Hydrogen's competitiveness as a sustainable energy carrier depends greatly on its transportation and storage costs. Liquefying hydrogen for these purposes offers benefits like purity, versatility, and higher density. However, current industrial hydrogen liquefaction processes face efficiency and cost challenges, with a second-law efficiency below 25% and costs between 2.5-3.0 US$/kgLH2, and they are mainly limited to small-scale. Scaling up liquefaction plants is a potential solution to reduce costs, but existing models often overlook the economic and technical viability of the conceptual plants. Most reported liquefaction costs rely on "ballpark" estimation, hindering process economic comparisons between various processes. Industry-sponsored studies often use confidential data, limiting accessibility. Thus, this thesis aims to develop a comprehensive framework for modelling large-scale liquefaction processes and assessing their feasibility, focusing on the large-scale high-pressure hydrogen Claude-cycle liquefier concept. The technical analysis focuses on the preliminary designs of main equipment, such as compressors, turboexpanders, and heat exchangers, ensuring compatibility with existing technology limitations. Aspen Process Economic Analyzer (APEA) is employed to estimate the capital and operating expenditure. At 0.1 €/kWh electricity price, the techno-economic assessment of the 125 tonnes per day (TPD) Claude-cycle concept yields specific liquefaction costs (SLC) of 1.55 €/kgLH2. Sensitivity analysis shows electricity price has significant influence. Applying the established design approach, incorporating high-speed centrifugal compressors could reduce the SLC by 5.42% and potentially more. Scaling up to 250 and 500 TPD shows potential SLC reductions of 7.80% and 9.45%, respectively, at electricity price of 0.1 €/kWh. Future projections suggest a potential 12.6% SLC reduction as the Claude-cycle liquefiers matures. In an ideal scenario, with incentives and low-cost renewable electricity, costs could range from 0.87 to 1.09 €/kgLH2. Finally, a cost-scaling curve for hydrogen liquefaction plants are estimated based on the cost results from this study. The curve is comparable to existing cost curves reported by industrial and government joint research projects, validating the methodologies developed in this thesis. Moreover, an experience curve is also predicted using cost data from this study and data found in the literature. The curve indicates a 17% price decrease in hydrogen liquefiers with each doubling of global liquefaction capacity.

Global warming is a topic of major concern the last decade and for reason the IMO adopted a strategy to reduce the emissions of greenhouse gasses of vessels. In order to meet the IMO requirements ships propulsion systems need to become more sustainable. An option to reduce emission is the implementation of fuel cells running on hydrogen together with batteries. Since hydrogen cannot be stored into conventional fuel tanks different fuel tank options are investigated, which led to the use of cryogenic liquid hydrogen storage tanks. During the research a case study was preformed for the Pioneering Spirit. The first step in the designing process is investigating the operational profile to get a better understanding of the projects done and the corresponding power demand and to see how the operational profile influences the power demand of the ship. After investigating the operational profile and its influence on the power demand of the ship a design methodology was written to help the user find an optimal solution for the new hybrid propulsion system. This methodology contains three parts: data importing, solution generation and new system specifications. In the first part data will be imported and processed to find the power demand during a project. Subsequently, a range of fuel cell capacities will be determine over which solutions will be generated in part two. The second part of the methodology contains three steps. During the first step solutions will be generated over the range of fuel cell capacities determined in the first part. This first step will be iterated for different battery capacities. After generating solutions in the first step in the second step suitable solutions will be defined. These solutions will be compared in the last step to find an optimal solution. For the optimal solution, the third part of the methodology will calculate the new system specifications.

