DEME and Penta-Ocean to Deploy Japan’s First 15 MW Offshore Wind Turbines, Strengthening Domestic Installation Capacity

2026/06/03

SEP installation vessel Sea Challenger. Photo: DEME

DEME and Penta-Ocean Advance Japan’s First 15 MW-Class Offshore Wind Deployment

The Oga–Katagami–Akita Offshore Wind Project off the coast of Akita Prefecture is emerging as a key milestone in the evolution of Japan’s offshore wind industry. Japan Offshore Marine (JOM), a joint venture between Belgium-based offshore engineering specialist DEME and Penta-Ocean Construction, has secured a contract to carry out offshore wind turbine installation works for Oga Katagami Akita Offshore Green Energy LLC. Offshore construction is scheduled to begin in the second half of 2027, with commercial operations targeted for June 2028.

The project will have a total installed capacity of 315 MW and will feature 21 Vestas V236-15.0 MW wind turbines. This marks the first deployment of 15 MW-class offshore wind turbines in Japan and one of the first applications of this turbine size outside Europe, excluding China. The project highlights Japan’s gradual transition toward next-generation turbine technology as global offshore wind development continues to favor larger and more efficient turbine platforms.

Sea Challenger to Strengthen Japan’s Offshore Installation Capability

At the center of the installation campaign is the self-elevating platform (SEP) vessel Sea Challenger. Originally owned by DEME, the vessel is now being operated under JOM and has recently undergone a major upgrade program to support the installation of 15 MW-class turbines.

The modernization included increasing crane lifting capacity from 900 tonnes to 1,600 tonnes, widening the vessel’s hull, and extending its legs. These upgrades position the vessel to meet the technical requirements of the latest generation of offshore wind turbines.

The vessel is expected to be reflagged under the Japanese registry during fiscal year 2026 and will become one of the first large-scale turbine installation vessels operating under the Japanese flag. Beyond supporting a single project, the move is widely viewed as an important step toward strengthening Japan’s domestic offshore wind construction infrastructure.

Addressing One of Japan’s Key Offshore Wind Bottlenecks

A shortage of specialized installation vessels has long been considered one of the major challenges facing Japan’s offshore wind sector. As turbine sizes continue to increase, access to large jack-up installation vessels has become increasingly critical, forcing many projects to rely on overseas fleets.

Penta-Ocean Construction already participates in the operation of the 1,600-tonne crane SEP vessel CP-16001 together with KAJIMA CORPORATION and YORIGAMI MARITIME CONSTRUCTION. The vessel is scheduled to support foundation construction works for the Oga–Katagami–Akita project.

With both CP-16001 and Sea Challenger available for operations, Japan will have enhanced capacity to execute multiple offshore wind projects simultaneously. As the Japanese government accelerates offshore wind deployment toward its long-term decarbonization goals, expanding domestic installation capabilities is becoming increasingly important for maintaining project schedules and reducing supply chain risks.

DEME Deepens Its Commitment to the Japanese Market

The contract also represents a significant milestone for DEME’s long-term strategy in Japan.

Based in Tokyo, JOM combines DEME’s extensive offshore wind installation experience in Europe with Penta-Ocean’s local marine construction expertise and project execution capabilities. The partnership was established to develop a dedicated offshore wind installation platform tailored to the needs of the Japanese market.

While DEME has participated in numerous offshore wind projects across Europe, Japan presents unique regulatory, logistical, and environmental conditions. The successful award of the Oga–Katagami–Akita contract demonstrates that JOM has moved beyond its establishment phase and is now positioned to participate in larger-scale offshore wind developments throughout the country.

The company’s efforts to localize vessel operations, develop Japanese offshore expertise, and establish a long-term operational presence reflect a broader commitment to supporting the growth of Japan’s renewable energy sector.

A Symbolic Project for the Next Stage of Japan’s Offshore Wind Industry

Japan’s offshore wind market has recently faced headwinds, including rising construction costs, supply chain disruptions, and increasing pressure on project economics. Nevertheless, the Oga–Katagami–Akita project stands out as a symbolic development that combines next-generation turbine technology with enhanced domestic installation capacity.

The competitiveness of offshore wind is determined not only by turbine technology but also by the strength of the supporting industrial ecosystem, including installation vessels, port infrastructure, logistics networks, and skilled personnel.

Against this backdrop, JOM’s contract award and the Japanese reflagging of *Sea Challenger* represent more than a single project milestone. They signal a broader shift in Japan’s offshore wind sector—from a market focused primarily on project deployment toward one increasingly focused on building a sustainable domestic offshore wind industry.

Resource:DredgeWire, DEME, Penta-ocean construction, WindTAIWAN