Climate change and greenhouse gas emissions have been at the forefront of both public and academic debate for some years. Although the shipping industry has managed to remain relatively free of climate regulation this is changing with the IMO goals for 2050. The military sector has also escaped scrutiny on sustainability issues. But this is also changing as the Dutch Ministry of Defence expressed the ambition to reduce its carbon footprint, with the eventual goal to reduce the operational dependency on a scarce resource, and to comply with national and international regulation. The direct aim, therefore, is to reduce the fossil fuel consumption by 70%, and to comply with IMO regulations by 2050. In this thesis the possibilities for reducing fossil fuel consumption and greenhouse gas emissions will be examined. This will be done for the seagoing large surface vessels of the Royal Netherlands Navy by using alternative fuels. This question is answered through the execution of two case studies of vessels with different mission profiles: the Zeven Provinciën class Air Defence and Command Frigate and the Landing Platform Dock Johan de Witt. For both vessels, a design process is carried out in which more detail is progressively added whilst down selecting the most suitable technologies. The first step in the design process is an operational analysis. This operational analysis uses the perceived missions profiles and the RNLN maritime doctrine to make a prioritization in a set of technical properties or measures of effectiveness. In the second design step, a systematic design variation is used to estimate the effect that different energy carriers have on the main dimensions of the vessel. The parametric design tool developed for this is an adapted version of the SPEC tool developed by Marin. The model estimates the required power and the weight of different weight groups of the vessel. The final design step continues with a more detailed proposal for a power plant configuration for both case studies. With this detailed design a final assessment of the fuel consumption, exhaust gas emissions, and operational effectiveness is made. Throughout the design phases it was established that the displacement of both vessels would increase significantly due to the lower energy density of the selected fuels. In the case of the Air Defence and Command Frigate, the high top speed and relatively high fuel and system weight lead to a larger increase in required fuel and installed power due to the increasing resistance when using anything but the most energy dense fuels. For the Landing Platform Dock, which has a more modest power requirement and a relatively low system and fuel weight, the increase in displacement is smaller. In conclusion, it can be said that the goals stipulated by the Ministry of Defence are attainable. The effect on the operational effectiveness varies between vessels but the overall fuel consumption, cost, and displacement are sure to increase significantly.

The Royal Netherlands Navy (RNLN) seeks to eliminate net green house gasses and other harmful- emissions. In this search, the operability of her vessels need to be secured. One of the options for eliminating net carbon emissions is Power to Liquid (PtL) conversion to Methanol. Fuel cells, and in particular Solid Oxide Fuel Cells (SOFCs) may be useful tools to power naval vessels efficiently and without the production of pollutants. The dynamic behaviour of these systems however is where a challenge is found. Contrary to methane fuelled SOFCs, little research has been done on the behaviour of methanol fuelled SOFCs in the higher temperature range. It was decided that for this thesis the SOFC system would be pressurised to 20 bar to increase power density, a pre-reformer would be incorporated to improve dynamic behaviour, a Plate Heat Exchanger (PHE) would be used to re-integrate heat from the cathodic outflow to the cathodic inflow, and Anode Off Gas Re-Cycling (AOGRC) would be used to provide steam and heat to the pre-reformer. A model was built that incorporates the following sub models: a pre-reformer that includes reaction kinetics, a dynamic SOFC stack model which incorporates heat losses normal to the cell orientation, and a extcolor{cyan}{PHE} which includes its dynamic behaviours. These models are interconnected and controlled such, AOGRC is mimicked. These models were verified by checking energy- and mass-balances. The eventual chemical equilibrium of the (kinetics based) model of the pre-reformer was used to validate the pre-reformer model. The leading research by (Aguiar et al.) was used to validate the SOFC model. Typical thermal behaviours of PHEs were used to validate the PHE model. Simulation results show that the pre-reformer could improve the system dynamics by providing a pre heated, hydrogen rich gas mixture to the SOFC. Running it at a temperature of higher than 530 K can pose danger due to more prominent exothermic, methane producing, reactions in the reactor vessel. Results from testing the SOFC show that the SOFC is best operated at an inflow temperature of around 800K for maximum efficiency (including outflow enthalpy). It shows that the SOFC is barely influenced by higher partial pressures of the reactants, and has slow load following characteristic, especially for low terminal current densities. The testing results for the PHE show that the this subsystem achieves higher heater effectiveness when more conductor plate area is used, but at the cost of dynamic response. It also shows that the PHE is the most important factor in the poor load following capabilities of the entire system. This is largly due to the limited convective heat coefficient. AOGRC has been shown to be an effective method to control the temperature of the pre-reformer, low AOGRC ratios make for large preventable energy losses. The interconnected methanol fuelled SOFC system simulation shows that external heating of the ingoing anode flow is detrimental to the efficiency of the system, but it could be instrumental in preventing thermal stresses on the Positive-Electrolyte-Negative (PEN) structure of the cell. Increasing the fuel and airflow excess is also detrimental to the system efficiency. These values are best kept at 1.1 due to uncertainty around for the models` accuracy for very low fuel- and air- flow excess. The settling time for the power output is in the order of several hundreds of seconds, and is largest for large sudden changes in power demands, and low terminal power demands. It was concluded from these results that the here proposed system is not suitable to power a naval vessel of the Snellius class in a satisfying way. The investigation however, has produced valuable tools for future work. Recommendations for future work are to implement condenser/heat exchanger for the anode anode off gas, implement a burner to make use of the remaining chemical energy in the anode off gas and install a turbine to make use of potential energy in the outflowing gasses.