Joint industry project

Floating wind reliability - Planned extension to include tower and substructure

The Floating Wind Reliability joint industry project (JIP) launched in 2023 to define cost-efficient, consistent design requirements for mooring and inter-array cables without compromising safety. In Phase 2, the work will extend to tower and substructure design, building on Phase 1 insights. We will also supplement Phase 1 by covering mooring and cable concepts not yet included, but intended to be captured by the requirements.

Phase 1 indicates potential savings of ~EUR 17.5 million in supply and installation for a 40-turbine floating wind farm with chain-polyester-chain moorings. Phase 2 aims to unlock further savings by tailoring requirements for the tower and substructure. 

Challenge

A major challenge in floating wind design is the structural design of the tower and substructure. Current standards lack up-to-date design format and calibrated safety factors for these structures, presenting an opportunity for cost savings. Phase 2 therefore aims to perform this calibration based on the safety level recommended in Phase 1.

Additionally, the required extent of design analysis needs to be updated. Existing requirements - such as those in DNV-ST-0119 -  inherit the Design Load Case (DLC) matrix from bottom fixed and land based turbines, resulting in an unnecessarily broad analysis scope that does not distinguish which parts of the matrix are important for different parts of the structure or different phases of the project. This challenge is amplified for large volume floaters, which demand complex models and significant computational effort to achieve adequate accuracy in fatigue and ultimate strength assessments.

Furthermore, the Load and Resistance Factor Design (LRFD) format is not well suited for time domain analysis, as its separate safety factors for different load effects complicate practical application. Industry feedback indicates a clear need for more targeted and less onerous requirements.

Objective

Phase 2 aims to improve and align industry practice for global structure design (tower and substructure), while extending the validity range for floating wind mooring and inter array cable design. The ambition is cost efficient, consistent requirements without reducing safety.   

Scope

The Phase 2 scope below is indicative and will be refined with Phase 1 participants based on input and final budget.

Tower and substructure scope
The high-level scope is to define improved design and analysis methods and calibrate safety factors for tower and substructure, aligned with the Phase 1 safety level. This will be done by narrowing analysis scope and reducing unnecessary conservatism.

For selected tower and substructure designs, and construction materials, we plan to: 

  • Review the DNV-ST-0119 DLC matrix and identify non-governing DLCs for tower/substructure
  • Define standardized time domain analysis methods for the condensed DLC set
  • Calibrate safety factors using the condensed DLC set and standardized time domain analyses, aligned with Phase 1 safety level

Mooring and cable scope
Phase 2 will expand the Phase 1 mooring and cable calibration by adding concepts not yet covered, identified by Phase 1 participants as relevant for future wind farms. The goal is to ensure DNV-ST-0119 covers the key solution space across floater types, water depths, locations, and mooring/cable configurations.

To address the unresolved Phase 1 scope, the following scope is proposed for Phase 2: 

  • Barge floater in one Phase 1 location (mooring/cable layout to be agreed with SC)
  • Deep-water location (US West Coast discussed in Phase 1; Japan as alternative). Floater type and mooring/cable layout to be agreed
  • Innovative mooring concepts (e.g., shared mooring) assessed qualitatively against Phase 1 cases

Benefit

The work will support an update of DNV-ST-0119 and enable cost-optimized designs for global structure, mooring, and cable systems. More aligned requirements and design principles should improve predictability for developers, designers, manufacturers, and financiers/insurers - with positive impact on cost and schedule.

Duration

Phase 2 is planned to kick off in Q1 2027.

Phase 1 participants

Acteon/Bruce Anchor, Aker Offshore Wind/Mainstream Renewable Power, Aker Solutions, APL -NOV, Bardex Corporation, BayWa r.e. Offshore Wind, Bluewater, BP, Brunel Floating, Cathie, Corio Generation, COWI, Delmar Systems, Delp, DOF Subsea, EDF Re, EnBW, Equinor, Goldwind, Hafslund, Hengtong, HSE, Iberdrola, Invenergy, Kongsberg Maritime, Ming Yang, Mooreast, Moreld, Nexans, NKT HV Cables, Noble Drilling, Ocean Winds, OMV, Ore Catapult, OSI Renewables, PSA, RWE Offshore Wind, Ryder Geotechnical, Saipem, SBM, Schottel Marine Technologies, Shell, Sofec, SSE Renewable Services, Statkraft, Stiesdal Offshore, Subsea7, Sumitomo Electric, TechnipFMC, Teijin Aramid, TotalEnergies, Vattenfall, Vicinay Marine, Ørsted Wind Power.

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