Japan
Appointed as Owner’s Engineer, Arup has supported the first bottom-fixed offshore wind project in Japan’s general sea areas to obtain conformity certification through the public auction process.
It is the world’s first design for a 15MW-class turbine to account for earthquake effects.
Arup has supported the certification process for the offshore wind power project located off the coast of Oga City, Katagami City and Akita City in Akita Prefecture, Japan.
On 30 June 2026, the project developer obtained certification from Bureau Veritas Japan Co. The certification confirms that the design of the offshore wind power facilities complies with Japanese technical standards and regulatory requirements, marking a key milestone toward approval of the construction plan under the Electricity Business Act.
The project involves key stakeholders, including Kajima Corporation (partnering with Kobori Research Complex Inc./COWI A/S), responsible for monopile foundation design, and Vestas Japan Co., Ltd. and MHI Vestas Japan Co., Ltd., responsible for wind turbine and tower design. The certification was achieved through close collaboration among all parties, encompassing site condition assessment, development of design criteria, global load analysis, and design verification of both support structures and wind turbines.
The project marks several significant firsts. It is the first bottom-fixed offshore wind project in Japan’s general sea areas to obtain conformity certification through the public auction process, and the first certified offshore wind project in the country featuring turbines exceeding 10MW in capacity.
The project also incorporates design considerations specific to Japan’s natural conditions, including seismic factors — notably representing the world’s first design case for a 15MW-class offshore wind turbine to explicitly account for earthquake effects.
This certification is a landmark moment for Japan’s offshore wind sector. By combining our global expertise with deep understanding of Japan’s unique seismic conditions, we helped the project team navigate complex technical and regulatory requirements as the country accelerates its energy transition.
With certification now secured, the project marks an important precedent for the application of advanced seismic design in large-scale offshore wind development.
Arup remains committed to supporting the continued growth of Japan’s offshore wind market.
