Patent Description:
In a known method for installing an offshore wind turbine, the foundation, in the form of a pile, is installed first by driving the pile into the sea bottom after which the wind turbine is installed on the pile, either by installing the wind turbine at once as a whole or by assembling the wind turbine in parts on the pile.

There is a trend towards larger wind turbines and a desire to install offshore wind turbines at locations with larger water depths than currently encountered. Both result in larger and heavier foundations. Hence, it is expected that in the near future piles need to be installed that are larger than <NUM> meters, possibly <NUM> meters or larger. The weight of such piles may be larger than 1000mt, possibly 1300mt or above.

<CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose prior art assemblies for gripping and handling pipes or piles, wherein <CIT> represents the closest prior art.

Installation of piles is currently done using jack-up type vessel in which legs are lowered into the water to lift the vessel at least partially out of the water so that waves have a limited or minimal effect on the vessel. However, a drawback of such a jack-up type vessel is that it takes a lot of time to lower the legs and to lift the vessel out of the water and to go through the reverse process after installation of the pile.

<CIT> discloses such prior art method, wherein damping is provided between the pile holder and a jack-up vessel for damping swinging motions of the pile. This prior art also suffers from the issue with regard to the time the process of lifting and lowering of the vessel takes.

<CIT> discloses a floating vessel provided with a pile holder that is configured to support the pile at an angle to the vertical whilst being driven into the pile into the seabed.

It is therefore an object of the invention to provide a faster method to install a pile adapted to support an offshore wind turbine.

This object is achieved by providing a method for installation of a pile adapted to support an offshore wind turbine, comprising the following steps:.

The invention is based on the insight that installation of the pile while keeping the vessel in floating condition, thereby obviating the need of lowering legs, will result in a huge increase of speed of the installation method. This insight is not obvious as it introduces the problem of wave-induced motion of the vessel. This problem is partially solved by compensating the pile holder for wave-induced motion of the vessel to maintain a predetermined X-Y location independent of the wave-induced motion of the vessel during lowering of the pile. However, the inventors have further realized that motions of the vessel caused by handling of the pile prior to lowering the pile into the water and introducing a pile into the pile holder while being confronted with vessel motions may pose a further problem. Therefore, the method also allows to upend the pile with the pile already being positioned in the pile holder and with the pile initially being oriented parallel to the longitudinal axis of the vessel. When the pile is then upended about a rotation axis perpendicular to the longitudinal axis of the vessel, e.g. over the stern of the vessel, the effect of the weight shift of the pile on the vessel motion is minimal.

In an embodiment, the installation vessel also carries out step a. of the method, namely transporting a pile in a horizontal orientation to an offshore installation site. However, it is also possible that the pile is transported by a separate vessel or barge.

(positioning the pile in the pile holder) and/or step c. (lifting an upper end portion of the pile) are carried out by a crane on the installation vessel.

The pile holder is mounted on the vessel to rotate relative to the vessel about the horizontal rotation axis between a receiving position to receive a horizontal orientation and a lowering position in which the pile can be lowered into the water while being in a substantially vertical orientation, wherein in step b. the pile holder is in the receiving position, and wherein in step c. the pile holder is moved along with the pile to the lowering position.

In an embodiment, the pile holder comprises a pile support to engage with the lower end of the pile in order to limit movement of the pile in a direction parallel to the longitudinal axis of the pile, wherein step d. , disengaging the pile holder from the lower end of the pile, comprises the steps:.

In an embodiment, step e. , lowering the pile in to the water by being held by the pile holder, comprises the steps:.

Preferably, step e1. is carried out by the crane on the installation vessel, wherein more preferably during at least a part, e.g. the last part, of the lowering in step e1. the upper end portion of the pile is compensated for wave-induced motion of the vessel to maintain a predetermined X-Y location independent of the wave-induced motion of the vessel.

Preferably during at least a part of the lowering in step e1. , the pile is compensated for wave-induced motion of the vessel to maintain a predetermined Z location independent of the wave-induced motion of the vessel. This may alternatively be referred to as heave compensation.

In an embodiment, the crane on the installation vessel is arranged at the stern of the installation vessel and aligned with the centre of gravity of the installation vessel, and wherein the pile holder is arranged at the stern of the installation vessel next to the crane. In an embodiment, in step c. , lifting an upper end portion of the pile thereby rotating the pile from a horizontal to a vertical orientation, it is prevented that the center of mass of the pile unintentionally continues its rotation to some extent after being vertically oriented, thereby toppling forwards with its upper end portion directed horizontally away from the vessel.

