NO320938B1 - Device for founding an installation on a seabed as well as a method for installing the device - Google Patents

Description

The invention relates to an anchorage for a pile to a seabed, in particular for a device for producing electrical energy from sea and river currents. Furthermore, the invention relates to a method for anchoring a pile.

Research and development on tidal power plants or facilities for the production of electrical energy has been ongoing for many decades. The advantages of tidal systems include, for example, that compared to wind turbines, they are predictable and little dependent on the weather. Nevertheless, very few facilities have been built despite the fact that there are very large amounts of energy in tidal currents worldwide. The reason is mainly of an economic and/or environmental nature. These and other reasons have led to the development of facilities that are entirely located under the seabed. These facilities are built up of modules placed on a foundation on the seabed.

However, it is a challenge to install a solid foundation at the right angle under the sea surface in an economical way, because the bottom conditions can be difficult and variable, and because the modules to be founded can have significant dimensions. If necessary, the foundation must be placed in flowing bodies of water, and in some cases installed relatively deep. The foundation is exposed to significant mechanical loads from the flowing water masses and from the turbine they are intended to carry, and these loads can be fluctuating and create inherent oscillations in the construction. The foundations must be able to be installed quickly because the installation work in many cases must take place at the change of tide so that the current in the area is not so strong that it hinders the work.

In the past, little technology has been developed in this area because facilities for the production of energy from flowing bodies of water, placed on a foundation, and which are placed entirely under water, have not been widespread, and are of recent date.

Installation of underwater power plants has in most cases previously necessitated difficult, extensive and expensive diving work.

An example of such a modular tidal system is described in patent application NO 2001 0737, Hammerfest Strøm. This facility comprises a foundation placed on the seabed and one or more modules placed on the foundation. The modules can include a turbine, generator for electrical power, gears, and various electrical components. These turbines are attached to foundations which may include columns or piles.

It is difficult to achieve an anchorage on a seabed in a durable and economical way, especially in difficult bottom conditions. Masses of water flowing around constructions of this type easily create inherent oscillations in the construction, which places great demands on the foundation. It is also a challenge to get such foundations, piles or tower pipes placed at the right angle. Constructions that do not go over water are beneficial in order to reduce disturbance and slowing down of the water flow. Slowing down and disturbances in the water flow can adversely affect the turbine.

US 4,102,147 discloses an adjustable guide jig to ensure that piles are driven at a correct angle into a seabed. After a pile has been driven into the seabed, the jig is removed and used again to drive a new pile.

It is an aim of the present invention to simplify the installation of foundations for components for facilities that are entirely placed under water. The invention can of course also be used as a foundation for the installation of modules that protrude above water.

This is achieved with the present invention as stated in the independent claims.

The present invention provides a construction that can be founded in a simple and economical way in different bottom conditions, as well as a method for installing the construction on the bottom. It is an object of the invention to provide a construction which simplifies the maintenance and replacement of components.

The foundation is specially adapted for a propeller turbine where the blades are pitch-regulated to be able to rotate the blades at least 180°, preferably in connection with a change of current direction. Thus, that structure can be mounted in a locked position on a supporting structure (does not need to be rotated, unlike a windmill).

The supporting structure or foundation may comprise a cable gate to which the transmission cable is attached to avoid fatigue failure due to the forces of the water flow.

The foundation preferably comprises an anchoring pile or a tower pipe. In one embodiment, this can be driven into the bottom. A reinforcing pipe with formwork can be placed around the anchor pile and be filled with concrete, and a support pile can support the house and be fixed in the anchor pile to anchor the house to the bottom.

The described components can be assembled as modules to facilitate installation and maintenance. During installation, the house with the turbine attached will normally represent one module and the foundation one or more other modules. In one embodiment, the foundation comprises the previously mentioned anchoring pile, reinforcement pipe with formwork and bearing pile as separate modules.

The advantages of modular construction are significantly lower construction costs, possibilities for step-by-step expansion, and easier decommissioning.

In a method for installing the device according to the invention, a step-by-step installation is permitted, and in this way, installation is made possible despite large forces caused by water currents acting on the structure.

