Behavior Of Proton Exchange Membrane Fuel Cell Research Articles

Deep Learning-Based State-of-Health Estimation of Proton-Exchange Membrane Fuel Cells under Dynamic Operation Conditions.

Proton-exchange membrane fuel cells (PEMFCs) play a crucial role in the transition to sustainable energy systems. Accurately estimating the state of health (SOH) of PEMFCs under dynamic operating conditions is essential for ensuring their reliability and longevity. This study designed dynamic operating conditions for fuel cells and conducted durability tests using both crack-free fuel cells and fuel cells with uniform cracks. Utilizing deep learning methods, we estimated the SOH of PEMFCs under dynamic operating conditions and investigated the performance of long short-term memory networks (LSTM), gated recurrent units (GRU), temporal convolutional networks (TCN), and transformer models for SOH estimation tasks. We also explored the impact of different sampling intervals and training set proportions on the predictive performance of these models. The results indicated that shorter sampling intervals and higher training set proportions significantly improve prediction accuracy. The study also highlighted the challenges posed by the presence of cracks. Cracks cause more frequent and intense voltage fluctuations, making it more difficult for the models to accurately capture the dynamic behavior of PEMFCs, thereby increasing prediction errors. However, under crack-free conditions, due to more stable voltage output, all models showed improved predictive performance. Finally, this study underscores the effectiveness of deep learning models in estimating the SOH of PEMFCs and provides insights into optimizing sampling and training strategies to enhance prediction accuracy. The findings make a significant contribution to the development of more reliable and efficient PEMFC systems for sustainable energy applications.

Simulation Approaches and Validation Issues for Open-Cathode Fuel Cell Systems in Manned and Unmanned Aerial Vehicles

Hydrogen is a promising energy carrier in all fields of transportation, including unmanned aerial vehicles (UAVs) and manned vehicles for urban air mobility (UAM). In these applications, one of the biggest challenges is to overcome the limitations of lithium battery technologies, while keeping the advantage of clean energy, at least in terms of direct emissions. For these reasons, there is an ever-increasing interest in the development, simulation, and testing of propulsion systems adopting air-cooled proton exchange membrane fuel cells (PEMFCs). Fuel cells for aerospace must be designed for power-to-weight maximization. For this reason, auxiliary systems are simplified, and the adoption of air-cooling and passive cooling techniques is favored. However, the performance and dynamic behavior of PEMFCs are affected by the operating conditions, which, in applications like UAVs and UAM, are continuously changing due to the variation of speed and altitude during the flight. This investigation analyzes semi-empirical and control-oriented models of fuel cell systems proposed in the scientific literature. The review addresses the whole fuel cell system, inclusive of the balance of the plant, and introduces the transition from dynamic models to digital twins.

Reduced-order modeling of PEM fuel cell based on POD and PODI: an efficient approach toward combining highest accuracy with real-time performance

The main contribution of this study is developing an efficient reduced-order model for accurate real-time simulation of a proton exchange membrane fuel cell (PEMFC). The basis of reduced space are created by the proper orthogonal decomposition (POD) of the snapshots obtained from the simulation results of the finite-volume method. Another approach is introduced by interpolating between the coefficients of POD, known as PODI method. The developed reduced-order models are examined by simulating the electrochemical behavior of PEMFC for various geometrical parameters and operating conditions, including porosity of catalyst layers, cell temperature, and concentration of inlet oxygen. An extensive eigenvalue analysis of dominant energetic modes shows that the PEMFC can be simulated accurately with very low computational cost. Compared to the finite-volume method (full-order model), speed-up factors of 27 and 67 are achieved by the POD and PODI methods respectively, which can potentially be used for real-time, optimization, and control purposes.

Stress response and contact behavior of PEMFC during the assembly and working condition

Mechanical behavior of proton exchange membrane fuel cell (PEMFC) is closely related to its service life. Stress response and contact behavior of PEMFC during the assembly and working condition were investigated. Effects of clamping force, steel bands number and width on the mechanical behavior of PEMFC were discussed. Thermal-mechanical coupling was considered during the PEMFC working for thermal effect caused by chemical reaction. The results show that stress distribution of multi-cells is more uniform after assembly. Stress and contact pressure distributions of single-cell and multi-cells are similar after assembly. During the assembly process, the average contact pressure between the MEA and other parts increases with the increasing of clamping force, steel band width and number. With the steel bandwidth increases, the contact pressure distribution of MEA is more uniform. And the chemical reaction inside the fuel cell is more favorable. Stress concentration is prone to appear on the corners of GDL on the MEA, corners of sealing gasket, and edges of bipolar plate ribs, which may cause seal failure after long-term work. Under working condition, thermal expansion can enhance the sealing performance, but affect stress of bipolar plate and MEA. Those results can be used for design, manufacturing, maintenance and evaluation of PEMFC.

