Performance Of Fuel Cell Stack Research Articles

Experimental Investigation on the Backpressure Effect on the Performance of a High Temperature Proton Exchange Membrane Fuel Cell Stack

This study investigated the impact of backpressure of anode and cathode on the performance of a high-temperature proton exchange membrane fuel cell stack consisting of 30 cells, initially operating at a current density of 0.4 A/cm², temperature of 160 ℃, and 0 bar with pure H2. Subsequently, the backpressure on both sides was varied from 0 bar to 1.5 bar, and the changes in stack performance were recorded throughout the testing period. Additionally, the impact of backpressure was also investigated with reformates (H2/CO2/CO/N2 = 69.4%/22.3%/1.40%/6.9%) as anode feed for the stack. The results showed that increase in operating backpressure improves the fuel cell performance. A stack voltage increase of 20 mV per cell and 40 mV per cell were achieved for the pure hydrogen operation and reformate gas operation respectively when increasing backpressure from 0 bar to 0.5 bar. This signifies potential to improve the system’s overall efficiency with only minor penalty in terms of auxiliary power loss to increase the back pressure.

Experimental Investigation on the Backpressure Effect on the Performance of a High Temperature Proton Exchange Membrane Fuel Cell Stack

This study investigated the impact of backpressure of anode and cathode on the performance of a high-temperature proton exchange membrane fuel cell stack consisting of 30 cells, initially operating at a current density of 0.4 A/cm², temperature of 160 ℃, and 0 bar with pure H2. Subsequently, the backpressure on both sides was varied from 0 bar to 1.5 bar, and the changes in stack performance were recorded throughout the testing period. Additionally, the impact of backpressure was also investigated with reformates (H2/CO2/CO/N2 = 69.4%/22.3%/1.40%/6.9%) as anode feed for the stack. The results showed that increase in operating backpressure improves the fuel cell performance. A stack voltage increase of 20 mV per cell and 40 mV per cell were achieved for the pure hydrogen operation and reformate gas operation respectively when increasing backpressure from 0 bar to 0.5 bar. This signifies potential to improve the system’s overall efficiency with only minor penalty in terms of auxiliary power loss to increase the back pressure.

A CFD‐based manifold design methodology for large‐scale PEM fuel cell stacks

AbstractThe flow distribution issue is of significance to the fuel cell stack performance and durability, which herein is studied from a theoretical and practical level. The manifold flow fundamentals are clarified and the pressure‐reconstruction‐based principle to regulate flow distribution is revealed. The prerequisite and corequisite lie in the ratio of pressure drop between headers and the entire manifold, and the pressure recovery in the inlet header. Accordingly, a step‐by‐step manifold design methodology is proposed and further quantified by detailed and organized simulations. A desirable effect on flow uniformity is validated in large‐scale stacks consisting of 300 and 400 cells, and the values of flow uniformity index represented by coefficient of variation (CV) are 3.32% and 2.95%, respectively. Moreover, a novel wedge‐shaped layout of the intake header is proposed for further optimization. The corresponding CV values have notably declined to 1.36% and 1.29%, nearly 60% lower than the conventional rectangular counterparts.

Experimental study and modelling of an air-cooled proton exchange membrane fuel cell stack in the static and dynamic performance

Research on Proton Exchange Membrane fuel cells is an important area in the field of modern energy sources. Such fuel cells are characterized by high efficiency and fast response times, making them a promising solution for sustainable energy production. Fuel cells operate under both static and dynamic conditions. Such varying operating conditions result in achieving different efficiency of fuel cell systems. This study attempts an experimental and modeled efficiency evaluation of a 1.2 kW open-cathode air-cooled fuel cell stack under static and dynamic conditions. A Sankey energy balance and an analysis of the balance components were determined for the fuel cell stack operating in these two operating states. Simultaneous modeling of the fuel cell under both static and dynamic conditions was carried out. The efficiency values of the fuel cell stack were found to be slightly higher under static conditions than under dynamic conditions. Modeling fuel cells in static and dynamic conditions results in slightly different parameters (better conformance was obtained for static models).