A foundation according to the invention is intended to be lowered onto a seabed from a vessel. The foundation comprises an outer pipe which, after completion of the foundation, rests on the seabed. An inner tube is installed inside the outer tube. In an alternative embodiment, the inner pipe is installed after the outer pipe is placed on the seabed. The angle of the inner pipe in relation to the outer pipe and thereby the rest of the foundation and the bottom can be adjusted with a device for this purpose, so that the subsequent tower pipe or pile can be placed vertically or at another desired angle. The angle adjustment can take place by holding the lower end of the inner tube in place, and adjusting the upper end of the inner tube with a suitable mechanism for this. Examples of such mechanisms may include manually or mechanically operated drive screws, racks or hydraulic cylinders. The mechanism preferably allows adjustment about two axes, so that the angle of the inner tube can be adjusted freely.

In one embodiment, the outer tube is mounted to box-shaped elements by means of trusses or the like. The boxes can be made of a heavy material, but are preferably hollow and filled with weight material during installation. The mutual distance between the boxes is chosen in relation to the assumed load, so that the foundation's "footprint" is sufficient to create the desired stability. After adjusting the inner pipe in relation to the outer pipe, the cavity between these can be filled with concrete so that the pipes are stabilized in relation to each other. The diameter of the outer pipe in relation to the inner pipe is adapted so that a desired adjustment interval is achieved in relation to the angle between the pipes and so that the space can be easily filled with concrete or other suitable filling material.

After the foundation, a tower pipe or pile is inserted adapted for mounting, for example, a turbine with housing and generator as described. The tower pipe preferably comprises guide cones which ensure that the tower pipe is centered in the inner pipe and is aligned parallel to this. The steering cones are placed around the part of the tower tube that is adapted to go into the inner tube, and are positioned so that steering is facilitated, while also ensuring that these can take up the torque applied to the tower tube. The tower pipe can further comprise one or more wedges which can enter one or more slits in the inner pipe for correct orientation of the tower pipe, preferably in relation to a current direction of flowing tides. Consequently, the inner tube should also be able to be adjusted about its longitudinal axis in relation to this. The slot should be open at one end with an opening that is significantly wider than the wedge, and taper downwards to facilitate the insertion of the tower tube and the wedge. After alignment, the space between the tower pipe and the inner pipe can be cemented, or the tower pipe can be fixed in some other way.

Brief description of the attached figures:

Fig. 1a, 1b are respectively a top and a side view of a foundation according to an embodiment of the invention; Fig. 2a-2c is a side view in which an installation sequence is illustrated for the embodiment shown in Fig. 1, from left to right; Fig. 3a-3c show two further steps of the installation sequence from fig. 2, where fig. 3b is a top view of Fig. 3a; Fig. 4a-4c show the two further steps in the installation sequence from fig. 2 and fig. 3 where fig. 4b is a top view of Fig. 4a; Fig.5a and 5b show the last two steps of the installation sequence from fig. 2, fig. 3 and fig. 4; Fig. 6 is a side view of a tidal system mounted on a pile and a foundation according to the invention; Fig. 7a-7c is a side view of an installation sequence of another embodiment of the invention;

Fig 8a-8g show a further three steps of the installation sequence from fig. 7; and

Fig 9 shows an alternative embodiment of the installation shown in fig. 7 and 8.

