Method of installing a monopile as foundation for an offshore wind turbine using a jack-up vessel

Abstract

Method of installing a monopile as foundation for a wind turbine at an offshore location, comprising: providing, at the offshore location, a jack-up vessel with legs supported on a seafloor and a hull that is in a jacked-up state with respect to the legs to be above the waterline, wherein, in plan view, the legs together define a legs section of the hull where the hull structurally interconnects the legs, and wherein, in plan view, a perimeter of the hull is shaped with a recess extending towards the legs section; providing, at the offshore location, a monopile for use as a foundation for a wind turbine; lowering the monopile in an upright orientation through the recess to a seafloor below the recess; and fixating the monopile in the seafloor to form the foundation.

Description

[0001] Title: Method of installing a monopile as foundation for an offshore wind turbine using a jack-up vessel

[0002] FIELD

[0003] The invention relates to a method of installing a monopile as foundation for a wind turbine at an offshore location, as well as to a jack-up vessel for use in the method.

[0004] BACKGROUND

[0005] Methods of installing a monopile as foundation for a wind turbine at an offshore location using a jack-up vessel are known as such. In a known method, the monopile that is to form the foundation is transported to the offshore location in a lying orientation on a main deck of the jack-up vessel. At the offshore location, the legs are jacked downwards, i.e. lowered with respect to the hull, so that the hull forms a stable platform, wherein the hull is elevated above the waterline. Then, the monopile is brought to an upright orientation and lowered to the sea bed in its upright orientation, typically using a crane of the jack-up vessel. Once on the seafloor, the monopile is fixated, for example by hammering the monopile into the seafloor, thus forming the foundation.

[0006] It has been found that the known method tends to pose challenges with respect to the jack-up’s structural integrity as well as the integrity of its support on the seafloor. In practice, such challenges may pose limitations on the installation conditions such as environmental conditions in which monopiles can be installed, as well as on types of monopiles for which installation can be performed safely and efficiently. Such limitations are generally undesired, in particular in view of the ongoing need to install more and more offshore wind turbines as part of the transition towards so- called clean energy. In other words, there is a desire to increase the installation capacity of jack-up vessels. Meanwhile, there is a desire to improve the effective cargo capacity of the jack-up vessel, for example to be able to carry more and / or larger monopiles for subsequent installation using the jack-up vessel. One possible way to increase the installation and cargo capacity would be to correspondingly increase the size of the jack-up vessel, but this may have a disadvantage of correspondingly increasing costs. In a more general sense, there is thus a desire to be able to install relatively large monopiles under a relatively wide range of installation conditions with a relatively moderately sized jack-up vessel.

[0007] SUMMARY

[0008] An object of the invention is to at least partly address at least one of the above-described problems or a related problem.

[0009] Thereto, an aspect of the invention provides a method of installing a monopile as foundation for a wind turbine at an offshore location. The method comprises: providing, at the offshore location, a jack-up vessel with legs supported on a seafloor and a hull that is in a jacked-up state with respect to the legs to be above the waterline. In plan view, the legs together define a legs section of the hull where the hull structurally interconnects the legs, and wherein, in plan view, a perimeter of the hull is shaped with a recess extending towards the legs section. The method further comprises: providing, at the offshore location, a monopile for use as a foundation for a wind turbine; lowering the monopile in an upright orientation through the recess to a seafloor below the recess; and fixating the monopile in the seafloor to form the foundation.

[0010] By lowering the monopile through the recess of the hull, loading of the jack-up vessel during the installation of the monopile can be relatively advantageous in terms of preserving structural integrity of the jack-up vessel and integrity of its support on the seafloor. In particular, it is considered that loads such as from lifting the monopile can thereby be transferred from the monopile to the legs of the jack-up vessel in a structurally favorable manner. Meanwhile, a relatively large deck area can be utilized for carrying cargo such as monopiles to be installed.

[0011] By contrast, in known methods, the monopile is typically lowered outboard beyond an outer port side or outer starboard side of the hull of the jack-up vessel. Compared to such known methods, the method of the present invention can advantageously enable installation of larger monopiles and / or installation of monopiles in less favorable environmental conditions, in particular with a similar size jack-up vessel.

[0012] During the fixating of the monopile in the seafloor, the monopile preferably continues to extend through the recess, wherein the arrangement of the recess may continue to provide advantages, as explained further elsewhere herein. Thereafter, the jack-up vessel may retract its legs and then sail away from the installed monopile, causing the installed monopile to leave the recess while remaining installed. The jack-up vessel may then sail to a subsequent offshore location for installation of a further monopile, for example in essentially the same manner as for the earlier monopile.

[0013] It shall be appreciated that in the present context, the term upright orientation may be understood as a generally vertical orientation but without necessarily requiring exact verticality. Thus, for example, deviations of up to 5, 10, or 15 degrees from exact vertical may be included within the term upright as used herein. In practice, such upright orientations are sometimes also referred to as vertical orientations.

[0014] Optionally, the lowering of the monopile comprises use of a crane of the jack-up vessel, which crane has a base that is at and around one of the legs, in particular to be primarily supported by the one leg during use.

[0015] Advantageously, such a crane can lift relatively heavy loads such as relatively large monopiles in a safe and stable manner at a suitable reach, transferring such loads to the seabed primarily via the one leg where the base of the crane is situated, wherein additional stability against platform overturning can be provided by the other legs via the hull. Optionally, in plan view, the recess is arranged at a side of the legs section that is at least co-defined by the one leg where the base of the crane is situated, in particular a side corresponding to a stern of the hull.

