An offshore wind turbine including a tower, a transition piece and a lifting apparatus for operating a lift inside the wind turbine is provided. The tower includes an inner platform at the bottom end of the tower. The transition piece includes a hang-off platform. The lifting apparatus includes a plurality of wires, a plurality of tensioners, one or more brackets attached to the inner platform and movable between at least a first operative configuration in which the plurality of tensioners are attached to the one or more brackets and the lift is movable from the first station at the inner platform towards the upper end of the tower, a second retracted configuration in which one or more brackets allows the lift to move between the first and the second station, the plurality of tensioners being attached to the hang-off platform.

Methods and systems for operating a stable platform in a far-offshore deep-sea environment. The platform can advantageously be a wind power generation station. A structural framework carries (for example) the wind turbine in an elevated position. Multiple points on the floating structure are connected both to a surface float and to a deep mass (e.g. an enclosed volume of seawater).

Embodiments herein describe operating wind turbines in an offshore park to provide auxiliary power to a local AC grid or to an onshore grid during a grid malfunction. In one embodiment, the offshore park is coupled via a HVDC link to an onshore grid. When the HVDC link is down, a substation in the park includes a backup generator for creating a weak grid for powering auxiliary systems in a pilot turbine. The wind turbines in the park can switch to an auxiliary control system help power the auxiliary systems in the substation and in other turbines. In another embodiment, the offshore park is AC coupled to an onshore grid using a transformer in the substation. The wind turbines can participate in a brown or black start following a grid fault by switching to operating using the auxiliary control system.

A system that produces electricity offshore through a fixed installation, including a minimum of; one turbine, one generator, one compressor set, one high voltage subsea cable, and one control center; the generator is a gas driven generator that produces enough power to operate the electric motors, an onshore control center that operate and monitor the system, and all electricity generated through the water turbines and generators are transported to the onshore electricity grid through a high voltage subsea cable.

A hollow structural element of a wind energy plant, in particular an offshore wind energy plant which includes a hollow structural element, and a cable arrangement extending along the hollow structural element. A shading element is arranged on the hollow structural element at a distance from the cable arrangement.

The present disclosure belongs to the technical field of new energy utilization, and provides an offshore oscillating water column wave energy conversion device with an external permeable structure. The offshore oscillating water column wave energy conversion device with the external permeable structure comprises an oscillating water column system, an anchoring fixing system and a permeable structure. According to the offshore oscillating water column wave energy conversion device with the external permeable structure provided by the present disclosure, the offshore oscillating water column wave energy conversion device and the permeable structure are effectively combined. Using an offshore floating structure, the offshore oscillating water column wave energy conversion device with the external permeable structure can be applied to deep and far sea areas with higher wave energy density, and the output power of the device can be effectively improved.

A deployed L-shaped rack structure interengaged with a self-elevating vessel is used for supporting a feeder transport vessel, such as an ocean or sea barge, to eliminate relative motion or movement between the vessels. Some of the proposed rack structures are movable between a stowed position and a deployed position. The method of use for the movable rack structures includes the self-elevating vessel arriving at a predetermined location, elevating the hull of the self-elevating to a suitable height above the sea surface at a desired still water line (SWL) to create an air gap, and then deploying the rack structure. A feeder transport vessel, with its cargo and/or components, can then be floated over the deployed rack structure. The self-elevating vessel then uses its jacking system including a plurality of legs supported on the seabed to raise the feeder transport vessel and its cargo and/or components to a desired height above the SWL. From this position relative motion between the self-elevating vessel and transport vessel is eliminated so that the self-elevating vessel lifting device, such as a crane, can be more safely used to install energy components, such as wind turbine components. A bottom supported tower/column section could also be assembled and installed in seabed using the self-elevating vessel and rack structure along with the lifting device. A fixed rack structure system and its method can also be advantageously used with a self-elevating vessel. The systems and methods could be used in reversing the method or steps for deinstallation of the energy components installed in the sea.

Described is a device for providing a sizeable, slender object having a longitudinal direction into an underwater bottom from a deck of a vessel. The device includes a lifting means configured to take up the object at a lifting point thereof and position it on the underwater bottom; an upending tool connected to an edge of the vessel and configured to engage a first circumferential part of the object suspended from the lifting means and provide a pivot around which the object can be upended; and a gripping tool connected to an edge of the vessel and configured to engage a second circumferential part of the object suspended from the lifting means, whereby the first and second circumferential parts are optionally spaced apart in the longitudinal direction of the object. The gripping tool includes an actuator system configured to act on at least one of the upending tool and the gripping tool and control movements of at least one of the first and the second circumferential parts, relative to the vessel. A method using the device is also described.

Disclosed is a semi-submersible floater defining an operating state and a non-operating state, and including at least two outer columns, a central column for receiving a payload, and, for each outer column, a branch in the form of pontoon connecting the outer column to the central column and defining a branch axis oriented from the central column towards the outer column. Each branch is formed from a first portion and a second portion which extend successively along the corresponding branch axis, each one over at least 10% of the total extent of the branch, along the branch axis. In the operating state of the floater, the second portion of each branch is at least partially filled with a ballast material, and the first portion does not contain any ballast material.

The invention relates to a method of manufacturing a tower (2) for an offshore wind turbine as well as such a tower. The method comprises providing the tower, mounting a crane (5) to an outer surface of the tower, and transporting the tower to the installation site of the wind turbine after the mounting of the crane. The crane comprises a base part (6) fixedly mounted to the tower, and a crane arm (7) pivotally connected to the base part at a first end (8). The method may further comprise a step of testing and certifying the crane according to a predetermined standard before the step of transporting the tower to the installation site. By application of the invention, the amount of installation work to be performed at the installation site can be minimized. In some embodiments of the invention, the crane arm has a shape matching the outer surface of the tower.