NO348291B1

NO348291B1 - Load out method and system for offshore floating wind turbine

Info

Publication number: NO348291B1
Application number: NO20230438A
Authority: NO
Inventors: Eystein Borgen; Håkon Hernes
Original assignee: Odfjell Oceanwind As
Priority date: 2023-04-21
Filing date: 2023-04-21
Publication date: 2024-11-11
Also published as: WO2024218286A1; NO20230438A1

Description

LOAD OUT METHOD AND SYSTEM FOR OFFSHORE FLOATING WIND TURBINE

FIELD OF THE INVENTION

The present invention relates to a loading out method and system for offshore floating wind turbine.

BACKGROUND OF THE INVENTION

There are multiple ways to install floating offshore wind turbines depending on the design and location of the wind turbine. General steps involved in floating offshore wind turbine installations are:

- Assembling the turbine - the turbine is typically assembled onshore, and the main components, like the nacelle, rotor blades and tower sections are transported to the inshore installation site by vessel. The inshore installation site typically comprises a quayside and a flat area behind the quayside for the storage and assembly of large components.

- Connecting the turbine to the floating structure - the turbine is then mounted on top of the floating structure and connected to it using a special mounting system.

- Transporting the floating structure - the floating structure is typically transported, with the wind turbine already installed on top of the floating structure, to the offshore installation site using tugs.

- Attaching the floating structure - the floating structure is typically attached to the seabed using mooring lines, which are anchored to the seabed.

An alternative is to assemble the floating structure at the quayside and then launch it into the water by means of lifting with cranes, using a dry dock, or using an submersible barge in a float-off operation. In the case of using a submersible barge the floating structure is loaded onto the submersible barge using self-propelled multi wheel trailers (SPMTs), then the SPMTs are retracted and driven back to the quayside. Finally, the submersible barge is ballasted down until the deck of the submersible barge is submerged in water for the floating structure to float off freely and be towed away from the submersible barge. In this case the floating structure will have a relatively small draft since the tower and turbine is not installed yet. The wind turbine is typically installed with a large crane, after the launching operation, while the floating structure is moored along the quayside. However, the weight of large wind turbines, when installed on the floating structure, may cause the floating structure to float at a draft deeper than the available water depth at most port locations. This may make it impossible to install the wind turbine with a land crane which would otherwise be preferred due to lower cost. In addition, it is difficult, and in many cases not safe, to use a floating crane to install a wind turbine on a floating structure because of the risk of excessive relative motions between the two floating bodies.

It is therefore a desire to install the wind turbine on top of the floater before launching the floating structure into the sea and then float-off the floating structure in deeper water away from the quayside. However, this task is difficult because only very few submersible barges are available world-wide for such an operation. The challenge is that the weight of the wind turbine on top of a more than 120m tall tower will make the center of gravity (CoG) of the combined floating structure and wind turbine very high, with the risk of capsizing, lending only a few and expensive very wide submersible barges capable of carrying out such a launching task.

It is worth noting that the installation process for floating offshore wind turbines can be more complex than for fixed-bottom turbines, as it requires specialized equipment and expertise to install (and maintain) the floating structure and mooring system. Additionally, the installation process can take several days or even weeks, depending on the size and complexity of the turbine and the weather conditions at the installation site.

One objective of the present invention is to provide a method and a system, for loading out an offshore floating wind turbine that will allow for the assembly of an offshore floating wind turbine, comprising a foundation, a tower and a turbine, on dry land and the loading out of the offshore floating wind turbine with a reduced risk for capsizing.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a method for loading out an offshore floating wind turbine comprising the steps of

a) placing an offshore floating wind turbine on a vessel, wherein the offshore floating wind turbine comprises a floating foundation, a tower and a nacelle assembly; and

b) adding at least one stabilizing member under the floating foundation of the wind turbine; and

c) contacting the floating foundation of the offshore floating wind turbine with the at least one stabilizing member.

As used herein, the term “loading out” is used to denote moving the offshore wind turbine from the quay to a body water.