Shipping is, and will continue to be, the most important transportation method around the globe. A vital part of the logistic chain, it is also one of the main contributors to the worldwide CO2 emissions. Current propulsion technologies all rely on the same classic diesel driven technology, as diesel is widely available and has a high energy density. The goal of this research is to identify greener solutions to propel a vessel sailing for short distances. During a definition study, several fuels and energy converters were studied and benchmarked based on a use case. The results showed that (a combination of) the dual fuel internal combustion, using bio diesel and hydrogen, and the low temperature proton exchange membrane fuel cell, fuelled with hydrogen, is the most feasible setup for the use case. Such a combination in itself is not a new one, but in the literature only an all-electric setup is described. In the proposed solution an internal combustion engine is driving the propellor shaft directly, assisted by an electric motor powered by the fuel cell. Based on this outcome, the following research question was defined: How can an internal combustion dual fuel engine and/or LTPEM fuel cell be integrated to form a cost effective solution to propel a short sea ship running on hydrogen? First, nine designs were created, ranging from a conventional diesel engine setup as a reference case, to a fully electric design powered by fuel cells. All main components in these designs are analyzed regarding part load efficiencies. With these efficiencies, the fuel consumption at different loads are calculated. Based on a use case scenario the total fuel costs are calculated. The CAPEX and the OPEX of the designs are determined to calculate the total costs. As currently no other fuel can compete with diesel, the designs are compared based on the price per tons of CO2 emissions, as the shipping industry is expected to see a CO2 emission penalty in the near future. For each design, what the height of this penalty has to be to reach the breakeven point at the end of the use case was calculated. Based on the lowest CO2 price, an all-electric, fuel cell powered design was identified as the most promising option. Applying additional operational arguments such as redundancy and end user acceptance, it was decided together with Conoship to choose a combination of an internal combustion engine and a fuel cell. This configuration is worked out in detail to answer the sub questions, covering efficiency improvement and system integration, during which it became apparent that not all information is available to answer all these sub questions. The design needs further research in a multidisciplinary team. A simulation model would be helpful in this further research. A framework and a start to such a model was written together with a list of recommendations.

This master's thesis addresses the urgent need to reduce the marine industry's environmental impact. Van Oord, a marine player, aims to achieve carbon neutrality by 2050. The study investigates integrating methanol-fueled Solid Oxide Fuel Cells and batteries into the cable laying vessel NEXUS's power plant. The research shows that integrating these technologies can offer acceptable operational capabilities and substantial greenhouse gas emissions reductions in the medium term. However, short-term implementation faces challenges due to current SOFC limitations. Economically, long-term fuel cost savings make this integration viable, despite high initial capital expenditure. The study includes a literature review favoring SOFCs and methanol for cable laying vessels. The case study proposes a 1926 kW SOFC and a 1195 kW battery pack integration, resulting in significant fuel consumption and emissions reductions while complying with regulations. In conclusion, integrating methanol-fueled SOFCs and batteries in cable laying operations presents an opportunity for efficiency improvement and GHG reduction, with long-term economic benefits. This supports Van Oord's commitment to carbon neutrality and addresses the marine industry's environmental challenges

The growth in the offshore wind industry sees an increased demand for offshore service vessels (OSVs). These vessels often operate in harsh conditions, and their performance is heavily dependent on their seakeeping characteristics. Conventional ship design processes fail to effectively consider seakeeping early in the design process, leading to sub-optimal vessel design. A design framework has been developed in the software 'NAPA' to efficiently design high-performing OSV concept designs. The developed framework is able to optimize a hull shape -specifically the main particulars and length of different hull sections- to maximize performance in certain objectives. These objectives are seakeeping, ship resistance, lightship weight, and station keeping power requirements. Regarding seakeeping, the attainable percentage operability is calculated for each iteration, although the Operability Robustness Index (ORI) is optimized. The ORI is a more robust seakeeping key performance indicator (KPI) than percentage operability, which is advantageous when facing concept design uncertainty. The framework maximizes ORI, thereby seakeeping performance, for a particular loading condition, motion sensitive criteria, and operational area. The ORI is evaluated based on the area of operation's scatter diagram and wave spectrum, governing motion limits, and iteration-specific RAOs. Designs are required to satisfy an initial stability constraint, to ensure feasibility. The framework's output is a Pareto-frontier showing the trade-offs between different KPIs, and the corresponding variable combinations. Thereby, the naval architect can evaluate what design offers the best overall performance. A 'feeder' OSV, designed to transport wind turbine components to wind installation vessels has been optimized to validate the framework. This OSV is currently being developed as a concept by C-Job naval architects. The ship has been optimized for maximum operability of an Ampelmann motion compensated platform. A single optimization run took three and a half hours to complete 300 iterations, thereby finding the Pareto-frontier. Comparing the Pareto-optimal solutions with the base vessel, the ORI can be increased up to 3.6%, the lightship weight decreased by 21.1% and the ship resistance decreased by 13.0%. The framework showed that smaller vessels can still attain good seakeeping performance, leading to a substantial reduction in lightship weight. The increase in seakeeping performance allows for the use of less expensive motion compensated equipment while maintaining high operability. The framework showed that there is a trade-off to be made with regard to seakeeping, and lightship weight, and ship resistance. The framework presents what variables and ship attributes cause these trade-offs. This information allows naval architects to determine the optimal design direction during concept design. Clients and naval architects can decide what trade-off in performance provides the ideal combination to achieve the ship's mission. Consequently, besides producing high-performance designs, the framework substantially increases early design knowledge. Thereby, the overall design process becomes more efficient. The framework showed to be a valuable tool for OSV concept design. By the extensive incorporation of seakeeping early in the design process, naval architects can design high-performance OSVs efficiently. The produced designs maximize performance in any of the KPIs, ensuring vessels have a high operability, but do not weigh more, or have higher fuel costs than is needed.

