The marine industry must reduce emissions to comply with recent and future regulations. Solid oxide fuel cells (SOFCs) are seen as a promising option for efficient power generation on ships with reduced emissions. However, it is unclear how the devices can be integrated and how this affects the operation of the ship economically and environmentally. This paper reviews studies that consider SOFC for marine applications. First, this article discusses noteworthy developments in SOFC systems, including power plant options and fuel possibilities. Next, it presents the design drivers for a marine power plant and explores how an SOFC system performs. Hereafter, the possibilities for integrating the SOFC system with the ship are examined, also considering economic and environmental impact. The review shows unexplored potential to successfully integrate SOFC with thermal and electrical systems in marine vessels. Additionally, it is identified that there are still possibilities to improve marine SOFC systems, for which a holistic approach is needed for design at cell, stack, module, and system level. Nevertheless, it is expected that hybridisation is needed for a technically and economically feasible ship. Despite its high cost, SOFC systems could significantly reduce GHG, NOX, SOX, PM, and noise emissions in shipping.@en

Solid Oxide Fuel Cell (SOFC) systems have the potential to reduce emissions from seagoing vessels. However, it is unknown whether ship motions influence the system's operation. In this research, a 1.5 kW SOFC module is operated on an inclination platform that emulates ship motions, to evaluate the influence of static and dynamic inclinations on the system's safety, operation, and lifetime. The test campaign consists of a static inclination test, a dynamic test, a degradation test, and a high acceleration test. There were no interruptions in the power supply during the different tests, and no detectable gas leakages or safety hazards. Although the SOFC does not fail in any test condition, dynamic inclinations result in forced oscillations in the fuel regulation, which propagate through the system by different feedback loops in the control architecture, leading to significant deviations in the operational parameters of the system. Additionally, for motion periods from 16 to 26 s, reoccurring exceedance of the fuel utilisation results in a gradual reduction of the power supply. Several enhancements are recommended to improve the design of SOFCs and marine fuel cell regulations to ensure their safe operation on ships.

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An increasing demand in the marine industry to reduce emissions led to investigations into more efficient power conversion using fuels with sustainable production pathways. Solid Oxide Fuel Cells (SOFCs) are under consideration for long-range shipping, because of its high efficiency, low pollutant emissions, and fuel flexibility. SOFC systems also have great potential to cater for the heat demand in ships, but the heat integration is not often considered when assessing its feasibility. This study evaluates the electrical and heat efficiency of a 100 kW SOFC system for marine applications fuelled with methane, methanol, diesel, ammonia, or hydrogen. In addition, cathode off-gas recirculation (COGR) is investigated to tackle low oxygen utilisation and thus improve heat regeneration. The software Cycle Tempo is used to simulate the power plant, which uses a 1D model for the SOFCs. At nominal conditions, the highest net electrical efficiency (LHV) was found for methane (58.1%), followed by diesel (57.6%), and ammonia (55.1%). The highest heat efficiency was found for ammonia (27.4%), followed by hydrogen (25.6%). COGR resulted in similar electrical efficiencies, but increased the heat efficiency by 11.9% to 105.0% for the different fuels. The model was verified with a sensitivity analysis and validated by comparison with similar studies. It is concluded that COGR is a promising method to increase the heat efficiency of marine SOFC systems.

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Marine actors are showing an increased interest in the application of Solid Oxide Fuel Cells (SOFCs) for deep sea shipping, because of their high conversion efficiency, low pollutant emissions, and fuel flexibility. However, it is unknown how the operation of SOFC systems is affected by large inclinations and motions, which can be present in ships for instance by seawaves. The goal of this research is to evaluate the influence of static and dynamic inclinations on the operation and safety of SOFC systems. Ship motions are emulated using a one-axial oscillation platform up to 30 degrees of inclination. The SOFC system was successfully operated on the platform and demonstrated stable power production under a variety of test conditions without any noticeable safety hazards. The results of the experiments are used to propose design improvements for marine SOFC systems, ultimately contributing to reduce the emissions of the shipping industry.@en

