Performance Of Proton Exchange Membrane Fuel Cell Stack Research Articles

Experimental investigation of the effect of hydrogen recirculation on the performance of a proton exchange membrane fuel cell

The hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) is recommended for the hydrogen supply of PEMFC, and hydrogen ejectors are gradually being used in fuel cell vehicles due to low noise and low energy consumption. However, there is a lack of discussion about the influence of recirculation rate on the stack. Due to passive regulating mechanism of the ejectors, a miniature speed-adjustable peristaltic pump is used to simulate the hydrogen ejector in this study to investigate the effect of hydrogen recirculation on the performance of PEMFC stack. Experiments are conducted under different pump flow rates. The stack with hydrogen recirculation is proven to have better performance, but over high pump flow rate can lead to hydrogen shortage. It is interesting to find that the flow rate fluctuation of hydrogen inlet affects the stability of stack performance, and pressure drop and recovery time during purge process are proposed as effective indicators for performance analysis. Finally, pump flow rates between 60 ml/min and 105 ml/min are defined as “effective area”. Based on the analysis of effective indicators, keeping at “effective area” is further proved to improve the performance of the stack, which is also useful to design hydrogen recirculation.

Modeling and optimization of a proton exchange membrane fuel cell using particle swarm algorithm with constriction coefficient

The present study aims at estimating the values of an electrochemical model parameter of a proton exchange membrane fuel cell (PEMFC). A variant of the particle swarm optimization (PSO) algorithm is adopted. This variant introduces a constriction coefficient to better regulate the convergence of the numerical code. Parameters’ identification of the PEMFC stack model is performed by specifying a range for each. Validity of the adopted approach is confirmed by confronting simulation results with experimental data in terms of current–voltage polarization curves. It should be noted that the optimal value of the objective function is largely affected by the lower and upper values of the parameters. Comparison of present results with other optimization methods shows a noticeable improvement in PEMFC stack performance when using particle swarm optimization algorithm with constriction coefficient (PSO-χ). This confirms that this version of PSO algorithm is very suitable for the optimization and parameter estimation of PEMFC stack modeling.

Flexible 4-in-1 microsensor for in-situ diagnosis of electric motorcycle fuel cell range extender

The performance and life proton exchange membrane fuel cell (PEMFC) depend on local distribution of internal temperature, voltage, current and humidity, while its overall performance and life of PEMFC stack are directly affected different external operating conditions. However, the nonuniform distribution of temperature, voltage, current and humidity can occur anywhere in a PEMFC stack. In order to solve this problem, this study developed a real-time microscopic diagnosis technology for PEMFC stack performance. It applied the micro-electro-mechanical systems (MEMS) technology to build, a flexible 4-in-1 (temperature, voltage, current and humidity) microsensor, which can measure the four main physical properties inside the PEMFC stack, so as to determine the optimum operating conditions. The flexible 4-in-1 microsensor developed in this study was successfully applied to the interior of a motorcycle fuel cell range extender, and detected that the physical properties in different parts of the PEMFC stack, especially on temperature. The measured data could be used to determine whether a thermal stress concentration has been generated inside the PEMFC stack, thus, the operating conditions could be changed accordingly to relieve the concentration. Moreover, the data of local voltage and current could also indicate the local reaction status and the relationship between the reaction rate and temperature and humidity. The proposed technology can help manufacturers to use the collected data to adjust the production parameters, thereby accelerating fuel cell development, and extending cell performance and life.

Effects of reformate on performance of PBI/H3PO4 proton exchange membrane fuel cell stack

The present study aims to examine the effect of nitrogen and carbon monoxide concentrations as well as the working temperature and the stoichiometry number on the performance of a self-made five-cell high-temperature Proton-exchange membrane fuel cell stack (PEMFC). The concentration of hydrogen in a reformed gas can be varied, and it may contain poisonous substances such as carbon monoxide. Hence, the composition of the fuel gas could affect the performance of the PEMFC. The polarization curve and the electrochemical impedance spectrogram are utilized to examine the behaviors of PEMFC. The cell temperature of 160 °C is found as an optimal working temperature in this study for high-temperature PEMFC. Measured results show that the stoichiometry of the anode gas has a minimal effect on the PEMFC performance. A high percentage of nitrogen makes hydrogen dilute and leads to poor cell performance. When carbon dioxide exceeds 3%, the pt-catalyst was covered with the CO and the cell performance significantly decreased. Finally, a raise of the PEMFC temperature boosted the catalyst energy and improved the detachment of the carbon monoxide and eventually enhanced carbon monoxide tolerance.