To support Van Oord’s path towards a low-emission future fleet, this thesis has focused on the technical, environmental and economic impact of a methanol hybrid power plant design for new-build offshore working vessels (OWVs). These Dynamic-Positioning (DP) vessels are known for their large and dynamic power plants and have to limit their NOx emissions in order to comply with IMO Tier III regulation. The research objective has been to assess the cost-effectiveness of a methanol hybrid power plant solution to reduce CO2 emissions of new-build OWVs relative to other alternative fuel options. As alternative fuels, both bio-diesel and ammonia have been selected as benchmark options. Two models have been developed to find the cost-effectiveness of the methanol and benchmark power plant solutions to reduce CO2 emissions. These models are a power plant model (PPM) and a cost assessment model (CAM). The PPM consists of an engine model, a battery model and a power management model. For a specific engine type, the engine model determines the fuel consumption and emissions performance by using available engine data. Next, based on the principle of equal energy consumption and relative fuel characteristics, these fuel consumption and emission performance are adapted in order to represent methanol or one of the benchmark fuels in the selected engine type. The battery model is established in line with DP hybrid power plant requirements and the power management model acts as a connecting link to bring the engine model and battery model together on a power level. The CAM uses the PPM output to find the relationship between costs and CO2 reduction for each power plant solution. This is done by comparing the annualized Total Costs of Ownership (TCO) and the Life-Cycle (LCA) CO2 emissions of each solution with a diesel-based configuration. In this comparison, the annualized TCO consists of the yearly operational costs and annualized investments costs of each solution. The life-cycle emissions account for both well-to-tank (WTT) and tank-to-propeller (TTP) emissions of each fuel type. A case study considering the Bravenes, a flexible fallpipe vessel within the fleet of Van Oord, has been carried out to bring the developed models into practice and to provide a solution to the research objective. The technical details of this vessel have been used to create the methanol and benchmark power plant solutions which comply with both IMO Tier III and DP regulations. Next, a representative load profile of the vessel has been applied to simulate the performance of the different power plant solution for a duration of one year. Based on these simulation results, it has been found that the methanol solution has a CO2 reduction potential up to 99% and a CO2 price of 78 euro per ton CO2 reduction. This means that methanol is most cost-effective in comparison to both the bio-diesel and ammonia power plant solutions. Relative to methanol, the battery has a similar CO2 price of 79 [euro/ton CO2], but has a CO2 reduction potential of 8.5% only. To motivate Van Oord to invest in a methanol hybrid power plant solution for new-build OWVs, external or internal incentives are required to bridge the CO2 price gap between the methanol hybrid solution and a diesel-based configuration. As external incentives, the expected CO2 tax and / or subsidy for the use of advanced fuels are particularly interesting to consider for new-build investment decision in 2021 and beyond.