To continue its operations, the marine industry needs to comply with emission regulations. Solid Oxide Fuel Cells (SOFCs) are considered a promising solution, since it can generate energy athigh efficiency and low NOX, SOX and particulate matter emissions. Another advantage of SOFCsis fuel flexibility, meaning several fuels can be applied in SOFC systems. This brings up the question which fuel is most effective for a marine SOFC system. In this research, marine gas oil (benchmark), liquefied hydrogen, biodiesel, Fischer-Tropsch diesel, natural gas, methanol, dimethyl ether, and hydrogenare compared as bunker fuel. A comparison framework is proposed specialised for marine applications. The following decision criteria are selected: production capacity, volumetric/ gravimetric energy density, technological readiness, safety, fuel cost, cost of the fuel storage system, and emissions. The performance indicators are quantified for every fuel based on literature and supplier information.In the end, five alternative fuels are selected for marine SOFC systems on the selected criteria, which wille be used in further research.@en

With the demand for anticipated green hydrogen and power production, novel and upgraded catalytic processes are desired for more effective utilization of precious natural resources. Methane steam reforming is an advanced and matured technology for converting methane to hydrogen and syngas. As a renewable energy resource containing a large amount of methane, biogas is a promising fuel for green hydrogen production. Because of the fuel flexibility and high efficiency relative to alternative technologies, solid oxide fuel cells with internal methane reforming capabilities may become an economically viable technology for hydrogen and power generation. A renewed interest in the flexible application of biogas in solid oxide fuel cells for the co-generation of green hydrogen and power has emerged recently, driven by the spectacular advances in fuel cell technology. However, the methane reforming process suffers from inaccurate or unprecise descriptions. Knowledge of the factors influencing the reforming reaction rate on the novel and improved reforming anode catalysts in solid oxide fuel cells are still required to design and operate such systems. Therefore, a comprehensive review of recent advances in methane steam reforming provides meaningful insight into technological progress. Herein, major descriptors of the methane steam reforming reaction engineering are reviewed to provide a practical perspective for the direct application of biogas in solid oxide fuel cells, which serves as an alternative sustainable, flexible process for green hydrogen and power co-production. Current advances and challenges are evaluated, and perspectives for future work are discussed.

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This paper gives an overview of research that was carried out with the purpose of gaining insight whether renewable methanol, fuel cells and on-board carbon capture can be used to reduce the CO2 emissions of part of a fleet consisting of various (governmental) work ships, using methanol produced from waste biomass, excess wind energy and recycled CO2. Since CO2 is a by-product from steam reforming methanol to hydrogen, this can be captured, liquefied, and stored on board for later use in methanol production. Integrating the necessary systems seemed possible for larger ships using dimensions of currently available systems, although suitable carbon capture systems are not yet available. Using system parameters and operational profile as input, a MATLAB-Simulink model was constructed to calculate the tank-to-propeller emissions, as well as providing insight in required tank dimensions (both methanol and CO2). In general, the total energy stored on board of larger ships is reduced when using methanol instead of traditional fuel oils, but the reviewed ships are still able to achieve their original operational profile. Smaller vessels require various advancements in order to fit the required systems whilst still being able to store enough fuel for at least a single trip. These advancements can include more compact reformer and fuel cell systems, or class rule changes regarding the dimensions of cofferdams that are to be fitted around methanol tanks. Assuming these advancements are possible in the near future, the total emissions could be reduced significantly, by up to 82% in the originally reviewed case. This means that the net CO2 emissions are still positive and subsequently a gap in CO2 supply for methanol production occurs. However, both problems can be tackled simultaneously with further advancements: either by capturing more CO2 during the various well-to-propeller stages, or by introducing an additional carbon-negative CO2 source. It could therefore be possible to operate a fleet with net zero CO2 emissions in the future by using renewable methanol, fuel cells and on-board carbon capture, if feedstock availability is high enough and technological advancements are made.@en

