Parametric study on the effect of mooring configurations on the dynamic responses of the Septon semi-submersible 5 MW floating wind turbine

Abstract

Offshore floating wind turbines (FWTs) offer a promising solution for harnessing wind energy in deep waters, where fixed-bottom turbines become impractical. Over the past decade, consistent advancements in technology have significantly reduced the levelized cost of energy, making large-scale deployment of FWTs increasingly feasible. The key factors influencing both cost and performance include the design and optimization of the substructure, mooring system, and power grid. The mooring system plays a pivotal role in ensuring platform stability and minimizing excessive motions that could impact the energy production efficiency and structural integrity of the FWT. The present study investigates the effects of different mooring configurations on the dynamic response of a novel semi-submersible wind turbine platform. This study analyzes two distinct mooring arrangements, spread mooring and cross-mooring, to determine the optimal configuration. The numerical investigation takes into account multiple parametric variations, including spread angle, cross angle, mooring line diameter, and line length, assessing their effects on platform motions and mooring line tensions. Numerical simulations are performed using an aero-hydro-servo-elastic simulation, which considers the coupled interactions of wind, waves, and structural components under various irregular sea states. This study reveals that the choice of mooring configuration significantly affects both platform stability and mooring line loads. A spread mooring system with a 30–60° divergence angle is identified as the optimal configuration for minimizing platform motions while keeping mooring tensions within safe operational limits. Conversely, cross-mooring configurations tend to exhibit higher tensions, particularly at larger cross angles. The cross-moorings require a minimum of 15–35 m additional mooring length compared to spread moorings for line tension to be within safe limits. The findings from the present study offer valuable insights into the optimal design of mooring systems for floating wind turbines, contributing to enhanced performance and reliability in deep water offshore wind farms. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.