Nuclear power is currently not a commonly used option in commercial marine applications, despite its potential for significant emission reductions. This thesis is an overview of what has been done before, and what the potential is of modern marine nuclear power applications considering the long-term goals of harmful emission reduction in the maritime industry.
The concept of nuclear power is discussed, followed by the current state of nuclear power in both the shore-based, naval and the mostly historic marine application. The regulations for the marine application are noted to be outdated and require significant work for a successful application. Finally, the societal aspect of nuclear power is highlighted, as societal acceptance is not self-evident for nuclear power applications.
Different developments in the field of nuclear power are addressed, with specific interest in the SMR (Small Modular Reactor), concepts that are part of the “generation IV” family, and concepts that can operate using thorium as fuel. Multiple options are considered, from the well-established PWR (Pressurized Water Reactor) to the gen IV concepts: the HTR/VHTR (high/very high temperature reactor), fast reactors in both gas-cooled, liquid-metal and sodium cooled varieties (GFR, LFR, SFR) and finally the MSR (Molten Salt Reactor). Of these the HTR/VHTR and MSR in small modular reactor form are considered the most attractive option for the marine application, due to their passive safety, high burnup, high operating temperatures, and possibilities for thorium use in the future.
Criteria are established that are of importance to a marine propulsion and power generation system, establishing a framework for an implementation. Focusing on topics as: efficiency, transient loading capabilities, environmental impact, economic viability, size, and weight.
For power conversion (linking the heat generation to power/electricity for the vessel) the open-cycle Brayton turbine with a heat exchanger is selected as most suitable, despite the steam turbine being more developed and projecting a possible higher efficiency. The choice for the open-cycle Brayton turbine stems from the system size and weight reduction, along with a relatively easily implementable heat rejection system for enhanced load following capabilities. The selected heat exchanger is of the helical coil type, as this is significantly more developed and proven than the PCHE.
The most suitable layout is determined to be an all-electric layout, as this will greatly improve reliability (enhancing safety by redundant arrangements) and make the implementation easier applicable to a host of vessels. The electric layout allows for the combination of additional system such as batteries and emergency power. This layout is then combined with the open Brayton turbine and its heat rejection capabilities to ensure a system that is both compact as well as highly capable in performance.
Finally, four suitable concept vessels were established that allowed for a like-for-like replacement with a nuclear propulsion and power generation system. This allowed for a comparison to the conventional fuel-based systems where it is shown that the implementation of nuclear power can provide very large CO2eq reductions (over 98%), while reducing size and weight if vessels of suitable size are selected. The trade-off to this reduction is the production of nuclear waste, alongside the increased upfront cost due to the high capital investment associated with nuclear power.

The maritime sector plays an important role in energy transition because offshore vessels are used for building offshore renewables but also have high emissions. The European Union (EU) has determined that from 2025 the maritime sector must pay per ton of CO2 emission. Heerema Marine Contractors (HMC) is an essential player in the maritime sector and plans to have reduced its emissions by 50% by 2025. This thesis aims to build a model in which different emission-abating options can be compared on financial and technical aspects to determine the best roadmap to achieve sustainability.
To do this properly, literature research is done on emissions-abating fuels and technologies/processes applicable to offshore crane vessels. Five sub-questions are answered to find an answer to the main research question:
What will be the future energy configuration of the Heerema fleet and the most technical and financial feasible roadmap to meet the sustainability goals look like?

• What are an offshore crane vessel's main operational energy-consuming modes?

• Which fuel switches and blends are technically and financially feasible, and what are the key characteristics of these fuels?

• What are the key characteristics of the ship-based emission-abating technologies like batteries and carbon capture and storage?

• What are the current vessel-specific levelized cost of Energy (LCOE) and levelized cost of carbon abatement (LCoCA) of the fuel switches and technologies, and how are they expected to develop over time?

• Which emission-abating future scenarios are technically and financially feasible, and how will these sustainable roadmaps look?

With the evaluation of the answers to these sub-questions, the importance of using hydrotreated vegetable oil (HVO) is shown until e-fuels are available. From 2026 e-fuels are assumed to be wide available for usage on board the three vessels, the Sleipnir, Aegir and Thialf the vessels within the scope. The financial evaluation of the e-fuels is in favour of ammonia. The technical evaluation is based on the limited available storage volume favour for methanol.
These findings result in a roadmap using batteries on board the vessels together with HVO as fuel and when available installing designated ammonia or methanol tanks, and using ammonia or methanol as a 100% fuel blend in the internal combustion engines of the three vessels.

