Low-Temperature Polymer Electrolyte Membrane Fuel Cells (LT-PEMFCs) have recently emerged as a promising solution for sustainable ship energy systems. However, enhancing durability is essential to enable their broader adoption in the maritime sector. Durability enhancement depends on a thorough understanding of degradation mechanisms and accurate prognostics, both of which are highly application-specific. The current literature lacks a comprehensive understanding of LT-PEMFC degradation under maritime operating conditions and its integration into reliable prognostic models. To address this gap, this review provides an overview of LT-PEMFC durability and prognostic models from the perspective of maritime applications. Through a comparative analysis of studies across various sectors, we identify and discuss maritime-specific degradation drivers, including ship load profiles, sodium chloride contamination, vibrations, and wave-induced inclinations. Building on this analysis, we critically evaluate existing prognostic models and their suitability for lifetime prediction in maritime applications. This review proposes durability enhancement strategies based on current knowledge and highlights key research gaps requiring further investigation. In addition, it outlines promising prognostic methodologies and identifies technical challenges for application to maritime LT-PEMFCs. In this way, this work lays the foundation for enhancing LT-PEMFC durability in maritime environments and supporting its broader adoption for zero-emission ships.

Recent research in chemical plant operation shows increasing interest in dynamic process operation as part of designed operating strategy for reasons such as increased dependency on renewable energy, and process intensification. Conventional analyses of fixed bed reactors are developed for steady state optimization and may not be adequate for dynamic operation. In fact, the important metrics and targets in dynamic process design are not entirely clear. The first objective of this article is to provide a state-of-the-art survey categorize types of dynamic operation, and rank the available common modelling and analytical tools suitable for quantification of dynamic process variables. The article then examines a case study of 1D and 2D model differences in a methanol steam reforming reactor. The case study shows model prediction differences of up to 15% for conversion, and up to 50% for CO concentration at the outlet during extreme load changes. The study concludes that the complexity of analytical and numerical techniques for dynamic processes is notably higher compared to steady state analyses, but appropriate tools and procedures are currently lacking.

As Polymer Electrolyte Membrane Fuel Cells (PEMFCs) emerge as a promising technology for transport decarbonization, the development of durability assessment protocols tailored to specific applications, such as maritime operations, is becoming relevant for the identification of stressors and lifetime enhancement. This study presents a preliminary experimental campaign aimed at introducing a methodology to assess the degradation of PEMFCs subjected to Accelerated Stress Test (AST). In particular, the methodology encompasses the utilization of electrochemical characterization and, in this work, the fuel cell operating profile has been chosen to mimic the operation of a small passenger vessel. The tests were carried out on two single Membrane Electrode Assemblies (MEAs) for 500 h. One membrane was subjected to the AST, and a second sample, tested under constant load operation, served as a reference. Periodic electrochemical characterization was conducted to assess performance degradation through polarization curves, electrochemical impedance spectroscopy, and cyclic voltammetry. The electrochemical analysis of degradation was conducted through a dual-method approach combining model-free and model-based methods for impedance analysis, as well as catalyst active area evaluation from voltammograms. Results show that the dynamic operation characteristic of the passenger ferry increases degradation compared to constant operation, evidenced by increased ohmic and interfacial resistances and losses in catalyst active area. This work provides a framework for developing application-specific durability protocols, enriched with multi-method diagnostic approaches to assess PEMFC degradation under realistic maritime conditions. Such methodologies support the development of durability enhancement strategies tailored to maritime applications, allowing a broader application of the technology in the sector.

This paper introduces a model predictive control (MPC) strategy for solid oxide fuel cell (SOFC) systems, introducing thermal stress-aware power modulation. The proposed MPC approach incorporates a temperature rate-of-change constraint to manage local temporal and spatial temperature gradients in the SOFC during transient power modulation. The study evaluates the sensitivity and effectiveness of the temperature rate-of-change constraint under four different constraint parameter sets, spanning a range from fast to slow power modulation. A one-dimensional spatially discretised SOFC model is employed in the simulations to assess the resulting local temperature gradients. The results of this paper indicate that the proposed MPC strategy enhances transient power tracking performance compared to the conventional approach of using an electrical current rate-of-change constraint with 1%–17%, without a significant increase in the local temporal and spatial temperature gradients in the SOFC.

