Method for installation of a monopile and installation vessel

A method for installation of a monopile adapted to support an offshore wind turbine, wherein use is made of an installation vessel comprising:

• a hull;
• a crane mounted on the hull and configured for suspending the monopile;
• a pile holding device, the pile holding device comprising:
• a pile holder configured to grip the monopile when suspended from the crane;
• and
• a support assembly which supports the pile holder and is mounted to the hull of the vessel, wherein the support assembly is configured to move the pile holder in a horizontal plane relative to the hull, and wherein the support assembly comprises motion actuators configured for causing a movement of the pile holder relative to the hull in said horizontal plane, and a motion control unit for controlling the motion actuators of the support assembly;
• and
• a monitoring system configured to, in a gripping phase wherein the monopile is suspended from the crane and is to be gripped by the pile holder, monitor a position and/or a movement of the suspended monopile in said horizontal plane relative to the pile holder,
• wherein the monitoring system is configured and operated to provide signals representative of the position and/or the movement of the monopile relative to the pile holder to the motion control unit,
• wherein the method comprises:
• monitoring with the monitoring system the position and/or the movement of the suspended monopile relative to the pile holder;
• providing signals representative of the position and/or the movement of the monopile relative to the pile holder to the motion control unit;
• operating under control of the motion control unit the motion actuators to synchronize a movement of the pile holder relative to the hull with the movement of the monopile based on the provided signals;
• operating under control of the motion control unit the motion actuators to align a center of the pile holder with a central axis of the monopile;
• and
• gripping the monopile by the pile holder.

An installation vessel for installation of a monopile adapted to support an offshore wind turbine, the installation vessel comprising:

• a hull;
• a crane mounted on the hull and configured for suspending the monopile;
• a pile holding device, the pile holding device comprising:
• a pile holder configured to grip the monopile when suspended from the crane;
• and
• a support assembly which supports the pile holder and is mounted to the hull of the vessel, wherein the support assembly is configured to move the pile holder in a horizontal plane relative to the hull, and wherein the support assembly comprises motion actuators configured for causing movement of the pile holder relative to the hull in said horizontal plane, and a motion control unit for controlling the motion actuators of the support assembly;
• and
• a monitoring system configured to, in a gripping phase wherein the monopile is suspended from the crane and is to be gripped by the pile holder, monitor a position and/or a movement of the suspended monopile in said horizontal plane relative to the pile holder,
• wherein the monitoring system is configured to provide signals representative of the position and/or the movement of the monopile relative to the pile holder to the motion control unit,
• wherein the motion control unit is configured to operate the motion actuators to synchronize a movement of the pile holder with a movement of the monopile relative to the hull based on the signals representative of the position and/or the movement of the monopile, and
• wherein the motion control unit is further configured to operate the motion actuators to align a center of the pile holder with a central axis of the monopile.

A method for installation of a monopile adapted to support an offshore wind turbine, wherein use is made of an installation vessel comprising:

• a hull;
• a crane mounted on the hull;
• and
• a motion compensating pile holding device, the device comprising:
• a motion compensating support assembly mounted to the hull of the vessel;
• and
• a pile holder that is supported by the support assembly, wherein the motion compensating support assembly comprises controllable motion actuators and an associated motion control unit configured for position control of the monopile during landing of the pile on a seabed and/or for control of verticality of the monopile during driving of the monopile into a seabed so as to compensate for vessel motion,
• wherein the method comprises:
• operating the crane so as to bring the monopile in a suspended and upended orientation;
• a phase of bringing the suspended monopile into engagement with the pile holder;
• lowering the monopile by means of the crane whilst being guided by the pile holder so that the monopile is landed on the seabed;
• and
• driving the monopile deeper into the seabed involving the use of pile driving equipment,
• wherein, during the phase of bringing the suspended monopile into engagement with the pile holder, the motion of the monopile is monitored by a monitoring system providing signals representative of actual position and/or motion of the monopile, and the signals are supplied to the motion control unit of the motion compensating pile holding device, which governs, during the phase of bringing the suspended monopile into engagement with the pile holder, the controllable motion actuators in order to actively position the pile holder with the suspended monopile.