To reduce the climate change impact of shipping and retain compliance with increasingly strict emission regulations, alternative fuels are required. Methanol is expected to be one of the renewable alternatives. However, it evaporates easily compared to for example Diesel and its vapours are toxic and flammable. Regulations prescribe the use of 10m radius hazardous areas around the vent mast connected to the ship's tank. These areas pose stringent limitations on the use of a ship. In this context, knowledge is lacking on the actual risks induced by possible outflows, let alone on outflow mitigation measures. In this research an analytical thermodynamical model of a ship's methanol fuel tank is developed, it is analysed what appropriate safety measures are and what their effectiveness is.

The thermodynamical phenomena inside a ship's tank are inventoried from literature and on a selection of these a model is derived. With the model, outflow values of methanol mass with and without outflow mitigation measures are simulated for various scenarios and tank sizes. The scenarios are (1) heating during the transition from night to day or (2) due to a fire and (3) the most critical post bunker situation. The latter occurs after the ship's tank is filled for the first time prior to which no methanol vapours are present.

It is found that outflow values correspond to a hazardous area size much smaller than the prescribed 10m except for the fire scenario. However, mitigating the outflow with a PRV and with locating the tank floor in contact with the seawater is found to be very effective. With application of mitigation measures, only the most critical post bunker situation results in a hazardous area of larger than 1m, being 1.17m. Assessment of the model accuracy is limited to the presented scenarios, limiting the model applicability to the ranges in which the parameters are varied within this research.

The design space of power plants of naval surface vessels is ever expanding. As a result, the design space has become too large for a human design team to fully explore. Therefore, a concept exploration tool is introduced to generate and evaluate all possible concepts within the design space. An optimal solution is chosen based on ship characteristics and client preferences. This tool helps designers find the optimal solution and visualises the design space to enable a less constrained design methodology.

The reduction of the of harmful emissions that result fromyachting are an increasing concern and priority. It has been widely established that yachts have a significant contribution to the emission of greenhouse gasses and other emissions that are harmful to the environment and the public health. Measures must be taken that drastically reduce the environmental impact of yachts. The use of fuel cells, in combinations with alternative fuels, can provide a solution. The emission of all harmful emissions can be greatly reduced or completely eliminated. One of the major challenges in this transition is the uncertainty in the future supply of alternative fuels. Yachts are built to operate up-to 30 years, this is only possible if it is ensured of fuel supply over this time. Fuel-flexibility can provide a solution. If the operating fuel can be changed according to the availability, the yacht is guaranteed of operation in all future scenarios. This report describes research on how a fuelflexible fuel cell system can be designed that is capable op powering a super yacht. A selection of alternative fuels was made. These fuels must be suitable for marine application, they must hold environmental benefits over conventional fuels, and together they must ensure operation in all future scenarios. A number of fuels was considered. Their storage, production and feedstocks were compared. A final selection of operative fuels was made: it consists of ammonia, methanol, and bio/synthetic diesel. A fuel-flexible fuel cell system was designed based on the power demands of a yacht. The operational demands have been carefully mapped based on a yacht design of De Voogt Naval Architects. The system design is based on an SOFC with an external (pre-)reformer/cracking reactor. This reactor operates adiabatic and the required steam is supplied by water recirculation, both to increase the control over the fuel decomposition process. Waste heat is utilized in the balance of plant of the system, and can be recovered from the system in the form of a hot water flow. This heat can be consumed directly during the operation of the yacht. There are limitations in the fuel-flexibility of the system. Some of the components must be replaced when a switch between alternative fuels is made. A performance analysis is needed to find whether the fuel-flexible fuel cell system can power a yacht. A model of the system was made in which the performance of the system was simulated under the defined operational requirements. A thermodynamic analysis of the system is conducted to find the efficiencies and fuel consumption, and the heat and mass flows within the system. These parameters were used to calculate the yearly fuel consumption, emission of CO2, and required stored fuel capacity. The efficiency for the designed fuel-flexible fuel cell system is high for all of the fuels, and throughout the operation of the yacht. There is a large difference in fuel consumption and required fuel storage capacity between the alternative fuels, this is mainly caused by the energy density differences of the fuels. The emission of CO2 is depended on the fuel consumption and the carbon content of the fuels. Compared to conventional power generation and fossil fuels, the emission of CO2 is significantly reduced. There are also differences in the heat and mass flows within the system. Each fuel therefore has a different required capacity for pieces of equipment such as heat exchangers, pumps, and compressors. This research has shown how a fuel-flexible fuel cell system can be designed that is capable of powering a yacht. Through a thermodynamic model, it is shown that such a system has a high operational efficiency throughout the performance of the yacht. Harmful emissions are greatly reduced compared to conventional power generation. In a fuel-flexible system, each component must be designed for themost demanding fuel. For each fuel, some system components will therefore be over-dimensioned. A fuel-flexible system will be more complex and voluminous than a single-fuel fuel cell system. In return, the system will be operational in all future scenarios. This research has shed light on the trade-offs that the choice for a fuel-flexible fuel cell system can bring about. It provides an analysis which will only become more valuable as the yachting industry is urged to adapt to an ever-changing environment

