Obayashi Corporation Obtains World's First Basic Design Approval for Hybrid TLP Floating Offshore Wind Facility

Obayashi Corporation has obtained Approval in Principle (AiP) from ClassNK for the supporting structure of a Tension Leg Platform (TLP) type floating offshore wind power facility, which utilizes a hybrid structure of steel and concrete. This approval confirms that the safety and structural integrity of the TLP floating offshore wind facility design meet the requirements of ClassNK guidelines. It is the world's first instance of ClassNK issuing an AiP for a TLP floating offshore wind foundation adopting a hybrid steel-concrete structure.

This development was conducted as part of the project "Development of Next-Generation Technologies for Promoting the Introduction of Floating Offshore Wind Power" commissioned by NEDO (New Energy and Industrial Technology Development Organization).

Obayashi has been researching TLP floating offshore wind power since 2012, utilizing tank tests, numerical analysis, and sea-area demonstration tests to verify structural safety and motion characteristics. Building on previous experience, including an AiP received in 2018 for a concrete-only TLP floating structure, the company has now adopted a hybrid structural design for the first time.

Key features of the support structure include:

1. Cost-effective floating foundation
By utilizing a hybrid structure, steel and concrete components can be manufactured separately and connected at a site assembly yard. This increases construction method options and is estimated to reduce construction costs by 25% compared to other types (such as steel semi-submersibles). It also facilitates easier mass production.

2. Stable power generation performance
The TLP mooring system maintains constant tension, suppressing vertical movement of the float. This is estimated to improve power generation efficiency by approximately 8% compared to semi-submersible forms.

3. Minimized impact on fishing activities
Compared to catenary mooring, which requires a large occupation width (approximately 10 times the water depth), the TLP mooring system requires less space, making it easier to minimize the occupied maritime area and reduce impact on fishing activities.

With this AiP, the foundation for commercial design is set. Obayashi aims to conduct sea trials with a wind turbine mounted in 2028 under the NEDO project, contributing to early social implementation and the 2050 carbon neutrality goal.