Fabien Harel

Fuzzy-Clustering Durability Diagnosis of Polymer Electrolyte Fuel Cells Dedicated to Transportation Applications

Polymer electrolyte fuel cells (FCs) are often considered as the most promising power-generation sources for next- generation electrical or hybrid electrical vehicles. However, areas needing further development are the improvements of the efficiency, durability, and reliability of the whole powertrain. Moreover, freeze start of the FC system is also a major issue. To reach these aims, diagnosis solutions of FC stacks and systems can speed up the development cycle of this new technology. The aim of this paper is, thus, to propose some guidelines within the framework of embedded FC system durability diagnosis.

Dynamic PEM fuel cell modeling for automotive applications

This paper presents a static and dynamic modeling of a proton exchange membrane fuel cell (PEMFC) for transportation applications. Electrochemical analysis is performed to get an equivalent circuit of the fuel cell, which can be used, in the simulation of the power generator (association of the fuel cell and its converter). Experimental polarization curves and electrochemical impedance spectroscopy (EIS) are used to identify model parameters and to validate simulation results. Finally, experimental response to a current step is compared to the proposed model.

Analysis of a Fuel Cell Durability Test Based on Design of Experiment Approach

The results of a durability test performed during 1000 h on a proton exchange or polymer electrolyte membrane (PEM) fuel cell are analyzed using some well-suited design of experiment techniques. The response surface methodology is adopted to model the performance degradation over ageing time from various load current--fuel cell voltage curves recorded at regular time-spaced intervals and for various air utilization rates. The dual response surface approach is employed to determine the most convenient operating conditions for the cells (load current and air stoichiometry rate levels), leading to a tradeoff between elevated electrical efficiency and low voltage variability versus ageing time and cell positions in the stack. In addition, some electrochemical impedance spectra are used to provide some physical interpretations and to corroborate the observations made from the static measurements. The work shows notably the benefit of using some variable stoichiometry rates through ageing time to get high-power levels and stable performances as well.

Experimental validation of a type-2 fuzzy logic controller for energy management in hybrid electrical vehicles

The aim of this paper is to present experimental validation results of an energy management system for hybrid electrical vehicles based on type-2 fuzzy logic. The energy management system (EMS) is designed by extracting knowledge from several experts using surveys. The consideration of interval type-2 fuzzy sets enables modeling the uncertainty in the answers of the experts. The validation of the EMS is performed on a real-scale heavy duty vehicle equipped with different energy sources such as batteries, fuel cell system and ultracapacitors. Experimental results are strong evidence that type-2 fuzzy logic is wide adapted for performing the energy management in hybrid electrical vehicles.

Diagnosis of a fuel cell stack using electrochemical impedance spectroscopy and Bayesian Networks

In the first part of the paper, a novel architecture of impedance spectrometer is presented. The instrument is dedicated to the characterization and diagnostic of large fuel cell stacks operated in galvanostatic mode. It allows impedance measurements on cells located in the middle of the stack, where common mode potentials are usually too high for commercial devices. In the second part of the article, probabilistic methods (Bayesian Networks) are used to provide efficient diagnostic of a proton exchange membrane fuel cell stack. Experiments are performed on a twenty cell assembly using electrochemical impedance spectroscopy and from the test results, a Bayesian Network is proposed to ensure the diagnosis of the investigated fuel cell (study of drying and flooding phenomena). A maximum rate of good classification equal to 91% has been reached.

Analysis of a Fuel Cell Durability Test Using the Response Surface Methodology

The design of experiment (DoE) technique and one of its important aspects, the response surface methodology (RSM), are employed to analyze the results of an ageing test performed during 1000 hours on a 100 W PEM fuel cell stack. The response surfaces are plotted thanks to load current - fuel cell voltage curves recorded at regular time-spaced intervals and for various air utilization rates. Some covariance based models are used to fit and adjust response surfaces to experimental data. An optimization of the fuel cell performances is done by taken into account the time, current and air stoichiometry rate factors

A New High Voltage Impedance Spectrometer for the Diagnostics of Fuel Cell Stacks

This paper presents a novel architecture of an impedance spectrometer dedicated to the characterization and diagnostic of large Fuel Cell (FC) stacks operated in galvanostatic mode. The validation tests are first performed on a single Proton Exchange Membrane Fuel Cell (PEMFC). Then, experiments are carried out on a twenty-cell PEMFC stack delivering more significant power levels. The proposed impedancemeter allows spectrum measurements on cells located in the middle of the stack, where common mode potentials are usually too high for commercial devices. Moreover, the impedances of different individual cells in the stack are acquired with a synchronous measurement reference (global stack impedance). This capability allows distinguishing any singular cell behavior or drift effect of operational parameters (e.g. stack temperature and polarization current).Copyright

Durability Test Results of a Polymer Electrolyte Membrane Fuel Cell Operated at Overnominal Temperature With Low Humidified Reactants

A three-cell polymer electrolyte membrane fuel cell stack equipped with perfluorinated ionomer membranes is tested for 1000 h in severe operating conditions. The fuel cell (FC) is fed by dry hydrogen/low humidified air and it is simultaneously operated at overnominal temperature. During the long term experiment, some polarization curves and electrochemical impedance spectra are recorded at regular time-spaced intervals for various stoichiometry rates. The objective is to characterize the degradation of FC performances with the aim to better understand the FC aging mechanisms. Some response surfaces are plotted to display and analyze the stack voltage variations as a function of aging time, static load current, and gas utilization rates. Different points of the FC impedance spectra are also considered. The evolutions of their coordinates in the Nyquist plot can be monitored versus aging time and for different gas utilization rates.

A New High Voltage Impedance Spectrometer for the Diagnostic of Fuel Cell Stacks

This paper presents a novel architecture of an impedance spectrometer dedicated to the characterization and diagnostic of large Fuel Cell (FC) stacks operated in galvanostatic mode. The validation tests are first performed on a single Proton Exchange Membrane Fuel Cell (PEMFC). Then, experiments are carried out on a twenty-cell PEMFC stack delivering more significant power levels. The proposed impedancemeter allows spectrum measurements on cells located in the middle of the stack, where common mode potentials are usually too high for commercial devices. Moreover, the impedances of different individual cells in the stack are acquired with a synchronous measurement reference (global stack impedance). This capability allows distinguishing any singular cell behavior or drift effect of operational parameters (e.g. stack temperature and polarization current).Copyright