[0016] In this way, the recess can be relatively close to the base of the crane to be in a relatively favorable range for the crane, facilitating stable suspension of the monopile from the crane during lowering of the monopile through the recess. By arranging the recess at the stern, the recess can be relatively close to an area between two of the legs, promoting load distribution between those legs. Meanwhile, in particular at the stern, the recess need not extend into the legs section, which may thus be utilized for other purposes such as holding monopiles during transport. Also, structural integrity of the hull regarding load paths between the legs thus need not be affected by the recess. In particular, longitudinal and transverse bulkheads may thus extend throughout the leg section, as is customary for jack-up vessels, to contribute to said structural integrity.

[0017] Optionally, prior to the lowering of the monopile, the monopile is adjusted from a lying orientation to the upright orientation.

[0018] Thereby, the monopile can be transported to the offshore location in a lying orientation before being installed. In the lying orientation, it may be easier to support the monopile in a sufficiently stable manner during transport.

[0019] It shall be appreciated that in the present context, the term lying orientation may be understood as a generally horizontal orientation but without necessarily requiring exact horizontality. Thus, for example, deviations of up to 5, 10, or 15 degrees from exact horizontal may be included within the term lying as used herein. In practice, such lying orientations are sometimes also referred to as horizontal orientations.

[0020] Optionally, the adjustment is performed using the crane.

[0021] Thus, the crane can be utilized for multiple actions during the installation. Moreover, the lowering of the monopile using the crane may thus be performed relatively quickly after the monopile has been adjusted to the upright orientation.

[0022] Optionally, during the adjustment, the monopile is connected to the jack-up vessel by a hinging mechanism that determines a hinging axis for the adjustment.

[0023] Such a hinging mechanism is known as such, sometimes also being called an upending tool, and may advantageously be used in the context of the present invention. In particular, by determining the hinging axis for the adjustment, the hinging mechanism can facilitate a stable adjustment using the crane. For example, whereas the crane may engage the monopile at an upper end thereof, the hinging mechanism may engage the monopile close to a lower end thereof, in particular restricting movement of the monopile with respect to the hull to rotation about the determined rotation axis.

[0024] Optionally, the hinging mechanism and / or the hinging axis is arranged at a side of the legs section that is at least co-defined by the one leg where the base of the crane is situated, in particular a side corresponding to a port side or starboard side of the hull.

[0025] In this way, the monopile can be relatively close to the base of the crane at the end of the adjustment, to be in a relatively favorable range for the crane, facilitating relatively stable suspension of the monopile from the crane, in particular for subsequently lowering and / or otherwise moving the monopile in the upright orientation while being suspended from the crane. The hinging axis preferably extends substantially parallel to the longitudinal axis of the hull, as explained elsewhere herein.

[0026] Optionally, prior to the adjustment, the monopile in the lying orientation is arranged on a deck of the jack-up vessel, in particular to extend mainly transverse with respect to a longitudinal axis of the hull. The deck is preferably a main deck of the jack-up vessel.

[0027] Thereby, a same jack-up vessel may be used for transport of the monopile to the offshore location and for installation of the monopile at the offshore location. In particular, in the lying orientation on the deck, the monopile may be transported relatively securely at sea. By a mainly transverse orientation of the lying monopile with respect to the hull, the monopile may extend outside a perimeter of the hull, for example on a port side and / or a starboard side, thereby occupying relatively little deck space compared to its size. Meanwhile, the monopile may be caused to be engaged by the hinging mechanism relatively easily when the hinging axis is arranged at a port side or starboard side of the hull. Preferably, the hinging axis determined by the hinging mechanism then extends substantially parallel to the longitudinal axis of the hull. Thereby, the monopile may be adjusted to the upright orientation directly from the mainly transverse orientation.

[0028] Optionally, prior to the lowering of the monopile, in particular after the adjustment, the monopile is moved while being in the upright orientation, in particular to above the recess from an area at a distance from the recess, such as an area where the monopile was adjusted to the upright orientation from a lying orientation.

[0029] In this way, the monopile may first be adjusted to the upright orientation e.g. at a port side or starboard side, and subsequently be lowered through the recess e.g. at the stern, allowing respective advantages of such different locations for the adjustment and lowering to be combined.

[0030] Optionally, the moving of the monopile in the upright orientation is performed using the crane, wherein preferably the moving comprises slewing of the crane while the monopile is suspended from the crane.

[0031] Thus, the crane may be utilized still further, wherein in particular the slewing can facilitate movement between the preferred different locations for the adjustment and the lowering.

[0032] During at least some of the slewing, the monopile may be suspended outside a perimeter of the hull. Thus, the slewing may comprise slewing in an outboard manner, which can contribute to safety. Nevertheless, during at least some of the slewing, the monopile may be suspended within the perimeter of the hull, e.g. to cross over a section of the hull from a starboard side or port side of the hull to above the recess. Such crossing over a section of the hull may facilitate that the crane is operated within a suitable reach, in particular in case of a relatively heavy monopile.

[0033] During the slewing, a distance between the monopile and the base of the crane in plan view may be varied, in particular between a smaller distance when the monopile is suspended outside and adjacent the perimeter of the hull and a larger distance when the monopile is suspended at least partly within the perimeter of the hull. In this way, the crane can be loaded relatively favorably, in particular during outboard slewing of a relatively heavy monopile, while interference with objects on deck can be limited.