Environmental and operational challenges associated with an excessive fuel consumption have led to the need for future naval vessels to be less dependent on fossil fuels. The chosen configuration is combined diesel-electric and diesel (CODLAD). However, there is a performance gap regarding the manoeuvrability between the previously implemented gas-turbine propulsion and the diesel-electric hybrid propulsion. In order to reduce this performance gap between a gas-turbine propulsion system and a diesel-eclectic propulsion system a new optimized control system needs to be developed.
Adaptive pitch control avoids the angle of attack peak, reducing the torque peak that can potentially overload the diesel engine. Adaptive pitch control is the only control strategy that operates at a low angle of attack, and therefore is less perceptible for cavitation. However this peak in angle of attack is responsible for the peak in thrust. Adaptive pitch control therefore needs large shaft speed fluctuations to be able to create a large thrust. Adaptive pitch control is therefore either slow or forces the diesel engine to rapidly make large changes in its shaft speed. The rapid changes in shaft speed could increase the amount of wear inside the engine, reducing the time between maintenance.
During the simulations torque control for the diesel engine performs extremely well during acceleration. Using torque control for the diesel engine the static power distribution of the propeller load was varied. During these variations it was concluded that a large acceleration can be achieved with a heavy loading on the diesel engine in steady state, supported by a large torque production during acceleration by the induction machine. A heavy matching of the diesel engine was possible because the diesel engine only produced the power needed for the steady state propeller power as matched via the combinator. The induction machine is made responsible for keeping the speed and coping with disturbances. The induction machine is inherently more suited than the diesel engine, due to its fast response as well as it being able to produce full torque or maximum power without any negative adverse effects. However torque control is not available from manufacturers.
This research includes a novel implementation of a dynamic power split, which produced very promising results. The dynamic power split uses the diesel engine with speed control parallel with the electric drive in dynamic torque control. The dynamic torque control for the induction machine allow for optimal usage of the inherent characteristics of the electrical machine. Using dynamic torque control the induction machine is responsible for the high frequency load changes such as disturbances as well as the first part of the acceleration. The diesel engine governed by a slower integral dominated PI controller accounts for the low frequency load changes, including the higher load at a new steady sate. The diesel engine with speed control parallel with the electric drive in dynamic torque control produces excellent acceleration characteristics, making it a viable option to improve the acceleration characteristics of a diesel-electric hybrid system.

The goal of this thesis is to characterise diesel-ammonia combustion using a mean value first principle approach, and to implement this characterisation of diesel-ammonia combustion in a time domain two-stroke engine model. This model will be used to indicate the technical feasibility of diesel-ammonia as a marine fuel. The main research question of this project is: How does the performance of the main engine of a deep-sea cargo vessel fuelled with diesel-ammonia compare to one fuelled by diesel only? The TU Delft engine B model is chosen to model the behaviour of an engine of an ocean going cargo vessel. The model has been adapted to simulate the behaviour of diesel-ammonia engines. The adapted model is used to compare the performance of a diesel only engine with a diesel-ammonia engine. The main conclusion from this study is that diesel-ammonia engine compared to diesel only engines have a higher specific fuel consumption because of the lower heating value of ammonia. Newly designed diesel-ammonia engines can potentially be more power dense because of stoichiometric air-fuel ratio of ammonia. However, the combustion efficiency could be a limiting factor. The diesel-ammonia engine emits significantly less CO2 and SOx emissions. However, ammonia emissions, caused by incomplete combustion, and an increase in NOx emissions, caused by the nitrogen in ammonia, are a concern. Furthermore, diesel-ammonia engines operate at lower maximum pressures and temperatures, therefore the mechanical limits of the engine are not exceeded. Lastly, diesel-ammonia engines do not require a different turbo charger system.

