Review on mooring systems for floating offshore wind: Design optimisation trends and challenges

Offshore wind has a key role to play in moving towards a net-zero energy system, and Floating Offshore Wind (FOW) could open up deep-water sites with the potential to harness 80% of Europe’s offshore wind resource. Although conventional floating platform and mooring technologies have been successfully used in pre-commercial floating offshore wind deployments of up to 120m of water depth, deployments in very deep waters and with increasing turbine sizes pose further technical and cost challenges. For example, the costs and footprint of mooring lines increase with water depth. A diversity of solutions have been proposed for different deployment conditions. For this reason, it is key to identify the design drivers and technical challenges for the design and selection of platform and mooring solutions at early project development stages. A comprehensive literature review and comparative analysis were conducted, encompassing real-world FOW projects, component supplier data, and both academic and industrial design and optimisation studies. The review classifies mooring designs, and assesses their suitability under varying deployment conditions. The results reveal trends in preferred designs for semi-submersible platforms: catenary systems for shallow waters ( < 200m), hybrid and semi-taut configurations for intermediate depths, and taut systems for very deep waters ( > 800m). Fatigue at the fairlead, especially in chain segments, emerges as a critical design driver, alongside cost and footprint constraints. Moreover, modelling challenges with synthetic fibre ropes due to non-linear load-extension behaviour highlight key areas for future research. This review provides actionable guidance for selecting and optimising mooring systems in FOW applications through a consistent parametric optimisation approach, that supports more efficient designs processes and facilitates informed decisions during early project phases. • Trends for preferred designs depending on water depth have been identified. • Fatigue is design driving for chain components and needs to be considered in early mooring design. • Constraints of manufacturing and installation processes limit the realistic design space.