Optimization of mooring line axial stiffness characteristics for offshore renewable energy applications

Abstract

Expanding on existing methodologies for the design optimization of mooring systems for offshore renewable energy devices, this paper explores the optimization of the axial stiffness of a mooring system, a key property that governs the motion of the moored renewable energy device. The optimization using a covariance matrix adaptation evolutionary strategy is executed with respect to both the motion response of the moored device, and the cumulative fatigue damage in the mooring lines. Previous mooring system optimization work has focused on geometry optimization of the system considering known material properties, whilst this paper explores the optimization of the axial stiffness properties of the mooring system identifying ways in which the response of the system can be optimized through changes in the material properties. Considering the case of a moored heaving buoy similar to an offshore renewable energy device, the present case study optimizes the mooring system simultaneously minimizing the cumulative fatigue damage in the mooring lines while also maximizing the heave response which is responsible for the energy generated by the device