Seajacks International recently completed the installation of all 33 wind turbines at the Akita and Noshiro offshore wind farm situated off Japan’s Akita Prefecture coastline – a major step forward for the country’s renewable energy market.

Zaratan Akita May 2021

The wholly owned subsidiary of Eneti mobilised the self-propelled jack up vessel, Seajacks Zaratan, to execute the installations, in collaboration with main installation contractor Kajima and turbine supplier Vestas Japan.

The 140 MW project, owned by Akita Offshore Wind (AOW), is the first commercial-scale fixed-bottom wind farm to be constructed in Japan.

Blair Ainslie, Seajacks ceo said: “The completion of the turbine installation at Akita and Noshiro is an achievement that all parties involved can be proud of. The project is a powerful demonstration of a successful collaboration between international partners to deliver a successful project outcome.”

Seajacks Zaratan will continue to provide support on the project through the end of the charter period, before demobilising and heading onto further turbine installation projects in the Asia Pacific region.

During construction, transport engineering specialist Mammoet was called in to upend 33 monopiles from the deck of the installation vessel. It said that this was the first time self-propelled modular transporters (SPMT) had been used for this type of operation in Japan.

The operation took place about 1 km offshore between the ports of Akita and Noshiro, with main marshalling station in Akita. The monopiles needed to be upended one by one from their horizontal orientation on the deck. In particular, close monitoring of tolerances was required to ensure the SPMTs were not subjected to high levels of torsional load.

The monopiles were loaded by a crane into a cradle and the upending frame. SPMTs were connected to the upending frame and the crane hook to their other end. Then, the SPMTs were driven forward as the crane hoisted.

As each monopile was larger than the deck of the vessel, there was a need for the upending operation to stop and have the crane slew 180 degrees. Mammoet explained that an unusual steering technique allowed the trailers to be put into carousel mode; freewheeling to follow the motion of the crane. “This required some bespoke power pack design due to the limited available space on the jack-up vessel deck,” said Francisco Rodrigues, global segment lead for offshore wind for Mammoet.

Mammoet is hopeful of further business on the Akita Noshiro project and others beyond the monopile placement. “We do have ongoing discussions with local partners for future works,” said Rodrigues. “We are developing studies for multiple engineering, procurement, and construction companies in their wind developments. We are [also] assessing port infrastructures across the country and assisting local companies to develop their construction strategy for future tenders.”

Further information on this project, and on the development of the Japanese energy industry, can be found in our September/October 2022 edition.

Energy security has always been an important issue in Japan, with recent geological, meteorological, and geopolitical events bringing matters to even greater urgency.

Just this year Tokyo indicated that it would restart as many as four nuclear reactors, in addition to the five already operating. If such plans are completed, nuclear power would account for about 10 percent of the nation’s electricity. That would be well below the peak of 25 percent the year before Fukushima, and well above the 1 percent four years after the disaster.

Beyond the resurgence in nuclear power, almost a dozen thermal power plants are being considered for reactivation, expansion, or construction, including the possibility of a new coal-fired generator.