The maritime industry is actively exploring alternative fuels and drive train technology to reduce the emissions of hazardous air pollutants and greenhouse gases. High temperature solid oxide fuel cells (SOFCs) represent a promising technology to generate electric power on ships from a variety of renewable fuels with high efficiencies and no hazardous emissions. However, application in ships is still impeded by a number of challenges, such as low power density and high capital cost. A slow response to load transients is another challenges, which is typically a result of the conservative thermal management strategies used to ensure that excessive thermal stresses in the stack are avoided. Therefore, a reduced order SOFC stack model is developed in this work for model-based control. The model is subsequently verified with a high fidelity model developed in previous work. In addition, a preliminary framework for its use for model predictive SOFC control is provided. The reduced order model and control framework will be used in future work to optimise thermal management of SOFC stacks for improved transient response while respecting physical and operational constraints.@en

As shipping is setting sail for a sustainable future, the application of fuel cells is increasingly regarded as a promising technology to reduce or fully eliminate emissions. Fuel cells convert the chemical energy in fuels directly into electricity, achieving high efficiencies while emitting no hazardous compounds and producing little noise and vibrations. This chapter provides an overview of different fuel cell systems and discusses the various fuel cell types, working principles and characteristics. Particular attention is given to the low and high temperature polymer electrolyte membrane fuel cell and solid oxide fuel cell, as these are often considered to hold most potential for application in ships. The application of fuel cells is not restricted to the use of pure hydrogen, thus an overview of relevant fuel processing and purification technologies is provided as well. Operational aspects including electrical efficiency, part load performance, load transients, system start-up, heat recovery and combined cycle operation are introduced and subsequently discussed in the context of maritime application. Aspects related to ship design and operation, emission regulation compliance, reliability, availability, maintenance, safety and economics are briefly considered. Finally, an overview of relevant maritime experience and a future outlook are provided.

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The shipping industry is facing increasing demands to reduce its environmental footprints. This has resulted in adoption of new and more environmental friendly power sources and fuels for on-board power generation. One of these novel power sources is the Solid Oxide Fuel Cell (SOFC) which has a great potential to act as a power source, thanks to its high efficiency and capability to handle a wide variety of fuel types. However, SOFCs suffer from low transient capabilities and therefore have never been considered to be used as the main power source for maritime applications. In this paper, novel component sizing, energy and power management approaches are proposed to enable the use of SOFCs as the main on-board power source for the first time in the literature and integrate them into the liquefied natural gas fueled Power and Propulsion System (PPS) of vessels. The proposed component sizing approach determines the power ratings of the on-board sources (SOFC, gas engine and battery) considering size and weight limits, while the energy and power management approaches guarantee an optimal power split between different power sources and PPS stability while looking after battery aging. The results indicate that the combined proposed optimization-based approaches can yield up to 53% CO₂ reduction and 21% higher fuel utilization efficiency compared to conventional diesel-electric vessels.

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The current literature on solid oxide fuel cell and internal combustion engine (SOFC-ICE) integration is focused on the application of advanced combustion technologies operating as bottoming cycles to generate a small load share. This integration approach can pose challenges for ships such as restricted dynamic capabilities and large space and weight requirements. Furthermore, the potential of SOFC-ICE integration for marine power generation has not been explored. Consequently, the current work proposes a novel approach of SOFC-ICE integration for maritime applications, which allows for high-efficiency power generation while the SOFC anode-off gas (AOG) is blended with natural gas (NG) and combusted in a marine spark-ignited (SI) engine for combined power generation. The objective of this paper is to investigate the potential of the proposed SOFC-ICE integration approach with respect to system efficiency, emissions, load sharing, space and weight considerations and load response. In this work, a verified zero-dimensional (0-D) SOFC model, engine experiments and a validated AOG-NG mean value engine model is used. The study found that the SOFC-ICE integration, with a 67–33 power split at 750 kWe power output, yielded the highest efficiency improvement of 8.3% over a conventional marine natural gas engine. Simulation results showed that promising improvements in efficiency of 5.2%, UHC and NOx reductions of about 30% and CO₂ reductions of about 12% can be achieved from a 33–67 SOFC-ICE power split with comparatively much smaller increments in size and weight of 1.7 times. Furthermore, the study concluded that in the proposed SOFC-ICE system for maritime applications, a power split that favours the ICE would significantly improve the dynamic capabilities of the combined system and that the possible sudden and large load changes can be met by the ICE.

