Kitakyushu Hibikinada offshore wind, Japan

Nurturing green expertise

Japan’s Kitakyushu Hibikinada offshore wind project is potentially a game changer for the country’s renewable energy industry.

The largest offshore arrays built to date have been of 143MW installed capacity at Akita Noshiro and 112MW at Ishikari Port, in the north west. Both drew heavily on European expertise, designs, technology and supply chains.

With 220MW installed capacity, Hibikinada, just off the south west coast, will be bigger. The project is being led by reputable Japanese electricity utility providers, financed and built wholly by Japanese companies, using locally adapted designs.

It will establish the core capabilities needed to grow a domestic offshore renewables industry that can meet demand for green energy in Japan and, it is hoped, neighbouring countries.

Whereas Europe has grown a large and mature offshore renewables industry, Japan’s is just starting out.

Osamu Ohta

Country lead, Mott MacDonald Japan

Previous offshore wind projects have been developed by international energy developers. Hibikinada is different. The consortium of Japanese companies developing the project, Hibiki Wind Energy, has placed and trained key personnel on European projects, learning from advisors including Mott MacDonald and equipping them to progress this major project at home.

The 220MW Hibikinada wind scheme will be sited just off the south west coast of Japan

Risk management

Hibiki Wind Energy appointed Mott MacDonald in 2021 as lenders’ technical advisor to review, assess and advise on exposure to potential construction and operation risks.

“Among the lenders there are three leading banks with significant offshore wind energy experience that has been mainly on European projects,” says Osamu Ohta, country lead for Mott MacDonald Japan.

“Japanese offshore wind projects present location-specific differences, including earthquakes and typhoons. Whereas Europe has grown a large and mature offshore renewables industry, Japan’s is just starting out. And Hibikinada is employing construction techniques that are uncommon outside Japan.”

Osamu notes that unlocking capital to initiate the project has involved generating unusually detailed information to account for these location-specific challenges.

“We’ve helped bridge the cultural gap, so that all sides – client, contractors and lenders – have the information they require in language that’s easy to comprehend. Lenders need help understanding the engineering and vice versa. We’ve helped translate different needs and perspectives.”

We oversaw unusually detailed studies of the complex seabed geology, as well as meteorological, oceanographic and environmental conditions. The project is in one of Japan’s less seismically active areas, but site investigations still needed to be particularly rigorous.

Withstanding waves, winds and quakes

Meanwhile, ‘super typhoon’ winds blow at over 200km an hour. The lateral forces and cyclical loading from waves and gusts will be extreme, albeit within the design parameters for severe weather applied to projects in other parts of the world.

Earthquakes add complication, however. Tremors frequently cause loss of friction and bearing capacity between soil particles, and solid ground temporarily takes on the properties of a liquid. When soil liquifaction occurs, structures can literally sink.

The jacket foundation design has therefore been scrutinised to ensure that it can withstand any imaginable combination of earthquake plus typhoon conditions.

A combination of locally proven piled foundation designs are being deployed, depending on the ground conditions and depth to bedrock.

Scrutinising the supply chain

Supply chain capacity came under scrutiny to gauge and mitigate risk of project delays.

The contractor for the foundations and turbine installation, a joint venture between Penta-Ocean and Nippon Steel Engineering, procured a new self-elevating platform for the project. Essentially a giant ship complete with crane and worker accommodation, which can raise itself clear of the sea on legs, it allows for continuous construction in all but the most severe typhoon conditions.

This self-elevating platform, which is substantially larger than any other in the region, is working in tandem with other offshore working vessels.

We investigated and confirmed that Japanese cable and substation manufacturers could meet demand for transmission infrastructure. The contract for cables and substation supply and installation was awarded to J-Power Hytech.

We also checked that the right skills, equipment and capacity existed locally to meet long term operational and maintenance needs, leading to the appointment of Penta-Ocean.

Fast track programme

Pile installation work started in November 2023, due for completion by the end of 2024. Cable laying will take slightly more than a year, from July 2024 to September 2025.

Turbines will be installed and commissioned in the second and third quarters of 2025, with substation construction completing and the first electricity flowing in March 2026.

Spinning giants

The Hibikinada array will consist of 25 Vestas 9.6MW turbines, set out in an area measuring 11km from east to west and up to 10km north to south. The turbines are among the largest commercially currently proven designs, and they are huge.

Each three bladed rotor has a diameter of 174m, dwarfing the 60m Ferris wheel in nearby Cha-cha Town Kokura theme park, and even the 150m Singapore Flyer. At the highest point of rotation, the rotor blades will be 200m above sea level.

All this fast turning, wind buffeted mass is supported on a 110m tall steel tower, mounted on a four legged steel lattice structure called a jacket. Each jacket is firmly anchored to the seabed by piles.

The turbines will rise 200m above the surface of the sea, with rotors 174m wide (Credit: Hibiki Wind Energy)

Going large

As the global offshore wind energy market has grown, project size has become ever more important.

The world’s main turbine, cable and substation manufacturers prioritise supply to projects of 1GW or more. Smaller projects increasingly struggle to place orders. When they can, the cost per unit tends to be higher, as suppliers are unable to generate efficiencies of scale.

Hibikinada has already expanded and diversified Japan’s supply chain. As the project builds experience, the country will be better equipped to realise its offshore wind energy potential – which the Global Wind Energy Council estimates at nearly 2TW.

The methodology of project management carried out and continuing at Hibikinada demonstrates the high skill and capability of the project developer and could be a model for other offshore wind projects in Japan. It shows how to unlock private capital and get projects moving.

World leading expertise

Mott MacDonald was technical advisor on the two previous largest Japanese offshore wind firms, Akita Noshiro and Ishikari projects.

For two decades we have been one of the world’s top technical advisors for renewable energy projects, by number and value.