A Methodology for Site-Wide Structural Optimisation and Advanced Clustering of Monopile Foundations for Next-Generation Offshore Wind Turbines

Abstract Industry trends of using ever-larger wind turbine generators and developing farms in deeper waters with longer design lives have resulted in increased importance of optimisation of monopile foundation structures due to their favourability over more complex foundation types. Optimisation is crucial to adequately assess feasibility of monopiles, and to efficiently design the structures to minimise capital expenditure and levelised cost of energy. This paper presents a methodology for site-wide design space exploration and optimisation of monopiles to address these challenges, using OPTIF, Arup’s in-house tool for design and optimisation of offshore wind foundation structures. The methodology employs heuristic and numerical optimisation approaches to rapidly optimise many thousands of monopile geometries for given site conditions and design constraints under the governing load cases, providing both designs that minimise total mass, and valuable insights into site-specific effects. The methodology is applicable at both early-stage and later FEED/detailed design stages, employing highly-accurate, site-specific loads analysis fully integrated with the structural optimisation to enable accurate early stage foundation weight estimates, provide valuable insight to inform advanced clustering, and allow for position-specific optimised geometries at later stages. The methodology is applied to an early-stage design case study to identify optimum mudline diameters across a typical site, and this study is used to illustrate the possibility for more advanced clustering methods informed by rapid site-wide mass sensitivity studies using varied input parameters and clustering approaches.