NO347364B1

NO347364B1 - Construction of offshore wind power plants

Info

Publication number: NO347364B1
Application number: NO20211547A
Authority: NO
Inventors: Christophe Bekhouche; Skule Pedersen; Jarle Gullaksen
Original assignee: Aker Offshore Wind Operating Company As
Priority date: 2020-12-21
Filing date: 2021-12-20
Publication date: 2023-10-02
Also published as: NO20201416A1; NO346577B1; GB202101058D0; NO20211547A1

Description

CONSTRUCTION OF OFFSHORE WIND POWER PLANTS

The present invention relates to a method for construction of wind power plants, and particularly to a method for constructing offshore, bottom-fixed wind power plants.

BACKGROUND

Offshore wind power is growing in importance worldwide, with the recent years having seen a number of large development projects being commissioned, among other places in the North Sea. At present, such development projects mainly utilize bottom-fixed wind turbine generators, i.e. wind turbine generators which are mounted on a bottom-fixed structure such as a piled or gravity-base foundation to form a power plant. While floating wind turbine generators are being investigated by various groups worldwide, bottom-fixed technology is currently the most competitive at shallower water depths. Bottom-fixed wind turbine generators are currently feasible at water depths of up to about 60 m, and with future advances in technology, it is likely that bottom-fixed systems will be suitable for even larger water depths.

Publications which may be useful to understand the field of technology include:

WO11102738, WO03066427, WO11028102, EP2251254, EP3170730, GB2580103, EP2505484, GB2479232, US2009217852, EP2307269, US2004262926, WO2006080850, WO2006076920.

With a projected continued increase in the investments into wind power in the future, there is a need for further improved technology in this area. The present disclosure has the objective to provide such improvements, or at least alternatives, to the current state of the art.

SUMMARY

In an embodiment, there is provided a vessel for the transport and installation of a wind power plant, the vessel comprising: a hull comprising an engagement structure for engaging a wind power plant, the engagement structure comprising a height-adjustable coupling arrangement; the height-adjustable coupling arrangement being configurable to be coupled to a wind power plant and permit vertical displacement of a wind power plant relative to the vessel between a raised position for transporting a wind power plant and a lowered position for installation of a wind power plant in a desired location; and wherein in the raised position, the height-adjustable coupling arrangement is lockable to restrict vertical and horizontal displacement of both the height-adjustable coupling arrangement and a coupled wind power plant, so as to transport a coupled wind power plant in a semi-submerged state on the vessel.

In an embodiment, there is provided a method for transport and installation of an offshore wind power plant, the method comprising: providing a vessel for the transport and installation of the wind power plant; mounting the wind power plant to a height-adjustable coupling arrangement on the vessel; transporting the wind power plant in a semi-submerged state to a desired location with the height-adjustable coupling arrangement in a raised position in which vertical and horizontal displacement of the height-adjustable coupling arrangement and the wind power plant is restricted; and installing the wind power plant in a desired location by moving the height-adjustable coupling arrangement to a lowered position.

The detailed description, figures and claims outline further inventive aspects and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics will become clear from the following description of illustrative embodiments, given as non-restrictive examples, with reference to the attached drawings, in which

Figs 1-6 show various steps of a method of constructing and installing a wind power plant according to an embodiment.

Figs 7-12 illustrate an example of the construction of a wind power plant at and near a shoreside.

Figs 13-16 illustrate an example of transporting and landing a wind power plant using a barge.

Figs 17 and 18 illustrate steps of a method using a vessel for transport and landing a wind power plant.

Fig. 19 illustrates an example of a vessel suitable for carrying out method steps relating to transporting and landing a wind power plant.

Figs 20 and 21 illustrate an example of a vessel suitable for carrying out method steps relating to transporting and landing a wind power plant.

Figs 22-27 illustrate a vessel for the transport and installation of a wind power plant.

DETAILED DESCRIPTION

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ”upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

Figures 1-6 illustrate a method of constructing a wind power plant 10 according to an embodiment. The method comprises providing a mast support structure 1 and positioning the mast support structure 1 on an underwater base 3 adjacent a shoreside 2. The mast support structure 1 may, for example, be a jacket or truss structure, which can provide advantageous handling capability, structural strength and constructability.

The underwater base 3 may, for example, be a concrete underwater foundation, a pre-piled seabed foundation or similar, prepared for supporting the mast support structure 1 thereon. The underwater base 3 may, for example, be arranged at a water depth of more than 20m, more than 30m or more than 40m. The underwater base 3 is advantageously arranged so that a shoreside, land-based crane 6 can reach a position above the base 3. A long-reach crane 6 may be employed for this purpose, as required. (Optionally, a floating or jack-up vessel crane may be used, as described below.) Preferably, the shoreside 2 comprises a quay so that a horizontal distance between the land-based crane 6 or other shoreside equipment and the base 3 can be minimised.

Providing the mast support structure 1 may comprise building the mast support structure 1 at least partly on the shoreside 2. Advantageously, the mast support structure 1 can be built fully, i.e. in its entirety, on the shoreside 2 and subsequently positioned on the underwater base 3 by moving the mast support structure 1 from the shoreside 2 to the base 3. This is illustrated in Figs 1 and 2, where a complete or close-to-complete mast support structure 1 is moved from the shoreside 2 and positioned on the base 3. Moving and positioning the mast support structure 1 onto the underwater base 3 can be carried out by use of the land-based crane 6, another crane, and/or other shoreside equipment, as appropriate.

Alternatively, the mast support structure 1 can be built partially on the shoreside 2 and partially on the base 3. For example, a first section of the mast support structure 1 can be built on the shoreside 2 and positioned on the base 3, and thereafter a second section of the mast support structure 1 can be built or connected onto the first section while the mast support structure 1 is on the base 3.

Building the mast support structure 1 at the shoreside 2 may comprise building the mast support structure 1 by use of the land-based crane 6 and other shoreside equipment, as appropriate.

Alternatively, the mast support structure 1 can be provided from a remote location and positioned on the underwater base 3. For example, if the mast support structure 1 is built elsewhere, for example at a remote yard, it can be provided to the shoreside 2 or the base 3 from the yard, for example by ship. In such a case, the mast support structure 1 can be provided directly onto the base 3 without being placed at the shoreside 2 at all, or it can be provided to the shoreside 2 and thereafter be positioned on the base 3, for example by the crane 6. The latter case may be most suitable if, for example, a number of mast support structures are provided in one shipment to the shoreside 2 and temporarily stored.