The Dutch railway system is subject to maintenance, which is carried out by a group of rail contractors who need parking space to park and prepare trains in between projects. The objective of this study is to minimise the total costs as a result of the distance travelled by maintenance trains and the preservation of the included parking locations in the Dutch railway network. According to the dynamic nature and the NP-hardness of the Facility Location Problem (FLP), a Simulation-Optimisation (Sim-Opt) approach is proposed. This Sim-Opt consists of a Discrete Event Simulation (DES) and Simulated Annealing (SA) optimisation. Two neighbourhood functions are evaluated: a Random Search Algorithm (RSA) and a Utility Level Search Algorithm (ULSA), which takes the utility level of parking locations into consideration. This research shows that DES is a feasible evaluation method for finding possible solutions to the FLP in a Sim-Opt approach. The results of this evaluation show that the ULSA converges sooner than the RSA. Furthermore, the spread in best solutions across all instances is tighter when applying the ULSA. The findings indicate that the ULSA gives more robust solutions when compared to the RSA and makes the SA process more efficient. This research found that the best solutions in terms of overall cost includes on average 22 parking locations, which can reduce the maintenance cost by ~30%. The average increase in travel costs of ~9% does not justify the use of more capacity than the absolute minimum to house all trains.

The increasing awareness and urgency of climate change have led to an increase in investments and research into power sources not reliant on fossil fuels. Proton exchange membrane (PEM) fuel cells are a promising technology for automotive, maritime, and auxiliary power applications converting chemical energy into electricity. In order for this upcoming technology to compete with well-established alternatives such as diesel generators and combustion engines, it is of vital importance to improve the power density and durability. PEM fuel cells produce water and heat during operation. The presence of superfluous liquid water in the fuel cell stack gives rise to flooding of the electrodes, which hampers operation and induces degradation processes. On the other hand, it is of great importance to maintain a high membrane humidification to reduce Ohmic losses over the membranes and avoid the formation of cracks. Therefore, water management plays a vital role both in maintaining the power density and guaranteeing durability. This thesis is written under the auspices of both TU Delft and PowerCell Group, a manufacturer of PEM fuel cell systems located in Gothenburg, Sweden. Currently, a substantial amount of water condenses in the anode subsystem of PowerCell’s PEM fuel cells in certain operating ranges which subsequently enters the fuel cell stack. This study identifies the influence of certain system operating parameters on responses as the water crossover through the membranes, the relative humidity at the stack inlet, the temperature at the inlet of the stack, the condensation rate in the mixing chamber of the recirculation loop, and the mass flow rates of liquid water and water vapor in and out of the stack. Multiphysics simulation software provided by Gamma technologies is used to simulate 5600 operating points in which the system operating parameters are varied according to the Latin Hypercube sampling method. These simulations give a clear overview of the influence of the operating parameters on the aforementioned responses over the entire operating range of PowerCell’s PS-100 system. The simulated experiments are subsequently used as a basis to construct metamodels. These metamodels predict the behavior of the system based on the operating parameters varied in the 5600 simulations. The metamodels are constructed both as Krigings and as multilayer perceptrons (MLPs). Kriging is a statistical method which produces an output for a certain response based on known input data where input points which resemble the unknown point are given a greater weight. MLPs are neural networks which recognise patterns in input data and use those to predict an output for a certain response. Finally, the operating parameters are optimized using the metamodels to minimize the liquid water mass flow rate into the stack, to prevent condensation in the mixing chamber of the anode subsystem, and to target a certain inlet relative humidity of the hydrogen feed to the stack. Concluding from these optimizations it would be beneficial to preheat the hydrogen before it reaches the mixing chamber. A number of alternative designs for the anode loop are proposed which require further investigation.

Global endeavors to reduce emissions in the shipping industry are accelerating the interest in fuel cell systems. This paper explores the application of different fuel cell types (LT-PEMFC, HT-PEMFC and SOFC) in combination with different fuels (LH2, LNG,MeOH and NH3) in expedition cruise ships. An impact model is developed for the first design phase. The goal of this paper is to evaluate the impact of the combination of fuel cell system implementation and operational profile on expedition cruise vessels. Impact is expressed in ship size, capital cost, operational cost and emissions. The model takes into account: fuel storage, on-board fuel processing, fuel cell system characteristics, balance of plant components, fuel cost over operational lifetime and all onboard emissions. In the research, seven different fuel cell systems and three different hybridization strategies are considered. For the six best performing combinations of fuel cell system and hybridization strategy, the range, endurance and capacity requirements are systematically varied to determine whether the best performing option depends on these requirements. Finally, hybrid option 2 (using diesel generators to support during long transits) combined with a methanol fueled LT-PEMFC system results in the lowest newbuild price. This option does comply with emission regulations and CO2 goals for 2030. Hybrid option 2 combined with an LNG fueled LT-PEMFC system results in the lowest total cost (newbuild price and fuel cost). This option does comply with emission regulations, but does not meet CO2 goals for 2030. When it is desired to reach this CO2 target, hybrid option 2 with methanol fueled LT-PEMFC is also recommended from a total cost perspective.

