The primary objective of this thesis is to compare the application of various alternative fuels in combination with fuel cells in maritime environments, aiming to reduce harmful emissions in marine transportation. These emissions are partly caused by the chemical composition of maritime fuels and partly by combustion processes in internal combustion engines and fuel cells. The application of fuel cells and alternative fuels has the potential to mitigate these emissions. Other research has considered the application of alternative fuels and fuel cells onboard ships, but the difference between using these various fuels in combination with fuel cells has not yet been researched in great detail. This study compares various alternative fuels in combination with fuel cells onboard ships by performing a case study where fuel cells and alternative fuels are integrated onboard an offshore vessel.
This thesis includes a review of existing literature on fuel cells, fuel processing, fuel storage technology, and maritime applications to select the most suitable technology for implementation onboard ships.
First, the most suitable fuel cell type for maritime applications is selected based on efficiency, durability, and operational requirements. Proton exchange membrane fuel cells (PEMFCs) and solid oxide fuel cells (SOFCs) are considered suitable fuel cell types for maritime applications; low-temperature PEMFCs are the most suitable of these two. Next, techniques for fuel conversion and purification, such as methanol reforming, ammonia decomposition, and carbon monoxide removal, are analyzed. These processes consume mass and volume onboard the vessel, reduce the power system’s efficiency, and reduce the transient response capabilities of maritime fuel cell systems. After this, liquid hydrogen, ammonia, and methanol are investigated as alternative fuels in this report. The physical properties of these fuels result in different storage conditions for each fuel. In addition, the health and safety aspects result in additional rules and regulations for storing and using these fuels onboard ships.
To perform the case study, the vessel’s operational profile is used to calculate the required power and energy for the vessel to conduct its operations. Next, the required power for auxiliary components to support the power and energy storage systems is calculated. Using these power and energy requirements and the losses occurring in the systems, the components of the power and energy storage systems are sized. The case study showed that liquid hydrogen storage in combination with PEMFCs consumes the least volume onboard ships for lower autonomies. For higher autonomies, ammonia or methanol-fueled PEMFC systems consume less volume. In all cases, the PEMFC-fuelled systems, in combination with alternative fuels, require more volume onboard the vessel than internal combustion engine-based systems operating on marine diesel oil. The trends for mass and volume requirements by the power and energy storage systems are expected to remain similar for other vessels. Besides the differences in mass and volume between the designed systems operating on alternative fuels, this thesis concludes that integrating fuel cell technology in maritime vessels is theoretically possible. However, it also points out the need for further research, development, and practical experience regarding the installation and operation of fuel cell systems and alternative fuel storage onboard ships. In addition, it is important to consider energy losses caused by auxiliary power consumers.
This thesis compared maritime fuel cell systems operating on alternative fuels from a technical perspective. For purposes where costs are also an important indicator when comparing various fuels, it is recommended that further research into the economic feasibility of installing and operating fuel cell systems and alternative fuels onboard ships is performed.