Numerical and Theoretical Study of Performance and Mechanical Behavior of PEM-FC Using Innovative Channel Geometrical Configurations

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of the dipole plates, so that while high strains are provided below the rib, the domain continues in its initial uncompressed case under the ducts approximate to it. This leads to significant spatial variations in thermal and electrical connections and contact resistances (both in rib–GDL and membrane–GDL interfaces). Variations in heat, charge, and mass transfer rates within the GDL can affect the performance of the fuel cell (FC) and its lifetime. In this paper, two scenarios are considered to verify the performance and lifetime of the PEM-FC using different innovative channel geometries. The first scenario is conducted by adopting a constant channel height (H = 1 mm) for all the differently shaped channels studied. In contrast, the second scenario is conducted by taking a constant channel cross-sectional area (A = 1 mm2) for all the studied channels. Therefore, a computational fluid dynamics model (CFD) for a PEM fuel cell is formed through the assembly of FC to simulate the pressure variations inside it. The simulation results showed that a triangular cross-section channel provided the uniformity of the pressure distribution, with lower deformations and lower mechanical stresses. The analysis helped gain insights into the physical mechanisms that lead to the FC’s durability and identify important parameters under different conditions. The model shows that it can assume the intracellular pressure configuration toward durability and appearance containing limited experimental data. The results also proved that the better cell voltage occurs in the case of the rectangular channel cross-section, and therefore, higher power from the FC, although its durability is much lower compared to the durability of the triangular channel. The results also showed that the rectangular channel cross-section gave higher cell voltages, and therefore, higher power (0.63 W) from the fuel cell, although its durability is much lower compared to the durability of the triangular channel. Therefore, the triangular channel gives better performance compared to other innovative channels.

A novel approach based on semi-empirical model for degradation prediction of fuel cells

This work proposes a semi-empirical model-based prognostics method which can achieve degradation prediction and estimate the remaining useful life of proton exchange membrane fuel cells (PEMFCs) under automotive profiles. Based on the polarization behavior of PEMFCs, a voltage prediction model is proposed to predict the degradation trend of PEMFCs by introducing degradation models of electrochemical surface area and equivalent resistance, respectively. In addition, a recovery factor is introduced to characterize the performance recovery of PEMFCs after shutdown and restart. When analyzing the aging parameters that affect the performance of PEMFCs, system identification is introduced to achieve the one-to-one correspondence between the aging parameters and the experimental conditions. Two experimental cases with different PEMFCs, which are loaded with different profiles, have been performed to validate the proposed voltage prediction model's accuracy. The results show that the proposed voltage prediction model can achieve accurate degradation trend prediction of PEMFCs, whether predicting the complete profile or the degradation corresponding to the maximum current.

Analysis and Optimization of Transport Losses in Hydroxide Exchange Membrane Fuel Cells

