NO333691B1 - A floating wind turbine. - Google Patents

Abstract

A floating wind power plant comprising a buoyancy body (3) configured to be immersed in water and supporting an equipment unit (2, 1a, b) extended over the water surface, and a ballast element (5) connected to the buoyancy body via at least one intermediate member (4a-c). . Control devices (31a, b, 32) in the buoyancy body (3) are configured for removable interaction with at least one intermediate piece so that the ballast member and buoyancy body are displaceable relative to each other. The buoyancy body (3) has an elongated shape with a front portion (9a) and a rear portion (9b), and the ballast element (5) has an elongated shape with a front portion (9a ') and a rear portion (9b').

Description

Floating wind turbines

Field of the invention

This invention relates to craft that float in a body of water. More specifically, the invention relates to a floating wind power plant which comprises a buoyancy body configured to be submerged in water and support an equipment unit that extends above the water surface, and a ballast element connected to the buoyancy body via at least one intermediate piece.

The background of the invention

The prior art includes WO 2010/093253 Al, which shows an offshore wind turbine installation comprising at least one floating body that supports a wind turbine. The floating body consists of a buoyancy body, an intermediate piece and a ballast structure, and the floating body is connected to a control arm which is further connected to a coupling structure with a turntable which is connected to anchor lines connected to seabed anchors.

The state of the art also includes JP 2005180351 A, which describes a floating wind power generator device that is able to prevent lateral movement and maintain stable position relative to a wave surface when a force is applied in a lateral direction relative to the water surface. A foundation column equipped with a main float at the bottom passes through an underwater float so that it can freely move vertically. When the foundation column is moved vertically on the water surface as a result of a wave force without a lateral force being applied, the water surface wind power generating device will be moved vertically without being disturbed by the underwater floating body.

This applicant has designed and brought forth this invention with the intention of overcoming certain limitations of the prior art and achieving additional advantages.

Summary of the invention

The invention is explained and characterized in the main claim, while the associated claims describe other characteristics of the invention.

A floating wind power plant has thus been produced which comprises a buoyancy body configured to support an equipment unit, and a ballast element connected to the buoyancy body via at least one intermediate piece, characterized by control devices in the buoyancy body configured for movable cooperation with at least one intermediate piece so that the ballast element and the buoyancy body are displaceable in relation to each other, and the buoyancy body has an elongated shape with a front part and an aft part, and the ballast element also has a corresponding front part and an aft part.

In one embodiment, each of the intermediate pieces is connected to the ballast element at one end, and at opposite free ends provided with a first stop device configured to cooperate with a corresponding second stop device on the buoyancy body.

A connecting element for one or more anchor lines is connected to the front part of the ballast element. The coupling element preferably comprises a turntable which is rotatably connected to the ballast element, in such a way that the floating plant is rotatable in a nominal horizontal plane.

The buoyancy body has ballastable watertight spaces, and the ballast element has ballastable watertight spaces.

In one embodiment, the floating facility further comprises an extension element connected to the free end of a front intermediate piece of such length that the upper end of the extension element extends above a nominal water level when the buoyant body is submerged below the water level indicated here.

The equipment unit is preferably supported by the aft part of the buoyancy body.

In a preferred embodiment, the equipment unit comprises a wind turbine generator supported by a column, of which the lower part of said column is attached to the buoyancy body.

The main purpose of the invention is to provide a floating offshore wind turbine plant that can be fully assembled on land, and where testing and verification of functionality is also carried out while the plant is on land. The level of completion achieved for the facility on land will mean significant cost savings.

Another main purpose of the invention is to reduce costs through the combined and controlled use of solid and liquid ballast. The design has thus been carefully adapted so that favorable ballasting provides such advantages.

