Method and vessel for installing monopiles

Abstract

An installation vessel for installing monopiles supporting offshore wind turbines, the vessel having a pile holding device comprising a pile holder and a support assembly configured to move the pile holder relative to the vessel in a horizontal plane, a monitoring system configured to monitor the monopile suspended relative to the pile holder in a horizontal plane during a gripping phase in which the monopile is suspended from a crane and gripped by the pile holder, the system sending signals to a motion control unit of the support assembly representative of the position and movement of the monopile relative to the pile holder.

Description

[Technical field]

[0001] The present invention relates to the field of installation of monopiles arranged to support offshore wind turbines. The present invention relates to a method for installing monopiles and an installation vessel for installing monopiles. [Background technology]

[0002] In the field of offshore wind turbines, monopiles with lengths of over 100 m, diameters of over 10 m and masses of over 1000 or even 2000 tonnes are not uncommon. These monopiles have to be transported to their offshore installation sites, where they are installed.

[0003] In the prior art, for example in US Pat. No. 5,399,633, it is known to transport a monopile in a horizontal orientation on board a ship to an offshore installation site. At the installation site, the monopile is held in a horizontal orientation by a pile holder provided on board the ship. The monopile is then erected to a vertical orientation and then lowered into the water. The monopile is erected by a crane provided on board the ship, with the lower end of the pile supported by the pile holder.

[0004] In the document WO 2005 / 023301 the vessel is equipped with a dedicated erecting device and a separate dedicated pile holder device. Erecting the monopile is performed by placing a lower end portion of the monopile on the erecting device and lifting the upper end of the monopile by a crane. While the monopile is held by the erecting device, the lowermost end of the monopile is moved into the open pile holder. The pile holder is then closed around the monopile and the erecting device is removed from the monopile.

[0005] In alternative methods, such as in US Pat. No. 5,399,633 or US Pat. No. 5,499,647, the monopile is first erected into a vertical orientation by a crane and then gripped by a pile holder. For example, erecting the monopile is performed using only a crane or using two cranes working together in the erecting process. For example, a dedicated erecting tool is utilized that is different from any pile holding device of the ship. For example, as discussed in US Pat. No. 5,499,633, a single crane is used in combination with a dedicated erecting tool that engages the lower end portion of the monopile for the erecting process. In these methods, the monopile is gripped by the pile holder while already in a vertical orientation and suspended from the crane. A drawback of these methods is that the pile holder may be damaged by the monopile before it is gripped by the pile holder or when the pile holder is in the process of holding the monopile. The pile holder may become more susceptible to damage as the size and weight of the monopile increases.

[0006] One known approach to mitigate this drawback is to equip the pile holder with a monopile fender or the like, for example to protect the pile holder's rather fragile pile engagement device (which typically has one or more hydraulic actuators for precise movement / positioning of said pile engagement device) from any excessive impact. A further known approach is to first form an oversized opening for the monopile during the gripping phase by first placing the pile holder's array of pile engagement devices in a retracted position. Another known approach is to use a tugger winch to stabilize the suspended monopile. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 117846 Brochure [Patent Document 2] US Patent Application Publication No. 2021 / 123203 [Patent Document 3] International Publication No. 2018 / 052291 Brochure [Patent Document 4] International Publication No. 2019 / 172752 Brochure [Patent Document 5] International Publication No. 2020 / 128016 Brochure Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to improve existing methods and vessels utilized for installing monopiles, for example when considered in terms of the engagement process between the pile holder and the monopile suspended from the ship's crane, for example to reduce the risk of damage to the pile holder by the monopile. [Means for solving the problem]

[0009] The present invention relates to a method for installing monopiles configured to support an offshore wind turbine as claimed in claim 1.

[0010] When the monopile is vertically oriented and suspended by the crane, the monopile and the crane form a giant pendulum, with the monopile forming the pendulum weight. In this configuration, movement of the monopile relative to the ship can be caused by a variety of factors, such as sea state induced ship movements (e.g. roll and / or pitch), operation of the ship's dynamic positioning system (if a dynamic positioning system is present), changes in the load on the ship's hull (e.g. due to a shift in the centre of mass of the monopile), operation of the ship's ballast system, wind forces acting on the large monopile and / or the crane, slewing movement of the crane during erection, luffing movement of the crane boom during erection, vibrations in the crane structure, e.g. at the crane boom, movement of the monopile induced as a result of the crane operating. Furthermore, movement of the monopile relative to the ship can also be caused intentionally, e.g. by controlled movement of the crane, e.g. when the monopile is moved, e.g. diverted, from a first position, e.g. a transport site, to a second position, e.g. an installation site.

[0011] The invention is based on the insight that damage to the pile holder may occur due to movements, such as pendulum or swivel movements, of the monopile relative to the pile holder when the monopile is suspended by a crane, especially if the pile holder is brought closer to the monopile in the process of gripping the monopile by the pile holder. Even relatively small movements between the monopile and the pile holder may result in damage to one or more components of the pile holder due to the high weight of the monopile. Damage to the pile holder may be caused, for example, if the monopile is not yet in the pile holder when the pile holder and the monopile are brought together and hits the pile holder, for example against one or more pile engagement devices of the pile holder. Damage may also be caused by a collision between the pile holder and the monopile when the monopile is in the pile holder but is not yet fixedly gripped, for example.

[0012] The present invention, by implementing it, reduces the relative movement between the monopile and the pile holder. By reducing the relative movement between the monopile and the pile holder, damage caused by possible collisions between them can be reduced or avoided. Furthermore, the present invention reduces or avoids the risk of collision between the monopile and the pile holder, for example by the pile holder being able to start moving away from the monopile if the monopile starts moving towards the pile holder in an undesirable manner.

[0013] The vessel used in the method comprises a hull and a crane mounted on the hull. The vessel may be a floating vessel or a lifting vessel and the method may be carried out when the vessel is floating or non-floating, for example with the hull supported by jack-up legs.