With the mast support structure 1 positioned on the base 3, the method further comprises mounting a wind turbine generator 4 onto the mast support structure 1 to form a wind power plant 10, as illustrated in Fig.3. As used herein, the term wind power plant 10 thus comprises both the mast support structure 1 and a wind turbine generator 4, the latter comprising a tower 21, a nacelle section 22 and a plurality of blades 23 (see Fig.6). Forming the wind power plant 10 may comprise mounting the wind turbine generator 4 onto the mast support structure 1 using the land-based crane 6. This may include mounting at least one tower section 21, at least one nacelle section 22 and at least one turbine blade 23 onto the mast support structure 1. These components may be mounted individually and sequentially, or with more than one of these mounted together in one operation. At least one of the tower section 21, nacelle section 22 and turbine blade 23, or optionally all these, can be mounted by use of a land-based crane 6.

Mounting the wind turbine generator 4 or one or more of its components on the mast support structure 1 while the mast support structure 1 is positioned on the base 3 and using of the land-based crane 6 may simplify the construction and mounting operations. For example, lifting of heavy components from a floating barge or vessel is avoided, and/or it is more practicable to carry out the mounting operations in several steps in an efficient manner. By carrying out these operations at or near the shoreside 2, weather impacts are also reduced.

Further, by having the mast support structure 1 arranged on the underwater base 3 while mounting the wind turbine generator 4 or one or more of its components reduces the required lifting height for installation and mounting operations.

Optionally, or additionally, some or several of the operations described above as carried out by the land-based crane 6 can be carried out by a barge or vessel-based crane 24 arranged on a barge or vessel 25, illustrated in Fig.8. The barge or vessel 25 may be floating or for example a jack-up vessel which can be fixed to the sea floor for these operations. Even with a floating barge or vessel for carrying out these operations, the advantages mentioned above of avoiding heavy lifts and installation operations offshore can be realized, in that the conditions at or near the shoreside 2 will usually be more advantageous and weather impacts lesser. Using a crane barge or vessel 25 for this purpose may, for example, be relevant where suitable shoreside equipment cannot be provided or shoreside structural conditions don’t allow for crane operations. In such a case, a barge or vessel-based crane 24 may, for example, pick up or otherwise be provided with components to be installed from the shoreside 2.

When the wind power plant 10 is substantially complete, illustrated in Fig.3, the method comprises picking up the wind power plant 10 with a barge or vessel 5 and transporting the wind power plant 10 from the shoreside 2 to an installation site 11. This is illustrated in Figs 4-6. At the installation site 11, the mast support structure 1 is landed and fixed to the sea floor 12, thereby installing the wind power plant 10 and making it ready for electrical hook-up and operation.

Transporting the wind power plant 10 from the base 3 to the installation site 11 is advantageously carried out with at least a part of the mast support structure 1 submerged. This can be the case during the entire transport operation, thus, if water depth conditions along the transport route allow it, obviating the need for lifting the wind power plant 10 to a higher level than that required to lift it off the base 3.

Advantageously, at least a part of the transport operation may including transporting the wind power plant 10 with the mast support structure 1 submerged to a water depth which is lower than that at the base 3. This may allow the centre of gravity to be further lowered for the transport operation. This step may include lowering the wind power plant 10 a pre-defined amount from the barge or vessel 5 after the barge or vessel 5 has picked up the wind power plant 10 from the base 3 but before it is lowered onto the sea floor 12, such that a part of the transport operation is done with the mast support structure 1 being submerged to a larger depth than when positioned on the base 3. Hence, in this example, the barge or vessel 5 may lift the wind power plant 10 off the base 3, commence the transport operation, and, when the barge or vessel 5 has moved away from the base 3 and water depth conditions allow, further lower the wind power plant 10 to lower the centre of gravity for example by a few or several meters.

The submerged part of the mast support structure 1, during transport and/or when positioned on the base 3, can make up at least half of the height of the mast support structure 1, at least 60% of the height of the mast support structure 1, or at least 75% of the height of the mast support structure 1.

The step of picking up the wind power plant 10 with the barge or vessel 5 may comprise lifting the wind power plant 10 off the base 3 with a handling assembly 30 arranged on the barge or vessel 5. An example of such a handling assembly is illustrated in Fig.19, described in further detail below.

Alternatively, or additionally, the step of picking up the wind power plant 10 with a barge or vessel 5 may comprise fixing the wind power plant 10 in relation to the barge or vessel 5 and adjusting the draught of the barge or vessel 5 to lift the wind power plant 10 off the base 3. The barge or vessel 5 may, for example, be a barge specifically designed for this purpose, for example as described below.

Figs 7-12 illustrate another example of the construction of a wind power plant 10. Illustrated in Fig.7, a mast support structure 1 is constructed at a shoreside 2 by means of a crane 6. In this example, a second crane 24 arranged on a barge or vessel 25 as described above is used to assist the construction of the mast support structure 1. In this case, the barge or vessel 25 is a floating crane barge. Other equipment on the shoreside 2 and/or on the barge or vessel 25 may be employed, as required.

In Figs 8 and 9, the complete or substantially complete mast support structure 1 is moved from the shoreside 2 onto an underwater base 3 adjacent the shoreside 2. In this example, moving the mast support structure 1 is carried out by both cranes 6,24, however using one of these cranes may also be possible. Additionally or alternatively, other equipment, such as other cranes or other lifting or handling equipment, could be employed for this purpose.

Illustrated in Figs 10-12, with the mast support structure 1 positioned on the base 3, a mast 21, a nacelle 22, and a plurality of blades 23 are mounted on the mast support structure 1 to form the wind power plant 10 (see Fig.12).

Figs 13-16 illustrate a pick up, transport and installation sequence according to one example, using a barge 5. A tug 35 can be used for moving the barge 5 with the wind power plant 10 from the base 3 and to an installation site offshore, as shown in Figs 13 and 14. Fig.15 illustrates the barge 5 carrying the mast support structure 1 and thereby the wind power plant 10 for the transport operation.