Compared to the prior art, costs are also reduced by this invention through the ability to combine and adjust the use of solid ballast and water ballast. A systematic plan for ballasting in combination with other properties of the invention will entail a solution for the wind turbine plant which has very advantageous stabilizing properties. Low cost to achieve floating stability is an important characteristic for this type of installation, which will generally be very exposed to overturning forces.

This invention has a number of significant advantages compared to the prior art. This invention uses only one floating body. This one floating body serves as the foundation for only one wind turbine generator, and this simplification enables some significant advantages for this invention.

In the invention, a control arm functionality is integrated as part of the floating body. This has been achieved by having a buoyancy body with a distinctly elongated shape. The tower structure for the wind turbine is located at the aft end of the buoyancy body. Furthermore, a solution with a coupling structure for the mooring system is integrated in the front part of the ballast structure located below the buoyancy body. The functionality of the control arm, which is necessary to effectively turn with the direction of the wind, is achieved through the elongated buoyant body, which provides sufficient horizontal distance between the position of the wind turbine and the position of the anchoring system.

The invention involves retractable intermediate pieces in the form of columns or truss structures. This is achieved by the structural elements belonging to the intermediate piece being passed through openings in the buoyancy body. Stop device for each spacer element ensures the final position of the spacer.

Brief description of the drawings

These and the other characteristics of the invention will be clarified through the following description of preferred embodiments, given as non-limiting examples, with reference to the attached drawings where: Figure 1 is a side view of a first embodiment of a floating wind turbine plant in an operational state; Figure 2 shows section A-A as indicated in Figure 1; Figure 3 shows section B-B as indicated in Figure 1; Figures 4-6 show various phases of a preferred construction sequence; Figure 7 shows a stop device on the intermediate pieces; Figure 8 shows a vertical section of the lower part of the coupling construction according to the invention; Figure 9 shows a vertical section of the upper part of the coupling construction according to the invention; Figure 10 shows a vertical section of a second embodiment of a coupling construction according to the invention; Figure 11 shows section C-C as indicated in Figure 10; Figure 12 shows a floating wind turbine plant where power and equipment cables are partly on a drum, which is placed on a movable foundation located on the front part of the buoyancy body; Figure 13 shows a vertical section of the buoyancy body; Figure 14 shows a perspective view of the plant with the ballast element in an extended position, with that part of the plant configured to be submerged in the water when the plant is in operation (ie wind turbine with tower and generator not shown here); and Figure 15 shows a perspective of the plant with the ballast element in a raised position, with that part of the plant configured to be submerged in the water when the plant is in operation (ie wind turbine with tower and generator not shown here).

Detailed description of a preferred embodiment

Figure 1 shows a first embodiment of the floating wind turbine plant, in an operational configuration floating in a body of water W. The floating plant comprises a buoyancy body 3 connected to a ballast element 5 via intermediate pieces 4a,b,c. The buoyancy body 3 supports a wind turbine generator la via a column lb and a column connection 2. The column lb and the column connection 2 can be a continuous element. The floating plant is anchored to the seabed (not shown) via anchor lines 7 attached to the ballast element 5 through a coupling element 12. The floating plant is thus free to rotate about the coupling element 12 and thus orient itself according to the prevailing wind and current, thus defining a front part 9a and aft part 9b for the facility. Reference number 8 indicates power export and equipment cables.

The floating facility is configured to allow the combined use of solid ballast and water ballast to maintain buoyancy and heeling within acceptable limits for the facility in all applicable conditions. With reference to figure 2, the geometry of the buoyancy body 3 is elongated in shape and the body contains many watertight spaces 36, defined by transverse bulkheads 37 and longitudinal bulkheads 38.1 according to known principles, some of these spaces are used to be able to contain water ballast. Thus, water pumps 74 (see Figure 13; not shown in Figure 2) can occasionally move water from one ballast tank to another to adjust heeling as needed for the floating facility. Typically in cases without wind forces on the wind turbine plant, water ballast will be stored in one or more tanks located in aft section 9b. Typically in cases with maximum wind forces on the wind turbine plant, water ballast will be stored in one or more tanks 36b located in the front part 9a. Thus, according to this invention, the center of gravity in the longitudinal direction of the ballast element 5 is typically located a certain distance forward, measured relative to the center of buoyancy in the longitudinal direction of the buoyant body 3. Figure 2 also shows openings 31a,b for the aft intermediate pieces 4a,b and an opening 32 for the front intermediate piece 4c (see figure 1).

