Introduction: Why Floating Offshore Wind Now?
Offshore wind power is a key technology for expanding renewable energy in Japan. In particular, Floating Offshore Wind Turbines (FOWT) are attracting attention as the optimal solution for Japan’s deep coastal waters.
For more background on why floating wind is gaining traction in Japan, see:
➡️ Part1: Why Now? Floating Offshore Wind
In this article, we explain systematically for renewable energy beginners:
- The basic structure of floating offshore wind (floating platform, RNA, mooring system)
- The overall design and certification process unique to floating wind
- Legal and regulatory frameworks involved
1. What is Floating Offshore Wind? Structure and Basics
Floating Offshore Wind (FOWT) is a technology that generates electricity by floating wind turbines in sea areas deeper than 50 meters.
Unlike bottom-fixed turbines installed via seabed foundations, floating platforms support turbines at sea surface level, anchored to the seabed using mooring lines and anchors.
This enables power generation even in deep sea areas. Japan’s rapidly deepening coastal waters make floating technology especially suitable.
For detailed explanations of floating platform types and designs, refer to:
➡️ Part2: Floating Platform Design: Key Types Explained
2. Three Key Components of Floating Offshore Wind
Floating wind systems consist of three main elements:
2-1. Floating Platform
- Supports the tower and wind turbine (RNA)
- Includes semi-submersible, spar buoy, and TLP structures
- Stability (restoring force) is critical for maintaining upright position
- Structural design must address strength, fatigue, corrosion, etc.
2-2. RNA (Rotor Nacelle Assembly)
- Comprises rotor blades and nacelle (generator, gearbox, etc.)
- Often adapted from onshore or fixed-bottom wind turbines
- Typically uses certified turbine types
2-3. Mooring System
- Keeps the floating platform anchored in position
- Includes anchors, mooring lines (chains, ropes), and buoy components
- Spread mooring or TLP systems selected based on seabed and depth
These three systems work together as a single floating wind power plant.
3. Design and Certification Process Unique to Floating Wind
Designing floating wind systems requires considering not only the turbine but also the floating platform and mooring system as an integrated whole.
3-1. Overall Design Approach
- Define site-specific environmental conditions (wind, waves, currents)
- Conduct dynamic analyses considering interactions between platform, RNA, and moorings
- Perform load analysis and structural design based on DLC (Design Load Cases)
- Ensure long-term durability against corrosion, wear, and fatigue
- Evaluate special conditions like marine growth and tsunamis
For economic considerations and LCOE evaluation, see:
➡️ Part3: Floating Wind Cost Structure & LCOE
3-2. Certification and Regulatory Framework
| Category | Description |
|---|---|
| Type Certification | Evaluates RNA (turbine) structural safety |
| Prototype Certification | For demonstration units with limited deployment |
| Wind Farm Certification | Assesses safety and performance of entire plant |
| Class Inspections | Ensures safety as floating structure (NKRE-GL-FOWT01) |
| Domestic Regulations | Compliance with MLIT guidelines, Electricity Business Act, Port Law, etc. |
For challenges in Japan’s certification and regulatory environment, refer to:
➡️ Part4: Japan’s Regulatory Framework & Certification Challenges
3. Key Design Points for Introducing Floating Wind
- Ensure platform stability (restoring force, draft, durability)
- Design mooring systems for long-term durability (corrosion and wear prevention)
- Address turbine control impacts due to platform motions
- Improve inspectability and maintainability (access systems, mooring inspections)
- Comply with domestic Japanese regulations, considering earthquakes and tsunamis
For actual demonstration projects, refer to:
➡️ Part5: Case Studies: From Demonstration to Commercialization
For future trends and technology outlook, see:
➡️ Part6: Post-2030 Floating Wind Trends & Outlook
Conclusion: Grasping the Full Picture of Floating Wind
Floating offshore wind is not just a turbine at sea — it is a system integrating floating platform, RNA, and mooring system.
To optimize system design:
- Understand the roles and interactions of each component
- Define appropriate environmental and design load conditions
- Comply with certification processes and regulations
Floating wind is poised to play a key role in Japan’s energy transition.
For a broader look at offshore wind technologies and future innovations, make sure to explore our comprehensive summary article:
🌊 Offshore Wind Technology 2025: Foundations, Floating Wind, Turbines, and Innovations
Explore more categories at DeepWind:
- 🔍Market Insights – Understand the latest trends and key topics in Japan’s offshore wind market
- 🏛️Policy & Regulations – Explore Japan’s legal frameworks, auction systems, and designated promotion zones.
- 🌊Projects – Get an overview of offshore wind projects across Japan’s coastal regions.
- 🛠️Technology & Innovation – Discover the latest technologies and innovations shaping Japan’s offshore wind sector.
- 💡Cost Analysis – Dive into Japan-specific LCOE insights and offshore wind cost structures.
