Diagnosis tools for PEMFC using humidification interruption tests

This article presents different diagnosis tools for Proton Exchange Membrane Fuel Cells based on the analysis of their dynamic evolution when the humidification of the inlet gases is interrupted. The diagnosis is aimed to know the internal state of the fuel cell with respect to the water distribution. The proposed diagnosis procedures combine the information of the time response with that extracted from Electrochemical Impedance Spectroscopy and consist in monitoring the evolution of a set of performance indicators during the humidification interruption. The article presents a study for the selection of these performance indicators, which are related to the physical phenomena inside the PEMFC, and describes the patterns that correspond to proper or improper water distribution.Postprint (published version

Experimental characterization and diagonosis tools for proton exchange membrane fuel cells

Tesis presentada por Mauricio Primucci a través del programa de doctorado "Automatización Avanzada y Robótica" y realizada en el Institut de Robòtica i Informàtica Industrial, CSIC-UPC.-- License Creative Commons.A fuel cell is a device that gives electric power directly from electrochemical reduction and oxidation reactions. PEM fuel cells present some properties that make them appropriate for portable and transport applications: high efficiency, no emissions, solid electrolyte, low operating temperatures and high power density. However, some technical problems can be improved, durability of the materials and the appropriate control of the operating conditions. One important aspect of the operating … [+]conditions is the water management. The right water content is needed in the electrolyte and catalyst layers to maximize the efficiency of the PEMFC by minimizing the voltage losses. Water content in the fuel cell is given basically by the generation of the water in the cathode due to the reaction, the humidity of the inlet gases and the transport trough the membrane. This thesis studies, proposes and compares different experimental characterisation methods aimed to provide performance indicators of the PEMFC water state. A systematic use of Electrochemical Impedance Spectroscopy technique is presented and its results are studied in order to analyse the influence of different operating conditions over the PEMFC response. The variables under analysis include: load current, pressure temperature and gas relative humidity. All these variables are considered with inlet gases feeding: H2/O2 and H2/Air. A set of relevant characteristics from the EIS response has been considered. Several equivalent circuits has been analysed and those that have the best fitting with the experimental EIS data are selected. When air is used as oxidant, a simple equivalent circuit with a resistance and a Warburg element is proposed. When Oxygen is used as oxidant, a more complex equivalent circuit is needed. A detailed sensitive analysis is performed indicating those parameters that best capture the influence of the operating conditions. A new experimental characterisation technique, based on the inlet gases humidification interruption is proposed. This dynamic technique combines the information extracted from EIS and the temporal response in order to study the water transport and storage effects in the PEMFC.Al Institut de Robòtica i Informàtica Industrial (IRII), donde he realizado la tesis doctoral, por el gran soporte tanto personal como ecónomico. También agradecer a la Agència de Gestió d’Ajuts Universitaris i Recerca (AGAUR) por la beca pre-doctoral que me han concedido para poder llevar a cabo esta tesis. También al Consejo Superior de Investigaciones Científicas (CSIC) y a la Universitat Politècnica de Catalunya (UPC) por los contratos que me permitieron seguir vinculado al IRII.Peer Reviewe

Diagnosis tools for PEMFC using humidification interruption tests

Presentado al V Congreso Nacional de Pilas de Combustible celebrado en Madrid del 21 al 23 de noviembre de 2012.This article presents different diagnosis tools for Proton Exchange Membrane Fuel Cells based on the analysis of their dynamic evolution when the humidification of the inlet gases is interrupted. The diagnosis is aimed to know the internal state of the fuel cell with respect to the water distribution. The proposed diagnosis procedures combine the information of the time response with that extracted from Electrochemical Impedance Spectroscopy and consist in monitoring the evolution of a set of performance indicators during the humidification interruption. The article presents a study for the selection of these performance indicators, which may be related to the physical phenomena inside the PEMFC, and describes the patterns that correspond to proper or improper water distribution.The authors acknowledge financial support from Spanish MICINN (DPI2010-15274 and DPI2011-25649). M.P. is grateful to the Generalitat de Catalunya (AGAUR Dept.) for the PhD Grant support.Peer Reviewe

