NO316980B1 - Device for installing modules for a plant for the production of energy from streams in water bodies, an anchoring, as well as a method for installing the device. - Google Patents

Description

The invention relates to a device for controlling modules for underwater installations that produce electrical energy from flowing water masses. Furthermore, the invention includes a method for installing such modules. 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 located entirely below sea level. These facilities are built up of modules placed on a foundation on the seabed.

However, it is a challenge to assemble these modules under the sea surface in an economical way, because the modules can have significant dimensions and because they must be placed in flowing water masses, and because in some cases they are installed relatively deep.

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

An example of such a modular tidal system is described in patent application NO20010737, 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.

The reason why one wants to place facilities of this type entirely under water is that facilities that go above the surface include structures that cause the hydrodynamic forces to impose significant mechanical stresses on the structure. Furthermore, it is difficult to achieve an anchorage in the bottom in a durable and economical way, especially in difficult bottom conditions. Masses of water flowing around constructions of this type also easily create self-oscillations in the construction, which can eventually cause fatigue failure. Corrosion is also a problem, both in the splash zone, in the transition between water and air, and in places with high mechanical stresses. Furthermore, constructions that go up to or above the sea surface create an obstacle for shipping, and are otherwise unsightly in nature. 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.

It is an aim of the present invention to simplify the installation, maintenance and replacement of components for facilities that are entirely placed under water. The invention can of course also be used for the installation of modules underwater, although new modules placed on the structure will be able to protrude above water.

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

The invention is described for the installation of a horizontal-axis turbine, but can also be used for a vertical-axis turbine. The installation method according to the present invention has important advantages. A modular system that is entirely submerged does not represent visual pollution or limitations for shipping. An installation method that allows step-by-step installation enables installation despite large forces caused by the water flow. Such a system enables simple and efficient repair and maintenance operations.

The device and the method are particularly adapted for installations that include a turbine that resembles a windmill and that is placed entirely under water.

Such facilities comprise at least one module in the form of a house anchored to the bottom with a foundation or a supporting structure. The support structure normally also includes a cable tray to which a power transmission cable is attached to avoid fatigue failure due to the forces of the water flow. The foundation preferably comprises an anchoring pile which is driven into the bottom, or which is otherwise fixed in it.

The described components are 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. The advantages of modular construction are significantly lower construction costs, possibilities for step-by-step development, and easier dismantling.

It is the composition or assembly of these components and modules that the present invention aims to simplify.

Repair and maintenance of a module can be done by taking the module to the surface with the help of the present invention so that the work can be carried out dry in a workshop.

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

During installation, the house with the turbine attached will normally represent one module and the foundation one or more other modules.

A transmission cable for the generated power runs from the electric generator, through the house, which is normally a watertight capsule, and to an onshore plant for bringing power ashore.

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

This description does not cover the installation of the supporting structure itself, but assumes that one has been established in accordance with the requirements for verticality and orientation that will apply.

The device is adapted for setting a module on a foundation, where the foundation is placed on the seabed. The foundation is typically a tower tube and modules are typically a capsule or a house with the necessary components for energy production. The device comprises an area adapted for joining with the module. This area includes, for example, a normal flange for a bolted connection. In this case, the modules have corresponding flanges. However, it would be an advantage if the joining could be controlled automatically, and this could take place with a remote-controlled engagement device which, for example, comprises remote-controlled engagement pawls that engage with corresponding recesses in, for example, a conical tube on the module. The conical tube can then be adapted to engage a matching funnel-shaped hole in the foundation.

The surface vessel includes at least one winch which is used to hoist the module with and possibly tighten the guide wires.

Receiver elements with respective locking devices are located at the joint area of the foundation. These receiving elements are adapted to receive guide posts adapted to be lowered into the receiving elements to be locked in them with the locking devices. These too can, in an alternative embodiment, be controlled automatically with a remote-controlled engagement device which, for example, includes remote-controlled engagement pawls that engage with corresponding recesses in the guide posts. The receiver elements can be tubular and are attached to the foundation at the joining area.

At least two guide wires run between the surface vessel and the guide posts, and at least two guide rods are placed on the module at a distance adapted to

the location of the receiver elements. The guide tunnels are adapted for entry of the guide wires and for entry onto the guide posts, and are preferably equipped with an extended lower end which facilitates entry onto the guide posts. The guide tunnels are attached to the module in such a way that they are adapted to the location of the guide posts when these are attached to the receiver elements on the foundation.