In the following, the invention will be described with an exemplary embodiment. Figure 1 shows a foundation according to an embodiment of the invention. The foundation is designed to be lowered onto the seabed from a vessel. The foundation is seen respectively from above and from the side and comprises an outer pipe (1) which is connected by means of trusses or the like to two box-shaped elements (2). The boxes can be made of a heavy material, but are preferably hollow and filled with weight material during installation. An inner tube (3) is installed in the outer tube (1). The angle of the inner tube (3) in relation to the outer tube (1) and thereby the rest of the foundation can be adjusted with a screw device as shown in the picture, with hydraulic cylinders, racks, drive screws or in some other way. Figure 2 shows three steps during installation of the foundation with outer pipe (1), inner pipe (3) and box-shaped elements (2). The steps show from left to right the sinking of the foundation and filling of the foundation boxes with weight material in the box-shaped elements (2), for example stone, using a suitable vessel, and the foundation fully installed on the bottom. Figure 3 shows three sketches where, figure 3a is a side view of a foundation placed on a seabed, and where it appears that this can be placed at an oblique angle for subsequent adjustment. Fig. 3b is a top view of fig. 3a and shows how the angle of the foundation's inner tube (3) is adjusted using screws, hydraulic pistons/cylinders or equivalent (4), schematically shown as screws. The embodiment shown shows a diver adjusting screws with a steering wheel manually, but the adjustment could well have taken place automatically with actuators well known in the field. When the inner tube (3) is in a vertical position, this can be locked by cementing the cavity between the inner tube (3) and the outer tube (1) using a hose from the surface (5) as shown in fig. 3c. During installation of the foundation, it is likely that this will be left at an angle in relation to a horizontal direction. Consequently, the outer tube (3) is not placed in a vertical position. It is therefore necessary to be able to adjust the angle described above. Figure 4 shows how the tower pipe is installed. Three sketches appear there. fig 4a shows a side view of how the tower pipe (6) is positioned over the foundation's inner pipe (3). In most cases, this will most easily be done by establishing a guide wire between the surface and the foundation along which the tower pipe is guided down (not shown in the figure). The tower pipe is equipped with two or more centering cones (7) on the part of the tower pipe that must enter the foundation's inner pipe (3). These must ensure that the tower pipe (6) achieves the same vertical angle as the foundation's inner pipe (3).

Considering the turbine that will later be mounted on the tower pipe (6), the tower pipe (6) must be installed with a given orientation in relation to the direction of the water flow. The inner tube (3) is therefore equipped with an orientation slot (8) as shown in fig. 4b which is a top view of fig. 4a.

The location of this is determined after the direction of the water flow has been observed and is used to mount an orientation wedge (9) on the tower pipe (6) as shown in fig 4c. When lowering the tower tube (6), this orientation wedge will hit the edge of the inner tube. When this happens, the tower tube (6) is turned until the orientation wedge (9) slides into the orientation slot (8), and the tower tube (6) can be lowered to its final position. At this stage, the tower tube (6) is in the correct position both in terms of vertical angle and orientation, and the space between the tower tube (6) and the inner tube (3) can be cemented. Figure 5 shows the installation of the cable pipe (10) and the retracting of the cable. The cable pipe (10) is attached to the tower pipe (6) and can be hinged as shown in the figure. The cable to land can be installed in this pipe either by pulling it into the pipe, as shown in the figure, or by dividing the cable pipe and hinged it, and that the cable can thus be inserted into the cable pipe. The cable will normally have several functions integrated, such as power conductors, signal lines and any hydraulic/pneumatic lines. When the cable has been installed in the cable duct, it is suspended so that the connections to the nacelle are accessible above the cable duct. Fig 6 shows a lift-induced propeller turbine (1t) as an example of an element, in the form of a module for generating power from flowing water masses, which can be mounted on a foundation according to the invention. The module includes a turbine (1t) with turbine blades. The blades are pitch-regulated to be able to rotate at least 180 <0> in connection with a change of current direction and are mounted on a waterproof capsule or housing (2t) with equipment to convert the turbine's rotation into electrical power, including a generator, possibly a gear and control system.

As the turbine blades can be rotated as described, the construction shown can be mounted in a locked position on the supporting structure or foundation (does not need to be rotated, unlike a windmill).

A support structure (3t) carrying the turbine (1t) and the capsule (2t) may also comprise a cableway to which a transmission cable (4t) is attached, to avoid fatigue failure due to the forces of the water flow. The transmission cable (4t) for the generated power runs from the electric generator, through the watertight capsule, and to a land plant (5t). The land plant (5t) transforms the generated power before it is phased into an existing power grid.