[0014] The vessel further comprises a pile holding device comprising a pile holder for gripping the monopile and a support assembly for supporting the pile holder, the support assembly being mounted relative to the hull of the vessel to support the pile holder relative to the hull.

[0015] The pile holder is movably supported by the support assembly such that the pile holder can move in a horizontal plane relative to the hull, allowing the pile holder to move in a horizontal plane independent of the hull and a crane mounted thereon. For example, during driving of the monopile into the seabed, the support assembly can be operated to ensure verticality of the monopile, e.g. to compensate for vessel movements that disrupt verticality.

[0016] The support assemblies comprise motion actuators, e.g. hydraulic or mechanical motion actuators, which are configured to move the pile holders relative to the hull. By controlling the motion actuators the pile holders can thus be moved in a horizontal plane relative to the hull. As described herein, this control also allows synchronizing the movement of the pile holders in the gripping phase of the monopile suspended from the crane. The motion actuators are controlled by a motion control unit, e.g. comprising a processor, which sends control signals to the motion actuators.

[0017] The installation vessel further comprises a monitoring system configured to monitor the position and movement of the suspended monopile relative to the pile holder in a horizontal plane during the gripping phase, when the monopile is suspended from the crane and gripped by the pile holder. For example, the monitoring system comprises a number of sensors for determining the position and movement. The sensor or sensors may only detect position / distance, and the movement is determined based on a number of position / distance determinations over time by the sensor or sensors. The sensor or sensors are preferably provided on the pile holder. In another embodiment, the monitoring system may comprise one or more sensors provided on the support assembly or hull, and the position and movement relative to the pile holder is determined by taking into account the known movement of the vessel relative to the hull. In yet another embodiment, one or more sensors, e.g. inertial based sensors, are provided on the monopile and / or one or more sensors are provided on a lifting tool suspended from the crane and fixedly holding the top end of the monopile. For example, to determine monopile movement, the monitoring system determines the position of the monopile at multiple points in time, e.g., at fixed time intervals, and correlates the changes in monopile position to the monopile movement. For example, the monitoring system is configured to determine the monopile position and movement at a frequency of greater than 20 Hz, preferably greater than 40 Hz, such as 50 Hz.

[0018] The monitoring system is configured to send signals indicative of the monitored position and movement of the monopile relative to the pile holder to the motion control unit, thereby enabling the motion control unit to control the motion actuator based on the monitored position and movement of the monopile, and therefore the movement of the pile holder.

[0019] The method according to the invention utilizing an installation vessel includes the step of operating, by the motion control unit, the motion actuator to synchronize the movement of the pile holder with the movement of the monopile relative to the vessel hull based on the transmitted signal. By synchronizing the movement of the pile holder with the movement of the monopile, the relative movement between the pile holder and the monopile is controlled and possibly minimized or even eliminated before the monopile is actually gripped by the pile holder. For example, if the movement of the pile holder is perfectly synchronized with the movement of the monopile, there may be no relative movement between the pile holder and the monopile during the actual gripping phase. For example, this synchronization may not be perfect and there may still be a small relative movement between the monopile and the pile holder. The relative movement between the pile holder and the monopile is smaller than the relative movement between the pile holder and the vessel hull when these movements are synchronized. For example, the movement of the pile holder may be synchronized with the movement of the monopile only in a single direction, e.g. the x-direction, and not in other directions, e.g. the y-direction.

[0020] The motion actuator is operated by the motion control unit to align the centre of the pile holder with the central axis of the monopile. For example, the movement of the pile holder in one direction towards the monopile cannot be synchronized with the monopile movement, but a small relative movement of the pile holder towards the monopile can be caused to enable alignment, while at the same time the movement of the pile holder in the vertical direction is synchronized with the monopile movement. This allows for a controlled alignment of the centre of the pile holder with the central axis of the monopile, thereby enabling gripping of the monopile with reduced collision risk.

[0021] In this approach of the invention, the pile holder actively positions itself with respect to the suspended monopile, thereby avoiding or at least mitigating excessive contact force changes during engagement. For example, application of the invention allows for a relatively smaller (e.g., in terms of diameter) and / or lighter design of the pile holding device than in prior art approaches. For example, being able to reduce the size and / or weight of the pile holder may also result in lower power being required to operate the pile holder during monopile landing and pile driving.

[0022] In practice, the suspended monopile does not necessarily have a (significant) pendulum movement before the gripping phase, e.g. if the vessel is not floating, e.g. because the vessel is a lifting vessel. However, even in the case of a lifting vessel, some pendulum movement of the suspended monopile may occur. For example, wind forces and / or crane movements (e.g. slewing) may induce some pendulum movement in the suspended monopile. The invention is advantageous even when no or only slight pendulum movement is observed in the suspended monopile. For example, (some) inaccuracies in the relative paths of the monopile and the pile holder leading up to and / or during the gripping phase can also be addressed by utilizing the invention.

[0023] In particular, when the vessel, embodied as, for example, a monohull vessel or a semi-submersible vessel, is floating, the sea state induced vessel movements may result in a pendulum motion of the suspended monopile before and possibly during the gripping phase. In these situations, the present invention may be used to counteract the pendulum motion of large monopiles by actively positioning the pile holder during the monopile gripping process.

[0024] Monitoring the movement of the monopile suspended from the crane during and preferably even before the gripping phase may be performed using a motion sensing system, e.g. contactless, e.g. based on one or more cameras and / or based on one or more inertial-based motion sensors. The sensor or sensors of this motion sensing system may be mounted on the motion compensated pile holding device, e.g. on the pile holder of the motion compensated pile holding device. Alternatively or additionally, the sensor or sensors of the motion sensing system may be mounted at other locations, e.g. on the hull of the ship, on the crane or (temporarily) on the monopile. The sensor or sensors may also be provided on the lifting tool, in which case the position of the pile is determined by determining the position of the lifting tool relative to the pile holder. These sensors may be provided on the pile holder, e.g. on a ring of the pile holder, or below the pile holder, e.g. on a part of the support assembly, e.g. a part that is directly connected to the pile holder ring and moves in unison with the pile holder ring. Furthermore, the sensors may, although not preferably, be mounted on the hull of the vessel, for example on deck.