[0034] The slewing of the crane with the monopile suspended therefrom is done to transport the monopile from a location where the monopile is upended towards a location where the monopile is lowered into the seafloor. The location where the monopile is upended is typically at a side of the hull such as the port side or the starboard side. Advantageously, the monopile is upended using the hinging mechanism or any other upending tool. In the hinging mechanism, the monopile can be transferred to an upright position. The adjustment from the lying position to the upright position is typically being done while the monopile is connected to the crane. So, when the monopile is in the hinging mechanism it may be supported by the crane as well. The hinging mechanism may then open, or disengage from the monopile, such that the monopile now becomes fully suspended by the crane. Then, a trajectory of moving the monopile in the upright position from the location of upending to the location of lowering may start. The moving of the monopile is done using the crane, in particular by slewing of the crane while the monopile is suspended from the crane. The trajectory may comprise a first part in which the monopile is suspended outside of the perimeter of the hull, and a second part of the slewing during which at least partially the monopile is suspended within the perimeter of the hull. During the first part of the trajectory the monopile may move alongside the hull, typically along the same side at which the upending location is. During the first part of the trajectory, the monopile is being moved from the location of the upending alongside the hull towards the side of the hull provided with the recess. Advantageously, the recess is arranged at a side of the hull having the leg around which the base of the crane is situated, e.g. at the stern side or the bow side. Advantageously, the location of upending of the monopile is at a side of the hull having the leg around which the base of the crane is situated which is also transverse to the side having the recess. So, during a first part of the trajectory, the monopile can be moved from the upending location towards a location near the base of the crane at the same side of the hull. During this first part of the trajectory, the monopile may extend partially through the waterline or may be above the waterline. During the first part of the trajectory, movement of the monopile is induced by slewing of the crane. Also, during the first part of the trajectory, a distance between the monopile and the base of the crane in plan view is varied. By varying the distance between the monopile and the base of the crane during slewing, the stability and / or load distribution of the legs and / or the jack-up can be improved. Further, it may be achieved that the monopile may remain or may come relatively close to the perimeter of the hull. Upon reaching a location near the base of the crane, the crane may lift the monopile until the monopile is at a height above the deck of the hull. During at least a part of the second part of the trajectory, the monopile may move inside the perimeter of the hull, preferably above the deck of the hull. The distance between the monopile and the base of the crane may be, generally speaking, larger during the second part of the trajectory than during the first part of the trajectory. Of course, since the distance during the trajectory varies, it may be possible that during some parts of first part of the trajectory the distance may be larger than during some parts of the second part of the trajectory. For example, the upending location, as a starting location of the first part of the trajectory, may be further away than the recess, as an end location of the second part of the trajectory, from the base of the crane, depending on the geometry of the jack-up vessel.

[0035] By moving the monopile within the perimeter of the hull during at least a part of the second part of the trajectory, the monopile may approach the recess in a safe manner. While the monopile approaches the recess, the distance between the monopile and the crane base may vary, thereby contributing to stability and / or load distribution of the jack-up vessel during operations. When the monopile has reached a location above the recess, the monopile can be lowered into the recess, typically in a pile guiding tool or a pile gripper, towards the seafloor and can be fixated into the seafloor.

[0036] Optionally, the lowering and / or the fixating comprises hammering the monopile into the seafloor.

[0037] Hammering of monopiles into the seafloor is known as such, and may advantageously be applied in the present context. To that end, the crane may be utilized still further, wherein a hammer tool may be suspended from the crane to be placed on top of the upright monopile extending through the recess.

[0038] Optionally, the recess is arranged aft of the legs.

[0039] Thereby, as alluded to elsewhere herein, a deck space of the legs section may be utilized for other purposes such as transportation of monopiles.

[0040] Optionally, in plan view, during the lowering of the monopile, the monopile is arranged within the recess.

[0041] In this way, force transmission between the monopile and the hull can be facilitated along a relatively large circumferential range of the monopile. Optionally, at least during the lowering and / or fixating of the monopile, a pile positioning tool for the monopile is provided at the recess, the pile positioning tool being arranged to transmit lateral force between the monopile and the hull for subsequent force transmission into the legs, wherein the method preferably comprises lateral force transmission between the monopile and the hull via the pile positioning tool, in particular during the lowering and / or fixating.

[0042] Pile positioning tools are known as such in various forms, sometimes also called pile guiding tools or pile grippers, and may advantageously be applied in the present context.

[0043] Optionally, the pile positioning tool is adjustable with respect to the hull for adjustment of a position and / or orientation of the monopile with respect to the hull at the recess, in particular other than a vertical position adjustment. Then, preferably, the method comprises, for example before and / or during the lowering and / or fixating of the monopile, adjustment of the pile positioning tool with respect to the hull for adjustment of a position and / or orientation of the monopile with respect to the hull, in particular other than a vertical position adjustment.

[0044] Optionally, the adjustment of the position and / or orientation of the monopile with respect to the hull using the pile positioning tool comprises at least one of: adjustment of a position of the monopile with respect to a forward-aft and / or port-starboard direction of the hull; adjustment of a verticality of the monopile; rotation of the monopile about its main axis.

[0045] Optionally, the pile positioning tool is adjustable to accommodate different shapes and / or sizes of monopiles.

[0046] Optionally, the pile positioning tool is adjustable to accommodate different hammering tools for the optional hammering of the monopile.

