Water Management Strategies in Fuel Cell Systems

Abstract The current research status of fuel cells in the space field is first introduced, followed by an analysis of the comprehensive utilization mode of fuel cell energy from three aspects: water, gas, and heat. The fuel evaporated from the liquid hydrogen and liquid oxygen tanks of spacecraft can be used for fuel cell power generation. The heat generated by fuel cells can be used to preheat gases through a dual-channel heat exchanger, achieving thermal energy recovery for hydrogen and oxygen fuels. The water produced by fuel cells can be separated and recovered through static drainage for reuse in heating control or environmental control systems. A prototype of a fuel cell power generation system is designed and relevant performance tests are conducted. When the fuel cell system stably generates 400W of power, approximately 215W of waste heat can be reused. The utilization efficiency of hydrogen and oxygen fuels reaches over 97%, and the water recovery efficiency of the system reaches over 95%.

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Fuel cell technology represents a promising pathway toward sustainable energy systems, offering efficient and clean energy conversion. This paper explores the fundamental principles of fuel cell technology, its various types, and its applications in different sectors. The discussion highlights the key challenges, including high costs, technological limitations, and infrastructural hurdles, as well as the opportunities such as environmental benefits, energy security, and technological advancements. The paper aims to provide a comprehensive overview of the current state and future prospects of fuel cell technology in contributing to sustainable energy solutions.

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Fuel cells, in combination with water electrolyzers and other renewable energy technologies promise to be an attractive near-future alternative to generate electricity in a direct, sustainable, and environmentally-friendly way.

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In recent years, fuel cells have gained prominence as a vital sustainable energy source. proton exchange membrane fuel cells (PEMFCs), utilizing hydrogen for electricity generation, have become especially widespread. However, addressing water management challenges remains crucial. Accumulated liquid water in the reaction area hampers reactant access, impacting the reaction rate and protonic conductivity, making effective water management pivotal for optimal PEMFC performance. The current work reports a comprehensive review of many methods to achieve efficient water management to attain higher fuel cell performance and increase its lifetime. Moreover, optimizing the operating conditions, using novel design configurations for the flow fields, and using new materials with specific surface treatment methods to fulfill this desired mission are discussed. A review of the methods used to visualize or model the water generation inside the flow channels and porous layers of PEMFCs is provided. In addition, the most recent water management methods, techniques, and materials are discussed. The ... Read More

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Regenerative fuel cells can operate alternately as an electrolyzer and as a fuel cell, frequently involving water as a reactant or product. Modifying the electrode surface to manipulate water can prevent electrode flooding and enhance the electrode's mass transfer efficiency by facilitating better contact with gaseous reactants. However, conventional electrodes face difficulties in allowing water droplets to penetrate in a single direction leaving electrodes. In this work to address this issue, a wettability gradient electrode is designed and fabricated for efficient water manipulation in regenerative fuel cells. The findings demonstrate that the water removal strategy in the electrolyzer mode yields the highest ammonia yield and Faradaic efficiency of 3.39 10-10 mol s-1 cm-2 and 0.49 %, respectively. Furthermore, in the fuel cell mode, the discharging process sustains for approximately 20.5 h, which is six times longer than the conventional strategy. The ability to sustain the discharging process for extended periods is particularly advantageous in regenerative fuel cells, as it e... Read More

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Energy Management Strategies for Fuel Cell Vehicles: A Comprehensive Review of the Latest Progress in Modeling, Strategies, and Future Prospects

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This paper investigates fuel cell technology, an efficient and environmentally friendly method for generating electricity by harnessing the energy content of hydrogen or alternative fuels. Fuel cells produce electricity with water, heat, and power as the only by-products when hydrogen is used as fuel, making them a clean and sustainable energy option. Future applications in the hydrogen economy are expected to utilize fuel cells as safe, quiet, and reliable energy sources. Fuel cells exhibit superior efficiency compared to combustion engines, promptly converting fuel energy into electrical energy. Various types and sizes of fuel cells with distinct technological requirements have been developed by scientists and inventors to enhance efficiency. The choice of electrolyte is a critical factor influencing the possibilities available to fuel cell inventors. Beyond exploring the technologys evolution, this paper delves into the diverse applications of fuel cells across different sectors. From transportation to industrial processes and residential power generation, fuel cells play a cruci... Read More

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Abstract This paper introduces the application demands and research progress of fuel cells in the space field. Subsequently, an analysis of the comprehensive energy utilization modes of fuel cells from the aspects of water, gas, and heat is conducted. The fuel evaporated from the liquid hydrogen and liquid oxygen tanks of spacecraft can be used for fuel cell power generation, and the heat generated by fuel cells, together with the low-absorption and low-emissivity thermal control coatings, maintains the temperature of the spacecraft in the shadow area. The product water from fuel cells can be purified for reuse in thermal control, environmental control, and water electrolysis cells. The hydrogen and oxygen produced by electrolyzing water can be recycled for fuel cell power generation, and the oxygen can also be used for environmental control and life support, while the hydrogen can be used for methane production. To reduce system weight and achieve comprehensive utilization of energy and resources, integrated system design and research on regenerative fuel cell system principles are ... Read More

