Holistic approach to design a fuel cell hybrid system for maritime application

This thesis presents the holistic design of a hybrid power system and propulsion system for ferry applications based on a Proton Exchange Membrane Fuel Cell (PEMFC). In the zero carbon energy transition scenario, hydrogen fuel cell (FC) technology is the protagonist for stationary power systems and medium to long range electric transport. In marine applications, especially for vessels operating in coastal areas, PEMFCs are a solid alternative to batteries, as they can provide a higher energy density due to the separation between the PEMFC and the energy storage (H2 tank). At present, the penetration of this technology into marine power systems is limited by the cost of manufacturing fuel cells and the high purity of hydrogen as a fuel. In addition, companies offering PEMFC-based power generation solutions to the marine market must design the product to meet customer requirements, which are different for each application. This significantly increases the cost and resources involved in each project. The aim of this work is to provide an effective tool for the preliminary design of PEMFC systems that considers the fuel cell in a hybrid configuration, taking into account the interaction with all other equipment on board. The holistic approach, together with the sizing of the FC system, provides important insights into the sizing of the other power system components. The simulation framework, developed in the Matlab-Simulink environment, uses models of different complexity for each power system component, taking into account the degree of interaction with the PEMFC. Thus, the other energy sources, such as batteries and internal combustion engines, are modelled taking into account the dynamics of these systems and the efficiency of the converters used to distribute the energy to the electrical grid. The proposed on-line energy management system (EMS) selects the operating mode, taking into account the ship’s power requirements and the remaining battery capacity, and chooses how to use the power available on shore. The modelling included not only the power systems but also all the ship’s characteristics, from hull resistance to propeller power. This was done in the case of a new ship design to know the power required during operation. The simulations assess the feasibility of the hybrid PEMFC power system, taking into account the main criticalities reported in the scientific literature, such as transient performance, FC degradation and thermal management. The optimisation framework then finds the solution to achieve the best performance in terms of FC stack degradation over one year of ship operation. The chosen case study is an existing ferry that is currently powered mainly by batteries and diesel generators in an DC network. The proposed results of the zero-emission power system configuration, based on the PEMFC and the battery, show the performance of the whole system during 5100 operating hours, and in particular, the efficiency of the PEMFC and of the applied thermal management strategy.