The use of fossil fuels and their impact on humans and nature is becoming a bigger concern worldwide. An interesting concept to lower polluting emissions coming from maritime engines is the combined use of a dual-fuel engine and an underwater exhaust system. In the dual-fuel engine natural gas is used as the main fuel type. It is seen as a cleaner alternative to the traditional fossil fuels that are being used. In order to ignite the air-gas mixture in the cylinder a small amount of diesel fuel (pilot fuel) is used, therefore making it a dual-fuel engine. Some advantages of using an underwater exhaust system are no direct emissions into the atmosphere, increased space on decks and reduced noise from the exhaust. However the downside is that such a system causes back-pressure effects which can deteriorate engine performance. So far research on these back-pressure effects on a dual-fuel type engine is lacking, therefore this thesis focuses on the static back-pressure effects on a dual-fuel engine.
For this purpose experiments were performed on a constant pressure turbocharged, 4-stroke dual-fuel engine. Engine performance and emissions were recorded for load points along the propeller and generator curve for three cases of back-pressure. The back-pressure was controlled by a butterfly valve in the exhaust pipe of the engine. Due to the fact that this butterfly valve could only be controlled manually, the back-pressure during the experiments could not be kept at a constant level. Also the engine experienced an absolute back-pressure of 1.15 bar with the valve fully open which was already quite high. And in the natural gas that was used a substantial amount of hydrogen was present. An existing diesel engine model (DE-B) that was developed at the TU Delft was then adapted to turn it into a dual-fuel engine model. It is a mean value first principle (MVFP) model. This dual-fuel MVFP model was then matched to the tested engine by using the experimental data. After the matching the model was used to test levels of back-pressure that could not be reached experimentally, due to engine limits, to see the effect on engine performance at these levels. The results were then analysed to see what the critical engine parameters are for the limits of the engine.
The experimental results showed that at low power more pilot fuel is needed to combust the gaseous fuel. It was also clear that there was a changing combustion efficiency for the gaseous fuel along the propeller curve. For the part load conditions the combustion efficiency was lower than at low or high power. For the generator curve the total efficiency was more constant, but always lower than the efficiency of the propeller curve. The results also showed that with increasing back-pressure the fuel consumption decreased for both the pilot and gaseous fuel, with the exception of the gaseous fuel flow at part load for the propeller curve. The recorded emissions showed lower levels of O2, CO and unburned hydrocarbons and higher levels of CO2 and NOx with increased back-pressure. Looking at the emissions in combination with the fuel flows, they showed signs of improved combustion efficiency with increased back-pressure. Increasing the back-pressure caused lower pressures and temperatures at the inlet side of the engine and higher pressures and temperatures at the outlet side. So for the thermal loading of the engine the outlet side is the critical one. The tested dual-fuel engine had a waste-gate installed. The model runs with higher levels of back-pressure showed that the pressure on the inlet side could become so low, that the pressure at which this waste-gate becomes active is no longer reached. This causes high pressures and temperatures before the turbine and high temperatures of the exhaust valve. The model also showed that at high levels of back-pressure the flow through the turbine becomes too low and not enough air is being put into the engine, so the air-excess ratio becomes too low, making the air-excess ratio also an important parameter for the engine limits. Finally it was shown how the dual-fuel MVFP model can be used to define acceptable limits of back-pressure for the air-excess ratio, exhaust valve and outlet receiver temperature.
The main recommendation for further research is to investigate the combustion efficiency of the gaseous fuel. Both the fact that at part load the efficiency was at it worst and the lower fuel consumption when back-pressure was increased need to be looked at. This will also help with improving the current dual-fuel MVFP model. Next to that it would be interesting to see what happens with different types of gaseous fuel and how the engine performs under a fluctuating back-pressure as induced by waves.

The constant pressure on the maritime sector to reduce Greenhouse Gas (GHG) emissions has led the shipping industry to search for alternatives, such as zero-emissions propulsion systems, which would allow meeting the 2050 target imposed by International Maritime Organization (IMO) regulation. Fuel cells have demonstrated to substantially contribute to the greening of energy conversion technologies. Specifically, Solid Oxide Fuel Cells have proven to be a reliable technology to produce energy from Liquid Natural Gas (LNG). However, the limited understanding of the effect of the components around the stack (also known as Balance of Plant, BoP) in SOFC power generation system represents one of the reasons of the slow development of this technology. The main objective of this research is to gain insight in the performance of the BoP components and their influence on the SOFC power generation system for maritime applications. A dynamic model describing a complete SOFC power generation system is developed in this work. The chosen system configuration consists of three blowers, two heat exchangers, a mixer, an external pre-reformer, an SOFC stack and an afterburner. Specifically, each BoP component is modelled dynamically using a 0-D approach and verified individually by using the software Cycle-Tempo. Then, the BoP models are integrated with an existing 1-D SOFC stack model. A dedicated control system is implemented and the load following capabilities of the complete system are studied. The model developed is able to simulate the time variation of all the BoP component characteristics and provides insights in the system efficiency when varying operating parameters such as stack current, anode recirculating ratio and fuel utilization. In particular, it is proven that working at low current enables higher cell voltage and, thus, higher system and stack efficiency. System fuel utilization significantly contributes to the system efficiency, which reaches the highest value for the highest fuel utilization. Additionally, the effect of the fuel utilization rate on the stack and system is the highest at lower currents. System and stack efficiency of respectively 58 % and 66 % are possible with the chosen system configuration. Anode recirculating contributes more to the system efficiency than the stack efficiency. The highest system efficiency is obtained for low current values and high recirculating ratio. Moreover, significant CO2 emission reduction is obtained for high recirculating ratio. The chosen control strategy succeeds on ensuring thermal safe operation, but does not guarantee fast response to load changes. In particular, a system response within 2 hours is achieved with the controller developed when the stack current is changed from 27 A to 23 A . Moreover, a load ramp of the stack current is a better choice in terms of thermal safe operation than a stepped change. The developed model represents a solid base for future development and research in the modelling of SOFC power generation systems for maritime applications. Nevertheless, future investigations on model validation, control system, start-up operations and system optimization are recommended.