"Loading out operation" refers to the process of loading a heavy or oversized structure, such as an offshore platform or wind turbine, onto a barge or other transport vessel. This operation typically involves using lifting means such as cranes or self-propelled multi-wheel trailers (SPMT) to place the structure onto the barge or vessel.

Synonyms for "loading out operation" may include "load-out operation", "loadout operation", or simply "loadout". These terms are commonly used in the maritime and offshore industries to describe the process of moving large structures from a quay to a body water.

"Float-off operation" refers to the process of floating a vessel or structure off a heavy-lift ship or barge and into the water. Some synonyms for "float-off operation" include "launching operation", "floating operation", or simply "float-off". These terms are often used interchangeably in the maritime industry to describe the process of moving a vessel or structure from a floating platform onto the water.

A body of water may have the meaning of the sea, a lake, a fjord, or any other body of water where a floating wind turbine may be loaded out before being taken to its installation site.

In an embodiment, in step a) the offshore wind turbine may be placed on the vessel, so that the floating foundation extends beyond the surface of the vessel. In other words, the floating foundation may extend beyond the periphery of the vessel so that the floating foundation is not fully supported by the vessel.

In an embodiment, in step b), the at least one stabilizing member may be added under a portion of the floating foundation extending beyond a periphery of the vessel, i.e. a portion of the floating foundation extending beyond the vessel and above the sea surface.

In an embodiment, in step c), the floating foundation may be brought into contact with the stabilizing member by lowering the vessel, or/and by vertically moving the stabilizing member in an upwards direction towards the floating foundation.

In an embodiment, the stabilizing member may be a partially submersible stabilizing member.

In an embodiment the floating foundation may comprise a plurality of buoyancy elements (columns) linked by a framework.

As used herein, the term “buoyancy element” is used to denote a hull or other type of housing, which contains a material having a density lower than the density of water. The material having a density lower than the density of water will typically contain a gas, such as air.

In an embodiment, the floating foundation may comprise at least one buoyancy element, and the top surface of the at least one stabilizing member may have a complementary geometric shape to the at least one buoyancy element of the floating foundation. In other words, the top surface of the at least one stabilizing member is adapted to interface with the buoyancy element.

In another embodiment, a complementary geometric shape to a portion of the at least one buoyancy element of the floating foundation, may be a complementary geometric shape to a downwards facing side of the portion of the at least one buoyancy element of the floating foundation.

In an embodiment, a complementary geometric shape to a portion of the at least one buoyancy element of the floating foundation, may be a geometric shape being complementary to a geometric shape of the portion of the at least one buoyancy element of the floating foundation, the portion extending beyond a periphery of the vessel.

In an embodiment, a complementary geometric shape to a portion of the at least one buoyancy element of the floating foundation, may be a complimentary geometric shape configured to prevent horizontal movement between the stabilizing member and the floating foundation when the floating foundation is in contact with the at least a stabilizing member.

In an embodiment, there may be at least two, three, four, five, six, seven, eight, nine or ten stabilizing members.

In an embodiment, there may be one stabilizing member per overhanging buoyancy element. In other words, there may be one stabilizing member per buoyancy element that is not supported by the vessel. In other words, there may be one stabilizing member per buoyancy element that extend beyond the periphery of the vessel (so that it is not supported by the vessel.

In an embodiment, the method may further comprise the step of

d) coupling the floating foundation of the offshore floating wind turbine to the at least one stabilizing member, using a vertically directed guiding system.

In an embodiment, step d) may be executed after step c).

In an embodiment, the vessel may be a partially submersible vessel.

In an embodiment, the vessel may comprise at least one buoyancy tower.

In an embodiment, the at least one buoyancy tower may be removed from the vessel before step a) and attached to the vessel after step a).

In an embodiment, the method may further comprise the step of

e) assembling the offshore floating wind turbine at an assembly site near or on the vessel.

In an embodiment, step e) may be executed before step a).

In an embodiment, step e) may be executed simultaneously as step a).

In an embodiment, near the vessel may mean an inshore installation site on the quayside. The inshore installation site typically comprises a quayside and a flat area behind the quayside for the storage and assembly of large components.