Experimental study of a fuel cell stack performance operating with a power electronics converter with high-frequency current ripple

This article presents an investigation into the effect of a high-frequency current ripple on the performance of fuel cell stacks. A current with high-frequency ripple can be drained from a fuel cell stack in applications in which a power electronics converter is the stack's electrical load, and this situation is very common in a wide variety of applications. The current ripple is a variation of its value around the average or dc component. It is caused by the switching action of the transistors in a power electronics converter, it can be calculated, and converters can be designed to have a particular current ripple amplitude and frequency. The existence of a ripple increases the Root Mean Square (RMS) value of the current (compared to their dc or average value). The study employs a boost converter to regulate the power output from the fuel cell stack, effectively generating a controlled AC ripple to observe its influence. A set of experiments are conducted to analyze the impacts of these conditions from the electrical point of view. Our results reveal that the main effect of the AC ripple is a reduction of the FC stack voltage output, like the one caused for an increase on the current, the voltage drop causes a shift on the operating condition which cause a reduced-efficiency operation. The presented findings provide information and must be considered for applications of power electronics converters feed by FC stacks. Experimental results are provided to demonstrate the discussed effects.

Investigation of the Effect of Graphite Bipolar Plate Flow Channel Inhomogeneities and Faults on HT-PEM Fuel Cell Stack Performance

Bipolar plates are a key component of fuel cell stacks. Bipolar plates have multiple functions. They connect the single cells of the stack electrically and must be therefore electrically conductive. They separate oxidant and fuel gases and distribute them on each side over the membrane-electrode-assembly (MEA). Bipolar plates separate coolant liquid too. Fuel cell stack is cooled by coolant liquid which is flowing through the cooling flow channels in the middle of bipolar plates.Especially the bipolar plates for HT-PEM must endure a low pH environment, continuous electrical potential, and higher temperatures up to 200°C. The focus here is on investigations of anode and cathode side flow channels of graphite bipolar plates. Inhomogeneities and faults of flow channels are examined and their effects on fuel cell stack performance are analyzed. The analyses are based on optical scan data of flow channel geometry and measurement data of a HT-PEM fuel cell full stack consisting of 120 cells operated on a testbed under different variations. Inlet pressure and stoichiometry of both anode and cathode were varied, anode was fed with pure hydrogen and with different reformate gas compositions consisting of hydrogen, nitrogen, carbon dioxide and carbon monoxide. For each variation point, polarization curves between 0 A/cm2 – 0,55 A/cm2 in step of 0,05 A/cm2 were recorded.With an on testbed installed cell voltage monitoring (CVM) system voltages of every cell were measured and logged. Enormous amount of optical scan data consisting of width and depth information of flow channels was merged to certain statistical data for anode and cathode bipolar plates. Correlations between statistical data and cell voltages are still being investigated. It is planned to repeat the measurements with another 120 cells HT-PEM fuel cell full stack and compare the results.

Investigation of the Effect of Airborne Contaminants on PEM Fuel Cell Stack Performance and Degradation Using Electrochemical Impedance Spectroscopy, AVL Thda™ and FTIR Gas Analyzer

Air pollution is still a bitter truth in many locations in the world. In highly populated regions like metropolitan areas as well as in agricultural areas there are various airborne contaminants which can be harmful to organisms. Also fuel cells, especially PEMFC are sensitive to airborne contaminants.In most mobile and stationary PEM fuel cell systems, ambient air is used as oxidant gas at the cathode of the fuel cell. It is cost and weight saving because there is no need to install additional tank for pure oxygen and to refill it, but the performance of fuel cell can suffer beyond the oxygen gain from airborne contaminants, which also have the potential to accelerate degradation. To prevent that airborne contaminants reach the fuel cell cathode, air filter systems consisting of particle filter and additional activated carbon filter are installed at the cathode inlet.The focus here is on the investigation of the use of AVL THDAtm method to detect effects of airborne contaminants. THDA (total harmonic distortion analysis) is a patented online fuel cell monitoring method based on analyzing harmonic distortion effects of voltage drifts instead of single cell voltage measurement. So far it was successfully demonstrated for the detection of water issues like flooding and drying, and for low media supply issues on both cathode and anode side [1, 2].For the development and validation of the method, experiments with a PEMFC stack are going to be done on a fuel cell testbed equipped with an AVL X-Ion impedance analyzer. Specific air pollutant gases ammonia (NH3), sulfur dioxide (SO2) and nitrogen oxides (NOx) are going to be mixed into the cathode air in the ppb range. Their effects on PEMFC stack performance are going to be investigated with electrochemical impedance spectroscopy (EIS) and total harmonic distortion analysis. The cathode exhaust gas is also going to be analyzed by an FTIR gas analyzer.It is planned to test the PEMFC stack under different operating conditions, with various parameters and different cathode gas mix ratios while monitoring possible conversion of impurities via FTIR and the stack state of health using THDA and conventional technologies to understand the link between the effect of airborne contaminants on fuel cell stack performance, on its lifetime and to determine possible early indicators in the THDA signals.