Experimental characterization and diagonosis tools for proton exchange membrane fuel cells

A fuel cell is a device that gives electric power directly from electrochemical reduction and oxidation reactions. PEM fuel cells present some properties that make them appropriate for portable and transport applications: high efficiency, no emissions, solid electrolyte, low operating temperatures and high power density. However, some technical problems can be improved, durability of the materials and the appropriate control of the operating conditions. One important aspect of the operating conditions is the water management. The right water content is needed in the electrolyte and catalyst layers to maximize the efficiency of the PEMFC by minimizing the voltage losses. Water content in the fuel cell is given basically by the generation of the water in the cathode due to the reaction, the humidity of the inlet gases and the transport trough the membrane. This thesis studies, proposes and compares different experimental characterisation methods aimed to provide performance indicators of the PEMFC water state. A systematic use of Electrochemical Impedance Spectroscopy technique is presented and its results are studied in order to analyse the influence of different operating conditions over the PEMFC response. The variables under analysis include: load current, pressure temperature and gas relative humidity. All these variables are considered with inlet gases feeding: H2/O2 and H2/Air. A set of relevant characteristics from the EIS response has been considered. Several equivalent circuits has been analysed and those that have the best fitting with the experimental EIS data are selected. When air is used as oxidant, a simple equivalent circuit with a resistance and a Warburg element is proposed. When Oxygen is used as oxidant, a more complex equivalent circuit is needed. A detailed sensitive analysis is performed indicating those parameters that best capture the influence of the operating conditions. A new experimental characterisation technique, based on the inlet gases humidification interruption is proposed. This dynamic technique combines the information extracted from EIS and the temporal response in order to study the water transport and storage effects in the PEMFC. Two advantages of this proposed technique is the simple hardware configuration used and the relative low impact on the fuel cell response, making attractive the humidification interruption as an in-situ technique. Three different sets of performance indicators are proposed as diagnosis tool. Relevant Characteristics from the EIS response, if properly monitored, can give a diagnostic of the fuel cell internal state. After an analysis, the chosen ones are: low and high frequency resistances (RLF and RHF) and the frequency of the maximum phase. These RC are helpful to determine if the PEMFC with the current operating conditions is well humidified. If the zone defined by RLF decrease, RHF slight increase and the frequency of the maximum phase increase is minimal, the cathode is optimally humidified. Equivalent Circuit are used in order to give a physical interpretation. The selected parameters as performance indicators are: membrane resistance, Rm, time constant and resistance of diffusion process (using Warburg elements: Tw and Rw). In this case, the humidification of the fuel cell is optimum if the zone where Rw and Tw decrease and Rm has slow increase is minimal. Model Based performance indicators are proposed: Rm, effective diffusion coefficient, Deff and effective active area, Aeff. The optimal humidification occurs when the zone where Deff is stationary and Rm has not changed significantly, is minimal. The parameter Aeff involved in this last diagnosis procedure can be detached from the humidification interruption test and be used to estimate the effective active area and then is also helpful to compare the PEMFC performance in different operating conditions.Una pila de combustible es un dispositivo que da energía eléctrica a partir de reacciones electroquímicas de reducción y oxidación. Las pilas del tipo PEMFC presentan propiedades que las hacen adecuadas para aplicaciones de transporte: alta eficiencia, cero emisiones, electrolito sólido, bajas temperaturas de operación y alta densidad de potencia. Sin embargo, algunos problemas técnicos deben ser estudiados: la durabilidad de los materiales y la correcta selección de las condiciones de funcionamiento. Una de las más importantes es la gestión del agua. Un balance adecuado del agua en la pila es necesario para maximizar la eficiencia de la PEMFC reduciendo al mínimo las pérdidas de tensión. El contenido de agua en la PEMFC viene dado por su generación en el cátodo debido a la reacción, la humedad de los gases de entrada y el transporte de agua a través de la membrana. La tesis estudia, propone y compara los diferentes métodos de caracterización experimental con el objetivo de obtener indicadores del estado del agua en la PEMFC. Se realiza un uso sistemático de la técnica “espectroscopía de impedancia electroquímica (EIS)” y el análisis de la influencia de las diferentes condiciones de operación sobre la respuesta de la PEMFC. Las variables estudiadas son: corriente de carga, presión de los gases, temperatura, humedad relativa y también la alimentación de los gases de entrada: H2/O2 y H2/aire. Se presenta un conjunto de características relevantes de la respuesta del EIS y se usan para dar valores iniciales a los circuitos equivalentes. Se estudian diferentes configuraciones de circuitos equivalentes y se seleccionan aquellos que tienen la mejor conexión con los datos experimentales. Se realiza un análisis de sensibilidad de los parámetros de los circuitos equivalentes con respecto a las diferentes condiciones de operación, para encontrar aquellos que sean útiles para representar estas variaciones. Se propone una nueva técnica experimental de caracterización, basada en la interrupción de la humidificación de los gases de entrada. Esta técnica combina la información de la respuesta temporal con la frecuencial (EIS) y es útil para analizar la influencia del agua en la respuesta de la PEMFC. Algunas ventajas de esta técnica son: la fácil implementación física y el bajo impacto sobre la respuesta de la PEMFC, lo cual convierte esta técnica en candidata para ser utilizada “In-situ”. Se proponen tres conjuntos de indicadores de comportamiento de la pila como herramientas de diagnosis. En primer lugar, se presentan las “Características Relevantes” de la respuesta de la EIS que dan un diagnóstico del estado interno de la PEMFC. De entre ellas se selecciona como indicadas: las resistencias de baja y alta frecuencia (RLF y RHF) y la frecuencia del máximo de fase. Estas características sirven para determinar la correcta humidificación de la pila en las condiciones actuales de operación. El cátodo está correctamente humidificado si la respuesta de las características, muestran que la zona definida por RLF bajando, RHF subiendo ligeramente y la frecuencia de la máxima fase está subiendo, es mínima. En segundo lugar, se usan los “Circuitos Equivalentes” para dar una interpretación física a los indicadores. Los parámetros seleccionados son: la resistencia de la membrana, Rm, la resistencia y la constante de tiempo de la difusión (Rw y Tw). En este caso, la humidificación correcta del cátodo ocurre cuando la zona donde Rw y Tw bajan y Rm sube ligeramente, es mínima. Por ultimo, se proponen indicadores de comportamiento utilizando un modelo: Rm, coeficiente de difusión efectivo, Deff y el área activa efectiva, Aeff. La humidificación óptima del cátodo ocurre cuando la zona donde Deff es estable y Rm no cambia significativamente, es mínima. El parámetro Aeff es útil para estimar el área activa efectiva aun cuando no se realice una interrupción de humidificación y para comparar la respuesta de la PEMFC bajo diferentes condiciones de operacio