As an emerging alternative to proton exchange membrane fuel cells (PEMFCs), hydroxide exchange membrane fuel cells (HEMFCs) are more cost-effective due to PGM-free catalysts options, more affordable bipolar plate production, and other potential savings.1 However, unlike PEMFCs, the HEMFC technology is in its early phases and there is a continuous effort to improve the performance and durability through the advancement of materials and optimization of operating conditions. The polarization curve is one of the most common methods of testing a fuel cell. A typical polarization curve for a fuel cell consists of open circuit potential (crossover losses), low-current behavior (kinetics losses), moderate-current behavior (ohmic losses), and high-current behavior (transport losses). Crossover and ohmic losses are determined by electrolytes, kinetics losses depend on catalysts and transport losses involve gas diffusion and water management. In addition, a triple phase boundary comprised of an electrolyte, an electrode and a gaseous reactant is crucial for the electrochemical reactions. Thus, the optimization of all these aspects is critical for HEMFC performance improvement. Here, we focus our work on transport phenomena in a fuel cell. The materials we used are hydroxide exchange membranes (HEMs) and ionomers (HEIs) based on poly(aryl piperidinium) (PAP).2 The specific chemical structure (shown in Figure 1) endows PAP HEMs with excellent chemical stability, high conductivity and mechanical robustness, making PAP HEMs/HEIs one of the best choices for HEMFC electrolyte. Furthermore, the use of PAP HEMs/HEIs enables operating HEMFCs at 95 °C, which accelerates reaction rates and decreases heat rejection. Optimization of fuel cell operating conditions is vital for water management. Water production by hydrogen oxidation reaction (HOR) tends to cause flooding in the anode, while water consumption from oxygen reduction reaction causes cathode to dry-out. In addition, the electro-osmotic drag pulls water from the cathode to the anode (in the reverse direction of PEMFCs), thus worsening the water management problem further. In this work, observable characteristics in the polarization curve for a flooded HEMFC were found, and a model was developed to describe this issue. Then we demonstrate that balanced water management can be obtained by adjusting the anode relative humidity and back pressure. Limiting current technology is widely employed for PEMFCs to characterize the transport resistance in order to reduce mass-transport losses; however, no one has done this systematically to HEMFCs, although there is a difference between limiting current behavior of PEMFCs and HEMFCs. We have found this technique useful to screen catalysts, optimize catalyst loading and adjust ionomer loading to improve the efficiency of gas diffusion, which is very helpful when switching from oxygen to air on cathode. Our optimized HEMFC can achieve a peak power density of 2.02 W cm-2 in H2/O2 and 1.33 W cm-2 in H2/air with platinum group metal (PGM) based catalysts (shown in Figure 2). The current density at 0.663 V for cell voltage is about 1.70 A cm-2, which is suitable for hydrogen fuel cell vehicles. References B. P. Setzler, Z. Zhuang, J. A. Wittkopf, and Y. Yan, Nat Nanotechnol, 11 (12), 1020-1025 (2016).J. Wang, Y. Zhao, B. P. Setzler, S. Rojas-Carbonell, C. Ben Yehuda, A. Amel, M. Page, L. Wang, K. Hu, L. Shi, S. Gottesfeld, B. Xu, and Y. Yan, Nature Energy, (2019) doi:10.1038/s41560-019-0372-8. Figure 1

An Open-Source Multiscale Transient Model for Numerical Characterization of Proton Exchange Membrane Fuel Cells

Mathematical modeling often compliments experimental studies and helps gain insight into various physical phenomena occurring in fuel cells that is difficult to obtain otherwise because of the small size of the components and lack of visual access. Many of the existing models for proton exchange membrane fuel cells (PEMFCs) are steady-state. These models cannot be used to study the behavior of PEMFCs during the normal testing process, which exhibits several time scales: a) milliseconds for the electrochemical processes; b) up to minutes for the mass transport; and c) up to hours for the heat transfer [1]. In recent years, various time-dependent models have been developed, e.g., [2-8]. These models, however, have critical drawbacks. Some of them, for instance, were developed for high-temperature PEMFCs and either do not consider water transport in the membrane [3] or neglect electro-osmotic drag [6]. Fuel cell models also commonly use simplified reaction kinetics [2,4-8] and neglect the capacitive current arising from double layer charging and discharging [3-8]. Effective diffusion coefficients for gases in the porous layers of fuel cells are typically computed using the Bruggeman approximation [2,4-6,8], which is not generally suitable for modeling transport phenomena in fuel cells [9]. Microstructure of the catalyst layers is seldom accounted for when estimating oxygen or hydrogen concentration at the reaction sites. In [7], an agglomerate and thin-film sub-model is only implemented for the cathodic side of the cell.In this work, a transient, two-dimensional numerical model of a PEMFC is developed in the open-source framework OpenFCST [10]. The model uses multi-step reaction kinetics [11-14] and accounts for water sorption and transport in the electrolyte, including electro-osmotic drag. Capacitive current due to double layer effects is taken into account in the model in order to increase its accuracy at small time scales. Effective gas diffusion coefficients are computed from the percolation theory [15,16], and a previously developed ionomer-covered catalyst particle sub-model [17,18] is incorporated that accounts for local transport resistances in the catalyst layers. The presented model is used for numerical PEMFC characterization by two common techniques: polarization curve experiments and electrochemical impedance spectroscopy. With this model, correlations between the operating conditions, voltage scan rates, and the magnitude of the polarization curve hysteresis are built in order to help experimentalists choose appropriate testing conditions and avoid the measurement uncertainties associated with the electrolyte hydration transients. The model also enables better understanding of the effect of the cell composition (e.g., catalyst loading and electrolyte content in the catalyst layers, thickness of the membrane and the catalyst layers) and different physical phenomena (e.g., electrolyte hydration, double layer charging and discharging) on the impedance spectrum of PEMFCs.

