As a result of the Paris Agreement, energy technologies require to shift from fossil fuel based to carbon neutral. In 2015, the maritime sector was responsible for 2.6 % of the global CO2 emissions. The combination of the solid oxide fuel cell fueled by sustainable synthesized ammonia is seen as a potential solution to reduce emissions. Ammonia is considered as a balanced solution in terms of ease of storage, volumetric energy density and cost of production. The solid oxide fuel cell is generally regarded to be a promising technology owing to its high eciency and combined heat and power usage. This MSc thesis investigates the technical viability of a sustainable SOFC propulsion system fueled by ammonia. Technical viability is expressed in equipment weight and volume, whereas sustainability is determined by efficiency and emissions. The solid oxide propulsion system is subjected to a case study: A diesel engine powered vessel from the Watertaxi Rotterdam company with an assumed shaft power of 25 kW. A model was compiled to determine the efficiency, weight and volume of the solid oxide fuel cell system. The model covers activation losses, ohmic losses and diffusion losses within the solid oxide fuel cell stack. With the model, a sensitivity study with a selected set of system parameters was performed to gain insight in the solid oxide fuel cell system. The selected system parameters are: Number of cells in the stack, single-pass fuel utilization, cathode off-gas recirculation rate and anode off-gas recirculation rate. The final solid oxide fuel cell system has a signicantly higher efficiency based on the higher heating value than the diesel engine system: 46.0 % versus 35.0 % respectively. Also, no carbon dioxide is emitted, leading to a reduction of 56.9 ton per year. Furthermore, nitrogen oxide emissions are considered to be negligible compared to the diesel engine system. However, the weight and volume of the solid oxide fuel cell system are signicantly larger: 1199 kg versus 278 kg and 1175 L versus 432 L respectively. Mainly caused by the battery module, required for compensating for temporarily imbalances between power demand and power supply. As a result, it is concluded that the solid oxide fuel cell system is unpractical for the small inland vessel selected for the case study. Larger sized vessels have more potential for the application, because large sized vessel sail more continuously, reducing the battery capacity requirement, may allow for more tolerance regarding heavy and bulky equipment and have more benefit of the higher efficiency due to a lower refuel frequency.

Fossil fuels are currently the primary source for electrical power generation, which subsequently increases the rate of greenhouse gas (CO2, CH4) emission. It has been agreed at the Climate Change Conference 2015 in Paris (COP21) to reduce greenhouse gas emissions in order to limit the global temperature increase to less than 2°C compared to pre-industrial era temperature. The GHG (Greenhouse Gas) effect is mostly attributed to methane and carbon dioxide emissions into the atmosphere. In order to reduce the use of fossil fuels and their negative impact on the environment, renewable energy resources have been receiving much attention in recent years. Sanitation systems, centralized Wastewater Treatment Plants (WWTPs) and organic waste digesters give an ample opportunity for resource recovery to produce biogas that contains mainly methane and carbon dioxide. The low conversion efficiency of conventional energy conversion devices like internal combustion engines and turbines prevents biogas from reaching its full potential as over 50% of chemical energy is dissipated. Wastewater treatment is a developed technology from human health and environmental-friendliness points of view. However, from energy aspects, it is still an energy-intensive process step. Wastewaters might contain significant amounts of organic matter and nutrient (nitrogen and phosphorus) compounds. The chemical energy in domestic wastewater is approximately 3.8 kWh.m-3 based on theoretical Chemical Oxygen Demand (COD) of 1 kg m-3. At wastewater treatment plants (WWTPs), collecting and treating wastewater streams need a considerable amount of electricity (0.5 kWh m-3) to reach an acceptable quality of discharge requirements. In a conventional WWTP, nitrogen is removed through nitrification, and biodegradable organic matter is converted to methane in anaerobic digestion. The energy demand at WWTPs could be partially offset by an efficient recovery of nutrient and organic matter from the wastewater stream. Biogas production is an important technology widely applied in Europe. Biogas can be converted to energy through thermal conversion with combined heat and power (CHP) plants. However, the electrical efficiency of the system is limited to 25-30%. In parallel, nitrogen can be removed from wastewater and converted and stored in the form of an ammonia-water mixture from ammonium-rich streams after anaerobic digestion. Solid oxide fuel cell (SOFC) is an energy conversion device that directly converts chemical energy into electrical energy based on electrochemical reactions. SOFC can operate with different types of fuels, especially unconventional or renewable fuels. The efficiency of SOFC is higher compared to conventional combustionbased processes. Therefore, the sustainability of WWTPs can be improved first by a recovery of nutrient and organic material from the wastewater stream and then, replacing the inefficient combustion process with an efficient high-temperature electrochemical reaction in SOFC. Due to the modularity of SOFC, this can be used for a wide range of biogas production capacities at WWTPs. However, the development of SOFC is still facing many challenges, and a better understanding of the constraints is needed. This dissertation aims to provide design concepts and thermodynamic system analysis for the biogas-ammonia fuelled SOFC system at wastewater treatment plants with a focus on achieving a safe operating condition and high electrical efficiencies. Thereupon, extended experimental studies have been conducted in this work on biogas dry and combined reforming. Moreover, the influence of mixing ammonia-water to biogas in SOFC has been experimentally investigated. After indicating the safe operating condition of biogas-ammonia fuelled SOFC, system modelling studies have been carried out in order to design an efficient conceptual biogas-ammonia fuelled SOFC system at wastewater treatment plants. Additionally, a complete biogas SOFC pilot system consists of a gas cleaning unit and an external gas processing system has been designed. @en