[0025] During the gripping phase, when the centre of the pile holder is aligned with the central axis of the monopile, the lower end of the monopile may be located below the pile holder and the upper end of the monopile may be located above the pile holder.

[0026] In an embodiment, the step of synchronizing the movement of the pile holder with the movement of the monopile comprises: First, synchronizing the movement of the pile holder with the movement of the monopile in a first direction, i.e., in the x-direction; Then, synchronizing the movement of the pile holder with the movement of the monopile in a second direction, i.e., in the y direction, for example perpendicular to the x direction. For example, the x-direction is along the longitudinal direction of the vessel and the y-direction is perpendicular to this longitudinal direction. For example, this embodiment allows the synchronization of the movement of the pile holder to the monopile to be separated, for example performed in two steps or phases, with some overlap of the steps or phases. Furthermore, this allows maintaining synchronization in the x-direction with some deviation from the synchronization in the y-direction when aligning the pile holder to the monopile.

[0027] Once the pile holder is synchronized in movement with the suspended monopile and the centers of the monopile and pile holder are aligned, the pile engagement device can be engaged with the monopile, such as after closing the pile holder around the monopile.

[0028] In an embodiment, the monitoring system further comprises one or more sensors for providing actual data regarding one or more of the following: the vessel's motion, the vessel's position, the operation of the dynamic positioning system, the vessel's stability, the operation of the vessel's ballast system, and said method further comprises: Transmitting signals from the one or more additional sensors to the motion control unit. The data provided by these sensors may enable the motion control unit to control the movement of the pile holder relative to the monopile based on additional parameters. For example, if a sensor detects instability of the vessel, such as as a result of the vessel nearly capsizing, the motion control unit may control the pile holder to release the monopile and push it away from the vessel. In another example, the pile holder may additionally be operated based on information about the vessel movements, such as movements due to waves or due to the vessel's motion drive. In an example, the monitoring system and / or the motion control system may predict the movements of the monopile, the pile holder and / or the vessel based on the data of these sensors, such as, for example, if the sensor is a wave prediction sensor predicting a shallow wave window suitable for carrying out offshore operations.

[0029] In an embodiment, the method comprises: Step of lowering the monopile by crane The grasping phase further includes: Operating the crane to redirect the monopile towards the pile holder The monopile may be transported vertically and then suspended from the crane, or may be transported horizontally and erected, e.g. by a crane or a separate device, and then suspended by the crane. Once the monopile is suspended by the crane, preferably the movement of the pile holder is synchronized with the movement of the monopile, or during this phase, the crane may be operated to move the monopile towards the pile holder, e.g. to align the centre of the pile holder with the central axis of the monopile.

[0030] In an embodiment, the monitoring system comprises one or more distance sensors, for example provided on the pile holder, for measuring the position and preferably the movement of the monopile relative to the pile holder. This allows an efficient measurement of the position of the monopile relative to the pile holder. Furthermore, by performing multiple measurements of the monopile position during a time interval, it is possible to determine the movement of the monopile relative to the pile holder based on the measurements of the distance sensor. The one or more distance sensors may be embodied as line sensors measuring the distance to the monopile on a line, for example located in a horizontal plane along which the pile holder moves. For example, the one or more sensors are based on laser measurements, for example a laser projects a projection onto the monopile, a camera detects this projection on the monopile and a processor performs the appropriate calculations based on the detected projection. Providing a line sensor and / or taking laser-based measurements allows an accurate determination of the distance of the pile holder to the monopile.

[0031] In a further embodiment, the monitoring system comprises two or more distance sensors, each arranged, for example, on the pile holder. These distance sensors are arranged spatially spaced apart from one another, for example on the pile holder, and two or more of the distance sensors may have overlapping fields of view, for example the field of view of each of the distance sensors includes the center of the pile holder. For example, by providing two distance sensors spaced apart in a horizontal plane, for example around the center of the pile holder, the measurements of the monopile may be more accurate. For example, by providing two distance sensors spaced apart in a direction perpendicular to the horizontal plane, the measurements of the monopile may be less affected by secondary stealing effects, for example shadow effects. For example, four sensors may be provided, two sensors arranged at a first height on the pile holder and two sensors arranged at a second height different from the first height on the pile holder. Furthermore, the distance sensors located at each height may be arranged at different angles to one another, thereby having non-parallel fields of view. The provision of four sensors allows reliable triangulation of the monopile position even if one of the sensors provides inaccurate data, for example due to shadow effects, malfunction or obstructed view. By allowing the centre of the pile holder to be located within the field of view, the sensors are able to determine the distance to the pile holder when the central axis of the pile holder is aligned with the centre of the pile holder.

[0032] Preferably, the one or more distance sensors have a distance resolution of less than 1 cm, more preferably less than 5 mm, e.g. less than 3 mm. Preferably, the distance sensor is capable of performing distance measurements at distances of more than 50 meters, e.g. more than 80 meters, for dark surfaces, e.g. with 10% reflectance. Preferably, the distance sensor is capable of performing distance measurements at distances of more than 100 meters, e.g. more than 200 meters, for bright surfaces, e.g. with 80% reflectance.

[0033] In one embodiment, the support assembly comprises one or more horizontal hull mounting rails, e.g. X-rails extending horizontally and in the longitudinal direction of the ship's hull, mounted on the ship's hull, e.g. on the ship's deck. A subframe is movable on said one or more hull mounting rails. One or more subframe mounting rails, e.g. Y-rails extending horizontally and in the transverse direction of the ship's hull, are mounted on said subframe and perpendicular to the hull mounting rails. A support frame is movable on said subframe mounting rails and a pile holder is mounted on the support frame. A controllable motion actuator of the support assembly is configured to move said subframe on the hull mounting rails and to move the support frame on the subframe mounting rails. For example, this is a practical embodiment that may move the pile holder in a horizontal plane and allows for synchronization of movements in e.g. x and y directions.