Sustainability regulations urge the maritime sector to implement green technologies. The integration of polymer electrolyte membrane fuel cell (PEMFC) systems is a promising solution to cut emissions. However, their degradation in maritime environments is rarely addressed, while the environment differs significantly from land-based or automotive contexts and can greatly affect the type and extent of damage. Research in this field is especially relevant as ships often operate in isolated areas and require durable and reliable power propulsion systems. This work collects the insights from existing PEMFC durability research and analyzes degradation mechanisms specifically relevant for the maritime field. We consider air and fuel contamination, maritime load profiles, and vessel motions as potential causes. Insightful schematics summarize the content by linking these causes to damage indicators. Moreover, we identify various areas for further research including degradation from interconnected effects of maritime drive cycles, marine air salinity, hydrogen-carriers and their residues, long term maritime vibrations, and dynamic inclination. The overview of existing literature combines insights from electrochemistry and maritime research while the knowledge gaps help to prioritize future research. Together, these elements promote collaboration in this multidisciplinary field, advancing mitigation strategies and improving cell, stack, and ship design and operation. Such improvements encourage PEMFCs application in ships and support the move towards zero-emission shipping.

The maritime industry increasingly adopts hybrid fuel cell systems to reduce emissions and improve energy efficiency. This chapter examines the current state-of-the-art energy management strategies (EMS) for hybrid fuel cell applications in ships. It provides an in-depth analysis of various strategies, including rule-based, optimization-based, and learning-based approaches, highlighting their benefits, challenges, and real-world applications. The review begins with an overview of hybrid fuel cell systems, their configurations, and control strategies, followed by a detailed examination of EMS. Rule-based strategies are discussed in terms of their simplicity and effectiveness in dynamic marine environments. Optimization-based strategies are evaluated for their ability to enhance system and performance through advanced computational techniques. Learning-based strategies, particularly those leveraging machine learning and reinforcement learning, are explored for their potential to adapt to varying operational conditions. The chapter concludes by identifying the technical, economic, and regulatory challenges facing the adoption of these strategies and proposing future research directions.

Hydrogen economy is spreading across the maritime sector in response to increasingly stringent regulations for shipping emissions. The challenging on-board hydrogen logistics are often mitigated with hydrogen carriers such as methanol. Research on methanol reforming to hydrogen for fuel cell feed is conducted mostly in steady state, overlooking dynamic reactor operation and its effects on the power production system. Forced reactor operations induce fluctuations of CO content in the reformate potentially harmful to the PEM fuel cell, and drops in methanol conversion causing inefficient operation. In present research, simulations with a physical 2D unsteady model of a packed bed methanol steam reforming reactor resulted in methanol conversion drop durations of up to a minute. Additionally, temporary increases of CO content up to 112% were observed. Throughput ramp ups most notably impact the conversion, while ramp downs negatively affect selectivity. The investigation on reactor geometry concludes that larger tube diameters increase transient time and CO spikes, while they decrease with reactor length. Amplified unsteady effects are also observed with larger changes in input process variables. The results imply that heat transfer rate to the reactor are most often the detrimental factor for transient effects and durations in practice. Following this work, inclusion of realistic heating methods is recommended, instead of uniform tube temperatures used in present simulations. Heating system characteristics are necessary for realistic evaluation of the methanol reformer constraint on fuel cell feed demand in fully integrated systems.

Solid oxide fuel cell systems are considered for the power plant of ships, because of their high efficiency, low pollutant emissions, and fuel flexibility. This research compares the volume, mass, fuel consumption, and emissions of different hybrid power plants for cruise ships using solid oxide fuel cells, fuelled with marine gas oil and liquefied natural gas. A component sizing model allocates the installed power over the selected power plant components and determines their size and weight. The components and energy management strategy are simulated with a cruise ship for five years of operation. A simple method is implemented to estimate the degradation and its effect on component operation. The combined component sizing and time-domain model highlights the importance of dynamic simulation for battery sizing. The results show that using solid oxide fuel cells for the auxiliary consumers can reduce greenhouse gas emissions by 21% and pollutants by 38% to 46% with only 17.5% installed power, which has limited consequences for the cost and size of the power plant. With 31% installed power, the ship can operate in low-emission zones while reducing greenhouse gas emissions by 33% and pollutants by 60% to 70%. Performing all cruise operations requires 51% installed fuel cell power and reduces greenhouse gas emissions by 49% and pollutants by 94% to 96%. In conclusion, the study affirms that solid oxide fuel cell systems, with proper sizing and energy management, can be used to reduce shipping emissions and reach IMO's 30% GHG emission reduction target for 2030.

