Methods to Improve Response Time in Fuel Cell Systems

This paper outlines a semi-empirical model to account for the transient response of Polymer Electrolyte Membrane Fuel Cells (PEMFC) during load changes. In this work, we investigated the voltage undershoots of the PEMFC system with a current step-up given as the input. The dynamic response of PEMFC during stepwise load changes is a vital factor that indicates cell performance. We present a model based on mass balance equations, various transport phenomena, and experimental conditions for these voltage undershoots. This model’s response highlights the impact of reactant starvation inside the fuel cell stack during step increase in current. A single fuel cell is divided into two domains to analyze the availability of reactant gases. The model can anticipate the impact of different operating conditions on the magnitude of voltage undershoots. Validation of the model with experimental data resulted in a maximum relative error of 4.59%, with the goodness of fit in the range of 0.96 to 0.99, making the model statistically significant.

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Introduction Fuel cell technology is a harbinger of the future for generating electricity due to their high efficiency and low emissions achieved through the direct conversion of chemical energy into electrical energy without combustion. Methods To optimize the design and performance, a fuel cell model is essential to predict its behaviour in different conditions. This technical note presents a novel physics-based approach, the Young’s Double-slit Experiment Optimizer (YDEO), for identifying parameters in Proton Exchange Membrane Fuel Cells. A performance metric is established by formulating an objective function that relies on the summation of squared errors between experimental and estimated values. Results and discussion The effectiveness of this approach is evaluated through the analysis of four benchmark test cases: Horizon 500 W, BCS500 W, NedstackPS6, and 250 W. The corresponding objective function values for these test cases are 0.011243, 2.065557, 0.011698, and 5.250849, respectively. The simulation results demonstrate the efficacy of the proposed YDEO algorithm when compare... Read More

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Fuel cell vehicles (FCVs) represent a pivotal advancement in the evolution of future automobile technologies. This paper introduces a comprehensive approach to enhancing the performance of automotive fuel cells, employing the Predictive Trip Distance Adaptive Equivalent Consumption Minimum Strategy (PTDA-ECMS) objective function for predictive analysis. By developing innovative alkaline electrolyte membranes, catalysts, and electrode materials, and implementing hybrid power system management strategies for fuel cell and battery integration, this study aims to extend fuel cell longevity, improve system efficiency, and reduce operational costs. Additionally, the use of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for electric catalyst evaluation signifies a methodical exploration into fuel cells with enhanced service life, reduced production expenses, and superior overall performance. Such advancements are anticipated to decrease the operational costs of electric vehicles, thereby increasing marketability and facilitating more sustainable human transportation solutions. This p... Read More

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In this paper, a meticulous modeling approach is proposed not only for a fuel cell stack itself but also for all auxiliary components that collectively form the fuel cell system. This comprehensive modeling approach encompasses a wide range of components, including, but not limited to, the hydrogen recirculation pump and the air compressor. Each component is thoroughly analyzed and modeled based on the detailed specifications provided by suppliers. This involves considering factors such as efficiency, operating parameters, response times, and interactions with other system elements. By integrating these detailed models, a holistic understanding of the entire fuel cell system’s performance can be attained. Such an approach enables engineers and designers to simulate various operating scenarios, predict system behavior under different conditions, and optimize the system design for maximum efficiency and reliability. Moreover, it allows for informed decision-making throughout the system’s development, deployment, and operational phases, ultimately leading to more robust and effective en... Read More

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To improve the fuel cell durability of the hydrogen Electric Multiple Units, this paper proposes a novel multi-stack fuel cell hybrid system energy management strategy in consideration of fuel cell degradation. The top layer of the method distributes the power of fuel cells and lithium batteries reasonably according to the Equivalent Consumption Minimization Strategy, and adjusts the fuel cell power through the feedback power regulation module. The bottom layer distributes the power of different stacks according to the degradation degree. The proposed layering method improves the durability of fuel cells by reducing the fuel cell degradation degree. The hardware-in-the-loop (HIL) experiments results show that, compared with the traditional equivalent hydrogen consumption minimum energy management strategy, the proposed method is effective in lowering the degradation degree and operating pressure of the fuel cell by 25.77% and 35.73% respectively.

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The adaptability of fuel cell vehicles in low-temperature environments remains challenging for their commercialization owing to the propensity of water within the fuel cell to freeze during a cold start, which impedes gas transmission and subsequent reactions. Consequently, the initial water content before cold start and the heat and water generated during this process are crucial for achieving a successful cold start. In this study, current- and voltage-controlled starting strategies are analyzed using a stack comprising 20 cells with an area of 285 cm 2 . Furthermore, key parameters related to shut down purging and cold start are optimized using starting time and reverse polarity cell count as optimization objectives. The optimal conditions for cold start include a current density of 0.5 A cm −2 , voltage of 0.45 V, purging time of 180 s, and stack temperature (during purging) of 60 °C. Furthermore, the ambient temperature boundary is determined as −25 °C–−30 °C for a successful cold start without auxiliary heating in the stack.