[0034] Furthermore, the invention relates to an installation vessel for installing monopiles configured to support an offshore wind turbine as claimed in claim 8.

[0035] In this vessel embodiment, the motion control unit is configured to first operate the motion actuators to synchronize the movement of the pile holder with the movement of the monopile in a first direction, i.e., the x-direction, and thereafter to operate the motion actuators to synchronize the movement of the pile holder with the movement of the monopile in a second direction, i.e., the y-direction, which is perpendicular to the x-direction, e.g., the x-direction is along the length of the vessel and the y-direction is perpendicular to the vessel.

[0036] In this vessel embodiment, the monitoring system further comprises one or more sensors for providing actual data regarding one or more of the vessel motions, the vessel position, the operation of the dynamic positioning system, the vessel stability, the operation of the vessel ballast system, and the monitoring system is configured to transmit signals from the one or more additional sensors to the motion control unit.

[0037] In this vessel embodiment, the crane is configured to move, e.g. turn, the suspended monopile towards the pile holder for gripping the monopile by the pile holder.

[0038] In this vessel embodiment the monitoring system comprises one or more distance sensors, e.g. provided on the pile holder, for measuring the position and preferably the movement of the monopile relative to the pile holder.

[0039] In this vessel embodiment, the monitoring system comprises two or more distance sensors, e.g. each mounted on a pile holder, the distance sensors being spaced apart from one another, e.g. on the pile holder, and two or more of the distance sensors having overlapping fields of view, e.g. each field of view of the distance sensors including the centre of the pile holder.

[0040] In this vessel embodiment, the support assembly comprises one or more horizontal hull mounting rails, e.g. X-rails extending horizontally and in the longitudinal direction of the vessel's hull, mounted on the vessel's hull, e.g. on the vessel's deck. A subframe is moveable on said one or more hull mounting rails, and one or more subframe mounting rails, e.g. one or more Y-rails extending horizontally and in the transverse direction of the vessel's hull, are mounted on said subframe and perpendicular to said hull mounting rails. A support frame is moveable on said subframe mounting rails, pile holders are mounted on the support frame, and controllable motion actuators of the support assembly are configured to move said subframe on the hull mounting rails and to move the support frame on the subframe mounting rails.

[0041] As is known in the art, in embodiments, the pile holding device may not include tilt functionality, in some cases the pile holder may simply be tiltable relative to the support assembly in terms of achieving a transport mode or a docking mode.

[0042] In one embodiment, the vessel comprises one or more sensors configured to provide actual data regarding one or more of the vessel motions, vessel position, operation of the dynamic positioning system, vessel stability, operation of the ballast system, and the positioning of the pile holders during the engagement phase is further controlled / fine-tuned based on signals from these one or more sensors.

[0043] As known in the art, the pile holding device may comprise a ring or have only a single ring. The ring comprises a plurality of pile engagement devices distributed along the circumference of each ring, e.g. each pile engagement device comprises one or more pile guide rollers radially positionable relative to the ring. The ring comprises a ring base and one or more movable jaws, e.g. two semicircular jaws, each jaw being movable between a closed position and an open position. In the closed position, each ring may form a closed annulus. Preferably, the pile holder has a single ring.

[0044] The present invention also relates to a method for installing a monopile configured to support an offshore wind turbine, comprising the steps of: The hull and A crane mounted on the vessel; 1. A motion compensated pile retention device comprising: a motion compensating support assembly mounted relative to the vessel's hull; and Pile holder supported by a support assembly a motion compensated pile retention device comprising: An installation vessel equipped with The motion compensated support assembly comprises a controllable motion actuator and an associated motion control unit configured to compensate for vessel motions by controlling the position of the monopile during landing of the pile on the seabed and / or controlling the vertical orientation of the monopile during driving of the monopile into the seabed. The method may be adapted to: operating the crane to place the monopile in a suspended and erected orientation, e.g., using the crane alone or with a monopile erecting tool distinct from the motion compensated pile holding device; - bringing the suspended monopile, e.g. a lower end portion of the suspended monopile, into engagement with a pile holder; lowering the monopile by the crane while being guided by the pile holder so that the monopile lands on the seabed; driving the monopile deeper into the seabed, for example with the use of a pile drive; Including, During the phase of engaging the monopile suspended on the pile holder, the motion, e.g. pendulum motion, of the monopile is monitored by a monitoring system which transmits signals representative of the actual position and / or motion of the monopile, which signals are fed to a motion control unit of the motion compensated pile holding device which manages controllable motion actuators to actively position the pile holder with respect to the suspended monopile during the engagement phase.

[0045] In an embodiment, monitoring the movement of the monopile suspended from the crane during and preferably even before the engagement phase is performed using a motion sensing system, e.g. non-contact, e.g. based on one or more cameras and / or based on one or more inertial based motion sensors.

[0046] In an embodiment, the positioning of the pile holders during the engagement phase is controlled based on signals from one or more sensors providing actual data regarding one or more of the vessel motion, the vessel position, the operation of the dynamic positioning system, the vessel stability, the operation of the ballast system.