Research on the Performance of Self-Made Open-Cathode Fuel Cell Stacks under Different Operating Conditions.

The traditional fuel cell power system requires external ventilation and humidification systems for both the anode and cathode, which not only increases the application cost but also restrict its widespread use. In order to further enhance the applicability and reduce the operating costs of fuel cell power systems, this paper investigates the open-cathode proton exchange membrane fuel cell power system. This approach not only lowers the cost but also reduces the weight of the power system, enabling its potential application in a wider range of vehicles. In this study, two versions of the open-cathode fuel cell stacks were developed and performance and stability tests were conducted under various operating conditions. Additionally, tests were carried out with different materials of carbon paper to find a balance between performance and stability. Through the research presented in this paper, the application scope of fuel cells has been expanded, providing valuable insights for their further development.

Experimental improvement of the performance of the open cathode-direct methanol fuel cell stack by magnetic field effect

Open Cathode Direct Methanol Fuel Cell (OC-DMFC) stack performance is achieved at different methanol temperatures (25, 40, 55 and 70 °C), methanol concentrations (0.5, 1, 2 and 4 M) and air flow rates (3.5, 4.8 and 6.4 m/s). Each parameter, whose performance was tested separately, was presented by making comparisons within itself. The effect of performance changes on peak power densities under relatively low electromagnetic fields (4.7, 12.4, 28 and 35 mT) was investigated by exposing the 10-cell OC-DMFC stack to a magnetic field with the help of ferritic magnets. Ferritic magnets placed on the OC-DMFC stack anode and cathode surfaces, It is designed to create an electromagnetic field. Thus, the magnetic field affected both surfaces. When the magnetic field was 35 mT, the OC-DMFC reached a power density of 17.5 mW cm−2. When the DMFC stack is exposed to the magnetic field, its performance is increased by ∼16%.

Improving long-term solid oxide fuel cell stack performance prediction accuracy using a microstructure evolution model

Solid oxide fuel cells (SOFCs) are highly efficient energy conversion devices capable of utilizing a wide range of fuels. However, a variety of degradation phenomena affects their long-term performance and durability. The purpose of this study is to explain an increase in voltage of an SOFC stack observed during a 3800 h-long period of operation. A three-dimensional phase field model using focused ion beam scanning electron microscopy data as initial input is used to simulate the evolution of an SOFC microstructure over a period of prolonged operation. For the generated time steps, microstructure parameters are obtained, and a microstructure-scale mass and charge transport model is used to predict the voltage change. The microstructure evolution model, combined with the electrochemical performance model, predicts the 0.01 V increase in terminal voltage during the 3800-long period of operation, which is consistent with the experimental results. The behavior is predicted for various phase mobility ratios, suggesting that the phenomenon is related to the specific characteristics of the particular microstructure investigated in the study. Clearing of diffusion pathways is identified as the root cause of the performance enhancement. Additionally, the results suggest non-negligible changes in the ceramic phase within the electrode.

A review on the sealing structure and materials of fuel-cell stacks

AbstractProton-exchange-membrane fuel cells (PEMFCs) have the characteristics of zero emissions, a low operating temperature and high power density, and have great potential in improving energy-utilization efficiency. However, fuel cells are still quite expensive as a result of the cost of key components, including the membranes, catalysts and bipolar plates of PEMFCs. As a result of the cost and importance of these items, most researchers have focused on improving the lifetime and performance of fuel-cell stacks in recent years. In contrast, seals, sealants and adhesives play a more mundane role in the overall performance of a fuel cell, but failure of these materials can lead to reduced system efficiency, system failure and even safety issues. Little attention has been paid to the performance and durability of these products but as other fuel-cell components improve, these seals are becoming an even more critical link in the long-term performance of fuel cells. This article highlights the importance and background of fuel-cell seals. The latest research progress on the mechanical properties and structural optimization of different sealing materials is reviewed.