The invention will now be described in a non-limiting way by reference to the accompanying drawings in which like parts are indicated by like reference symbols, and in which:.

<FIG> depict a pile holding system <NUM>. The pile holding system comprises a base frame <NUM> to be mounted on a vessel as depicted in <FIG> and <FIG>.

The base frame <NUM> is integrated in or with a deck of the vessel. Alternatively, the base frame may be moveable, e.g. slidable or skiddable, relative to the deck, so that the pile holding system may for instance be moveable between a retracted position in which the pile holding system is arranged inside a contour of the vessel seen from above, and an operational position in which the pile holding system is arranged at least partially outside the contour of the vessel seen from above.

The pile holding system <NUM> further comprises a support frame <NUM> that is moveably supported by a support system at a distance from the base frame <NUM>. The support system comprises four vertical beams <NUM>, <NUM>, <NUM>, <NUM> which are equal in length and extending between the base frame <NUM> and the support frame <NUM>. In <FIG>, the beams <NUM>, <NUM>, <NUM>, <NUM> extend mainly in the Z-direction.

One end of each beam <NUM>, <NUM>, <NUM>, <NUM> is connected to the base frame <NUM> and the respective opposite end is connected to the support frame <NUM>. The ends of the beams <NUM>, <NUM>, <NUM>, <NUM> are connected to the respective base frame <NUM> and support frame <NUM> using a universal joint with a pair of hinges located close together, oriented at <NUM> degrees to each other, and connected by an intermediate member. The universal joint may alternatively be referred to as cardan joint.

Hence, each beam is able to hinge about a first hinge axis extending in X-direction relative to the base frame, a second hinge axis extending in Y-direction relative to the base frame, a third hinge axis extending in X-direction relative to the support frame and a fourth hinge axis extending in Y-direction relative to the support frame. For simplicity reasons, the following table indicates the reference symbols used in the drawings.

Hence, the first hinge axis is orthogonal to the second hinge axis and parallel to the third hinge axis. The fourth hinge axis is orthogonal to the third hinge axis and parallel to the second hinge axis. As a result, the support frame <NUM> is able to be moved parallel to the base frame <NUM> in both X- and Y-direction, i.e. in an X-Y plane.

In order to move the support frame <NUM> relative to the base frame <NUM> in the X-Y plane, an active motion compensated actuation system is provided. In this embodiment, the actuation system comprises two first actuators, in this case two first hydraulic cylinders <NUM>, to move the support frame <NUM> in the Y-direction relative to the base frame <NUM> by pivoting the beams about their respective first and third hinge axes. The actuation system further comprises two second actuators, in this case two second hydraulic cylinders <NUM>, to move the support frame <NUM> in the X-direction relative to the base frame <NUM> by pivoting the beams about their relative second and fourth pivot axes.

The first actuators <NUM> are arranged between the base frame <NUM> and the support frame <NUM>, so that the first actuators <NUM> are also connected to the respective base frame <NUM> and the support frame <NUM> using universal joints similar as the beams, so that the support frame can move relative to the base frame without being interfered by the first actuators. The position of the support frame <NUM> in Y-direction relative to the base frame <NUM> is then set by the length of the first actuators <NUM>.

One of the second actuators <NUM> is arranged between the beams <NUM> and <NUM>, and the other one of the second actuators <NUM> is arranged between the beams <NUM> and <NUM>. An advantage thereof is that the second actuators only need to be hingedly connected to the beams about hinge axes that are parallel to the second and fourth hinge axes of the beams. The position of the support frame <NUM> in X-direction relative to the base frame <NUM> is then set by the length of the second actuators <NUM>.

As shown in <FIG>, the support frame <NUM> may be provided with a platform <NUM> allowing personnel to walk over the support frame <NUM>. The platform <NUM> may be accessible via a construction <NUM> comprising a stair or ladder 22a between deck level and platform <NUM> level and a gangway 22b between the stair or ladder 22a an the platform <NUM>. The gangway 22b is suspended just above the platform <NUM> without being fixed to the platform <NUM>, so that the platform <NUM> can freely move below the gangway in the X-Y plane along with the support frame <NUM>.