[0047] The invention also relates to an installation vessel configured to install monopiles configured to support an offshore wind turbine, the installation vessel comprising: The hull and A crane mounted on the vessel; 1. A motion compensated pile retention device comprising: a motion compensating support assembly mounted relative to the vessel's hull; and Pile holder supported by a support assembly a motion compensated pile retention device comprising: Equipped with a motion compensated support assembly comprising a controllable motion actuator and an associated motion control unit configured to compensate for vessel motions by providing positional control of the monopile during landing of the pile on the seabed and / or vertical control of the monopile during driving of the monopile into the seabed; The vessel may, in some cases, be in a floating hull situation. operating a crane to place the monopile in a suspended and erected orientation, e.g., using the crane alone or with a monopile erecting tool distinct from the motion compensated pile holding device; bringing the suspended monopile into engagement with a pile holder; lowering the monopile by the crane while being guided by the pile holder so that the monopile lands on the seabed; driving the monopile deeper into the seabed, for example with the use of a pile drive; configured to carry out a method comprising: The vessel comprises a monitoring system configured to monitor a movement, e.g. a pendulum movement, of the suspended monopile during a phase of bringing, e.g. a lower end part of the suspended monopile into engagement with the pile holder, the monitoring system transmitting signals representative of the actual position and / or movement of the monopile, the monitoring system being linked to a motion control unit such that said signals are supplied to the motion control unit, the motion control unit being configured to manage controllable motion actuators during said phase for actively positioning the pile holder relative to the suspended monopile holder.

[0048] The present invention will now be described with reference to the drawings. [Brief description of the drawings]

[0049] [Figure 1] FIG. [Diagram 2] FIG. 2 is a more detailed view of the pile holding device shown in FIG. 1. [Diagram 3] FIG. 2 shows the pile holding device in an open configuration. [Figure 4] FIG. 1 is a diagram showing a monohull installation ship for explaining the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Figure 1 shows a pile holding device on a vessel VE during handling of a monopile PI. In this embodiment, the vessel VE comprises a hull HU with at least one deck DE. The deck DE provides enough space to store the monopiles PI, in this case five, in a horizontal orientation. The monopiles PI are stored such that their longitudinal axes are parallel to the longitudinal axis of the vessel VE in this example. The longitudinal axis of the vessel extends between the bow and the rear (i.e. the stern) of the vessel. Lateral storage is also possible.

[0051] In this embodiment, the vessel VE is a mono-hull vessel, but could alternatively be a semi-submersible vessel.

[0052] In one embodiment, not shown, the vessel VE is an elevating vessel, in which legs can be lowered into the water so that the hull is at least partially above water, limiting or minimizing the impact of waves on the vessel, so that the vessel can be used in a floating state, for example when weather and wave conditions are good, and in a raised state when weather and wave conditions are bad.

[0053] In this embodiment, the pile holding device 1 is arranged on a longitudinal side of the ship, in this embodiment on the starboard side of the ship VE, so as to hold the pile PI outside the starboard profile of the ship VE as viewed from above. Alternatively, the pile holding device 1 is arranged on the stern of the ship so as to hold the monopile PI outside the stern profile of the ship as viewed from above.

[0054] In this embodiment, a crane CR is positioned adjacent to the holding device 1. The crane CR is configured to handle the monopile PI, which may include any of: lifting the monopile PI from a storage position, erecting the monopile PI, positioning the pile PI relative to the pile holding device 1, and lowering the monopile PI to the seabed. The monopile PI may be gripped by the pile holding device 1 when suspended by the crane CR.

[0055] In case the pile holding device 1 and the crane CR are arranged at the stern of the ship, the crane is preferably arranged in line with the centre of gravity of the ship VE and the pile holding device 1 is arranged adjacent to the crane. In such a case, the storage location of the pile drive mechanism is preferably on the side of the crane CR opposite to the side on which the pile holding device is arranged. The ship VE may also further comprise deck space for storing other equipment, such as for example a pile extension PX (also called a transition piece) arranged to be coupled to the free upper end of the pile PI and configured to support the mast of an offshore wind turbine.

[0056] Figure 2 shows the pile holding device 1 already gripping the monopile PI, e.g. after successfully completing the method steps of the invention, with the central axis of the monopile PI aligned with the centre of the pile holder PI. The pile holding device 1 shown in Figure 2 is mounted on a vessel VE, not shown.

[0057] As can be seen in Figure 2, the pile holding device 1 shown in the figure comprises a base structure BS, a pile holder PH having a first yaw Y1 and a second yaw Y2. The pile holding device further comprises a support assembly 2 mounted on the hull HU and supporting the pile holder PH at the base structure BS of the pile holder PH.

[0058] In the illustrated embodiment, the support assembly 2 comprises two horizontal hull mounting rails 7 mounted on the hull HU of the ship VE, for example on the deck DE of the ship VE. The hull mounting rails 7 are X-rails that extend horizontally along the hull HU of the ship VE. A subframe 8 is moveable on said hull mounting rails 7 and one subframe mounting rail 9 is mounted vertically on said subframe 8 and to the hull mounting rails 7. Furthermore, a support frame 10 is moveable on said subframe mounting rails 9. A pile holder PH is mounted on the support frame 10. The motion actuator 3 of the support assembly 2 is configured to move said subframe 8 on the hull mounting rails 7 and to move the support frame 10 on the subframe mounting rails 9. This allows the pile holder PH to move along the hull mounting rails 7 in the x direction and separately along the subframe mounting rails 9 in the y direction. This configuration allows the pile holder PH to be decoupled such that the synchronization of the movement of the pile holder PH to the monopile PI is performed in two steps, and furthermore, it allows the alignment of the pile holder PH to the monopile PI to maintain synchronization in the x direction with some deviation from synchronization in the y direction.

[0059] The illustrated embodiment of the support assembly 2 allows the pile holder PH to move in a horizontal plane relative to and independent of the support assembly 2 mounted on the hull HU. Other embodiments of the support assembly 2 allow the pile holder PH to move in a horizontal plane and are also included as part of the present invention.

[0060] The support assembly is provided with a motion actuator 3, which in this figure is provided near the hull mounting rail 7 and the subframe mounting rail 9 to drive the support assembly 2 on the rails. Furthermore, the pile holder PH in Figure 2 is provided with a bumper 13 to protect the pile holder PH from the impact of the monopile PI.