A hoist wire extending between the module and the winch, mounted on the surface vessel for raising and lowering the module 2, is releasably attached to the module in an otherwise known manner. In one embodiment, the release of the hoist wire can be controlled remotely.

The locking devices for the receiver elements may comprise engagement means which automatically engage with the guide posts and lock them to the receiver elements. The engagement means may comprise spring-loaded pawls which slide into engagement with recesses when the guide posts are in place.

The remote control of the various intervention devices can take place via a cable from the surface vessel or in another way known in the field.

A method for controlling one or more modules for a foundation placed on a seabed for an undersea plant for the production of energy from currents in bodies of water with the described device can include placing a vessel that carries the module over the foundation. The entire steering and assembly should take place during the tide change so that this can take place when there is the least possible current. The present invention has therefore been developed so that this assembly can take place in such a short period of time that the module can be assembled before the current becomes too strong.

The guide wires are threaded through the guide tunnels placed on the module and the guide posts with the guide wires are lowered from the vessel down to the foundation. The guide posts are threaded into the receiving elements on the foundation and locked to the receiving elements with the locking devices. The guide wires are then tightened between the foundation and the vessel, for example with a winch placed on the vessel. The module is then hoisted down along the guide wires with the hoisting wire and the winch. The conical tube enters the foundation and the guide posts enter the guide tunnels on the module. The module is then attached to the foundation with the fixing device, for example by means of piles on the foundation engaging with recesses on the module. During an elevation of the module, this process is reversed. When the assembly is complete, the hoisting wire and guide wires are detached from the module and the foundation, and the assembly is finished.

The cable for transmitting power from the module in the case where this includes a

generator, can take place with an underwater coupler that automatically engages with a corresponding coupler mounted on the foundation when the module is placed, or the module can have a cable that is long enough for the connection to take place at the surface.

Brief description of the attached figures:

Fig. 1 shows a side view of an example of an installation that can be installed with a device and a method according to the invention where the various components or modules of the installation are clearly visible; Fig. 2 shows a partially cut side view of an example of a generator module with a nacelle that can be installed with a device according to the invention; Fig. 3 shows three steps of an installation sequence; Fig. 4 shows two steps of the installation sequence indicating the installation of the shore power cable; Fig. 5, 6 and 7 show different steps in the installation of a module according to the invention, where the components of the installation device appear; and Fig. 8 and 9 show a module and a barge that can be used in connection with the invention.

In the following, the invention will be described with an exemplary embodiment.

Fig. 1 shows a lift-induced propeller turbine (1) which can typically be installed with a device and a method according to the invention. On the installation shown, the propeller blades are pitch-regulated to increase efficiency and to be able to rotate the blades at least 180°, preferably in connection with changing the flow direction. The lift-induced propeller turbine (1) is mounted on a watertight capsule or housing (2) which typically forms a module, with equipment to convert the turbine's rotation into electrical power, including a generator, possibly a gear and control system. The housing or module (2) can also include secondary functions such as bilge devices for minor leaks. As the turbine blades can be rotated as described, the construction shown can be mounted in a locked position on a support structure (does not need to be rotated, unlike a windmill).

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

From fig. 2 shows an example of a housing (2) or a module that can be installed with the present invention. The module (2) comprises a turbine (1), a gear (22) for converting the rotational speed from the turbine, accumulator bottles (23) to protect against water ingress by means of overpressure protection of the housing or capsule, a generator (24) to convert mechanical energy from the gear (22) into electrical energy, a nacelle with pitch control (28) for turning the turbine blades, oil or other corrosion-preventing liquid (27), alternatively helium or other inert gas preferably with good heat-conducting ability with e.g. 0.5 bar overpressure in relation to the surrounding water pressure and an electrical connector (26) for connecting the generator (24) to cable (4) for introducing energy to land.

Figure 3 shows three installation steps where a turbine (1) and capsule (2) are lowered from the surface and guided into place by means of guide lines (18) that run from the top of the support structure up to a surface vessel (not shown). After the turbine (1) and capsule (2) have landed on top of the support structure, the capsule is mechanically locked to the support structure.

Finally, the cable is laid out so that a diver can attach it to the cable tray before the remaining cable is laid on the seabed and in to land (not shown). The cable is laid with a loop at the base of the support structure so that there is sufficient length to raise the capsule (2) and the turbine (1) to the surface during later repairs or maintenance.

Considering the turbine that will later be mounted on the tower pipe (3), the tower pipe (3) should be installed in a given orientation in relation to the direction of the water flow.