Towards intelligent and integrated architecture for hydrogen fuel cell system: challenges and approaches

The hydrogen fuel cell is rapidly attracting research interest for its potential in power generation and electrified transportation. The fuel cell stack (FCS) is a complex system comprising multiple coupled subsystems, and in order to maximize the utilization of an FCS, the system-level design and control can be optimized through modeling, data-based analytics and monitoring. To this end, a systematic overview of the system architecture and control of hydrogen fuel cells is provided in this review, with focus on integration and intelligence. Firstly, the fuel cell subsystems, namely the cathode, anode and cooling loops are reviewed, where their respective control methods and impact on FCS performance are discussed. DC/DC converters are another core component of FCS, and we present an overview of fuel cell DC/DC converter topologies and integrated control of DC/DC converter and air compressor. Finally, the system-level integration of fuel cells in power systems is surveyed. In the conclusions, we discuss the challenges and perspectives concerning the integrated architecture and intelligent control for FCS, including cohesive dynamic models, data-based approaches, and integrated hardware architecture.

Investigate the effect of a parallel-cylindrical flow field on the solid oxide fuel cell stack performance by 3D multiphysics simulating

In this paper, the 3D electrochemical-multiphysics coupling models for the one-cell solid oxide fuel cell (SOFC) stacks with the parallel flow field and a new parallel-cylindrical flow field have been developed and verified to evaluate their working characteristics. Firstly, the 3D model is established based on the realistic component structures including the solid, fluid, and porous components. Secondly, the momentum, mass, species, and energy transports, and the electrochemical reactions are coupled to the corresponding regions for carefully considering their effects on the performance. The analyzing result shows that a typical SOFC using the parallel-cylindrical rib configuration is concluded to be proper designing in achieving a good stack performance. The SOFC stack adopting the new parallel-cylindrical flow field would increase the electric current density by 38 % and improve the reactant distribution uniformity by 60 % than that with the traditional parallel flow field.

Thermoeconomic comparison of a molten carbonate fuel cell and a solid oxide fuel cell system coupled with a micro gas turbine as hybrid plants

This study presents a comparative evaluation of Molten Carbonate Fuel Cell (MCFC) and Solid Oxide Fuel cell (SOFC) stacks coupled with a micro gas turbine (MGT). For the analysis, it is assumed that the fuel supply to the stacks is constant in all the analyzed conditions. The components of the system have been sized using the first law of thermodynamics to meet the thermal conditions required to maintain fuel cell stack operation, while an exergetic analysis has been implemented in order to assess the components in terms of irreversibilities. Furthermore, an economic analysis to estimate the Levelized Cost of Electricity (LCOE) has been carried out to indicate the most feasible option between the two analyzed systems. The capacity of the fuel cell stacks is 500kWdc operating at 350 kPa and 600 °C/650 °C. The results indicate that MCFC stacks are more efficient than SOFC stacks, but are considerably more expensive. Nevertheless, the SOFC/MGT system has a global efficiency higher than that of the MCFC/MGT; also its Total Capital Investment (TCI) is 2.5–3.5 times lower, thus making the SOFC/MGT coupling more attractive. The only product considered coming out from the systems to determine the LCOE is electricity. The LCOE for the SOFC/MGT system is 0.339–0.402$/kWh and for the MCFC/MGT is 0.875–0.897$/kWh, which for both configurations is still higher than the current electricity prices. One aspect that increases the investment and consequently the LCOE is the high cost of the stacks and their replacements which is around 19 % and 10 % of the total Purchased Equipment Cost (PEC) for MCFC and SOFC stacks, respectively.

