PEMFC stack voltage singularity measurement and fault classification

The study summarized in this paper deals with non-intrusive fault diagnosis of Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack. In the proposed approach, the diagnosis operation is based on the stack voltage singularity measurement and classification. To this aim, wavelet transform-based multifractal formalism, named WTMM (Wavelet Transform Modulus Maxima), and pattern recognition methods are combined to realize the identification of the PEMFC faults. The proposed method takes advantage of the non-linearities associated with discontinuities introduced in the dynamic response data resulting from various failure modes. Indeed, the singularities signature of poor operating conditions (faults) of the PEMFC is revealed through the computing of multifractal spectra. The obtained good classification rates demonstrate that the multifractal spectrum based on WTMM is effective to extract the incipient fault features during the PEMFC operation. The proposed method leads to a promising non-intrusive and low cost diagnostic tool to achieve on-line characterizations of dynamical FC behaviors.     

An analysis of fluidic voltage statistical correlation for a diagnosis of PEM fuel cell flooding

The fault diagnosis is one of the most important topics on Proton Exchange Membrane Fuel Cell (PEMFC) stacks. Statistical methodologies for diagnosis are considered as one of the most relevant. This paper is dedicated to the diagnosis of flooding, using statistical methodology.     

A novel health indicator for PEMFC state of health estimation and remaining useful life prediction

Proton Exchange Membrane Fuel Cell (PEMFC) is a promising renewable energy, while still limited by the short life duration. To postpone the end of life, approaches of health management and prognostic (PHM) are applied into the cells. The stack voltage and impedance are often used as the health indicator (HI) for estimating state of health (SoH) and predicting remaining useful life (RUL). However, on one hand, on-line measurement of impedance is hardly realizable while downtime measure costs a lot. On the other hand, a single HI based on voltage or impedance is difficult to express the degradation of PEMFC precisely. To tackle this problem, this paper develops a fusion HI and a prognostic methodology for PEMFC SoH estimation and RUL prediction. Moreover, geodesic distance is employed to estimate SoH. Afterwards, a 2nd order Gaussian degradation model is built to complete the RUL prognostics based on unscented particle filter (UPF). In the experiment, both mahalanobis distance and geodesic distance are employed to estimate the SoH based on the presented HI. Besides, a rational model is applied to predict the RUL compared with the proposed Gaussian model. Finally, the results show the efficiency and effectiveness of the SoH estimation and RUL prediction approaches based on the proposed HI.     

The dynamic multifractality in PEMFC stack voltage signal as a tool for the aging monitoring

Fuel Cell aging monitoring and diagnosis are key-issues for scientists and industrials who intend to spread this technology. In the present work, we propose an efficient method that enables the extraction of valuable information which contains indicators on the aging of a studied PEM Fuel Cell (PEMFC). In this context, we investigate the possibilities offered by the Wavelet Leaders based Multifractal Analysis (WLMA), which is a suitable method to study the clustering variability of non-stationary fluctuating signals. A continuous aging test of 124 h conducted under nominal operating conditions serves as data input for the development of our diagnosis method. Singularity spectra (SS) are calculated on the stack voltage signals at different periods of time. We observe that stack voltage over extended periods of operating time leads to different types of singularities, i.e., we find a narrow range of values of Hölder exponent h with non-zero fractal dimension D(h) according to the operating time of the FC. We conclude that this dynamic multifractality of the stack voltage can be considered as a pertinent tool for the monitoring of the FC aging state.     

Tuning of PEM fuel cell model parameters for prediction of steady state and dynamic performance under various operating conditions

Many models are available with various degrees of complexity to study the behaviour of Proton Exchange Membrane Fuel Cells (PEMFC) under varying operating conditions. To our knowledge no model has been developed from single cells to multiple cells with increased electrode area for PEMFC stacks along with power conditioners, by considering the dynamic characteristics of the fuel cells under the influence of stoichiometry, humidity ratio and their response during their integration with power conditioners. We have developed a model using Matlab to study the transient response of the cell for 30 cm², which has been extended to a multicell stack of 1.2 kW capacity of electrode area 150 cm². The developed model has been validated using PEMFC single cells and stacks, by considering partial pressure of hydrogen, oxygen, and water as three states, anode fuel utilization and all three losses. This model is proposed to evaluate the transient response of all the stacks developed at Centre for Fuel Cell Technology (CFCT) ranging from a few watts to 10 kW that are integrated with various power conditioners depending on the applications.     