In an embodiment, the assembly site is a quay to which the vessel is docked during step a).

In an embodiment, the method may further comprise the step of

f) partially submerging the vessel.

In an embodiment, the vessel has a deck and the vessel may be submerged until the deck of the vessel is below the surface of the water, one meter under the surface of the water or two meter under the surface of the water.

In an embodiment, the vessel may be submerged until the offshore floating wind turbine achieves floatation, in other words, until the offshore floating wind turbine achieves sufficient buoyancy to float off the vessel.

In an embodiment, step f) may be executed after step c) or step d).

In an embodiment, the method may further comprise the step of

g) steering the vessel to a location where the offshore floating wind turbine (1) can be lowered into water;

h) lowering the wind turbine in the water; and

i) separating the at least a stabilizing member (5) and the vessel (10) from the wind turbine.

In an embodiment, step g) and h) may be executed after step c) or step d).

In an embodiment, step h) may be executed by partially submerging the vessel.

In an embodiment, in step i), the at least a stabilizing member and the wind turbine may be separated first, and then the vessel and the wind turbine may be separated. This embodiment is particularly relevant for sideways unloading of the wind turbine from the vessel, for example when the vessel has multiple buoyancy towers, to avoid that the wind turbine and buoyancy towers collide during float-off operations.

In an embodiment, in step i), the vessel and the wind turbine may be separated first, and then the at least a stabilizing member and the wind turbine may be separated. This embodiment is particularly relevant for unloading of the wind turbine from the vessel via the bow or the stern of the vessel, for example when the vessel has no buoyancy towers on the bow or the stern.

In an embodiment, the vessel may be submerged until the offshore floating wind turbine achieves floatation, in other words, until the offshore floating wind turbine achieves sufficient buoyancy in order to be able to float off the vessel.

In a second aspect, the present invention relates to a system for loading out an offshore floating wind turbine, wherein the offshore floating wind turbine comprises a floating foundation, a tower and a nacelle assembly; the system comprising

‐ a vessel; and

‐ at least one stabilizing member.

In an embodiment, the floating foundation may comprise at least one buoyancy element, and the top surface of the at least one stabilizing member has a complementary geometric shape to the at least one buoyancy element of the floating foundation.

In an embodiment, a complementary geometric shape to the at least one buoyancy element of the floating foundation, may be a complimentary geometric shape configured to prevent horizontal movement between the stabilizing member and the floating foundation when the floating foundation is in contact with the at least a stabilizing member.

In an embodiment, the system for loading out an offshore floating wind turbine may further comprise

‐ a support and transport frame for the offshore floating wind turbine, the support and transport frame being built around a vertically arranged pipe, the pipe supporting the buoyancy element of the floating foundation to which the tower is coupled, the support and transport frame arranged to support and transport the offshore floating wind turbine in the transport phase on a vessel and/or load-out phase to a vessel or a submersible vessel or barge.

In an embodiment, the vertically arranged pipe has substantially the same diameter as the buoyancy element of the floating foundation to which the tower is coupled.

In an embodiment, the support and transport frame further comprises a flange, for connecting the pipe to the buoyancy element of the floating foundation to which the tower is coupled.

DETAILED DESCRIPTION

Embodiments of the invention will now be described in detail with reference to the enclosed drawings, wherein:

Fig. 1 is a perspective view of the of a wind turbine on a quay.

Fig. 2 is a perspective view of the of the loading of a wind turbine on a vessel. Fig. 3A is a perspective view of a transport frame.

Fig. 3B is a first perspective view of a support structure on a transport frame and SPMT.

Fig. 3C is a second perspective view of a support structure on a transport frame and SPMT.

Fig. 4 is a perspective view of the of the wind turbine loaded on a vessel.

Fig. 5 is a perspective view of the placement of stabilizing members under the wind turbine.

Fig. 6A is a perspective view of the stabilizing members being brought in contact with the support structure.

Fig. 6A is a front view of the stabilizing members being brought in contact with the support structure.

Fig. 7 is a perspective view of the partial sinking of the vessel.