The system <NUM> further comprises a pile holder <NUM> mounted on the support frame <NUM>, which pile holder <NUM> is configured to engage with a pile in order to hold the pile and to allow the pile to move in a direction parallel to a longitudinal axis of the pile relative to the pile holder <NUM> as will be explained below in more detail.

The pile holder <NUM> comprises a base structure <NUM> mounted to the support frame <NUM>. In this embodiment, the base structure <NUM> is pivotably mounted to the support frame <NUM> to pivot relative to the support frame <NUM> about base pivot axis <NUM> between a substantially vertical orientation as depicted in <FIG> and a substantially horizontal orientation as depicted in <FIG>, <FIG>.

The pile holder <NUM> comprises two actuators, in this case two hydraulic cylinders <NUM>, <NUM>, that are arranged between the support frame <NUM> and the base structure <NUM> to move the base structure <NUM>, i.e. the pile holder <NUM>, between the vertical and horizontal orientation. As a result thereof, the pile holder can be retracted when not in use and/or the pile holder can be used to upend a pile as will be explained later in more detail.

Cylinders <NUM> and <NUM> are adapted to brake a toppling movement of the pile holder and the pile held therein, when rotating a pile from a horizontal to a vertical orientation using the pile holding system. This toppling movement being that, starting from the vertical orientation of the pile, the center of mass of the pile moves forwardly, away from the vessel - that is, wherein the pile topples with its upper end portion moving horizontally away from the vessel.

At each end of the base structure <NUM>, a respective arm <NUM>, <NUM> is provided. The arms <NUM>, <NUM> are pivotably mounted to the base structure <NUM> to pivot relative to the base structure <NUM> about respective arm pivot axis <NUM>, <NUM> between an open position as depicted in <FIG>, <FIG> and <FIG> and one or more closed positions as depicted in <FIG> and <FIG>.

The pile holder <NUM> comprises a driving mechanism that is operable on the two arms <NUM>, <NUM> to move the arms about the arm pivot axes <NUM>, <NUM> between the open position for receiving a pile and a closed position. In this embodiment, the driving mechanism comprises two hydraulic actuators <NUM>, <NUM>.

Each arm <NUM>, <NUM> is provided with a respective jaw <NUM>, <NUM>. The jaw <NUM> is pivotably mounted to arm <NUM> to pivot relative to the arm <NUM> about a jaw pivot axis <NUM>. The jaw <NUM> is pivotably mounted to arm <NUM> to pivot relative to the arm <NUM> about a jaw pivot axis <NUM>.

Each jaw <NUM>, <NUM> is provided with at least two distinct piling engaging portions <NUM>, <NUM>, <NUM>, <NUM> in this embodiment in the form of single rollers.

Although it is possible to provide separate actuators to pivot the jaws <NUM>, <NUM> about their respective jaw pivot axis <NUM>, <NUM>, the jaws <NUM>, <NUM> are in this embodiment automatically moved and positioned by the driving mechanism <NUM>, <NUM> moving and positioning the arms <NUM>, <NUM> due to the provision of a kinematic linkage for each jaw <NUM>, <NUM> that is configured to cause movement of the jaw during and as a result of movement of the respective arm.

The kinematic linkage for jaw <NUM> comprises a beam <NUM> connecting the jaw <NUM> to the base structure <NUM>. One end of beam <NUM> is hingeably connected to the jaw <NUM> at a distance from the jaw pivot axis <NUM> while the opposite end of beam <NUM> is hingeably connected to the base structure <NUM> at a distance from the arm pivot axis <NUM> thereby forming a four bar linkage consisting of (portions of) the base structure <NUM>, the arm <NUM>, the jaw <NUM> and the beam <NUM>.

The kinematic linkage for jaw <NUM> comprises a similar beam <NUM> connecting the jaw <NUM> to the base structure <NUM>. One end of beam <NUM> is hingeably connected to the jaw <NUM> at a distance from the jaw pivot axis <NUM> while the opposite end of beam <NUM> is hingeably connected to the base structure <NUM> at a distance from the arm pivot axis <NUM> thereby forming a four bar linkage consisting of (portions of) the base structure <NUM>, the arm <NUM>, the jaw <NUM> and the beam <NUM>.