[0047] Such optional adjustabilities are known as such for pile positioning tools, and may advantageously be applied in the present context. Optionally, the pile positioning tool is adjustable to release the pile positioning tool from the monopile to allow the jack-up vessel to move away from the monopile after the fixating of the monopile to the seafloor.

[0048] In this way, the pile positioning tool can advantageously remain in place with respect to the hull after installation of the monopile has been completed.

[0049] Optionally, the pile positioning tool is arranged at least partly within the recess, in particular being connected to the hull at least at two mutually opposite sides of the recess, for example at the two mutually opposite sides and at a third side of the recess that is between the two mutually opposite sides.

[0050] Thereby, the pile positioning tool can be structurally connected to the hull in a relatively strong and stable manner, in particular obviating the need for excessive reinforcement structures for the pile positioning tool sometimes applied in known methods. Thus, the recess advantageously allows the pile positioning tool to be structurally connected to the hull substantially directly at least at two, e.g. three, spaced apart circumferential positions of the pile positioning tool. By contrast, in known methods wherein a pile positioning tool may be cantilevered over a side of the hull, only one such a direct structural connection may be possible.

[0051] When the pile positioning tool is arranged at least partly within the recess, the pile positioning tool may thereby advantageously be arranged with respect to structural connection to the hull, in particular when the recess is arranged centrally between a port side and a starboard side of the hull, and / or on a longitudinal center line of the hull.

[0052] Optionally, the recess and / or the pile positioning tool is arranged centrally between a port side and a starboard side of the hull, and / or on a longitudinal center line of the hull.

[0053] Thereby, force transmission between the monopile and the hull may be relatively well balanced with respect to structural features of the hull and / or positions of the legs with respect to the hull. In addition, such a central arrangement of the recess and / or the pile positioning tool can facilitate a favorable center of gravity of transit and jacking loading conditions of the jack-up, e.g. allowing favorable distribution of cargo loads over the jack-up legs, thereby favorably affecting the possible cargo and installation capacity of the jack-up.

[0054] Optionally, the monopile has a diameter of at least 8 meter, preferably at least 10 meter, more preferably at least 12 meter, even more preferably at least 14 meter, for example about 15 or 16 meter.

[0055] Relatively large and / or heavy monopiles may thus be installed, allowing to support relatively large wind turbines and / or to support wind turbines on the sea floor at relatively large depths. It shall be appreciated that elements such as the recess, hinging mechanism and pile positioning tool described herein are dimensioned to accommodate the size of the monopile. A same jack-up vessel, e.g. with a same recess, hinging mechanism and pile positioning tool, may nevertheless be able to accommodate different sizes of monopiles. Elements such as the hinging mechanism and the pile positioning tool may be adjustable to accommodate different monopile sizes. Meanwhile, the recess is preferably dimensioned in accordance with a largest size monopile to be installed and / or in accordance with a largest size of the pile positioning tool which may be arranged within the recess as explained elsewhere herein. Nevertheless, it shall be appreciated that the installation method of the present disclosure is not necessarily limited to any size of monopile, and that smaller monopiles may be installed e.g. using a jack-up vessel that is also usable for installation of larger monopiles.

[0056] A further aspect, which may be combined with one or more other aspects and / or options described herein, provides a jack-up vessel for installing a monopile as foundation for a wind turbine at an offshore location, comprising legs and a hull that is in a jacked-up state with respect to the legs to be above the waterline, wherein, in plan view, the legs together define a legs section of the hull where the hull structurally interconnects the legs, and wherein, in plan view, a perimeter of the hull is shaped with a recess extending towards the legs section, the recess being dimensioned for the monopile to be lowered therethrough in an upright orientation.

[0057] Such a jack-up vessel can provide advantages corresponding to those explained above for the installation method.

[0058] Optionally, a pile positioning tool for the monopile is arranged at least partly within the recess, in particular being connected to the hull at least at two mutually opposite sides of the recess.

[0059] Advantages of such an arrangement have been explained above in the context of the method.

[0060] Optionally, a hinging mechanism is arranged at a port side or starboard side of the hull, the hinging mechanism defining a hinging axis and being arranged for interconnecting the monopile to the hull during an adjustment of the monopile about the hinging axis from a lying orientation to the upright orientation, wherein the hinging axis preferably extends substantially parallel to a longitudinal axis of the hull.

[0061] Advantages of such an arrangement have been explained above in the context of the method.

[0062] Preferably, the jack-up vessel is evidently configured for use as the jack-up vessel in a method as described herein. For example, the jack-up vessel preferably comprises the described crane with the base situated at and around one of the legs. Other examples shall be apparent to the skilled person having the benefit of the present disclosure, in particular from the descriptions regarding options for the method herein.

[0063] The jack-up vessel may be used for installing the monopile as foundation at the offshore location, and / or for removing the monopile from the offshore location. In case of removal, the monopile may be lifted out from the seafloor through the recess and / or may be adjusted from an upright orientation to a lying orientation using the hinging mechanism. The preferred crane may be used during the lifting and / or the adjustment.

[0064] Thus, a same jack-up vessel may advantageously be used for removing a monopile.

[0065] Although the optional arrangement of the hinging mechanism and / or the hinging axis at the port side or starboard side of the hull has been described herein in combination with the described recess, it shall be appreciated that such an arrangement may alternatively be provided and / or used without provision and / or use of such a recess, in particular with the described advantage of facilitating adjustment of a monopile transversely arranged on a deck of the jack-up vessel to an upright orientation.