The urgent need for marine transportation to reduce CO2 emissions has led to considering alternative energy and storage sources. The resulting increase in the complexity of powerplant architectures led to the development of advanced control strategies to achieve energy savings. At the same time, the health status of components has been often overlooked, leading to shortened powerplant lifecycles. To address this issue, this paper proposes a novel health-aware control strategy for hybrid and full electric powerplants featuring fuel cells and batteries that simultaneously extend service life and reduce energy consumption. Specifically, the thesis identifies the most detrimental behaviour for powerplant components and propose a bespoke cost function to mitigate those. To assess the effectiveness of the proposed control strategy, a comparative analysis will be conducted against a non-health-aware control strategie and a health aware control strategy from literature, to demonstrate the advantages of the proposed approach in terms of energy performance and service life extension, contributing to the development of sustainable marine transportation.

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

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.

In response to climate change, the marine sector is increasingly focused on the energy transition. New marine power plants operating more efficiently and on cleaner fuels are receiving significantly more attention. While the transition to different power plants and fuels results in reduced fossil fuel consumption and emissions, waste heat recovery systems can aid in obtaining both as well. Current as well as future marine power plants do not convert all of the energy contained in the fuel into useful power, with significant amounts of energy being wasted as heat. Waste heat recovery technologies can be applied to recover some of this energy and generate additional power, effectively boosting total system efficiency, with the resulting benefits of improved fuel economy and reduced specific emissions. This study first provides an extensive summary of all the different marine power plants, fuels, and waste heat recovery technologies, of both the present and future. One type of power plant that could be an advantageous alternative for future marine propulsion is the solid oxide fuel cell (SOFC) due to its high efficiency and potential to run on clean fuels. SOFCs generate electricity from chemical energy using a high-temperature electrochemical process, resulting in high-temperature waste heat being expelled. Therefore, the potential for a waste heat recovery technology to boost system efficiency is high, and it is chosen to investigate several power cycles for the waste heat recovery of a case study vessel powered by a 2 MW SOFC system. The aim of this study is to develop and execute an approach to evaluate these waste heat recovery technologies regarding their efficiency, size, and associated cost. While numerous power cycles for waste heat recovery are in existence, a selection of potentially suitable systems with a number of different setups is made to investigate further. Thermodynamic models are created for the selected power cycles to determine and compare their theoretical efficiencies. Subsequently, the size of the heat exchangers are calculated for the evaluation of system size, considering the size of other components such as turbomachinery as well. Two types of heat exchangers are considered in this study: the compact and innovative printed circuit heat exchanger (PCHE) and the classic but commonly large shell and tube heat exchanger (STHE). Finally, the investigated systems are subjected to an economic analysis based on the cost associated with the main components, with again considerations being made regarding excluded additional components. The results indicate that various configurations of the (transcritical) Rankine cycle operating on steam and CO2, as well as the (supercritical) Brayton cycle operating on CO2 and air, present with significant theoretical efficiencies ranging from 41 to 52% and electrical power outputs ranging from approximately 530 kWe to over 670 kWe. From the evaluation of the system size it is concluded that the smallest systems are those operated on CO2 equipped with PCHEs, while the largest are the air Brayton cycles equipped with STHEs. The economic analysis revealed that the systems with the lowest costs are the configurations of the (transcritical) Rankine cycle operating on steam, as well as certain air Brayton cycles equipped with PCHEs. The systems with the highest cost are found to be the air Brayton cycles equipped with STHEs, due to the significant sizes of the required heat exchangers. In general, it is concluded that no system outperforms the others simultaneously across all three investigated aspects of efficiency, size, and cost, and trade-offs will be required when selecting a waste heat recovery technology for the presented case study vessel. Nonetheless, a detailed process-oriented approach has been developed and executed to allow various waste heat recovery solutions to be compared, and it is proven that a significant amount of power can be produced from recovered waste heat. The results from this study can be directly consulted by ship owners and designers considering the application of waste heat recovery to an SOFC powered vessel. Furthermore, the developed approach can also be applied to waste heat recovery in other industries and power generation systems, as it provides a step-by-step guide on relevant calculations and considerations.