Fig. 16 illustrates the barge 5 having arrived at and positioned above the installation site 11. Landing the mast support structure 1 to the sea floor 12 at the installation site 11 may be done by lowering the wind power plant 10 from the barge 5, e.g. by winches or a handling assembly 30 as described in relation to Fig.19 below, and/or by de-ballasting the barge 5 to lower the barge 5 and the wind power plant 10 together towards the sea bed 12.

Illustrated in Fig.16, the installation site 11 may have a prepared foundation or foundations 31, such as a piled foundation arranged to engage a lower part of the mast support structure 1 and fix it to the sea floor 12. The foundations 31 may, for example, comprise receptacles arranged to receive legs of the mast support structure 1.

Figs 17 and 18 illustrate another embodiment, in which a vessel 5 is arranged to carry two wind power plants 10 for installation. The method may otherwise be similar to that described elsewhere in this disclosure.

Fig. 19 illustrates another example where a special purpose vessel 5 is employed to transport the wind power plant 10 from the base 3 to the installation site 11. The special purpose vessel 5 may, for example, be a purpose-built vessel for this operation or a converted vessel such as a semi-submersible rig or construction vessel. Fig.19 also illustrates a handling assembly 30 for engaging and carrying the wind power plant 10. Such handling assembly 30 may be arranged on the other examples for the vessel or barge 5 described herein. The handling assembly 30 may be arranged to fix, grip or otherwise hold the mast support structure 1 and/or the tower 21 for the purpose of lifting the wind power plant 10 off the base 3, holding it during transport, and for lowering and installing it at the installation site 11.

Figs 20 and 21 illustrate another example for a vessel 5 suitable to carry out the methods described herein. The vessel has a receptacle 34 arranged to receive the mast support structure 10 therein. Suitable equipment can be arranged on the vessel 5 to engage and hold the wind power plant 10 in the receptacle 34. Such a receptacle 34 can also be used with a barge 5 as shown in Figs 13-16. This can provide advantages of improved stability and handling capability for the vessel or barge 5 when picking up, transporting and/or landing the wind power plant 10. For example, with such an arrangement, when picking up the wind power plant 10 from the base 3, the vessel or barge 5 can be positioned such that the vessel or barge 5 supports the mast support structure 1 on at least at two horizontally opposing sides for the purpose of lifting it off the base 3 and fixing it to the vessel or barge 5 for transport.

Figure 22 illustrates an example of a vessel 100 for the transport and installation of a wind power plant (illustrated in Figures 27a-c, for example). In the example of Figure 22 the vessel 100 comprises a single hull 102. In some examples the vessel 100 may comprise more than one hull, the vessel 100 may e.g. be a catamaran. The hull 102 illustrated in Figure 22 comprises an engagement structure 101, i.e. a receiving portion or a receptacle for a wind power plant as described below in more detail.

The engagement structure 101 may be shaped so as to facilitate engagement of a structure such as a wind power plant, or part thereof, therein. For example the engagement structure may comprise a plurality of arms that extend from the hull 102 of the vessel 100 to permit engagement of a structure therein. The engagement structure 101 may comprise a gripping member for gripping a structure engaged therein. The engagement structure 101 may have a U-shape to engage a wind power plant, or part thereof, therein according to the methods described herein. The U-shape may be formed by providing two arms that extend from the hull 102, thereby forming a U-shape with the hull and defining a gap therebetween. Having a U-shape may permit the engagement structure 101 to engage a structure on multiple sides, thereby resulting in a secure engagement, when the structure is positioned therein. A structure may be positioned in the gap defined by the arms extending from the hull 102. The shape of the engagement structure 101 may be dependent on the geometry of the wind power plant to be transported. In some examples, there may be more or fewer than two arms extending from the hull 102, and forming part of the engagement structure 101, such as one arm or three arms.

The engagement structure 101 may be integrally formed with the hull 102, and may be considered to comprise a part of the hull 102. The engagement structure 101 may be made up of sponsons or equivalent which are fixed to the hull 102.

In some examples the engagement structure 101 may be added to or mounted onto an existing ship or vessel to convert the ship/vessel to a vessel 100 as illustrated, suitable for carrying out the methods described herein. The conversion may be completed by mounting a conversion structure onto the existing ship/vessel to convert the ship/vessel for the described usage (e.g. mounting onto the hull 102 of an existing vessel). In cases where the engagement structure 101 is mounted onto the hull of an existing vessel, the structure may extend along at least some of the hull in a longitudinal direction, which may facilitate a secure and stable connection between the vessel 100 and the engagement structure 101. In some examples, the conversion structure may comprise an interface for mounting the conversion structure to the ship, thereby facilitating the conversion process. Preferably, the ship comprises a counterpart to said interface. In some cases, such a counterpart may be added to the ship as a step of the conversion. The counterpart may comprise a mating interface, shaped to fit with a corresponding to a mating interface on the conversion structure. Having a conversion structure and a counterpart may facilitate the conversion of a ship or vessel, by reducing the time requirements and complexity of such an operation. For example, the counterpart may be easily installed onto or incorporated into the hull 102 of an existing vessel, and allow the conversion structure to be safely mounted thereon. In some examples, the conversion structure may be prefabricated, enabling to convert the ship for the installation of a wind power plant by conducting few process steps, i.e. not installing the conversion structure by successively adding several parts. In some examples, the conversion structure may be provided to a user along with a counterpart to facilitate conversion of a ship or vessel.

Although not illustrated in figure 22 or 23, the engagement structure 101 may be detachable from the vessel 100. In such cases, the engagement structure may be incorporated into a barge. Such a barge may be couplable to the vessel when necessary, and may be able to be decoupled, for example during installation of a wind turbine in a desired location offshore. The barge may be in the form of a buoyant U-shaped structure, comprising a gap for receiving a wind power plant. The barge may comprise two arms connected together by a structure configurable to couple and decouple from the hull of a vessel, e.g. at the stern of a vessel.