[0066] DETAILED DESCRIPTION

[0067] In the following, the invention will be explained further using examples of embodiments and drawings. The drawings are schematic and merely show an example. In the drawings, corresponding elements are provided with corresponding reference signs. For clarity of the drawings, some elements and / or references signs may be omitted from some of the figures, wherein the presence of such elements may nevertheless be understood in view of one of more other figures and / or the description. In the drawings:

[0068] Fig. 1 shows a plan view of a jack-up vessel with three monopiles in a lying orientation on a main deck of the jack-up vessel and with a leg based crane of the jack-up vessel in a configuration for sailing;

[0069] Fig. 2 A shows a plan view of the jack-up vessel with the crane in a configuration for initial lifting of one of the monopiles, wherein said one monopile is interconnected to the jack-up vessel via a hinging mechanism;

[0070] Fig. 2B shows a rear view of a central section of the jack-up vessel with the hinging mechanism and the monopile as in Fig. 2A; Fig. 3 A shows a plan view of the jack-up vessel, wherein for clarity the crane is not shown, wherein compared to Figs. 2A-B the monopile has been adjusted to an upright orientation using the crane and the hinging mechanism;

[0071] Fig. 3B shows a rear view of the central section of the jack-up vessel with the hinging mechanism and the monopile in the upright orientation as in Fig. 3 A;

[0072] Fig. 3C shows a rear view of the central section of the jack-up vessel, wherein compared to Fig. 3B the monopile has been lifted clear of the hinging mechanism;

[0073] Fig. 4A shows a plan view of the jack-up vessel, wherein for clarity the crane is not shown, wherein the monopile is shown in different subsequent positions as the monopile is moved in its upright orientation from the hinging mechanism to above a stern-side recess in the hull using the crane;

[0074] Fig. 4B shows a rear view of an aft section of the jack-up vessel, wherein the monopile is above the recess;

[0075] Fig. 5 shows a side view of an aft section of the jack-up vessel with the monopile suspended from the crane in a position VI as indicated in Fig. 4 A; and

[0076] Fig. 6 shows a rear view of an aft section of the jack-up vessel, wherein the monopile extends through the recess while being fixated in the seafloor below the recess.

[0077] The figures show a jack-up vessel 1 for installing a monopile 2, 2a and / or 2b as foundation for a wind turbine at an offshore location. In the shown example, the monopile 2 is being installed while further monopiles 2a and 2b remain on a main deck 13 of the jack-up vessel 1, e.g. for later installation at one or more subsequent offshore locations. In the shown example, the monopiles 2, 2a, 2b have a diameter of about 15 or 16 meter. Nevertheless, it shall be appreciated that differently sized monopiles may be used.

[0078] The jack-up vessel 1 comprises legs 3a-3d, and a hull 4 that can be jacked with respect to the legs 3a-3d to be above the waterline 16. In plan view, the legs 3a-3d together define a legs section 5 of the hull 4 where the hull 4 structurally interconnects the legs 3a-3d. The legs section 5 is schematically indicated in Fig. 4A by a dotted line indicating a perimeter of the legs section 5 in plan view.

[0079] In plan view, a perimeter 6 of the hull 4 is shaped with a recess 7 extending towards the legs section 5, in particular without extending into the legs section. The recess 7 is dimensioned for the monopile 2 to be lowered therethrough in an upright orientation. In the shown example, the recess 7 is arranged aft of the legs 3a-3d and centrally between a port side PS and a starboard side SB of the hull 4, in particular on a longitudinal center line L4 of the hull 4.

[0080] In the shown example, the jack-up vessel 1 comprises a crane 12 with a based situated at and around one of the legs, here leg 3a, in particular to be primarily supported by the one leg 3a during use. In plan view, the recess 7 is arranged at a side of the legs section 5 that is at least co-defined by the one leg 3a where the base of the crane 12 is situated, in particular a side corresponding to a stern ST of the hull 4.

[0081] In the shown example, a pile positioning tool 8 for the monopile 2 is arranged within the recess 7, the pile positioning tool 8 being connected to the hull 4 at two mutually opposite sides 9 of the recess 7. Although not shown, the pile positioning tool 8 is preferably additionally connected to the hull 4 at a third side of the recess 7 that is between the two opposite sides 9. The pile positioning tool 8 is adjustable with respect to the hull 4 for adjustment of a position and / or orientation of the monopile 2 with respect to the hull 4 at the recess 7, in particular other than a vertical position adjustment of the monopile 2. Nevertheless, the pile positioning tool 8 may itself be vertically adjustable with respect to the hull 4 to facilitate the adjustment of the position and / or orientation of the monopile 2. The pile positioning tool 8 is adjustable to accommodate different shapes and / or sizes of monopiles. The pile positioning tool 8 is adjustable to release the pile positioning tool 8 from the monopile 2 to allow the jack-up vessel 1 to move away from the monopile 2 after the fixating of the monopile 2 to the seafloor 11.

[0082] In the shown example, a hinging mechanism 10 is arranged at a starboard side SB of the hull 4, the hinging mechanism 10 defining a hinging axis H and being arranged for interconnecting the monopile 2 to the hull 4 during an adjustment of the monopile 2 about the hinging axis H from a lying orientation to an upright orientation. Such an adjustment of the monopile 2 may also be referred to as upending of the monopile. The hinging axis H here extends parallel to a longitudinal axis L4 of the hull 4.