The shipping industry has a notable share in global greenhouse gas emissions and other pollutants such as sulphur and nitrogen oxides. Fuel cells and batteries are identified as relatively new technologies for shipping with high potential and hydrogen is also considered as one of the most promising sustainable fuels, especially for smaller vessels. This research contributes to three identified knowledge gaps: (1) the potential of hydrogen propulsion for high-speed craft, (2) the hybridisation of fuel cells and batteries for marine applications and (3) the characteristics of the response of a hybrid fuel cell/battery propulsion system under transient loads. The objective of this research is to analyse these aspects based on a series of time domain simulations of various operational conditions.
A mathematical model of a fuel cell/battery propulsion system is developed in Matlab/Simulink. The developed model is used to analyse the energy consumption for various operational conditions of a test vessel. Based on this analysis, two configurations of fuel cell power and battery energy are selected. If the vessel sails at top speed, the fuel cell power stacks operate at maximum power and the battery operates as power booster. A strong correlation was found between the endurance at top speed and the battery size which is selected. A larger battery has a positive effect on endurance, but it also increases the displacement of the vessel significantly and, hence, required power.
Fuel cells are least responsive and these should be protected against high fluctuations in a short time. A fuel cell can only follow low-frequency transient loads. The battery is required to support in high-frequency load changes. Contrary to the fuel cell, both the battery and PMSM were found to have very favourable characteristics in transient conditions.
Finally, it is concluded that it is feasible to implement fuel cell/battery propulsion on high-speed craft. It is proposed that the fuel cell and hydrogen deliver the majority of the energy and use the battery as power booster and for transient support. Novel energy management strategies can deliver high system efficiencies in both full and part load and this is one of the main advantages of hybridisation.
The implementation of a fuel cell/battery system does, however, come at significant costs in terms of endurance and top speed due to the low volumetric energy density of hydrogen. It should be acknowledged that the functionality of the vessel is reduced. In addition to this, the storage of hydrogen requires some deck space, so the cargo capacity in terms of crew and material is also reduced. Therefore, it is recommended to redefine the user profile of the vessel.

The maritime sector faces major challenges with increasing regulations from the International Maritime Organization (IMO) and national regulations for CO2, SOx and NOx. Innovative fuel types for maritime use are now under development by various stakeholders. Methanol shows considerable potential as one of the most promising for implementation in the short to medium term, based on the potential availability, emission reduction, and energy density. The Green maritime methanol (GMM) project is Netherlands based collaboration of important stakeholders such as shipbuilders, engine manufacturers and universities. Within this project, methanol is researched as a potential alternative combustion fuel for maritime vessels. For this purpose, the ”Dutch Caterpillar engine dealer” PON Power provided a G3508A engine available as a retrofit option. The engine is a turbocharged spark-ignited natural gas (NG) engine with 8 cylinders and a rated power of 500 kWe at 1500 rpm. After six months of rebuilding the engine, the spark-ignited (SI), port fuel injected (PFI) engine runs on 100% methanol. Tests with stable engine operation were achieved with 100% methanol at 25%, 50%, and 75% engine loading and a constant engine speed of 1500 rpm.
In this research, experiments and modelling have been performed to study combustion using 100% PFI methanol. Measurements are realized with varying: ignition timings, NOx emission settings, and manifold temperatures. Data collected during these measurements such as in-cylinder pressures, emissions, and temperatures, provided a comparison between running the engine on methanol or natural gas. In this comparison combustion stability is determined with the coefficient of variation (COV) of Pmax and of imep, optimum ignition timing is determined and engine efficiency is calculated and compared to NG. Modelling is accomplished with a TU Delft model of the G3508A SI engine adjusted for the use of 100% methanol as a fuel. A modified sub-model for the PFI and vaporization of methanol has been developed. These engine data will be used to validate the methanol engine model and to optimise the engine performance for further experimental runs and better understanding the use of methanol as a fuel.
The effect on the performance and the combustion when 100% methanol is used as fuel for a SI PFI engine compared to premixed injection of natural gas is shown in this work. The engine operates stably on methanol at 50% and 75% load within ignition timings of 16-24 °CA BTDC, but less stable than with NG. Heat release indicates an almost similar combustion duration, but shorter combustion duration is shown for methanol. Also with methanol, the crank angle where 50% of fuel is burnt (CA50) is shown earlier compared to NG. The faster premixed combustion, combined with a better found fuel consumption operating point, resulted in higher efficiencies for methanol compared to NG for the tested 50% and 75% load at comparable operating conditions.