[0061] The motion actuator 3 is configured to move the pile holder PH relative to the ship hull (HU). By controlling the motion actuator 3, the pile holder PH is movable in a horizontal plane relative to the ship hull HU. As described herein, this mobility may enable synchronizing the movement of the pile holder PH with the monopile suspended from the crane during the gripping phase.

[0062] The motion actuators 3 are controlled by a motion control unit 4, e.g. a processor which sends control signals to the motion actuators 3. The motion control unit 4 in this figure is mounted on the support assembly 2. In an embodiment, the motion control unit 4 may be provided on another location of the vessel VE, e.g. on the bridge of the vessel VE. Furthermore, the pile holding device 1 comprises a monitoring system 5, which in this figure is provided on the support assembly 2.

[0063] In an embodiment, the monitoring system may be provided on the pile holder PH or on any other suitable location. For example, a first sensor of the monitoring system 5 may be provided on the first yaw Y1, a second sensor on the second yaw Y2, and a third sensor on the base structure BS.

[0064] In another example, one or more sensors of the monitoring system 5 may be provided on the support assembly 2 rather than on the pile holder PH, such as on a part of the support assembly 2 that is mounted directly to the pile holder and moves in line with the pile holder.

[0065] The monitoring system 5 is configured to monitor the position and movement of the suspended monopile PI relative to the pile holder PH in the horizontal plane during the gripping phase, in which the monopile PI is suspended from the crane CR and gripped by the pile holder PH.

[0066] For example, the monitoring system 5 comprises a number of sensors 6 for determining position and movement, mounted on the pile holder PH as shown in FIG.

[0067] In the illustrated embodiment, the monitoring system 5 comprises a sensor provided on the support assembly 2. For example, to determine the movement of the monopile PI, the monitoring system 5 determines the position of the monopile PI at multiple points in time, for example at regular time intervals, and correlates the position changes of the monopile PI to the movement of the monopile PI. For example, the monitoring system 5 is configured to determine the position and movement of the monopile PI with a frequency of more than 20 Hz, preferably more than 40 Hz, such as 50 Hz.

[0068] The monitoring system 5 is configured to transmit signals indicative of the monitored position and movement of the monopile relative to the pile holder PH to the motion control unit 4. This enables the motion control unit 4 to control the motion actuators based on the monitored position and movement of the monopile, and therefore the movement of the pile holder PH. As mentioned above, the motion control unit 4 may be provided at any suitable location on the vessel VE.

[0069] In an embodiment, the motion control unit 4 is adjacent to the monitoring system 5, for example adjacent to a central processing unit of the monitoring system 5. In another embodiment, the motion control unit 4 is located adjacent to the motion actuator 3.

[0070] FIG. 3 shows the pile holder PH in an open configuration, e.g. before gripping the monopile PI. The pile holder PH in FIG. 3 may be a different embodiment when compared to the pile holder in FIG. 2. In the embodiment shown in FIG. 3 of the pile holding device 1, the first yaw Y1 is pivotally connected to the base structure BS to pivot about a first yaw pivot axis, and the second yaw Y2 is pivotally connected to the base structure BS to pivot about a second yaw pivot axis. Both the first yaw Y1 and the second yaw Y2 are pivotable between their respective closed positions as shown in FIG. 1 and FIG. 2 and an open position as shown in FIG. 3. In this embodiment, the base structure BS, the first yaw Y1, and the second yaw Y2 for encircling the monopile are similar in size, i.e., both extend along a 120 degree arc-shaped trajectory to form a circle segment. This is best shown in FIG. 3 where the first yaw Y1 and the second yaw Y2 are in an open position. Other embodiments of the pile holder are also possible, for example where the first yaw Y1, the base structure BS and the second yaw Y2 differ in size.

[0071] In the open position, the monopile PI is able to move from and to the pile holder PH in a lateral direction, ie in the horizontal plane in which the pile holders move.

[0072] Four distance sensors 6 of the monitoring system 5 are provided on the base structure BS of the pile holder PH to monitor the position and movement of the monopile PI relative to the pile holder PH. This allows for an efficient measurement of the position of the monopile PI relative to the pile holder PH. For example, by measuring the position of the monopile PI multiple times during a certain time interval, it is possible to determine the movement of the monopile PI relative to the pile holder PH based on the measurements of the distance sensors 6. The distance sensors 6 have an overlapping field of view.

[0073] In this embodiment, the distance sensors 6 are line sensors 6, which measure the distance to the monopile PI on a line, for example a line located in the horizontal plane along which the pile holder PH moves, thereby making it possible to determine more accurately the distance of the pile holder PH to the monopile PI.

[0074] The distance sensors 6 are spaced apart from each other on the pile holder PH, for example mounted with non-parallel, e.g. vertical, fields of view towards the centre of the pile holder. For example, two sensors are mounted at either end of the base structure BS at different heights of the base structure BS.

[0075] The four distance sensors 6 allow a reliable triangulation of the position of the monopile PI even if one of them provides inaccurate data, e.g. due to shadow effects, malfunction or obstruction of the view. By being able to locate the centre of the pile holder PH within the field of view, the distance sensors 6 are able to determine the distance to the pile holder PH when its central axis is aligned with the centre of the pile holder. One advantage of providing the distance sensors 6 on the base structure BS compared to providing them on the yaws Y1, Y2 is that the field of view of the distance sensors 6 does not change when the pile holder PH is in either the open or closed configuration.

[0076] Preferably, the distance sensor 6 achieves / has a distance resolution of less than 1 cm, more preferably less than 5 mm, e.g. less than 3 mm. Preferably, the distance sensor 6 is capable of performing distance measurements at distances of more than 50 meters, e.g. more than 80 meters, for dark surfaces, e.g. with 10% reflectivity. Preferably, the distance sensor 6 is capable of performing distance measurements at distances of more than 100 meters, e.g. more than 200 meters, for bright surfaces, e.g. with 80% reflectivity.