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For decades, ships have been propelled by diesel engines. However, there are increasing concerns about their environmental impact. Fuel cells can provide an alternative to convert fuels directly into electricity, with high efficiencies and without hazardous emissions. Solid oxide fuel cells have a ceramic membrane, which functions at high temperatures. This makes them less prone to contamination, allows internal conversion of various fuels and enables integration with thermal cycles to achieve high combined efficiencies. So are ships and solid oxide fuel cells a match made in heaven? This dissertation breaks ground on the challenges and opportunities regarding the application of solid oxide fuel cells in ships, internal fuel reforming and integration with thermal cycles. How do solid oxide fuel cells compare to other power plants? How can we compare different system integration options? Does internal fuel reforming affect the efficiency and lifetime? Can cell experiments provide useful information on overall system performance? These are among the questions addressed in this dissertation. The reader will learn how solid oxide fuel cell integration with reforming and thermal cycles can provide power on ships with high efficiency and reliability, no pollutant emissions and low noise, but also about the challenges and opportunities of this potentially budding love.@en

Various concepts have been proposed to use hydrocarbon fuels in solid oxide fuel cell (SOFC) systems. A combination of either allothermal or adiabatic pre-reforming and water recirculation (WR) or anode off-gas recirculation (AOGR) is commonly used to convert the fuel into a hydrogen rich mixture before it is electrochemically oxidised in the SOFC. However, it is unclear how these reforming concepts affect the electrochemistry and temperature gradients in the SOFC stack. In this study, four reforming concepts based on either allothermal or adiabatic pre-reforming and either WR or AOGR are modelled on both stack and system level. The electrochemistry and temperature gradients in the stack are simulated with a one-dimensional SOFC model, and the results are used to calculate the corresponding system efficiencies. The highest system efficiencies are obtained with allothermal pre-reforming and WR. Adiabatic pre-reforming and AOGR result in a higher degree of internal reforming, which reduces the cell voltage compared to allothermal pre-reforming and WR. Although this lowers the stack efficiency, higher degrees of internal reforming reduce the power consumption by the cathode air blower as well, leading to higher system efficiencies in some cases. This illustrates that both stack and system operation need to be considered to design an efficient SOFC system and predict potentially deteriorating temperature gradients in the stack.

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Direct internal reforming in solid oxide fuel cells (SOFCs) is advantageous as it enables to heat and steam from the exothermic hydrogen oxidation reaction in the endothermic steam reforming reaction. However, it may increase potentially deteriorating temperature gradients as well. The temperature and concentration profiles can be accurately simulated with adequate SOFC models and intrinsic methane steam reforming (MSR) kinetics. Therefore, this study aims to derive intrinsic MSR kinetics suitable for control-oriented dynamic SOFC models. The individual influences of the methane, steam and hydrogen partial pressures on the MSR reaction are experimentally studied on functional electrolyte supported cells with nickel-gadolinium doped cerium anodes. A non-proportional dependence of the MSR rate on the methane partial pressure and a slight negative dependence on the steam partial pressure are observed, but the effect of the hydrogen partial pressure seems insignificant. Various kinetic rate equations are parameterised with the experimental data and an ideal plug flow reactor model. An intrinsic Langmuir-Hinshelwood mechanism for a rate determining step between associatively adsorbed methane and dissociatively adsorbed steam on the catalyst surface shows good agreement with the experimental data, and is thermodynamically and physically consistent.

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Direct internal reforming enables optimal heat integration and reduced complexity in solid oxide fuel cell (SOFC)systems, but thermal stresses induced by the increased temperature gradients may inflict damage to the stack. Therefore, the development of adequate control strategies requires models that can accurately predict the temperature profiles in the stack. A 1D dynamic modelling platform is developed in this study, and used to simulate SOFCs in both single cell and stack configurations. The single cell model is used to validate power law and Hougen-Watson reforming kinetics derived from experiments in previous work. The stack model, based on the same type of cells, accounts for heat transfer in the inactive area and to the environment, and is validated with data reported by the manufacturer. The reforming kinetics are then implemented in the stack model to simulate operation with direct internal reforming. Although there are differences between the temperature profiles predicted by the two kinetic models, both are more realistic than assuming chemical equilibrium. The results highlight the need to identify rate limiting steps for the reforming and hydrogen oxidation reactions on anodes of functional SOFC assemblies. The modelling approach can be used to study off-design conditions, transient operation and system integration, as well as to develop adequate energy management and control strategies.