Switching to Proton Exchange Membrane Fuel Cell (PEMFC) systems can greatly reduce the environmental impact from the maritime industry. However, the limited durability of PEMFCs remains an obstacle for their implementation. Understanding fuel cell degradation is especially relevant for ships, as they typically operate for long periods and in isolated areas. Their energy systems therefore need to be exceptionally robust and reliable. In order to improve the design of maritime PEMFCs, we need to improve our understanding of degradation mechanisms induced by their use on a ship. Models can be a great tool to that end.
Many PEMFC models have been developed and used over three decades. They differ on various levels, from their spatial dimensions – one, two or three dimensional – to which processes are modelled and the detail to which they are described. Our previous review1 shows that numerous processes contribute to degradation in a maritime context. These include more general processes, such as load induced damage, as well more specific ones for ships, such as sea salt contamination via the air inlet.
Currently, there is no modelling framework to quantify PEMFC degradation in a maritime environment specifically. The aim of this work is to propose such a framework, building on knowledge gained from previous modeling studies. It should integrate the additional degradation triggers such as salt contamination. We start out by analyzing existing PEMFC durability models. They are rated based on the coding complexity, computational costs, specificity and the possibility to incorporate both specific
maritime as well as general degradation causes. Thereafter we analyze whether and how the models are validated and verified.
The proposed modeling framework can serve as a blueprint for future maritime PEMFC degradation models. These can facilitate vessel specific case studies, investigations to improve cell and stack design and explorations of altered ship operational profiles. The resulting insights will aid scientists, engineers and ship owners to improve PEMFC lifetime in maritime applications.

Shipping is a relatively clean transport method with low emissions per ton-mile compared with road transport. However, harmful emissions emitted in coastal areas are a concern, as these affect local air quality and health. To reduce sulphur oxide (SOX ) emissions, the International Maritime Organization (IMO) implemented a global sulphur cap of 0.5 wt% and the 0.1 wt% limit in emission control areas (ECAs). Ship owners can opt for either low sulphur fuels or wet scrubber systems. Wet scrubber systems are a reliable method for reducing SOX emissions with capture rates of up to 98%. These systems may use seawater alkalinity or caustic soda (e.g. closed-loop systems) to neutralise the SOX emissions. However, the dynamic loading of engines can cause large fluctuations in the exhaust flow conditions, and it is unknown how these affect the effectiveness of the scrubber. This study explores the impact of dynamic loads on the SOX removal efficiency of closed-loop wet scrubbers. A dynamic model of a closed-loop wet scrubber utilising fresh water and caustic soda is developed and verified using publicly available data. The model applies the two-film theory to model the gas-liquid interface. Billet and Schultes liquid hold-up theory is used to model the liquid film thickness in the packed bed. Maintaining scrubber efficiency with large load fluctuations or high-frequency fluctuations requires an increased liquid flow. The scrubber control system used a set-point of 75% of the equivalent compliance limit to ensure compliance with the 0.1% ECA limit during load fluctuations. The model and results can be used to develop a more advanced control system for improved scrubber operation and integration with a selective catalytic reduction (SCR) system to demonstrate compliance with the IMO NOX Tier III limit when using high-sulphur heavy fuel oil (HFO).