Performance evaluation of commercial-size proton exchange membrane fuel cell stacks considering air flow distribution in the manifold

This study offers an efficient method for commercial-size proton exchange membrane fuel cell (PEMFC) stack performance evaluation to improve designing of fuel cell and maximize power density in PEMFC stack. The flow distribution in the manifold of the stack is critical to the energy conversion of the assembled unit cells in series due to the typical short-board effect. Most existing works studying on the flow distribution focus on small fuel cell stack and does not establish a clear relationship to performance, which are not able to thoroughly guide commercial-size PEMFC stack design and development. In the present study, an effective method combining computational fluid dynamics (CFD) model and empirical model is proposed to evaluate the performance of commercial-size stack considering air flow distribution in the manifold. Firstly, the air flow distribution in the manifold is predicted by a CFD model. A performance evaluation empirical model is developed by a series of experiments to evaluate the effects of flow maldistribution on the performance of PEMFC stack. Then, the predicted flow distribution and performance are respectively validated by a novel experimental setup. Finally, the effects of stack configuration, cell number, and current density on flow distribution and performance of PEMFC stacks are discussed. The results show that U-type configuration promotes more uniform voltage among unit cells than Z-type. The voltage unevenness of unit cells caused by flow maldistribution climbs dramatically as the cell number and current density increase. The methodology developed is beneficial to the energy management and the efficiency improvement of commercial-size PEMFC stack.

Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.

Performance and transient behavior of the kW-grade PEMFC stack with the Pt[sbnd]Ru catalyst under CO-contained diluted hydrogen

In the study, a self-made kW-class 40-cell proton exchange membrane fuel cell (PEMFC) stack, with an active area of 112.85 cm2 for each membrane electrode assembly and with the anodic PtRu catalyst, was tested under different simulated reformate gases of different CO concentrations and different hydrogen concentrations. The performances and the transient voltages of the stack and the individual cells under different CO/N2/H2 mixtures were studied. The results show that increasing the CO concentration or decreasing the H2 concentration of the CO-contained reformate gas negatively affects the performance of the PEMFC stack. Moreover, the PEMFC stack with the PtRu anodic catalyst can tolerate a CO concentration of up to 50 ppm under non-diluted H2. However, it can only tolerate 10 ppm CO under diluted H2. The CO tolerance decreases dramatically with an increase in the H2 dilution level. In addition, increasing the CO concentration in diluted H2 or decreasing the H2 concentration in CO-contained H2 accelerates the occurrence of potential oscillation. The potential oscillation is owing to the interactions of CO electro-oxidation and adsorption reactions on the catalyst. This work is also the first to report that the potential oscillation phenomenon initially occurs at the upstream cells of the stack.

Performance Improvement for Proton Exchange Membrane Fuel Cell Using Hydrogen Pressure Pulsation Approach

In a proton exchange membrane fuel cell (PEMFC), the hydrogen feed into the anode in a periodical pressure swing, so-called hydrogen pressure pulsation feed (HPPF), significantly affects the transport phenomena of hydrogen and water in the anode flow field. HPPF could adjust the distribution of the back diffusion water and the hydrogen partial pressure along the anode flow channels, improve hydrogen mass transfer in the anode flow field, and enhance the diffusion of hydrogen in the porous medium (anode diffusion layer). On the other hand, HPPF technique could mitigate the anode flooding issue caused by water back diffusion from the cathode, improve the fuel cell performance. In this work, the principle of HPPF technique was introduced and analyzed by a mathematic approach. Some of the important parameters used in HPPF technique, such as amplitude of pulsation pressure, pulsating frequency, etc., were experimentally investigated on dead-end mode PEMFC stack. The experimental results showed that the amplitude of pressure pulsation, pulsating frequency, and position applied for HPPF highly affected the performance of the PEMFC stack. It can be seen that higher the frequency and/or amplitude of pressure pulsation, the better the performance of PEMFC stack.

