Tohoku Electric Power Co. and France-based BW Ideol have received Approval in Principle (AiP) from Japanese classification society ClassNK for the design of a floating offshore wind turbine system, a step that moves a potential large-scale project off Kuji City, Iwate Prefecture, closer to reality.
The AiP, granted by Nippon Kaiji Kyokai (ClassNK), covers a concrete barge-type floating substructure engineered to host a 15 MW-class wind turbine. This preliminary approval confirms that the concept meets key technical and safety requirements at the design stage, allowing the partners to proceed with more detailed engineering and feasibility work.
The two companies have been jointly studying the commercial potential of a floating offshore wind project off Kuji since May 2022. The newly-approved system is tailored to the site’s specific metocean conditions and is built around BW Ideol’s patented Damping Pool® technology, which is designed to improve motion performance and stability in heavy seas.
The substructure is planned in concrete rather than steel, a choice the partners say is well suited to mass production and local fabrication. The mooring design combines synthetic fibre ropes with steel catenary chains in a hybrid system intended to balance durability, cost and ease of installation.
BW Ideol’s standardised 15 MW barge design had already passed a key international milestone in May 2025, when it received Basic Design Certification from DNV, demonstrating compliance with global offshore wind and maritime standards. ClassNK’s AiP now adds a Japanese stamp of technical confidence, reinforcing the design’s suitability for both domestic and international deployment.
On the back of the new approval, Tohoku Electric and BW Ideol plan to continue detailed feasibility studies off Kuji City, with the long-term aim of commercialising floating offshore wind in the region.
The partners say the project is intended to support Japan’s broader push to expand renewable energy and tap deeper coastal waters that are unsuitable for traditional fixed-bottom turbines.