Hence, upon rotation of the arms <NUM>, <NUM>, the respective four bar linkages will cause the respective jaws <NUM>, <NUM> to rotate relative to the arms <NUM>, <NUM> about the jaw pivot axes <NUM>, <NUM>. An advantage of the kinematic linkages is that the jaws will face more towards each other during opening and closing of the pile holder compared to jaws that are fixed to the arms. This will improve the engagement and disengagement of the jaws with the pile. Further, more space is available to receive a pile in the open position as can be best seen in <FIG> and <FIG>. Due to the four bar linkage, the pile engaging portions <NUM> and <NUM> are retracted to lie almost entirely within the respective arms <NUM>, <NUM>. The arms <NUM>, <NUM> are designed as forks with the respective jaw being arranged in between the forks to allow the free rotation of the jaw about the respective jaw pivot axis and to allow the pile engaging portions <NUM>, <NUM> to be received in between the forks.

Another advantage of the four bar linkages may be that in at least one closed position there is a moving range of the arms <NUM>, <NUM> around the at least one closed position allowing the pile holder to hold piles having a different diameter or allowing the pile holder to hold a pile having a varying diameter along its length in different locations while the longitudinal axis of the different piles or the varying diameter pile remains substantially at the same position relative to the base structure.

As an example, the arms <NUM>, <NUM> are depicted in different positions. The open position is already described in relation to <FIG>, <FIG> and <FIG>. <FIG> depict two different closed positions, each for a different diameter. In <FIG>, the jaws <NUM>, <NUM> are closer to each other than in <FIG>, so that the closed position of <FIG> allows to hold a smaller diameter pile or pile portion than the closed position of <FIG> may also be an intermediate position when moving from the closed position in <FIG> and the open position.

The pile holder <NUM> further comprises a pile support <NUM> arranged on a support beam <NUM> which is pivotably connected to the base structure <NUM> to pivot relative to the base structure <NUM> about a beam pivot axis <NUM>. For simplicity reasons, the pile support <NUM> and support beam <NUM> are only shown in <FIG>, <FIG>.

In order to move and position the support beam <NUM> about the beam pivot axis <NUM>, an actuator, in this case a hydraulic cylinder <NUM>, is provided between the base structure <NUM> and the support beam <NUM>. The actuator <NUM> allows to move the pile support between an operational position in which the pile support is able to engage with a pile and a retracted position in which the pile support allows the free passage of a pile through the pile holder <NUM>. The pile support <NUM> is configured to engage with a lower end of a pile in the operational position in order to limit movement of the pile in a direction parallel to a longitudinal axis of the pile and preferably also in a direction perpendicular to the longitudinal axis of the pile. This allows the pile support to provide additional support to the pile during upending of the pile as will be explained below in more detail.

The pile holder <NUM> is further provided with a platform <NUM> on the base structure <NUM>, a platform <NUM> on the arm <NUM>, and a platform <NUM> on the arm <NUM> of the pile holder <NUM>. This allows personnel to reach the pile holder, e.g. for inspection of the pile holder, but also for inspection of the pile in the pile holder.

A stair <NUM> is provided between platform <NUM> on the support frame <NUM> and the platform <NUM> on the base structure <NUM>. It is further possible to get on the platforms <NUM> and <NUM> from the platform <NUM>. At the platform <NUM> side of the stair <NUM>, the stair <NUM> is supported from the platform by wheels and on the pile holder side the stair <NUM> is pivotally mounted to the base structure <NUM>, so that when the pile holder is rotated towards the vertical orientation as depicted in <FIG>, the stair <NUM> moves easily over the platform <NUM>.

The base structure <NUM> of the pile holder <NUM> is further provided with a bumper <NUM>, in this embodiment having a V-shape, allowing to engage with a pile when the arms are in the open position. The bumper <NUM> protects the base structure and may comprise resilient or spring-like components to absorb collision forces, but the bumper may additionally or alternatively be used as a temporary support for a pile when the pile holder is in a vertical orientation and a pile is introduced into the pile holder in a substantially horizontal position. Once the arms of the pile holder are closed and the pile engaging portions engage with the pile, the bumper preferably disengages from the pile. The bumper is moveable in a direction parallel to a plane spanned by the arms and jaws and perpendicular to the base structure thereby allowing to position the pile in between the arms and/or allowing to actively engage and disengage from the pile.

