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In this article, a data-driven dynamic efficiency model is developed for efficiency evaluation and comparison of ship electric powertrain with various system configurations. Based on the proposed method, the entire powertrain efficiency is assessed from the fuel consumption to the propulsion unit and the rest of the onboard load. The efficiency model is repeated for the conventional diesel electric and the hybrid power system with batteries. In the latter case, the efficiency of the battery system is also included in the model. Then, the analysis is extended for different power system architectures such as AC and DC onboard power systems. As a case study, system efficiency in a cruise ship is investigated using a real operational profile. A comprehensive analysis is performed to demonstrate the loss distribution in each subsystem of a hybrid AC and DC power system. For a fair comparison between AC and DC, the battery charge level is equalized based on fuel compensation. The case study shows that hybridizing the ship power system increases system efficiency and enhances operational flexibility for the studied use case vessel. Furthermore, the DC hybrid power system can improve the efficiency of the whole ship powertrain due to the variable-speed operation of engines.
Ghimire et al. (2021) studied this question.