[0077] FIG. 4 shows a monohull installation vessel 400 configured for installation of monopiles 410 configured to support offshore wind turbines.

[0078] The vessel 400 comprises a hull 401 , a crane 450 mounted on the hull, and a motion compensating pile holding device 500 .

[0079] The vessel 400 is configured to store one or more, preferably a plurality of, monopiles 410 in a horizontal orientation, e.g. on deck, for example, supported by a dedicated support structure. As shown, the monopiles 410 may be stored transverse to the longitudinal axis of the vessel, although storage parallel to said axis is preferred.

[0080] The device 500 is a motion compensation support assembly 510 mounted relative to the vessel hull; A pile holder 520 supported by a support assembly 510; Equipped with.

[0081] The motion compensated support assembly 510 is shown only very diagrammatically, as the various embodiments thereof will be familiar to those skilled in the art. In general, the assembly 510 comprises a controllable motion actuator and an associated motion control unit 530 configured to compensate for vessel motions by providing positional control of the monopile 410 during landing of the pile on the seabed and / or vertical control of the monopile 410 during driving of the monopile into the seabed.

[0082] Fig. 4 shows an embodiment in a schematic way. The support assembly 510 of the pile holding device 500 comprises one or more horizontal hull mounting rails mounted on the ship's hull, for example on the ship's deck, e.g. comprising an X-rail extending horizontally and in the longitudinal direction of the ship's hull. A subframe is movable on said one or more hull mounting rails, and one or more subframe mounting rails, e.g. one or more Y-rails extending horizontally and in the transverse direction of the ship's hull, are mounted on said subframe and vertically to said hull mounting rails. A support frame is movable on said subframe mounting rails, and a pile holder is mounted on said support frame. A controllable motion actuator of the support assembly is configured to move said subframe on the hull mounting rails and to move the support frame on the subframe mounting rails. For example, the motion actuator is embodied as a rack and pinion mechanism. For example, the pile holder 520 cannot tilt with respect to the support frame.

[0083] The vessel 400 is equipped with an erecting tool 600, different from the pile holding device 500, embodied for example to engage with the lower end portion of the monopile which remains in a horizontal position. The tool 600 supports the lower end during erecting, when the upper end of the monopile 410 is lifted by the crane 450.

[0084] The vessel 400 is configured to carry out a method, when the vessel's hull 401 is floating, comprising the following steps: Here, the step of operating the crane 450 to suspend and orient the monopile 410 in an upright orientation, with the lower end portion of the monopile being supported by the monopile erection tool 600 in the erection process. A step of engaging the monopile 410 suspended from the crane 450 with the pile holder 520. A step of lowering the monopile 410 by the crane 450 while being guided by the pile holder 520, and landing the monopile on the seabed. Driving the monopile 410 deeper into the seabed, for example with the use of a pile driver. The vessel 400 is equipped with a monitoring system configured to monitor the movement, e.g. the pendulum motion, of the suspended monopile 410, e.g. during the phase of bringing the lower end part of the monopile 410 into engagement with the pile holder 520.

[0085] The monitoring system transmits signals representative of the actual position and / or movement of the monopile 410. The monitoring system is linked to the motion control unit 530 such that these signals are transmitted to the motion control unit 530. The motion control unit 530 is configured to manage the controllable motion actuators of the device 500 in order to actively position the pile holder 520 with respect to the suspended monopile 410 during the engagement phase.

[0086] As discussed, the monopile 410 may experience pendulum motion prior to and during the engagement phase. For example, sea state induced movements and / or wind forces and / or crane movements (e.g., slewing) may cause pendulum motion of the monopile 410.

[0087] The monitoring and associated active positioning of the pile holder 520 relative to the (moving) monopile ensures that any contact during engagement does not lead to excessive loads and potential damage. A motion compensated support assembly is used to achieve the desired active positioning of the holder 520.

[0088] The monopile 410 can be inserted from above into a pile holder, such as one embodied with a ring and a pile guiding device. In another approach, the pile holder is opened laterally, whereby the monopile is introduced laterally into the pile holder, such as by swinging the crane 450.

[0089] In one embodiment, the monitoring system comprises a motion sensing system, eg, non-contact, based, eg, on one or more cameras 550 and / or based on one or more inertial-based motion sensors.

[0090] In one embodiment, the vessel 400 is equipped with one or more sensors configured to provide actual data regarding vessel motion, vessel position, operation of the dynamic positioning system, vessel stability, operation of the ballast system, etc. In an embodiment, the positioning of the pile holder 520 during the engagement phase is also controlled based on signals from these vessel related sensors.

[0091] In one embodiment, the vessel 400 is equipped with a wave prediction system, for example of the radar-based type. For example, a suitable time window for the engagement phase is determined or ascertained based on the wave prediction. [Explanation of symbols]

[0092] 1 Pile Retention Device 2 Support Assembly 3 Motion Actuator 4 Motion Control Unit 5. Monitoring System 6 Distance sensors, line sensors 7 Hull mounting rail 8 Subframe 9 Subframe mounting rail 10 Support frame 13. Bumper 400 Monohull Installation Vessel 401 Hull 410 Monopile 450 Crane 500 Motion Compensated Pile Retention Device 510 Motion Compensation Support Assembly 520 Pile Holder 530 Motion Control Unit 550 Camera 600 erection tool, monopile erection tool CR Crane HU Hull PI Monopile PH Pile Holder VE Ship Y1 First yaw Y2 Second yaw