The bumper is for simplicity reasons not shown in every drawing, but can be clearly seen in <FIG>, <FIG>.

The pile holding system <NUM> further comprises a control unit <NUM>, which is schematically depicted in <FIG> only. The control unit <NUM> controls at least the first and second actuators <NUM>, <NUM>, but may, as in this embodiment, also control all other actuators shown in the drawings.

The control unit <NUM> provides an active wave-induced motion compensation mode in which the actuation system is operated to maintain a predetermined X-Y location of the pile holder <NUM> independent of the wave-induced motion of the vessel. This provides many advantages which will be described below in more detail.

<FIG> depict an alternative epile holding system <NUM>.

The pile holding system is similar to the pile holding system <NUM> of <FIG> with the main difference that the jaws <NUM>, <NUM> are embodied differently. Due to the similarity between the two pile holding systems, the identical or similar components are not described again below. Reference is made to the description related to <FIG>. The description below in relation to the <FIG> therefore focuses on the differences between the two embodiments.

The jaws <NUM>, <NUM> according to <FIG> each comprise two fixed pile engaging portions <NUM>, <NUM>, <NUM>, <NUM> in the form of single rollers. The jaws <NUM>, <NUM> according to <FIG> each comprise two swivelling pile engaging portions <NUM>, <NUM>, <NUM>, <NUM> that can freely swivel about respective swivel axes 71c, 72c, 73c and 74c. Each pile engaging portion further comprises two rollers to engage with the pile. Pile engaging portion <NUM> comprises rollers 71a, 71b, pile engaging portion <NUM> comprises rollers 72a, 72b, pile engaging portion <NUM> comprises rollers 73a, 73b, and pile engaging portion <NUM> comprises rollers 74a, 74b.

In <FIG>, the support frame <NUM>, and thus the pile holder <NUM>, is in an equilibrium position. The equilibrium position can be defined as the position in which the beams <NUM>-<NUM> are perpendicular to plans spanned by the support frame <NUM> and the base frame <NUM>.

<FIG> depict the moving possibilities. In <FIG>, the first actuators <NUM> are fully extended thereby moving the support frame in a negative Y-direction relative to the equilibrium position. In <FIG>, the first actuators <NUM> are fully retracted thereby moving the support frame in a positive Y-direction relative to the equilibrium position. In <FIG>, the second actuators <NUM> are fully retracted thereby moving the support frame in a negative X-direction relative to the equilibrium position. In <FIG>, the second actuators <NUM> are fully extended thereby moving the support frame in a positive X-direction relative to the equilibrium position.

The described moving possibilities and the equilibrium position also apply to the embodiment of <FIG> and allows to move the support frame <NUM> in the X-Y plane thereby allowing the wave-induced motion compensation mode of the control unit.

The above pile holding systems <NUM> can be used in a method that will be described below by reference to <FIG>. The pile holding system <NUM> shown in <FIG> and <FIG> is similar to the pile holding system <NUM> of <FIG>.

<FIG> and <FIG> depict a vessel <NUM> with a deck <NUM>. The deck <NUM> provides sufficient space to store, in this case, five piles <NUM> in a horizontal orientation. The piles <NUM> are stored such that their longitudinal axes are parallel to a longitudinal axis of the vessel <NUM>.

The vessel <NUM> is a monohull vessel, but alternatively, the vessel could be a semi-submersible. In a non-shown embodiment, the vessel is a jack-up type vessel in which legs can be lowered into the water to lift the vessel at least partially out of the water so that waves have a limited or minimal effect on the vessel. The vessel can then be used in floating condition when the weather and wave conditions are good and can be used in jack-up condition when the weather and wave conditions are bad.

At a stern of the vessel is provided a crane <NUM>. The crane <NUM> is arranged in a centre of the deck <NUM> seen in transverse direction of the vessel <NUM> to be aligned with a centre of gravity of the vessel <NUM>. On one side the pile holding system <NUM> is arranged and on an opposite side of the crane <NUM>, a pile driving mechanism <NUM> is arranged at a corresponding storage location.

The pile holding system <NUM> is arranged such that the base pivot axis <NUM>, which may alternatively be referred to as rotation axis <NUM>, is oriented horizontally but perpendicular to the longitudinal axis of the vessel <NUM>.