Multi-impedance Distribution of Relaxation Times Applied to Predicting Fuel Cell Stack Operating State: A Theoretical and Experimental Study

Multi-impedance Distribution of Relaxation Times Applied to Predicting Fuel Cell Stack Operating State: A Theoretical and Experimental Study

Optimum Sizing and Performance of Fuel Cell Stack Integrated by Boosted DC-DC converter for Running DC Load

A fuel cell stack (FCS) converts the chemical energy to be the electrical energy through an electrochemical process. One type of FCS is proton exchange membrane (PEM) with hydrogen and oxygen as the main chemical energy source. The PEMFCS has been applied widely for operating direct current (DC) loads. However, the optimum sizing of FCS, DC load and the other supported devices are not considered well, thus the system performance does not have function optimum fully. This paper present the FCS integrated by boosted DC-DC converter for running DC load. The optimum sizing of FCS and boosted DC-DC converter are explained to obtain the required number of FCS and boosted DC-DC converter. A simulation of the FCS integrated boosted DC-DC converter is conducted using SIMULINK MATLAB. The simulation results show that the FCS and boosted DC-DC converter have good performance in the operation of DC load.

Analytical methods for the effect of anode nitrogen concentration on performance and voltage consistency of proton exchange membrane fuel cell stack

Buckets effect remains one of the most important factors limiting the fuel cell stack performance and lifetime. An experiment on a 16-cell stack with decreasing hydrogen concentration is conducted to investigate the effect of anode nitrogen concentration on stack performance and voltage consistency. The mean voltage decay rate of the stack is only 6% at the current density of 1.0 A cm−2, but the decay rate of the single cell with minimum voltage reaches up to 18%. The voltage standard deviation of the fuel cell stack increases by about 8 mV with the decrease in hydrogen concentration from 100% to 85%. Results show that the local voltage standard deviation is as high as 30 mV at 85% hydrogen concentration when the 16 cells are divided into four groups. The influence of local voltage consistency on the overall voltage consistency is further studied. The local voltage consistency can be served as a reliable indicator of anode purge strategy. Moreover, the uneven gas distribution amongst the cells in the stack can be analyzed and effectively detected, according to the local voltage consistency analysis with the experiment of anode nitrogen doping.

A Feasibility Study of Placing a Heated Turbulence Grid in Front of an Air-Cooled Fuel Cell Stack in Freezing Conditions

The telecommunications industry is growing fast, and the air-cooled fuel cell is a promising alternative to the diesel-gensets as a backup power system. These systems are required to operate in freezing conditions where temperatures can be as low as -40°C, and they are usually located in remote areas where they can not be easily accessed. Berning proposed the placement of a turbulence grid in front of an air-cooled fuel cell stack to improve the heat transfer and thereby the performance, since the performance of the fuel cells was restricted due to the membrane overheating[1]. In an experimental study, Al Shakhshir et al. measured a performance increase of over 30% by placing a turbulence grid before an air-coiled fuel cell stack [2]. Then, Berning and Knudsen studied how the performance of the fuel cell would be affected while operating in different climate regions [3]. Additionally, previous studies allocated a turbulence inducing grid in front of the cathode inlet of the fuel cell where the main goal was to improve the heat transfer between the air and the components to achieve higher performances of the fuel cell while keeping the operating temperature in a good range [4] and how the design of this turbulence inducing grid would affect the cell [5]. Besides the use of a turbulence grid, this paper aims to analyze how the effect of the freezing ambient temperature can be reduced by pre-heating the incoming fuel cell air. A feasibility study is developed where different temperature differences and four different grid designs where the number of grid pores and its thickness are varied. The aims of this project were to identify feasible surface temperatures of the grid while having a reasonable consumption of fuel cell power to be provided to the grid and heated it up. A three-dimensional, steady state numerical analysis has been conducted on these grid dimensions where the computational domain considered was a single cathode channel where the gas diffusion layer would be the bottom surface, and the bipolar plate is to remain walls. Four different grid dimensions, namely grids with one and two millimeters of thickness and six 1 mm2 pores and grids with one and two millimeters of thickness and twenty-four 0.17 mm2 pores, have been considered. The outside temperature has been varied from -20 °C to 0 °C and heated up to 5 °C before air flow enters the cathode. The goal of this study is to better understand the temperature of the turbulence grid that is required to pre-heat the incoming air and thus conclude, which materials are suited. A parametric study was conducted, and with the last designed grid the best result was achieved. Preheating the air by 10°C, a surface temperature around 236°C was predicted. The fuel cell power usage would be approximately 30% of the total provided by fuel cell. It is possible to conclude the surface area of a single grid is not sufficient, leading to too high temperatures. A possibility could be having two staggered grids. Finally, an energy storage system could be used to provide this additional power required, avoiding such consumption of hydrogen and its slow dynamic response. [1] Berning T. A Numerical Investigation of Heat and Mass Transfer in Air-Cooled Proton Exchange Membrane Fuel Cells. InFluids Engineering Division Summer Meeting 2019 Jul 28 (Vol. 59032, p. V002T02A030). American Society of Mechanical Engineers.[2] Shakhshir SA, Gao X, Berning T. An experimental study of the effect of a turbulence grid on the stack performance of an air-cooled proton exchange membrane fuel cell. Journal of Electrochemical Energy Conversion and Storage. 2020 Feb 1;17(1):011006.[3] Berning T, Knudsen Kær S. A thermodynamic analysis of an air-cooled proton exchange membrane fuel cell operated in different climate regions. Energies. 2020 Jan;13(10):2611.[4] Lind A, Yin C, Berning T. A Computational Fluid Dynamics Analysis of Heat Transfer in an Air-Cooled Proton Exchange Membrane Fuel Cell with Transient Boundary Conditions. ECS Transactions. 2020 Sep 8;98(9):255.[5] Pløger LJ, Fallah R, Al Shakhshir S, Berning T, Gao X. Improving the Performance of an Air-Cooled Fuel Cell Stack by a Turbulence Inducing Grid. ECS Transactions. 2018 Jul 23;86(13):77. Figure 1

