An operations and maintenance arrangement for floating wind turbines (1), comprising a floating sub-structure (2) on which at least one wind turbine unit (3) is situated, a service operation vessel (11) and a portable crane (14), said floating sub-structure (2) having an interface capable of receiving and fixedly locking said crane (14) to said sub-structure (2), said service operation vessel (11) having a ship crane (12) capable of lifting said portable crane (14) from said vessel (11) and onto said sub-structure (2). A method for replacing components using the arrangement is also described.

In an upend crane and an installation vessel including such an upend crane, the upend crane is provided with a boom configured for upending wind turbine components, e.g. monopiles and masts. The boom of the crane can be pivoted in an upend position for upending the wind turbine component with the bottom end of the wind turbine component being guided by a cart and a track along an upend deck and with the top end of the wind turbine component being guided along the boom by a trolley and the trolley guide.

A modular wind turbine assembly platform (WTAP) comprises a crane module and at least one work module for temporary storage of wind turbine components, and a modular floating hull assembly platform (FHAP) comprises a crane module and at least one work module for temporary storage of floating platform hull components and a large floating mat, wherein each of the modules comprises a rectangular hull and a plurality of retractable legs with each leg featuring a large-size footing in a water depth of 5 to 15 meters. A method for assembly of a floating offshore wind turbine comprises a floating wind assembly base (FWAB) including the modular FHAP and WTAP deployed at a near-shore site within a distance of 200 to 2000 meters from a shoreline. The method further comprises assembling a floating platform hull and lowering it into the water using the FHAP with the floating mat, then assembling and integrating a wind turbine with the floating platform hull using the WTAP.

A method and system for horizontally mating an offshore wind turbine generator assembly. typically including a tower and wind turbine nacelle and blades, with a substructure platform to form an integrated substructure unit, wet towing the unit to installation site offshore, and then installing the unit independent of cranes and derricks.

In the installation of a rotor blade in horizontal orientation to the hub of a horizontal axis offshore wind turbine, use is made of a blade motion synchronization and positioning device, which comprises a wind turbine coupler, a blade coupler, a motion arm between the wind turbine coupler and the blade coupler, and a controllable motion arm actuator assembly. The method includes bringing and maintaining the blade coupler in a motion compensated receiving position, wherein the arm is operated to compensate for sea state and/or wind induced tower top motion. In receiving position, the coupler is coupled to the blade that is suspended from a crane. The actuator assembly is then operated to gradually bring, and then maintain, the coupled blade in a horizontal motion that is synchronized with tower top motion, and to displace the coupled blade root into a pre-mounting position. Then a mounting motion is performed wherein the blade root is moved into a mounting position and the blade root is fastened to mounting structure by fasteners.

In the assembly of the support structure of a wind turbine, N sets of a first tubular brace and a second tubular brace extend from a tower support. For each set, the second braces are connected at one or both of their end parts by a casted connection. The first brace or the tower structure has a casting cavity for accommodating an end of the corresponding second brace. In order to assemble the construction, the second brace is inserted into the cavity, after which the end of the first brace is lifted until the end of the second brace is inserted deeply enough into the respective cavity.

Provided herein are methods and processes for wet-towing and installing a bucket foundation or mono-bucket for a wind turbine with or without the wind turbine mounted thereto in a body of water, such as a sea, an ocean or a lake. The methods and processes utilize at least a pair of wrap buoys secured to the bucket foundation or mono-bucket where the release thereof alters buoyancy such that the bucket foundation or mono-bucket submerges to a target site in the body of water.

A semi-submersible offshore platform includes at least one truss having a central column with an upper end and a lower end, at least one float having an upper end and a lower end, the float spaced from the central column horizontally, at least one upper beam coupled to the upper end of the float and the upper end of the central column, at least one lower beam coupled to the lower end of the float and the lower end of the central column, at least one cross beam coupled to the lower end of the float and the upper end of the central column, wherein each of the at least one upper beam, the at least one lower beam and the at least one cross beam are coupled via a plurality of pins to the float and the central column.

In order to allow for a safe and cost-efficient lifting of components (1) from a service vessel (2) to a location on an off-shore wind turbine generator (3) or lowering of components from a location on an off-shore wind turbine generator to a service vessel a method involving the use of a handshake-tool (10) is provided my means of which the component to be lifted or lowered can easily be transferred from one crane to another.

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.