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Activation is a crucial procedure to improve the performance of newly fabricated fuel cell stacks to meet the power requirements in actual application scenarios. However, traditional activation procedures generally last for several hours or even days, which greatly increases the cost and limits the production efficiency. In response to this problem, this paper proposes a rapid activation procedure composed of hydrogen pumping (HP) and limiting-current activation with limited air (LCA). The influence of current density for HP and air supply for LCA on activation effect is studied and the best operating conditions are determined. The importance of water supply to the cathode is highlighted during HP. The influence of air supply for LCA on activation effect is limited, which contributes to gas saving. According to the experiments conducted on a single cell and a 10-cell stack, only 40 min are needed with this combined procedure, which is much shorter than that of the traditional step-current activation. Furthermore, nearly 75% of hydrogen is saved due to the short activation time and th... Read More

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<title>Abstract</title> In fuel cells, disparities in individual cell performance can significantly impact various aspects of the overall system, including uneven energy output, accelerated aging, poor system stability, and decreased safety. Hence, enhancing the balance within fuel cells holds paramount importance. Accordingly, this study utilized Matlab and COMSOL to establish a 1D model of the fuel cell stack and a 3D model of individual cells for combined simulation. The aim was to analyze performance discrepancies between individual cells arising from flow distribution issues, investigate how flow rates affect individual cell performance, and ultimately, improve fuel utilization by optimizing individual cell flow channel dimensions. This optimization aimed to address performance deficiencies caused by insufficient gas supply. The research findings indicate that pre-optimization and post-optimization of flow field dimensions, the performance of cells experiencing insufficient gas supply (at the lowest inlet flow rate) improved by 5.59%. Increasing the inlet flow rate enhances indi... 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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The startup performance is crucial to the high-efficient operation of the sustainable power generation system. Current literature usually focuses on catalysts and startup strategy to improve startup performance of the proton exchange membrane fuel cell, which ignores the gas foil bearings-rotor system that directly affects startup response. Therefore, in this paper, the effects of bump foil structure, coating, and nominal clearance on the startup response of the bearings-rotor system are first investigated experimentally. Multi-objectives optimization mathematical model considering simultaneously lower power consumption, takeoff speed, and vibration is presented based on grey relational analysis. The optimal bearings-rotor system with radial trisection bump foil, coating MoS2, and nominal clearance of 50 μm is identified. Compared to average values, the power consumption of the optimal system is diminished by 27.2% while the takeoff speed and nonlinear vibration are reduced by 16.2% and 47.3%, respectively. These findings can be used to improve energy efficiency and startup performan... Read More

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<title>Abstract</title> The performance of fuel cells is influenced by many factors, among which operating temperature is crucial. Therefore, this study focuses on analyzing the performance of fuel cells at different temperatures and optimizing operational parameters at the optimum temperature condition to enhance the performance and lifespan of fuel cells. The research finds that the optimal temperature for fuel cells is 69.9°C, with an efficient operating temperature range of 60–80°C, and the optimal flow rate range is 1000–1600 ml/min. The influence of back pressure on fuel cell performance becomes less significant when it exceeds 2.5 bar. Furthermore, this study utilizes a Gaussian process regression model to optimize the performance of fuel cells under different temperature, flow rate, and back pressure combinations. Regression analysis model predictions suggest that the optimum operating temperature is 71°C, with an optimal back pressure range of 0.9–1.4 bar and a flow rate range of 1310–1600 ml/min.

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Dynamic performance of proton exchange membrane fuel cell (PEMFC) significantly influences the durability and reliability. This study experimentally investigates the transient response of PEMFC when starting with different load levels under various operating conditions. The results indicate that the dynamic behavior follows a "two-stage" response mode when starting with a low load. While starting with a high load, due to the flooding at the cathode, the voltage fluctuation during the starting process is larger and the starting time is longer, following a "three-stage" response mode. Increasing the cathode stoichiometry ratio obviously enhances the dynamic performance of PEMFC during startup. Increasing the anode stoichiometry ratio has minimal impact on the dynamic behavior when starting with a low load, whereas starting with a high load it results in longer response time and larger voltage fluctuation. As the load carried at startup increases, augmenting cathode inlet humidity consistently improves the dynamic response of the output voltage more effectively than increasing anode inl... 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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The low-temperature cold start has become one of the leading technical bottlenecks limiting the large-scale commercial application of proton exchange membrane(PEM) fuel cells. This paper establishes the 1-D numerical model of the fuel cell stack to study the reactant gas, charge transfer, heat transfer, and water phase transition process. Then the critical parameters in the numerical model of the fuel cell stack are identified based on the cold start experiment data. The identification results show that the cold start model is consistent with the experimental results, and the model's output voltage and average temperature errors are under the acceptable range. Based on the numerical model, with the cold start time as the optimization objective and load current and initial membrane water content as the optimization variable, the cold start strategy is optimized under different ambient temperatures. The results show that the optimized current loading strategy can reduce the cold start time of the fuel cell stack and achieve a fast, successful cold start for −20 °C and − 25 °C condition... Read More

