Diagnosis of performance degradation phenomena in PEM fuel cells (original) (raw)
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Diagnosis of PEM fuel cells through current interruption
Journal of Power Sources, 2007
Electrochemical Impedance Spectroscopy (EIS) is widely used for the characterization of PEM fuel cells. In particular, EIS data is used for parameter estimation of the PEMFC equivalent circuit model. However, EIS exhibits some practical limitations when it is applied to the in-field diagnosis and control of fuel cells (e.g., the equipment's size, weight and cost). An alternative methodology for the parameter estimation of the PEMFC equivalent circuit is proposed. Firstly, the cell's transient response after current interruption is experimentally measured. The equipment required to perform this experiment is easily portable and inexpensive. Secondly, the cell equivalent circuit parameters are estimated by fitting the cell's experimental data to the analytical expression of the cell model transient response after current interruption. The application of this cell assessment methodology is illustrated by means of a case study: the diagnosis of the cathode flooding in a PEM fuel cell.
Rapid Fault Diagnosis of PEM Fuel Cells through Optimal Electrochemical Impedance Spectroscopy Tests
Energies, 2020
The present paper is focused on proposing and implementing a methodology for robust and rapid diagnosis of PEM fuel cells’ faults using Electrochemical Impedance Spectroscopy (EIS). Accordingly, EIS tests have been first conducted on four identical fresh PEM fuel cells along with an aged PEMFC at different current density levels and operating conditions. A label, which represents the presence of a type of fault (flooding or dehydration) or the regular operation, is then assigned to each test based on the expert knowledge employing the cell’s spectrum on the Nyquist plot. Since the time required to generate the spectrum should be minimized and considering the notable difference in the time needed for carrying out EIS tests at different frequency ranges, the frequencies have been categorized into four clusters (based on the corresponding order of magnitude: >1 kHz, >100 Hz, >10 Hz, >1 Hz). Next, for each frequency cluster and each specific current density, while utilizing ...
Model based PEM fuel cell state-of-health monitoring via ac impedance measurements
Journal of Power Sources, 2006
The present paper deals with monitoring of flooding and drying out of a proton exchange membrane (PEM) fuel cell using a model-based approach coupled with ac impedance measurements. A study of the impedance response of a 150 cm 2 six-cell air/H 2 PEM fuel cell as a function of inlet gas relative humidity was carried out. Parameters of a Randles-like equivalent circuit were then fitted to the data. In order to improve the quality of the fit, the classical Randles cell was extended by changing the standard plane capacitor into a constant phase element (CPE). It was found that monitoring the evolution of the three resistances of this modified Randles model was an efficient and robust way of monitoring the state-of-health (SOH) of the fuel cell with respect to the water content of the membrane electrode assembly. Moreover, the non-integer power of the CPE was found to be statistically constant over a wide range of operating conditions, thus comforting the assumption that it has a physical meaning. Qualitative interpretation of the variation of the parameters as a function of the SOH is proposed in both flooded and dry conditions.
Characterisation of fuel cell state using Electrochemical Impedance Spectroscopy analysis
2008
One of the most demanding research topics related to the Polymer Electrolyte Membrane Fuel Cell (PEMFC) concerns its reliability. Apart from the security aspects, it is basic to have a diagnosis of the internal state of the PEMFC in order to correct and optimise its operation. The Fuel cell state and response depends on the imposed operating conditions, which are mainly given by temperatures, pressures, humidity, reactants concentrations and current. This work explores the use of fuel cell experimental Electrochemical Impedance Spectroscopy (EIS) as a tool to characterise the fuel cell state, what can be very helpful for diagnosis purposes. With this objective in mind, a definition of “relevant characteristics” extracted from EIS response is done. These “relevant characteristics” can be used in order to characterize the fuel cell and also to find the parameters of simple equivalent circuits of its dynamical response. Besides, a complete equivalent circuit which permits a close fitti...
International Journal of Hydrogen Energy, 2019
Prognostics and health management for fuel cells in real-world applications are important for optimization of lifetime and operation. A parameter that has been shown to indicate the state of ageing is the low-frequency intercept with the real axis of the Nyquist diagram in a fuel cell's impedance spectrum. This article presents a method for direct identification of this parameter, without the need to carry out a full electrochemical impedance spectroscopy, and with an algorithm that can be realized within a typical fuel-cell control system. The proposed method is based on relay excitation feedback, a proven solution from controller tuning.
