Evaluation of hybrid monopiles as next-generation foundations for offshore wind turbines

The offshore wind industry faces critical challenges from rapid turbine size growth, limited installation vessel capacity, and the need to extend the service life of aging infrastructure. With wind turbine generators reaching 26 MW and monopiles expected to exceed 2500 t by 2030, up to half of European installation vessels may become unsuitable for these heavy foundations. This study evaluates hybrid monopile foundations as next-generation solutions integrating conventional monopiles with supporting structures such as footings, collars, or suction buckets. A review of hybrid foundation concepts is first presented, including monopile-footing, collared monopile, monopile-bucket, and monopile-three-bucket configurations, along with their installation methodologies and associated challenges. Finite element simulations using the NGI-ADP constitutive model in soft clay demonstrate that hybrid foundations can outperform conventional monopiles of equal steel volume. The monopile-bucket and monopile-three-bucket provide the highest lateral capacity, improving performance by up to 21.4 %. Staged installation allows the use of smaller vessels but introduces additional complexity in installation sequencing. Field deployments at Kaskasi (collared monopile) and Putian Pinghai Bay OWF (monopile-bucket) demonstrate practical feasibility. Hybrid foundations represent a strategic approach that accommodates installation constraints, optimizes material use, and enables foundation improvement to extend offshore wind turbine service life. • Hybrid monopiles are considered as next-generation solutions for addressing offshore wind foundation challenges. • Four hybrid concepts are evaluated: footing, collar, single-bucket, and three-bucket. • Staged installation of hybrid monopiles lowers vessel demand and field trials confirm practical feasibility. • Finite element results show bucket hybrids outperform monopiles with equal steel volume.