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Solid oxide fuel cell (SOFC) technology offers a clean and efficient way to generate electricity from natural gas. Since various integration options with thermal cycles have been proposed to achieve even higher electrical efficiencies, it is interesting to see how these compare. In addition, the influence of the SOFC operating parameters on thermal cycles is not yet adequately addressed. In this study, a stand-alone SOFC system is thermodynamically analysed and compared to configurations combined with a gas turbine or steam turbine, as well as a novel SOFC-reciprocating engine combined cycle system. The results are mapped in contour plots for the entire SOFC operating envelope, revealing the influence of fuel utilisation, cell voltage, average stack temperature and gas turbine pressure ratio on different combined cycles. An exergy analysis is included to quantify notable losses in the systems and identify potential further improvements. The pressurised SOFC-gas turbine combined cycle achieves the highest electrical efficiencies for stack operation at moderate cell voltages and high temperatures, while the steam turbine combined cycle is more efficient at high cell voltages and low stack temperatures. The SOFC-reciprocating engine combined cycle shows similar behaviour to the steam turbine combined cycle, but achieves slightly lower efficiencies.

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Computational fluid dynamics (CFD) models can be used to optimize operational conditions for safe and stable operation of direct internal reforming solid oxide fuel cells (SOFCs), but require an appropriate description of the reforming kinetics on the anode. A CFD model, representing a single channel in a single cell test station is developed in this study. Data from previous methane steam reforming experiments on single cells is used to parameterize two kinetic models, one of the power law and one of the Langmuir-Hinshelwood type, using an ideal plug flow reactor model. Both rate equations are implemented in the CFD model and used to simulate the experimental conditions. Although the model shows good statistical agreement with the experimental data for both rate equations, different spatial distributions of reaction rates, species concentrations and temperature are predicted.

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Major operating challenges remain to safely operate methane fuelled solid oxide fuel cells due to undesirable temperature gradients across the porous anode and carbon deposition. This article presents an experimental study on methane steam reforming (MSR) global kinetics for single operating SOFCs with Ni-GDC (gadolinium doped ceria) anodes for low steam to carbon (S/C) ratios and moderate current densities. The study points out the hitherto insufficient research on MSR global and intrinsic kinetics for operating SOFCs with complete Ni-ceria anodes. Further, it emphasizes the need to develop readily applicable global kinetic models as a subsequent step from previously reported state-of-art and complex intrinsic models. Two rate expressions of the Power law (PL) and Langmuir-Hinshelwood (LH) type have been compared and based on the analysis, limitations of using previously proposed rate expressions for Ni catalytic beds to study MSR kinetics for complete cermet anodes have been identified. Firstly, it has been shown that methane reforming on metallic (Ni) current collectors may not be always negligible, contrary to literature reports. Both PL and LH kinetic models predict significantly different local MSR reaction rate and species partial pressure distributions along the normalized reactor length, indicating a strong need for further experimental verifications.

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Progressing limits on pollutant emissions oblige ship owners to reduce the environmental impact of their operations. Fuel cells may provide a suitable solution, since they are fuel efficient while they emit few hazardous compounds. Various choices can be made with regard to the type of fuel cell system and logistic fuel, and it is unclear which have the best prospects for maritime application. An overview of fuel cell types and fuel processing equipment is presented, and maritime fuel cell application is reviewed with regard to efficiency, gravimetric and volumetric density, dynamic behaviour, environmental impact, safety and economics. It is shown that low temperature fuel cells using liquefied hydrogen provide a compact solution for ships with a refuelling interval up to a tens of hours, but may result in total system sizes up to five times larger than high temperature fuel cells and more energy dense fuels for vessels with longer mission requirements. The expanding infrastructure of liquefied natural gas and development state of natural gas-fuelled fuel cell systems can facilitate the introduction of gaseous fuels and fuel cells on ships. Fuel cell combined cycles, hybridisation with auxiliary electricity storage systems and redundancy improvements are identified as topics for further study.

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