Performance and multi-objective optimization of a ship-integrated internal wave energy conversion system

Ship-integrated wave energy converter offers a promising solution for onboard renewable power generation without modifying the external hull geometry. This study investigates an internal heaving-oscillator wave energy conversion system integrated into a container ship. A fully coupled time-domain mathematical model is developed to describe the dynamic interactions between ship motions, the internal power take-off system, and incident waves. The model is validated against experimental ship motion data, demonstrating good accuracy and computational efficiency. The steady-state performance of the coupled system is examined under regular wave conditions, focusing on the effects of wave period, wave direction, and forward speed. The results indicate that forward speed significantly alters wave encounter characteristics and shifts the optimal energy capture toward head and near-beam sea conditions at the service speed of 24 knots. Parametric analyses further show that power take-off damping and stiffness strongly influence energy capture efficiency. To evaluate realistic operational performance, a surrogate-assisted multi-objective optimization framework is applied under irregular wave conditions representative of the South China Sea along the Hong Kong–Singapore shipping route. The results demonstrate that substantial improvements in energy capture can be achieved without excessive mechanical loads, confirming the feasibility of internal wave energy converter integration for large commercial ships.