Disclosed embodiments relate to systems and methods for mating a wind turbine off-shore to a spar buoy without the use of a crane barge. The system may include a spar buoy, wherein the spar buoy is secured to a foundation, and a wind turbine to be installed on the spar buoy. The system may also include a first truss affixed to the top of the spar buoy and a second truss affixed to the bottom of the wind turbine. The first truss may comprise either stabbings or receptacles configured for mating to the second truss and the second truss may comprise either receptacles or stabbings configured for mating to the first truss.

A system comprises a carrier structure configured for carrying a module and a floating support structure configured for supporting the carrier structure. The carrier structure comprises first connection means and the floating support structure comprises second connection means, whereby the first and second connection means are configured for releasable connection and comprise contact surfaces that prevent the carrier structure from rotating about its longitudinal axis when the two structures are connected. A transportation and installation apparatus for the carrier structure is configured for being arranged on a floating vessel.

A system comprises a carrier structure configured for carrying a module and a floating support structure configured for supporting the carrier structure. The carrier structure comprises first connection means and the floating support structure comprises second connection means, whereby the first and second connection means are configured for releasable connection and comprise contact surfaces that prevent the carrier structure from rotating about its longitudinal axis when the two structures are connected. A transportation and installation apparatus for the carrier structure is configured for being arranged on a floating vessel.

Methods for the maintenance of a marine structure having a wind turbine and at least one essentially vertical shaft are described. The methods include the use of an auxiliary floating system having: at least one floating element that remains semisubmerged throughout the process of maintaining the marine structure; at least one coupling structure that connects the system to the floating structure; and contact elements and tightening elements, wherein the contact and tightening elements are secured to the coupling structure and are intended to solidly connect the system to the shaft. Advantageously, this solid connection allows operations for the maintenance of the marine structure to be carried out in a manner that is efficient and safe for maintenance workers and for the systems involved in the operations.

Provided is a floating wind turbine including a hull, a wind turbine mounted on top of the hull and a counterweight suspended below the hull by a counterweight suspension is described. Also, a method for the installation is described. The counterweight includes one or more counterweight buoyancy tanks. When the internal volume of the buoyancy tanks is filled with air, the total buoyancy of the counterweight is close to or greater than its weight. Hereby it is capable of floating in a towing/maintenance position with moderate or no support in the vertical direction from the hull or other vessels. During towing, the hull substantially has the character of a barge, substantially relying on a large waterplane area and shallow draft to maintain stability.

The invention relates to an operations vessel for the maintenance, installation and/or disassembly of offshore structures, comprising: a hull equipped with ballast means connected to a control system; at least one working platform supported on the hull by means of one or more support elements; and at least one system for coupling to an offshore structure, wherein said coupling system can adopt, at least, a state in which it is coupled to said offshore structure and a state in which it is not coupled to said offshore structure. Advantageously, the control system and the coupling system are configured in a cooperating manner, in order to adopt at least two working positions of the vessel, wherein the hull adopts an above-water state with the coupling system decoupled, and at least a second working position wherein the hull adopts a submerged state in which the coupling system is coupled to the offshore structure.

A method of assembling a floating wind turbine platform includes forming a base assembly of the floating wind turbine platform in either a cofferdam or a graving dock built in water having a first depth. The base assembly includes a keystone and a plurality of buoyant bottom beams extending radially outward of the keystone, wherein longitudinal axes of each of the plurality of bottom beams are coplanar. The cofferdam or the graving dock is flooded and the assembled base assembly is floated to an assembly area in water having a second depth. A center column and a plurality of outer columns are assembled or formed on the base assembly, a tower is assembled or formed on the center column, and a wind turbine is assembled on the tower, thereby defining the floating wind turbine platform.

A method of assembling a floating wind turbine platform includes forming a base assembly of the floating wind turbine platform in either a cofferdam or a graving dock built in water having a first depth. The base assembly includes a keystone and a plurality of buoyant bottom beams extending radially outward of the keystone, wherein longitudinal axes of each of the plurality of bottom beams are coplanar. The cofferdam or the graving dock is flooded and the assembled base assembly is floated to an assembly area in water having a second depth. A center column and a plurality of outer columns are assembled or formed on the base assembly, a tower is assembled or formed on the center column, and a wind turbine is assembled on the tower, thereby defining the floating wind turbine platform.

A control system for stabilizing a floating wind turbine is connected to at least one sensor and at least one actuator of the floating wind turbine and configured for: determining a difference between the floater orientation and a predefined desired floater orientation of the floating wind turbine during towing of the floating wind turbine, actuating the at least one actuator during towing of the floating wind turbine for changing the floater orientation of the wind turbine to minimize the difference.

A control system for stabilizing a floating wind turbine is connected to at least one sensor and at least one actuator of the floating wind turbine and configured for: determining a difference between the floater orientation and a predefined desired floater orientation of the floating wind turbine during towing of the floating wind turbine, actuating the at least one actuator during towing of the floating wind turbine for changing the floater orientation of the wind turbine to minimize the difference.