Hybrid Mooring Design for a Pendulum-Based Wave Energy Converter

Abstract

This research presents a comprehensive mooring design flow for a pendulum-based wave energy converter, including the design of extreme and operational sea states, a step-by-step mooring optimization, and a code check for Ultimate Limit State (ULS), Accidental Limit State (ALS), and Fatigue Limit State (FLS) based on the DNV standard. The numerical model built in OrcaFlex was validated through an experimental campaign and used for mooring design. Finally, a 3-leg hybrid mooring system consisting of elastic ropes and catenaries was obtained. Its comparison with the original design demonstrates a production increase of at least 20.7%, and the durability of the mooring system was also improved, mainly due to pretension and fairlead position adjustments. Besides, the safety code check results illustrate that fatigue damage functions as the primary threat for such a pitch-dominated device, indicating the importance of considering fatigue damage in preliminary design to avoid undesired mooring with high service life in ULS while significantly low design life in FLS. This work provides a comprehensive reference for future mooring design of the WECs that operate mainly on pitch motion, and the findings contribute to the research toward practical application of such wave energy technologies in rotating mass.

Keywords

Mooring design / Wave energy converter / Rotating mass / OrcaFlex

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