A major transition became necessary for the maritime industry to meet the IMO’s targets for mitigating the carbon footprint of the sector by at least 50% by 2050. One of the promising methods to lower the emissions is the ship's hybridization. An enormous increase in pilot and demonstration projects for that purpose is being observed. This research was contacted through the involvement of TU Delft in such a project called the Implementation of Ship Hybridisation. The design and optimization of hybrid propulsion systems is a complex and challenging task due to the different power sources involved and the dependence on the energy management and control. The physical system and the control algorithm should be designed in an integrated manner to obtain an optimal system design. This study applies a multi-objective double-layer optimization methodology to optimize the sizing and energy management of a hybrid ship propulsion system to be installed on a Crew transfer vessel. A proposed hybrid topology which combines diesel engines, batteries and fuel cells is considered. The proposed approach incorporates the development of fuels and electricity prices as well as the investment costs of the system’s components as an uncertainty element. The introduction of emission reduction measures such as carbon tax was also considered in the study. Future trajectories for the relevant uncertainties were developed and incorporated in the optimization methodology to provide decision-makers with a more realistic picture of the solution space. The analysis of the optimization results was based on the Total cost of ownership (TCO) and the emission reduction potential of the optimal designs produced by the optimization methodology. The results show that instead of choosing a hybrid propulsion system for the vessel under study, an all-electric propulsion system which is based entirely on batteries and fuel cells is the most economical and environmentally friendly option. Incorporating diesel engines has a negative impact on the operational expenditures of the system in the long term. A fully electric propulsion system would require a larger initial investment from the ship owner, but it would pay off over the course of the ship’s remaining useful life. This research can be used as a reference to base the decision of the stakeholders on choosing a new propulsive system for their vessel. The parameters of the optimization methodology can be easily changed to explore more options and expand the design solution space if this thesis’ results don’t satisfy the shipowner. In addition, it is suggested that a professional user interface designer be involved in the development of a real life decision support tool, incorporating the multi-objective optimization methodology.

In order to meet the shipping industry's emissions reduction goals, it is imperative to explore and adopt alternative marine fuels. Methanol (or methyl alcohol) is expected to play a large role in the future. However, current regulations limit the attractiveness of methanol as marine fuel due to the inability to use the space around a venting point on deck. Hazardous area zones are installed around fuel tank vapour outlets due to the flammability and toxicity of methanol vapour. Consequently, these areas become very impractical. This thesis investigates the ventilation of the fuel tank vapour below the waterline instead on deck in order to be able to limit/eliminate these areas. Therefore, the main research question is: "What is the concentration of methanol at deck level when methanol is vented below the waterline?" An Eulerian based CFD model and a simple integral model are used to predict the methanol concentration above the waterline. The integral model predicts the gas concentration above the waterline based on the gas flow rate reaching the surface and the radial inflow rate of air. The CFD model tracks parcels (group of bubbles with the same properties) using the force balance in the discrete phase model. Both of the models are successfully validated against experimental data from the "Rotvoll experiment" wherein methane was released at the bottom of a water basin. The CFD model showed strong superiority over the integral model, o.a. due to the lack of gas dissolution in the integral model. The numerical models are applied to the case wherein a mixture of methanol and nitrogen is vented due to an overpressure. The overpressure could be caused by for example the failure of the vapour return line when bunkering or a fire. The bunker tanks are protected by a pressure relief valve, which reduces the overpressure by directing the gases in the bunker tank towards the venting location below the waterline. The flow rate characteristic (pressure - flow rate) of the pressure relief valve determines the rate at which the gases are injected in the water. The gas dissolution showed strong dependence on the departure bubble diameter and the venting depth. Different cases with different initial bubble sizes and different venting depths were simulated. The CFD model showed that in the most critical case (lowest venting depth 0.5m and largest initial bubble size 0.08m) the gas dissolution is large enough such that no methanol vapour reaches the deck of the ship and barge. The subsea venting of methanol-nitrogen vapour proved to be a safe alternative compared to the venting above deck.