Initially, it is referred to fig. 1, where a support structure is placed on an assembly site, here a dock, to accommodate the construction of a wind turbine 1. The floating foundation 2 of the wind turbine 1 may be assembled on site or in a different site and then transported to the assembly site. The tower 3 and the nacelle assembly 4 (not shown) of the wind turbine 1 are then assembled with the floating foundation 2 to form the wind turbine 1.

The floating foundation 2 comprises a plurality of buoyancy elements (columns) 21 linked by a framework 22.

As shown on fig. 2, the wind turbine 1 is then loaded on a vessel 50, in this example using a support and transport frame 10 and a number of self-propelled multi-wheel trailers (SPMT) 40.

Figures 3A-3C show the support and transport frame 10 for the offshore floating wind turbine foundation 2, where the support and transport frame 10 may be used to support the offshore wind turbine foundation 2, for instance, during manufacturing or storage of the offshore wind turbine foundation 2, or during transport of the offshore wind turbine foundation 2, for instance, from a quay area and to a vessel 50 which is to transport the offshore wind turbine foundation from a fabrication yard to a vessel as part of a loading out operation or of a float-off operation.

The support and transport frame 10 is also adapted to move an assembled wind turbine 1.

A number of self-propelled multiwheel trailers (SPMT) 40 may be used during the transport of the offshore wind turbine floating foundation 2.

The support and transport frame 10 is built around a central vertically arranged pipe 12 with substantially the same diameter as the center buoyancy elements 21 of the floating foundation 2.

Depending on the design of the wind turbine 1, the vertically arranged pipe 12 may not be central. The placement of the vertically arranged pipe 12 preferably coincides with the buoy or part of the floating foundation 2 on which the tower 3 will be mounted

A flange connection may be arranged between the pipe 12 and the center buoy 21 for transferring the weight from the wind turbine foundation 2 to the support and transport frame 10. Heavy box beams 11,13A are welded to the central vertically arranged pipe 12. Heavy outer beams 14 are welded to the heavy box beams 11,13A. Secondary beams 13B with a lower height is welded between the heavy box beams 11,13A and the heavy outer beams 14. Due to the lower height of the secondary beams enough vertical space is arranged allowing self-propelled multiwheel trailers (SPMT) 40 to be positioned under the secondary beams 13B, thus allowing the load transfer between the support and transport frame 10 to the SPMT 40s.

The support and transport frame 10 is arranged to support and transport the offshore floating wind turbine foundation 2 in the transport phase on a vessel, and/or loadout phase to a vessel 50 and can also have the function of grillage/seafastening for distributing the loads between the floating structure and the vessel during a sea transportation.

Furthermore, the outer profile element 14 and the inner profile element 11A are connected to each other through a plurality of transverse extending beam elements 13.

The transverse extending beams elements 13B have a lower height than the outer and inner profile elements 11, 13A, 14, thereby providing a space between a ground and an upper surface of the support and transport frame 10, such that a number of self-propelled multiwheel trailers 40 may be used to lift and transport the support and transport frame 10.

The support and transport frame 10 is arranged to support and transport the offshore floating wind turbine foundation 2 or the wind turbine 1 in the load-out phase and/or float-off phase from a submersible vessel and/or the transport phase on a vessel 50.

Going back to figure 2, the vessel 50 may for example be a barge, for example a semi-submersible heavy lift and launching cargo barge, such as a BOA barge 38. This kind of vessel 50 is advantageous for launching wind turbines because it comprises buoyancy towers that stabilize the vessel 50 during the float-off operation when the vessel deck is submerged in water and therefore much of the stability is lost. Some of these buoyancy towers may be removable, to facilitate loading and unloading. Such a vessel 50 reduces the chances of the vessel 50 capsizing during loading and steering of the vessel 50.

It is worth noting that vessels are generally much smaller than the foundation of modern large offshore wind turbines 1 which can often have a rated power of more than 12MW, reducing the stability of the loaded wind turbine. In addition, the rotor and nacelle , placed on top of the tower, causes the wind turbine to have a high center of gravity. These factors result in a high-risk situation where the vessel may easily capsize during loading and navigation.

