Floating wind concept wins DNV approval

Classification firm DNV has awarded Approval in Principle to Inocean, a Norwegian subsidiary of the engineering firm Technip Energies, for a semi-submersible wind turbine platform concept.

A result of the project WINDMOOR, a competence building project funded by the Research Council of Norway through the ENERGIX programme and industry partners Equinor, MacGregor, Inocean, APL Norway and RWE Renewables, the INO12TM has been designed to accommodate a 12MW wind turbine that can last for 25 years without dry docking.

The concept has been tailored towards mass production and scalability, and also offers the possibility of full assembly at the quayside with direct access to the tower.

The aim of the project was to improve the understanding of loads governing the mooring system design of floating wind turbines, and the scope involved validating low-frequency hydrodynamic models, understanding atmospheric stability and aerodynamic interaction between turbines.

The steel platform has three columns connected by pontoons and deck beams, and the turbione tower is installed at the top of one of the columns.

“The design was based on an iterative approach with multiple combinations of draft, column diameter/height, pontoon width/height, and columns center-center distance, subjected to constraints on hydrostatics, required ballast, heave/pitch natural periods, and static pitch at rated condition,” says research and development group SINTEF Ocean in its 80-page Definition of the INO WINDMOOR 12 MW base case floating wind turbine report.

The design has been assessed for operations in Bretagne Sud (South Brittany), based on the DNV class notation: OI Column-stabilised Floating offshore wind turbine installation POSMOOR in the DNV Rules for Offshore Units DNV-RU-OU-0512, “Floating offshore wind turbine installations”. The review conducted covers the hull structure, stability, mooring, marine systems, and technical safety.

The AiP, which independently confirms that a design is feasible, was signed between Inocean and DNV at the recent Nor-Shipping trade show in Oslo.