Impact of alternating fuel feeding on a PEMFC stack durability

The integration of PEMFC for transport applications requires cost as well as system complexity reduction. A novel anode circuit architecture named “Alternating Fuel Feeding” (AFF) was developed. It combines on one hand, the benefits of the hydrogen recirculation and on the other hand, the simpleness of Dead-End Anode (DEA). A previous work demonstrated the benefits on the costs and on the anodic line weight. In the present work, investigations on stack durability, from the system scale to the cell scale, are performed during operation in two anode feeding modes: AFF and recirculation. The performances of stacks are evaluated along ageing tests, coupled with local measurements. At the end of life, postmortem analyses are performed on the aged cells. The degradation rates of stack performances are quite similar in both cases while more heterogeneous cell degradation are observed in recirculation mode along with the ageing according to a Fuel Cell Dynamic Load Cycle (FC-DLC).     

Fuel cell power conditioning unit for standalone application with real time validation

In recent era, fuel cells are emerging as better alternative to wind and solar based energy sources due to its reliability and high efficiency. Polymer Electrolyte Membrane Fuel Cell (PEMFC) is widely used in various applications due to low operating temperature and high energy density. On the other side low and unregulated stack voltage demands PEMFC integration with suitable power conditioning unit. However, the use of actual fuel cell power conditioning unit in design and testing for research is expensive. Any failure may lead to damage of source or power circuit. In this regard, the present work aims at developing a soft-computing model of PEMFC. Also, a DC-DC converter is designed to step-up the stack voltage. A classical PI controller is implemented to regulate the PEMFC fed power conditioning units for resistive loads. The proposed system is implemented is Hardware-In-the-Loop (HIL) using OPAL-RT's OP5600 Real Time Digital Simulator (RTDS).     

Oxygen starvation analysis during air feeding faults in PEMFC

A new analysis of performance degradation during oxygen starvation of PEMFC (Proton Exchange Membrane Fuel Cell) is proposed in this paper. Oxygen starvation happens for several reasons like compressor delay, fault during peak power demand or water management issues. The consequences on fuel cell performance degradation are not still well understood. This paper proposes a complete study with experimental tests and modeling. Impacts on performance were investigated under oxygen starvation and effects on the local conditions in the MEA (Membrane Electrode Assembly) were measured and modeled. In particular, current density measurements during oxygen starvation have been made with a specific bi-cell stack. Voltage oscillations were also found. Durability test have been realized on a PEMFC stack. Samples from the degraded MEA were analyzed by TEM (Transmission Electron Microscopy). Degradation mechanisms are proposed and the local conditions during oxygen starvation are identified.     

Experimental and modelling studies of low temperature PEMFC performance

The performance of a PEMFC (Polymer Electrolyte Membrane Fuel Cell) is greatly influenced by the various operating variables like temperature, pressure, stoichiometry of reactants and humidity. The presented work deals with the experimental study of 30 cells low temperature PEM fuel cell stack employing Nafion®-212 membranes. Experimental results are discussed with polarization curves and compared with the steady state model results, developed in MATLAB. The model predicts increase PEMFC performance with increase in operating temperature, pressure and reactant humidity. The comparison shows good agreement between experimental and modeling results with deviations in the range of 7–15% only.     

Design of experiment techniques for fuel cell characterisation and development

Designs of Experiments (DoE) can be of immediate relevance for various research works conducted in the Fuel Cell (FC) area. DoE techniques allow efficient test definitions for rapid conceptions and well-organised characterisations of FC materials and components, individual cells, stacks or even complete generators. In the DoE method, some statistic-based models can be proposed in pre-stages of physical models. The statistical/numerical relations are used to predict the behaviour of the investigated systems as a function of various operating parameters. Some control strategies can also be developed to optimise relevant criteria like FC voltage, fuel consumption, and maximal electrical power or stack lifetime.     

Performance superiority of an arc-shaped polymer electrolyte membrane fuel cell over a straight one

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a promising electricity-producing technology but needs further improvement to become economically viable. Oxygen transfer to reaction zone is known as one of the main PEMFC performance-limiting factors. Accordingly, various recent studies have been focused on fuel cell design to improve oxygen transfer. The present study numerically investigates the influences of converting a straight (or planar) PEMFC to a bent (arc-shaped) one. The idea of PEMFC bending originates from the fact that it can create a velocity component perpendicular to gas diffusion layer (GDL) and exert centrifugal force on channel gas flow towards the GDL; thereby, enhancing oxygen transfer. The results indicate that PEMFC bending can enhance performance up to about 8.33% for the examined operating conditions. It is also observed that PEMFC bending impact factor generally increases with operating pressure, stoichiometry ratio and bending angle, but decreases with operating voltage.     