In the context of this thesis, the effect of various diesel-methanol blends in a diesel engine compared to conventional marine diesel oil is investigated by experiments and in-cylinder simulations. The main differences obtained between diesel and methanol are the lower heating value, heat of vaporization and cetane number. During the experiments, the engine was not able to run on M20 at loads lower than 153 [kW]. Pressure signal comparison between the cylinders showed that cylinder one shows better ignition properties for methanol operation compared to cylinder two, three and four. Higher COV's for IMEP and maximum pressure were obtained by methanol blends. Experiments with F76, M10 and M20 fuel have shown that methanol blends increase the specific fuel consumption and slightly decrease the engine efficiency. Specific NOx emissions decreased with 2.9 up to 14.2 [%] by methanol blends compared to F76. Due to the increased fuel consumption, the CO₂ emissions hardly reduced. Exhaust gas temperatures and CO emissions seems to decrease. The ignition delay of methanol blends increased up to 8 [degrees CA] for M20 while remaining the brake power constant. Moreover, the combustion duration and air excess ratio decreased by using methanol blends. A single droplet evaporation model is built to simulate the evaporation heat losses for methanol fuel during the in-cylinder process. Methanol has a longer evaporation time which is a disadvantage for diesel engine applications. By using the single droplet evaporation model combined with an injection model calibrated for dual fuel direct injection, the fuel spray evaporation heat is calculated for implementation in the single zone model. The results are calibrated by using the droplet diameter as a variable. In this way, the evaporation heat required for evaporation of methanol is simulated in the dual fuel single zone model. Heat release analysis shows that the premixed combustion phase of methanol blends is dominant compared to F76, while the diffusive combustion phase significantly reduces. For methanol blends, the residence time at high temperatures is lower due to the decreased combustion duration and elongated ignition delay. Unfortunately, the results from the dual fuel single zone model are strongly dependent on the position of the pressure signal. Results for the temperature of the mean cylinder two, three and four were not in line with the expectations. Cylinder one showed smoother heat release curves and its temperature result was in line with the expectations based on the exhaust gas temperature. More research to the effects of the fuel injectors on the heat release of methanol/diesel blends is recommended.

In the present study, a Model Predictive Control (MPC) - based, Energy Management Strategy (EMS) is proposed, aiming at the minimisation of the fuel consumption of vessels with hybrid propulsion and power supply. This approach is capable of utilising online information regarding realistic future predictions of the propulsive power demand, addressing the current gap in the literature regarding the implementation of MPC EMSs onboard ships, and pragmatic future mission information utilisation. To the author's best knowledge, MPC for fuel consumption minimisation has not yet been implemented at this timescale in maritime propulsion plants with hybrid power supply. Furthermore, online mission information from the Integrated Bridge Systems (IBSs) and the governor's human input cannot be utilised by EMSs onboard ships, due to the lack of a mathematical pathway to enable such an information feedback flow. Increasingly powerful processing units in ship controllers and a wider application of batteries in marine powertrains motivated such a computationally heavy and, simultaneously, highly fuel-efficient control approach. The proposed controller framework has been tested and verified in a case study using a Mean Value First Principle (MVFP) propulsion plant model of a hybrid naval vessel with batteries in Simulink®, provided by DAMEN® SNS. By using provided mission data, realistic mission profiles were generated, in which the proposed controller is validated against perfectly and piecewise, non-perfectly informed Dynamic Programming (DP) solutions in an information barrier scheme, yielding close to optimal performance, and a fuel consumption reduction of up to 3.5% when compared to any non-long-term feedback enabled controller.

Even though shipping is one of the mos fuel-efficient modes of transport, the industry was responsible for over 900 million tonnes of CO2 equivalent emissions in 2015. This is equivalent to the annual emissions of Germany. Besides greenhouse gas (GHG) emissions ships engines also cause particulate matter, NOx and noise pollution. As a result, the shipping industry is already facing strict rules and regulations, and these are expected to become even more strict in the near future. These developments have led to an increased interest in zero-emission solutions and one especially promising area is hydrogen-electric propulsion. By combining hydrogen produced from excess renewable energy with oxygen in a fuel cell, water and electricity are produced. The problem, however, is the storage method for hydrogen, traditionally hydrogen is stored in compression tanks under 300 to 700 bar. But due to the low density of hydrogen, this still results in large installations. Additionally dealing with large amounts of hydrogen gas requires extra safety precautions. An alternative way of storing hydrogen is by binding the gas to another substance like sodium borohydride or NaBH4. This substance is in a solid form and reacts with water to produce hydrogen and sodium metaborate (NaBO2). The NaBH4 crystals can be stored as a powder and are safe to handle under atmospheric conditions. Also, the substance has a high energy density, even comparable to that of conventional diesel fuel.