Test de interrupción de la humidificación para la diagnosis en pilas PEM

Presentado al III Congreso Nacional de Pilas de Combustible celebrado en Zaragoza (España) del 24 al 26 de septiembre de 2008.[EN]: One of the most demanding research topics related to the Polymer Electrolyte Membrane Fuel Cell concerns its reliability. Apart from the security aspects, it is basic to have a diagnosis of the internal state of the fuel cell 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, reactants humidity, reactants concentrations and current. This work presents the combination of the experimental characterisation technique named Electrochemical Impedance Spectroscopy and the reactant gases humidification interruption to study the behaviour of the fuel cell system. The realization of spectroscopy tests when the humidification interruption is applied, allows obtaining certain relevant characteristics, which can be used as fuel cell state diagnostic indexes.[ES]: Uno de los principales temas de investigación relacionados con las pilas de combustible del tipo de membrana de electrolito polimérico es su fiabilidad . Además de los aspectos de seguridad, es básico hacer una diagnosis del estado interno de la pila para corregir y optimizar su funcionamiento. El estado interno de la pila de combustible cambia con las condiciones de operación, dadas por: las temperaturas, la presión, la humidificación de los gases, la concentración de reactantes y la corriente. En este trabajo se presenta la combinación de una técnica de caracterización experimental, la espectroscopía de impedancia electroquímica, y la interrupción de la humidificación de los gases reactantes para determinar el estado interno de la pila. La realización de varias espectroscopias mientras se desarrolla el transitorio de interrupción de la humidificación permite obtener la evolución de ciertas características relevantes que pueden ser utilizadas en el diagnóstico del estado de la pila.Este trabajo fue parcialmente subvencionado por el proyecto CICYT DPI2007-626966 del Ministerio de Educación y el soporte de una beca predoctoral del Departament de Universitats, Investigació i societat de l’Informacio, de la Generalitat de Catalunya.Peer Reviewe