External temperature field test and leakage fault diagnosis for SOFC stacks

The uniformity of Solid Oxide Fuel Cell (SOFC) stacks largely affects the stability and performance of the SOFC power generation system with multiple stacks. However, the health conditions of the stacks are usually assessed by the long-time electrochemical performance test, and some small faults are not able to be quickly identified when the I–V performances have small differences. In this paper, a non-contact temperature sensor array constructed by thermocouples is proposed for NDE (non-destructive evaluation) application in SOFC stacks. The temperature sensor array is fixed near the outer surfaces of the 1 kW-class stack to measure the external temperature field of the stack. Based on the experimental results, it is found that the proposed method is feasible for the examination of the external temperature field of stacks under different operation conditions, which helps to screening the stacks before assembling to the system. At the same time, a real-time online monitoring of fuel leakage is performed using the temperature sensor array, and stacks with unusual temperature distribution due to the leakages can be quickly recognized by comparing with the healthy stack.     

Effect of dynamic load on the temperature profiles and cooling response time of a proton exchange membrane fuel cell

Polymer Electrolyte Membrane Fuel Cells (PEMFC) is an electrochemical device that generates electrical energy from the reactions between hydrogen and oxygen. An effective thermal management is needed to preserve the fuel cell performance and durability. Cooling by water is a conventional approach for PEMFC. Balance between optimal operating temperature, temperature uniformity and fast cooling response is a continuous issue in the thermal management of PEMFC. Various cooling strategies have been proposed for water-cooled PEMFC and an approach to obtain a fast cooling response was tested by feeding the coolant at a high temperature. In this paper, the operating behaviour was characterized from the perspectives of temperature profiles, mean temperature difference, and cooling response time. A 2.4 kW water-cooled PEMFC was used and the electrical load ranged from 40 A–90 A. The operating coolant temperature was set to 50 °C where the maximum stack operating temperature is 60 °C. The stack temperature profiles, cooling response time, mean temperature difference and cooling rates to the load variation was analysed. The analysis showed that the strategy allowed a fast cooling response especially at high current densities, but it also promotes a large temperature gradient across the stack.     

Bond graph modeling approach development for fuel cell PEMFC systems

This paper addresses the problem of bond graph methodology as a graphical approach for modeling fuel cell systems. The system consists of a Proton Exchange Membrane Fuel Cell (PEMFC) stack, an interleaved boost converter, battery pack connected via a buck converter.     

Online electrochemical impedance spectroscopy detection integrated with step-up converter for fuel cell electric vehicle

Declining reserves of the crude oil and increasingly serious environmental pollution have emphasized the requirement of a suitable substitute to our actual petroleum-based automobile market. An environmentally-friendly and efficient power generation device based on a sustainable energy source is attractive to settle this issue and realize cleaner production. Proton Exchange Membrane Fuel Cell (PEMFC), which achieves zero emission, modular construction, high energy conversion ratio and etc., has been treated as one of the most promising solution for automobile applications. Nevertheless, many technical restrictions such as relatively short life cycle have still to be conquered before satisfying the requirements of large-scale commercialization.Electrochemical Impedance Spectroscopy (EIS) is an effective technique for fault detection of electrochemical system. This paper presents an on-line EIS detection strategy based on the proposed fuel cell stack connected step-up converter. No additional equipment is required compared with conventional detection process. Furthermore, the proposed 6-phase Interleaved Boost Converter (IBC) based on Silicon Carbide (SiC) semiconductors and inverse coupled inductors has achieved low input current ripple, high efficiency, high voltage gain ratio, high compactness and high redundancy. Benefiting from these advantages, the lifespan of fuel cell stack can be extended. The proposed online EIS detection has been realized and the results have been compared with theoretical analysis.     

