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Akita offshore wind moves from vessel booking to certified installation readiness
The 315 MW Oga-Katagami-Akita project has advanced beyond a specialist vessel signal: Japanese technical and port-standard compliance is now confirmed, while base-port preparation, monopile engineering, submarine cables, navigation safety, and Sea Challenger turbine installation form one live marine delivery chain.
What changed
The developer's official project page defines 21 Vestas V236-15MW turbines, a 30 June 2028 commercial-operation target, and a construction chain covering base-port use, foundations, submarine cables, turbine installation, and commissioning. Its 1 July 2026 update confirms completion of conformity assessment against Japanese technical standards and Ports and Harbours Act compliance, with Kajima, COWI, Vestas, and Arup named in the design and certification chain. Penta-Ocean and DEME separately confirm the 1,600-tonne-lift Sea Challenger charter and Japan Offshore Marine engineering role for turbine installation.
Why it matters
Japan's fixed-bottom offshore buildout depends on a tightly coupled domestic and international marine chain. Certification and a specialist vessel charter reduce readiness uncertainty, but base-port throughput, foundation and cable sequence, weather and navigation controls, installation cadence, integrated testing, and grid handover still determine whether the June 2028 operating target is credible.
Decision read
What remains open
Specialist vessel availability is no longer the main uncertainty. The June 2028 target now depends on certification, base-port throughput, monopile design, cable sequencing, navigation controls and the interface between domestic contractors and international offshore capability.
Next watchpoints
- Base-port readiness and major-component arrival sequence
- Monopile installation and cable-laying mobilisation
- Sea Challenger arrival and turbine installation window
- Navigation Safety Committee controls during offshore works
- Schedule movement against the 30 June 2028 commercial-operation date
Knowledge context
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Sources used 4
- Oga-Katagami-Akita project overview and construction schedule Oga Katagami Akita Offshore Green Energy LLC, Publication date not stated; evidence reviewed 13 July 2026
- Conformity assessment against Japanese technical standards completed Oga Katagami Akita Offshore Green Energy LLC, 1 July 2026
- Signing of charter contract for offshore installation vessel Penta-Ocean Construction, 29 May 2026
- DEME wins contract for offshore wind project in Japan DEME Group, 29 May 2026
Corrections and methodology
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