When the vessel <NUM> has sailed to an offshore installation site where a pile <NUM> needs to be installed into the sea bottom, a pile <NUM> is positioned in the pile holder <NUM> of the pile holding system <NUM> while the pile holder <NUM> is in the vertical position of <FIG>, which may also be referred to as the receiving position as it allows to receive a pile in a horizontal orientation.

The arms <NUM>, <NUM> of the pile holder <NUM> are moved to the open position and the pile <NUM> can be positioned in the pile holder <NUM> to rest on the bumper <NUM>. The arms <NUM>, <NUM> are then closed such that the pile engaging portions <NUM>, <NUM>, <NUM>, <NUM> of the jaws <NUM>, <NUM> engage with the circumference of the pile <NUM> at a lower side thereof. The pile is then preferably lifted from the bumper <NUM>.

The pile support <NUM> on the pile holder <NUM> is also brought into the correct position and in this case using a translation of the pile <NUM> parallel to the longitudinal axis of the pile <NUM>, the lower end of the pile <NUM> engages with the pile support <NUM>.

As a result thereof, movement of the lower side of the pile <NUM> in a direction perpendicular to the longitudinal axis of the pile <NUM> and movement of the pile <NUM> in a direction parallel to the longitudinal axis of the pile <NUM> is limited.

The upper end of the pile <NUM> is then lifted using the crane <NUM> with the lower side in the pile holder <NUM> thereby rotating the pile <NUM> from a horizontal orientation to a vertical orientation as shown in <FIG>. <FIG> shows the pile <NUM> in an intermediate oblique orientation between the horizontal orientation and the vertical orientation.

After rotating, the pile holder <NUM> is in the horizontal position, which may alternatively be referred to as lowering position, and the pile <NUM> is located outside the contour of the vessel <NUM>, i.e. overboard, seen from above to be lowered into the water as can be seen in <FIG>. The pipe holder <NUM> and the pile <NUM> are now in the stern side of the vessel <NUM>.

Before lowering the pile <NUM> into the water, the lower end of the pile <NUM> needs to be disengaged from the pile support <NUM>. The pile <NUM> is in that case lifted first after which the pile support <NUM> can be moved out of the way. The pile <NUM> can then be lowered into the water.

During the above operations, the vessel is in floating condition, and during lowering the pile holder <NUM> is compensated for wave-induced motion of the vessel <NUM> to maintain a predetermined X-Y location independent of the wave-induced motion of the vessel <NUM> by operating the control unit <NUM> of the pile holding system <NUM> in wave-induced motion compensation mode.

When lowering the pile <NUM> into the water, the pile <NUM> is initially held by the crane <NUM> and gravity forces will initially drive the pile <NUM> into the sea bottom when the pile <NUM> reaches the sea bottom. When this stops, the crane <NUM> can be disengaged from the pile <NUM> and the pile driving mechanism <NUM> can be lifted by the crane <NUM> to be position on top of the pile <NUM> to actively drive the pile <NUM> deeper into the sea bottom by applying downwardly directed forces to the upper end portion of the pile <NUM>.

When the pile is lowered into the water and suspended from the crane <NUM>, the crane may be operated in wave-induced motion compensation mode so that the upper end of the pile <NUM> is compensated for wave-induced motion of the vessel to maintain a predetermined X-Y location independent of the wave-induced motion of the vessel. This allows to keep the pile <NUM> in a substantially vertical orientation during lowering.

Alternatively or additionally, the crane may be operated in wave-induced motion compensation mode so that the pile <NUM> is compensated for wave-induced motion of the vessel to maintain a predetermined Z location independent of the wave-induced motion of the vessel. This may also be referred to as heave compensation.

In order to lift the upper end of the pile <NUM> to rotate the pile from a horizontal orientation to a vertical orientation, the crane is provided with a pile clamping device <NUM> comprising a clamping part <NUM> to clamp the upper end of the pile <NUM> and a connecting part <NUM> allowing to connect the pile clamping device to a load connector <NUM> of the crane <NUM>. The connecting part <NUM> is able to rotate freely relative to the clamping part <NUM> during lifting of the upper end, i.e. during rotating of the pile.

<FIG> depicts another wave-induced motion compensated pile holding system to be mounted on a vessel, e.g. for installation of a pile adapted to support an offshore wind turbine.