With reference to Figure 3, the ballast element 5 also has a forward part 9a' and an aft part 9b", and includes ballast space 136 built up of transverse bulkheads 137 and longitudinal bulkheads 138. Ballast material in solid form, for example in the form of finely crushed stone, is placed in indicated ballast room 136 before discharge and offshore installation of the plant. Pipes (not shown) are led inside each intermediate piece (4a-c) and further up to the ballast rooms (36). The pipes will enable placement of stone material inside the ballast rooms and simultaneous evacuation of water and/or air from these spaces. Ballasting operations are carried out based on planned access at the upper end of intermediate pieces (not shown). Figure 3 also shows aft footing point 51a,b for aft intermediate piece 4a,b and a forward footing point 52 for forward intermediate piece 4c Reference number 53 indicates an opening for the connecting element to the mooring lines inside the front intermediate piece(s).

Figure 4 shows assembled plant standing on a surface F at a fabrication workshop. The intermediate pieces 4a,b,c run through their respective openings 31a,b, 32 in the buoyancy body 3 (see figure 2). Thus, during construction and assembly of the facility, the buoyancy element 3 will rest on the ballast element 5. When the facility floats in the water W, for example during discharge (see figure 5), the ballast element 5 will remain in the retracted position relative to the buoyancy element 3. The intermediate pieces include expediently releaseable locking devices (not shown) to prevent accidental lowering of the ballast element 5. However, at a suitable time prior to or during the installation, the intermediate pieces 4a-c are pulled out from the buoyancy body 3, so that the ballast element 5 is lowered. Flexible tensile elements 6, for example cables, can be attached in an appropriate manner, and as indicated in Figure 6, between the buoyancy body and the ballast element to achieve a rigid connection between the ballast element and the buoyancy body.

The intermediate pieces 4a-c are connected with their respective first ends to the ballast element 5 (cf. description of foot point with reference to figure 3 above). The intermediate pieces are movable in relation to the buoyancy body 3 in that they are arranged in a displaceable manner in their respective openings 31a,b, 32 as stated above with reference to Figure 2. Each of the intermediate pieces also has a stop device at its respective free ends. With reference to Figure 7, the stop device comprises a conically shaped end part 14 on each intermediate piece and a corresponding conically shaped recess in the respective openings 31a,b, 32 in the buoyant body 3. Each stopping device is appropriately provided with a locking mechanism, such as locking pins, welded brackets , etc. (not shown).

The front intermediate piece 4c further comprises an extension 4d, which will extend above the nominal water level S when the floating plant is in a submerged operating state (see for example figure 1). The purpose of the intermediate piece extension 4d is to achieve simple and dry access to the towing ring system (described below) during installation and subsequent maintenance. The intermediate piece extension 4d is a slender tubular structure, possibly braced with vertical tensile members attached to several horizontal beams (not shown) which cantilever in radial directions at the top of the front intermediate piece 4c.

With reference to Figure 1 and Figure 8, the plant is properly secured to the seabed via anchoring lines 7 connected to a coupling element 12 in the ballast element 5. The coupling element 12 consists of a rotating body (turntable) 17 which is connected to the ballast element 5 via bearings 44, and rotatable around a centric part 16 which is attached to the seabed through a suitable anchoring system. The system is located in the front part of the ballast element 5 and barely protrudes past the bottom of the element.