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Improving the commercial fuel cell system efficiency is critical to reducing hydrogen consumption and improving the operational economy. This paper studies the power consumption pattern of the air supply subsystem, the most power-consuming auxiliary components, aiming to improve the system's efficiency. A method was proposed to get the extremum of the system net power by optimizing the oxygen excess ratio and cathode pressure. Mathematical models describing the fuel cell stack and air supply subsystem power characteristics were developed based on the mechanism analysis and estimation of unknown parameters. Then, a system net power model for energy efficiency optimization was developed. The operating conditions for optimal efficiency at a specific current density can be obtained by numerical calculation. To verify the method's effectiveness, a series of experiments were conducted, and the results show that the proposed method can maximize system net power output at various current density conditions. Compared with the conventional oxygen excess rate based one-dimensional optimization,... Read More

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The energy management system and thermal control of fuel cell in fuel cell vehicles plays a crucial role in ensuring their stable and efficient operation.This study presents a novel fuel cell powertrain energy management system control strategy considered the temperature fluctuation based on deep reinforcement learning.A comprehensive SIMULINK model, encompassing fuel cell cooling system and stack models, was constructed for the fuel cell, followed by simulation testing under various temperature scenarios.To validate the robustness and stability of the control system, the standard operating conditions -US06 were employed for experimental verification.The experimental results highlight the effectiveness of the designed fuel cell energy management system in achieving transient temperature stabilization.Additionally, the results revealed that stable operation temperatures correlate with reduced hydrogen consumption.Furthermore, it's noted that fuel cell hydrogen consumption displays substantial variation under uniform operating conditions at varying temperatures.This highlights the key ... Read More

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Recently, the development of heavy-duty fuel cell vehicles (HDFCVs) has received intense attention. Unlike the refuelling protocol of SAE J2601 for light-duty fuel cell vehicles, the SAE J2601-2 for HDFCVs does not propose a specific filling strategy but only specifies the limits that need to be observed for safety. Refuelling data for HDFCVs at hydrogen refuelling station (HRS) shows that refuelling parameters are often set conservatively, resulting in long refuelling time. To shorten the refuelling time, energy consumption and power demand of the cooling system, we establish a detailed three-stage pressure filling model to study the effects of pressure ramp rate (PRR), initial pressure, number of onboard tanks and precooling temperature on the filling time. Then, a three-stage temperature precooling method is proposed simultaneously, whose cooling energy and power of the heat exchanger are compared with the single-stage temperature precooling method. Research shows that three-stage and two-stage pressure filling can reduce the average pressure difference between the station-side an... Read More

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PEM fuel cells are encouraging energy conversion technologies that offer low emissions and high efficiency for various applications, auto motives in particular. In order to create flexible and adaptive models that accurately depict the complex electrochemical, transport, and thermodynamic processes within these systems, a parameterized technique for modelling PEM fuel cells is essential. This work focuses on investigating the profound impact of load and temperature variations on the steady-state behavior of PEM fuel cells. The parameterized approach is then employed to develop a dynamic model of PEM fuel cells. The dynamic model captures the intricate dynamics of the cell under varying load conditions, considering the transient behavior of the cell components and the interactions between the different physical phenomena.

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The gas flow channels inside unitized regenerative fuel cells display obvious effects on relevant parameter changing behaviors such as species concentration, electrical signal and thermal signal during mode switching. In previous study, detailed transportation behaviors inside a cell constructed with streamlined channels have not been investigated. In our present study, a two-dimensional, transient model coupling non-isothermal characteristics is employed to study the changing characteristics of the cell with typical streamlined channel and comparatively analyze the channel structure impacts on the working states inside the operating cell regions. The simulated results indicate that when turning the mode from electrolyzer to fuel cells, the changing response occupied time of each parameter is required more, compared with the stabilizing procedure after entering the electrolytic cell procedure. For different oxygen-side channels, when reducing the channel depth, the current density output is raised, and the needed time-span for the stabilizing the working state is reduced. The present... Read More

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Abstract This paper aims to achieve stable and reliable operation of the marine PEM fuel cell systems. To accomplish this, a dynamic model that incorporates the thermodynamic electric potential and the three irreversible voltage losses of the fuel cell was established and simulated using Matlab/Simulink software based on the steady-state model of the PEM fuel cell. Under certain ideal conditions, the dynamic response of the PEM fuel cell was simulated and analyzed concerning various environmental factors and internal parameters of the fuel cell stack. An input signal source was used as an applied load for this purpose. The simulations and analysis focused on examining the impact of each factor on the performance of the PEM fuel cell. Specifically, the dynamic response is investigated when the load signal undergoes a step change. In addition to enhancing the drawbacks of the conventional steady-state system model, which tends to be complex with redundant parameters and a large amount of data, the dynamic model also establishes a theoretical foundation for optimizing the performance of... Read More

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