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Controlling the relative humidity is crucial for improving fuel cell performance in self-humidifying fuel cells. In light of this, this study investigates the influence of humidity variation on Proton Exchange Membrane Fuel Cells (PEMFC) performance through single-cell testing and a two-dimensional two-phase model. In the experiment, different humidity conditions are achieved by adjusting the inlet air temperature, and the effect of relative humidity on cell performance is observed. The research findings indicate that as the relative humidity increases, the performance of the fuel cell gradually improves. Increasing humidity reduces voltage fluctuations, particularly at low flow rates, demonstrating more stable performance. Under different humidity conditions, when the inlet air flow rate exceeds a certain value, the voltage non-uniformity of the cell remains within 1, indicating insignificant voltage fluctuations, attributed to the effects of inlet air flow rate on performance improvement and alleviation of flooding phenomena. Analysis of the two-dimensional two-phase model reveals ... Read More

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Proton exchange membrane fuel cells (PEMFCs) are efficient and zero emission energy conversion technology with promising application prospects towards carbon neutrality. The PEMFC's performance is largely affected by the poor water management, which is a substantial concern for long term durability. Herein, we overview the water management problems in PEMFCs, such as flooding and dehydration of membrane electrode assembly and analyze the causes and their impacts on the device performance. Major problems such as flooding impedes the gas transport and electrode reactions, while dehydration increases the membrane resistance and hinders proton transport. We have thoroughly overviewed several electrochemical and physicochemical diagnostic techniques for water management in PEMFCs. Additionally, material development and optimization approaches for the flow field structural design are explored in order to improve mass transport and wetting characteristics for optimized water management. Therefore, it is anticipated that this review will provide insights into the effective operation of PEMFC... Read More

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Water management is crucial for achieving high-performance proton-exchange-membrane fuel cells (PEMFCs), as it helps keep the electrolyte hydrated while avoiding performance degradation and cell shutdown due to liquid-water accumulation. According to ex-situ measurements [1-3], accumulation of liquid water in gas-diffusion layers (GDLs) of PEMFCs is a transient process that can be accompanied with oscillations in capillary pressure and saturation. To understand how liquid-water accumulation and drainage impact PEMFC performance hysteresis and stability, a transient cell-level model that accounts for electrode structure and composition and is computationally efficient is needed. A number of volume-averaged models that describe the electrode structure through pore-size distribution have been developed in the past [4-7], but they are steady-state and thus cannot predict dynamic PEMFC performance. Existing transient models have also not been used to analyze cyclic liquid-water accumulation [8-10]. In this work, a transient two-phase 2D PEMFC model is developed in the open-source fuel-cel... Read More

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A fuel cell is a promising energy conversion system that will eventually become the first-choice for producing power because of its clean or zero-emission nature. A steady-state, two-dimensional mathematical model with a complete set of governing equations valid in different components of a PEM fuel cell was developed to illustrate the temperature and water content effects on proton exchange membrane (PEM) fuel cell performance. This model considers the transport of species and water along the porous media: gas diffusion layers (GDL) anode and cathode, and the membrane of PEMFC fuel cell. To improve the kinetics of electrochemical reactions at the electrodes and thus reduce the activation overvoltage: increase the gas diffusion electrodes reduce the drop ohmic, especially in the proton conductive membrane through an increase in ionic conductivity. The electrochemical performance of a fuel cell will be strongly depend temperature and water content.

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Water management is an important criterion in the operation of proton-exchange membrane fuel cells to maintain the high performance and reliability of the system. The water content in the cathode air that is supplied to the cathode channel contributes to the membrane humidification and the transport of protons inside the membrane structure. In automotive applications, the supply air is typically driven through an external membrane humidifier to absorb more moisture from the recirculated cathode exhaust. In the literature, humidifiers and fuel cell stacks have been separately investigated without considering whole-system configurations for water management. This study investigates changes in the cathode air characteristics through a membrane humidifier and compares two configurations using a humidifier bypass of the supply flow and exhaust flow to adjust the cathode inlet air relative humidity. Each component in the system was modeled using mathematical relations and converted into blocks of inputs and outputs in MATLAB/Simulink for simulation. The bypass valve was demonstrated to eff... Read More

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Now is the time for hydrogen, it is a new vector of energy independence, which is available to decarbonize several sectors of the world economy. Unfortunately, Hydrogen is only rarely present by electrolysis of water, which is an electrolytic process that, breaks down water (H2O) into di oxygen and hydrogen gas, using an electric current offered by a conventional or a renewable energy source. In fact, thanks to a water electrolyzer and a fuel cell, it is possible to switch from electricity to hydrogen and vice versa, without emitting any pollutant in situ. Beyond the obvious priority goals, such as reliability and lifespan, it can be difficult to predict how fuel cells will be used in the future. Several researches treated this phenomenon, and treated the Fuel cell. In this paper, we illustrate a modeling of an Exchanged Proton Membrane Fuel Cell (PEMFC), using Matlab/Simulink. This modeling will highlight the influence of different parameters on the efficiency of the PEMFC and the electricity produced.

