In an installation of a wind turbine on a floating foundation in floating condition and subject to sea-state induced motions, e.g. at the site of an offshore windfarm, use is made of a vessel with a crane arranged on the hull and provided with a hoisting system adapted to support the weight of the wind turbine and suspend the wind turbine from the crane. A heave compensation device compensates for sea-state induced heave motion of the wind turbine mast relative to the mast mounting structure of the floating foundation. Use is made of a mast alignment system configured to engage on the suspended wind turbine, e.g. on the mast of the suspended wind turbine, and to bring and maintain the mast of the wind turbine in alignment with the mounting axis of the floating foundation in order to compensate for sea-state induced motions, at least including tilt motions in one or more vertical planes, of the wind turbine mast relative to the mounting axis of the floating foundation.

A method of assembling a wind turbine tower by stacking a plurality of annular sections made of concrete above each other. The main connections are performed between two adjacent annular sections, for withstanding loads induced by a rotor. The auxiliary connections are performed between two adjacent annular sections, for withstanding loads induced by an earthquake and loads induced by the wind on the wind turbine in absence of the rotor, but not necessarily loads induced by the rotor. The method is characterized in that the auxiliary connections between two adjacent annular sections are performed prior to stacking the following annular section.

An apparatus is for performing a part of an operation to install a tower for a wind turbine, wherein the wind turbine has a tower, wherein the apparatus has a travelling car for travelling up and down along the tower of the wind turbine and for carrying an item to be installed as part of the wind turbine, wherein the travelling car has a device for balancing the travelling car, and wherein the device for balancing the travelling car has a weight configured to be movably connected to the travelling car i) for allowing keeping the travelling car balanced under exposure to a force or ii) for avoiding, correcting or reducing a shift in a centre of gravity of the travelling car. Further is disclosed a method of balancing a travelling car for an apparatus for performing at least a part of an operation to install a wind turbine.

An apparatus is for performing parts of an operation to install a wind turbine, wherein the wind turbine has a tower, wherein i) the tower has a plurality of sections of the tower; ii) installation of the tower includes stacking the sections; iii) during the installation the tower has an installed part of the tower and sections of the tower yet to be installed; and iv) the installed part of the tower includes one or more installed sections of the tower. The apparatus comprises a travelling car for being selectively raised or lowered along the tower and a device for selectively raising or lowering the travelling car. The device for selectively raising or lowering the travelling car is arranged to connect the travelling car to an uppermost installed section of the tower.

A tool (600) for aligning tubular structures (200, 300) of a wind turbine comprises: a plurality of hanger members (601) configured to be pivotably attached to an end region of a first tubular structure (300) so as to extend axially outward therefrom, each of the hanger members comprising a guide part (605) adapted to engage an interior wall (203) of a second tubular structure (200); at least one cable (615) connecting the hanger members (601) together; and a tension mechanism arranged to adjust a tension of the at least one cable (615). The tension mechanism is operable to adjust said tension to pivot the guide parts (605) into engagement with the interior wall (203) of the second tubular structure (200) when the first tubular structure (300) is moved axially toward the second tubular structure (200), thereby to guide the first tubular structure (300) into axial alignment with the second tubular structure (200).

A pile displacement system includes a first subsystem, and a second subsystem arranged adjacent to the first subsystem along a longitudinal axis of the monopile. Each of the first and the second subsystems includes a height adjustable support, and a pile support unit arranged on the height adjustable support such that the pile support unit is movable along the monopile's longitudinal axis. A method for displacing a horizontally oriented monopile for an off-shore wind turbine parallel to a base floor by use of the pile displacement system includes arranging the monopile onto the monopile support units of the first and second subsystems; lowering the height adjustable support of at least the first subsystem towards the base floor until the weight of the monopile is transferred from at least the first subsystem to an external support structure aligned along the monopile's longitudinal axis, adjacent to the first subsystem; moving the pile support unit of the first subsystem a distance in direction away from the external support structure; raising the height adjustable support of the first subsystem away from the base floor until the weight of the monopile is transferred from the external support structure to the first subsystem; and moving the pile support units of the first and the second subsystems a distance in direction towards the external support structure.

An equipment canister for supporting and enclosing electrical equipment of a wind turbine. The canister comprises: a housing defining or containing at least one internal platform for supporting the equipment; a lifting interface on a top of the housing; an at least one support formation positioned on or projecting laterally beyond a side wall of the housing. The support formation is capable of supporting the weight of the canister suspended therefrom when the canister is installed within a monopile wind turbine foundation. Various wind turbine arrangements and wind turbine assembly methods incorporating such a canister are also described.

A method for assembling a floating offshore wind farm, including: arranging at least N floating structures on a body of water; providing mast sections for assembling at least N masts; providing turbines and blades for at least N wind turbines; selecting at least one floating structure referred to as the mounting floating structure, the other floating structures being receiving floating structures; fastening a lifting device to the mounting floating structure; moving the mounting floating structure up to a receiving floating structure, and using the lifting device to lift and mount at least one constituent element of a wind turbine on the receiving floating structure; repeating the preceding step for the other receiving floating structures.

An apparatus is for performing parts of an operation to install a wind turbine, wherein the wind turbine has a tower, wherein the apparatus has a travelling car for travelling up and down along the tower for the wind turbine, and wherein the travelling car has a movable portion of a deck of the travelling car, wherein the movable portion of the deck is configured to carry an item to be installed as part of the wind turbine to a height for installation of the item and for moving the item substantially horizontally into a position for installation of the item when the travelling car is in a vertical position for installation of said item. Further is disclosed a method of installing at least a part of a wind turbine.

Provided is a tower section arrangement for a guyed tower of a wind turbine, the tower section arrangement including: a tower section including a wall having an outer surface with a circumference, at least two brackets attached to the outer surface of the wall at different locations on its circumference, and at least two stay cables, wherein each stay cable is connected at its first end to one of the brackets and is configured for connection at its second end to a cable foundation, and wherein an angle (?) between each stay cable and a tangent to the outer circumference at the respective bracket has, in a top view of the erected wind turbine, a value of 90? when the respective stay cable is guyed.