Proton membrane fuel cell stack performance prediction through deep learning method

Proton exchange membrane fuel cell (PEMFC) system is a complex non-linear system affected by many factors with interaction, which make it difficult to build an accurate mathematical model to predict the fuel cell performance. A fuel cell performance model using a Lattice gate recurrent unit (LGRU) based on recurrent neuron network (RNN) is proposed in this paper. The proposed LGRU method can remember the previous information both in time and in depth, which help to accurately predict the performance of the fuel cell stack while reducing the computation burden. Simulation and experiment are implemented on a 2.5 kW fuel cell stack. The Root mean square error (RMSE) and of voltage prediction can reach 0.0038 and the RMSE of the temperature prediction can reach 0.0040 The fuel cell stack model established using LGRU method can be efficiently used in energy management strategy designing for accurately predicting the fuel cell stack performance.

Detection and Analysis of Corrosion and Contact Resistance Faults of TiN and CrN Coatings on 410 Stainless Steel as Bipolar Plates in PEM Fuel Cells.

Bipolar Plates (BPPs) are the most crucial component of the Polymer Electrolyte Membrane (PEM) fuel cell system. To improve fuel cell stack performance and lifetime, corrosion resistance and Interfacial Contact Resistance (ICR) enhancement are two essential factors for metallic BPPs. One of the most effective methods to achieve this purpose is adding a thin solid film of conductive coating on the surfaces of these plates. In the present study, 410 Stainless Steel (SS) was selected as a metallic bipolar plate. The coating process was performed using titanium nitride and chromium nitride by the Cathodic Arc Evaporation (CAE) method. The main focus of this study was to select the best coating among CrN and TiN on the proposed alloy as a substrate of PEM fuel cells through the comparison technique with simultaneous consideration of corrosion resistance and ICR value. After verifying the TiN and CrN coating compound, the electrochemical assessment was conducted by the potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. The results of PDP show that all coated samples have an increase in the polarization resistance () values (ranging from 410.2 to 690.6 ) compared to substrate 410 SS (230.1). Corrosion rate values for bare 410 SS, CrN, and TiN coatings were measured as 0.096, 0.032, and 0.060 , respectively. Facilities for X-ray Diffraction (XRD), Scanning Electron Microscope (FE-SEM, TeScan-Mira III model and made in the Czech Republic), and Energy Dispersive X-ray Spectroscopy (EDXS) were utilized to perform phase, corrosion behavior, and microstructure analysis. Furthermore, ICR tests were performed on both coated and uncoated specimens. However, the ICR of the coated samples increased slightly compared to uncoated samples. Finally, according to corrosion performance results and ICR values, it can be concluded that the CrN layer is a suitable choice for deposition on 410 SS with the aim of being used in a BPP fuel cell system.