In some examples, the engagement structure 101 may be located at or coupled to the stern of the vessel 100. It should be appreciated however, that it may also be possible to provide some examples in which the engagement structure 101 is located at or coupled to another part of the vessel 100, such as at the bow of the vessel 100 or at the side of the vessel 100. In some examples, multiple engagement structures 101 may be present on or coupled to a vessel, e.g. the vessel having one U-shaped engagement structure 101 at the bow (e.g. a first engagement structure 101) and one U-shaped engagement structure 101 at the stern (e.g. a second engagement structure 101) giving the vessel an H-shape.

Figure 23 illustrates the example of a vessel 100 from Figure 1 from a perspective view. In this example, the engagement structure 101 is formed at the stern of the vessel 100. In other examples, the engagement structure 101 may be located at the bow or at a side of the vessel 100. In some examples, there may be more than one engagement structure 101, e.g. one engagement structure 101 at the bow and one engagement structure 101 at the stern. Here it can be seen that part of the U-shape of the engagement structure 101 is formed by two arms that extend from the hull 102, while another part of the U-shape is formed by the hull 102 itself. Although the arms are illustrated here as extending in a direction that is perpendicular to the longitudinal axis of the vessel 100, in other examples, the arms may be located at an angle to (e.g. obliquely) the longitudinal axis of the vessel 100.

Figure 24 illustrates an example of a wind power plant 110. As described above, the wind power plant 110 comprises a mast support structure 111. The mast support structure 111 may be or comprise a jacket, a truss structure, a tower or another type of elongated structure. In some examples, the mast support structure 111 comprises several legs. In this example, the mast support structure 111 comprises four legs, interconnected by truss structures, and arranged so as to have a substantially square cross section.

The wind power plant 110 comprises a wind turbine 121,122,123 comprising a turbine tower 121, a nacelle 122 and three turbine blades 123 mounted on the mast support structure 111. In some examples, there may be more or fewer blades mounted on the turbine tower 123, such as two blades or four blades.

The wind power plant 110 may comprise a collar 113 for transferring loads between the mast support structure 111 and the wind turbine 121,122,123. The collar 113 may be located at the interface between the turbine tower 121 and the mast support, and both the turbine tower 121 and the mast support structure 111 may be mounted to the collar 113. The collar 113 may additionally be designed for attachment to or engagement with the vessel 100, which will be described in detail below. The wind power plant 110 shown in Figure 3 may be installed at the sea floor 112, or may be installed in an underwater base which has been constructed to support the wind power plant 110. In this example, the collar 113 is located above the sea level 114, in other examples the collar 113 may be partly or completely submerged for all or at least some of the operation and/or installation of the wind turbine.

Figures 25 and 26 illustrate an example of a vessel 100 suitable for performing the methods described herein, illustrated from a side view and from a sectional rear view respectively. Here, the vessel comprises an engagement structure 101 formed at the stern of the vessel 100.

The engagement structure 101 comprises a height-adjustable coupling arrangement 104. The height-adjustable coupling arrangement 104 comprises four towers 103 and the coupling arrangement is movable along the height of the towers 103. The height-adjustable coupling arrangement 104 is movable between a raised position for transporting a wind power plant 110 and a lowered position for installation of said wind power plant 110 in a desired location. The height adjustable coupling arrangement may comprise a clamp, locking pin, a bolted connection profile and/or the like positioned on each of the towers 103. The height of the coupling arrangement 104 may be adjustable on a rack and pinion arrangement that may be at least partially housed within each of the towers 103, each of which may connect to a clamp, locking pin, bolted connection, or the like. In the case where the engagement structure is on a barge, the towers 103 may be decouplable from the vessel with the barge.

Coupling a wind power plant 110 to the height-adjustable coupling arrangement 104 permits vertical displacement of the wind power plant 110 relative to the vessel 100 by movement of the height-adjustable coupling arrangement 104 on or relative to the towers. As illustrated in Figures 27a-c, the height adjustable coupling arrangement 114 may couple to the collar 113 of the wind power plant 110, and as such the collar 113 may comprise a suitable profile for coupling the coupling arrangement 104 thereto.

The wind power plant 110 may be mounted to the height-adjustable coupling arrangement 104 and then may be able to be vertically displaced once mounted thereto. Preferably, the height-adjustable coupling arrangement 104 is lockable in the raised position (as is illustrated in Figure 27a) to restrict vertical displacement of both the height-adjustable coupling arrangement 104 and the coupled wind power plant 110. The raised position of the heightadjustable coupling arrangement 104 may be defined by the uppermost position of the coupling arrangement 104, or may be defined as the position of the height-adjustable coupling arrangement 104 that is necessary to permit transport of a wind power plant 110 when coupled to the coupling arrangement 104. The raised position of the height adjustable coupling arrangement 104, as illustrated in Figure 27a, may therefore be defined by the positioning of the wind power plant 100 relative to the vessel that best permits transport of the wind power plant 110 on the vessel 110. For example, it may be desirable to have the wind power plant 110 raised to a height such that the lower portion (e.g. the submerged portion) is not positioned so low in the water as to cause excessive drag, or to interact with subsea objects, and not positioned so high relative to the vessel 100 such that the vessel becomes unstable. The engagement structure 101 may be designed with a sufficient lifting height such as to allow the vessel 100 to lift a mast support structure 1,111 off an underwater base 3 as described above.

The vessel 100 may additionally comprise a locking arrangement 115. The locking arrangement may comprise a locking member positioned on or adjacent (for example, at the hull 102 near) one, or all, of the towers 103, and may assist to prevent movement of a wind power plant relative to the towers 103, and therefore relative to the vessel 100. The locking arrangement 115 may comprise a clamp, a locking pin, a bolted connection and/or the like. In this example, the locking arrangement 115 is located towards the base of the towers 103, and may be adjacent the engagement structure 101. In some examples, the locking arrangement 115 may be located on the engagement structure 101. The locking arrangement 115 may function to prevent horizontal movement of a wind power plant relative to the vessel 100, and optionally also assisting to prevent vertical movement of the wind power plant. The locking arrangement 115 may therefore assist to stabilise a wind power plant 110 that is mounted on the height-adjustable coupling arrangement 104.