The attachment points 19 for the anchor lines 7 are included in the centric part 16 of the turntable 17. The centric part 16 also includes at least one guide pipe 20 intended for high-voltage power cables and equipment cables 8 which are led between the wind turbine plant and the seabed.

An alternative solution for the connecting element is to include a guide pipe 21 for the anchor lines 7 (see figure 10). Thus, for this option, the centric part 1 lb of the turntable includes a multiple of guide tubes 21. At least one centrically placed guide tube 21 contains high voltage cables and additional cables 8.1 addition, the coupling structure contains a guide tube 21 for each anchor line 7.

Figure 11 shows a centrally placed guide pipe 21' for power and equipment cables surrounded by four pipes 21 each intended for their respective anchoring lines. Fewer or more pipes can be used based on the requirements given in each individual case. The guide tubes for anchor lines run from the base level of the ballast structure through the intermediate piece and on to the top of the intermediate piece extension, as shown in figure 10. The solution is provided with an upper axial bearing 62 and a lower radial bearing 63.1 upper end of each anchor line guide tube inside the intermediate piece extension, is located a mechanism that enables the secure attachment of the anchor line (not shown). In a similar way, the guide pipe for electric power cables passes through the turntable and further up to the top of

the intermediate piece extension. At this top level, a replaceable equipment unit 61 is mounted which contains a slip ring for the transmission of high-voltage electric power and signal transmission necessary for operation and monitoring of the installation, see Figure 9 and Figure 10 respectively. The front intermediate column is mounted on top of the ballast structure and axially aligned in line with the coupling structure which is found inside the ballast construction. In the event that an intermediate piece is in the form of a retractable truss structure, the elements that are part of the coupling construction will be located inside the front leg of the truss. In the case of an intermediate piece in the form of a closed column structure, the connection structure will be on the inside of the front closed part of the column structure.

A staircase and platform (not shown) for access to the offshore wind turbine facility are located at the aft end of the buoyancy body. As a result of the weathervane pear tip that characterizes the invention, stairs and platforms will always be positioned on the leeward side. The risk of damage due to extremely large waves hitting the installation is thus reduced. Furthermore, the solution for this invention will allow service personnel to enter the wind turbine plant at greater wave heights than would otherwise have been possible from the opposite edge where the incoming wind-generated waves hit.

This invention includes a method for assembling and installing the wind turbine plant. The wind turbine plant is assembled in a dry dock, on a barge, or on land (F, see Figure 4) to later be pushed aboard a barge for launching or on sliding beams that are placed sufficiently deep into the water. The invention involves the use of ballast in solid form in combination with water ballast, where the design of the construction is carefully adapted to ballasting and trim plans that utilize the advantages of each type of ballast material.

The buoyancy provided by the buoyancy body 3 and the ballast structure is used to float the unit (see figure 5). The unit is moved to a location where there is sufficient depth for the ballast structure to be lowered to an operational position. Water ballast is filled into the ballast structure to the extent necessary to lower the ballast structure and associated intermediate piece into the operational position (see figure 6). After intermediate pieces 4a-c have been attached to the buoyancy body 3 and tensile elements (6) have been tensioned, the ballast operations are completed. Ballast material in the form of finely ground stone is then fed into ballast element 5, by using transport pipes installed inside the intermediate piece.

After ballasting operations with stone and associated compensating water ballast as discussed above are completed, additional water ballast is supplied in water ballast tanks inside the buoyancy body. This additional ballasting is to lower the buoyancy body to operational depth (see figure 1), and involves filling water tanks in the buoyancy body.

This invention includes a method for connecting the turbine plant to suitable anchoring lines 7, and for connecting cables 8 which are connected to a transformer station when the plant is in operation. To disconnect the turbine plant, the operations described below must be carried out in reverse order.

With the floating unit correctly arranged with operational draft, the plant is towed offshore by tugboat to the current location in the wind farm and moored in the pre-installed anchoring system.