Novel variable structure control for the temperature of PEM fuel cell stack based on the dynamic thermal affine model

Dynamic thermal management of proton exchange membrane fuel cell stack (PEMFC) is a very important aspect, which plays an important role on electro-reaction. Its variation also has a significant influence on the performance and lifespan of PEMFC stack. The temperature of stack should be controlled efficiently, which has great impacts on the performance of PEMFC due to the thermal variation. Based on the control-oriented dynamic thermal affine model identified by optimization algorithm, a novel variable structures control (VSC) with rapid-smooth reaching law (RSRL) and rapid-convergent sliding mode (FCSM) is presented for the temperature control system of PEMFC stack. Numerical test results show that the method can control the operating temperature to reach the target value satisfactorily, which proves the effectiveness and robustness of the algorithm.

Experimental analysis of dynamic characteristics on the PEM fuel cell stack by using Taguchi approach with neural networks

This study determines the optimum operating parameters for a proton exchange membrane fuel cell (PEMFC) stack to obtain small variation and maximum electric power output using a robust parameter design (RPD). The operating parameters examined experimentally are operating temperatures, operating pressures, anode/cathode humidification temperatures, and reactant flow rates. First, the dynamic Taguchi method is used to obtain the maximum and stable power density against the different current densities, which are regarded as the systemic inputs considered a signal factor. The relationship between control factors and responses in the PEMFC stack is determined using a neural network. The discrete parameter levels in the dynamic Taguchi method can be divided into desired levels to acquire real optimum operating parameters. Based on these investigations, the PEMFC stack is operated at the current densities of 0.4–0.8 A/cm 2. Since the voltage shift is quite small (roughly 0.73–0.83 V for each single cell), the efficiency would be higher. In the range of operation, the operating pressure, the cathode humidification temperature and the interactions between operating temperature and operating pressure significantly impact PEMFC stack performance. As the operating pressure increasing, the increments of the electric power decrease, and power stability is enhanced because the variation in responses is reduced.

Particle Swarm Optimization based predictive control of Proton Exchange Membrane Fuel Cell (PEMFC)

Proton Exchange Membrane Fuel Cells (PEMFCs) are the main focus of their current development as power sources because they are capable of higher power density and faster start-up than other fuel cells. The humidification system and output performance of PEMFC stack are briefly analyzed. Predictive control of PEMFC based on Support Vector Regression Machine (SVRM) is presented and the SVRM is constructed. The processing plant is modelled on SVRM and the predictive control law is obtained by using Particle Swarm Optimization (PSO). The simulation and the results showed that the SVRM and the PSO receding optimization applied to the PEMFC predictive control yielded good performance.

Characterization of a Ballard MK5-E Proton Exchange Membrane Fuel Cell Stack

We present the results of an experimental investigation of the energy balance of a Ballard MK5-E proton exchange membrane fuel cell (PEMFC) stack. We have investigated the transient phenomena that occur during PEMFC stack warm-up, under load switching, and when the PEMFC stack is connected to a DC/AC inverter. A simple and convenient model describing the polarization curve as a function of the temperature is presented and validated by our experimental data. We also present experimental results on the increase PEMFC stack performance as a function of the current density for different oxygen concentrations of the oxidant gas.

Characterization of a Ballard MK5-E Proton Exchange Membrane Fuel Cell Stack

We present the results of an experimental investigation of the energy balance of a Ballard MK5-E proton exchange membrane fuel cell (PEMFC) stack. We have investigated the transient phenomena that occur during PEMFC stack warm-up, under load switching, and when the PEMFC stack is connected to a DC/AC inverter. A simple and convenient model describing the polarization curve as a function of the temperature is presented and validated by our experimental data. We also present experimental results on the increase PEMFC stack performance as a function of the current density for different oxygen concentrations of the oxidant gas.