Diagnosis tools for PEMFC using humidification interruption tests

This article presents different diagnosis tools for Proton Exchange Membrane Fuel Cells based on the analysis of their dynamic evolution when the humidification of the inlet gases is interrupted. The diagnosis is aimed to know the internal state of the fuel cell with respect to the water distribution. The proposed diagnosis procedures combine the information of the time response with that extracted from Electrochemical Impedance Spectroscopy and consist in monitoring the evolution of a set of performance indicators during the humidification interruption. The article presents a study for the selection of these performance indicators, which are related to the physical phenomena inside the PEMFC, and describes the patterns that correspond to proper or improper water distribution

Test de interrupción de la humidificación para la diagnosis en pilas PEM

Uno de los principales temas de investigación relacionados con las pilas de combustible del tipo de membrana de electrolito polimérico es su fiabilidad. Además de los aspectos de seguridad, es básico hacer una diagnosis del estado interno de la pila para corregir y optimizar su funcionamiento. El estado interno de la pila de combustible cambia con las condiciones de operación, dadas por: las temperaturas, la presión, la humidificación de los gases, la concentración de reactantes y la corriente. En este trabajo se presenta la combinación de una técnica de caracterización experimental, la espectroscopía de impedancia electroquímica, y la interrupción de la humidificación de los gases reactantes para determinar el estado interno de la pila. La realización de varias espectroscopias mientras se desarrolla el transitorio de interrupción de la humidificación permite obtener la evolución de ciertas características relevantes que pueden ser utilizadas en el diagnóstico del estado de la pila.Peer Reviewe

Test de interrupción de la humidificación para la diagnosis en pilas PEM

One of the most demanding research topics related to the Polymer Electrolyte Membrane Fuel Cell concerns its reliability. Apart from the security aspects, it is basic to have a diagnosis of the internal state of the fuel cell 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, reactants humidity, reactants concentrations and current. This work presents the combination of the experimental characterisation technique named Electrochemical Impedance Spectroscopy and the reactant gases humidification interruption to study the behaviour of the fuel cell system. The realization of spectroscopy tests when the humidification interruption is applied, allows obtaining certain relevant characteristics, which can be used as fuel cell state diagnostic indexes.Peer Reviewe

Characterisation of fuel cell state using Electrochemical Impedance Spectroscopy analysis

Presentado al I Simposium Ibérico de Hidrógeno, Pilas de Combustible y Baterías Avanzadas celebrado en Bilbao (España) del 1 al 4 de julio de 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 fitting of the EIS response for all operating conditions is proposed and its evolution with operating pressure is studied.This work was supported by the project 'Avances en el modelo y diseño de controladores para sistemas basados en pila de combustible PEM' (4800). This work has been funded partially by the project CICYT DPI2007-626966 of the Spanish Government, and the support of a PhD doctoral grant of the Department of Universities, Investigation and Society Information of the Generalitat de Catalunya.Peer Reviewe

Diagnosis tools for PEMFC using humidification interruption tests

This article presents different diagnosis tools for Proton Exchange Membrane Fuel Cells based on the analysis of their dynamic evolution when the humidification of the inlet gases is interrupted. The diagnosis is aimed to know the internal state of the fuel cell with respect to the water distribution. The proposed diagnosis procedures combine the information of the time response with that extracted from Electrochemical Impedance Spectroscopy and consist in monitoring the evolution of a set of performance indicators during the humidification interruption. The article presents a study for the selection of these performance indicators, which are related to the physical phenomena inside the PEMFC, and describes the patterns that correspond to proper or improper water distribution