Wider vessels that can fully accommodate the foundation of the wind turbine also exist and may be used to reduce the likelihood of the vessel capsizing, but such vessels are much more expensive to hire due to its larger size.

Therefore, in the inventive method, at least a stabilizing member 5, 5a, 5b is placed under the floating foundation 2 of the offshore floating wind turbine 1. The stabilizing member 5, 5a, 5b may for example be a floating element, preferably which buoyancy can be adapted, in other words, the stabilizing member 5, 5a, 5b can be partially sunken or floated in order to be placed under and then put in contact with the floating foundation 2. These steps are illustrated in fig. 4, fig.5 and fig. 6A - 6B.

In detail, in fig. 4, a floating foundation (NO20230146) is illustrated after loading on the vessel and comprises a plurality of buoyancy elements (columns) 21 linked by a framework 22. One of the buoyancy elements 21 is over the vessel and the other two buoyancy elements 21 hang over the water. These buoyancy elements 21 do not contribute to stability stopping the wind turbine 1 from capsizing for example around the longest axis of the vessel 50 until these buoyancy elements 21 are submerged in water.

Assuming a flat quayside area and the vessel being arranged vertically flush (even height) with the quayside during the load out operation, the bottom of the buoyancy elements 21 will necessarily have to be arranged higher than the quayside and therefore also higher than the vessel deck during the load-out operation. On typical SPMTs it is possible to elevate/lower the transported item (in this case the wind turbine 1) /- 300mm. In theory this could be sufficient to lower the wind turbine 1 down upon placement on the vessel to ensure that the bottom of the overhanging buoyancy elements 21 will get slightly submerged in water before the deck of the vessel is submerged when doing a float-off operation with a submersible barge. However, /- 300mm is not regarded as a safe margin due to tolerances which have to be considered, such as but not limited to, flatness of the quay area, tilt of the wind turbine 1 during the load-out operation on the quayside and from the quayside to the vessel, tilt of the vessel during the float-off operation.

Therefore, two stabilizing members 5a and 5b are placed under the buoyancy elements as illustrated in fig. 5 in order to extend the effective length of the buoyancy elements 21 for example during the float-off operation from vessel 50 such as a submersible barge.

Then, as illustrated in fig. 6A and 6B, the buoyancy of the stabilizing members 5a and 5b is increased, allowing for contact between the stabilizing members 5a and 5b and the buoyancy elements of the floating foundation 2, in order to further stabilize the offshore structure during the further operations, especially when the deck of the vessel 50, for example a submersible barge, is getting below the water surface during ballasting down the vessel 50. Alternatively the vessel 50 may be ballasted down, achieving the same result.

Thereafter the vessel 50 may be partially sunk as illustrated in fig. 7, during this operation, the stabilizing member 5 will also be partially sunk at the same time (being pushed down due to the contact with the buoyancy elements 21, or being ballasted in parallel with the vessel ballasting) in order to ensure that the wind turbine 1 and vessel 50 are stable.

The vessel may for example be partially sunk until the water level is at the deck level, or over the deck level.

When submerging the deck of the vessel 50 below the surface of the water, the vessel 50 will lose the waterplane area related to the deck surface and thereby lose most of its hydrostatic stability. In order to increase the hydrostatic stability during the submergence operation, submersible vessels are therefore typically equipped with vertical floatation towers which penetrates the surface of the water/sea even when the vessel deck is below the water surface. However, due to the very high centre of gravity of the combined vessel/barge and modern large wind turbines with tower, only very large and wide vessels will be able to carry out such an operation without capsizing. Such vessels are not available in big numbers and are expensive to build or rent. It is therefore advantageous to present a loading out method in which much smaller vessels can be used for such operations. Smaller barges can be found in larger numbers and are less expensive to build or rent.

Description of a method to obtain sufficient stability of the combined vessel and stabilizing member(s) with wind turbine during the loading out operation:

An offshore floating wind turbine 1, comprising a floating foundation 2, a tower 3 and a nacelle assembly 4 is assembled on land.

