Modeling and Experimental Validation of a Hybrid Electric Propulsion System for Naval Applications

Focusing on coastal or inland navigation cities, where emissions from ships are not negligible concerning global ones, the possibility of reducing exhaust gas pollution would have more benefits for public health and air quality. Therefore, in recent years, increasing attention on environmental sustainability is driving the shipbuilding industry towards greener propulsion based on full-electric or hybrid-electric propulsion systems. This work is presented a parallel hybrid system composed of two electric motors, one internal combustion engine, and lithium battery storage. All motors are coupled to the propeller through a specially designed transmission system based on the High Sliding Gear theory (HSG). The hybrid-electric propulsion system is designed to extender the battery pack durability, ensuring a smooth profile of the required current, through the complementary action of the batteries and the internal combustion engine. Then, the overall performance of the hybrid propulsion system is verified by laboratory experimentations, also testing the energy storage system. A fast boat (yacht) is chosen as a simulation case where a lumped parameters model is coupled with map-based motors obtained from experimental test activities performed on this hybrid propulsion system. This model is also validated by the available performance data obtained during an experimental campaign where has been emulated a typical propeller load. The results show the feasibility of this hybrid architecture, in terms of performance and sustainable maritime transport. Furthermore, the simulation results confirm the experimental performance, proving to be a good tool for system development in terms of energy management.