[0083] The jack-up vessel 1 is configured for use as the jack-up vessel 1 in a method of installing the monopile 2 as foundation at the offshore location. The method comprises: providing the jack-up vessel 1 at the offshore location, wherein the legs 3a-3d are supported on a seafloor 11 and the hull 4 is in a jacked-up state with respect to the legs 3a-3d. In particular, the hull 4 may thus be clear of the waterline 16. The method further comprises: providing the monopile 2 at the offshore location; lowering the monopile 2 in an upright orientation through the recess 7 to a seafloor 11 below the recess 7; and fixating the monopile 2 in the seafloor 11 to form the foundation.

[0084] Throughout the figures, to facilitate understanding of the example shown as illustration of the method, subsequent positions of the monopile 2a being installed are indicated by Roman numerals I to VIII. The indicated positions I to VIII may be referred to throughout the present description, merely to facilitate understanding using the example to serve as illustration. In the shown example, with particular reference to Figs. 2A-B and 3A-B, prior to the lowering of the monopile 2, the monopile 2 is adjusted from a lying orientation (I) to the upright orientation (II) using the crane 12. Prior to the adjustment, the monopile 2 in the lying orientation (I) is arranged on a main deck 13 of the jack-up vessel 1, in particular to extend mainly transverse with respect to a longitudinal axis L4 of the hull 4. During the adjustment, the monopile 2 is interconnected to the jack-up vessel 1 by the hinging mechanism 10, wherein the hinging mechanism 10 determines the hinging axis H for the adjustment.

[0085] In the shown example, with particular reference to Figs. 3A to 5, prior to the lowering of the monopile 2, and after the adjustment to the upright orientation, the monopile 2 is moved while being in the upright orientation, in particular to above the recess 7 (VII) from an area at a distance from the recess 7 where the monopile 2 was adjusted to the upright orientation (II, III) from a lying orientation.

[0086] In the shown example, the moving of the monopile 2 in the upright orientation (II to VII) is performed using the crane 12, wherein the moving comprises slewing of the crane 12 while the monopile 2 is suspended from the crane 12 and follows a trajectory from location II to location VII and VIII. As can be seen in Fig. 4A, the monopile 2 may thus be moved around the leg 3a where the base of the crane 12 is situated, first mainly rearward along the outboard side of the perimeter 6 of the hull 4, and then crossing over an aft section of the hull 4 to above the recess 7 that is here arranged centrally between the port side PS and starboard side SB on a longitudinal center line L4 of the hull 4. During the movement, the monopile 2 can remain relatively close to the leg 3a, in particular in a favorable load range for the crane 12 as well as being favorable with respect to jack-up loads on the leg 3a. The trajectory of moving the monopile 2 from the lying orientation, location I, towards and into the recess, location VIII, is done by the crane 12. Adjusting the monopile from the lying location I to the upright location II can be done at a side of the hull 4 where the leg 3a around which the crane 12 is positioned, which side is transverse to the side of the hull 4 having the recess 7. Such side can typically be a port side or a starboard side, whereas the recess 7 may typically be at the stern side or a bow side. Then, with the monopile 2 in upright position, the hinging mechanism 10 may disengage from the monopile 2 and the monopile 2 may now be fully suspended by the crane 12. A first part of the trajectory of moving the monopile from the upright position to the position at or in the recess may commence. The crane 12 may slew to move the monopile slightly outwardly out of the hinging mechanism away from the hull 4. This is illustrated as location III in Fig. 4A. During the first part of the trajectory, the crane 12 may continue the slewing movement while bringing the monopile along location IV and to location V. During this first part of the trajectory, the monopile 12 moves outside of the perimeter of the hull 4 and alongside the hull 4 towards location V which may be closer to the base of the crane 12 than locations IV and III, thereby contributing to a more favorable load distribution. During the first part of the trajectory, the distance between the monopile 2 and the base of the crane 12 may vary, as can be seen in Fig. 4A. By varying the distance during slewing, the monopile 2 may move approximately alongside the hull towards the side of the hull containing the recess, thereby approaching the leg 3a around which the base of the crane 12 is arranged. In Fig. 4A this is illustrated by location V. Location V typically may be an unfavorable slewing position for the crane 12, so to approach the base of the crane 12 with the monopile 2 as closely as possible at location V is advantageous for the load distribution on the legs. If the monopile is not already above the waterline, the monopile 2 may then be lifted above the waterline, preferably until a height above deck level. The second part of the trajectory may commence during which the monopile 2 may at least partially be within the perimeter 6 of the hull 4. The crane 12 may slew further from the location V near the base of the crane 2 towards a location VII above the recess 7. During part of the slewing movement from location V to location VII, the monopile 2 is lifted above the deck of the hull and inside the perimeter of the hull 4, illustrated by location VI in Fig. 4A. At location VII, the monopile 2 may be lowered towards the recess 7 to extend through the recess 7 towards the seafloor, illustrated as location VIII in Fig. 4A and Fig. 6. Also during the second part of the trajectory, the distance between the monopile 2 and the base of the crane 12 may vary, thereby contributing to a more favorable load distribution. From location V onward in the second part of the trajectory, the distance between the monopile and the base of the crane 12 also varies, and may even slightly increase, as the monopile 2 moves at least partially within the perimeter 6 of the hull 4, toward the recess 7. The recess 7 is here arranged at the stern side, close to an area between two of the legs, so when moving the monopile 2 during the second part of the trajectory towards the recess 7, the distribution of load between those legs can be improved. The distance between the monopile 2 and the base of the crane 12 in plan view may be varied, in particular between a smaller distance during at least a part of the first part of the trajectory when the monopile 2 is suspended outside and adjacent the perimeter 6 of the hull 4 and a larger distance during at least a part of the second part of the trajectory when the monopile 2 is suspended at least partly within the perimeter 6 of the hull 4. Varying the distance may be beneficial for leg loads and / or load distribution of the jack-up vessel and / or may allow handling of relatively large and heavy monopiles within an operational crane envelope.

