the central section relative to a fixed base, in this case the seabed. This and other aspects are further illustrated with reference to fig. 2, amongst others, below.

As can also be seen from fig. 1 , the method further comprises interconnecting the central section 13 with an additional number of central sections at the central sections' end walls, in order to form a continuous chain of central sections. In special versions turbines may be provided in through-flow openings in the central sections. The barrier can thereby represent an installation for harnessing tidal energy, since the turbines are driven by water which is naturally moved between the first and the second body of water as a result of tidal forces. Further aspects of the method and the device will now be described.

Fig. 2 is a schematic view of a device for construction of a whole or partial barrier between a first and a second body of water. The figure also illustrates aspects of a method for construction of a whole or partial barrier between a first and a second body of water. Fig. 2 illustrates a central section 13 floating on the water surface. On the left side of the central section 13 a support leg is illustrated already manoeuvred into position and attached to the central element 13. The right side of the figure is a schematic view of a situation where a corresponding support leg 22 is manoeuvred into position on the opposite side of the central section 13 and affixed thereto. The method for construction of a whole or partial barrier between a first and a second body of water therefore firstly comprises arranging the central section 13 on the water surface.

At least one pair of support legs are further provided to support the central section relative to a fixed base, illustrated as the seabed by the hatched area at the bottom of fig. 2. The method further comprises leading a number of projections, where one projection is provided on each support leg, diagonally upwards and inwards in respective openings in a lower area of the central section 13. The projections are then fixed to these openings.

The buoyancy for each support leg can be varied and controlled by filling a plurality of cavities or chambers in the support leg with air or water. These may comprise an upper chamber in the part of the support leg which is shown submerged, and a lower chamber 24 in the part of the support leg which protrudes slightly up from the surface in the illustrated example. In the whole of this description "upper chamber" refers to the chamber which is located in the highest position after the support leg is mounted, i.e. closest to the central section.

The upper chamber may, for example, be water-filled, while the lower chamber 24 is air-filled. This results in the position illustrated in fig. 2, where the support leg's upper end, where the projections are mounted, is positioned slightly below the surface, while the support leg's lower end, which comprises an anchoring device, protrudes slightly up from the surface.

By gradually pumping water into the lower chamber 24, and/or pumping water out of the upper chamber, and/or pumping air into the upper chamber, this enables the right support leg 22 to be manoeuvred into position in an easy and practical manner. In addition the option is given of tightening a winch line 29 by means of a winch (not illustrated, but it may be mounted on the central section 13, for example at the pump station 28), in order thereby to further facilitate the manoeuvring of the right support leg 22 into position.

Buoyancy means in the form of chambers in the support leg 22 permit easy manoeuvring and handling of the support leg when joining the support leg 22 and the central section 13. Furthermore, the need is avoided or reduced for powerful cranes or the like and heavy installation machinery during the joining operation. Fig. 3 illustrates a central section with transport unit, ready for connecting to already embedded central sections.

At 10 there is illustrated a number of central sections already mounted to one another, or alternatively a central section of a greater length. Here, the central section or central sections have already been provided with a number of support legs, which together form a tilted surface which leads flowing water upwards and inwards towards any through-flow openings in the central section(s), where a turbine or turbines may be mounted for harnessing the energy in flowing water.

In fig. 3 the central section 13 is being lifted by the transport unit 17. This is explained in more detail with reference to fig. 5 below. Fig. 4 illustrates a support leg 22 in the horizontal position in which it is transported from building dock to assembly site.

The lower part of the support leg (where "upper" herein refers to a higher position after the support leg is mounted, i.e. closest to the central section, while on the other hand "lower" refers to a lower position after the support leg is mounted, i.e. in the opposite end of the central section) comprises an anchoring device, illustrated as an example in the form of a suction anchor 26. The suction anchor has an open underside 27 which, by means of filling water in the additional, lower chamber 25 in the support leg 22, is gradually pushed down into the base, i.e. the seabed. Via a pipe/hose connection (not shown) to a vacuum pump, the internal pressure in the suction anchor may then be lowered. The external water pressure combined with tightening of the winch line will further press the lower end of the support leg 22 down into the seabed.