Restricting displacement of the height-adjustable coupling arrangement 104 and the coupled wind power plant 110 relative to the vessel 100 may additionally reduce the impact of wave, weather or wind induced motion. Locking the height-adjustable coupling arrangement 104 in place may reduce swinging motions of the wind power plant 110, which may cause large stresses and shearing forces to be incident on the vessel (e.g. on the towers 103, on the engagement structure 103, on the locking arrangement 115, or the like) as the wind power plant 104 may have a large weight and a large leverage.

Figure 27c illustrates the wind power plant 110 with the height-adjustable coupling arrangement 104 in the lowered position. The lowered position of the height-adjustable coupling arrangement 104 for installing the wind power plant 110 may be a position lower than the raised position as the wind power plant 110 may be lowered to the sea/ocean floor at the installation site. The lowered position of the height-adjustable coupling arrangement 104 may therefore be variable dependent on the depth of the ocean floor below the vessel 100, and also on the height of the wind power plant 110. The lowered position may be defined as the height at which the wind power plant 110 is able to engage with the sea/ocean floor, or is able to engage with an underwater base. In some examples, the height-adjustable coupling arrangement may have a range of motion that extends past the raised and lowered positions, e.g. being movable above the raised position or below the lowered position to enable transport in more shallow waters or installation in deeper waters.

The height-adjustable coupling arrangement 104 may e.g. be driven by a drive arrangement such as a motor, in combination with pistons, chain gears, cog gears or winches. In another example, the height-adjustable coupling arrangement 104 may be or comprise a crane or another lifting device and the engagement structure 101 may comprise another number of towers 103 or no towers at all, e.g. in cases where the height-adjustable coupling arrangement 104 may be simply provided by suspension by a crane, and may be locked in place by the locking arrangement 115 located on the engagement structure 101. In some examples, the towers 103 may be comprise additional support structures such as or scaffolding.

As previously indicated height-adjustable coupling arrangement 104 is couplable to a wind power plant 110 by coupling means 105. The coupling means 105 may comprise a pin connection, a tenon and mortise connection, another type of male-female coupling, a grabbing tool like a hydraulic claw grabbing the wind power plant 110, pistons pressing against the wind power plant 110 or other well-known solutions. In this example, the coupling means 105 are coupling the wind power plant 110 to the height-adjustable coupling arrangement 104 by engaging at the collar 113. In another example, the coupling means 105 may engage the tower 121, the mast support structure 111 or any combination of these. In some examples, the height-adjustable coupling arrangement 104 may be couplable to the wind power plant 110 at a plurality of points.

In Figure 26, the height-adjustable coupling arrangement 104 is illustrated in a raised position with respect to the position illustrated in Figure 25, wherein the height-adjustable coupling arrangement 104 is illustrated in a lower position. The height-adjustable coupling arrangement 104 may be movable between a raised position for transporting a wind power plant 110 and a lowered position for installation of a wind power plant 110 in a desired location.

Figures 27a-c illustrate the process of lifting, transporting and installing a wind power plant 110 according to the disclosure from a sectional rear view on the vessel as in Figure 26. In Figure 27a illustrates a wind power plant 110 at a construction site being lifted for transport. The construction site may comprise an underwater base 3 as introduced above to facilitate construction of the wind power plant 110. In some examples, the construction site may be located close to the shore, e.g. close to a quay.

In this example, the vessel 100 approaches the constructed wind power plant 110 with the engagement structure 101 facing the wind power plant 110. The height-adjustable coupling arrangement 104 may then be moved (e.g. reconfigured) to an intermediate position to pick up the wind power plant 110, such as from a construction site. The intermediate position is located between the lowered position for picking up the wind power plant 110 and the raised position for transport of the wind power plant 110. The height-adjustable coupling arrangement 104 couples with the wind power plant 110 to enable lifting and transport of the wind power plant 110. In some examples, the vessel 100 may be ballasted prior to coupling the height-adjustable coupling arrangement 104 with the wind power plant 110 to reduce the draught thereof, and thereby increase the stability thereof. Once ballasting of the vessel is complete, the height-adjustable coupling arrangement 104 may then be adjusted to ensure that it is located to enable coupling with the wind power plant 110. In some cases, the position of the height-adjustable coupling arrangement 104

In this example, the height-adjustable coupling arrangement 104 comprises a pin connection, which connects to receiving parts at the collar 113 of the wind power plant 110 from below. In another example, the height-adjustable coupling arrangement 104 may form the coupling by other means, for example by the means described above. After forming the coupling (herein the height-adjustable coupling arrangement 104 needs to be moved upwards to move the pins of the pin connection in the respective receiving parts at the collar 113 of the wind power plant 110), the height-adjustable coupling arrangement 104 is moved to a raised position for transport of the wind power plant 110. In this example, the raised position can be a few meters above the position in which the wind power plant 110 was picked up, e.g.1 or 2 meters. In another example, the raised position may be more than 2 meters above the pickup position. In yet another example, the raised position may be less than 2 meters above the pick-up position or less than 1 meter above the pick-up position if sufficient for the wind power plant 110 to be moved off the base 3. Depending on the wind and waves, the structural composition of the wind power plant 110 (e.g. the height of the center of mass) and the water depth along the transport route to the installation site, a suitable elevation of the height-adjustable coupling arrangement 104 and the coupled wind power plant 110 above the pick-up position may be chosen. In some examples, other factors may have an influence on the height of the raised position, e.g. safety regulations, draught of the vessel 100 or personal preference of the installation personnel.

Figure 27b shows the transport of the wind power plant 110 by the vessel 100. In this example, the vessel is located in in an offshore location and the lowest point of the wind power plant 110 is 18 meters below the sea level 114. Referring to Figure 27a, the water depth of the installation site was 20 meters, enabling the transport of the wind power plant 110 by lifting the wind power plant 110 by only 2 meters. In another example the water depths may be more shallow or deeper. In some examples, the wind power plant 110 may be lifted to another elevation, e.g. because the water depth at the construction or installation site or the water depth along the transport route to the installation site has another value compared to the illustrated example.

Figure 27c shows the installation of the wind power plant 110 at the installation site. In this example, the water depth at the installation site is 70 meters. In another example, the water depth may differ and may have an effect on the size and design of the wind power plant 110 and the vessel 100, for example the height-adjustable coupling arrangement 104 may have a larger range of motion. The installation of the wind power plant 110 may comprise fixing the wind power plant 110 to the ocean floor, e.g. by fixing the wind power plant 110 to a preconstructed installation base.