Behavior PEM fuel cell for 4WD electric vehicle under different scenario consideration

Vehicle autonomous present a major important problem for modern commercialized four wheel drive electric vehicle (4WDEV) propulsion system. The supply of electric vehicles with batteries is limited by state of charge (SOC) and the type of batteries technologies used. To overcome problem of energy variation in several speed and road topology condition, the proton exchange membrane fuel cells (PEMFC) is presented as best solution of energy management. In this paper we focus the behavior of PEMFC for 4WDEV controlled by direct torque control based space vector modulation (SVM-DTC). The proposed controller law is very appropriate to electric traction systems. To test the performances of PEMFC, we undergo 4WDEV to several tests. Direct torque control based on space vector modulation (SVM-DTC) is proposed. The Obtained results under Matlab/Simulink present satisfactory. The DTC-SVM law increases the utility 4WDEV autonomous under several scenario considerations. Moreover, the future industrial's vehicle must take into considerations the obtained results into design steps.

Experimental study of two-phase flow in a proton exchange membrane fuel cell in short-term microgravity condition

Water management is important for improving the performance and stability of proton exchange membrane fuel cells (PEMFCs) for space applications. An in situ visual observation was conducted on the gas–liquid two-phase flow in the cathode channels of a PEMFC in short-term microgravity condition. The microgravity environment was supplied by a drop tower. A single serpentine flow channel with a depth of 2mm and a width of 2mm was applied as the cathode flow field. A membrane electrode assembly comprising of a Nafion 112 membrane sandwiched between gas diffusion layers was used. The anode and cathode were loaded with 1mgcm−2 platinum. The PEMFC shows a distinct operating behavior in microgravity because of the effect of gravity on the two-phase flow. At a high water production regime, cell performance is enhanced by 4.6% and the accumulated liquid water in the flow channel tends can be removed in microgravity conditions to alleviate flooding. At a low water production regime, cell performance deteriorates by 6.6% and liquid aggregation occurs in the flow channel because of the coalescence of dispersed water droplets in microgravity conditions, thus squeezing the flow channel. The operating behavior of PEMFC in microgravity conditions is different from that in normal gravity conditions. Further studies are needed on PEMFC operating characteristics and liquid management for space applications.

Derivation of a Fast Mathematical Model of PEM Fuel Cell With Two-Phase Water Transport

A physical model that accounts for the transportation of water in both vapor and liquid phases is useful for the design of water management scheme in a proton exchange membrane fuel cell (PEMFC) system. A 1-D, two-phase PEMFC model that offers both a very short simulation time and a realistic capture of the physical behavior of PEMFC is developed. The presence of liquid water in the cathode gas diffusion layer is modeled by using a simplified treatment of the mass balance of water. The simulation results are compared to the published experimental data and a satisfactory agreement is obtained. The proposed model is used to predict the cell performance under various operating conditions, and its capability to predict an abrupt fall in the cell voltage under flooding condition is demonstrated. The model equations developed, except for the average liquid water saturation, are analytical and require a minimal computational effort, hence reduces the overhead time in PEMFC power system simulations.

Modeling and Simulation of PEM Fuel Cell Thermal Behavior on Parallel Computers

Proton exchange membrane fuel cells (PEMFCs) have aroused great interest in recent years, in particular for transportation applications. However, fuel cell (FC) technology is not yet ready for large-scale commercial use, as it requires more understanding and intensive development, in particular in the thermal behavior area. Such understanding of the FC requires many large-scale simulations that can take unacceptably large execution time. This is especially true when using traditional models that are governed by heat equations and based on computational tools that derive approximate solutions to partial differential equations. Such multimodel systems also require synchronization that results in overhead. Instead, in this paper, a new fully integrated modeling approach that lends itself to parallelism is introduced. This approach can benefit from advances in parallel computing, and thus dramatically reduce time and enable multiple large simulations. This is called the global nodal method, which is intended to analyze and simulate the thermal behavior of PEMFCs. Parallel simulations are implemented with the message passing interface (MPI) and using the unified parallel C (UPC) language on parallel systems. It will be shown that computation time to conduct thermal behavior in large-scale simulation using MPI and UPC is significantly reduced compared to sequential simulations, and obtained data are highly precise and accurate.

