A Model-Based Evaluation of Wave Collision Effects on the Multi-Objective Optimization of Hybrid Ships Sizing

Ship hybridization has increasingly attracted attention to accomplish the 2050 emission goals. However, despite the recent benefits of utilizing a hybrid ship power system, additional power fluctuation sources in an All-Electric Ship (AES) power system have evolved. These variations must be thoroughly examined at the vessel design and control level. Otherwise, the optimum performance of the ship power system in various sea situations cannot be theoretically guaranteed. One of the crucial circumstances under which propellers generate power variations in the AES's power system is wave collision. This paper focuses on the effect of ship motions on the sizing and control optimization of hybrid ship propulsion systems at the design level. First, a model-based approach is proposed for integrating the in-and-out-of-water effect into an existing load profile from a specific journey. By utilizing the proposed strategy, a load profile can be modified to represent the power fluctuation of the extreme conditions. Then, a nested double-layer multi-objective optimization problem for sizing and controlling hybrid vessels is presented. The influence of incorporating wave collision on the sizing optimization of hybrid vessels is investigated using the presented optimization approach and model-based load profile adjustment. It is shown that the in-and-out-of-water effect resulting from ship movements in extreme conditions can substantially impact the sizing of the all-electric ship's components. In addition, it can significantly increase the diesel fuel consumption of the vessel. Therefore, the ship motions should be considered to ensure an optimum design and control in various operation conditions during the ship's lifespan.