In some examples, the height-adjustable coupling arrangement 104 may be motion compensated to compensate relative motion of the wind power plant 110 and the vessel 100 due to wind, waves and weather. As previously described, in some examples, the vessel 100 may comprise a locking arrangement 115 to restrict motion of the wind power plant 110 relative to the vessel 100. In some examples, the locking arrangement 115 may be configured to restrict motion of the wind power plant 110 in the vertical plane, e.g. by providing a stabilising force (e.g. by pressing or pushing) from multiple sites against the wind power plant 110 using pistons, biasing members, or the like. In some examples, the locking arrangement may be configured to prevent motion of the wind power plant 110 relative to the vessel 100. Alternatively, or in addition to the above and as briefly described previously, the locking arrangement may comprise means to grab the wind power plant 110 to prevent motion thereof, e.g. clamps, robotic arms or the like. In some examples, the locking arrangement 115 and the wind power plant 110 may comprise arrangement to permit coupling of a wind power plant 110 thereto, which may be similar to the engagement of the height-adjustable coupling arrangement 104 and the wind power plant 110, to provide a rigid connection between the vessel 100 and the wind power plant 110 during the transport, the rigid connection being releasable when installing the wind power plant 110. In some examples, the locking arrangement may comprise a pin connection or corresponding engagement surfaces. The locking arrangement may preferably be activated after lifting the height-adjustable coupling arrangement 104 and the wind power plant 110 from the intermediate pick-up position to the raised position to lock the movement of the wind power plant 110 during the transport. Further, the locking arrangement 115 may be decoupled after transporting the wind power plant 110 to the desired location, prior to commencing the installation, i.e. lowering the height-adjustable coupling arrangement 104 with the wind power plant 100 to the lowered position for installation.

In some examples, the wind power plant 110 may be transported semi-submerged as shown in the Figures. This enables the center of mass of the transported wind power plant 110 to be lowered, reducing the impact of rolling or rocking motions of the wind power plant 110 induced by wind, waves or weather on the stability of the vessel 100. The structural stability of the vessel 100 may be improved, i.e. requiring a reduced structural stability of the vessel to transport a wind power plant 110. Also the stability of the vessel 100 may be improved.

In some examples, the vessel 100 may comprise a ballasting arrangement to compensate for the mass of the wind power plant 110. When lifting or installing the wind power plant 110, the weight distribution of the vessel 100 may shift. A ballasting arrangement may be used to compensate for the alteration of the weight distribution when picking up/installing the wind power plant 110. Depending on the position of the engagement structure 101, the ballasting arrangement may shift its ballast. For example, the ballasting system may use water movable along the ship and the engagement structure 101 may be located at the stern.

When picking up the wind power plant 110, the wind power plant 110 induces additional weight at the stern. The ballasting system may be used to pump water to the bow of the vessel 100 to secure an upright position of the vessel 100 during pick-up and transport (e.g. to counteract the increased weight loading on the vessel 100 when the wind power plant 110 is mounted thereon). When installing the wind power plant 110, i.e. when the weight of the wind power plant 110 is released from the vessel 100 (e.g. gradually released), e.g. when the wind power plant 110 touches the ocean floor, the ballasting system may shift the water to a more aft position to compensate for the reduction in weight at the stern, thereby ensuring stability of the vessel throughout the installation process.

The ballasting system may be used in combination with the height-adjustable coupling arrangement 104 to continuously vary weight distribution of the vessel, to ensure improved stability throughout operation. For example, the ballasting system and the height-adjustable coupling arrangement 104 may be used to ensure that the centre of gravity of the vessel 100 remains constant, or relatively constant, throughout operation by carefully shifting the ballast weight of the vessel. As such, the vessel may be used to install a wind power plant 110 as illustrated, in a more controlled and stable way than previously known in the art. In examples where the engagement structure 101 is provided on a barge, installation of a wind power plant 110 may comprise an additional step of decoupling the barge from the vessel for installation of the wind power plant 110. Once decoupled, the barge may comprise the engagement structure 101 and the towers 103 with the wind power plant 110 coupled thereto with the height-adjustable coupling arrangement 104 in the raised position. The barge may then be moved to the desired installation location of the wind power plant 110, and the wind power plant may be lowered to engage the sea/ocean floor, or an underwater base. Since the barge is smaller than the vessel, there may be reduced or eliminated need to shift the weight of the barge during installation operations.

Advantageously, with methods according to the examples described herein, it may be possible to carry out various operations relating to the construction and installation of bottomfixed, offshore wind power plants in a safer, more efficient and/or simpler manner. For example, lifting operations offshore and at the installation site 11, such as lifting of heavy wind turbine components, can be reduced or eliminated.

By constructing the wind power plant 10 on an underwater base 3, handling the wind power plant 10 for transport offshore may be simplified. A challenge in such operations can be the high weight of the wind turbine parts such as the nacelle, and the high centre of gravity, making transport of complete wind power plants 10 challenging. By providing the wind power plant 10 on the base 3, it can be picked up by a barge or vessel 5 with the centre of gravity of the wind power plant 10 lowered compared to for example handling it completely assembled from the shoreside 2.As will be appreciated when reading the disclosure herein, advantages of the methods described may be realised individually and by the use of only some of the method steps described above. The invention is not limited by the embodiments described above; reference should be had to the appended claims.

Further inventive aspects and embodiments according to the present disclosure is outlined in the following clauses.

1. A method of constructing a wind power plant (10), the method comprising:

providing a mast support structure (1);

positioning the mast support structure (1) on an underwater base (3) adjacent a shoreside (2);

with the mast support structure (1) positioned on the base (3), mounting a wind turbine generator (4) onto the mast support structure (1) to form a wind power plant (10);

picking up the wind power plant (10) with a barge or vessel (5);

transporting the wind power plant (10) from the base (3) to an installation site (11); and

landing and fixing the mast support structure (1) to a sea floor (12) at the installation site (11).

2. A method according to any preceding clause, wherein the step of providing a mast support structure (1) comprises building the mast support structure (1) at least partly on the shoreside (2).