The maritime sector is important for the facilitation and growth of global trade. Currently, about 90% of the goods are transported by ships and as a result, the number of ships has risen, increasing the emissions related to shipping. Pollution caused by exhaust gas, especially the sulphur oxide emission, from marine diesel engines has become a global concern in recent years. Therefore, the International Maritime Organisation limited marine fuel sulphur content in both Emission Control Areas to 0.1%w/w since 2015 and globally to 0.5%w/w since January 1st , 2020. It is anticipated, that the newly implemented IMO regulations will help to mitigate negative impact of ship emissions on public health and the environment in the coastal areas. The wet scrubber system is a reliable technology for flue gas desulphurisation in marine applications and can achieve a sulphur dioxide removal efficiency of 98%. The operating costs are low, however the capital cost for installation are high and a scrubber system requires space for installation while maintaining ship’s stability. Wet scrubber systems operating in a closed loop and using caustic soda may operate without discharge to the sea and thus are allowed to operate in ports. The use of caustic soda also makes it possible to use the scrubber in areas with low seawater alkalinity. However, scrubber systems generally operate at 100%, even when the engine operates at lowload. This results in an increase of the fuel consumption and carbon dioxide emissions. Themain objectives of this research are to examine the influence of water evaporation on the sulphur dioxide removal efficiency and the (response of the scrubber) effect of dynamic loads on the scrubber efficiency. A dynamic model of a closed loop wet scrubber operating with fresh water and caustic soda also known as sodium hydroxide was created and verified. The scrubber model consists of three resistance elements, namely the venturi scrubber, the tower scrubber with a packed bed and the demister and two volume elements (lower and upper) to connect the resistance elements. The absorption of SO2 is mainly taking place in the packed bed and the two phase flow of exhaust gas and scrubbing liquid was modelled in this section. The Nerst film theory was used and extended to a two film theory in which the exhaust gas and scrubbing liquid phases come into contact through an interface and exchange both heat and mass. The gas flow in the packed bed could be modelled with a combination of resistance and volume elements as this phase is compressible. The liquid flow and liquid film thickness in the packed bed were modelled based on the conservation of mass and the liquid holdup theory developed by Billet and Schultes. A feedback control system controls the scrubbing liquid flow based on the sulphur dioxide to carbon dioxide ratio. The system includes a time constant to account for the inertia of the scrubber’s pump and pipe system. The verified model was integrated with engine data and used to run several static and dynamic simulations. The inclusion of evaporation in the packed bed leads to an increase of the scrubber efficiency in all engine loads. The extra vapour added dilutes the gas phase and reduces the mass fraction of sulphur dioxide. When evaporation is included in the analysis, the sulphur dioxide to carbon dioxide ratio leaving the scrubber is 1.88, equal to a fuel sulphur content of 0.043% on a mass base (from 3.5% in the fuel) for 100% engine load. When evaporation is not included in the analysis the previous values are 2.3 and 0.053% respectively. To increase the precision concerning the amount of water that evaporates, a higher discretisation of the packed bed is required. High engine load fluctuations and/or high input frequencies lead to overshoots and higher liquid supply, in order to keep the scrubber system efficient. In the transition from 25% MCR to 100% MCR the liquid supply exceeds the nominal value of 94 kilogram per second by by 5.3 kilogram per second (or by 5.6%). In the transition between 75%MCR to 100%MCR, for the frequency of 50 seconds the liquid supply is equal to 92.9 kilogramper second. Increasing the input frequency 5 times results in an increase of the liquid supply to 96.1 kilogram per second. The sulphur dioxide to carbon dioxide ratio leaving the scrubber was always below the ECA sulphur limit and was fluctuating around the set point, but most of the time below it. A combination of feed forward and feedback and/or a more advanced control may result in a more stable control of the scrubber, but this has to be investigated. The model functions, but more research is required for the venturi and the demister models, but also for the packed bed model. In the venturi a three phase flow is required and in the demister an analytical and dimensional analysis is required. Also, the packed bed model needs to be further developed to include the condensation effect and a more precise approach for the liquid phase. Further research can be done on the integration of the model with a diesel engine and SCR model. Also, seawater can be examined as a scrubbing liquid as this may reduce the operational costs of the scrubber. Finally, because space requirements of the scrubber are high, a structured packed bed could be an alternative to the dumped and reduce the space occupied by the wet scrubber.