Global warming, caused by the excessive release of greenhouse gases due to the use of fossil fuels, is the main reason why a switch to renewable energy sources is becoming a necessity. A renewable energy source with a high potential to contribute to the energy needs worldwide is biomass. Biomass can be used for the production of electricity and heat or for the production of chemicals for a wide range of applications. The overall challenge for the thermal conversion of biomass is the development of robust and efficient technologies to process biomass with a high conversion efficiency into a useful and clean product. Biomass pyrolysis has great potential to convert a wide range of biomass species into various products. In this project, the decomposition characteristics of two high-potential biomass feedstocks, Miscanthus and Ulva, were investigated. The grass species Miscanthus has been in the spotlight as a potential biomass feedstock due to its rapid growth, high biomass yield potential and high calorific value. There is a growing interest in the seaweed species Ulva as a potential biomass feedstock due to its rapid growth and due to the fact its use may lead to a reduction of ecological problems (Ulva is a major sea pollutant). Decomposition characteristics of Miscanthus and Ulva at slow heating rates were investigated with a thermogravimetric analyser. Proximate analysis results and mass loss rate graphs were obtained. The shapes (peaks) of the mass loss rate graphs were linked to the different biomass components present in Miscanthus and Ulva. For the decomposition at fast heating rates pyrolysis experiments were carried out in a Pyroprobe reactor. The solid, liquid and gaseous product yields were analysed for different final pyrolysis temperatures. The compositions of the gas fractions were analysed using a micro gas chromatograph. The influences of pyrolysis temperature and biomass feedstock composition on the product yields and compositions were linked to different pyrolysis mechanisms In order to determine the role of different biomass components in the pyrolysis process, the decomposition of the biomass feedstocks and pyrolysis kinetics are further investigated by modelling the mass loss rates of Miscanthus and Ulva during slow pyrolysis obtained from thermogravimetric analysis. For this purpose, the independent parallel reaction (IPR) model was used. The experimental and modelling results obtained in this study for Miscanthus and Ulva help characterising the two biomass species. Based on the decomposition rates, product yields and gas compositions, a better understanding of the pyrolysis reaction mechanisms of the different constituents of Miscanthus and Ulva is gathered. This is a contribution to the knowledge required to optimise thermal conversion processes for different biomass species.

The interest in alternative fuels in the maritime sector is growing due to increasing concerns of the effect of harmful emissions. Hydrogen in combination with a fuel cell has a high potential to be a more environmental friendly solution than the commonly used fossil fuel systems. However, the use of hydrogen encounters problems looking at the fuel storage density, safety and the operating profile of a vessel. Hydrogen storage in a material, such as sodium borohydride, has the potential to overcome or mitigate these problems. The goal of this research is to provide an insight in the technical feasibility of this technology for the maritime industry. Therefore, the following research question will be answered: How does a technical design of a power train using sodium borohydride as hydrogen storage material on-board of vessels perform in terms of power and energy density and in a transient load? There are three important elements in this system: the sodium borohydride, water and the spent-fuel. The hydrogen in sodium borohydride can be released in a reaction with water, resulting in a hydrogen gas and liquid spent-fuel. The energy and power density is determined using the weights and volumes of these separate elements. Both the least, and most compact configurations are considered to determine the operating range of this technology. A model is made and measurements are done on the power demand of the `Stad Amsterdam' to investigate the performance of the system on dynamic behaviour. The most slow components, such as the mix-chamber, fuel cell and the battery system, are dynamically modelled to identify the critical elements in the design. In the first configuration, all fuels are stored in separate tanks and all the water needed for the process is stored on-board. This results in a low volumetric energy and power density. To improve the density of the system multiple concepts are considered: a concentrated or dry fuel, a volume-exchange tank, on-board water generation and a filtered spent-fuel. Implementing these concepts results in a compact configuration which is more competitive with diesel systems and other alternative fuels. The hydrogen buffer in the mix chamber, the fuel cell and the battery systems are the most important elements influencing the performance of the system in a transient load. A more constant behaviour can be expected by making use of multiple mix chambers. The safety on-board of the vessel still needs attention, especially around the places containing hydrogen gas and where hydrochloric acid is present. It can be concluded that this technology has a high potential for many types of applications in the maritime industry. It will be technically feasible to implement such a system on-board of a vessel. The harmful emissions in this industry can be decreased significantly using this system. Cost and safety of the system are a challenge and, therefore, further research has to be done to realise the implementation of these systems on-board of vessels.