The concept of coproduction has been explored in combined heat and power applications. It is a method of improving the efficiency of the energy generating system by utilising waste heat. In the coming years hydrogen is expected to play an important role in decarbonization as it does not emit greenhouse gas at the point of application. Hydrogen today is primarily generated from fossil fuels and the processes of producing hydrogen are energy intensive, while also emitting large quantities of greenhouse gases into the atmosphere. As the amount of hydrogen generated today is limited, it has restricted the growth of industries such as the automobile industries producing fuel cell vehicles that are to use hydrogen as fuel. In this thesis report a coproduction concept using high temperature molten carbonate fuel cell has been examined. The molten carbonate fuel cells operate at very high temperature, and it is possible to utilise the waste heat for internal reforming reaction of a fuel such as natural gas to liberate hydrogen required by the fuel cell. Excess hydrogen can also be produced from such fuel cell systems when the fuel utilisation in the fuel cell is reduced. This concept has been studied with solid oxide fuel cells and a paper published in 2008 by Hemmes et al. titled "Flexible Coproduction of Hydrogen and Power Using Internal Reforming Solid Oxide Fuel Cells System" has served as the inspiration for this thesis report. Three modes of operations have been simulated in this thesis on the Cycle-Tempo software with varying fuel utilisations, similar to what has been shown with the solid oxide fuel cells in that paper. With molten carbonate fuel cells, overall efficiency of up to 80% was obtained in terms of electricity and hydrogen coproduction. By doing so it is also possible to produce overall power output of nearly three times than what can be achieved by conventional electricity production. The results obtained have also been compared with the solid oxide fuel cells in this report. While high coproduction efficiencies for flexibly coproducing hydrogen and power have been shown to be possible, other factors would also play important roles in the success of this technology. In this report some of those factors such as the status and expected growth of the hydrogen market, molten carbonate fuel cell market, role of actors, role of policy makers have also been examined. As this technology does rely on a fossil fuel that is natural gas, the benefits of using natural gas in hydrogen production has also been highlighted along with the positive effects these systems could have on the society.

This report will give an in depth view on the technical feasibility of placing an offshore platform from which watersports can be practiced in the waters surrounding the island of Bonaire. The feasibility research is done by appointment of two entrepreneurs on the island of Bonaire. The report will give an answer to the research question: Can an offshore floating platform, aimed at fast watersports, be built as sustainable as possible within the context of Bonaire? This research question can be divided into multiple sub-questions, being: 1. What is the context of Bonaire? 2. What is, for this report, the definition of sustainability? 3. What facilities are needed on the platform? 4. How can 100% renewable energy be generated for the platform? 5. What would such a (conceptual) platform look like? To answer these questions, the method as described in Kossiakoff (2011) is used. This method gives structure to the design of a system that has not been used before, but tries to combine older systems in new innovative ways. From this method, three important stages in the design process have been identified: The needs analyses, the concept exploration and the concept definition. This report follows that structure, starting with the chapter: Needs analyses. In this chapter, the report answers the first two sub-questions. The context of Bonaire can be described as: an island with opportunities for every-one, but the local environment suffers from the exponential growth of people and tourists that visit the island. For the second sub-question the definition of sustainability has been placed within this context of Bonaire, leading to a specialized definition of sustainability. This definition combined with the requirements of the clients has lead to a valid need for the platform. The concept exploration, gives options to answer those needs. It does so by researching a broad range of possible facilities for the platform. This broad research eventually leads to a morphological map from which 3 realistic and 1 futuristic concepts are designed. In the concept definition these 3 realistic concepts have been tested by an MCA resulting in one concept that has been worked out for various components, thus answering sub question 5. From this worked out concept, a conclusion is written in where the main conclusion is that an offshore platform aimed at fast water sports van be build sustainable within the context of Bonaire if the clients are able to make some consensus in there plans and the way they will use the platform. Finally, considering the sustainability of the proposed platform, it can be concluded with current technologies it is hard to build a platform without emissions, negative effects or any hidden impact. However, if the schedule and plans of the clients where to change towards a more ’nature dependent’ schedule (so taking peak energy generation into account). The platform could set an example and can even be a global ’first’ when it comes to making the practice of watersports more sustainable.