To reduce the CO2 emissions of the maritime industry, several alternative fuels are being researched to possibly achieve this goal. The absence of an infrastructure for alternative fuels in the current port environment is one of the barriers towards implementation of these high potential fuels. The goal of this thesis project was to create an optimization model which can provide more insight into the initial sizing, phased growth and corresponding cost of an infrastructure needed for maritime transport using different forms of alternative fuels. The corresponding main research question is: "How do the port refueling infrastructures of sodium borohydrate, liquid hydrogen and gaseous hydrogen compare to each other with respect to costs and supply chain set-up in terms of where, when, and at what sizes to build up the production, storage, distribution and refueling facilities?" To answer this research question a single-objective multi-period mathematical optimisation model (Mixed Integer Programming) has been created for the port refueling environment. The most important model innovations are the inclusion of a maritime refueling convention and the possibility to model less conventional alternative fuels such as sodium borohydrate (NaBH4). Furthermore, input for the model has been gathered from several sources. Next, some parameters of the model have been varied to research their effect on the total alternative fuel infrastructure. As a result it has been found that the gaseous hydrogen infrastructure is the cheapest with respect to facility capital costs and facility operating costs, but was the most expensive when looking at transportation of the fuel within the port. The liquefied hydrogen was the cheapest with respect to fuel transportation, but scored average on facility capital cost. Furthermore it is the most expensive infrastructure with respect to facility operating cost. The NaBH4-infrastructure is the most expensive infrastructure when looking at the facility capital cost, but scores average on facility operating cost and transportation cost. Overall the gaseous hydrogen infrastructure was the cheapest infrastructure, followed by liquefied hydrogen. The NaBH4-infrastructure turned out to be the most expensive with the current input. The input parameters for NaBH4 are still very uncertain at this stage as the production of this fuel on a large scale is still at a low Technology Readiness Level and there is still unfamiliarity with large scale storage and transport of the substance. A reduction in the corresponding cost parameters would lead to the NaBH4-infrastructure becoming more competitive with a liquefied hydrogen infrastructure. The input used in the model should thus be further researched to reduce the corresponding uncertainties. While the current model focuses on optimising the infrastructure from a cost perspective, it must be taken into account that other factors also influence the favouring of certain alternative fuels, such as safety, policy, public acceptance and the preference for certain fuels from the perspective of the maritime users. In future research the expansion of the model towards a multi-objective model should be evaluated.

During offshore construction with a Semi-Submersible Crane Vessel (SSCV) the vessel is station keeping by means of Dynamic Positioning (DP). DP enables a vessel to keep position and heading by utilizing its own propulsion, while being exposed to the environmental forces caused by waves, wind and current. In a comparison study between offshore measurements and time-domain simulations, an increased vessel/thruster response for the offshore measurement was observed. The results revealed, that in operational environmental conditions, the measured vessel response shows increased oscillations in Surge, Sway & Yaw, with periods of approx. 3-5 min. The goal of this thesis was to determine the causes for such an increased dynamic vessel response, which are not captured in time-domain simulations. At present, numerical methods and time-domain simulations that assess the DP performance of a vessel (e.g. aNySIM) assume a quasi-static current of which the variation is only caused by the tides. One thesis is, that time-varying currents on a scale of 1 to 5 minutes can cause an increased vessel response. Furthermore, the DP System as it is used onboard is not captured in aNySIM simulations. This means that the characteristics of the DP System onboard are but not represented in full detail in time-domain simulations. Vortex Induced Motion (VIM) has previously been observed to affect multi column floaters. However, the influence on a SSCV during DP-operations has not yet been studied. In this thesis it was investigated whether the unexpected increased motions originate from time-varying currents, VIM or the DP System itself. A significant challenge was posed to find current measurement data with a small enough time step to confirm the presence of such time-varying currents. One 45 min current measurement with a sampling rate of 1Hz became available. This measurement shows that time-varying currents on a scale of 1 to 5 minutes exist and cannot be assumed to be quasi-static. More research is required to confirm their presence. However, with this limited available data it was shown that time-varying currents can cause an unexpected motion response of a SSCV during DP-operations.In order to obtain the DP System characteristics, a DP Response Amplitude Operator (RAO) assessment was conducted wherein the spring and damping terms were derived as demanded by the controller and as experienced by the vessel. This assessment showed that between 20% to 67% of the demanded critical damping is lost over the control loop of the DP System. These damping losses cause the vessel to overshoot and the damped natural period to decrease. To determine the effects of VIM, current load tests carried out on the hull of an SSCV have been investigated. It was determined that strong currents on column type floaters can cause fluctuating forces and moments that originate from vortex shedding. Further, with real-time simulations it was demonstrated, that also VIM causes an increased, previously unknown, motion response of a SSCV. Lastly, a method was developed to extrapolate the current load test results to velocities below 2kn. Subsequently, in time-domain simulations it was shown that for current velocities above 0.5kn, the vessel experienced forces and moments that caused it to fluctuate around its setpoint.

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 \textcolor{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.