a review on propulsion drive trains of electric ships: structures, challenges and opportunities

Development of marine industry has caused a significant increase in fuel consumption of global shipping as well as pollutant greenhouse gases. it is forecasted that marine industry will account for 20% of global carbon footprint, 9% of sox emissions, and 15% of nox pollutants by 2050. studies reveal that carbon, nitrogen and sulfur oxides deteriorate seawater quality, which may diffuse in air and affect human health. in this regard, renewable energy sources and storage units are capable to save more energy and mitigate pollutants emitted from fueling internal combustion engines (ices). this paper aims to present a comprehensive study on electric ships’ structure and operating modes, prime movers, energy sources including non-renewables and clean ones, benefits and challenges in electrification of marine industry. it is found that electric ship propulsion drive trains typically consist of electric motors, power electronic devices such as inverters and converters for flowing electricity from battery or fuel cell to electric motor, battery energy storages, and controllers for managing speed, torque, and direction of motor rotation. some challenges of electric propulsion systems are the weight and space required for batteries, overheating of motors and power electronic devices, and lower energy density of storage compared to traditional fossil fuels-based ones. the main advantages of marine transport electrification include less greenhouse gas emissions and ecological footprints, lower operation and maintenance costs of electric motors compared to marine-scale diesel engines, noise reduction, and the improved maneuverability as a result of better torque control during navigating through congested waterways.