Figure 4 shows the installation of the cable pipe and the retraction of the cable. The cable pipe (10) is attached to the tower pipe (3) and can be hinged as shown in the figure. The cable (11) 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. Figure 5 shows how the guide wires (14) which will be used to control the nacelle and the turbine in place are established. Receivers (12) are mounted on each side of the tower pipe (3) into which teat posts (13) are lowered and locked (only shown on one side of the tower pipe). The guide wires (14), which run from the top of the guide posts (13) are tightened from the surface after the guide posts (13) are locked in the receivers (12). Figure 6 shows how the nacelle with turbine (2) is guided into place for final installation on top of the tower tube (3). On the side of the nacelle (2) are mounted guide tunnels (16) into which the guide wires (14) are threaded on the surface. The nacelle (2) is then lowered so that the guide tunnels (16) enter the guide posts (13). Furthermore, a conical tube (17) on the underside of the nacelle enters the tower tube. The top of the tower tube is designed so that the conical tube is well supported to absorb the bending moments the nacelle will be exposed to. The conical tube (17) can be equipped with a locking device that can be activated mechanically or hydraulically to lock the nacelle (2) to the tower tube (3).

The actual submersion of the nacelle from the surface until it has entered the support structure must take place in connection with a change in current direction where the current strength is low. Figure 7 shows the nacelle which is landed on top of the tower tube or support structure. The two parts are connected either by means of a flange, or by means of a locking device as described above in connection with figure 6. The cable from shore, which is installed inside the cable pipe (10) is connected to the nacelle by means of a short cable (4 ) from the nacelle (2) with suitable connectors. Alternatively, the cable can be connected to the nacelle on the surface and lowered together. Finally, the guide posts (13) are released and with the help of the guide wires (14) they are pulled to the surface. At this point, the plant is ready to start production. Figures 8 and 9 show how the operation described above can be carried out from a barge. When the nacelle and turbine blades are secured under the barge, the module can be transported ashore for repair and/or maintenance. An alternative to the barge shown is a completely normal barge with two davits over the side.

Claims (5)

1. Device for controlling a module (2) on a foundation (3), for an underwater facility located on a seabed for the production of energy from currents in bodies of water, where the foundation (3) is located on the seabed and includes an area adapted for joining with the module (2) and where the module (2) is adapted for placement on the foundation (3) from a surface vessel with at least one winch, characterized in that the device comprises: at least two receiver elements (12) with respective locking devices, located at the joining area of the foundation (3); guide posts (13) adapted to be lowered into the receiver elements (12) to be locked in them with the locking devices, which receiver elements (12) comprise engagement means that engage the guide posts (13) and lock them to the receiver elements (12); guide wire (14) extending between the surface vessel and the guide posts (13); at least two guide tunnels (16) placed on the module (2) at a distance adapted to the location of the receiver elements (12), where the guide tunnels (16) are further adapted for entry of the guide wires (14) and for entry into the guide posts (13); a conical tube (17) placed on the underside of the module (2) for entry into the foundation (3), where this is designed to fit together with the conical tube (17); a fixing device for fixing the module (2) to the foundation (3); and a hoist wire running between the module (2) and the winch mounted on the surface vessel for raising and lowering the module (2) between the surface vessel and the foundation along the guide wires (14). 2. Device according to claim 1, characterized in that the engagement means automatically engage with the guide posts (13) and can be remotely controlled to release the guide posts (13) from the receiver elements (12). 3. Device according to claim 1, characterized in that the hoist wire that runs between the module (2) and the winch can be detached from the module with a remote-controlled detaching device. 4. Device according to claim 1, characterized in that the fixing device for fixing the module (2) to the foundation (3) includes remote-controlled intervention means for fixing and releasing the module to the foundation. 5. Procedure for controlling at least one module for a foundation (3) placed on a seabed for an underwater plant for the production of energy from currents in bodies of water with a device according to claim 1, characterized by: placement of a vessel carrying the module (2) above the foundation (3); thread the guide wires (14) through the guide tunnels (16) placed on the module (2); lower the guide posts (13) with the guide wires (14) from the vessel down to the foundation (3); thread the guide posts (13) into the receiver elements (12) on the foundation (3); locking the guide posts (13) of the receiving elements (12) with the locking devices; tighten the guide wires (14) between the foundation and the vessel; hoist the module (2) down along the guide wires (14) with the hoisting wire; insert the conical tube (17) into the foundation (3); enter the guide posts (13) into the guide tunnels (16); and fasten the module (2) to the foundation with the fastening device.