The anchoring system is attached to the coupling structure in the front part of the ballast structure. According to this invention, an alternative during the mooring operation would be to have segments of the anchor lines 7 pre-installed to the attachment points found in the centric part of the turntable (cf. figure 8). When the wind turbine is positioned on site, the pre-installed line segments are attached to the corresponding anchor lines that have been pre-installed.

After the mooring operation of the plant has been completed, power and equipment cables 8 are pulled through guide pipes located in the central part of the turntable. Conduit for electrical cable runs through the turntable and to the top of the intermediate piece extension that goes above the still water level (cf. Figure 9). On this top level, a replaceable equipment unit is mounted which contains a slip ring for the transmission of high-voltage electrical power and signal transmission necessary for operation and monitoring of the installation.

Another alternative for the installation operation is to pull up the anchor line segments through the guide tubes for anchor lines 21 (see figure 10). Thus, in this alternative solution, the centric portion 1 lb of the turntable accommodates a multiple of guide tubes with pre-installed retract lines. When the wind turbine installation is positioned on location, the pre-installed anchor line segments are attached to the corresponding and pre-installed pull-in lines. The winch on the installation vessel is used to reel in pull-in lines and get the anchoring line inside the connection structure for attachment to the wind turbine plant. After the mooring of the plant is completed, power and equipment cables are pulled through guide pipes located in the central part of the turntable.

In this invention, another solution for power and equipment cables will be that the cables are pre-installed together with pre-installed equipment unit for the transmission of high-voltage electrical power and signal transmission. The necessary cables to go to the substation can be rolled up on a drum 45 placed on a temporary and removable foundation frame 46 attached to the buoyancy body 3, and which also provides access for personnel during the installation as shown in figure 12.

After the plant is connected to the anchoring system in the hawind park, water ballast can be pumped out of the buoyancy body in the event that a pre-tensioned anchoring system is to be used at a given location.

Claims (10)

1. A floating wind power plant comprising a buoyancy body (3) configured to be submerged in water and supporting an equipment unit (2, la,b) extended above the water surface, and a ballast element (5) connected to the buoyancy body via at least one intermediate piece (4a- c), characterized by control devices (31a,b, 32) in the buoyancy body (3) configured for movable cooperation with at least one intermediate piece so that the ballast element and the buoyancy body are displaceable in relation to each other, and the buoyancy body (3) has an elongated shape with a front part (9a) and an aft part (9b), and the ballast element (5) has an elongated shape with a front part (9a') and an aft part (9b'). 2. The floating plant according to claim 1, where each intermediate piece (4a-c) is attached at one end to the ballast element (5) and at the other, free end, is provided with a first stop device (14) configured to cooperate with a corresponding second stop device (15) on the buoyancy body (3). 3. The floating installation according to claim 1, where a connecting element (12) for one or more anchor lines (7) is attached to the front part (9a') of the ballast element. 4. The floating plant according to claim 3, where the coupling element (12) comprises a turntable (17) rotatably attached to the ballast element, whereby the floating plant is rotatable in a nominal horizontal plane. 5. The floating plant according to each of the preceding claims, where the buoyancy body comprises ballastable watertight spaces (36). 6. The floating plant according to any one of the preceding claims, wherein the ballast element comprises ballastable watertight spaces (136). 7. The floating plant according to any one of the preceding claims, further comprising an extension element (4d) attached to the free end of the front intermediate piece (4c) and of such length that the upper part of the extension element reaches above a nominal waterline level (S) when the buoyant body is submerged below said waterline level. 8. The floating facility according to any one of the preceding claims, wherein the equipment unit (la,b, 2) is supported by an aft part (9b) of the buoyancy body (3). 9. The floating plant according to any one of the preceding claims, where the equipment unit comprises a wind turbine generator (lb) supported by a column (la, 2), of which the lower part (2) of a given column is attached to the buoyancy body. 10. The floating plant according to any one of claims 2 - 9, where each stop device comprises locking means.