Claims

1. 1. A method for installing monopiles configured to support an offshore wind turbine using an installation vessel, the method comprising: The hull and a crane mounted on the hull and configured to suspend the monopile; 1. A pile holding device comprising: a pile holder configured to grip the monopile when suspended from the crane; and a support assembly supporting the pile holder and attached to the hull of the ship, the support assembly configured to move the pile holder relative to the hull in a horizontal plane, the support assembly comprising: a motion actuator configured to move the pile holder relative to the hull in the plane; and a motion control unit for controlling the motion actuator of the support assembly. a pile holding device comprising: a monitoring system configured to monitor the position and movement of the suspended monopile relative to the pile holder in the horizontal plane during a gripping phase in which the monopile is suspended from the crane and gripped by the pile holder; Equipped with the monitoring system is configured to transmit signals to the motion control unit indicative of the position and the movement of the monopile relative to the pile holder, possibly in a situation where the hull of the vessel is floating; monitoring the position and movement of the suspended monopile relative to the pile holder using the monitoring system; sending signals to the motion control unit indicative of the position and movement of the monopile relative to the pile holder; operating the motion actuator under control of the motion control unit to synchronize movement of the pile holder relative to the support assembly with movement of the monopile based on the transmitted signal, wherein the step of synchronizing the movement of the pile holder with the movement of the monopile includes: first synchronizing the movement of the pile holder with the movement of the monopile in the x direction; then synchronizing the movement of the pile holder with the movement of the monopile in a y direction, the y direction being perpendicular to the x direction; operating the motion actuator under the control of the motion control unit to align the center of the pile holder with respect to a central axis of the monopile; gripping the monopile with the pile holder; A method comprising:

2. The method described in claim 1, wherein the x direction is along the longitudinal direction of the ship and the y direction is perpendicular to the longitudinal direction.

3. The monitoring system further comprises one or more sensors for providing actual data regarding one or more of vessel motions, vessel position, operation of a dynamic positioning system, vessel stability, operation of a ballast system of the vessel, and the method further comprises: transmitting signals from the one or more additional sensors to the motion control unit.

3. The method of claim 1 or 2, further comprising:

4. Suspending the monopile by the crane The grasping phase further includes: operating the crane to move the monopile towards the pile holder.

4. The method of claim 1, comprising:

5. 5. The method according to any one of claims 1 to 4, wherein the monitoring system comprises one or more distance sensors for measuring the distance and / or position of the monopile relative to the pile holder.

6. 6. The method of claim 5, wherein the monitoring system comprises two or more distance sensors each mounted on the pile holder, the distance sensors being spaced apart from one another on the pile holder, and two or more of the distance sensors having overlapping fields of view.

7. 7. The method of claim 1, wherein the support assembly comprises one or more horizontal hull mounting rails mounted on the hull of the ship, a subframe is movable on the one or more hull mounting rails, one or more subframe mounting rails are mounted on the subframe and perpendicular to the hull mounting rails, a support frame is movable on the subframe mounting rails, the pile holders are mounted on the support frame, and controllable motion actuators of the support assembly are configured to move the subframe on the hull mounting rails and to move the support frame on the subframe mounting rails.

8. An installation vessel for installing monopiles configured to support an offshore wind turbine using the installation vessel, comprising: The hull and a crane mounted on the hull and configured to suspend the monopile; 1. A pile holding device comprising: a pile holder configured to grip the monopile when suspended from the crane; and a support assembly supporting the pile holder and attached to the hull of the ship, the support assembly configured to move the pile holder relative to the hull in a horizontal plane, the support assembly comprising: a motion actuator configured to move the pile holder relative to the hull in the plane; and a motion control unit for controlling the motion actuator of the support assembly. a pile holding device comprising: a monitoring system configured to monitor the position and movement of the suspended monopile during a gripping phase in which the monopile is suspended from the crane and gripped by the pile holder; Equipped with the monitoring system is configured to transmit signals indicative of the position and the movement of the monopile; the monitoring system is configured to monitor the position and movement of the suspended monopile relative to the pile holder in the horizontal plane during a gripping phase in which the monopile is suspended from the crane and gripped by the pile holder; the monitoring system is configured to send signals to the motion control unit indicative of the position and the movement of the monopile relative to the pile holder; the motion control unit is configured to operate the motion actuator to synchronize movement of the pile holder relative to the hull with movement of the monopile based on the signal representing the position and the movement of the monopile, and the motion control unit is further configured to operate the motion actuator to align a center of the pile holder with a central axis of the monopile; the motion control unit is configured to first operate the motion actuator to synchronize movement of the pile holder with movement of the monopile in an x-direction, and thereafter operate the motion actuator to synchronize movement of the pile holder with movement of the monopile in a y-direction, the y-direction being perpendicular to the x-direction, of the installation vessel.

9. A vessel as described in claim 8, wherein the x direction is along the longitudinal direction of the vessel and the y direction is perpendicular to the longitudinal direction.

10. 10. A vessel as claimed in claim 8 or 9, wherein the monitoring system further comprises one or more sensors for providing actual data relating to one or more of vessel movements, vessel position, operation of a dynamic positioning system, vessel stability, operation of a ballast system of the vessel, and the monitoring system is configured to transmit signals from the one or more additional sensors to the motion control unit.

11. 11. A vessel according to any one of claims 8 to 10, wherein the crane is configured to turn the suspended monopile towards the pile holder for grasping the monopile by the pile holder.

12. 12. A vessel according to any one of claims 8 to 11, wherein the monitoring system comprises one or more distance sensors for measuring the distance and / or position of the monopile relative to the pile holder.

13. 13. The vessel of claim 12, wherein the monitoring system comprises two or more distance sensors, the distance sensors being spaced apart from one another, and two or more of the distance sensors having overlapping fields of view.

14. 14. The vessel of any one of claims 8 to 13, wherein the support assembly comprises one or more horizontal hull mounting rails mounted on the hull of the vessel, a subframe movable on the one or more hull mounting rails, one or more subframe mounting rails mounted on the subframe and perpendicular to the hull mounting rails, a support frame movable on the subframe mounting rails, the pile holders mounted on the support frame, and controllable motion actuators of the support assembly configured to move the subframe on the hull mounting rails and to move the support frame on the subframe mounting rails.

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