A review of polymer electrolyte membrane fuel cell durability test protocols

Durability is one of the major barriers to polymer electrolyte membrane fuel cells (PEMFCs) being accepted as a commercially viable product. It is therefore important to understand their degradation phenomena and analyze degradation mechanisms from the component level to the cell and stack level so that novel component materials can be developed and novel designs for cells/stacks can be achieved to mitigate insufficient fuel cell durability. It is generally impractical and costly to operate a fuel cell under its normal conditions for several thousand hours, so accelerated test methods are preferred to facilitate rapid learning about key durability issues. Based on the US Department of Energy (DOE) and US Fuel Cell Council (USFCC) accelerated test protocols, as well as degradation tests performed by researchers and published in the literature, we review degradation test protocols at both component and cell/stack levels (driving cycles), aiming to gather the available information on accelerated test methods and degradation test protocols for PEMFCs, and thereby provide practitioners with a useful toolbox to study durability issues. These protocols help prevent the prolonged test periods and high costs associated with real lifetime tests, assess the performance and durability of PEMFC components, and ensure that the generated data can be compared.     

Online identification of semi-empirical model parameters for PEMFCs

In this paper, a semi-empirical model has been proposed for online identification in order to improve the performances of Fuel Cell Vehicles (FCV). The Adaptive Recursive Least Square (ARLS) method has been considered to update the semi-empirical model parameters online to cope with Fuel Cell System (FCS) parameter variations. After introducing a literature review of the semi-empirical model for online identification to show its importance. A Matlab/Simulink model has been designed to define the initial parameters of the ARLS algorithm for the online identification in real time. Then, an experimental test bench has been performed to verify the ARLS algorithm in real time on a Proton Exchange Membrane Fuel Cell (PEMFC). In order to simplify the semi-empirical model, an extensive ANalysis Of VAriance (ANOVA) technique has been used to evaluate the impact of each model parameter. It has been confirmed that the ARLS algorithm is suitable to take into account the operating parameters that changes the PEMFC performance. The simulation using ANOVA results has shown that a parameter with relative low impact (mass transport) is very relevant for the energy management. Therefore, the proposed study can be used for the control and energy management of the Hydrogen Research Institute FCV taking into account the influence of operating conditions.     

High performance PEMFC stack with open-cathode at ambient pressure and temperature conditions

An open-air cathode proton exchange membrane fuel cell (PEMFC) was developed. This paper presents a study of the effect of several critical operating conditions on the performance of an 8-cell stack. The studied operating conditions such as cell temperature, air flow rate and hydrogen pressure and flow rate were varied in order to identify situations that could arise when the PEMFC stack is used in low-power portable PEMFC applications. The stack uses an air fan in the edge of the cathode manifolds, combining high stoichiometric oxidant supply and stack cooling purposes. In comparison with natural convection air-breathing stacks, the air dual-function approach brings higher stack performances, at the expense of having a lower use of the total stack power output. Although improving the electrochemical reactions kinetics and decreasing the polarization effects, the increase of the stack temperature lead to membrane excessive dehydration (loss of sorbed water), increasing the ohmic resistance of the stack (lower performance).     

Optimal parameter identification of PEMFC stacks using Adaptive Sparrow Search Algorithm

In this paper, a new optimization algorithm called Adaptive Sparrow Search Algorithm (ASSA) is proposed for optimal model parameters identification of the proton exchange membrane fuel cell (PEMFC) stacks. The proposed ASSA is utilized for minimizing the sum of squared error (SSE) between the empirical stack voltage and the calculated stack voltage by optimal selection of the mentioned parameters in the PEMFC stack. The method is then performed to three case studies including Ballard Mark V, Horizon H-12, and NedStack PS6 under different operating conditions and give 0.82, 5.14, and 0.097 of SEE which is the least value for all three case studies. The results of the algorithm are compared with some reported works in the literature including CGOA, GRA, and basic SSA to show the method prominence. The final results indicated that the proposed ASSA has the best efficiency toward the others.     

A review of polymer electrolyte membrane fuel cell stack testing

This paper presents an overview of polymer electrolyte membrane fuel cell (PEMFC) stack testing. Stack testing is critical for evaluating and demonstrating the viability and durability required for commercial applications. Single cell performance cannot be employed alone to fully derive the expected performance of PEMFC stacks, due to the non-uniformity in potential, temperature, and reactant and product flow distributions observed in stacks. In this paper, we provide a comprehensive review of the state-of-the art in PEMFC testing. We discuss the main topics of investigation, including single cell vs. stack-level performance, cell voltage uniformity, influence of operating conditions, durability and degradation, dynamic operation, and stack demonstrations. We also present opportunities for future work, including the need to verify the impact of stack size and cell voltage uniformity on performance, determine operating conditions for achieving a balance between electrical efficiency and flooding/dry-out, meet lifetime requirements through endurance testing, and develop a stronger understanding of degradation.