The support legs may further comprise one or more cast-in tubes 25, which can thus act as guide tubes for drilling holes for inserting strong safety bolts in solid rock. The support legs can then be securely grouted with pumped concrete through the tube or tubes 25. The support leg 22 may be provided at its left end with a towing fixture 18 mounted on the projections (or the protruding tongues) 19. The projections 19 may, for example, be expediently cut out of solid steel plates. A number of transverse reinforcing bars 20 on each projection provide good power transfer and a stiff connection between central section 13 and its cut-out, and the support legs, after concrete has been pumped in round the reinforcing bars 20.

The support leg 22 may have an internal, upper chamber comprised of the area between a surface 21 where the projection is provided and a partition wall 23 in the support leg 22. The support leg may also comprise a lower chamber 24 between partition wall 23 and suction anchor 26. Both these chambers advantageously have a pipe/hose connection up to pump station 28, for example arranged on the central section 13, thereby enabling an operator to here adjust the buoyancy on and along the support leg concerned.

Fig. 5 is a perspective view of a central section 13 and a transport unit 17 ready for insertion in the central section's horizontal openings 1 1. At 14 openings are shown through which turbines can be lowered after assembly is completed and the concrete in the central sections has set.

For the sake of simplicity the diagonal openings or cut-outs in the central section 13, for receiving and mounting of the support leg's projection, are not shown in figure 5, but it should be understood that the central section is also provided with these.

The transport unit 17, which is expediently welded together from steel plates, comprises three separate and closed chambers, contained in the transport unit's main part 17, together with the two protruding parts 15, 16. From each chamber pipes are run up to a non-illustrated control station at the top where an operator can pump water or air into or out of each chamber and thereby adjust both buoyancy and tilt of the transport unit.

On each end wall the central section 13 may be provided with protruding, cast-in steel beams 12. These may expediently have milled grooves in end members on strong channel beams, which in their opposite, cast-in member have holes or cutouts for a number of reinforcement rods which distribute the forces well into the centre of the concrete. The said grooves may be horizontal and designed so as to fit into opposite protruding teeth from corresponding steel beams on the opposite central section. A possible advantage of this is that in the few minutes when the tide turns, the fitters will be able to position the new central section at the correct height and lateral direction, whereupon, by means of welding and/or screw connection or in some other way, they can join the sections together so that the weight of the new section can be transferred to the old when the transport unit has to be released. Further connection is carried out by imbedding protruding reinforcing bars on both central sections and on the support feet when they are in position.

Further possible aspects of the invention will now be described. A device for construction of a whole or partial barrier between a first and a second body of water comprises, as indicated in the above, a central section 13 and at least one pair of support legs 22 arranged to support the central section relative to a fixed base.

The central section 13 is provided in a lower area with a number of openings, or cut-outs/cavities, and each support leg 22 is provided at an upper end with a number of projections adapted for attachment to respective openings in the central section. This is illustrated, for example, in fig. 2. The openings in the central section may expediently comprise diagonal cut-outs, or cavities, each with a cross section, for example circular, decreasing obliquely upwards towards the interior of the central section, and where the support leg's projection fits into its respective cut-out.

As illustrated particularly in fig. 1 , the device may further comprise an additional number of central sections 13, where the central sections are interconnected at their end walls in order to form a continuous chain of central sections. Support legs may be attached to all the central sections in the described fashion for anchoring to the base/the seabed. For this purpose each support leg is provided at a lower end with an anchoring device for attachment to the fixed base.

In order for the device, including the support legs, to constitute surfaces which form a whole or partial barrier for the water between the first and second body of water, the central section may comprise a first and a second end face, facing the first and second body of water respectively, and each support leg may comprise a surface extending along a whole length of a respective end face for the central section.

In some embodiments the support leg's surface may extend along the whole height of the support leg. In other embodiments the surface may be broken by openings where water can pass. As indicated earlier, each support leg may be arranged to have variable controllable buoyancy. This can be provided by a plurality of cavities in the support leg which are arranged to be filled with (or emptied of) air or water.

