Calling for entries from companies and consortia interested in undertaking a study to assess freeboard requirements for floating offshore wind (FOW) substructures, with a view to improving industry understanding and supporting future standardisation. While blade‑tip clearance and WTG tower access requirements are generally well-defined in existing design standards, approaches to freeboard, airgap, and column or deck submergence remain inconsistent across the industry.
Current practice varies significantly due to differences in floater typologies; some floater concepts allow controlled column or deck submergence to reduce primary steel or concrete volume, accepting increased CAPEX for secondary reinforcement and higher OPEX from potential green water impacts and slamming loads. Others prioritise maintaining positive freeboard under most operational conditions, improving resilience at the expense of increased structural volume.
Maintaining adequate clearance becomes challenging in harsh environments, where avoiding wave on deck may be impractical. Increasing freeboard can lead to heavier, more expensive structures and may complicate accessibility for vessels such as SOVs. As a result, two main strategies are observed within current designs:
- Design to avoid wave on deck and slamming entirely, or
- Design to withstand wave on deck loads, accepting reinforced structures and potentially higher O and M costs.
Selecting the appropriate strategy requires balancing CAPEX, OPEX, structural integrity, environmental conditions, operational considerations, and project specific consent requirements (e.g., blade tip clearance rules). A clearer and more consistent framework is needed to support developers, designers, and regulators.
The Floating Wind JIP would like to:
- Review existing floating wind guidance on substructure freeboard requirements
- Define applicability conditions
- Assess design implications
- Evaluate risk and cost trade-offs
- Develop recommendations
The deadline for clarification questions is 6 February 2026
The closing date to receive tender submissions is 6 March 2026.
All clarification questions and tender submissions should be sent electronically, by their respective deadlines to Arturo.andersen@carbontrust.com, with floatingwind@carbontrust.com in copy.