3. A method according to any preceding clause, wherein the step of providing a mast support structure (1) comprises building the mast support structure (1) fully on the shoreside (2) and subsequently positioning the mast support structure (1) on the underwater base (3) by moving the mast support structure (1) from the shoreside (2) to the base (3).

4. A method according to any preceding clause, wherein the step of providing a mast support structure (1) comprises building the mast support structure (1) partially on the shoreside (2) and partially on the base (3).

5. A method according to any preceding clause, wherein the step of providing a mast support structure (1) comprises providing the mast support structure (1) from a remote location and positioning the mast support structure (1) on an underwater base (3).

6. A method according to any preceding clause, wherein the step of transporting the wind power plant (10) from the shoreside (2) to an installation site (11) is carried out with at least a part of the mast support structure (1) submerged.

7. A method according to the preceding clause, wherein the submerged part makes up at least half of the height of the mast support structure (1), at least 60% of the height of the mast support structure (1), or at least 75% of the height of the mast support structure (1).

8. A method according to any preceding clause, wherein the step of transporting the wind power plant (10) comprises transporting the wind power plant (10) with the mast support structure (1) submerged to a water depth which is lower than its depth when positioned on the base (3).

9. A method according to any preceding clause, wherein the step of picking up the wind power plant (10) with a barge or vessel (5) comprises lifting the wind power plant (10) off the base (3) with the barge or vessel (5).

10. A method according to any preceding clause, wherein the step of picking up the wind power plant (10) with a barge or vessel (5) comprises fixing the wind power plant (10) in relation to the barge or vessel (5) and adjusting the draught of the barge or vessel (5) to lift the wind power plant (10) off the base (3).

11. A method according to any preceding clause, wherein the step of building a mast support structure (1) at the shoreside (2) comprises building the mast support structure (1) by use of a land-based crane (6).

12. A method according to any preceding clause, wherein the step of positioning the mast support structure (1) on the underwater base (3) is carried out by use of a land-based crane (6).

13. A method according to any preceding clause, wherein the step of mounting a wind turbine generator (4) onto the mast support structure (1) to form a wind power plant (10) comprises mounting the wind turbine generator (4) onto the mast support structure (1) using a land-based crane (6).

14. A method according to any preceding clause, wherein the step of mounting a wind turbine generator (4) onto the mast support structure (1) to form a wind power plant (10) comprises mounting at least one tower section (21), at least one nacelle section (22) and at least one turbine blade (23) onto the mast support structure (1).

15. A method according to any preceding clause, wherein at least one of the steps of mounting at least one tower section (21), at least one nacelle section (22) and at least one turbine blade (23) is carried out by use of a land-based crane (6).

16. A method according to any preceding clause, wherein all the steps of mounting at least one tower section (21), at least one nacelle section (22) and at least one turbine blade (23) is carried out by use of a land-based crane (6).

17. A method according to any preceding clause, wherein the step of landing and fixing the mast support structure (1) on and to the sea floor (12) at the installation site (11) comprises landing and fixing the mast support structure (1) on and to a prepared foundation (31).

18. A method according to any preceding clause, wherein the prepared foundation (31) comprises a piled foundation arranged to engage a lower part of the mast support structure (1).

19. A method according to any preceding clause, wherein the step of landing and fixing the mast support structure (1) on and to the sea floor (12) at the installation site (11) comprises lowering the wind power plant (10) from the barge or vessel (5).

20. A method according to any preceding clause, wherein the step of landing and fixing the mast support structure (1) on and to the sea floor (12) at the installation site (11) comprises adjusting the draught of the barge or vessel (5) to lower the wind power plant (10) together with the barge or vessel (5) to land the mast support structure (1) on the sea floor (12).

21. A method according to any preceding clause, wherein the submerged part of the mast support structure (1), when positioned on the base (3), makes up at least half of the height of the mast support structure (1), at least 60% of the height of the mast support structure (1), or at least 75% of the height of the mast support structure (1).

22. A method according to any preceding clause, wherein the underwater base (3) is arranged at a water depth of more than 20m, more than 30m or more than 40m. 23. A method according to any preceding clause, wherein the step of picking up the wind power plant (10) with a barge or vessel (5) comprises positioning the mast support structure (1) in a receptacle (34) on the barge or vessel (5).

24. A method according to the preceding clause, wherein the receptacle (34) is arranged to support the mast support structure (1) at least at two horizontally opposing sides.

25. A method according to any preceding clause, wherein the step of transporting the wind power plant (10) from the base (3) to the installation site (11) comprises supporting the mast support structure (1) in the receptacle (34) while transporting the wind power plant (10).

26. A vessel (100) for the transport and installation of a wind power plant (110), the vessel comprising:

a hull comprising an engagement structure (101) for engaging a wind power plant (110), the engagement structure (101) comprising a height-adjustable coupling arrangement (104);

the height-adjustable coupling arrangement 104 being configurable to be coupled to a wind power plant (110) and permit vertical displacement of a wind power plant (110) relative to the vessel (100) between a raised position for transporting a wind power plant (110) and a lowered position for installation of a wind power plant (100) in a desired location; and

wherein in the raised position, the height-adjustable coupling arrangement (104) is lockable to restrict vertical and horizontal displacement of both the height-adjustable coupling arrangement (104) and a coupled wind power plant (110), so as to transport a coupled wind power (110) plant in a semi-submerged state on the vessel (100). 27. The vessel (100) according to any preceding clause, comprising a locking arrangement for restricting movement of a wind power plant (110) relative to the vessel (100).

28. The vessel (100) according to any preceding clause, wherein the locking arrangement is configured to prevent movement of the wind power plant (110) relative to the vessel (100).

29. The vessel 100 according to any preceding clause, wherein the height-adjustable coupling arrangement (104) is couplable to a wind power plant (110) at a plurality of points.

30. The vessel (100) according to any preceding clause, comprising a wind power plant (110) having a mast support structure (111), wherein the height-adjustable coupling arrangement (104) is couplable to the mast support structure (111).

31. The vessel (100) according to any preceding clause, wherein the mast support structure (111) comprises four legs, and the vessel (100) comprises a locking arrangement for restricting movement of the wind power plant relative to the vessel, and the locking arrangement is lockable to each of the four legs of the mast support structure (111).