The assembled wind turbine 1 is then loaded onto a vessel 50 by the use of a transportation frame 10 and self-propelled multiwheel trailers (SPMT) 40 and positioned on the vessel 50 on suitable supports or directly onto the deck, or using the transportation frame 10 as support on deck.

The floating foundation comprises a plurality of buoyancy elements (columns) 21 linked by a framework 22.

The SPMTs 40 are removed and returned to the quayside. At least a stabilizing member 5 is floated into position below at least one of the buoyancy elements (columns) of the floating foundation 2 which are protruding outside the deck of the vessel.

Each of the at least a stabilizing member 5 comprises a stabilizing float. Each stabilizing float may advantageously have an upper footprint similar to the lower footprint of the buoyancy elements 21. In other words, the upper surface of the stabilizing float has a complementary geometric shape to the lower surface of the buoyancy elements 21 of the floating foundation 2.

A vertically directed guiding system (restricting horizontal movements) may be provided to couple the lower end of the buoyancy elements to the upper part of the stabilizing member 5.

This guiding system may for example be concentric rings with slightly different diameters, the concentric axis arranged in the vertical direction, whereby one ring is mounted on each wind turbine substructure buoyancy member (column) and one ring is mounted on each stabilizing float.

The guiding system may also be individual guiding pins and buckets or parts of concentric rings, or any other form of vertical guiding to resist movement in the horizontal directions. With this configuration the stabilizing members will be locked to the floating platform in the horizontal direction but free to move apart from each other in the vertical direction.

The stabilizing members 5 are then brought in contact with the floating foundation 2 of the wind turbine 1 by either ballasting the vessel 50 to a deeper draft, or by deballasting the stabilizing members 5 to a smaller draft, or a combination of the two. It is also envisaged that the two parts could initially be brought together by any other practical means like winching, hoisting, jacking etc.

Once in contact, the at least one stabilizing member 5 can be mechanically connected to the floating foundation 2 in the vertical direction, but this connection is not always necessary, for example when there are at least two stabilizing members 5 arranged at each side of the vessel 50 because the buoyancy force for the at least one stabilizing member 5 will at any time be positive and push the float towards the wind turbine floating foundation buoyancy elements (columns), hence avoiding roll of the vessel. Once the vessel is further ballasted down, the upward acting buoyancy force on each stabilizing member 5 will increase and ensure a stable connection, especially when the upper footprint of the stabilizing member 5 is complementary to the lower footprint of the buoyancy elements of the floating foundation 2, more particularly when these footprints are not flat.

It is a preferred feature of the invention that the at least a stabilizing member 5 is in contact with the floating foundation before water reaches the vessel deck level.

Then the vessel 50 may be re-positioned, either on its own motion or towed to a location where the offshore floating wind turbine can be fully lowered into water. This method allows the offshore floating wind turbine to be assembled in dry conditions onshore or in most docks, even if the water at the dock or at the quayside is shallow, and then be transported to a site with deep enough water before being lowered into water, or transported directly to the installation site.

The vessel is then ballasted further down. Once the buoyancy elements (columns) of the floating foundation 2 are sufficiently submerged in water, this could be typically 0 to 10m or even 10 to 30m, the stabilizing members 5 can be removed by adding weight to the stabilizing members 5.

The weight could for example be water ballast inside the stabilizing members 5. When adding weight, the at least a stabilizing member 5 will sink downwards hence releasing itself from the guiding system. Separate, small surface floats can alternatively be attached to the stabilizing members 5 by a slack wire, rope or the like, to ensure that they will not sink too deep. Then the stabilizing members 5 can be picked up by a boat and removed.

The submerging operation can then continue by ballasting the vessel 50 until the wind turbine floating foundation 2 floats off the submersible vessel 50 and can be pulled away from the submersible vessel 50.

It should be understood that the removal of the stabilizing members 5 can also be carried out after the wind turbine substructure floats off the submersible barge/vessel.