Hydrogen Polymer Electrolyte Membrane (PEM) fuel cell technology is becoming increasingly popular in the transportation sector, especially the automotive industry. It can power electric drives by converting hydrogen into electricity in a chemical reaction with oxygen, whose products consist only of water. Therefore, hydrogen PEM fuel cell-based powertrains are free of any harmful emissions, enabling clean propulsion technology. An important part of an automotive fuel cell system is the air processing subsystem, which usually features an electrical air compressor (E-compressor) to supply the necessary oxygen for the chemical reaction. This E-compressor can absorb between 10-30% of the fuel cell gross power. One way to decrease this share is to expand the fuel cell air exhaust flow in a turbine that contributes to power the E-compressor, essentially realizing an electric turbocharger (E-turbocharger). E-turbochargers for fuel cells are still in the development phase, therefore there is a lack of experience and knowledge on their benefit. In this thesis, a model of an existing automotive PEM fuel cell air processing system has been developed using the AVL Cruise M software. In addition, two prototype PEM fuel cell E-turbochargers (ETC1 and ETC2, respectively) have been modeled and integrated into the main air processing system model. Steady-state simulations have been performed for three different power levels. Moreover, the turbine inlet temperature of the ETC1-based model was varied in the range of 60°C to 150°C to quantify what benefits exhaust heating with waste heat brings in addition to the inherent turbocharging performance gains. The results show that compared to the baseline system, the model featuring ETC1 achieved an increase in net power between 3.04-6.78% or a decrease in fuel consumption between 3.19- 7.67%, depending on the power level. For the ETC2-based model, from low to high load, the net power increased between 1.88-2.04%, or fuel consumption decreased between 2.07-3.17% compared to the baseline system. When increasing the turbine inlet temperature to 150°C, the model showed an additional decrease in fuel consumption of 2.1 percentage points at full power. The models could be improved by implementing a first-principle-based model of the E-compressor and E-turbocharger, which could have been developed in this project if more detailed information on the heat flows within these components was available.

Hydrogen Polymer Electrolyte Membrane (PEM) fuel cell technology is becoming increasingly popular in the transportation sector, especially the automotive industry. It can power electric drives by converting hydrogen into electricity in a chemical reaction with oxygen, whose products consist only of water. Therefore, hydrogen PEM fuel cell-based powertrains are free of any harmful emissions, enabling clean propulsion technology. An important part of an automotive fuel cell system is the air processing subsystem, which usually features an electrical air compressor (E-compressor) to supply the necessary oxygen for the chemical reaction. This E-compressor can absorb between 10-30% of the fuel cell gross power. One way to decrease this share is to expand the fuel cell air exhaust flow in a turbine that contributes to power the E-compressor, essentially realizing an electric turbocharger (E-turbocharger). E-turbochargers for fuel cells are still in the development phase, therefore there is a lack of experience and knowledge on their benefit. In this thesis, a model of an existing automotive PEM fuel cell air processing system has been developed using the AVL Cruise M software. In addition, two prototype PEM fuel cell E-turbochargers (ETC1 and ETC2, respectively) have been modeled and integrated into the main air processing system model. Steady-state simulations have been performed for three different power levels. Moreover, the turbine inlet temperature of the ETC1-based model was varied in the range of 60°C to 150°C to quantify what benefits exhaust heating with waste heat brings in addition to the inherent turbocharging performance gains. The results show that compared to the baseline system, the model featuring ETC1 achieved an increase in net power between 3.04-6.78% or a decrease in fuel consumption between 3.19- 7.67%, depending on the power level. For the ETC2-based model, from low to high load, the net power increased between 1.88-2.04%, or fuel consumption decreased between 2.07-3.17% compared to the baseline system. When increasing the turbine inlet temperature to 150°C, the model showed an additional decrease in fuel consumption of 2.1 percentage points at full power. The models could be improved by implementing a first-principle-based model of the E-compressor and E-turbocharger, which could have been developed in this project if more detailed information on the heat flows within these components was available.