Fuel Cell Diagnostics using Electrochemical Impedance Spectroscopy
2015
When a proton exchange membrane (PEM) fuel cell runs short of hydrogen, it suffers from a reverse potential fault. This fault, driven by neighboring cells, can lead to anode catalyst degradation and, through cell reversal, to holes in the membrane due to local heat generation. As a result, hydrogen leaks through the electrically-shorted membraneelectrode assembly (MEA) without being reacted, and it recombines directly with air. This recombination results in a reduction in oxygen concentration on the cathode side of the MEA and a fuel cell voltage reduction. Such voltage reduction can be detected by using electrochemical impedance spectroscopy (EIS). In this research, in order to fully understand the effect of this oxygen reduction fault, the impedances of single and multi-cell stacks at different leak rates were measured. Then the impedance signatures were compared with the signatures of stacks having non-leaky cells at different oxygen concentrations with the same current densities. The signatures were analyzed by fitting the leaky stacks and oxygen concentrations impedance data sets with the parameters of a Randles circuit. The correlation between the parameters of the two data sets allows us to understand the change in impedance signatures with respect to a reduction of oxygen in the cathode side. Using the circuit parameters, a model that establishes a relationship between impedance and voltage was also considered. With the help of this model along with the impedance signatures, we are able to detect the reduction of oxygen concentrations at the cathode by using fuzzy logic (FL). However, resolution of detection was reduced with the reduction of leak rate and/or increases in the stack cell-count. The amount of hydrogen leak rates were quantified by simulating the resulting reduced amount of oxygen with the use of neural network (NN) method. Successful implementation of FL and NN methods in a fuel cell system can result in an on-board diagnostics system that can be used to detect and possibly prevent cell reversal failures, and to permit understanding the status of crossover or transfer leaks versus time in operation. Using such system will increase the reliability and performance of fuel cell stacks, where leaks can be detected online and appropriate mitigation criteria can be applied.
Detection of Flooding and Drying inside a PEM Fuel Cell Stack
Strojniški vestnik – Journal of Mechanical Engineering, 2013
Proton Exchange Membrane (PEM) fuel cells are currently seen as the most suitable choice for implementation into daily-use applications. However, the PEM technology does not yet fulfil all the necessary requirements that the mass-market demands and proper strides towards elimination of remaining issues have to be taken. Hence, in this paper, the focus is made on water management faults, i.e. flooding and drying. More precisely, it deals with detection of them with the use of Electrochemical Impedance Spectroscopy (EIS). The EIS was successfully applied as a diagnostic tool to a fuel cell stack consisted of 80 cells without usage of any special purpose measurement equipment, where, in addition to the stack current, only voltage of the complete stack was measured. The paper describes the modifications that were made on the EIS to make it capable of handling the diagnostics of fuel cell stacks. The results of the experimental study show that the approach is successful in detecting the flooding and drying faults and that for detection only excitation signals with frequencies between 30 and 300 Hz are required. Based on the experimental data and conclusions, a diagnostic decision algorithm is proposed.
Sustainable Energy Technologies and Assessments, 2019
The objective of this work is to define and implement a method of artificial neural network to create an optimal impedance model of the proton exchange membrane fuel cell (PEMFC) which considers the electrochemistry and the mass transfer theory, which are used to analyze and diagnose PEM fuel cell failure modes (flooding & drying) across the physical parameters of the electrochemical impedance model. For this, we have based on the neural network technique for the calculation and estimation of various constituents parameters of this model. The Multi-Layer-Perceptron through back-propagation training algorithms shows satisfactory performance with the regard of parameter prediction. Furthermore, the neural network method applied to the impedance model is valid and valuable, which used to estimate the physical parameters of the electrochemical impedance model of the fuel cell (PEMFC) in both cases; flooding and drying of the fuel cell heart. The novelty of our work is summed up in the demonstration of the existence in a simple and uncomplicated way that allows the knowledge of the state of health of the PEMFC.
Fuel Starvation: Irreversible Degradation Mechanisms in PEM Fuel Cells
PEM fuel cell operates under very aggressive conditions in both anode and cathode. Failure modes and mechanism in PEM fuel cells include those related to thermal, chemical or mechanical issues that may constrain stability, power and lifetime. In this work, the case of fuel starvation is examined. The anode potential may rise to levels compatible with the oxidization of water. If water is not available, oxidation of the carbon support will accelerate catalyst sintering. Diagnostics methods used for in-situ and ex-situ analysis of PEM fuel cells are selected in order to better categorize irreversible changes of the cell. Electrochemical Impedance Spectroscopy (EIS) is found instrumental in the identification of fuel cell flooding conditions and membrane dehydration associated to mass transport limitations / reactant starvation and protonic conductivity decrease, respectively. Furthermore, it indicates that water electrolysis might happen at the anode. Cross sections of the membrane ca...
Non-dimensional analysis of PEM fuel cell phenomena by means of AC impedance measurements
Journal of Power Sources, 2011
a b s t r a c t AC impedance or electrochemical impedance spectroscopy (EIS) is becoming a fundamental technique used by researchers and scientists in proton exchange membrane (PEM) fuel cell analysis and development. In this work, in situ impedance measurements are presented for a series of operating conditions in a 50 cm 2 fuel cell. The electrode charge transfer resistance was determined from the corresponding arcs of the Nyquist diagrams. The analyses were performed for H 2 /O 2 and H 2 /air operation at different stoichiometric factors and reactant gases humidification. Characteristic time scales of charge transfer processes at the different operating conditions were estimated from the corresponding Bode plots. These values were used for a non-dimensional analysis of the different fuel cell electrochemical and transport processes, namely electrochemical reaction versus GDL reactant transport. Fuel cell adapted Damkhöler numbers are thus presented, where the results indicate that the GDL diffusion transport is the limiting process for the cases under analysis, especially when air is used as oxidant. Additional analysis of channel convective mass transport versus GDL diffusive mass transport is also presented.