A growing concern is associated to the greenhouse gases emissions of superyachts, consequently alternative fuels are introduced to the market. For the yachting decarbonisation, this work focuses on hydrotreated vegetable oil (HVO) and methanol. Nevertheless, the uncertain global availability of these fuels can undermine the operations of ocean-crossing superyachts. Thus, a multi-fuel system is installed allowing for fuels switchover and built-in flexibility. Moreover, non-dedicated tanks are installed for the alternative storage of HVO and methanol to make optimal use of the tanks’ capacity. However, the alternative storage of HVO and methanol causes mutual fuels’ contamination. The lack of standards and research on accepted fuels impurity makes full fuels’ separation relevant to be explored. In this work, to avoid degradation of dual-fuel engines or fuel cells, gravity-settling tanks and disc-bowl centrifuges were studied to separate HVO-methanol mixtures. Shake tests were conducted on HVO-methanol mixtures to quantify the separation time and relative concentrations to obtain complete gravity separation. The gravity tests revealed methanol traces in HVO for all the tested mixtures within the 1 hour-3 days observation time, due to the low-density difference between the fuels. This makes the use of gravity-settling tanks impractical onboard for quasi-instantaneous fuels supply to the converters. A mathematical model was developed for disc-bowl centrifuges to assess the separator performance and separation time. Furthermore, the centrifuge was sized by providing the separator working conditions for varying engine modes. Moreover, spin tests were conducted to validate the mathematical model. The model showed that full separation is achievable with a larger centrifuge compared to existing designs. The larger design is due to the low-density difference between the fuels. The maximum separation time ranges from 5-10 minutes. Nevertheless, all the tested mixtures with the spin tests failed at achieving a state of full separation due to the dilution of a certain residual volume in the continuous liquid. The discrepancy between the mathematical model and the spin test results can lie in the neglected diluted phase of the dispersed fuel in the continuous liquid in the mathematical model. However, the mathematical model is a good tool to simulate the dynamic behaviour of the dispersed droplets. Consequently, the onboard use of a centrifuge for separating HVO-methanol mixtures should be evaluated by quantifying the concentration of the fuels’ mixture entering the separator tailored per yacht. Furthermore, tests on dual-fuel engines or fuel cells are recommended to establish tolerable limits of fuel’s contamination.

Solid oxide fuel cell (SOFC) technology offers a promising way to reduce maritime greenhouse gas (GHG) emissions.
Integration with a proton exchange membrane fuel cell (PEMFC) allows unreacted hydrogen, produced in the SOFC stack, to be reused and increase the electrical efficiency of the system. In this study, the Cycle Tempo software is used to model a SOFC-PEFMC combined cycle system operating on methane. The system is thermodynamically analysed to reveal the influence of SOFC fuel utilisation, cell voltage, operating temperature and PEMFC cell voltage on the system performance. A multivariable parametric analysis is applied to generate contour plots of net electrical efficiency and fraction of total power produced by the PEMFC. The analysis shows that increasing the cell voltage of both the SOFC and PEMFC has a positive influence on efficiency, whereas increasing the fuel utilisation reduces the system efficiency. Efficiencies in the range of 50-68% can be achieved. Model assumptions for PEMFC operating parameters are verified to exert little influence on the system efficiency, which confirms the assumption of constant values for these parameters. This study highlights the high-efficiency potential of the combined system and the difficulties that arise from thermally integrating an SOFC with a PEMFC.

HYLENA will investigate, develop and optimize an innovative, highly efficient integrated hydrogen powered, electrical aircraft propulsion concept for short and medium range. It will achieve significant climate impact reduction by being completely carbon neutral with radical increase of overall efficiency. The full synergistic use of: a) an electrical motor (as the main driver for propulsion), b) a contoured hydrogen fueled SOFC stacks (geometrically optimized for nacelle integration), c) a gas turbine (to thermodynamically integrate the SOFC), will act as an enabler for hydrogen aviation and will allow for efficient and compact engine concepts. This disruptive propulsion system will be called HYLENA concept. HYLENA aims to evaluate and demonstrate the feasibility of a “game changing” engine type which integrates Solid Oxide Fuel Cells (SOFC) into a turbomachine, in order to utilize the heat generated by the fuel cells on top of its electrical energy. The combination of e-motor, turbomachine and contoured SOFCs fueled with H2 will deliver high overall efficiency and performance versus state-of-the-art turbofan engines. Indeed, HYLENA Figures of Merit consist of minimizing CO2 emission; negligible NOX and an unmatched overall efficiency versus state-of-the-art turbofans which corresponds to an outstanding performance increase. It will also enable to extend the flight range for the same fuel tank size. The HYLENA project will deliver: 1. On SOFC cell level: Experimental investigations on SOFC cell technologies and identification of the most promising one(s) for aeronautical applications; 2. On SOFC stack level: Studies and tests to determine the most compact/light/manufacturable way of stack integration; 3. On thermodynamic level: Cycles simulations of the proposed novel HYLENA concept architecture and down selection of the most performing one; 4. On engine design level: Exploration, through resilient calculation and simulation, of the best engine design, sizing and overall components integration; 5. On overall engine efficiency level: Demonstration that HYLENA concept can reach very high efficiency levels with limited weight and complexity; 6. On demonstration level: A decision dossier for a potential ground test demonstrator to prove that the HYLENA concept works in practice during a second phase in the continuity of this project.

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.

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.

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.

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.

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.

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.