It should also be understood that in some cases it could even be possible to remove the stabilizing members even before the wind turbine substructure buoyancy elements (columns) have entered the water/sea. However, this might increase the risk of capsizing and must therefore be studied and planned in detail. In this embodiment the vessel 50 will roll to the side until one of the wind turbine substructure buoyancy elements (columns) enter the water/sea and hydrostatic stability is again achieved. If the buoyancy elements (columns) of the wind turbine floating foundation 2 are close enough to the water surface when the stabilizing members 5 are removed, the resulting roll angle will be small and might be within acceptable limits. For example, if the gap between the column and the sea is 1m when the stabilizing members 5 are removed and the distance between the columns is 80m, the static roll angle will be approximately 1-2 degrees. However, when this roll motion occurs there will be a dynamic transient response which could result in even larger roll angles. Therefore, the preferred option is to remove the stabilizing members 5 after the columns are at least partially submerged in water.

Claims

1. A method for loading out an offshore floating wind turbine (1) comprising the steps of

a) placing an offshore floating wind turbine (1) on a vessel (50), wherein the offshore floating wind turbine (1) comprises a floating foundation (2), a tower (3) and a nacelle assembly (4);

b) adding at least one stabilizing member (5) under the floating foundation (2) of the wind turbine (1); and

c) contacting the floating foundation (2) of the offshore floating wind turbine (1) with the at least one stabilizing member (5).

2. The method according to claim 1, wherein the stabilizing member (5) is a partially submersible stabilizing member (5).

3. The method according to claim 1 or 2, wherein the floating foundation 2 comprises at least one buoyancy element, and wherein the top surface of the at least one stabilizing member (5) has a complementary geometric shape to the at least one buoyancy element of the floating foundation (2).

4. The method according to any one of the previous claims, further comprising the step of

d) coupling the floating foundation (2) of the offshore floating wind turbine (1) to the at least one stabilizing member (5), using a vertically directed guiding system.

5. The method according to any one of the previous claims, wherein the vessel (50) is a partially submersible vessel.

6. The method according to any one of the previous claims, wherein the vessel (50) comprises at least one buoyancy tower.

7. The method according to any one of the previous claims, further comprising the step of

e) assembling the offshore floating wind turbine at an assembly site near or on the vessel (50).

8. The method according to any one of the previous claims, wherein the assembly site is a quay to which the vessel is docked during step a).

9. The method according to any one of the previous claims, further comprising the step of

f) partially submerging the vessel.

10. The method according to any one of the previous claims, further comprising the step of

h) lowering the wind turbine in the water; and

11. The method according to any one of the previous claims, wherein in step i), the at least a stabilizing member (5) and the wind turbine (1) are separated first, and then the vessel (10) and the wind turbine (1) are separated.

12. A system for loading out an offshore floating wind turbine (1), wherein the offshore floating wind turbine (1) comprises a floating foundation (2), a tower (3) and a nacelle assembly (4); the system comprising

‐ a vessel (50); and

‐ at least one stabilizing member (5),

wherein the floating foundation (2) comprises at least one buoyancy element, and wherein the top surface of the at least one stabilizing member (5) has a complementary geometric shape to the at least one buoyancy element of the floating foundation (2).

13. A system for loading out an offshore floating wind turbine (1) according to claim 12, further comprising

‐ a support and transport frame (10) for the offshore floating wind turbine (1), the support and transport frame (10) being built around a vertically arranged pipe (12), the pipe (12) supporting the buoyancy element (21) of the floating foundation (2) to which the tower (3) is coupled, the support and transport frame (10) arranged to support and transport the offshore floating wind turbine (1) in the transport phase on a vessel and/or load-out phase to a vessel or a submersible vessel or barge.

14. A system for loading out an offshore floating wind turbine (1) according to claim 13, wherein the vertically arranged pipe (12) has substantially the same diameter as the buoyancy element (21) of the floating foundation (2) to which the tower (3) is coupled.

15. A system for loading out an offshore floating wind turbine (1) according to claim 13 or 14, wherein the support and transport frame (10) further comprises a flange, for connecting the pipe (12) to the buoyancy element (21) of the floating foundation (2) to which the tower (3) is coupled.