[0087] In the shown example, the lowering of the monopile 2 comprises use of the crane 12. In particular, the crane 12 may lower the monopile 2 from above the recess 7 (VII) to extend through the recess (VIII, Fig. 6). In plan view, during the lowering of the monopile 2, the monopile 2 is arranged within the recess 7, in particular within the pile positioning tool 8 that is here arranged within the recess 7. The lowering and / or the fixating of the monopile 2 may comprise hammering the monopile into the seafloor 11. Thereto, a hammer tool 14 may be provided that may be stored on the deck 13 when not in use, in particular close to the monopile installation location to facilitate handling of the hammer tool and associated hydraulic equipment. In Fig. 6, it can be seen that a lower end of the monopile 2 has been embedded in the seafloor 11 as a result of the hammering process.

[0088] Lateral force may be transmitted between the monopile 2 and the hull 4 via the pile positioning tool 8 into the legs 3a-3d, in particular during the lowering and / or fixating. The pile positioning tool 8 may be adjusted with respect to the hull 4 for adjustment of a position and / or orientation of the monopile 2 with respect to the hull 4, in particular other than a vertical position adjustment. The adjustment may comprise at least one of: adjustment of a position of the monopile 2 with respect to a forward-aft and / or port-starboard direction of the hull; adjustment of a verticality of the monopile 2; rotation of the monopile 2 about its main axis L2.

[0089] Although the invention has been explained further herein using examples of embodiments and drawings, these do not limit the scope of the invention as defined by the claims. Within said scope, many variations, combinations and extensions are possible, as shall be appreciated by the skilled person having the benefit of the present disclosure. For example, a jack-up vessel may have more or less than four legs. In some variants, the recess may be arranged at the bow, in particular in case the preferred crane is arranged closer to the bow than to the stern. All such variants are included in the scope of the invention as defined by the claims. LIST OF REFERENCE SIGNS

[0090] 1. Jack-up vessel

[0091] 2. Monopile

[0092] 2a, 2b. Further monopiles

[0093] 3a-3d. Legs

[0094] 4. Hull

[0095] 5. Legs section

[0096] 6. Perimeter

[0097] 7. Recess

[0098] 8. Pile positioning tool

[0099] 9. Side of recess

[0100] 10. Hinging mechanism

[0101] 11. Seafloor

[0102] 12. Crane

[0103] 13. Deck

[0104] 14. Hammer tool

[0105] 15. Crane boom

[0106] 16. Waterline

[0107] BW. Bow

[0108] H. Hinging axis

[0109] L2. Main axis of monopile

[0110] L4. Longitudinal axis of hull

[0111] PS. Port side

[0112] SB. Starboard side

[0113] ST. Stern

[0114] I-VIIL Subsequent positions of monopile during installation

Claims

Claims1. Method of installing a monopile as foundation for a wind turbine at an offshore location, comprising: providing, at the offshore location, a jack-up vessel with legs supported on a seafloor and a hull that is in a jacked-up state with respect to the legs to be above the waterline, wherein, in plan view, the legs together define a legs section of the hull where the hull structurally interconnects the legs, and wherein, in plan view, a perimeter of the hull is shaped with a recess extending towards the legs section; providing, at the offshore location, a monopile for use as a foundation for a wind turbine; lowering the monopile in an upright orientation through the recess to a seafloor below the recess; and fixating the monopile in the seafloor to form the foundation.

2. Method according to claim 1, wherein the lowering of the monopile comprises use of a crane of the jack-up vessel, which crane has a base that is situated at and around one of the legs, in particular to be primarily supported by the one leg during use.

3. Method according to claim 2, wherein, in plan view, the recess is arranged at a side of the legs section that is at least co-defined by the one leg where the base of the crane is situated, in particular a side corresponding to a stern of the hull.

4. Method according to any of the preceding claims, wherein prior to the lowering of the monopile, the monopile is adjusted from a lying orientation to the upright orientation.

5. Method according to claim 4 as dependent from claim 2 or 3, wherein the adjustment is performed using the crane.

6. Method according to claim 4 or 5, wherein during the adjustment, the monopile is interconnected to the jack-up vessel by a hinging mechanism that determines a hinging axis for the adjustment.

7. Method according to claim 6, wherein the hinging mechanism and / or the hinging axis is arranged at a side of the legs section that is at least co-defined by the one leg where the base of the crane is situated, wherein the side preferably corresponds to a port side or starboard side of the hull.

8. Method, preferably according to claim 7, of installing a monopile as foundation for a wind turbine at an offshore location, comprising: providing at the offshore location a monopile for use as a foundation for a wind turbine and a jack-up vessel having legs and a hull that is in a jacked- up state with respect to the legs to be above the waterline; lowering the monopile in the upright orientation to a seafloor, wherein during the lowering the jack-up vessel is in a jacked-up state with the legs of the jackup vessel supported on the seafloor; and fixating the monopile in the seafloor to form the foundation, wherein the hinging mechanism and / or the hinging axis is arranged at a port side or starboard side of the hull.