The pile holder <NUM> comprises a base structure <NUM> mounted to the support frame <NUM>. In this embodiment, the base structure <NUM> is pivotally mounted to the support frame <NUM> to pivot relative to the support frame <NUM> about base pivot axis <NUM> between a substantially vertical orientation and a substantially horizontal orientation. In this example it is envisaged that this tilting is only in view of sailing with the vessel, mooring in a port, etc., as it is envisaged that a pile is hoisted by a crane and placed in vertical orientation before engagement thereof by the pile holder <NUM>.

The pile holder <NUM> has an annular structure of which a section is formed by the base structure <NUM>, and of which the remainder is formed by two semi-circular jaws <NUM>, <NUM>. These jaws <NUM>, <NUM> are each pivotally connected at an inner end thereof to a respective pivot part of the base structure <NUM> and pivotal about a pivot axis <NUM>, <NUM> between a closed position, wherein outer ends of the jaws <NUM>, <NUM> join up, and an opened position. The actuation of each jaw <NUM>, <NUM> is done by a jaw actuator, e.g. a hydraulic cylinder <NUM>. A locking mechanism <NUM> is preferably provided to lock the outer ends of the semi-circular jaws <NUM>, <NUM> to one another.

The annular structure of the pile holder <NUM>, as preferred, is provided with a circular support track structure <NUM> that carries multiple pile engaging devices <NUM>, here with pile guiding rollers <NUM>, e.g. four or more, here six, of such devices.

The pile engaging devices <NUM> are movable along the circular support track structure, at least one or more of them, at least over an arc segment of the circle, so as to allow for adaptation of the angular position of the pile engaging devices <NUM> relative to the passage for the pile.

Each pile engaging device <NUM>, as preferred, carries one or more, here a pair of two, pile guiding rollers <NUM> in a movable manner allow for adjustment of the radial position of the rollers <NUM> relative to the passage for the pile. Here each pile engaging device comprises a suspension arm <NUM> that pivotal about a horizontal axis <NUM>, here as preferred from a top end of the arm <NUM>, relative to a chassis <NUM> of the device that is supported on the track structure <NUM>.

A suspension arm actuator, here a hydraulic cylinder <NUM>, is provided between the chassis <NUM> and the arm <NUM> to adjust the radial position of the roller(s) <NUM>.

Each chassis <NUM> here is provided with a motorized drive adapted to move the chassis <NUM> along, possibly a section of, the circular track structure so as to adjust the angular position of the device <NUM>.

Claim 1:
A method for installation of a pile (<NUM>) adapted to support an offshore wind turbine, comprising the following steps:
a. transporting the pile (<NUM>) in a horizontal orientation to an offshore installation site;
b. positioning the pile in a pile holder (<NUM>) on an installation vessel (<NUM>) while being in a horizontal orientation parallel to a longitudinal axis of the vessel (<NUM>), wherein the pile holder (<NUM>) engages with a circumference of the pile at a lower side thereof to hold the pile in order to limit movement of the lower side of the pile in a direction perpendicular to a longitudinal axis of the pile, and wherein the pile holder engages with a lower end of the pile in order to limit movement of the pile in a direction parallel to the longitudinal axis of the pile;
c. lifting an upper end portion of the pile with the lower side in the pile holder thereby rotating the pile from a horizontal orientation to a vertical orientation about a substantially horizontal rotation axis perpendicular to the longitudinal axis of the vessel, wherein after rotating the pile from the horizontal orientation to the vertical orientation the pile is located outside the contour of the vessel seen from above to be lowered into the water;
d. disengaging the pile holder from the lower end of the pile;
e. lowering the pile into the water while being held by the pile holder,
wherein during steps b. to e. the vessel is in a floating condition,
and wherein during step e. the pile holder is compensated for wave-induced motion of the vessel to maintain a predetermined X-Y location of the pile holder independent of the wave-induced motion of the vessel,
wherein step b. and/or step c. are carried out by a crane (<NUM>) on the installation vessel (<NUM>), and
wherein the pile holder (<NUM>) is mounted on the vessel (<NUM>) to rotate relative to the vessel about the horizontal rotation axis between a receiving position to receive the pile (<NUM>) in a horizontal orientation and a lowering position in which the pile can be lowered into the water while being in a substantially vertical orientation, wherein in step b. the pile holder is in the receiving position, and wherein in step c. the pile holder is moved along with the pile to the lowering position.