32. The vessel (100) according to any preceding clause, wherein the mast support structure (111) comprises a collar (113) for coupling to the height-adjustable coupling arrangement (104).

33. The vessel (100) according to any preceding clause, wherein the collar (113) is configured to transfer load between a wind turbine (110) and the mast support structure (111).

34. The vessel (100) according to any preceding clause, wherein the engagement structure (101) comprises a U-shaped portion arranged for receiving the mast support structure (111).

35. The vessel (100) according to any preceding clause, wherein the U-shaped portion defines the stern of the vessel (100).

36. The vessel (100) according to any preceding clause, wherein the height-adjustable coupling arrangement (104) is located on a plurality of towers (103).

37. The vessel (100) according to any preceding clause, wherein the plurality of towers (103) is located on the U-shaped portion of the stern of the vessel (100).

38. The vessel (100) according to any preceding clause, wherein the height-adjustable coupling arrangement (104) comprises a heave compensation system.

39. The vessel (100) according to any preceding clause, comprising a ballasting arrangement.

40. The vessel (100) according to any preceding clause, wherein the height-adjustable coupling arrangement comprises an intermediate position between the raised position and the lowered position, for engaging the wind power plant (110) at a pickup location.

41. The vessel (100) according to any preceding clause, wherein the vessel is selfpropelled.

42. A method for transport and installation of an offshore wind power plant (110), the method comprising:

providing a vessel (100) for the transport and installation of the wind power plant (110);

mounting the wind power plant (110) to a height-adjustable coupling arrangement (104) on the vessel (100);

transporting the wind power plant (110) in a semi-submerged state to a desired location with the height-adjustable coupling arrangement (104) in a raised position in which vertical and horizontal displacement of the heightadjustable coupling arrangement (104) and the wind power plant (110) is restricted; and

installing the wind power plant (110) in a desired location by moving the height-adjustable coupling arrangement (104) to a lowered position.

43. The method according to any preceding clause, comprising ballasting the vessel (100) to reduce the draught thereof, prior to mounting the wind power plant (110) thereon.

44. The method according to any preceding clause, comprising moving the ballast of the vessel (100) to a forward position as the wind power plant (110) is mounted thereon.

45. The method according to any preceding clause, comprising configuring the heightadjustable coupling arrangement (104) to an intermediate position for mounting the wind power plant (110) thereon.

46. The method according to any preceding clause, comprising moving the heightadjustable coupling arrangement (104) from the intermediate position to the raised position, with the wind power plant (110) mounted thereon.

47. The method according to any preceding clause, comprising restricting movement of the wind power plant (110) relative to the vessel with a locking arrangement prior to and/or while transporting the wind power plant (110).

48. The method according to any preceding clause, comprising unlocking the locking arrangement to permit movement of the wind power plant (110) relative to the vessel (100) prior to installing the wind power plant (110).

49. The method according to any preceding clause, comprising moving the ballast of the vessel to an aft position as the wind power plant (110) is installed in a desired location.

50. A conversion structure for converting a vessel for the transport and installation of a wind power plant (110), comprising:

an interface for mounting the conversion structure to the vessel;

an engagement structure (101) for engaging a wind power plant (110), the engagement structure (101) comprising a height-adjustable coupling arrangement (104);

the height-adjustable coupling arrangement (104) being configurable to be coupled to a wind power plant (110), and permit vertical displacement of a wind power plant (110) relative to the vessel (100) between a raised position for transporting a wind power plant (110) and a lowered position for installation of a wind power plant (110) in a desired location; and

wherein in the raised position, the height-adjustable coupling arrangement (104) is lockable to restrict vertical and horizontal displacement of both the height-adjustable coupling arrangement (104) and a coupled wind power plant (110), so as to transport a coupled wind power plant (110) in a semisubmerged state on the vessel (100).

51. A method for converting a vessel for transport and installation of a wind power plant (110), the method comprising:

providing a vessel; and

mounting a conversion structure according to clause 50 on the vessel.

52. The method according to any of clauses 1-25 or 42-49 wherein the method is carried out using a vessel according to any of clauses 26-41 or a vessel having a conversion structure according to clause 50.

Claims

1. A vessel (100) for the transport and installation of a wind power plant (110), the vessel comprising:

wherein in the raised position, the height-adjustable coupling arrangement (104) is lockable to restrict vertical and horizontal displacement of both the height-adjustable coupling arrangement (104) and a coupled wind power plant (110), so as to transport a coupled wind power (110) plant in a semi-submerged state on the vessel (100).

2. The vessel (100) according to claim 1, comprising a locking arrangement for restricting movement of a wind power plant (110) relative to the vessel (100).

3. The vessel 100 according to any preceding claim, wherein the height-adjustable coupling arrangement (104) is couplable to a wind power plant (110) at a plurality of points.

4. The vessel (100) according to any preceding claim, wherein the engagement structure (101) comprises a U-shaped portion arranged for receiving the mast support structure (111).

5. The vessel (100) according to any preceding claim, wherein the U-shaped portion is defined by the stern of the vessel and two sponsons extending from the hull (102).

6. The vessel (100) according to any preceding claim, wherein the height-adjustable coupling arrangement (104) is located on a plurality of towers (103).

7. The vessel (100) according to any preceding claim, wherein the plurality of towers (103) is located on the U-shaped portion of the stern of the vessel (100).

8. The vessel (100) according to any preceding claim, wherein the height-adjustable coupling arrangement comprises an intermediate position between the raised position and the lowered position, for engaging the wind power plant (110) at a pickup location.

9. A method for transport and installation of an offshore wind power plant (110), the method comprising:

10. The method according to claim 9, comprising configuring the height-adjustable coupling arrangement (104) to an intermediate position for mounting the wind power plant (110) thereon.

11. The method according to any of claims 9-10, comprising moving the height-adjustable coupling arrangement (104) from the intermediate position to the raised position, with the wind power plant (110) mounted thereon.

12. The method according to any of claims 9-11, comprising restricting movement of the wind power plant (110) relative to the vessel with a locking arrangement prior to and/or while transporting the wind power plant (110).

13. The method according to any of claims 9-12, comprising unlocking the locking arrangement to permit movement of the wind power plant (110) relative to the vessel (100) prior to installing the wind power plant (110).