A Transient Model for Fuel Cell Cathode-Water Propagation Behavior inside a Cathode after a Step Potential

Most of the voltage losses of proton exchange membrane fuel cells (PEMFC) are due to the sluggish kinetics of oxygen reduction on the cathode and the low oxygen diffusion rate inside the flooded cathode. To simulate the transient flooding in the cathode of a PEMFC, a transient model was developed. This model includes the material conservation of oxygen, vapor, water inside the gas diffusion layer (GDL) and micro-porous layer (MPL), and the electrode kinetics in the cathode catalyst layer (CL). The variation of hydrophobicity of each layer generated a wicking effect that moves water from one layer to the other. Since the GDL, MPL, and CL are made of composite materials with different hydrophilic and hydrophobic properties, a linear function of saturation was used to calculate the wetting contact angle of these composite materials. The balance among capillary force, gas/liquid pressure, and velocity of water in each layer was considered. Therefore, the dynamic behavior of PEMFC, with saturation transportation taken into account, was obtained in this study. A step change of the cell voltage was used to illustrate the transient phenomena of output current, water movement, and diffusion of oxygen and water vapor across the entire cathode.

Experimental and modeling study on water dynamic transport of the proton exchange membrane fuel cell under transient air flow and load change

Water management is important in the proton exchange membrane fuel cell (PEMFC) operations, especially for those cells based on sulfonic acid polymers due to the depending of the conductivity on water. This paper aims at illustrating the effect of the change in membrane water content on cell potential response. For this purpose, the cell potential response has been investigated experimentally and computationally under transient air flow and load change of a PEMFC. From the experimental and computational results, an undershoot behavior of cell potential as well as the great influence of the relative humidity on the magnitude of undershoot is observed. It is found that the magnitude of cell potential undershoot increases as the relative humidity decreases. By carrying out a transient simulation on the water content of the membrane, the undershoot phenomena could be well explained. It is also found from the computational prediction that the time scale for the cell potential to reach its steady state is about 20 s, in agreement with experimental results. The model prediction also suggests that the dynamic behavior of PEMFC is critically dependent on the water content in the membrane.

Investigation of gas flow characteristics in proton exchange membrane fuel cell

An investigation of electrochemical behavior of PEMFC (proton exchange membrane fuel cell) is performed by using a single-phase two-dimensional finite element analysis. Equations of current balance, mass balance, and momentum balance are implemented to simulate the behavior of PEMFC. The analysis results for the co-flow and counter-flow mode of gas flow direction are examined in detail in order to compare how the gas flow direction affects quantitatively. The characteristics of internal properties, such as gas velocity distribution, mass fraction of the reactants, fraction of water and current density distribution in PEMFC are illustrated in the electrode and GDL (gas diffusion layer). It is found that the dry reactant gases can be well internally humidified and maintain high performance in the case of the counter-flow mode without external humidification while it is not advantageous for highly humidified or saturated reactant gases. It is also found that the co-flow mode improves the current density distribution with humidified normal condition compared to the counter-flow mode.

Behavior of PEMFC in starvation

Starvation is a vivid word to describe the operation condition of a fuel cell in sub-stoichiometric reactants feeding. In starvation, a fuel cell could not present its best performance; moreover, there might also be safety issue because of cell reversal. In this paper, current density distributions of proton exchange membrane fuel cell (PEMFC) in hydrogen and air starvation were studied with a segmented single fuel cell. Experimental results show that the polarization curves of the overall cell are different for anode and cathode starvation. And the current density distribution results show that for anode starvation, current density of the starved region drops sharply to zero, while for cathode starvation, there is no zero current density region observed. Numerical simulations give similar results.

Effect of Flow Field Design and Voltage Change Range on the Dynamic Behavior of PEMFCs

Data are presented to show that the dynamic behavior of a proton exchange membrane fuel cell (PEMFC) subjected to rapid changes in the voltage depends on the type of flow field and on the voltage range of the voltage change. These data consist of the responses of the current density when the flow rates are constant and at levels that result in operation between fuel stoichiometries of 1.2 and 1.1 (see Ref. 1 and 2 for other stoichiometries). The data expand an understanding of the previously observed pseudo-second-order dynamics of the current responding to a change in voltage. The results show that the undershoot of the final steady-state current that follows the resulting overshoot was observed with a standard triple-path serpentine flow field (SFF) but not with a single-path SFF. The results also show that the dimensionless peak current and the percentage of the overshoot current depend on the starting cell voltage and on the range of the voltage change. Evidence is presented to indicate that these peak heights are limited primarily by oxygen mass transfer, even though the PEMFC is operating at close to fuel-starved conditions.