The installation of the device according to another embodiment of the invention is shown in fig. 7 and fig. 8. The installation is shown to be carried out step by step in steps (a) to (g). Steps (a), (b), (c) and (d) in Fig. 7 show that an anchoring pile or an anchoring pipe (11) is first driven down into the bottom masses. On top of this, a combined formwork and reinforcement pipe (12) is installed. The formwork (15) (shown as a cone) can be made of various materials, including fabric which takes on a conical shape when filled with concrete (later in the installation sequence). If the bottom masses are unstable with regard to washing out, this can be remedied by placing a stone/gravel filling (13) around the edge of the formwork (15). The supporting foundation for turbine (1) and capsule (2) shown in fig. 6 is installed in the anchoring stake (11) which is driven into the bottom, and oriented in relation to the direction of the current. Orientation can take place as indicated in figures 4a, 4b and 4c by mounting an orientation wedge (9) on the tower pipe (6) as shown in figure 4c. When lowering the tower tube (6), this orientation wedge will hit the edge of the inner tube. When this happens, the tower tube (6) is turned until the orientation wedge (9) slides into the orientation slot (8), and the tower tube (6) can be lowered to its final position Steps (e), (f) and (g) in fig. 8 shows that the voids between the anchor pile (6) and the reinforcement pipe (12), in the formwork (15) and between the support pile (6) and the reinforcement pipe (12) are filled with concrete. To ensure that the tower tube stands at the correct angle, this can be adjusted in one embodiment as indicated in fig. 3a, 3b and 3c. The adjustment must take place before the tower pipe is cemented. The hinged cable gate (17) is then released, so that the lower part rotates and falls to the bottom.

Figure 9 shows a simple embodiment where an outer pipe is driven down into a seabed, and a tower pipe (6) with centering cones (7) is cemented into the outer pipe.

Claims (9)

1. Anchoring for anchoring a pile (6) to a seabed, with a foundation comprising an outer tube (1) and an inner tube (3) placed inside the outer tube (1), where the lower end of the pile (6) is adapted for placement in the inner tube (3) and where the outer tube (1) is firmly connected to the seabed, and where an adjustment device (4) can adjust an angle between the inner tube (3) and the outer tube (1) characterized in that: the lower end of the pile (6) for placement in the inner tube (3), and the inner tube (3), comprises a wedge (9) and groove (8) for engagement with each other for orientation of the pile (6) along the pile's (6 ) longitudinal axis in relation to the foundation. 2. Anchorage for anchoring a pile (6) according to claim 1, where a space between the outer pipe (1) and the inner pipe (3) is adapted to be cemented when the anchorage is placed on the seabed. 3. Anchorage for anchoring a pile (6) according to claim 1, where the outer pipe (1) is attached to boxes (2), and where the boxes (2) are adapted for filling in mass after placement on the seabed. 4. Anchoring for anchoring a pile (6) according to claim 1, where the pile includes two or more centering cones (7) on the part of the pile which is adapted to enter the inner tube (3) to center the pile in the inner tube (3) and to facilitate the insertion of the pile (6) therein. 5. Anchoring for anchoring a pile (6) according to claim 1, where the inner pipe (3) consists of an anchoring pile (11) which is driven into the seabed and where the outer pipe (1) consists of a reinforcement pipe (12), where a formwork (15) is placed around the anchor pile (12) and is filled with concrete, and where the pile (6) is fixed in the anchor pile (12). 6. Anchorage for anchoring a pile (6) according to claim 1, where the pile (6) is adapted to support a housing (2t) with an axial turbine (1t), the pile (6) and the housing (2t) constitute modules, and the housing (2t) is adapted for a fixed connection with the pile (6), so that the housing (2t) cannot rotate in relation to the seabed. 7. Anchoring for anchoring a pile (6) according to claim 1, comprising an anchoring pile (11) and a combined formwork (15) and reinforcement tube (12), where the formwork (15) can be made of different materials, including fabric that gets a conical shape when filled with concrete. 8. Anchorage for anchoring a pile (6) according to claim 1, comprising a cable gate (17) to which a transmission cable (4t) is attached to avoid fatigue failure due to forces applied by the water flow, and the transmission cable (4t) for the generated power from the house and the turbine goes from an electric generator through the house (2t) and to a land plant (5t). 9. Procedure for anchoring with an anchor for a pile (6) according to claim 1, characterized by the following steps: placing the foundation comprising the outer tube (1) and the inner tube (3) located inside the outer tube (1), on a seabed; adjust an angle between the inner tube (3) and the outer tube (1) with the adjusting device (4); and place the lower end of the pile (6) in the inner tube (3) by turning the pile (6) until the wedge (9) engages with the groove (8).