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<div class="section abstract"><div class="htmlview paragraph">Fuel cells are considered one of the promising technologies as possible replacement of Internal Combustion Engine (ICE) for the transportation sector due to their high efficiency, ultra-low (or zero) emissions and for the higher drive range.</div><div class="htmlview paragraph">The Membrane Electrode Assembly (MEA) is what mainly influences the Fuel Cell FC performance, durability, and cost. In PEMFC the proton conductivity of the membrane is a function of the humidification level of the FC membrane, hence the importance of keeping the membrane properly humidified to achieve the best possible fuel cell performance. To have the optimal water content inside the fuel cells membrane several strategies could be adopted, dealing with the use of external device (such as membrane humidifier) or to adopt an optimal set of parameters (gas flow rate and temperature for example) to use the water produced at fuel cell cathode as humidity source.</div><div class="htmlview paragraph">The aim of this p... Read More

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Water management is a crucial aspect of hydrogen fuel cell operation because inadequate management can lead to significant losses in mass transport, limitations in oxygen diffusion, and membrane durability issues. This study investigates the impact of various operational conditions on the initial formation and evolution of liquid water content and distribution, as well as water evacuation, within a lung-inspired PEM fuel cell with a 50 cm2 active area. A series of experiments were conducted to assess the effects of cell pressure, relative humidity of the reactant (anode and cathode), temperature, and cell current density. Neutron imaging was utilized as it has been shown to be an effective technique for quantitative analysis of water distributions. The results indicate that water initially appears in the sponges located in the central region of the cathode, but due to considerable back-diffusion, water predominantly accumulates in the area of the anode channels in contact with the cathode sponges. The amount of water in the cell increases faster when the relative humidity of the cath... Read More

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Because of its clean or zero-emission nature, the PEM fuel cell is considered a potential energy conversion device for power production. The performance of the PEM fuel cell is known to be influenced by many parameters, such as operating temperature, pressure, and humidification of the reactants. In addition, the operational stability of the PEM fuel cell under these conditions with the purging of water during its operation should also be studied to understand the performance of the PEM fuel cell. Therefore, this paper brings out the effects of cell humidification and cell heating on the performance, especially the operational stability concerning the liquid water removal of the PEM fuel cell. The experiments are conducted on a single PEM fuel cell with mixed flow distributors operating on different cell temperatures and humidification conditions. At dry feed operation of the PEM fuel cell at ambient condition, the cell utilizes around 80.3% of water generated for its membrane hydration, i.e., self-humidification. When the PEM fuel cell is operated at full humidification (100% RH) on... Read More

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A good water management is very important for the operation of PEM fuel cell systems as the proton conductivity is dependent on the membrane water content. In contrast to state of the art approaches, this study focuses on an anode based water management approach of fuel cell systems with an anode recirculation loop. The aim of the anode based water management is to reach a high and homogeneously distributed anode humidity without condensation in all relevant operating conditions. A criterion is defined to evaluate the anode humidity distribution. A macroscopic discrete 2D+1D model was developed that can simulate humidity distributions and the cell voltage for various flow directions of the fluids and operating conditions. The model considers the system behavior including the anode recirculation loop. This study shows that flow directions that support an internal water circulation are beneficial for fuel cell systems without external humidification. Furthermore, the study shows a correlation between the anode humidity distribution at the membrane and the cell voltage. The higher the t... Read More

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Water management is a key factor in the operation of hydrogen fuel cells since its formation may lead to significant mass transport losses, oxygen diffusion limitation and membrane durability issues. In this work, the effect of different operating conditions on the liquid water distribution inside a 50 cm2 active area bio-inspired PEM fuel cell has been studied. Therefore, a set of experiments was designed varying cell pressure, the reactants relative humidity (anode and cathode), temperature, and cell current density. Liquid water distribution for each operating condition was determined using neutron imaging technique as it has been proved to be an excellent technique for this purpose, including quantitative analysis and water profiles in the different areas of the bio-inspired flow field. The results show that high relative humidity of the inlet gas flows, high pressure, low temperatures and low current density favor the accumulation of water in the flow field channels and GDL. Specifically, water accumulates preferentially in the anode side that make contact with the low part of t... Read More

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Fuel gas utilization and water management are particularly challenging integrated engineering problems in hydrogenoxygen proton exchange membrane fuel cell (H 2 /O 2 PEMFC) systems. Herein, a standardized process is adopted to evaluate the performance and investigate the degradation mechanisms of a PEMFC with dual exhaust gas recirculation. The purpose of incorporating recirculation subsystems in the fuel cell is to achieve a high fuel gas utilization rate and realize effective water management inside the stack, which consists of 3Dprinted ejectors and a customized recirculation pump. Evaluation of the electrochemical performance degradation and morphological characterization of the fuel cells under different operating strategies are performed after 50 h durability experiments. At a current density of 400 mA cm 2 , the performance degradation rates of the stack decrease from 16.50% to 7.49% and 0.71% in the ejector and recirculation pump operation strategies, respectively. The results show that using exhaust gas recirculation devices (ejector/pump) in the fuel cell stack can help ... Read More

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