In some embodiments the central section also has variable, controllable buoyancy. This can be provided either by at least one cavity in the central section which is arranged to be filled with air or water, or by the use of a separate transport unit, illustrated by 17 in figures 3 and 5, arranged to be connected to the central section, where the transport unit comprises cavities which can be filled with air or water. The device may particularly expediently form part of an installation for harnessing tidal energy. In such embodiments the central section comprises a first and a second end face, facing the first and second body of water respectively, and in addition at least one through-flow opening between the first and second end face. In the central section a turbine may furthermore be provided which is driven by water flowing through the through-flow opening. In a special embodiment of this kind, as illustrated for example by further details in fig. 5, the central section may further comprise vertical passages 14 between an upper portion of the central section and a centre portion of the two through-flow openings provided, where the vertical passage forms a mounting channel for the turbine. The turbine may be arranged to be horizontally reversible in the central section, in order thereby to exploit both tide directions.

The invention may be particularly useful for anchoring and assembly of large prefabricated concrete sections at greater depths than those for which previously known methods are suited, such as the method described in Norwegian patent

320988. The invention may have special advantages during mounting and anchoring in loose seabed.

The support legs employed in the invention form an incline which leads waves and tidal water up and into any intake or passage in central sections containing one or more turbines. By means of these inclines tidal water in deeper locations may also be forced up and into the turbine(s).

The central sections are advantageously cast in reinforced concrete. They can be mass produced in dock and floated out of the building dock, preferably at high water. The central sections may be equipped with air-filled cavities and/or supplemented with a special transport unit 17 which provides sufficient buoyancy to permit the sections to be lifted free of the dock floor and subsequently towed in a partly submerged position to the assembly site.

When the new central section is in position, the buoyancy is adjusted to the correct height before the new concrete section is locked to the previously mounted section. Water is then admitted to the transport unit 17, so that the weight of the new section is transferred to the old section and its foundations. The transport unit 17 can then be towed back to the production site for reuse on the next section.

By means of the same method of production as for the main central sections, the support legs may be cast in reinforced concrete in the building dock and floated into position. They may be equipped with cavities which provide buoyancy for towing in a surface position. By means of a winch and pumping water in a controlled manner into the support legs' various buoyancy chambers, arranged at different positions along the length of the leg, the support legs can be manoeuvred into position. The support legs may advantageously be produced in different lengths and designs depending on the depth of the sea and bottom conditions where they are to be installed.

In order to ensure secure anchoring in loose seabed, support legs may

advantageously be employed where the outer/lower part of each support leg is provided in the form of a suction anchor. The lower part may have a box-shaped cross section without a bottom. When the outer/lower buoyancy tank in the feet is filled with sea water, the support legs are tilted downwards by their own weight so that a lower sharp edge of the said box-shaped part penetrates a distance down into the loose ground. Sea water can then be sucked out of the said chamber via a pipe/hose connection. The support leg may be held more securely in place by means of a winch and steel cord while the inner end is winched up. The water is then sucked out from the support leg's outer/lower chamber via a non-illustrated pipe/hose connection up to a vacuum pump. The water pressure outside the chamber and the winch will thereby cooperate by pressing the support leg's outer/lower end further down into the seabed.

At their opposite (i.e. upper) end the support legs have one or more protruding tongues or projections which fit into opposite openings in the central section. Both support leg and central section here may have protruding reinforcement bars with openings around which are filled with concrete when the leg concerned is in position. After the concrete has set, strong, rigid connections are obtained between support leg and central section.

With support legs of this kind on each side of the central section, firm anchoring to the bottom is provided which absorbs the powerful lateral forces from tide and waves as well as the weight which will be produced by the entire resulting concrete bridge with turbines and future traffic on the roof.

When the concrete binding the support legs and the central section together has set, this section can take over the load from the next new central concrete section. In this way the bridge connection can be built step by step in a rational manner out into the sea without the need for heavy crane vessels or any noticeable need for divers.

The final stage is the mounting of turbine(s) and other machinery, independently of the concrete work. The support feet are produced in different lengths to suit the depth of the sea where they are to be mounted. Thus an approximately equal and optimal tilt is achieved for the support legs independently of the depth of the sea.

The method and the device offer great flexibility with regard to such variations in sea depth while at the same time being time and cost-saving compared to previously known methods and devices. It should be understood that the above description is provided in the form of non- limiting, illustrative examples. Many variations and alternatives will immediately be apparent to those skilled in the art. The principle and scope of the invention are therefore defined by the following patent claims and their equivalents.