9. Method according to any of claims 4 - 8, wherein prior to the adjustment, the monopile in the lying orientation is arranged on a deck of the jack-up vessel, in particular to extend mainly transverse with respect to a longitudinal axis of the hull, wherein the deck is preferably a main deck of the jack-up vessel.

10. Method according to any of the preceding claims, wherein, prior to the lowering of the monopile, the monopile is moved while being in the upright orientation, in particular to above the recess from an area at a distance from the recess, such as an area where the monopile was adjusted to the upright orientation from a lying orientation.

11. Method according to claim 10 as dependent from claim 2, wherein the moving of the monopile in the upright orientation is performed using the crane, wherein the moving comprises slewing of the crane while the monopile is suspended from the crane.

12. Method according to claim 11, wherein, during at least some of the slewing, the monopile is suspended outside a perimeter of the hull.

13. Method according to claim 11 or 12, wherein, during at least some of the slewing, the monopile is suspended within a perimeter of the hull.

14. Method according to any of the claims 11 - 13, wherein, during the slewing, a distance between the monopile and the base of the crane in plan view is varied, in particular between a smaller distance when the monopile is suspended outside and adjacent the perimeter of the hull and a larger distance when the monopile is suspended at least partly within the perimeter of the hull.

15. Method according to any of the claims 11 - 14, wherein, during a first part of the slewing, the monopile is suspended outside the perimeter of the hull, and during a second part of the slewing, the monopile is suspended within the perimeter of the hull.

16. Method according to any of the claims 13 - 15, wherein, when the monopile is suspended within the perimeter of the hull, the monopile is above the hull to cross over a section of the hull from a starboard side or port side of the hull to above the recess.

17. Method according to any of the claims 12 - 16, wherein, when the monopile is suspended outside the perimeter of the hull, the monopile is above the waterline.

18. Method according to any of the preceding claims, wherein the lowering and / or the fixating comprises hammering the monopile into the seafloor.

19. Method according to any of the preceding claims, wherein the recess is arranged centrally between a port side and a starboard side of the hull and / or on a longitudinal center line of the hull.

20. Method according to any of the preceding claims, wherein the recess is arranged aft of the legs.

21. Method according to any of the preceding claims, wherein in plan view, during the lowering of the monopile, the monopile is arranged within the recess.

22. Method according to any of the preceding claims, wherein, at least during the lowering and / or fixating of the monopile, a pile positioning tool for the monopile is provided at the recess, the pile positioning tool being arranged to transmit lateral force between the monopile and the hull for subsequent transmission of force into the legs, wherein the method preferably comprises lateral force transmission between the monopile andthe hull via the pile positioning tool, in particular during the lowering and / or fixating.

23. Method according to claim 22, wherein the pile positioning tool is adjustable with respect to the hull for adjustment of a position and / or orientation of the monopile with respect to the hull at the recess, in particular other than a vertical position adjustment, wherein the method preferably comprises, for example before and / or during the lowering and / or fixating of the monopile, adjustment of the pile positioning tool with respect to the hull for adjustment of a position and / or orientation of the monopile with respect to the hull, in particular other than a vertical position adjustment.

24. Method according to claim 23, wherein the adjustment of the position and / or orientation of the monopile with respect to the hull comprises at least one of: adjustment of a position of the monopile with respect to a forward-aft and / or port-starboard direction of the hull; adjustment of a verticality of the monopile; rotation of the monopile about its main axis.

25. Method according to any of claims 22 - 24, wherein the pile positioning tool is adjustable to accommodate different shapes and / or sizes of monopiles.

26. Method according to any of claims 22 - 25, wherein the pile positioning tool is adjustable to release the pile positioning tool from the monopile to allow the jack-up vessel to move away from the monopile after the fixating of the monopile to the seafloor.

27. Method according to any of claims 22 - 26, wherein the pile positioning tool is arranged at least partly within the recess, in particular being connected to the hull at least at two mutually opposite sides of the recess.

28. Method according to any of the preceding claims, wherein the monopile has a diameter of at least 8 meter, preferably at least 10 meter, more preferably at least 12 meter, even more preferably at least 14 meter, for example about 15 or 16 meter.

29. Jack-up vessel for installing a monopile as foundation for a wind turbine at an offshore location, comprising legs and a hull that can be jacked with respect to the legs to be above the waterline, wherein, in plan view, the legs together define a legs section of the hull where the hull structurally interconnects the legs, and wherein, in plan view, a perimeter of the hull is shaped with a recess extending towards the legs section, the recess being dimensioned for the monopile to be lowered therethrough in an upright orientation.

30. Jack-up vessel according to claim 29, wherein a pile positioning tool for the monopile is arranged at least partly within the recess, in particular being connected to the hull at least at two mutually opposite sides of the recess.

31. Jack-up vessel, preferably according to claim 29 or 30, for installing a monopile as foundation for a wind turbine at an offshore location, comprising legs and a hull that can be jacked with respect to the legs to be above the waterline, wherein a hinging mechanism is arranged at a port side or starboard side of the hull, the hinging mechanism defining a hinging axis and being arranged for interconnecting the monopile to the hullduring an adjustment of the monopile about the hinging axis from a lying orientation to an upright orientation, wherein the hinging axis preferably extends substantially parallel to a longitudinal axis of the hull.

32. Jack-up vessel according to any of claims 29 - 31 evidently configured for use as the jack-up vessel in a method according to any of claims 1 - 28.

33. Use of a jack-up vessel according to any of claims 29 - 32 for installing and / or removing of a monopile as foundation for a wind turbine at an offshore location.

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